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Food Processing and Engineering

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The term "fresh" can only be used to describe foods that have not been ___.
Frozen, heat processed, or preserved (for instance, cured)
For a chemical equation such as H+ + OH- = H20 at equilibrium at 25?C, which of the following is always true? (a) S = 0 (b) H = 0 (c) G = 0 (d) all of above
(c) G = 0
With regard to can defects during thermal processing, what is buckling?
Permanent deformation of the can ends caused by excessive internal can pressure compared to external pressure during cooling; opposite of paneling.
How does the process of freeze drying preserve food?
Lowered water activity, vacuum application
What off flavor of milk develops as a result of the release of hydrogen sulfide?
Cooked flavor
What organic solvent is used to extract oil from oil seeds?
Hexane
What is a process where an electric current is passed through the food with the main purpose of heating it?
Ohmic heating
In measuring the flow rate or velocity, which of the following can be used? (a) pitot tube (b) orifice meter (c) venturi tube (d) A and B (e) A, B and C
(e) A, B and C
What is co-current operation?
Rapid initial drying, inefficient heat transfer at end of drying, formation of internal splits of porosity
What is the principle of UHT?
for given increase in temperature, rate of destruction of microorganisms and many enzymes increase faster than rate of destruction for nutrient and sensory components
Define heat capacity.
The amount of heat required to change an object's temperature by a given amount (°C, K, or °F).
What is the high-quality life (HQL) of frozen foods?
High-quality life (HQL): defined as the duration of frozen-food storage until a statistically significant change in product quality can be detected when comparing the product to a reference temperature at a significantly lower temperature.
What is the purpose of the "hot break process" in tomato processing?
Inactivate pectin degrading enzymes
For a mixture of gases in a container, the total pressure exerted is the sum of the pressures that each gas would exert if it were alone. Which law is it? (a) Boyles' (b) Charles' (c) Dalton's (d) Avogadro's
(c) Dalton's
What are the other food applications for R.O. and U.F.?
Most commercial application is in the dairy industry where it is used to concentrate milk prior to manufacture of dairy products. Other uses include: - The concentration of sucrose and tomato paste. - Separation and concentration of enzymes and other proteins or pectin. - Treatment of water. - Pre-treatment prior to R.O.
What are some of the disadvantages of thermal processing?
Nutrient loss, reduce desirable qualities such as texture, flavor, color, lower antioxidant and phenolic content
What process commercially sterilizes a food product and its container separately and then combines and seals the two under a sterilized atmosphere?
Aseptic Packaging
What is the function of the Forced-circulation Evaporator?
Use of external pumping for viscous liquid with particulate: example: tomato products.
Is pasteurization a high energy thermal processing method?
No
Name four types of mixers.
1) Conical blender 2) Ribbon blender 3) Propeller 4) Turbine 5) Paddle agitators.
beta-d-galactosidase is added to dairy products for what three reasons?
Hydrolyzes lactose to galactose and glucose- latter combination is sweeter than lactose; prevents sandiness defect in ice cream; makes products consumable for lactose intolerant individuals
The heat transfer rate for radiative heating depends on temperature to the power of what?
Four
Why does a hold tube have an upward slope?
To eliminate air pockets and ensure self draining
True or False: Canned foods are sterile.
False, they are commercially sterile
Name 3 applications for radio frequency in food processing.
Baking, drying, defrosting, pasteurization/sterilization, kill pests still in walnut shells
What are the different types of food materials?
Types of food materials: liquid solutions and gels,(milk, juice, gelatin), capillary-porous ridged cells, (wet sand, wheat, corn), capillary porous colloidal materials (plant tissue, meat). Hygroscopic foods are those in which the partial pressure of water vapor varies with the moisture content
Explain the difference between conduction- and convection-heated canned foods.
Conduction: Heat moves through solid or semi-solid foods (e.g., mashed potatoes). Convection: Heat transfers through liquid foods that circulate (e.g., soups).
What are the advantages and disadvantages of spiral membrane modules?
Advantages: Compact, Minimum energy consumption, Low capital/opening cost Disadvantages: Not suitable for very viscous fluid, Dead space, Difficult to clean, Faulty membranes - change whole module
Why is agitation used in steaming processing?
May be difficult to hear solid and highly viscous foods, cook time longer at thermal center could cause over cooking therefore to increase hear transfer - containers agitated, thinner containers used
What is microencapsulation?
a process in which tiny particles or droplets are surrounded by a coating to give small capsules.
What is the range of BCU used in baking applications?
The BCU range will be from 0.00 (darkest) – 5.25 (lightest) BCU.
Give 2 ways to block production or reception of ethylene post harvest.
There are several anti-ethylene chemicals. Silver thiosulfate (STS) is used on flowers. Aminoethoxyvinylglycine (AVG, trade name ReTain) blocks ethylene synthesis. It is applied preharvest. The fruit (plant) will not produce much ethylene, so there is not an ethylene response. The ethylene blocker 1-methylcyclopropene (1-MCP, trade name EthylBloc) blocks ethylene by binding to its receptor. It is applied postharvest. The fruit (plant) may still produce some ethylene, but there is no response to the ethylene.
What are the prefixes for 10^9, 10^12, 10^15, and 10^18?
Giga (10^9), Tera (10^12), Peta (10^15), Exa (10^18)
Give two examples of an emulsifier.
Lecithins, Mono and diglycerides, Monoglyceride derivatives, fatty acid derivatives. Examples include: Soy lecithin, Tween, Potassium stearate
What is the name used to describe the temperature at which air reaches 100% saturation with water?
Dew point
In soy sauce production, what is "koji"?
Rice fermented with Aspergillus oryzae
What is the % of fat in cream that is used to make butter?
36-44% fat
How many main effects are there in a three way ANOVA?
3
According to the U.S. government, food irradiation is regulated as which of the following? (a) a process; (b) an additive; (c) a unit operation; (d) a genetically modified ingredient
(b) an additive
What are 2 internal conditions that affect drying?
Properties of the food, thermoconductivity, density, porosity, sorption isotherms
What is accomplished by passing steaks or boneless sub-primals through a bank of needles or through a steak macerator?
Mechanical Tenderization
Fourier's law is the fundamental differential equation for heat transfer by conduction. For the steady flow of heat, this equation reads q= KA(delta)T. What does K stand for in this equation?
Thermal conductivity (of the material through which the heat is flowing)
Which food processes is acetaldehyde found in?
Foods that involve yeast fermentation, it is a metabolic byproduct from the yeast.
Explain the difference between conduction, convection, and radiation in heat transfer during food processing, and give an example of each.
Conduction: Heat transfer through direct contact (e.g., frying). Convection: Heat transfer through fluid movement (e.g., boiling). Radiation: Heat transfer through electromagnetic waves (e.g., broiling).
What do the initials A.S.T.M. stand for?
American Society for Testing and Materials
What law describes moisture migration based on vapor pressure differences?
Fick’s law of diffusion
Name the three methods of producing a vacuum in cans.
Mechanical, thermal, or live steam injection
What is pectin utilized for in food chemistry/food processing?
Stability of jams, jellies, fruit juices, tomato sauces, etc.
Name the microorganism responsible for tequila fermentation.
zymomonas mobilis
What is the equation used to convert deg C to deg F?
F= (C*9/5) + 32
How do you calculate the Total System Head?
Total discharge head-total suction head
What are the advantages and disadvantages of hollow fiber membrane modules?
Advantages: Low hold up volume, Back flushing possible, Low energy consumption Disadvantages: Susceptible to end-face fouling, Not suitable for viscous fluids, Single fiber damage - replace entire module
Discuss the changes in kinetics and how they relate to drying.
Used to quantify changes. Zero order: overall quality of frozen foods, nonenzymatic browning, chlorophyll loss. First order: ascorbic acid degradation, thiosulphinate loss, oxidative color loss, microbial destruction, enzyme inactivation, texture loss in heating processing
What is the primary function for thermal processing of low acid canned foods?
To inactivate Clostridium botulinum
What is the term for determining the magnitude of reflection, refraction, and transmission of microwave radiation?
Fresnel equations
What is the equation for conduction and how can you reduce evaporation time?
Q = hA[ΔT/L) where Q equals the heat rate, h is thermal conductivity, L is thickness of wall, A is surface area of the wall, ΔT is the difference in temperature between two sides. When you increase the area you increase A and reduce evaporation time, also when you increase the temperature difference you increase Q and reduce evaporation time. You can also decrease pressure (vacuum evaporation), which decreases the boiling point of the liquid, thereby increasing the effective Delta T without needing higher steam temperatures that might scorch the product.
What is the term for the use of heat to eliminate a desired number of microorganisms from a food product?
Thermal processing
What happens during Single Effect Evaporation?
Single Stage: a lot of energy is left in the hot condensate.
Enzymatic browning is caused by the oxidation of what type of compounds? Name the enzyme.
Polyphenols; Polyphenoloxidase/phenolase
What is the name of the nonthermal processing method for food preservation which uses short and intense duration pulses of braod sprectum white light?
Pulsed light processing
By what method or physical constant are gelatins rated?
Bloom test (jelly strength)
What is the SI unit for pressure?
Pascal
What is regression analysis?
statistical method to analyze a relationship between 2 or more variables such that 1 of them can be predicted by using the information of the others.
In reference to Stokes Law, How can you create an emulsion in salad dressing?
Shaking the dressing causes the droplets in the discontinuous phase to become smaller, which creates more friction between the droplets and the continuous phase; this results in slower separation of the 2 phases
What is the relationship between viscosity and fluidity?
Fluidity is the reciprocal of viscosity.
Passing an oil through Fuller's earth is a process called _____.
Bleaching.
What is food dehydration?
A unit operation in which water activity of a food is lowered by removal of nearly all the water normally present through vaporization and or sublimation. A process of thermally removing volatile substances (moisture) to yield a solid product. One of the oldest and most common unit operations found in diverse process.
Why are chelating agents used in dairy products?
De-aggregate casein complexes
Assume the temperature of moist air is 60C, and the saturation pressure of water vapor at 60C is 20 kPa. If the measured water vapor pressure is 4.0 kPa, what is the relative humidity of the air?
20% (Relative humidity is the ratio of the partial pressures: RH = 4/20 = 20%)
What term describes properties of a material, such as density, temperature, and pressure that do not depend upon the mass of the system?
Intensive properties or intrinsic properties
What are the freezing and frozen temperature ranges?
Freezing below the temp. at which ice crystals begin to form within the food -10 to -20º C.
The quantity of heat required to change the state of a substance without changing the temperature or pressure is called what?
Latent heat
How many D values are required for an acid canning process?
5 (12 also acceptable)
What is a concentric tube pasteurizer and what is it used for?
Used for fluids with high viscosity, , ketchup, concentrated juices, tomato paste, needs high pressure to move
Which technology is used to purify water?
Reverse osmosis/ RO
What nutritional changes occur in product quality?
Decrease in sensitive vitamins - vitamin C, B vitamins.
What is the name of the point at which condensation begins?
Dew point
What term is defined as the time (min) at a specified temperature required to destroy 90% of all organisms in a population?
D-value
Name the two main methods of preserving food involving the application of thermal energy.
1) Pasteurization 2) Sterilization
Name two examples of w/o and o/w emulsions each.
O/w: milk, mayonnaise, salad dressings W/o: Butter, shortenings
What is nanofiltration?
Pressure 20-40 psig, Sugars divalent salts, dissociated acids rejects, Water and small univalent ions can pass
What is the natural circulation tubular method, how does it work, what is it used for?
Utilizes the density difference between the liquid and the generated vapor to circulate the liquid past the heating surface. It is a continuous process and the residence time is 10-20 minutes. It is used for cane sugar solutions
What is the main advantage of an agitating retort over a still retort?
Increase in heat transfer, decrease time for geometric center to reach desired temperature
What is heating containers by flame used for?
Mainly for small cans, rapid heat transfer - short processing time, increased internal pressure, used mainly for mushrooms, sweet corn, green beans, pears and beef cubes
What are different methods of separation?
Solid liquid (filtration, centrifugation, membrane sep, drying) liquid-liquid (centrifuge, extraction, distillation, membrane sep)
What is the general term for the process where liquid milk is forced through small nozzles at high pressure to break up fat globules into a stable emulsion?
Homogenization
Give 2 examples of emulsifiers.
SPAN, TWEEN, Lecithin, egg white
What is the % sugar w/v of a solution with specific gravity of 1.06 and 15 brix?
15.9% (15*1.06)
What are levels of exposure in kGy for radurization, radicidation, and radappertization?
Radurization: 0.75-2.5 kGy; Racidiation 2.5-10 kGy; Radappertization: greater than 30-40 kGy
Name any three enzymes that are inactivated during blanching.
PME, PPO, lipoxygenase, polygalacturonase,chlorophyllase
Which is greater, the amount of radiation needed to inhibit the sprouting of potatoes or that amount which is lethal to humans?
The amount needed to inhibit the sprouting of potatoes (7500-10,000 rads will inhibit sprouting while only 500 rads is lethal to the human)
What are the factors that determine what pasteurizer is selected?
Type of food, type of packaging, and storage method
What is the relationship between temperature and penetration depth?
as temperature increases, penetration depth decreases
Which food preservation process uses low level of radiation to kill pathogens in food products?
Irradiation
What is the batch pan method, how does it work, what is it used for?
Oldest method of evaporation next to solar evaporation, heating of sample using jacket or internal coils, it has high residence time (many hours). Still used to make jams and jellies
which of the following products is NOT a pseudoplastic fluid: A.mayonnaise, B.fruit purees, C.condensed milk, or D.60% suspension of starch in water
D. 60% suspension of starch in water (its a colloid)
What is hysteresis?
Hysteresis represent the history dependence of physical systems. If you push on something, it will yield: when you release, does it spring back completely? If it doesn't, it is exhibiting hysteresis, in some broad sense.
What is the most common stabilizer used in the production of chocolate milk?
Carrageenen
What is hypobaric storage?
Controlled atmosphere storage with reduced partial pressure of the gases in the environment.
What type of product flow should be used through the plate heat exchanger in HTST pasteurization?
Turbulent
What is the major purpose of blanching foods prior to packaging?
To inactivate natural enzymes in fruits and vegetables prior to further processing.
What are the (3-4) benefits of using SO2 in dehydration processing?
SO2 pasteurization, prevention of enzymatic browning, prevention of non-enzymatic browning, retention of Vitamin C.
What food safety concern has driven increased research into cold plasma and high-pressure processing in recent years?
Non-thermal inactivation of pathogens while preserving fresh-like quality.
What does IQF in frozen food refer to?
Individually Quick Frozen
What is the name of the holes in swiss cheese and what are they caused by?
Eyes; the carbon dioxide produced by the microbe Propionibacterium freudenreichii subsp. shermanii
What process is used in the food industry to concentrate foods by water removal?
Evaporation
Name two refrigerants that are not CFCs.
NH3 and SO2
Describe the principle behind High Pressure Processing (HPP) and its effect on microorganisms.
HPP applies pressures typically between 300–600 MPa uniformly to foods, disrupting cell membranes, protein structures, and enzyme systems in microorganisms without significant heating. It inactivates vegetative cells while largely preserving fresh-like sensory and nutritional qualities.
What term refers to a container that is absolutely impermeable to gases and vapors throughout its entirety, including its seams?
Hermetic
Explain high-pressure processing (HPP).
HPP uses pressures of 300–600 MPa to inactivate microorganisms by disrupting cell membranes and proteins without significant heating. Limitations include cost and limited effectiveness against bacterial spores.
The most recent addition to the allowable materials used in commercial curing of pickles is ______.
D or L-alpha tocopherol
What does the acronym SKU represent?
Stock keeping unit
What is done in packaging potato chips to prevent damage?
Flush bag with nitrogen gas
Naturally occurring and synthetic agents that are used in food processing for production and stabilization of dispersions are called what?
surface active agents (surfactants)
What is the definition of an evaporation?
A device wherein liquid is evaporated from a thin (low concentration) feed material in order to produce a more dense or thick product (concentrate). The feed may be a solution, slurry, or suspension of solid material in a liquid. The hear necessary for vaporization is supplied through heat transfer across metallic surface by condensing steam.
What is the application of sorption isotherms to drying?
Determine Xe , limit of hot air drying
Explain Traditional Nonthermal Processing methods.
Chemicals added to food for preservation to control aW and extend shelf-life through packaing
What is the temperature for supercritical CO2?
31.1 deg C
The temperature at which water condenses is called the what?
Dew point
What are some of the advantages of resistance temperature detectors (also known as RTD)?
Most accurate sensors for industrial applications and have the best long-term stability, can cover a wide range of temperatures, and can hook up to a computer
Explain Sterilization.
Describes a product that is free of all pathogens and MOs; used mainly for medical purposes
Log mean temperature difference is used instead of simple temperature difference in: (a) freezing foods in plate freezers; (b) heating in a liquid-liquid heat exchanger; (c) cooking in a steam kettle, (d) all of the above
(b) heating in a liquid-liquid heat exchanger
In drying, one term used by engineering to describe the property of the air is humidity. What are its units?
Pounds of water per pound of air (or kg water per kg air)
What is electrode ionization?
Removes ions and charge
True/False: a low range or small standard deviation indicates a greater uniformity or less variability in the process.
True
Dried food have Aw less than what?
0.55 (IMF - 0.55-0.90)
Define lag constant for heating/ Give the formula for lag constant for heating.
jh = (Tr - Tpi) / (Tr - T0); jh: lag constant, Tr: Retort (Heating medium) temperature, Tpi: Theoretical "intercept" temperature, T0: Actual initial temperature of the food
How is boiling point linked to evaporation?
Boiling point is the temperature at which the vapor pressure of the liquid is equal to the external pressure
What are the steps necessary in sauerkraut production?
Shred cabbage; salt cabbage at 2.25-3%; pack the cabbage to remove air pockets; create an anaerobic environment; hold at 21 degrees C for 3-4 weeks
The quantity of heat that is gained or lost by a unit weight of product to accomplish a desired change in temperature without a change in state is referred to as what?
Specific or sensible heat
For unsteady state heat transfer what do you plot vs time to get a straight line?
Log of unaccomplished temp difference or (Text - T) / (Text - Ti)
What is the cooking loss percentage of a roast that had a raw weight of 20 lbs and a cooked weight of 15 lbs?
25%
What parameter defines the severity of thermal processing relative to microbial lethality?
F₀ value.
What does the sieve size refer to?
Number of openings per linear inch (25.4 mm). For example, a 100-mesh sieve has 100 x 100 = 10,000 openings per square inch
Why is having excess flour particulates in a milling plant hazardous?
Fire hazard
In canning, what is come-up time?
The time it takes to reach the thermal processing temperature
Name three types of drying.
1) Air convection 2) Drum or roller driers 3) Vacuum driers.
Who developed the concept of quality cost?
Deming
A force of 60 kg m/s^2 is applied to a body with a mass of 2 kg. What is the acceleration?
30 m/s^2 (F = mass x acceleration)
What is the name of the international symbol used to label foods that have been processed by irradiation?
Radura
Discuss the pressure differences between a pump placement and the design of the system and the implications of each?
Where you have the pump, directly before it there is really low pressure caused by vacuum and right after it you have really high pressure which gradually becomes lower. Depending on where you have the pump, if something breaks, the high pressure will flow towards the low pressure, so you don't want the high pressure to be where the raw milk is causing it to flow into the pasteurized milk because then you will lose the whole batch from cross contamination because the milk is now already past the sterilization point, but it the high pressure is with the treated milk, it will flow back to the raw and will not contaminate the already processed milk.
What are 5 factors that will influence dehydration?
Temperature, dryness, air volume, particle size, type of food or load
Which MAP gas has bacteriostatic/bactericidal properties?
Carbon dioxide
Lye is used to hasten the peeling process in some vegetables. What concentration of lye is commonly employed?
Usually 1.0%, generally in the range of 0.5% to 3.0%
Give three reasons for drying foods.
The main objective of drying food is to prolong its shelf-life beyond that of the fresh material, while at the same time minimizing undesirable changes in appearance, texture, flavor, and nutritional value during the drying process. In addition to the preservation of the product, drying can bring about savings in storage and transport of foods owing to the reduction in weight and bulk that occurs during most methods of drying.
What is the fat content or regular mayonnaise?
83% (typical reduced-calorie mayo has 34% fat)
What is active and passive modified atmosphere packaging?
Passive MAP: Uses the natural respiration of the product and the specific permeability of the film to allow the atmosphere to change over time. Active MAP: The intended atmosphere is actively flushed into the package (or oxygen scavengers are added) at the start to achieve the desired environment immediately.
What is the purpose of Refrigeration storage?
To extend shelf-life by slowing down derogatory reactions and limiting microbial growth.
What are the advantages of freeze drying?
Low thermal damage, good vitamin retention with minor exceptions, minimal product shrinkage, long shelf life if product are suitably packaged, retention of biological activity, best in terms of quality
What are the potential issues with spray drying?
Tg, if rubbery sugar very sticky and build up on wall, so need to make sure it becomes glassy before hits wall. Powder explosion: can happen when enough particles get into the air and if spark explosion will occur
True/False: metals are added into microwavable popcorn package to achieve increased uniformity of heating.
True
What type of pump is most efficient in transferring low viscosity liquids?
Centrifugal
What is tempeh and what microorganism is used to ferment it?
Fermented soybean; Rhizopus oligosporus
Describe the flow behavior of a dilatent material.
Shear thickening
What is the surface temperature of a block of dry ice?
-109.3 degrees Fahrenheit (-78.5 degrees C)
What is the link between TDT and processing time?
when thermal death time is reached sterilization would be completed thus, process time can be the same as TDT
To calculate using the perfect gas law, what type of pressure must be used?
absolute pressure
What is the mechanism of action for the microbial destruction by High Hydrostatic Pressure and Pulsed Electric Fields?
PEF: electroporation (the formation of pores in cell membranes by the action of high voltage electric fields). PEF inactivation via electroporation is believed to be associated with the migration and accumulation of charge across the cell membrane under the action of applied electric field; HHP: Rupture or damage to cell membrane
What is the difference between Degrees C and Kelvins?
Kelvin is always 273.15 degrees greater than Celsius
Name two methods for irradiation of foods.
Cobalt 60, x-rays, or E-beam
If the D-value of the critical organism is 0.2 and the product is canned peas, what should the F-value be?
F = 2.4 (=12D)
Why do foods freeze faster than they thaw?
Water layer insulates, thermal conductivity and thermal diffusivity of ice>water
In lye peeling of vegetables, give a typical concentration of lye used.
One percent (accept 0.5 - 3%)
What is the difference between accuracy and precision?
Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other.
Describe two kinds of fluids that require the application of yield stress before any flow occurs.
1) Bingham liquids 2) Plastics
Name three compounds capable of poisoning the catalyst during commercial hydrogenation.
Phospholipids, water, sulfur compounds, soaps, partial glycerol esters, carbon dioxide, and mineral acids.
What organization governs microwave regulations?
FCC
Additional component in mass and energy balance equation in food processing
- Time sucrose +heat + acid --> Hydrolysis/inversion
What happens to enthalpy of steam when the temperature increases at constant pressure?
Increases
What is a disadvantage of UHT?
In milk some enzymes like proteases and lipases more heat resistant - can cause flavor changes during prolonged storage
Of the following four choices, which is not a commercially used source of energy for food radiation? a. gamma-rays; b. x-rays; c. electrons; d. beta-rays
d. beta-rays
Name a purification step used to produce high fructose corn syrup after starch liquefaction.
Carbon treatment of liquor
What is the difference between dried food and dehydrated food?
Dehydrated food as no more than 2.5% water on a dry basis and dried food can be more than 2.5%
Please put the following steps in order as they would be used for processing? Grinding, cleaning, Cocoa separation, shell removal, conching, roasting, addition of other material, tempering
Cleaning, roasting, shell removal, grinding nibs, cocoa separation, addition of other material, Conching, tempering
List three factors that contribute to the buffering capacity of milk.
Phosphate, citrate and lactate salts, whey proteins, carbonic acid from the dissolved CO2
What changes occur in quality during food processing?
Degradation of pigments Loss of vitamins Enzyme activity Oxidation of lipids.
How do natural and forced circulation affect the boundary layer?
Natural circulation has laminar flow and an increased boundary layer, and forced circulation is turbulent flow and therefore decreases the boundary layer
Which food is made by fermenting soaked and cooked soybeans with a mold, usually rhizopus?
Tempeh
What relies on abrasion of meat against stainless steel rotating paddles to accomplish diffusion and binding of curing ingredients with meat?
Messaging
What is the falling film tubular evaporator, how does it work, what is it used for?
Going with gravity instead of against it, this results in thinner and faster moving film and gives rise to shorter contact time and further improvement in the heat transfer coefficient. The key technical hurdle is the even distribution of liquid to each of the tubes
What is the primary mechanism by which heat transfer occurs in a canned liquid?
Convection
True or False. The greater the temperature difference between the heating medium and the food, the greater will be the rate of heat transfer.
True
What are 3 reasons for piling blocks of curd during the cheddaring process?
Acid development, texture development, uniform heating
What is the viscosity of water at 25 C?
1 cP or 1 mPa s
What does HEPA stand for?
High Efficiency Particulate Air (filter)
What temperature type of sensor is based on the effect of a junction between two different metals that produce a voltage that increases with temperature?
Thermocouple
In sterilization and pasteurization, what is the purpose of the hold tube?
Make sure the product has the correct residence time (aka the time necessary to sterilize/pasteurize at a certain temperature)
If you had 10 ml of Kool-Aid with 10% sucrose, how much water should you add to make the drink 0.1% sucrose?
990 ml water
Define "microencapsulation".
Microencapsulation is the science of trapping components (core or active) into a secondary material (encapsulant, wall material, carrier, or cover), producing small solid particles (1–500 μm in size). These particles are able to release their contents at a specified rate or under specific conditions.
what is the term for an ingredient that is added during processing that is later, during shipping, handling, and storage is altered, removed, or diminished?
a processing aid
How do refrigeration and freezing affect staling? a. both slow staling b. fridge slows staling, freezing aids staling c. fridge aids staling and freezing slows staling d. both aid staling
c. fridge aids staling, freezing slows staling
What would you do to change a temperature reading from Farenheit to degree Rankine?
add 459.67
What is one advantage and one disadvantage to direct heating?
advantage: rapid heating minimizes organoleptic changes, less fouling/burn-on. disadvantage: requires culinary steam (expensive), increases volume of product (adds water from steam), bad for products containing oil (oxidizes quickly)
Glucono lactone is used as a food additive when slow what is needed?
Acidification.
What are descriptions of routine tasks in a food processing operation?
Standard operating procedures
How does the Short-Tube Evaporator function?
In Short-Tube Vertical (STV) evaporators (the "standard" evaporator), the liquid is inside the tubes and the steam is in the shell. Sometimes, steam is fed through the inside of internal tubes, while evaporating product flows around the outside. Density changes cause warmer fluid to rise and cold to sink. Used sometimes in sugar processing.
Name 3 non-thermal food processing technologies.
UV light, ultrasound, high pressure, pulsed light, pulsed electric field, irradiation
Fully developed turbulent flow of fluid in a pipe is achieved when the Reynolds number is greater than ______?
10000
The process of irradiating foods is sometimes referred to as ____.
Cold sterilization.
What are cryoprotectants?
Substances that protect against the dehydration which destroys structure and texture caused by freezing.
Which class of food additives has faced increased scrutiny due to potential impacts on gut microbiota?
Emulsifiers (e.g., polysorbates, carboxymethylcellulose).
Explain Pasteurization.
Process used to inactivate pathogens (e. coli) and vegetative (alive) pathogens
List the three radiate particles, alpha, beta and gamma, in the order of their increasing penetration power.
Alpha < beta < gamma rays
What are the different types of centrifuges?
Disk bowl, decanter, tubular, basket
What is the purpose of an atomizer in spray drying?
step very important : the formation if sprays having the required droplet size distribution is vital to any successful spray dryer operation so that powder specifications can be met. The key is to produce tiny uniform particles
Give another name for the Couette viscometer?
Concentric cylinder
What is the boiling point of water in °F, °C, and °K?
212 °F, 100 °C, 373 °K.
A product with drying ratio of 5 yields 1 kg of dry product for how much water removed?
4 kg (drying ratio is the amount of fresh material need to produce 1 kg of dried product)
What is UHT used for? What are some examples?
Used for liquid foods: milk, juices, cream, wine, baby food, tomato products, salad dressing
What is the most common technique used to make dried pet food?
Extrusion
Name 5 types of heat exchangers used for food processing.
Shell and tube heat exchanger, spiral heat exchanger, plate heat exchanger, jacketed pans, scraped surface heat exchangers, corrugated tube heat exchanger, finned tube heat exchangers, double pipe heat exchanger
What is the slowest freezing method?
Sharp freezing
Define specific heat and provide its units.
The quantity of heat required to raise the temperature of a unit mass by 1 degree (Kcal / kg¼C or Btu / lb¼F or J / mol K)
What major food-system concern has driven rapid growth in alternative lipid sources such as algae oils?
Sustainability and omega-3 supply limitations from marine fisheries.
What is ohmic heating?
It is where an electrical current is passed through a suitable conducting product causing it to heat
What are some of the benefits of using a conveyor system in an air impingement oven?
Help cook food well/evenly, control temperature and time, control cooking, cook large amounts of food in a continuous process, shorter process times, improved product quality, can use for both heating and freezing foods
What are different methods of food preservation?
Food preservation through energy input or temperature reduction (chilling, freezing, blanching, canning, pasteur)Food preservation through water removal (concentration: evap/freeze, frying, food dehydration: hot air, spray, drum, freeze dry, osmotic dehydration)
How does heating of a dielectric material via dipole rotation occur?
Frictional heat between dipoles (e.g., dipoles in water) while rotating to orient themselves to the rapidly oscullating electric field
What does URP stand for?
Unique radiolytic product
What is the main purpose of pasteurization?
To destroy pathogenic microorganisms
How do you convert F to Rankine?
R = F + 459.67
The z-value you have calculated for your process is 18 F. What is the z-value in degrees Celsius?
10 degrees Celsius
At what frequency are microwaves typically at?
300 MHz to 300 GHz
What law of filtration rate to change in presse drop across a filter bed?
Darcy's law
In unsteady state heat transfer, what is the dimensionless number used to evaluate the importance of internal and external resistance to heat transfer?
Biot number
What is the Aw limit or requirement for filing a process when heat-processing foods in hermetically sealed containers?
0.85
Convert 298 K to Celcius degrees.
25°C
What is the classification of fluids according to Reynolds number?
Small (<2100): Laminar or streamline flow; High (>4000): Turbulent flow
In food engineering, with respect to refrigeration, what is a COP?
Coefficient of Performance
The rate of heat penetration into canned foods is dependent on the mechanism of heat transfer. Fluid foods heat by ___ and solid foods heat by a ___ mechanism.
1) Convection 2) Conduction.
What is the refrigeration temperature range?
Temperature range - approximately -1 to 8 C.
What factors affect heat penetration in canned foods?
Container size/shape, product consistency (homogenous or not), type of retort (still vs agitating)
If fermentable carbohydrates are present when pickiling food, what percent acid must be present to prevent growth of lactic acid bacilli and yeasts?
0.036
Name the two main methods of preserving food involving the application of thermal energy.
Pasteurization and sterilization
What is the fundamental equation for the 1st Law of Thermodynamics?
(delta)u= q + w, where (delta)u - internal energy, q - heat, w - work
How does vapor pressure effect evaporation?
Water will naturally evaporate into the air until the rate of evaporation = the rate of condensation
What is the definition of calorie?
The quantity of heat needed to raise the temperature of 1 g of water by 1°C.
What type of flow has the Reynold number of 6000?
Turbulent
What are the different variables that are monitored in a retort?
Temp material, temp steam, temp cooling water, process time, hearing and cooling rates
Of the following four choices, water at 18 C boils at approximately which absolute pressure? a) 0.2 kPa b) 2.0 kPa c) 20.0 kPa d) 200.0 kPa
b) 2.0 kPa
What are the components of a supercritical fluid extraction system?
Solvent compressor or pump, extractor, temperature/pressure control system, separator/absorber.
What is a food additive?
substances added to food to preserve flavor or enhance its taste, appearance, or other qualities
What is an intermediate moisture food?
Contains 10-50% water with an Aw of 0.60 - 0.90
With regards to starch, what is the value determined by the difference in peak viscosity and final viscosity which corresponds to gel formation after cool down following gelatinization?
Set back viscosity/set back value
What is zymology?
The science of fermentation
Why do you add aluminum sulfate to pickles?
It can improve the crispness of the pickle (it's a firming agent)
With respect to thermal processing, what does TA stand for?
Thermophilic anaerobe
Given a closed vessel of an ideal gas at room temperature, what happens to the density of the gas when the temperature of the vessel is raised to 100 C?
The density remains the same.
The dimensionless ratio of the heat transfer coefficient at the surface of a solid to the heat conductance to the center of the solid is known as what?
Biot number
What does HPP stand for?
High Pressure Processing
In a thermal processing operation, if the D value is 0.5 minutes at 250°F and the initial microbial count is 100,000, what is the microbial count after 2 minutes?
10, a decrease of 4 D values
What term refers to the percentage change in length of a material due to pulling stress before breakage?
Elongation or strain
Particles with dimensions greater than 1 millimicron and less than 0.1 micron are called_.
Colloids
Name the inorganic chemical additive that is often included in brines to minimize softening of vegetables during thermal processing.
CaCl2
What is 1 way to measure sorption isotherms?
Gravimetric (weight changes), manometric (vap press changes), hygrometric(eq RH determined)
Why is the recommended storage temperature for potatoes 7°C to 10°C (45-50 F)?
Storing potatoes at room temperature or higher leads to sprouting and rapid shriveling. Temperatures below 4°C result in more reducing sugar formation creating the potential for browning (called Cold-Induced Sweetening). To prevent Cold-Induced Sweetening while avoiding spoilage, potatoes for processing (chips/fries) are typically stored at 7°C to 10°C (45-50 F).
The FDA does NOT allow the irradiation of herbs and spices.
False
What is the denominator of a t-test?
standard error of the mean
How many pascals equal one newton per meter squared?
1
State Stoke's law.
F = 6(pi)r(eta)v; Drag force = 6(pi)sphere radius.fluid viscosity.velocity of the sphere
How is canned food pasteurized?
Using batch type retort or a continuous tunnel type pasteurizer
What are different methods of congregation?
Extrusion, encapsulation, mixing/emulsify
What is the difference between direct and indirect heating systems?
Direct: having steam condense into a product (directly contacts product). indirect: the use of equipment to exchange heat between the surface that is heated and the product
A retort temperature of 250oF is achieved with how many pounds of pressure?
15
Give three characteristics of spray drying.
Used to create powders, very rapid process, atomizers make food into mist
What chart is used to relate moisture content to water activity?
Sorption isotherm.
What is splashing feeding for drum drying?
suitable to products with a high sediment rate, used in single and twin drum dryers
What is the difference between X-ray and gamma-ray?
X-ray is generated from a shift of electron of the orbital of an atom whereas gamma-ray is generated by shifting of energy levels in a radioactive nucleus. Gamma rays generally have much higher energy levels and shorter wavelengths than X-rays.
Quick Freezing
32 F to 25 F in 30 minutes, developed by Birdseye
What is the purpose of counter-current air flow in spray drying?
Drying air and particles move through the drying chamber in opposite directions, this mode is suitable for products which require a degree of heat treatment during drying, product will be overheated unless can withstand heat, temp of the powder leaving dryer is higher than exhaust air temp
What are the advantages of osmotic dehydration?
Less energy cost (30-40%lowe, no phase change), less heat impaired changed in the food components , retention of natural quality, desirable nutrients added during preservation process (fortification)
What are the components of steam table?
Specific volume, entropy, enthalpy
Describe how plate heat exchangers work in pasteurization systems.
Thin metal plates separate hot and cold fluids, allowing efficient heat transfer for continuous pasteurization of liquids like milk and juice.
Under which pH value can potassium sorbate reach its most effectiveness?
pH < 5
Which heat transfer mechanism dominates in retort processing of canned foods?
Convection.
At a Reynold's number of 10,000, what type of flow will be experienced?
Turbulent
Name 2 approved bleaching agents used in flour production.
Cl2, NOCl, N2O4, benzyl peroxide, ClO2, NO2, lipogenase
When vitamin D is added to milk to make fortified milk, is it before or after pasteurization?
vitamin D is generally added prior to pasteurization because it is heat-stable
What are the substrates for Miso production?
Koji (fermented rice) and Soybeans
Give two ways starch is modified for use in foods.
Cross linking, derivatives e.g. phosphate esters, acid/enzyme thinning, precooking
Name 3 advantages of microwave heating.
Reduced process time, higher food quality, better appearance/flavor/taste, convenient, easy clean-up, decreased cost of electricity, increased retention of vitamins and minerals
Describe the difference between shear and normal stress.
Shear is parallel to the surface, normal is perpendicular
What are some disadvantages of aseptic processing?
Over processing, not easy to ensure the sterility of all equipment used in the process, products that contain particulates processed at high temperatures lose shape and form during the heating and cooling steps
What is the relationship among freezing rate, crystal size and food quality?
Faster the freezing rate, smaller the crystal size, higher the food quality
What is the effect of drying on Vitamin C?
vitamin C reduction/loss
Which category of food materials can be heated by microwave?
Dielectric material.
Name 4 advantages of using enzymes in food processing.
They are natural, nontoxic substances, generally catalyze without unwanted side-effects, active under very mild conditions of temperature and pH, active at low concentrations, rate of reaction can be controlled, can be inactivated after reaction.
Name uses for the 3 types of caramel colors that are produced.
Color for cola drinks, brewers color for beer, and bakers color to give brown, baked color
What are two non thermal methods that are currently under investigation
pulsed electric field, and high hydrostatic pressure
What is spray feeding for drum drying?
Spray feeding-material is atomized by nozzle on drum surface, can be located at bottom of drum or other, quantity of product applies is controlled by nozzle system and independent of other parameters
In IR heating, what happens to the wavelength as temperature increases?
wavelength gets shorter
In the making of chocolate, following roasting, the cocao beans are loaded into a machine called a winnower; what does this machine do?
It removes the outer hulls and separates the 'nibs' by size
What is the purpose of pasteurization for low acid foods?
Primarily for the destruction of pathogens, and then secondly for the destraction of spoilage organisms and deactivate enzymes
What is the name of the law that states that "the total pressure in a gas phase is equal to the sum of partial pressures of the components?"
Dalton's Law
How are food freezing systems categorized?
2 categories: Indirect contact and Direct contact systems. How to select: Depends on type of food and type of package.
How do Eutectic plate systems work?
A frozen salt solution at its eutectic temperature - water and salt form a single phase or a solid solution. Solution melts at its eutectic temperature and heat is removed from the environment and provides refrigeration. (Potassium bicarbonate, potassium chloride, ammonium chloride, and sodium chloride). Temperature range: -5 to -21 C / air circulate across eutectic plates into the refrigerated chamber this provides refrigeration.
What is the fungal genus responsible for the production of soy sauce?
Aspergillus (oryzae is species)
What is the pressure range usually used for HPP?
300-700 MPa
In a pipe, what type of flow occurs when the Reynolds number is less than 2100?
Laminar
High-pressure processing (HPP): Explain how HPP inactivates microorganisms. Name two foods commonly processed using HPP. Describe one advantage and one limitation of HPP.
How HPP inactivates microorganisms: Applies pressures of 300–600 MPa, Disrupts cell membranes, protein structure, and enzyme activity without high heat. Two foods commonly processed with HPP: Guacamole, Deli meats, Fruit juices, Ready-to-eat meals One advantage and one limitation: Advantage: Retains fresh flavor, color, and nutrients; Limitation: High equipment cost and limited effectiveness against bacterial spores
What is the particle size range for ultrafiltration?
0.001 to 0.1 microns
What is a common unit of brightness or luminous intensity?
Candella
What are the common metric units for the following: acceleration, power, mass, force
Acceleration= meters/seconds squared; power= watt; mass= kg; force= Newton
How does fat have "shortening power"?
It interlaces between protein and starch structures and makes them tear apart easily and 'short' rather than allowing them to stretch long. This is a tenderizing effect for meat and baked goods.
Name the confectionaries that contain gelatin.
Gummy bears
What is the most common syrup added to soft drinks?
High Fructose Corn Syrup
What is the D value of a microorganism that is decreased in population by a factor of ten in two minutes at a constant temperature?
Two
What is Commercial Sterilization?
To achieve long-term shelf stability for canned foods and other products: majority after being placed in container but some are aseptically processed.
What is a PERT chart and how are they used by food companies?
PERT - Program Evaluation Review Technique Used as an organization tool for food product development
What are four parameters which affect the efficiency of lye peeling operations?
Concentration of lye; Time; Temperature of solution; Lye and peel removal systems
In a Bingham plastic fluid, what is the initial resistance that must be overcome before the flow starts and the system behaves as true Newtonian?
Yield stress
What is the term given to the process of kneading and aerating melting masses of chocolate to develop smoothness, viscosity, and flavor?
Conching
What are two types of processes that involve the removal of thermal energy and at what temperatures are these two processes?
Refrigeration (40 F or 4.4 C) and freezing 0 F or -17.8 C)
What is yield stress?
Minimum shear stress required to initiate flow
Generally, what is the net rate of heat transfer of food?
Rate of absorption- rate of emission
What factors influence dehydration?
Temp, dryness, air vol, particle size, type of food, load
Name 4 types of membrane separation systems.
Reverse Osmosis, nanofiltration, ultrafiltration, microfiltration
Define commercial sterility.
When a food has been processed enough to prevent spoilage and pathogen growth. Some spores may be present.
What is a Disc bowl centrifuge?
for sub-micron particles, designed to maximize the surface area for separation, thus providing the most cost effective separation solution, applications (fish, olive oil, breweries, wineries, jucies)
What is dipping feeding for drum drying?
Used in single and twin dryers, dryer is partially submerged in a tray and product in tray adheres to the surface as the drum rotates, good for certain suspensions of solids and used usually with a recirculation of material to prevent the setting of the solid in a tray
What is centrifugal separation?
Utilizes fundamental physical laws and centrifugal force. Centrifugal force is produced through rotation around an axis. The force generated through the rotation acts in an outward direction. Depending on the speed of the rotating body, it increases or drops on the circular path. Mechanical separation technology makes use of this property when light, heavy or substances of different density have to be separated from each other.
Name the 4 steps of refrigeration.
Compression, condensation, expansion, evaporation
What are some advantages of using the formula (ball) method to calculate lethality?
Allows use of semi-log curves for detailed analysis of time/temp data, can calculated processes of a rang of IT and RT utilizing heating factors, conservative process model
Name the methods for direct heating and indirect heating.
1) Direct heating methods: toasting, frying, steam injection, steam infusion, spray drying, baking 2) Indirect heat exchangers: plate, tubular, shell and tube, scraped surface heat exchanger.
For a refrigeration cycle, what term is used to describe efficiency?
COP, the coefficient of performance
What do we dehydrate food?
Extend shelf life, quality enhancement, ease of handling, packaging, handling, transportation
Name 2 heat stable enzymes in food that are important to the quality of aseptic products.
Lipase, lipoxygenase, catalase, chlorophylase, peroxidase, pectinase, protease, ascorbic acid oxidase, alkaline phosphatase.
With regard to can defects which occur during thermal processing, what is buckling?
Permanent deformation of the can ends caused by excessive internal can pressure compared to external pressure. ( occurs when there is insufficient pressure during cooling), opposite of panneling
Food radiation is capable of destroying all the following in food except:
Prion
What are the three types of junctions in a thermocouple?
Exposed, ungrounded, grounded.
Convective flow is driven by a gradient of what property?
Density
How many gallons of ethanol will a bushel of corn yield?
2.5 gallons
What is F0 value?
Converted to a reference temperature and z-value which is Z-value of 10°C and temp of 121°C.
Explain Commercially Sterile.
Describes a product free of all pathogens and other microorganisms that could potentially grow in the product
What is mass balance? Why is it important?
Input-output=accumulation, and in a steady state process accumulation = 0 so: mass in =mass out
Give 3 visible signs of chilling injury.
Poor ripening, pitting, collapse of structural integrity, development of off-flavors and rotting
How is the pasteurization time and temperature selected?
It is based upon the principle of D-value and Z-value
If the pressure at the bottom of a 10 meter lake is 1.2 atmospheres, the surface area of the lake is 200 square meters, and the temperature is 25 C, what is the pressure at the bottom of a 10 meter test tube with a surface area of 20 square centimeters?
1.2 atmospheres
What is the term for a non-pathogenic microbe used instead of a pathogenic microbe to test process effectiveness?
Surrogate (Indicator organism also acceptable)
The door of a microwave is often glass with a metal mesh imbedded, why is that so?
while microwaves can go through glass, they cannot go through metal, and so the mesh has holes small enough that microwaves cannot pass through but allows for the person to view the food inside
What is the name of the process that is used for high-acid foods? The food is held at 170-190 deg for 25-30 minutes.
Hot, fill, hold
At what pressure do popcorn kernels pop?
135 psi
What are the main stages of canning?
Heating phase (removal of air, come-up time, holding time at processing temperature), cooling phase
Acrolein is a potentially toxic product that can occur in food processing applications. Give the source and the type of degradation can yield this chemical.
Thermal decomposition of fats
The process known as agglomeration for instantized products is used for which type of powdered product? Freeze or spray dried?
Spray dried
What is the most commonly used supercritical fluid?
Carbon dioxide
What is BHT, BHA and their uses
They are both synthetic antioxidants added to food to preserve natural compounds and food quality
How does ionic polarization contribute to heating?
Ions in solution move in response to applied electric field component of the microwave, and the collisions with other molecules convert kinetic energy into heat
What is the dairy industry's most important kind of air convection drier?
The spray drier
Define triple point?
Pressure-temperature at which a substance is at solid, liquid, and vapor phase at the same time. For water, it is 611.73 Pa and 273.16 K.
Give 3 advantages of food dehydration over sun drying.
More controlled conditions, shorter drying time, better sanitary conditions, no climate losses due to weather, some products (such as milk) cannot be sun dried
What is the Westphal balance used to measure?
Specific gravity
What are some advantages of indirect heating?
Easier to control food temperatures, process viscous products without causing food to burn, conserves energy by heat regeneration
What are the plate type evaporators that are used?
Rising film, falling, parvap (similar to wiped film) and paraflash (similar to forced circulation)
What is the D value of a bacterial population which is decreased by a factor of 10 in 2 minutes?
2
What are some of the external conditions that affect drying?
Humidity, relative humidity, are velocity, dry bulb temperature, wet bulb temperature, dew point temperature, specific volume, enthalpy, geometry of the food
The main component of an Infrared Heating Equipment is the radiator, name 3 types of radiators and length of wave.
Gas heated (long waves), electrically heated radiators (tubular/flat metallic heaters (long waves), ceramic heaters (long waves), quartz tube heaters (medium/short waves), and halogen tube heater (ultra short waves))
Coextrusion involves using two or more extruders to form multilayer structures.
True
Define Z-value.
Temperature change (in C or F) required to change the D-value by a factor of 10
Which food processing technique could be named as 'controlled spoilage'?
Fermentation
The sun can be approximated as a blackbody at what temperature?
5800K
A plate freezer is a direct or indirect freezing method?
Indirect (NOTE: the other team does not get a chance to answer)
The S.I. unit of pressure is the Newton per meter-squared, also called the Pascal. Because this is an inconvenient size unit for many purposes, standard atmospheres are often used. To two significant digits, how many Pascals are in one atmosphere?
1.0 x 10^5 Pascals per atmosphere
Which of the following is not found on pyschrometric chart: Enthalpy, abs humidity, wet bulb temp, thermal conductivity
thermal conductivity
Give three reasons for adding starch to food.
Coating and glazing agent, thickening agent, colloidal stabilizer, moisture retention, gel forming, binding
What is reverse osmosis?
Reverse osmosis is a process that removes foreign contaminants, solid substances, large molecules and minerals from water by using pressure to push it through specialized membranes. It is a water purification system used to improve water for drinking, cooking and other important uses.
Which processing step causes most loss of B and C vitamins in peas? A. harvesting B. blanching C. Frozen storage D. home cooking
B. blanching
What are the different membrane module selections?
Flat sheets - can wrap into different shapes, Plate and frame module - feed fed through spacer(between membranes) and permeate moves through membrane, Spiral module - product flows through center and then permeate moves outward through membranes, Tubular >10mm tubular, Capillary 0.5-10mm, <0.5mm hollow fiber
What sacrificial metal is utilized in cans to prevent oxidation by Fe2+?
Tin
The enzymes alpha amylase, glucoamylase, and glucose isomerase are used in sequence to produce what food ingredient?
High fructose corn syrup
What is the purpose of an ascorbic acid dip for fruits prior to freezing?
Prevention of browning (vitamin C is oxidized by polyphenol oxidase rather than the plant catechol-tannin complexes)
Why is scale important? What is scale up?
This is very important for having to feed over a million people. A scale up is increasing the production from a benchtop to a pilot plant scale to an industrial scale. This has a big effect on mass production including the overall cost (reduction) and quality control
What is the product from vegetable oil, acid and egg yolk?
Mayonnaise
Name of the food derived from dried maize that has undergone nixtamalization)
Cornmeal that has been soaked in an alkaline solution, e.g., limewater (a process known as nixtamalization), it is called masa harina (or masa flour),
Name four types of sucrose used in industry.
Bottler's, canners, liquid, granulate (sanding, baker's special, cordial, fine, gelatin, unigran), powdered/ confectionary sugar, brown sugar (dark and light)
What happens to the freezing point as ice is removed?
As water is removed from the system and the concentration of solids increases and the freezing point of water decreases.
What are the 2 types of direct heating?
steam injection and steam infusion
How many D-values are required for an acid canning process?
Five
What are the physio-chemical reactions affecting product quality?
1. Component migration - migration of components in and out of foods. Water - foods can pick up or lose moisture from the environment. 2. Phase change - loss of product quality over time - stale bread due to retro-gradation of starch - slow crystallization of elements of starch.
What are some of the disadvantages of a tubular heat exchanger?
Excessive pressure drops, inability to open and inspect surfaces, only 70-75% regeneration which is lower than plate heat exchangers, fouling tendencies because of low shear, restriction of products by viscosity and particle size
What is the unit of Reynolds number?
None
Two main functions of emulsifying salts in processed cheese making?
Flavor, emulsification
What are the different types of atomizers available?
Rotary (wheel) atomizer: spinning discs or vaned wheels or cups. Nozzle atomizer: pressure nozzles and two-fluid nozzles
What is the S.I. unit of radiation absorbed dose?
The gray (also acceptable is Joule per kilogram)
Which dimensionless number represents the ratio of momentum diffusivity to thermal diffusivity?
Prandtl number
Describe the flow behavior of a pseudoplastic material.
Shear thinning (viscosity decreases with increasing shear force)
Chemical additives are typically added in what range? A. 1-5% by weight B. ppm to <1% by weight C. ppb to ppm
ppm to less than 1% by weight
What are the changes in ice crystals during recrystallization?
Three categories: - Isomass, a change in shape of the ice crystal resulting in reduction of surface-to-volume ratio. - Accretive, the joining of two ice crystals to form a much larger crystal. - Migratory, an increase in size of crystals and an overall reduction in the number of ice crystals as a result of liquid water migrating from one crystal to another.
Why does water heat rapidly in a microwave oven?
Water is a dipole molecule. As the microwave field oscillates, the dipole of water will try to oscillate to follow the field
What two types of equipment achieve powders as end products?
Spray and freeze dryers both achieve powders
Name 2 types/examples of direct-contact freezing systems.
Continuous immersion freezing: food carried through a bath of refrigerant; CO2, liquid nitrogen. Continuous cryogenic freezing: Has its advantages and disadvantages.
There are many types of ISM bands available for dielectric heating, what does ISM stand for?
Industrial Scientific Medical
Name 2 refrigerants used in mechanical compression refrigeration systems other than Freon and its replacements and how is the efficiency of the compressor expressed?
Hydrofluorocarbons (HFC) and hydrochlorofluorocarbons (HCFC); COP
match the following common descriptions w/the correct classification of flow behavior: pseudoplastic, dilatent, Bingham plastic, Thixotropic
Pseudoplastic= shear thinning;Dilantent= shear thickening;Bingham Plastic= yield stress; Thixotropic= thickens w/time
What vegetable oils are approved for use in butter manufacture?
None
Why is vitamin C usually not used for fortifying milk?
it is easily destroyed by pasteurization and normal storage; it is also against current standard of identity for milk
What are some of the disadvantages of using a thermistor?
Limited temperature range, low accuracy at higher temperatures, non-linearity at higher temperatures (resistance over temperature decreases exponentially)
Tomato catsup is described as a: a. Newtonian fluid or b. Non-Newtonian fluid.
b. Non-Newtonian fluid.
What are feeding methods?
applying product to drum surface, depends on drum arrangement & solid concentration
What is the volume (in liters) of 1 mol of gas at standard temperature and pressure?
22.4 L
Air freezing, indirect contact freezing and immersion freezing are three freezing preservation methods. Which of these types of freezing is typified by the Birdseye Multiplate Freezer?
Indirect contact freezing
What are the three heat transfer modes? Explain their mechanism.
Convection - flow of air or water over a physical body, maintains large gradient. Conduction - direct transfer between two physical bodies (surface area, gradient, heat, conduction) . Radiation - transfer of heat between two physical bodies that are not in direct contact with each other. (Evaporation) - liquid becomes gas (heat loss), release of energy in the form of heat
What are tunnel dryers?
Product on trays, stacked, on trucks, rolled into tunnel, air movement by fans 2-6m/s, flow of air can be co-current or counter-current
What are the 3 simple components of a radio frequency heating system?
Radio frequency generator, electrodes, and product
The irradiated product that most US consumers have eaten is what?
spices
What is the difference between total mass balance and individual mass balance?
There is a balance equation for each component and then there is a balance that takes everything into account. For example if a unit like apples involves 3 components (sugar, water, solids) then you will have 3 independent mass balances and one total mass balance
What are the different types of dryers?
Cabinet/tray/compartment dryers, tunnel dryers, conveyor belt dryers, kiln drier, foam mat drier, fluidized bed drier
Until a few decades ago, Freon-12 was commonly used in what food processing operation?
Refrigeration
What are 4 advantages of impingement heating?
Efficient heat transfer, uniform heating, better moisture retention in food, heat transfer is independent from the conveyor belt, easier nozzle configuration, adjustable velocity and temperature
What makes "slow" catsup different from "fast" catsup?
"Slow" catsup = higher processing temps inactivate polygalacturonase "Fast" catsup = lower processing temps, therefore polygalacturonase is able to break more pectin down, causing a runnier product
Who was the first person in Germany to develop commercial refrigeration?
Linde
What is the better-known identity of minus 273.15 degrees Celsius?
Absolute zero (zero degrees Kelvin)
How does high sugar content in foods affect the drying process?
High sugar content causes foods to dry slower, as sugar attracts water
What is "Radurization"?
Low-dose irradiation (0.1–10 kGy) intended to extend shelf life by reducing spoilage microbes (similar to pasteurization)
A measurement of what fluid flow property can be made with a Pitot tube?
Velocity head due to flow (just velocity is acceptable)
What are the advantages of processing with a hydrostatic cooker relative to a still retort?
Continuous flow; external pressure balances internal pressure during heating and cooling, leading to more efficient processing.
What is the heat step in coffee that produces flavor?
Roasting
What is G-force?
Measure of the magnitude of the acceleration relative to the local gravitational acceleration
Define kinematic viscosity.
Ratio of absolute viscosity and density
For the chemical reaction CaCO3 --> CaO + CO2 (g) at 298K at equilibrium, which of the following is true? (a) ?G=0 (b) ?H=0 (c) ?S=0 (d) all of above
(a) ?G=0
What two types of heating are dielectric heating?
Microwave and radio frequency
Why are lethality calculations important?
Allows us to compare the effect of different temperature and time combinations on microbial destruction. Also the temperature changes constantly in a retort and we want to know the effect of the temperature time profile on killing microbes
How is the specific gravity of a solid or a liquid defined?
It is defined as the density of the solid or liquid divided by the density of water at the same temperature.
A substance that exhibits an increase in viscosity with an increase in shear rate is known as what type of fluid?
Dilatant
What type of radiation is of primary interest in food preservation?
Electromagnetic (gamma)
HTST is known as a method for pasteurization. What does HTST stand for?
High temperature short time
What are the pre-fixes for million, billion, and trillion?
Mega, Giga, Tera (10^6, 10^9, 10^12)
What is the rising-falling film evaporator, how does it work, what is it used for?
Combines the previous two, the purpose is to save headroom, about half the height of the previous two methods
What are some of the applications of freeze concentration?
Coffee, citrus, juices, beer, wine, vinegar, dairy products, meat/fish extracts
Name 5 dimensionless numbers used in heat and/or mass transfer calculations.
Biot number (Bi), Fourier number (Fo), Fanning friction factor (f), Grashoff number (Gr), lag coefficient for mass transfer (j), Lewis number (Le), Nusselt number (Nu), Plank number (Pk), Prandtl number (Pr), Raleigh number (Ra), Reynolds number (Re), Schimidt number (Sc), Sherwood number (Sh), Stefan number (Ste)
Gel formation in frozen egg can be prevented by
2-10% NaCl 8-10% sucrose
What is the rising film tubular method, how does it work, what is it used for?
This is the first modern type of evaporator, the forming of vapor bubbles inside the tubes causes a pumping action giving high liquid velocities. Residence times are low, hear transfer coefficients are high and hence heating area is reduced and initial capital is lowered. Need at least 25F temp difference to establish a well developed film. It is used for condensed milk.
How is saturated steam used in exhausting?
Flush retort with steam to remove air, Also air a thin boundary layer around the containers which reduces heat transfer from steam to containers
Explain how gamma rays destroy microorganisms.
Gamma rays induce free radical formation, which can interact with DNA and other cellular constituents, which would destroy the organism.
A US gallon is equivalent to how many UK gallons (out to 1 significant figure)?
0.8 (0.83)
What is the relationship between pasteurization time and temperature?
The higher the temperature the shorter the pasteurization time required
What does a piezometer measure?
Pressure
State the Poiseuille's law for a Newtonian fluid.
V = pi.R^4.deltaP/(8.nu.L)
State Hook's law.
F = -kx (k = spring constant, x = spring elongation, F = force)
What is the water activity of intermediate moisture foods?
0.6 - 0.85
What are the effects of drying on case hardening and crust formation?
Solutes move to surface, evaporation of water causes concentration of solutes at the surface level, high temp cause complex chemical and physical changes and the formation of a hard impermeable skin, aggregations of molecules are not easily disassociated on rehydration, minimized by flattening the concentration gradients, control rate of drying, crust is desirable breakfast cereals long bowl life, undesirable if rehydration necessary. IN sausages, they are drying from the inside out and the moisture removed from the surface is replaced by the moisture coming from inside the sausage. If the surface hardening occurs to fast, the inside moisture may be permanently trapped and bacteria will multiply spoiling the sausage
What are some examples of indirect-contact freezing system?
Plate Freezers: The most common type, where products (often packaged fish or meat) are placed between metal plates (vertical or horizontal) that are cooled internally by a refrigerant. Contact Belt/Contact Plate Freezers: Product is placed on a cold metal conveyor belt that moves through a freezer, allowing for continuous, efficient, and uniform freezing. Submerger (Immersion) Freezer: Packaged foods are passed through a bath of refrigerated brine, glycol, or calcium chloride solution, creating intense indirect contact for rapid freezing. Scraped Surface Heat Exchanger: Used for liquids or pastes, this involves a rotating blade within a cylinder that scrapes the frozen product off the inner surface.
What is the practical storage life (PSL) of frozen foods?
Practical storage life (PSL): defined as the duration of frozen-food storage when the product remains acceptable for human consumption or any defined purpose.
Engineers commonly use dimensionless numbers to aid in solving equations; which dimensionless numbers do the following 2-letter abbreviations represent when expressed in the subscript to a capital N: Sc, Re, Nu, Bi?
Sc=Schmidt; Re=Reynolds; Nu= Nusselt; Bi=Biot
What is non-Newtonian fluids?
Fluids that show a non-linear relationship between shear stress and shear rate. a. Shear-thinning or pseudoplastic: condensed milk, fruit purees, mayonnaise; b. Shear-thickening.
What are some ways to reduce non-uniform heating during microwave heating?
Rotating food with motorized platter, pre-heating and holding time after the microwave heating, adjusting power settings in microwave ovens
What is the drying method by contact with a heated surface of a revolving drum called?
Drum or roller drying
What equipment is needed for osmotic dehydration?
Osmotic dehydrator with vibrating basket (jacked vessel, basket, shaft, eccentric, spout) batch operation
In the manufacture of chocolate, what is the name of the process that impacts flavor & texture changes in the chocolate paste, through agitation?
Conching
What instrument is used for dough-mixer to measure torque?
Farinograph
The increase in kinetic energy of a flowing fluid is at the expense of what? a) pressure drop b) Reynolds number c) viscosity
a) pressure drop
what is the purpose of using a rotary retort for canned soup?
The rotation causes currents in the liquid, which causes more efficient heating during retort.
What are some of the factors that affect the dielectric properties of foods?
frequencies, food composition, moisture content, product temperature, physical state of water in the food, fat content, and product density
What is the name given to a mixture of flour and water that are used for manufacture of extruded pasta products ?
Alimentary pastes (do not accept batters)
what are the 2 main components of food that absorb far-IR energy?
water and organic compounds (such as proteins and starches)
A two-stage homogenizer uses a pressure of what through the first stage valve and what through the second stage valve?
2000-2500 psi 500 psi
Is fermentation considered chemical preservation?
No
What is the optimum moisture percentage for RTE breakfast cereal?
3-5%
What is osmotic dehydration?
The process of water removal by immersion of water containing cellular solid in concentrated aqueous solution of high osmotic pressure for a specified time and temperature
What are the different categories of food processing technologies?
Food preservation, separation, congregation
What is absolute humidity?
Mass of water/mass of dry air
What is the ratio of internal to external resistance?
Biot number
What is the purpose of corrugations or ripples?
Used to increase the surface area, causes turbulence which causes the boundary film of lower thickness on the solid surface, heat transfer coefficient is increased
Name 5 chelating agents used in the food industry.
EDTA, citric acid, malic acid, tartaric acid, oxalic acid, succinic acid, adenosine triphosphate, pyrophosphate, porphyrins, and proteins.
Starting with 1 atm, how are the following units related: atmosphere, inches of mercury, pascal, psi?
1 atm = 29.92 (~30) in Hg = 760 mm Hg = 101,325 Pa = 14.696 psi
Give three examples of classes of foods which are low acid.
Meats, seafood, vegetables (except tomatoes), some fruits.
What foods need to be processed by retorting or pressure cooking the product under anaerobic conditions?
Low acid, high pH foods.
What is the difference between dead-end filtration and cross-flow filtration (or tangential flow filtration)?
With dead-end, or conventional filtration, the feed flows perpendicular to the membrane and separation occurs by the force of gravity. Under cross flow filtration, the flow of the feed is parallel to the membrane and separation is controlled by pressure and flow rate.
The undesirable clarification of orange juice or tomato juice (precipitation of pulp) is caused by what enzymes?
Pectin methyl esterase or galacturonase
What is the difference between evaporating and drying?
Evaporation is used to concentrate solids to a certain degree while drying is used to achieve a level close to total dryness with only 2-3% of water
In extrusion, what are the sources of heat?
Heat from the temperature-elevating system; heat from shear force
How does Convection Heating work?
(canned liquid) the first heated portion of the liquid becomes lighter in density and rises thereby setting up circulation within the can. Coldest location at bottom of container.
What is the standard temperature and pressure (STP)?
0 degrees C at 1 bar pressure (10^5 Pa or 0.987 atm)
What is the equation for conduction and define each term?
Q=KA[ΔT/L] Q=the heat rate K = thermal conductivity L= thickness of the wall A = surface area of the wall ΔT = the difference in temperature between the 2 sides
What is Sensible Heat?
Sensible heat refers to the amount of heat added to or removed from a substance that results only in a change in temperature, it takes into consideration the mass of the material and heat capacity.
In cheese making, the "cheddar" process involves: A) adding lactic acid to milk; B) adding rennet; C) turning and piling the curds; D) chopping the curds and adding salt
C) turning and piling the curds
What are the four variables used when calculating the Reynolds number of a fluid?
D = pipe diameter, V = mean fluid velocity, ρ = mass density, μ = fluid viscosity.
In heat transfer, what do the Biot number and the Fourier number physically represent?
Biot: Ratio of internal resistance to heat transfer to external resistance (convection). Fourier: Ratio of heat transferred by conduction to the heat storage rate.
What is thermal death time?
TDT is the time at temperature T to reduce the number of microorganisms by a specific amount, varies from food to food.
The pitot tube, orifice meter, and venturi tube are all devices designed to measure what?
Flow rate (liquid transport)
Name three types of freezers.
air blast freezer, contact or plate freezer, spray or imersion freezer
The ratio of the sine of the angle of incidence of a ray of light on the surface separating two media to the sine of its angle of refraction is called:
Refractive index
What is a technique used to inject pickle simultaneously and automatically through a series of hollow needles, the shafts of which have numerous, evenly spaced holes along their lengths?
Multiple injection pumping (stitch)
What is the name given to any fluid at a temperature above its critical temperature-pressure value?
Supercritical fluid
What is the unit used to measure viscosity in fluids?
Pascal-seconds (Pa·s) or centipoise (cP)
What is the mechanism of moisture migration?
Diffusion ( moisture content difference), Capillary & Bulk flow (pressure difference), Heat is applied to the food and start with wet food and dry air and end with dry food and wet air
What is the primary substance used for caffeine extraction?
Supercritical carbon dioxide
How can we decrease the boiling temp of a well-defined liquid mixture without changing its composition, in order to prevent degradation of heat-sensitive ingredients?
Use vacuum evaporator; under vacuum, boiling temps will decrease
Why is calcium propionate used as an ingredient of soft rye bread?
Antifungal agent (preservative also accepted)
Name 2 types of retorts.
still (not agitating, vertical, horizontal, hydrostatic), agitating
What are some advantages of a scraped surface heat exchanger?
Process any pumpable product, adding surface area, low pressure drops, can process at high temps without burn-on
The rotary pump and the reciprocating pump are both types of what kind of pump?
Positive displacement pump
What is the cheapest thickener in the US and what is the most expensive?
Cheapest - unmodified corn starch Most Expensive - Agar
foods relatively high in fat are frozen prior to irradiation to: A.inactivate some foodborne illnesses,B. preserve the frozen food, C. minimize nutrient loss and flavor changes, or D. help drive oxygen out?
C. minimize nutrient loss and flavor changes
What is the effect of the thermal and physical properties of food on processing time for in-container sterilization?
The physical state may change during heat sterilization, ie/gel starch. Thermal and physical properties - solid food, thermal conductivity, Cp, density, ; liquid food, thermal conductivity, viscosity, density, Cp
What is the difference between traditional thermal processing and aseptic processing?
Traditional: food is packaged then sterilized, ex canning. aseptic: food is sterilized and packaged in a sterile container and is only practical for liquid or fluid products
Why do we dry food?
To decrease distribution costs, to prolong storage time, to concentrate flavors.
ESL dairy cow product means: A.estimated shelf life, B.extremely short-lived, or C.extended shelf life
C.extended shelf life
Food additives (define)
Chemical substances added to foods directly or indirectly, in known/regulated quantities for the purpose of assisting the processing/preservation/flavor/texture/appearance
Rate the following materials from lowest thermal conductivity value to highest: water, aluminum, stainless steel, glass, air, copper
Air, water, glass, stainless steel, aluminum, copper
What is incipient contaminant?
Contaminant found before thermal processing
What does Commercial Storage involve?
Pre-treatment of products during chilling process: - Solid foods - blast chilling - Direct immersion - into coolant medium - Chilling of liquid - indirect heat exchangers (plate and frame design) Temperature control always be within 1 C.
What is Heat Capacity?
Heat capacity is a measure of a material's ability to store heat
Describe the process of forming an hermetic seal.
The can end and body are interlocked during two rolling actions, first action curls the edge of the can end up and under the flange of the can body, and the second action roll flattens and tightens the seam
What dimensionless number describes the ratio of momentum diffusivity to thermal diffusivity in fluid flow?
Prandtl number.
Increases in ice crystal size within a frozen food as a result of migratory recrystallization can be minimized at a given storage temperature by minimizing what?
Temperature fluctuations
Nutrient retention is best ensured in quality food production using what three techniques?
Batch production; Minimize holding/cooking time; Minimize cooking temperature
Give the equation for determining loss tangent, also called dissipation factor.
Dielectric loss factor divided by dielectric constant
What are the four foods that currently cannot be processed using HPP?
Breads and baked goods, whole fruits and vegetables, marshmallow, whole eggs, high-fat foods, green leafy vegetables, carbonated beverages
Why might you want between 0.5 and 2% encapsulated water dispersed in a chocolate system?
The water (humectant) enables the chocolate to resist melting at ambient tropical temperatures.
Explain IR radiation.
It is transmitted as a wave and gets converted into heat when it impinges on the food surface
The mash obtained in the fermentation of soy to produce soy sauce is called
Miso
What unit operation separates particles based on size using a mesh?
Sieving
How many BTU's must be taken from a pound of water to change it from a pound of liquid (water) at 32?F to a pound of solid (ice) at 32?F?
144 BTU's
What are 4 applications that use spray drying?
Powdered cheese, cream powders, egg powers, milk products
why is HFCS used for sweetening of cold but not hot drinks?
Fructose is found either as pyranose or furanose; increasing the temp shifts the equilibrium toward the furanose form (which is less sweet)
What is the biggest factor in increasing thermal efficiency of continuous pasteurizers?
By using a larger size of the regeneration section
What is the common metric unit for force?
Force= Newton
With respect to quality, what do the following acronyms stand for? TQM, JIT, GMP, CIM, HACCP, AQL, SPC, PONC
TQM-Total Quality Management; JIT-Just In Time; GMP-Good Manufacturing Practices; CIM-Computer Integrated Management; HACCP-Hazard Analysis and Critical Control Points; AQL-Acceptable Quality Level; SPC-Statistical Process Control; PONC-Price Of Non-Conformance
In indirect heating, what is heat regeneration?
using sterilized product to heat sterilized product and thereby cooling the sterilized product
UHT is known as a method for pasteurization. What does UHT stand for?
Ultra High temperature
What is the dielectric constant?
a quantity measuring the ability of a substance to store electrical energy in an electrical field
Which rheological model best describes shear-thinning behavior of ketchup?
Power-law model.
Tofu is made of ______.
Soybean curd
What are the disadvantages of freeze drying?
Cost much more than conventional drying methods, certain products are damaged by freezing before drying, freeze dried products more rapidly pick up moisture, freeze dried products are very fragile, some freeze dried products bleach when store
What are the three phases of the freeze drying cycle?
Freezing, primary drying, secondary drying
What is Ultra High temperature/aseptic processing?
Process at very high temperature for very short time. Sterilize liquid before filling, sterilize containers, Fill food in containers in sterile environment
What is the log of 1?
0
Which of the following are the standard temperature and pressure conditions according to IUPAC? (a) 25 C at 1 atm (b) 25 C at 1 bar (c) 0 C at 1 atm (d) 0 C at 1 bar
(d) 0 C at 1 bar (current IUPAC definition, older definitions said 0 C at 1 atm
Multiple choice: which of the following is the strongest form of radiation: a. alpha, b. beta, c. gamma?
c. Gamma radiation
What is another name for industrial evaporation?
Boiling
What is conventional filtration?
Perpendicular flow causes a quick buildup of solids on membrane surface and reduces flux
What are the three types of fluid flow through a pipe and the Reynold's number that defines them?
Laminar (Re < 2100), transitional (2100 < Re < 4000), turbulent (Re > 4000)
What is the type of non-Newtonian fluid that exhibits reversible shear-thinning?
Thixotropic
What size particles is spray drying meant for?
Small particles
Which is the mildest form of food preservation?
Refrigeration
What is vapor recompression?
To increase the pressure and temperature of the vapor to be used again in evaporation
What is the frequency range of microwaves?
300 MHz to 300 GHz
Which of the following dehydration methods would you use to produce a very high quality, dried, intact food product, such as a dried strawberry? a. spray drying; b. drum drying; c. air convection drying; d. freeze drying
d. freeze drying
How many pounds are there in a kilogram?
2.2
What is the transformation of a gas into a liquid called?
Condensation
What is cryogenic freezing?
Freezing process by direct immersion of products in cryogenic liquids (liquefied gas with extremely low boiling points)
The recommended maximum temperature for dry food storage areas should not be greater than: a) 45°F (7.2°C); b) 50°F (10°C); c) 60°F (15.6°C); d) 70°F (21.1°C)
d) 70°F (21.1°C)
What does the term "STP" mean, and what are the values of the components?
Standard temperature and pressure: 14.7 psia or 760 mm Hg (or equivalent) and 0 °C.
What are the parameters that are controlled during post harvest preservation of fruits and vegetables?
Temperature and humidity
The equation which relates electrochemical cell potentials to the concentrations of the oxidation/reduction reactants, is called what?
The Nernst Equation
How does a Multiple-Effect Evaporator function?
Vapors produced by evaporation of water from the initial product in the first stage are fed into the steam chest of the second stage to provide further evaporation. 3 to 7 stages are common.
What are some disadvantages of a plate heat exchanger?
Limited to low viscosity products, re-gasketing costs can be high, fouling tendencies may exist for some products
Cryogenic freezing of fruits and vegetables generally refers to freezing at what temperature?
-70 F
What is humidity (absolute humidity)?
H= (mass water (kg))/(mass dry air (kg))
What is the difference between Reverse Osmosis (R.O) and Ultrafiltration (U.F)?
In both processes, the driving force for transport across the membrane is the pressure applied to the liquid feed. However, R.O is utilized to separate water from low-molecular weight solutes (i.e., salts, monosaccharides, volatile compounds), while allowing water and some salts with the smallest size to pass through. High pressure is needed to achieve this (4000-8000 kPa). UF limits only the largest (i.e., proteins, colloids) and smaller solutes are transported through, therefore lower pressure is needed.
Name two emulsifying salts used to make processed cheese.
Disodium phosphate, sodium citrate, sodium tartrate, sodium pyrophosphate, trisodium phosphate, sodium potassium tartrate
What does "c" stand for in E=mc²?
Speed of light
(Bonus) For fluids, flowing through a pipe. Name the four parameters included in the calculation of Reynolds number.
Viscosity, pipe diameter, velocity, density (Re: Dv(rho)/(nu))
a technology that will enable the use of aspartame in baked goods is:
Encapsulation
In cocoa processing, what does NARS stand for?
Nibs alkalizing roasting and sterilizing
which of the following does NOT generally have moisture loss as a mechanism of deterioration: A.fresh vegetables, B.RTE salads, C.Ambient packaged cakes, or D.potato chips?
D. potato chips
What is the name of the machine that destroys insect eggs in flour?
Entoleter
Cloud stability in products like tomato and orange juice is favored by which of the following? A) Inactivation of polygalacturonase B) Inactivation of PME C) Addition of PME
B) Inactivation of PME
What are the SI units of viscosity?
Pa-s
What is the process by which the passage of an electric current through a conductor produces heat?
Joule Heating/ Ohmic heating
Standard sieves in the U.S. (the Tyler series of sieves) are given a mesh number. What does the mesh number tell you about the characteristics of the sieve?
The mesh number is the number of openings per inch.
What is Hess's Law?
Enthaply is not dependent on the reaction pathway, just on initial and final conditions (State Function)
What is the function of the additive sodium silicoaluminate?
Maintains free-flowing properties
What is the purpose of co-current air flow in spray drying?
Drying air and particles move through the chamber in sampe direction, product temperatures of discharge from dryer are lower than the exhaust air temp, hence this is an ideal mode for drying heat sensitive products, when operating rotary atomizer air disperser creates a high degree of air rotation giving uniform temps throughout drying chamber
What property is described by Poiseuille's Law?
Viscosity/ pressure drop/ flow rate
Complete the term: First in
First out, aka FIFO
What heat transfer mechanism dominates during retort sterilization of canned foods?
Conduction (for solid foods) or convection (for liquids).
What term is a measure of ability to store electrical energy?
Dielectric constant
Name one acceptable sanitizer for use on food equipment.
sodium hypochlorite, iodophors, quaternary ammonium compounds
What is the relationship between ERH and water activity?
Aw = ERH/100
What are some of the disadvantages of a liquid-in-glass thermometer?
Large sensing element, not possible for continuous or automatic readout, long time constant
What is the point on the phase diagram where ice crystals and sugar crystals form?
It happens at the eutectic temperature
Name four types of freezing processes used in the food industry.
Fluidized Bed (or Individually Quick Frozen-IQF); Plate; Immersion; Blast Freezing (Convective Freezing); Cold-Room freezing (stagnant air freezing); Swept-surface heat exchanger (as with ice-cream)
At which frequency, 915 or 2450 MHz will the penetration depth be larger?
915 MHz
Give four pulse waveforms used in Pulsed Electric Field.
Exponentially decaying, square wave, bipolar, oscillatory, instant charge reversal pulse
What is lethality?
Measure of the microbial kill power at reference temperature
Prior to refrigeration, what was the primary method used for food preservation?
Fermentation
What is the effect of temperature on D Value?
Increasing the temperature will shorten the D value
What are the two specific frequencies reserved by the FCC for industrial/home food microwave heating?
2450 MHz and 915 MHz
Why are fruits or vegetables often heated prior to maceration for juice production?
To speed up the process or to infuse flavors prior to maceration, to increase extract yield and to inactivate the enzymes
What is a thermal center?
The slowest point of heating in a can
What are the requirements for optimal evaporation?
Rapid rate of heat transfer Low temperature operation through the use of vacuum Efficient vapor-liquid separation Efficient energy use and recovery.
What corn derivative is one of the most commonly used sweeteners in the food industry?
High Fructose Corn Syrup (HFCS)
Shear modulus is represented by which letter?
G
What is the general name given to liquefied gases of extremely low boiling point, such as liquid nitrogen at -196 C and liquid carbon dioxide at -79 C, which are commonly used in immersion freezing of foods?
Cryogenic fluids
What is the psychometric chart?
A chart that relates all of the external conditions to each other. If you know two conditions you can determine the other two
What law describes the theoretical spectral distribution for the emissive power of a black body?
Planck law
What are the types of heat sterilization?
In-container sterilization , Ultra high temperature processes
What is the name given to heat transfer that occurs primarily by mass movement of molecules?
Convective heat transfer.
What are the different processes that can be used depending on the raw material and end product?
Raw End Pro Liquid->liquid Concentration, thermal pasteurization Liquid->Solid Concentration, thermal pasteurization, drying solid->Solid Drying, extrusion, thermal pasteurization
What are some of the internal conditions that affect drying?
Properties of food, thermo conductivity, density, porosity, aw, sorption isotherms
What is done when force acts through a certain distance?
Work
What is the distance from the surface of the food material at which the incident microwave power is reduced to 1/e of its value at the surface of the product?
Penetration depth
What are cabinet/tray/compartment dryers?
Thin layer of product, air moves either cross-flow or through flow, cheap to build and maintain, mainly for fruits and vegetable, uneven drying, more rapid drying where trays enter, good for pilot testing
What are the three steps in retorting?
Preheating, sterilization, cooling
Explain Heat Treatment.
Process of inactivating pathogens and spoilage microorganisms and enzymes, i.e. blanching and pasteurizing
What factors contribute to the magnitude of the thermal process?
- Product pH or acidity - Heating and cooling characteristics - Size of container - Heating and cooling medium - Time/temperature relationship - Product composition
If the viscosity of a liquid inreases, what happens to the Reynolds number?
Decreases
What is freeze concentration?
Freeze concentration is fundamentally a crystallization and separation process. It involves partial freezing of product and removal of ice crystals.
Name 5 unit operations in the food industry.
Material handling, cleaning foods, cleaning equipment, separating, disintegrating, pumping, heat exchange, cooling, evaporating, drying, forming, controlling, packaging
What are the 4 purposes of evaporation industry?
Reduce the volume of a product Preconcentrate a liquid Increase solid content in food Reduce the microbial load
What are the steps in freeze concentration?
Step 1: It all starts from the ice crystal point of view by removing heat from the solution, Typically done by using a scraped surface heat exchanger ( inside scraped by a rotating shaft while outside cooled by refrigerant). Tiny ice crystals are formed at this cold surface. Step 2: Once crystals formed in SSHE, enter a mixed vessel (recrystallizer). Most of the small crystals will melt allowing larger ones to grow. Why? Bc melting required the addition of heat and changing from solid to liquid. Known as ripening and forms the heart of separate nucleation and growth process. Step 3: Since we want a continuous flow of small crystals to the recrystallizer, we must extract liquid from a filter in the recrystallizer and circulate that over the SSHE (scraped surface heat exchanger). Step 4: Once sufficient crystals in recrystallizer can start separation from concentrated liquid, This is done with wash column, where crystals sep from liquid, washed to remove and remaining concentrate, melted and discharged as pure water, Concentrate returned to recrystallizer. Step 5: Fresh feed replaced the water that is removed from the system. The feed is mixed with the recirculation stream feeding the SSHE. Since the feed is replacing the water that is removed from the system the concentration of the soluble solids in the system will increase. Step 6: Next add a way to remove the concentrated product, discharged from the liquid recirculation line after filtration. Since the concentrate contains all of the soluble solids originally in the feed the system will now remain constant
What does a headspace scavenger such as ascorbate do in a container?
Reduce headspace [O2]
What are the 3 types of still retorts?
vertical, horizontal, and hydrostatic
Certified food colorants can be divided into 2 types. What are they?
Dyes (water soluble) and lakes (water and oil soluble)
What effect would the addition of sodium bicarbonate have to chocolate?
Smoother, less acid and less bitter chocolate flavor, darker color, and improved solubility (elevated pH enhances sugar-amino browning reactions and polymerization of flavonoids).
What is carboxy-methyl cellulose often used for in foods?
Thickener
Given type of heat exchange, say whether there is aroma retention or not: steam injection/infusion, plate heat exchanger, tubular heat exchanger, scraped surface heat exchanger
All yes (retain aroma) except steam injection/infusion
What is non-newtonian fluid?
As you increase the shear rate the viscosity decreases, liquid but flowing like a solid
What unit operations take place during evaporation?
Thus evaporator operations basically involve energy transfer (heat for vaporization and condensation), mass transfer (moisture removal), fluid flow (feed and vapor flow)
What are the units of a Reynold's number?
It has no units/ it is dimensionless
Give the time and temperature for HTST pasteurization.
72°C (161 °F) for 15 seconds
What are the effects of drying on rehydration?
A comprehensive quality parameter (good rehydration, good drying process) a good indication as to whether the various processing conditions were correctly applied. Biomatrix changes during drying: loss of the elasticity of cell walls, a reduced swelling ability of starch gel, loss of the osmotic properties of cell walls, destruction of membranes and structural proteins. Rehydration is a measure for the severity of the destruction caused by drying
A Newton is defined as which of the following? (a) The work done when a point of application of 1kgm/s2 is displaced a distance of 1m (b) The force that gives a mass of 1 kg an acceleration of 1m/s2 (c) The power that give rise to the production of energy at the rate of 1 m2kg/s2 (d) None of the above
(b) The force that gives a mass of 1 kg an acceleration of 1m/s2
For what purpose is sodium hypochlorite used in the food industry?
It is a sanitizer
Explain Moisture Removal.
The removal of water from food to lower its moisture content to inhibit food spoilage. Done by adding solutes, like sugar and salt
What is the most advantageous type of IR and why?
Far-IR, most food components absorb radiative energy in this region
What is the difference between latent heat and sensible heat?
Sensible heat-heat readily perceived by the sense of touch which produces a temperature change as heat is added or removed. Latent heat-quantity of heat required to change the state or condition under which a substance exists, without a change in temperature.
What are some of the factors that affect osmotic dehydration?
Molecular species, concentration of osmotic solution, temperature, time, pressure(vacuum), size and shape of product
What is wet bulb temperature?
Temperature of air measured by a thermometer whose bulb is covered by a wet cloth
What is the primary purpose of Processing Food?
To preserve food and create a specific desirable food product
Energy is lost when the flow of a liquid is altered or distorted, such as when there is a bend in a pipe. The energy loss at fittings is proportional to what property of the fluid flow?
The velocity head of the liquid (just velocity is acceptable)
What is the basis for preservation by dessication?
water removal-lowers water activity
What is the purpose of pasteurization in high acid foods?
To kill spoilage micro-organisms like wild yeasts, and to inactivate enzymes
Name a fermented milk that contains alcohol.
Kefir or koumiss
Which unit of electricity measures the number of electrons moving through a wire?
Ampere
A succession of grinding stages is used to reduce grain to flour. What device is used?
Roller mills
During the process of drying what is the point after which the drying rate starts to decrease?
Critical point or critical moisture content.
What is the rapid formation, growth and subsequent collapse of microscopic gas bubbles during the ultrasound process called?
Cavitation
What is the multiple effect design?
Where vapor from the previous evaporator is used to evaporated more water from the concentrate in the next evaporator. utilizes the latent heat of the vapor
What disease is currently devastating the Florida Citrus Industry?
Citrus Greening or HLB
What are the four main requirements in an aseptic system?
Aseptic processing and equipment, aseptic packaging and sealing hermetically in an aseptic environment, monitoring, and proper handling of finished products
The FDA requires the irradiation logo to appear on irradiated foods. What wording is required on the package of irradiated foods?
The phrase "treated with radiation" or "treated by irradiation"
Which type of heat transfer involves the movement of a fluid (liquid or gas) over a surface, such as in a blast freezer?
Convection
What are the different types of drum dryers?
Single drum, double drum (2 drums revolve toward each other @top), twin drum (2 drums rotates away from each other), Vacuum (heat sensitive materials, expensive), perforated/suction (hot air, several drums can be linked)
What is the difference between thermoplastics materials and thermosets materials?
Thermoplastics are uncrosslinked polymers with amorphous or semi-crystalline structures; thermosets are crosslinked polymers.
What is Z value?
Z-value is the temperature increase required to reduce the D-value by a factor of 10 (one log cycle)
What are some two reasons for roasting cocoa beans for chocolate making?
Flavor development, separate outer husk from inner bean (makes cracking and winnowing much easier), virtually sterilizes cocoa been (prevent growth of bacteria/fungi/molds), even color and texture
What are some characteristics of microwaves?
Travels at speed of light, non-ionizing form of radiations, can be focused into beams, can transit through hollow tubes, may be absorbed or reflected by the material depending on its dielectric properties, may also transmit through materials without any absorption (includes glas, ceramics, some thermoplastic plastics)
What is the D-value if the time required reducing the population by a factor of 10 is 2 minutes?
2 min
Why do we determine F values?
This allows us to be able to compare the different processes
What is specific gravity?
Ratio of density of a substance to the density of water at a given temperature
What form of heat transfer is used in solid canned foods?
Conduction
What is the simple term for conversion of raw materials or ingredients into a consumer food product?
Food Processing & Engineering
What are the steps of membrane separation?
Feed enter, permeate penetrates the membrane, retentate is what doesn't pass through) reject, concentrate, residue)
2 piece cans for low acid foods are made in what? a. impact exit b. draw + iron c. draw redraw(?) d. welding
c. draw-redraw
The viscosity of an egg white decreases with an increase in shear force. What is the name of this type of viscosity?
Pseudoplastic or shear thinning
What process is commonly used to produce condensed milk?
Vacuum evaporation
What is Specific Heat Ratio?
Ratio of the heat capacity of a substance to that of water; dimensionless
Why add K(ALSO4)2 to a pickle mix?
To keep the pickles firm (the AL3+acts as a cross linker between pectin polymers)
State the steady state mass balance equation.
Mass in = mass out (steady state: mass acumulation = 0)
What is the most common type of thermocouple used in food processing?
Type T (Copper-Constantan) is the most common because of its high accuracy at the temperatures used for refrigeration and canning.
A unit of lethality can be expressed as which of the following? (a) The time needed to reduce the bacterial load by a 1 log cycle reduction; (b) The heat kill equivalent to 1 min. at 121ºC against an organism with an 18º z-valve; (c) The number of organisms destroyed during a thermal process; (d) All of the above
(b) The heat kill equivalent to 1 min. at 121ºC against an organism with an 18º z-valve
What is a psychrometric chart?
A psychrometric chart is a graphical representation of the psychrometric processes of air. Psychrometric processes include physical and thermodynamic properties such as dry bulb temperature, wet bulb temperature, humidity, enthalpy, and air density.
What metric prefix is used to denote a value of one billion?
Giga-
What is osmotic pressure?
Minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in water by osmosis. Excess pressure needed to reach the state of equilibrium between two systems
In thermoprocessing, what is the difference between ""sterility" and "commercial sterility"?
"Commerical sterility" means the probability of spores and cells surviving is low but not absolute
Which of these is a fermented product? Surimi, tofu, miso
miso
Name 4 applications for Infrared in food processing.
Drying, heating, frying, roasting, baking, thawing, surface pasteurization
What is the purpose of thermal processing?
Ensure food safety and extend the shelf life of food (by killing bacteria)
Of the three radiate particles, alpha, beta and gamma, which two are commonly used in food irradiation?
Beta and Gamma
What two factors largely determine the degree of thermal processing required?
pH of foods and rate of heat penetration into canned products
What is the inverse of attenuation factor?
Penetration depth
In spoilage of thermally processed canned foods, what is meant by the term flat-sour growth?
Spoilage without gas production
What is equilibrium moisture?
Xe, moisture of a food when it reaches equilibrium with the air. When it reaches this it cannot be dried anymore, free moisture= moisture - equilibrium moisture
What term is defined as the number of degrees required for a specific thermal death time curve to pass through one log cycle?
Z-value
microwave heating is accomplished by _______.
Molecular friction
What is an ideal surface which absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence, and emits the maximum possible thermal radiation at a given temperature?
Blackbody
What is a decanter centrifuge?
for clarification (solid liquid separation) and dewatering, can handle higher solid content than high speed disc, applications(fish-meal, rendering, olive oil, juice, chemical slurries, waste water)
What is the name of the time period needed for a retort to reach processing temperature?
Come-up time
Name the equation that relates electrochemical cell potential to redox states.
Nernst equation
classify the following as either endothermic or exothermic: melting, condensation, evaporation, boiling, freezing, crystallization
Melting=endo; condensation=exo; evaporation= endo; boiling= endo; freezing= exo; crystallization= exo
What pH distinguishes the difference between low acid and high acid foods?
pH 4.6
What are instantized powders?
Dissolves right away - large wettable surface area, sinkability(must not float on surface, agglomeration by rewetting) dispersibility of solubility, resistance to sedimentation. Want to make small lumps. Production process: Moist air + spray dried powder (rewetting and agglometation) → redrying in spray dryer/ fluidizer bed →sieving → packaging
Gear, rotary, and reciprocating piston pumps represent a specific class of pumps. What is this class?
Positive displacement
What is dew point temperature?
Temp at which air becomes saturated with moisture (RH=100%) and any further cooling results in condensation of water form air
What is the name of the process where a foods temperature goes from 32deg F to 25degF in 30 minutes?
Quick freezing
What does a gauge tell you?
A gauge can only tell you the difference between the pressure it is measuring and the atmospheric pressure.
What law is represented by F = kQ1Q2/d2, where Q1 and Q2 are the magnitude of the charges on two particles, d is the distance between their centers, and k is a constant?
Coloumb's law
What term is defined as the number of minutes at a specified temperature required to destroy a specified number of organisms having a specific z valve?
F value
During freeze drying, water is removed by a change in state. What is this process called?
Sublimation
Name two types of flow in pipes based on Reynold's number.
Laminar and Turbulent
What is the name given to the temperature scale that expresses temperature as degrees Farenheit above absolute zero?
The Rankine scale
Which Serbian-American inventor born in present-day Croatia, also an electrical engineer, mechanical engineer, and a futurist is attributed with the invention of alternating current and also has a unit of magnetism named after him?
Nikola Tesla
What are the advantages and disadvantages of tubular membrane modules?
Advantages: Feed stream with particulate matter can be put through membrane, Easy to clean Disadvantages: High energy consumption, High hold up volume
Does a smaller or larger electrode gap result in faster heating of the product?
smaller electrode gap
What is the property of a substance such as a liquid or dough that is measured by its resistance to flow?
Viscosity
Convection, conduction, and radiation are terms which describe what?
Types of heat transfer
What is the minimum pH of low-acid food?
4.6
What dimensionless number describes the ratio of momentum diffusivity to thermal diffusivity?
Prandtl number
Give the time and temperature for UHT pasteurization.
135-150°C (275-302°F) for 2-3 seconds
What are some of the advantages and disadvantages of radio frequency heating?
advatanges: longer wavelength, deeper penetration depth, shorter treatment time, less equipment space requirement, volumetric heating; being a continuous process disadvantages: non-uniform heating,
What is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%?
Dew-point
In what year was there a patent registered for use of a commercial refrigeration process for fish?
1842
What is the derived SI unit defined by the power that gives rise to the production of energy at the rate of one joule per second?
Watt
Why is flour added to confectionary frosting?
As a flow agent and anti-caking agent
What are the limitations of freeze concentration?
High cost, Difficulty in separation of ice from solid, Low upper limit on concentration, Has no effect on enzymes and microbes
Give the thermal process temperature for pumpkin packed in 50 gallon drums.
280-300F
In extrusion, most of the energy for melting the polymer resin comes from heat supplied by the extruder barrel.
False
How are the following enzymes or biochemical reactions used by the food industry? a. acetaldehyde reduction by yeast; b. invertase; c. production of carbon dioxide by Propionibacterium; d. pectinases in the beverage industry
a. acetaldehyde reduction makes ethanol; b. invertase makes liquid-filled candies and invert sugar; c. Probionibacterium is used in the production of Swiss cheese; d. pectinases are used in the clarification of juices
What is Ohm's Law and what is Power Equation?
V=IR and P=VI or I^2.R
What is the microorganism used to make miso and sake?
Aspergillus orzae
Name the only fruit or vegetable that is never sold frozen, canned, processed, cooked or in any other from except fresh.
Lettuce
Some food products such as salt, dehydrated vegetable and fruit powders, soup and sauce powders and baking powder tend to cake or harden. This can be avoided by anticaking agents. Name two.
Na-, K-, Ca-hexacyanoferrate, Ca-silicate, tricalcium phosphate, Mg-silicate, Mg-carbonate
What is the term for electromagnetic radiation generated by the thermal motion of charged particles in matter?
Thermal radiation
What is the range of refrigerated temperature?
40°F (4°C) or below; the freezer at 0°F (-18°C).
An exoenzyme that catalyzes hydrolysis of maltose units from the non-reducing end of starch is what?
B-amylase
What are the different types of membrane materials available?
Polymers most common, inorganic more stable. Synthetic membranes : PVC. Polymeric membranes: widely used for UF, wide tolerance to pH temp and chlorine. Ceramic membranes: made from mineral materials such as glass aluminum oxide, and zirconium oxide, expensive and can be brittle, mainly for MF. Glass membranes. Metallic membranes: ability to withstand extreme chemical and thermal stress. Zeolite membranes: a solid with lots of tiny holes. Can have different selectivity, long term stability at high temp resistance to harsh environments and high pressure drops. Inertness to microbial degradation and easy cleanability and catalytic activation
What are some disadvantages of a scraped surface heat exchanger?
High cost per units area, high operating costs, large floor space requirement vs other heat exchangers, disintegration of fragile particles
What would be acceleration of a 2 kg mass when 60 N force is applied?
Accl: 30 m/s2
How does a rotary sterilizer work?
Cylindrical pressure vessel with helical track an inner wall, cans rotated through different pressure zones
What unit operation is used to destroy pathogenic microorganisms and extend the shelf life of milk by heating it to a specific temperature for a set time?
Pasteurization
What does the c stand for in the equation E = mc^2?
The speed of light (~3 x 10^8 m/s)
What are the SI units for work, pressure, and energy?
Watts, pascals, joules
Tempeh is a fermented product from __________
Soybeans
True or false? Milk homogenization slows creaming by changing oil droplets radius
True
which of these methods will remove metal ions: A.microfiltration, B.ultrafiltration, C.reverse osmosis, or D.nanofiltration?
C. reverse osmosis
What is freeze drying?
Process of removing water from a product by sublimation and desorption.
Explain the difference between conduction, convection, and radiation heat transfer in food processing.
Conduction: Heat transfer through direct contact (solid foods). Convection: Heat transfer via fluid motion (liquids/gases). Radiation: Energy transfer via electromagnetic waves (microwave or infrared heating).
How many pecks are in a bushel? 2, 4, 8, 16
b. 4
What is open production?
A business buys a commodity from a producer at a market price determined at the time of purchase.
How does a continuous retort work?
Load the cans, then heat container with steam, allow to cook food for specified time, then cool by filling retort with water, then emptying the retort
In cheese making, what terms describe the solid mass and the liquid phases?
solid; curd; liquid:whey
The single most important phase of a sterile canning operation is what?
Retorting
Which dehydration process is used to obtain dry foods with minimal changes in their shape and ease of re-hydration?
Vacuum Freeze-drying
Explain thixotropic and pseudoplastic.
Thixotropy is the property of certain fluids and gels of becoming thinner when a constant force is applied. A pseudoplastic fluid is a fluid that increases viscosity as force is applied. The main difference is that viscosity of thixotropic fluids decreases upon applying a force whereas the viscosity of pseudoplastic fluids increases upon applying a force.
How does elevation effect boiling point?
As altitude increases the air pressure (external pressure) decreases, therefore at higher elevation the air pressure is less so the boiling point lowers. This is important in the food industry because if you want to minimize quality degradation then evaporation should take place at higher elevations where it doesn't have to reach as high of a temperature to achieve the same effect.
What is a unit operation?
a basic step in operation
Briefly describe the still retort process
Cans are loaded into the vessel, steam is injected into the vessel, fan circulates steam for uniformity, vent valve (cold air goes out), temperature and pressure increase to desired temp then vent valve closes, temperature is maintained for desired time (processing time), then precooling begins where the pressure is maintained while slowly cooling the cans, circulating pump with cold water moves into the vessel and gradually decreases the temperature, the drain opens to drain water, and once the cans are cooled and the pressure decreases, the cans can be removed
Materials which exhibit a direct proportionality between shearing stress and rate of shear are known as what type of fluids?
Newtonian Fluids
Can things be added to foods after sterilization?
Yes, Enzymes and probiotics with low hear sensitivity can be added to food after sterilization
What types of evaporators are used in the food industry?
Short tube Long tube (rising and Falling film) Forced-circulation evaporator Wiped film/agitated thin-film evaporator Plate evaporator: rising/falling film Centrifugal/conical evaporator.
What are the four phases of Refrigerated storage?
Commercial storage Transport storage Retail storage Home storage.
Two general categories of freezing methods used in commercial food processing are. Give examples.
Direct (air blast, immersion); Indirect (plate, scraped surface).
The food drug and cosmetic act contains guidelines requiring what foods to require lot coding?
Low acid canned foods, acidified foods, bottled drinking water, infant formula, bottled water
Name two of the three properties of a saturated steam that are listed in a steam table.
Specific volume, enthalpy, or entropy
What are the different types of freeze concentration units?
Ice Crystallization (Direct contact freezers, Indirect-contact freezers) and Separation Devices (Mechanical press, Centrifugal, Wash column)
What are the key difference between Pasteurization and heat sterilization?
Pasteurization: Mild heat treatment, Few week shelf life, Microbial and enzyme reduced, Insignificant nutrient and sensory loss, For liquid and canned foods Heat Sterilization: rigorous treatment, 6 or more month self-life, microbes and enzymes destroyed, substantial nutrient and sensory loss, mainly for canned foods
What are some of the applications of osmotic dehydration?
Dried fruits, (sucrose syrup, then air drying)
What four ingredients are necessary for making soy sauce?
Soybeans, wheat, salt, water.
What is the classification of fluid flow that has low velocities, no lateral mixing and moves in parallel layers?
Laminar
How are processed cheeses made?
Processed cheese are made either with the trimmings that are left over from the manufacture of other cheeses, or from dried milk powder
Name three types of retorts.
Still, agitating, continuous , discontinuous, still with overpressure
Describe one way nanoparticles are used in food processing.
Nanocapsules to improve the availability of neutraceuticals and/or flavors. Nanotubes and particles as gelation and viscosifying agents. Particles that bind and remove chemicals and pathogens.
What is supercooling?
The difference in temperature between the melting point and the temperature below the melting point in which the material remains liquid.
Who developed the equations to predict falling rate drying?
Sherwood
What are the advantages of spray drying?
Huge capacity(15000lb/hr), cost of maintenance low, purity of product maintained since particles do not contact with surface of equipment until dried, simple operation and cleaning condition contributes to low labor cost, low bulk density of product can be obtained, particle size is very small 10-500 um
What is the amount of energy required to raise the temperature of 1 gram of water from 14.5°C to 15.5°C?
1 Calorie/ 4.184 J
Why is quality of food better in retort pouches than in conventional cans?
Thinner profile means the less time to reach sterilizing treatment at center of pouch, saves money and time
Explain how Raoult's Law is applied in food processing.
Lowering of water activity when adding solutes to water; boiling point elevation or freezing point depression
What effect does the type, size and shape of the container have on processing time?
smaller container = greater heat transfer, effects conduction and convection - tall cylinder promote convection currents, faster transfer metal containers compared to glass or plastic
What are the two measures of dispersion?
Range and standard deviation
What does the Kelvin scale measure?
Temperature
What happens in the secondary drying phase?
Removal of non-freezable water(sorbed or bound water) via evap, temp limit ↑0C, process done to lower water activity
Define thermisation aka thermization wrt milk processing.
sub-pasteurization heat treatment applied to raw milk, typically in the range 62-65 deg. C for 10-20 sec that isn't intended to destroy any pathogens of concern. It's used to extend the storage life of raw milk prior to normal pasteurization by controlling psychotrophic bacteria early on.
What is the name of the concept which involves the usage of multiple barriers in order to prevent spoilage of foods?
Hurdle Concept
Are foods with a 3.7 to 4.5 pH classified as acid foods or high acid foods?
Acid foods
The unit used to measure an absorbed dozes of ionizing radiation is the “RAD”. What does “RAD” stand for?
Radiation absorbed dose
What are the advantages of non thermal processing over thermal processing?
Prevention of thermal off flavors, better flavor, better nutrient retention
What is the common unit of mass in the English system?
Pound
How does sugar syrup prevent browning of fruit?
Minimizes contact with atmospheric oxygen
What does a sling psychrometer do?
It measures the dry-bulb and wet-bulb temperatures independently. You then use a psychrometric chart or formula to calculate the relative humidity.
What is the winterization process for an oil?
Cooling the oil and filtering of the solids formed so that long chained saturated fats do not crystallize at low temperatures.
What are the units for absolute humidity?
Grams of water vapor per cubic meter volume of air
Give 4 reasons why compounds are micro-encapsulated.
Stability against oxidation, bioavailability, stability, resistant to pH, protect reactive substances from the environment, controlled/delayed release of compounds
This substance is formed from gliadins, glutenins and glycolipids when water is mixed with wheat flour.
Gluten
Name the 4 layers of a tin can.
Steel, tin, iron alloy, tin, enamel
What is the common term for the rapid removal of water vapor molecules from the frozen surface of a food by cold dry air through sublimation?
Freezer burn
What is the typical width of the pulse used in pulsed electric field processing?
1-10 microseconds
Which has a higher thermal conductivity - ice at 32 F or water at 32 F?
Ice (thermal conductivity of 1.28 BTU/(hr-ft-degrees F) compared to 0.314 for water).
Name four commercial types of thermal processing.
Steam Retorting, Pasteurization (HTST, UHT), Aseptic, Hot Fill, Frying, Flaming, Baking, Dry Oven...
What does the term “retort processing” refer to?
Commercial sterilization of low-acid canned foods using pressurized steam or water at ≥121°C.
What are the 2 parameters describing supercritical fluid?
Temperature and pressure
What is microfiltration?
Particles retained 0.02 - 10 mm, Pressure 1-50 psig, Bacteria, fat globules (suspended particles) rejected, Applications: dairy (milk - removal of bacterial and spores, fractionation of proteins), egg (remove bacteria) juice (clarification) Beer (recover yeast)
What is the name of the viscous liquid in which legumes have been cooked?
It's called aquafaba
What does ultraviolet light do to fat oxidation?
It accelerates fat oxidation
Give 3 ways to produce ethylene gas.
There are three main ways to produce ethylene: 1) gas from a cylinder, 2) catalytic generator, and 3) ethephon
What term describes the processing of a product, intended for room temperature storage, with the goal of preventing the growth of spoilage and pathogenic bacteria (although spores may be present)?
Commercial sterility
What do we call the process of converting vegetable oil to solid shortening?
Hydrogenation
What are the 8 key elements in an aseptic processing system?
The product, flow control (pumps), deaerator (optional), product heating, hold tube, product cooling, surge tank, filler for packaging
An electromagnetic wave w/ 10^10 cycle/sec is what type of wave?
Microwave
What are the 4 parameters for the processing of fluids flowing through a pipe?
Pipe diameter, viscosity, velocity, and density of fluids
What is the SI unit for power and what are the respective dimensions?
Watts, joules per second
What are the principles of osmotic dehydration?
Three types of counter-current mass transfer (water outflow: product to solution, solute transfer: solution to product, leaching out of products own solutes: sugars, organic acids, minerals, vitamins)
Tofu is a fermented product. True or False.
False
What are some of the disadvantages of frozen foods?
Thermal abuse during transportation/storage (warming or freezing product), ice crystal formation (affects food quality), freeze burn/ice crystal formation breaks down cells
A ribbon blender is preferred over a propeller-type agitator when mixing which types of ingredients?
low speed= cake dough mixing; high speed= dissolving solid ingredients into a liquid component.
what are 3 common units for expressing pressure from either the metric or English system?
kPa, Pa, torr, atm, psi, mmHg
What is oil winterization and why do we do it?
Winterization is done to remove fats which would crystallize at refrigeration temperatures. It is done by holding the oil at low temperatures (5 C) until advanced crystallization takes place, after which the solids are filtered out
Explain Blanching.
Process used to inactivate enzymes and set color
What factors of heat penetration effect sterilization time?
Type of product, size of container, agitation of container, temperature of retort, type of container
Name the four basic components of a mechanical refrigeration system.
Compressor, condenser, evaporator, expansion valve
Name two limitations to using intermediate moisture foods.
Lipid oxidation, enzymatic and non-enzymatic deterioration.
Explain the steps of freeze drying.
Lyophilization, freezes food then puts it through a vacuum, this evaporates solid frozen food, sublimation dries the food.
What is the general term that describes a device used to measure the force required to move a plunger a fixed distance through a food material?
Penetrometer
name 3 factors that affect the stability of an emulsion according to Stoke's Law.
Particle radius, particle density, fluid viscosity, fluid density, standard gravity
What are the minimum times and temperatures for LTLT and HTST pasteurization of milk?
LTLT – 145 degF (63 deg C), 30 minutes HTST – 161 deg F (71.7 deg C) 15 seconds
When preparing hot chocolate, it is common to observe:
A scum on the surface of the heated product.
what is the residue left after refining sugar?
Molasses
What is the SI unit of force?
Newton
What are the factors that affect the selectivity of membrane separation?
Size, shape, electrostatic charge, diffusivity, physiochemical interactions, volatility, polarity/solubility
What are the units for the following: pressure, force, and energy?
Pressure: pascal, force: newton, energy: joule
What term is used when there is a percent change in length of material before pulling?
Strain or elongation
What is the rate of doing work called? It has units of watts.
Power
What does cGMP stand for?
Current Good Manufacturing Practices
What are 4 limitations of IR heating?
IR radiation has limited penetration power, penetrative radiation energy does not make significant contribution to internal heating (need to combine IR with other heating methods for best result), maily efficient for solid products only, risks of infrared energy hazard to eyes and skin
What are the 3 effects of high temperature on whey protein?
Denaturation, coagulation, cooked flavor
What are 5 methods of freezing?
Plate/contact, still air/cold room/sharp, blast air, IQF/Fluidized bed, immersion/spray, cryogenic, sharp, rotary, spiral, band
What is the fish most commonly used for making Surimi?
Alaskan Pollock
Name 5 examples of unit operations.
Evaporator, storage tanks, filler, shipping, peeler/dicer, washing, mill, pasteurizer, grinding, extraction, drying
What is the term used to describe the quantity of heat that is gained or lost by a unit weight of product to accomplish a desired change in temperature without a change in state?
Sensible heat
What is the definition of mesh size?
Openings per square inch.
Bushel is a unit traditionally used to measure what?
Grains
True or False. The coldpack canning method requires less heat than the hotpack method.
False
Definition of Reynolds number
The ratio of inertial forces to the viscous forces
Give 3 types of natural and 3 synthetic surfactants in foods.
Natural - saponins, lecithin, lipoproteins, gums; synthetic - mono and diglycerides, sorbitan monostearate (SPANs) and polysorbates (TWEENs)
Give two methods by which aseptic packages are commercially sterilized.
H2O2 rinse, steam, dry heat.
What are the two types of steam?
Saturated and superheated
What is the glass transition temperature?
when an amorphous food polymer is heated the temperature at which it changes from a glass to the rubbery state form is called the glass transition temperature Tg, second order transition
Thermal processing relies on understanding heat resistance. Define z-value and F-value.
z-value is the temperature change required to change the D-value by a factor of 10. F-value is the total time required at a specific reference temperature to achieve a specific level of microbial destruction (lethality).
What is the relationship between dielectric loss factor and penetration depth?
as dielectric loss factor increase, penetration depth decreases
Why is calcium added to tofu during production?
Calcium Sulfate (CaSO4) is a salt coagulant that works by ionic cross-linking of proteins.
What is the purpose of blanching?
To destroy degradative enzyme
What is involved in Transport storage?
Based on mechanical refrigeration units, Eutectic plates, spray or direct expansion of liquid nitrogen.
In thermal processing, what is the symbol used for the temperature response parameter for cooling curve? It is the time required for the straight line fitted to the log-linear portion of a cooling curve to pass through a one log cycle. It is also the negative reciprocal of the slope of the cooling curve.
F sub c
What is vacuum pressure?
Atmospheric pressure - absolute pressure
Falling film is a type of which equipment in food processing?
Evaporators
During typical food heating, what is the starting size of gap that microwaves cannot pass through?
0.122 m to 0.328 m
What type of rays are used principally in irradiating foods?
Gamma rays, beta rays.
How do soluble solids affect the boiling point and freezing point of a solution?
When a solute (soluble solid) is added it lowers the vapor pressure above the solution therefore causing boiling point elevation because more vapor has to be created to overcome the atmospheric pressure and it also causes freezing point depression
What cooking method uses dry heat and radiant energy?
Broiling
What is the spectrum range for thermal radiation?
0.1 um to 1000 um (1 mm)
Explain the principle of extrusion cooking and name two key variables that influence product expansion.
Extrusion combines heat, pressure, and shear to gelatinize starch and denature proteins. Expansion is influenced by moisture content and die temperature/pressure.
What is the main reason that stitch pumping is the most used curing method in the meat industry?
It is conducive to mechanization (conveyors and automation)
A higher attenuation factor does what to the distribution?
Makes the distribution less uniform
Lyophilization refers to the process of what?
Freeze Drying
How much air does saturated steam contain?
None
What is a hydrostatic cooler and how does it work?
Large continuous sterilizers used for productin of high volume products where ther eis no requirement to regularly change the container size or processing conditions
What are some of the osmotic agents?
Mono-, di-, polysaccharides, inorganic salts, ethanol, polyols
In pasteurization of foods, what is an LTLT process and why is it used instead of other pasteurization methods?
Low Temperature Long Time; pasteurization to inactivate pathogens without denaturing the protein; used for shell eggs and raw oysters
What are the driving forces of membrane processes?
Transmembrane pressure, concentration gradient, chemical potential, osmotic pressure, electric field, magnetic field, partial pressure, pH gradient
Describe Hot Fill Hold process.
Used for high acid foods, temp is 170-190 for 30 s to 3 min, will kill all bacterial cells, not spores
Microwave, ultraviolet rays, and gamma rays are all ionizing radiation (True/False)
False
What is an alternative to hydrogenation of lipids that is through to be more healthy but still change functionality of lipids?
Interesterification
What is the purpose of having a back pressure device for the hold tube?
To prevent flashing or boiling
What are kiln dryers?
Tall, deep bed of product 20cm, large capacity, used for apple slices, hops, grains, batch drier, simple to operate, cheap to build, high labor cost, slow, poor control drying
What is lethal rate?
The Lethal Rate is defined as 10^[(T-Tref)/z] and has units of equivalent minutes at the reference temperature per minute of actual processing
How does a spray drier dehydrate foods?
It sprays the liquid foods through a nozzle into a funnel-like compartment and uses hot air to dry
Bonus: Give the engineering term which describes the following: the ratio of the characteristic time of a particle (or droplet) to a characteristic time of the flow or of an obstacle; the ratio of yield stress to the viscous stress; the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity
Stoke's Number, Bingham Number, Prandtl Number
What is the amount of antibiotics allowed in milk?
Zero
The thermal conductivity of ice is approximately how many times greater than that water?
Four times
Name 2 types of pumps used primarily in food industries.
Rotary and positive displacement
What graph in non-dimensional form relates the friction factor, Reynolds number and relative roughness for fully developed flow in a circular pipe?
Moody Diagram
What is the stress needed before a substance flow?
Yield stress
The enzyme used to manufacture the liquid center of candies is:
Invertase
What is pasteurization used for?
Used in both high and low acid food to help prevent unwanted microbial growth
Which of the following is not a cause of major losses of B vitamins during food processing: trimming and peeling, removal of bran during milling, reactions with free radicals, or leaching during blanching
Reactions with free radicals
An ideal gas at 25C and a pressure of 2 MPascals is passed, without a change in volume, through a valve decreasing the pressure to 0.2 MPascals. What happens to the temperature of the gas?
The temperature decreases - the gas is ideal and therefore obeys the gas law PV=NRT
A plot of 1/Vmax plotted against 1/ substrate concentration is called what?
Lineweaver Burk plot
What salts can be used to promote coagulation when making tofu?
Calcium sulfate or magnesium chloride
Is radiation a fast or slow method of heat transfer?
Fast
What are the effects of drying on microflora?
Dehydration id a good method to prevent microbial proliferation, rehydrated foods need to be consumed more or less immediately, high d-value at low moisture-more resistant to thermal processing
The position in a can of food which is last to reach the final heating temperature is called what?
Cold point
What are the parts of a continuous retort?
Pre-heat, steam chamber, air cooling, (hydrostatic cooling), cooling bath, can feed and can discharge
How is microbial growth controlled during refrigerated storage?
Low temp - Slows the rate of micro growth at each step - Reduce lag phase - Slow growth in exponential phase - Reduce generation time.
The internal friction which tends to bring to rest portions of the fluid which are moving relative to one another is called what?
Viscosity
What is ultrafiltration?
Particles retained 0.001 - 0.02 µm, Pressure 10-100 psig, Proteins rejected (macromolecules)
What are the disadvantages of using Reverse Osmosis (RO) and Ultrafiltration (UF)?
Disadvantages of using membranes: -Membranes can get clogged. -Concentration gets to only between 40 to 50% compared to 80% in evaporation.
Type of food spoilage organisms depend on food composition and intrinsic and extrinsic factors. Give 3 each of intrinsic and extrinsic factors
Intrinsic: physical structure, Moisture content, pH. Extrinsic: temperature, relative humidity, gas atmosphere, light
What are some advantages of a liquid-in-glass thermometer?
Easy portability, independence of auxiliary equipment, low cost, compatible with most environments, moderate ruggedness, wide range of temperatures
Explain the commercial process of hydrogenation.
Hot oil is treated with hydrogen using nickel catalyst
name the 2 most common positive displacement pumps.
Rotary and reciprocating
At what frequency are radio waves typically at?
less than 300 MHz
How many rads are in one gray?
100
What are the food applications for Reverse Osmosis (R.O.) and Ultrafiltration (U.F.)?
R.O. most economical for dilute solutions: Used widely for whey from cheese manufacture. Examples of other uses: 1) To concentrate and purify fruit juices prior to evaporation. 2) To concentrate citric acid, egg white, coffee, natural extracts and flavors. 3) To clarify wine and beers. 4) To demineralize and purify water.
When a force acts parallel to a surface, the stress is called what?
Shear stress
Give me four reasons why compounds are micro encapsulated?
Increase bioavailability, delayed release, stability, to protect (to protect reactive substances from the environment To convert liquid active components into a dry solid system to separate incompatible components for functional reasons to mask undesired properties of the active components to protect the immediate environment of the Microcapsule in capsules from the active components, and then the controlled release or delayed release)
How do you get latent heat from the steam table?
You take the enthalpy of saturated vapor minus enthalpy of liquids, or there will be a column enthalpy of evaporation which is equal to latent heat
Name three types of evaporation.
1) Sun drying 2) Heated kettle/open boiling 3) Heated kettle/vacuum evaporation.
What gas has been successfully collected and converted to electricity from decomposing animal wastes?
Methane
Name three drying methods used.
spray drying, freeze drying, bed, drum, convection, sunlight, dehydration
Describe the pasteurization process.
Product heated to desired temperature, product held at desired temperature for defined time (typically for 5D-6D reduction targetting specific pathogens), product cooling, and product handling/distribution under refrigeration
Describe how a material is heated using radio frequency heating.
The radio frequency generator creates an alternating high frequency electric field between two electrodes (or capacitor), the material being heated is conveyed between the electrodes causing power water molecules in the material to continuously reorient to face opposite electrodes. the friction from the molecular movement causes the material to rapidly heat volumetrically
What common purpose is served by sodium metasilicate, sodium hexametaphosphate and sodium pyrophosphate?
They are all alkaline cleaners
What type of heating arises from the direct conversion of electrical energy in the form of microwaves to heat within the volume of the food itself?
Microwave heating
Define a refrigerant.
A substance that has a boiling point of less than 32F
How can osmotic pressure affect shelf life?
One can regulate the shelf life of foods by adjusting the osmotic pressure of the solution. Π > 12.7 MPa most bacteria do not proliferate Π > 17.3 most yeast do not proliferate Π > 30.1 most molds do not proliferate
What is the term introduced by the Japanese that refers to chemicals enhancing food and palatability?
Kokumi
Commercial Lecithin comes from what?
Soy
What is the equation for convection and how can we effect heat transfer?
There are two mechanisms - random molecular motion (diffusion) and bulk motion of the fulid (when velocity = 0 only diffusion, when velocity ≠0, diffusion + bulk motion). Equation : Q=Asteam hsteam(ΔT) then conduction through wall then Q=Ajuice hjuice(ΔT) where h is the convective heat transfer coefficient. Relationships: as increase velocity of the fluid, then decrease the boundary layer, then increase the heat transfer coefficient, and increase hear transfer rate. If increase viscosity, then increase boundary layer and decrease heat transfer coefficient and decrease heat transfer rate.
What is the SI unit of pressure?
The Pascal
Which body has more BTU's: 5 gallons of water at 70?F or 1 gallon of water at 150?F?
Five gallons at 70?F
Dehydration, definition and purpose
The removal of water from a food by heat and it lowers the water activity, concentrating flavors
Define D-value.
Decimal reduction time, time for 1 log cycle reduction in viable cells at specific temperature
What preserving process loses the most vitamins and minerals?
Canning
A strawberry processor makes a "4+1" product. What do that "4" and "1" stand for?
4 parts strawberries, 1 part refined sugar
The term used to describe the relative masses of equal volumes of a material being measured and water at a stated temperature is what?
Specific gravity
What is Membrane Separation?
Selective permeability. Classification based on molecular size.
If water and orange juice are placed in a freezer at the same time, which will freeze first and what is the name of the law that governs this phenomenon?
The water freezes first: freezing point depression is due to increased concentration of dissolved solutes governed by Raoult's Law
List all the different types of thermocouples.
J, K, E, T, N, B, R, S
When air is passed over a thin layer of water (such as water in a wick surrounding a thermometer) it assumes a characteristic temperature governed by the moisture content and temperature of the air. What is this temperature?
Wet bulb temperature
List three common types of thermal processing methods and their typical applications.
Blanching: Inactivates enzymes in vegetables. Pasteurization: Destroys pathogenic microorganisms in milk/juice. Sterilization: Kills all microorganisms in canned goods.
Which has a higher thermal conductivity: frozen peas (at 0 oC) or fresh peas (at room temperature)?
The frozen peas
What device is used to separate condensate from steam?
a steam trap
Name 2 parameters affecting the temperature during the thermal processing of canned foods.
1) Surface heat transfer coefficient 2) Heat transfer properties of food and can
Soft wheat is preferable for flours used in making cake because
development of weak gluten (soft crumb etc.)
Why won't irradiated foods develop higher than normal levels of radioactivity?
99% of food tissue is hydrogen, carbon, nitrogen, or oxygen, none of which are convertible into unstable radioactive isotopes by the radiation energy levels used in food irradiation.
What is nip feeding for drum drying?
simplest, only for double drums, for thin solutions like milk/whey, adjust gap bwn drums control film thinkness, uniform distribution essential, pendulum feed, or perforated pipe used to supply material into pool in space between drums
What method or substance is used to sterilize spices?
Ethylene oxide or propylene oxide or irradiation
What is "Radappertization"?
Sterilization by exposing food to ionizing radiation.
What does a BCU of 0.00 indicate?
The BCU (baking contrast units) range from 0.00 (darkest) – 5.25 (lightest) BCU.
List the following olive oil grades from most pure to least pure. US virgin olive oil not fit for human consumption without further processing, US extra virgin, US virgin, US olive oil, US refined olive oil
US extra virgin, US virgin, US virgin not fit for human consumption without further processing, US olive oil, US refined olive oil
Name 3 methods of fruit and vegetable peeling.
Steam peeling, knife peeling, abrasion peeling, caustic peeling and flame peeling
What are the five classes of unit operations?
Fluid flow (fluids transportation, filtration, solids fluidization) heat transfer (canning, freezing, blanching) Mass Transfer (extraction, dehydration, frying) thermodynamic processes (gas liquification, refrigeration) Mechanical processes (solids transportation, crushing and pulverization, screening and sieving)
What are the disadvantages of Continuous cryogenic freezing?
High cost of refrigerant. - Cost of pressurized vessel. - Possible quality problems due to cracking.
What is a sorption isotherm?
Relationship between equilibrium moisture and water activity
To calculate the lethal effect of a thermal process, two items of information are needed. Name the two items.
1) Thermal resistance characteristics of the microorganisms (reaction rate constants, Z and F values) 2) Dependence of the rate constants on temperature (temperature history)
What are the effects of drying on flavor?
Heat treatment reduce volatiles, introduces additional compounds, mechanisms (evap, autoxidation fatty acids, thermal decomp, maillard reactions, inactivation volatile forming enzymes) factors: temp moisture content, vapor pressure volatiles, solubility volatiles in water, open pore structure of food)
How are vacuum pressure, atmospheric pressure and absolute pressure related?
Absolute pressure = atmospheric pressure-vacuum pressure
What is the principle behind spray drying?
Every spray dryer consists of feed pump, atomizer, air heater, air dispenser, drying chamber, and systems for exhaust air cleaning and powder recovery. Temp out:50-100C, Temp inlet: 140-270C. There is a critical moisture content below which the surface becomes impermeable to aroma compounds thus preventing losses of flavor
What does the term "cold sterilization" mean?
Sterilization by radiation because no heat is generated
What does power dissipation measure and what are the units?
Conversion of microwave energy to heat, and W/cm^2
What are three goals of conching?
To remove undesirable volatiles, to drive off moisture, and to coat all particles of cocoa solids and sugar with cocoa butter
Why are fats neutralized during processing and manufacture and how is it done?
Oil breakdowns to Free fatty acid & other simple compounds, lead to off flavor & off odors, Soap is formed from the fatty acids by addition of alkali to remove these undesirables.
What is a Newtonian fluid?
Layers slide over each other
What is angular acceleration?
The change in angular velocity divided by the change in time
Which refrigerant is the trademark for a family of fluorocarbons manufactured by DuPont and is commonly used as refrigerants, solvents, and in other applications?
Freon
What is counter-current operation?
Counterbalances resistance to drying, highest temp at lowest moisture content, increase danger of scorching, complete volume shrinkage can take place
What is the common metric unit for mass?
Kg
Polyvinylpolypyrrolidone, gelatin, egg albumin and Icing glass are commonly added to beverages direct processing, why?
To clarify because they form complexes with tannins and polyphenols which then precipitate out.
Why does water have a high specific heat?
Stabilizing effect of hydrogen bonding
What are the advantages of drum drying?
Products have good porosity and hence good rehydration due to boiling evap, can dry very viscous foods, such as pastes and gelatinized or cooked starch not easily dried by other methods, have high energy efficiency, clean and hygienic, easy to operate and maintain, dryers are flexible and suitable for multiple but small quantity production
An additive used to retain moisture in products is known as a _____.
Humectant
What is the world's oldest and most common form of food preservation?
Drying
What is "converted rice" and how is it manufactured?
Whole grain rice is parboiled or steeped in hot water prior to removal of the hulls, bran, and germ in milling. The rice loses fewer nutrients as the B vitamins and minerals from the hulls, bran, and germ are leached into the endosperm. The converted rice is then dried, milled, and polished
What is a humectant?
Humectants control water activity in foods, thus enhancing stability and viscosity, maintaining texture and reducing microbial activity. Humectants chemically bind water and reduce water activity.
What are the X and Y axis on a lineWeaver Burk plot?
X=1/[S] (substrate concentration) and Y=1/v (velocity (reaction speed)
The two most popular means of measuring temperature in heat penetration tests involve what two devices?
1) Thermocouple (requires electrical hookup) 2) Thermistors (uses radiotelemetry)
What is the relationship between wavelength and frequency?
wavelength= speed of light / frequency or speed of light = frequency * wavelength
What is a commercial undercounter refrigerator known as?
A lowboy or a bar refrigerator
The temperature at which water boils _____ as elevation increases.
Decreases
What is dry bulb temperature?
Temp of air measure with thermometer freely exposed to air
using 4 significant figures, tell us how many pounds a gallon of water weighs.
8.345 lbs
What are the four main products of the corn wet-milling proces?
Protein, starch, oil, fiber
What is Gauge pressure?
Positive difference between atmospheric pressure and absolute pressure, measures pressures greater than atmospheric pressure
What is food processing?
Food preservation method, creates functionality, and increases nutrition
What are Unit Operations?
Describes the processing step of a product, like in a factory (i.e. heat exchange, evaporation, drying, and material handling)
What is the primary purpose of blanching vegetables prior to freezing?
Enzyme inactivation.
In the United States, how much chocolate liquor must each of the following products contain? Milk chocolate, sweet chocolate coating, bittersweet chocolate
Milk chocolate: 10%; Sweet chocolate coating: 15%; Bittersweet chocolate: 35%.
Are there any negative changes caused by Refrigeration?
There are some changes that are not beneficial: - Vitamin degradation takes place. - Some Fruits and Vegetables cannot be stored at refrigerated storage temperatures due to the optimal storage conditions for these items being higher than refrigerated temperature.
Hydrogenation of oil does what?
Makes it more solid at room temperature
What should be the size of milk fat globules after homogenization?
less than or equal to 2 microns
Name 5 types of air convection dryers (heated air dryers)
Kiln, cabinet, tunnel, Solar, conveyor, fluidized bed, air lift, rotary, spray drier, Freeze Dryers, Vacuum Dryers
The temperature at which the water vapor in the air under a constant barometric pressure will condense into liquid water is called?
Dew point
Describe two kinds of fluids that require yield stress before flow occurs.
1. Bingham liquids: Newtonian response after yield stress, straight line not through origin 2. Bingham plastics: Shear-thinning behavior after yield stress, curve not through origin. 3. Herschel-Bulkley fluids
Name two types of heat exchangers used to process particulate foods?
Scraped surface and tubular
What are the units for the convective heat transfer coefficient?
W/m2C or W/m2K
What are the advantages of Continuous cryogenic freezing?
Shorter freezing and chilling time: rapid. - Texture damage is minimal. - Smaller equipment. - Oxygen is limited from environment. - Less maintenance required.
What kind of chart is used to find wet bulb temperature, dry bulb temperature, and percent relative humidity?
Psychrometric Chart
Define the 'hurdle concept' as it pertains to foods.
preservation technique that involves using multibarrier methods in order to prevent microbial spoilage of foods: ex. combination of salt, water activity, pH, and temperature on the inhibition of bacterial growth
What is tangential flow filtration?
Increases permeate passage through the membrane, greatly improves efficiency
What is the purpose of Thermal Vapor Recompression?
Fresh steam is combined with used vapor saving energy during evaporation.
What is the relationship between thermal death time and temperature for bacteria?
It is not only a relationship between TDT and temperature but also time, the time at a certain temperature needs to be above the TDT in order for the process to be affective. Also increasing temp will reduce processing time
What are the two substrates for soy sauce production?
Wheat (or Rice) and Soybeans
What is the strategy of preserving food that involves combined different ways of preventing microbial growth called?
Hurdle technology
What is incipient spoilage in thermally processed foods?
Spoilage that occurs prior to thermal processing
What changes are caused by refrigeration?
Low temperature - limited chemical, biochemical and physio-chemical changes.
What is the name for the absolute temp scale in the English System that is based on the Fahrenheit scale?
Rankine
list 2 approved application of gamma irradiation in foods.
Inhibit sprouting in tubers and bulbs,reduce microbial population in spices,destruction of salmonella in poultry,destruction of spoilage microorganisms
What is Newtonian fluids?
Fluids that show a linear relationship between shear stress and shear rate.
What processes are used to separate and isolate whey proteins from the lactose and minerals in whey?
Ultrafiltration and diafiltration
What is drum drying?
Horizontally mounted hollow cylinders made of high grade cast iron or stainless steel, a supporting frame, a feeding system, a scraper and auxiliaries
The "cold break" tomato process which is used to produce some soups and ketchups, involves brief activation of which enzyme?
Pectin methyl esterase, polygalacturonase
What are the advantages and disadvantages of continuous retorts?
Advantages - gradual temperature and pressure change, less strain on cans. Disadvantage - high capital investment, breakdown will stop process line
Who developed the first mathematical equations to predict thermal process time?
Ball
What parameter describes the time required at a given temperature to reduce microbial population by 90%?
D-value.
What do the Grashof number, Nusselt number, Prandtl number, Biot number, and Fourier number all have in common?
They are all dimensionless
Name the piece of milk processing equipment used to remove some bacteria and sediment originating from the cow's udder.
Clarifier
A product with a drying ratio of 5 yields 1 kg of dry product for every how many kg of water removed?
4 kg of water removed.
How does ultraviolet light affect fat oxidation?
Accelerates
What factors do you need to take into consideration when doing evaporator calculation?
Mass balance equations (total balance, solute/solid, water, evaporation rate, feed rate) energy balance (energy input from steam, energy consumed by evaporator)
The theoretical expression describing the force which must be applied before a substance will flow freely is called ...
Yield stress
The typical process controller used on a retort is called a PID controller. What do the initials PID stand for?
Proportional Integral Derivative
What is sodium silicoaluminate used for?
An anticaking agent
What is a 15 degree Brix solution?
A solution containing 15% (by weight) sugar
What are microbial and enzymatic factors that affect sterilization time?
Heat resistance of microbes and enzymes, pH of food
With respect to distillation theory, what is the term referring to one cycle of condensation and distillation?
Theoretical plate
In Total Quality Management, what do the letters JIT stand for?
Just In Time
What are three methods used for precooling of fruits and vegetables?
Hydro- cooling, Vacuum cooling, Air cooling
What is angular velocity?
Change in angle divided by time taken. When angular velocity of a rotating object is in radians per second, the linear speed v of a point on the object given by v=ωr, often rotational speeds are given as N rev/min
Of the four stages in a refrigeration cycle, expansion, evaporation, compression, and condensation, which is a constant entropy process?
Compression
Named after the Italian physician & physicist Luigi Galvani, name the instrument used to measure electric current.
Galvanometer
What are the 4 purposes of evaporation in industry?
To reduce the volume of the product, to economize on packaging, shipping storage and distribution costs. To pre-concentrate liquid foods such as fruit juice, milk and coffee before product enters a dehydration process, thus saving energy in subsequent operations. To increase solids content of food and hence preserve it by lowering water activity. To reduce the microbial load and stabilize the product
What is mechanical vapor recompression?
Use compressor to increase pressure of vapor to increase energy efficiency. Mechanical energy supplies via a compressor or fan compresses the process vapor to a higher pressure (and condensing temperature) where it is reused as the heating steam
Explain the triple point of water
At 4.5 mm Hg pressure and 0.01 °C water exists in liquid, solid, and vapor states
What are the applications of freeze drying in the food industry?
Products include veggies, juices, fish, and other processed products, military meals, also used in the floral industry
How does frequency affect dielectric properties of foods?
It changes the dielectric constant, higher frequency lower dielectric constant
What dimensionless number represents the ratio of inertial to viscous forces in fluid flow?
Reynolds number.
What are the different types of equipment used for retorting?
Batch type (horizontal or vertical) continuous retort (hydrostatic coolers, cooker-coolers, rotary sterilizers
What are the 3 main types of indirect heating?
PHE, THE, SSHE (plate heat exchanger, tubular heat exchanger, and scraped surface heat exchanger)
What are 4 ways to lower water activity?
Dehydration (remove water), concentration (increase solids content), add salt, add sugar (both salt and sugar compete for water)
In food freezing, what is the term for the critical zone of temperatures (usually 31 F to 25 F or -0.5 C to -3.9 C where most quality damage from large ice crystal formation occurs?
Zone of Maximum Ice Crystal Formation
What is the vapor pressure of water at 212F?
1 atmosphere or 14.7 psi
What is important in Retail storage?
Convenient visibility is important.
State the Arrhenius equation and its variables.
ln K= ln A - (Ea/RT) or K=A.e^(-Ea/RT); Where k is the rate constant, A is the pre-exponential factor, Ea is activation energy, R is the gas constant, and T is absolute temperature (Kelvin)
What is an advantage of UHT?
Process conditions independent of container size
When is the cooling effect of ice the highest?
It's the highest at the point the ice is melting
Name four types of peeling methods.
Hand peeling, flame peeling, mechanical peeling, lye peeling, hot water peeling, steam peeling, abrasion peeling, cryogenic peeling.
Why do we care about the heat transfer rate (Q) ?
Because if we increase heat transfer than we decrease residence time, and increase the capacity, this lets us reduce capital investment and increase profit. Also if decrease residence time then you will decrease quality degradation
How many significant figures are in the number 0.000401?
3
Name 5 types of nonthermal pasteurization.
High-pressure processing, pulsed electric field, ultraviolet, radio frequency, ultrafiltration
What might the Doppler effect be used to measure in food settings?
Flow velocity or food intake
What are the main causes of product quality deterioration?
Chemical, Biochemical, Physio-chemical, and Nutritional.
What is a material property that determines the distribution of energy within the material?
attenuation factor
Is HTST suitable for food products with large discrete particles?
No
What are some of the ways parameters can be changed to alter the drying?
If the air temp is increased you increate the Rc (constant rate). Increase the air relative humidity, increase density of moist air and decrease change in temp and decrease Rc. Increase the air velocity the increase heat transfer coefficient and increase Rc. If increase thickness, decrease constant rate.
What is the overall heat transfer coefficient/ How is it calculated?
1/U = 1/hsteam + L/k + 1/hjuice + Rf; U = overall heat transfer coefficient h = convective heat transfer coefficient k/L = conductive heat transfer coefficient = thermal conductivity/thickness Rf = Fouling factor
What are the effects of drying on nutrition?
Vitamin losses, protein - loss of biological value, the most susceptible nutrients to dehydration: unsaturated lipids, proteins, vitamin C
Name 3 design considerations in an air impingement oven.
Air velocity, jet configuration, nozzle to target surface spacing, location of exhaust ports, induced or imposed cross flow, surface motion, angle of impingement, nozzle design, temperature differences between the jet and the impingement surface
which of the following food categories is NOT approved for treatment w/irradiation: A.fruits, B.milk and dairy products, C.animal and pet foods, or D.none of the above?
B. milk and dairy products
How does Refrigeration affect microbial growth and food quality?
- Retard microbial growth - Limit lipid oxidation - Limit non-enzymatic browning and enzymatic browning - Slow down sugar conversion - Reduce respiration reactions.
Name 3 necessary elements of proper refrigeration.
Constant temp, humidity control, and air circulation
What is the freezing point of pure water at sea level?
0°C (32°F)
What is heat recovery and how is it calculated?
It is the amount of heat that can be reused in the heating process, it denotes the effiecncy of the regeneration section . heat recovery %= (T2-T1)/(T3-T1) x100 where T1 is the inlet temperature, T2 is temp at the end of regeneration section, T3 at the end of the hold up tube
What are the types of membranes used in membrane separation?
Microfiltration, ultrafiltration, nanofiltration, reverse osmosis
What process is done prior to freezing or dehydration to inactivate enzymes?
Blanching, chemical inactivation
In terms of dehydration please describe how osmosis works.
As water on the surface evaporates, the water moves from the interior to the surface due to the new concentration gradient.
What does GMP stand for and why does it exist?
Good Manufacturing Practice, to make food products sanitary
Name five categories of freezing equipment used in the food industry.
1-The air blast freezers / cold storage freezers 2-The cartoon freezers / box freezers 3-The spiral belt freezers 4-The fluidized bed freezer / IQF freezer (or tunnel freezers) 5-The immersion freezers / brine freezers 6-The plate freezers / block freezers 7-The contact belt freezers 8-The impingement freezers / flat product freezers 9-The cryogenic freezers
Which of these food additives could be used to prevent cocoa particles from settling in chocolate milk? A) BHA (butylated hydroxyanisole) B) Carrageenan C) Thiamine Hydrochloride D) Citric Acid
B) Carrageenan
What do CIP and COP stand for wrt dairy processing?
CIP-Clean In Place; COP-Clean Out of Place
How is banana oil made?
Synthetically using isoamyl acetate
What is a steam table? What is it used for?
A steam table gives different boiling point and what the vapor pressure has to be to achieve boiling (local pressure=vapor pressure at boiling) and then what the enthalpy of liquid vapor and liquid is at that temperature and you can subtract the two to get latent heat. It is used to find the boiling point at different pressures and also the amount of energy needed for vaporization at that point.
What are the three mechanisms of transferring heat energy in a food system?
Conduction, Convection, and Radiation
Which of the following are emulsifying salts for use in the processing cheese? A - sodium tartrate, B - sodium chloride, C - Potassium chloride, D - all of the above
a. sodium tartrate
What are the three types of emulsions?
semi permanent, permanent, and temporary
Describe osmosis in terms of dehydration
As water on the surface evaporates, water moves from the interior of the product to the surface due to the concentration gradient.
What are indirect food additives?
"Indirect" food additives are those entering into food products in small quantities as a result of growing, processing, or packaging.
What is the collapse problem with freeze drying?
Don't want to cross rubbery stage during freeze drying, otherwise the food will collapse
Name 3 components of a freeze-drier.
Condensor, vacuum pump, heat source
Name 3 sanitizers commonly used in food processing.
Quats (quaternary ammonium compounds), chlorine, iodophores
What type of pump is preferable and why in an aseptic processing system and?
PD pump (positive displacement pump), it is less sensitive to pressure drop than centrifugal pumps
Define commercial sterilization.
All pathogenic and toxin-forming organisms have been destroyed but it still may contain viable spores that cannot grow under normal conditions
How long is the average lactation cycle of a cow?
The cycle is split into four phases, the early, mid and late lactation (each of about 120 days, or 305 in total) and the dry period (which should last as long as 65 d). In an ideal world, cows calve every 12 months
A sling psychrometer is a special instrument designed to directly measure what?
Dry air temperature and wet bulb temperature (relative humidity is an indirect measurement)
Compare spray drying and freeze drying in terms of process and product quality.
Spray drying: Rapid water removal by hot air; economical but may lose volatiles or cause oxidation. Freeze drying: Sublimation under vacuum; retains nutrients, structure, and flavor but costly and time-consuming.
Define viscosity.
The state of being thick, sticky and semifluid due to internal friction. measure of its resistance to gradual deformation by shear stress or tensile stress
What does a manometer measure?
Pressure
What is the benefit of HTST pasteurization?
less change in nutrient composition and sensory attributes, less change in overall food quality, continuous throughput, lower utility costs, longer shelf life
How does the high sugar content in food affect the drying process?
It takes longer, as sugar attracts water.
Name at least four reasons for processing foods.
1. Preserve against deterioration 2. Provide adequate food supply throughout the year 3. Convenience 4. Provide uniform quality of foods on a large scale 5. Create new products to meet specific nutritional needs or changes in technology.
Give the time and temperature for batch, or LTLT, pasteurization.
63°C (145°F) for 30 minutes
In the sugar refining process, what is the function of earth and charcoal?
Decolorize.
The doppler effect is used for what purpose in the food industry?
Measure flow rate
What is the 1st law of thermodynamics?
Energy can neither be created nor destroyed. It can only be converted from one form to another. The total amount of energy of an isolated system is constant.
What are the advantages & disadvantages of flat sheet/plate and frame membrane modules?
Advantages: Low hold up volume, Permeate from individual membrane element, Membrane replacement easy Disadvantages: Difficult to clean, Susceptible to plugging
Rank the following membrane separation methods based on increasing pore size: microfiltration, reverse osmosis, nanofiltration, and ultrafiltration.
RO, NF, UF, MF
The amount of heat required to raise the temperature of 1 g of water 1 C is called what?
Calorie
Name types of concentration methods/equipment.
1) Solar evaporation 2) Flash evaporators 3) Ultrafiltration 4) Open kettle 5) Thin-film evaporators 6) Reverse osmosis 7) Freeze concentration 8) Vacuum evaporators.
What happens during the secondary phase of freeze drying?
Removable of non-freezable water via evaporation, lowers the water activity
True or False: The geometric center of a can is the slowest heating point for foods heated by convection.
False. The slowest heating point is near the bottom of the container.
How does a citric acid dip prevent the browning of fruit?
Chelates metal ions (also decreases the pH).
What are conveyor belt dryers?
Food placed on mesh belts up to 15cm deep, air flow directed up through wet food and down through dry food, multistage, good control over drying conditions high production rates, low labor costs, highly automated, continuous, replacing tunnel driers
What are the different ways to set up membrane filtration?
Batch operation, continuous operation (single pass , feed and bleed)
Name two processing considerations for a tubular centrifuge.
Limitations for solids <25kg, has relatively high speed and length to radius ratio, useful clarifying lightly loaded suspensions
Name four products in which pectin is used.
Jams, jellies, fruit juices, tomato sauces
Capillary tube and rotational are two types of what instrument?
Viscometer
Which of the following is the strongest form of radiation: a. alpha, b. beta, c. gamma, d. delta?
c. Gamma radiation.
What is a theoretical plate in simple distillation?
A theoretical plate is an area in the column where the recondensing liquid and the rising vapor come into equilibrium with one another
What are "Designer Foods"?
Foods containing large amounts of beneficial phytochemicals
Why is mozzarella cheese "stringy" compared to other cheeses?
Kneading and stretching the curds help to elongate this protein chain, which causes the stringiness of mozzarella.
What are foam mat dryers?
Food products (juices) formed into a stable foam by addition of a stabilizer and aerating with inert gas, foam is spread on belt drier 2-3mm, through flow co or counter current flow, rapid drying, lower process temps, superior flavor and quality, low bulk density of product, may need more than one stage to obtain required moisture, more expensive than most dryers
Name 5 microwave applications in food processing.
Tempering, heating/reheating, cooking/pre-cooking of meat/poultry, drying/dehydration, baking/cooking, blanching, pasteurization/sterilization
What are 4 advantages of radiant heat?
Non-contact heating, fast response, reduced heating time, uniform heating, reduced quality losses, versatile, simple, compact equipment, and significant energy saving
Explain Innovative Nonthermal Processing.
Refers to new technologies that preserve the food supply without raising the temperature; to eliminate thermal degradation of food quality
One of the major fructose concentrations used by beverage manufacturers is which of the following: a. 30%, b. 32%, c. 40%, d. 42%?
d. 42%
Define the "refractive index"
The numerical measure of the degree of light bending that occurs when light passes through a substance.
Why does phosphate salt add to cured beans?
Promote water tension, juiciness of texture.
What is the thermal conductivity of ice?
2.22 - 2.35 W/m K (4 times more than water)
What does the area under the lethal curve rate represent?
Lethality, it is the same as F0
What happens in the primary drying phase?
Removal of freezable water via sublimation, heat for sublimation must be supplied, temperature limitation, below 0C
What does FIFO stand for and why it is used?
First in First out, to ensure product turnover
With respect to food processing, what is SS 316?
SS 316 is a food grade austenitic stainless steels
The concentration of a dissolved salt solution by the application, on the solute side of the membrane, of pressure in excess of osmotic pressure, is called what?
Reverse osmosis
How can we enhance heat recovery?
By increasing the heat exchange area in the regeneration section, by using more plates in the regeneration section of plate type pasturizer, by increasing the length or diameter of tubes in regeneration section of concentric tube pasturizer
what is the common metric unit for acceleration?
acceleration= meters/seconds^2
A food preservation method that utilizes liquid nitrogen to rapidly freeze foods is called what?
Cryogenic Freezing
What are cyclones used for in milk spray-drying systems?
To sediment small particles of powder still present in the air before its release.
What three parameters determine hold tube length?
Residence time, system flow rate, hold tube internal diameter
What is the term for determining the microwave absorptivity of a material and absorbed microwave energy determines the amount of energy converted to heat?
Dielectric loss factor
Define sterilization.
Complete destruction of microorganisms, requires at least 250F, time is important.
Why is ascorbic acid sometimes added to flour?
it acts as an oxidizing agent in a dough system, causing cross-linking between gluten protein thus imparting strength to the dough
What are brix?
Brix = g solids / total solution g (Solids + solvent)
Given an example of a product that requires asceptic processing.
Liquid eggs, milk, milk products, long term products that need to be sterile
What type of detergent should be used to clean fat from equipment?
alkaline
Thermal destruction of microorganisms obeys zero order, first order, or second order kinetics?
First order
What is a well-known gum used by microbiologists in bacteria cultivation and by food technologists in icing production?
agar-agar
What are the stages of freeze drying?
Freezing: Solidifying the water. Primary Drying: Sublimation of ice under vacuum. Secondary Drying: Desorption of bound water.
How many pints are in a half-gallon?
Four
What are the biochemical reactions affecting product quality?
1. Enzymic browning - occurs in fruits and vegetables after bruising and processing. Phenolic compounds react with phenolases with oxygen to produce yellow-brown pigment. - Vacuum packaging, modified atmosphere packaging, sulphites, citric acid or ascorbic acid reduce the effects of browning. 2. Glycolysis - Breakdown of glycogen in living tissue - happens after harvest/slaughter oxygen causes breakdown of tissue and softening of structure. 3. Proteolysis - Proteases enzymes attack protein matter in food breaking them down to peptides or shorter chain amino acids. 4. Lipolysis - Lipolysis causes loss of product quality. - Lipases cause catalysis of hydrolysis of triacylglycerols into fatty acids and glyceride breakdown."
What are the benefits of using SO2 in dehydration processing?
SO2 pasteurization, prevent enzymatic browning, prevent non-enzymatic browning, enhance retention of vit.C
What added ingredient keeps confectioners sugar from clumping?
Corn starch
What commercial product can be described as dilute acetic acid?
Vinegar
Name 3 pieces of equipment that thermocouples are frequently used in
Ovens, furnaces, flue gas, and other areas that have temperatures above 250 C
What are the disadvantages of drum drying?
Some products may not form good film on surface, products with high sugar content may not be easily scrapped off, relatively low throughput compared to spray drying, high cost of changing drum surface b/c of machining that required, possible scorching of the product to impart cooked flavor and off-color due to direct contact with high temp surface
What are two approaches used to make intermediate-moisture foods?
Partial Drying, Osmotic Drying, Dry Infusion, Blending (formulation)
What is the process of removing air from canned foods before sealing called?
Exhausting or vacuum sealing.
What does commercial sterilization refer to?
The use of a thermal process to achieve a shelf-stable food product.
What effect does temperature difference between food and retort have on the time?
Higher difference between retort and food, faster heat transfer
What is "latent heat of vaporization"?
The amount of energy required to convert a unit mass of liquid to gas at its boiling point.
What common purpose is sodium metasilicate, Sodium hexametaphosphate, and sodium pyrophosphate is served in the food industry.
alkaline cleaners.
What person is responsible for developing quick frozen foods?
Clarence Birdseye
What is the SI unit for force/unit area?
Pascal
Flowing liquid increases in kinetic energy because of what?
The pressure drop
Name 3 methods of food preservation.
Drying, salt addition, heat, freezing
What is the difference between white, milk and dark chocolate wrt cocoa contents?
White chocolate: cocoa butter, sugar and milk solids but not cocoa solids Milk: cocoa solids, cocoa butter, sugar, milk solids Dark: higher cocoa content, may include cocoa butter and sugar
In temperature sensing, what does the abbreviation RTD stand for?
Resistance temperature detector
What is absolute pressure?
It is the atmospheric pressure + Gauge pressure or - vacuum pressure.
20g of amylose is added to 80 g of water in a beaker and heated to boiling. What would be the observed boiling point (at sea level)?
100 C - not a true solution, so no boiling point elevation
What is a Kilojoule?
The SI unit of energy.
How does the Wiped-Film or Agitated thin-Film Evaporator work?
Surface is continuously agitated or wiped to prevent build up: example: purees.
Give 3 methods for the production of corn syrup from starch.
Acid hydrolysis, acid-enzyme hydrolysis, enzyme-enzyme hydrolysis
which of the procedures listed is designed to kill most microorganisms: A.radappertization, B.radicitation, or C.radurization?
A. radappertization
Okara is a by-product of what processing?
Soy
When viscosity of a fluid increases, what happens to the reynolds number?
Decreases
Why is flash cooling important?
It produces a consistent product density
Compared to reverse osmosis, ultrafiltration requires a) more pressure b) less pressure c)same pressure
b) less pressure
What is a batch pasteurizer and how does it work?
It helps to reduce the formation of cold spots
What is the name of rotating screw technology?
Extruder
What are the applications of microencapsulation?
Carbonless paper, flavors and essences, pesticides and herbicides, pharmaceuticals, adhesives etc.
What type of heat exchanger is preferable for high viscosity sauces/foods in an aseptic process system?
scraped-surface
A mathematical expression of the principle of conservation of energy, as it relates to fluid flow, was discovered by a Swiss mathematician in 1738. Today this expression is one of the foundations of fluid mechanics. What is the name of the equation?
The Bernouilli equation
What is the main purpose of homogenization in milk processing?
To reduce fat globule size and prevent creaming
What processing principle or technology is used to preserve the following foods: canned beef, potato chips, ketchup, and yogurt?
Canned beef: retort (heat sterilization) Potato chips: dehydration Ketchup: acid, heat sterilization/hot filling Yogurt: fermentation, low storage temperature.
What is the relation between Wet bulb temperature, dry bulb temperature and dew point temperature at 100% saturation and the same temperature?
They're all equal (WBT = DBT = DPT).
What is thermal conductivity?
A measure of a material's ability to transfer thermal energy. The SI derived unit of thermal conductivity is watt per metre kelvin (W.m-1.K-1)
"Sharp" freezing can be described as.....?
Still air freezing
Name three methods of microencapsulation technology.
Spray drying, spray cooling, emulsification, extrusion, simple coacervation, complex coacervation, internal/ external gelation, fluidized bed coating, etc.
What are the different types of quality changes that can occur from drying?
Kinetics, Effects of food texture (shrinkage, case hardening, crust formation, stress development and cracking, rehydration, flavor, color, nutrition, microflora)
Which nonthermal process called as purple blow torch, inactivates 99% of norovirus on fruit surface?
Cold plasma
What is the typical shelf life of pasteurized milk held under refrigeration?
12-16 days
How does a cooker cooler continuous retort work?
Cans carried over conveyer through 3 sections of tunnel each at different presser
What is a dielectric material and give an example?
Dielectric materials are an electrical insulator that can be polarized by an applied electric field. examples include: porcelain/ceramic, mica, glass, plastics, various metal oxides
What happens at the triple point?
All 3 phases of a substance, solid, liquid, and gas, occur in equilibrium at a specific temperature and pressure that is characteristic for that substance
What type of temperature sensor is made from certain metal oxides whose resistance decreases with increasing temperature?
Thermistor
Under what conditions should a food be classified as a low-acid food for the purposes of canning?
pH > 4.6 and aw > 0.85.
What are the two types of distribution systems for falling film evaporators?
Static distribution system (bowl with smoothing plate) and dynamic distribution system (liquid distribution by means of a full cone nozzle)
What is SCP?
single cell protein
If the time to reduce a population by 5 logs is 20 min, what is the D-value?
4 min
In Microwave processing, what is penetration depth?
The penetration depth is used to denote the depth at which the power density has decreased to 37 % of its initial value at the surface.
What is Reynolds number?
A dimensionless number used to predict flow patterns in different fluid flow situations. Small (<2100): laminar or streamline flow; transition: 2100-4000; High (>4000): turbulent flow.
What is Coulomb's law?
The electrical force between two charges of magnitude Q1 and Q2 separated by a distance r in vacuum is; f = k(Q1*Q2)/r^2) where k= 1/(4*pi*epsilon naught)
Discuss energy consumption with spray drying.
The lower the percent solids, the more energy required for spray drying (that why evaporate before spray dry) heat consumption KJ/ 1kg water = 6000/spray dry, 2600/evap1stg, 1300/evap2stg, 430/evap6stg
what is the most commonly used natural colorant in food?
annato
What are the basic components of evaporators?
Introduction: All evaporators have the same basic components: Principal components include: Steam chest or other ways of introducing steam into the product. Liquid feed: preheated to evaporator temperature before being distributed uniformly to the heat transfer surface area. When boiling has occurred, an efficient separator is required to isolate vapors from liquid concentration.
What percentage of salt is ideal for making sauerkraut?
2.25-3%
What is the purpose of the heat penetration test in thermal processing?
To determine the temperature of slowest heating zone in a food container, and use the time/temperature data to calculate a thermal process that will render the product commercially sterile
What is a eutectic point?
Lowest point on the freezing point depression curve
What is the main advantage of extrusion cooking?
Combines mixing, cooking, and shaping in one continuous process; efficient and versatile.
What form of heat transfer is used in drum dryer?
Conduction
Which of the following set of four conditions would you select for an optimal drying process of any food? a) low temperature, high relative humidity air, and a large surface area; b) low air velocity, long time, and high temperature; c) large surface are, high air velocity, and vacuum pressure conditions; d) atmospheric pressure, low temperature, and low air velocity
c) large surface are, high air velocity, and vacuum pressure conditions
Give 3 examples where enzymes are measured as an indication of quality or as a processing efficiency check.
Lypoxytenase=Blanchiing; Peroxidase=blanching; Alkaline Phosphatase=milk pasteurization; alpha-amylase=starch quality; rennet=curd production efficiency
The study of dielectric properties concerns ____ and ____ of electric and magnetic energy in materials
storage and dissipation
What are the applications of centrifugal separation?
Separation of immiscible liquids, clarification by removal of small amounts of solids, removal of solids,(skimming milk, oil refining, brewing, fish protein concentrate, remove cellular material in juice
What is the purpose of air flow in spray drying?
The initial contact between spray droplets and drying air controls evaporation rates and product temp in the dryer.
What is Thermal conductivity (k)?
Thermal conductivity (k): refers to how heat penetrates the food when freezing the food. It takes into consideration Mw, solids, fat, general composition of the food product.
A physical change in an amorphous material promoted by the addition of heat and the uptake of low molecular weight substances called plasticizers is called what?
Glass transition
What is Conduction Heating?
Conduction is the transfer of heat between stationary particles (molecular motion)
What is centrifugal force?
The outward force nature exerts on objects moving in a circular fashion
What psychrometric property is defined as the weight of water vapor per kg of dry air?
Humidity/ humidity ratio
Give the michaelis-menten equation and give two assumptions underlying its derivation.
V0 = Vmax ([S]/([S] + KM)); This equation includes the assumption that during the early stages of the reaction so little product is formed that the reverse reaction (product combining with enzyme and re-forming substrate) can be ignored (hence the unidirectional arrow under k3). Another assumption is that the concentration of substrate is much greater than that of total enzyme ([S] >> [Et]), so it can essentially be treated as a constant.
Name 6 food products that use freeze concentration.
Coffee, citrus, juices, beer, wine, vinegar, dairy products, meat/fish extracts
Often phage or viruses are used for DNA cloning, what is this process called?
Transduction
What is the common metric unit for power?
Watt
What are fluidized bed dryers?
Food pieces on mesh perforated belt 15cm, hot air blown up through bed at high velocity, particles suspended and agitated improving heat and mass transfer, batch or continuous, multistage in cascade, compact, high drying rates, good process control, limited to small 20µ-10mm particles
What is atmospheric freeze drying?
To maintain partial pressure of water vapor adjacent to the product at a level below triple point of water, approach 1 - inert gas and water vapor pressure = 1atm, approach 2 - capture of the water vapor with adsorbent
What is a mathematical technique for determining the best use of available resources when these resources can be used in other products?
Least cost formulation
Food with pH 3.5 to 4.5 is rated as high acid or low acid?
High acid
How do you convert deg F to deg R?
deg F + 459.67 = deg R
What are the effects of drying on color?
Hunter lab and CIE Lab are most widely used color systems (lightness - L, red/green - a, yellow/blue - b) humans perceive color in terms of lightness, hue, and chroma by the integration of complex color systems. Mechanisms: drying changes the surface characteristics of a food and hence alters its reflectivity, enzymatic browning - dark pigment, photo-oxidation of pigment caused by light in combination with oxygen - meat, chemical changes to carotenoid and chlorophyll pigments caused by heat and oxidation
Why can microwaves go through glass but not metal?
Glass is dielectric
When M. Nicholas Appert developed the principle of canning or thermal processing in the 1800's, which organism was he attempting to inactivate?
None (microorganisms were not discovered until much later)
What is the definition of 1 horsepower (hp)?
33,000 foot-pounds per minute
What are the different types of feeding methods?
Roll feeding, nip feeding, dipping, spray feeding, splashing
What are the two methods of canning?
Boiling water (water bath) and pressure canning
What is the main application of transglutaminase?
Cross-linking of proteins to strengthen gelling properties; mostly used in rice or cornbread applications
How does Mechanical Vapor Recompression save energy during evaporation?
Vapors from a single stage are compressed to higher pressure in a mechanical compressor and then reused as steam in the steam chest. Only a small portion of fresh steam is needed. Present advantages: - Reduced cooling-water requirement - Energy recovery schemes are still feasible - Low temperature between steam and product is used - Short residence time at high temperature - Results in high quality.
Name four examples of traditional nonthermal processing.
1) Modified atmosphere packaging (MAP) 2) Controlled atmosphere storage (CAS) 3) Nitrogen flush packaging 4) Vacuum packaging
Which equation describes the relationship between temperature and water activity?
Clausius Clapeyron Equation
Describe the flow behavior of a Thixotropic material.
Viscosity decreases over time while under a constant shear rate (time-dependent thinning)
Which plant is utilized for extraction of linseed oil?
Flax seed
Define the triple point.
The triple point is the state at which the three phases (solid, liquid, and gas) may all be present in equilibrium
What is the application of Stoke's Law in food processing?
Stoke's Law describes the terminal velocity of a sphere falling (or rising) through a viscous fluid. In food, it explains creaming (oil rising in milk) or sedimentation (pulp settling in juice).
What is hydrogenation?
Addition of Hydrogen to the double-bonds of unsaturated oils. This changes liquid oils into semisolids and makes the fat or oil less susceptible to oxidation and rancidity. It causes fat to be more saturated.
What unit of viscosity is equal to 1 gram per centimeter-second?
Poise
What are 4 steps to ensure a proper natural fermentation of sauercraut?
Salting, shredding, anaerobic storage, low temperatures
What property is related to the rate of heat transfer for unsteady state?
Thermal diffusivity
What are some pasteurization methods?
Thermal pasteurization, High pressure pasteurization, pulsed electric field pasteurization, ohmic heating, ultrasounds, microwaves, radio frequency electric fields, combination of various methods.
When convection predominates, where is the coldest spot in a can?
Approximately 1/2 to 1 inch from the bottom (the "cold zone" where the descending cool liquid pools). 1/3 from the bottom is a common approximation.
What is Specific Heat?
Amount of heat required to raise the temperature of 1 unit of mass by 1 degree (J/kg.K or BTU/lb.F)
What dimensionless number describes the ratio of inertial forces to viscous forces in fluid flow?
Reynolds number.
What is a basket centrifuge?
for abrasive, hard-packing and sticky materials, not used in food industry
What is latent heat of vaporization?
Temperature remains constant as liquid turns to gas
What is the difference between Bingham plastics and Newtonian Fluid models?
Bingham plastics have a yield stress
What is the protein source in TVP (textured vegetable protein)?
Soy
Which of the following is not an assumption required for Bernoulli equation? A. The fluid is incompressable B. Viscosity of the fluid is negligible C. The fluid is well mixed D. The flow is steady
C. The fluid is well mixed
Name the enzyme used to remove O2 from the headspace of canned or bottled products.
Glucose oxidase
What are some factors that may affect aseptic processing?
If the product has particulates, size of particles, viscosity, product thermal sensitivity
Do resistance thermometers or thermocouples have a higher upper limit temperature?
Thermocouple
Name 5 dimensionless numbers utilized to determine aspects of heat exchange.
Biot, Fourier, Prandtl, Nusselt, Reynolds
What is the term used to describe the ratio of the viscous portion to the elastic portion?
Tan delta or loss factor or damping factor
What is another name for the Carnauba wax?
Brazil wax, palm wax, "queen of waxes"
Prevention of damage in food during freezing is promoted by slow cooling to minimize ice nucleation. True or False?
False
Give three product or product category applications for lecithin as an additive?
The primary applications for lecithin are in baked products, dairy blends, baby foods, nutritional drinks, margarines, chocolates, chewing gums, and confectionaries
What needs to be taken into account for production and equipment selection?
Production method (ie/instant coffee) equip selection and sizing
Name five components of pasteurization unit for market milk.
Balance tank, product feed pump, flow controller, separator, constant pressure valve, density transmitter, fluid transmitter, regulating valve, shut off valve, check valve, homogenizer, booster pump, holding tube, flow diversion valve, plate heat exchanger, process controller
How does the addition of salt before the microwave cooking of vegetables affect the cooking time?
The time decreases
Of the following 4 choices, what is the correct set-up of a three compartment sink in a foodservice operations? a) wash, sanitize, rinse; b) rinse, wash, sanitize; c) sanitize, wash, rinse; d) wash, rinse, sanitize
d) Wash, rinse, sanitize
Define "microencapsulation"
Packaging of microsize materials in the form of capsules, which are 1-2000 micron in size.
What are isotonic solutions?
solutions that have the same osmotic pressure at the same temperature
Solids are __ to thermal radiation.
Opaque
Dielectric heating is also called what, and why?
volumetric heating, and because heat is generated throughout the food volume
Name 2 parameters affecting the thermal processing of canned foods.
1) Surface heat transfer coefficient 2) Heat transfer properties of food and can 3) Difference between steam temperature and initial product temperature.
What are methods used to heat containers?
saturated steam, hot water, flames
What was the first product approved for irradiation by the FDA in 1963?
Wheat and wheat flour (for insect disinfestation at doses of 0.2-0.5 kGy).
What are the methods for exhausting containers?
Hot fill foods, cold fill then hear container with partially sealed lid, apply vacuum to remove air, flush cans with steam
What is the cutoff Reynold's number for laminar flow?
2100
Define lethal rate.
F= 10^(T-Tref)/z (often Tref = 250 F)
How would you convert kinematic viscosity to absolute viscosity?
Kinematic viscosity x density= absolute viscosity
How many grays in a rad?
0.01 grays per rad
What other changes can occur in food when pasteurizing it?
There can also be reductions in flavors (or production of off flavors), colors and enzymes and vitamins. Want to select for the right conditions to minimize changes to food while still killing the bacteria in a reasonable amout of time
What are the 3 USDA quality grades of rabbits?
US Grade A, US Grade B, and US Grade C
What is reverse osmosis filtration?
Only water can pass through the membrane, filters out un-disassociated acids and monovalent species, pressure is 200-300psig
What are the component of a freeze dryer?
Heating system, refrigeration system, vacuum system, condenser
What is water activity?
Water activity aw=(P h2O vapor in food)/(vapor pressure pure H2O@same T)= (RH%)/100
Soy flour is produced by solvent extraction of dehulled soybean meat. What is the protein content of this product?
50% or 0.5 fraction
What are some critical factors in designing a thermal process?
Type of food, target microorganism, location of cold spot, shelf life requirement
Since commercial sterility must be assured throughout the food container, thermal process evaluation uses the ___ value in the container to assure sterility.
Slowest heating point (or cold point)
What do SOP and SSOP stand for?
SOP-standard operating procedure; SSOP-sanitation standard operating procedure
Compare ohmic heating and microwave heating in terms of heating mechanism, penetration depth, and limitations.
Ohmic heating generates heat via electrical resistance uniformly throughout conductive food matrices; penetration depends on conductivity. Microwave heating relies on dipole rotation and ionic conduction, with limited penetration depth and risk of non-uniform heating. Ohmic requires conductive foods; microwave suffers from hot spots.
Where is heating by hot water used in the food industry?
Mainly glass containers, flexible pouches, polymer - trays glass thicker so decreased conductivity, provides lower thermal shock then steam - flexible pouches and polymer trays are thinner and therefore can increase temperature rapidly
What is hydrogen swell?
when a canned high-acid food product attacks the metal lining of the can and releases hydrogen gas.
What is the purpose of mixed air flow in spray drying?
Particle movement through the drying chamber experiences both co- and counter current phases. This mode suitable for heat stable products where coarse powder requirements cessitate the use of nozzle atomizers, spraying upward into incoming air flow, or for heat sensitive products where the atomizer sprays droplets down wards towards an integrated fluid bed and the air inlet and outlet are located at the top of the drying chamber
What are the different types of osmotic dehydration?
Impregnation soaking process, osmotic dewatering, dewatering impregnation soaking, solvent drying
Low dose irradiation acts to preserve foods by: a. forming free radicals in foods; b. causing disintegration of bacteria; c. destroying enzymes in food; d. stopping rancidity
b. causing disintegration of bacteria
What do HTST, PSIG, and CSTR stand for in food processing?
1) High Temperature Short Time 2) Pounds per Square Inch Gauge 3) Continuous Stirred Tank Reactor.
What is the unit of ionizing radiation dose in the International System of Units (SI)?
Gray
Shear forces in solids are analogous to what forces in liquids?
Viscous forces
Vegetables and fruits can be heated by microwave energy because they have a high "loss factor". The "loss factor" is mainly due to what compositional content of fruits and vegetables?
water
What are the effects of drying on stress development and cracking?
Loss of valuable product, loss of consumer satisfaction, seed reduced germination(a biopolymer during drying shrinks at the surface causing tensile stress at the surface and compressive stress on the material surface exceeds the material breaking strength,, the material cracks
Name 3 factors that contribute to the preservative actions of smoking foods.
Temperature (heat kills cells), drying and salt lower water activity, and smoke contains chemicals that are antimicrobial and antioxidants
What are the three most commonly used additives?
sugar, salt, corn syrup
Why is refrigeration combined with other methods?
Combined refrigeration with other preservatives techniques to enhance shelf life. MAS (Modified Atmosphere Storage).
Why do bubbles form in boiling and not evaporation?
Because the vapor pressure can overcome the atmospheric pressure
The extraction technique used by the meat industry to remove fats from most by-products that have no better market potential is called what?
Rendering
which laws, appearing in the general form of driving force over resistance force, describes the following processes: mass transfer, heat transfer, and electrical conductance
Mass transfer=Fick's Law; heat transfer= Fourier's Law; electric conductance= Ohm's Law
Measurement of temperature using thermocouples involves two wires of dissimilar metals. What is produced and measured when these two wires are joined and the junctions placed at different temperatures?
A (small) voltage or potential (mV)
What effect is described by a visco elastic fluid climbing an impeller shaft during mixing or agitation?
The Weissenberg Effect
In thermoprocessing, what is the difference between "sterility" and "commercial sterility"?
Sterility: free from microorganism Commercial Sterility: Free from pathogenic microorganisms and reduced levels of spoilage microorganisms that does not affect quality of a product
How many meters are in one angstrom?
1 x 10^(-10)
What are the advantages of a plate heat exchanger?
Low initial cost, high heat transfer efficiency, small hold up volume in heat exchanger, easy to inspect and disassemble unit, flexibility of the system (can be readily expanded/contracted to perform multiple duties)
The hydrolysis of a specific bond in kappa casein (phe 105 - Met 106) results in what?
Destabilization of the casein micelles (cheese curd formation)
In quality control of frozen foods, why is it more desirable to freeze a product quickly rather than slowly?
Ice crystals formed will be the smaller if the product is frozen quickly to prevent texture defects.
What is the significance of the temperature/time relationship in the processing time?
Product temperature curve shows that the product temperature at the slowest (coldest) heating location within the container increases more slowly than the heating medium temperature and the product temperature may not reach the retort temperature before the end of the process.
What is Cobalt-60 used in?
Gamma-irradiation
What does the Bernoulli equation allow us to calculate?
It is used to find the relationship between pressure, velocity, and elevation for an incompressible, inviscid fluid in steady flow
What is the simplest and cheapest method for food drying?
Sun drying
A retort temperature of 250 F is achieved with how many pounds of pressure?
15
Define specific gravity.
Specific gravity is the weight of a volume of the substance divided by the weight of an equal volume of water
What is the hot fill temperature used for glass jars?
180F
How does the Long-Tube Vertical-Rising-Film Evaporator operate?
Product exists from top. Much used in Dairy and Fruit industry.
What is the type of heat energy described when ice changes temperature from 0 F to -10 F?
Sensible heat
Name the four classes of caramel and how they are processed.
Caramel color class I: Plain caramel Caramel color class II: Caustic sulfite process Caramel color class III: Ammonia process Caramel color class IV: Sulfite ammonia process
What is food quality used to indicate?
Used as indicator to measure food during shelf life. Quality changes are less/slower when the product is dried
What three metals make up German silver, a metal historically used in food processing equipment?
Copper, Steel, and Silver
What is the relationship between dielectric constant and frequency?
as frequency increases, dielectric constant decreases
What is the latent heat of fusion?
Energy required to change a substance from solid to liquid (or vice versa) at a constant temperature
What liquid property has the greatest influence on flow characteristics?
Viscosity
Explain 'Freezer Burn'.
A condition that occurs when frozen food has been damaged by dehydration and oxidation. Usually due to substandard packaging
Ketchup exhibits what kind of flow behavior?
Pseudoplastic/ shear thinning/ Herschel-Bulkley
How many radians are there in 360 degrees?
2 pi
What is a plate type heat exchanger mainly used for?
Used for non-particulate fluids
In the early 1800's a Frenchman developed a method of preserving foods by sealing them in glass jars with a paraffined cork and heating the filled jars in boiling water. What was the name of this early food scientist?
Nicholas Appert
Name 3 natural colorants and the food from which they come from.
Annato extract: Annato seeds, Beet powder: Dehydrated beets, Paprika: ground dried mild capsicum pod, Grape color extract: Concord grapes, Turmeric: ground rhizome of Curcuma longa L.
What are the 3 regions of IR radiation?
Near-IR, mid-IR, and far-IR
What is the thermal center of conduction in in-container sterilization?
Geometric center of container
What is the forced circulation evaporator, how does it work, what is it used for?
This is for viscous fluids, liquids with suspended solids and some degree of scaling and fouling. Product is pumped at high velocity through a heat exchange section where boiling is prevented by the application of hydrostatic pressure. High velocity helps to prevent scaling and fouling and to increase heat transfer rate, absence of boiling also helps reduce scaling, capital investment and operation cost high
In Planck Distribution, At a given wavelength, what happens to the emissive power as the temperature increases?
Emissive power also increases
In the S.I. system of units, there is only one energy unit. What is it?
The Joule
List four kinds of food deterioration.
Microbial, insect & rodent, chemical, enzymatic.
In a multiple effect evaporator what term is used to calculate efficiency?
SE (steam economy). To be precise, Steam Economy is the ratio of the mass of water evaporated to the mass of steam supplied (SE = m{vapor} / m{steam}). In a multiple-effect system, the SE is roughly equal to the number of effects (e.g., a triple-effect evaporator has an SE close to 3).
Name a chart used in unsteady state heat transfer.
Gurney-lurie/ Heisler chart
What are the three sections of an extrusion screw?
Feed, compression, and metering.
What are the disadvantages of removing water from foods during processing?
Different physical appearance (excluding freeze drying), energy consuming (more expensive), and if it is heat drying there is a decrease in food quality
What term refers to the number of BTU's required to convert one ton of water at 32 degrees Fahrenheit to one ton of ice at 32 degrees Fahrenheit in 24 hours?
Ton(s) of refrigeration
What is the agitated think film tubular evaporator, how does it work, what is it used for?
For very viscous foods, feed is spread on the inside of the cylindrical heating surface by wiper blades, small heating area and high cost.
How does a bimetallic thermometer work?
there is a bimetallic strip that converts a temperature change into a mechanical displacement. There is a mechanical displacement because the strip is formed from two different metals that expand at different rates when heated
How many kPa is one atm?
101.3
Why is a rotating retort used for the thermal processing of canned soups?
The rotation causing mixing of the soup in the can and promotes even heating during the thermal processing
Which statement is False about food irradiation: A.destroys harmful bacteria that cause food spoilage/human disease, B.foods are better preserved during storage, C. makes food radioactive, or D.involves exposing food to 1 of 3 types of ionizing energy.
C. makes food radioactive
What are the factors to consider in the design of a continuous pasteurizer?
Thermal design (calculation of exit temperature of food and calculation of total surface area, # of plates etc) Structural design( strength of plates) Fluid mechanics (operating pressure and velocity profile of fluids) Microbial and nutrient aspects (selection of pasteurization temperature and time)
How are food categories classified based on pH?
Low acid over 4.5 Medium acid and acid 3.7 to 4.5 High acid below 3.7
What is roll feeding for drum drying?
Used in single and twin drum, effective for viscous and glutinous materials, multirolls used to increase film thinkness, gap adjusted bwn rolls and drum, sometimes used combination with other methods
Describe the TDT curve, what are the axes, the slope?
The x axis is temperature and the y axis is thermal death time. Z value = 1/slope of thermal death time vs temperature
What type of heat exchanger is commonly used in pasteurization of milk?
Plate heat exchanger.
A liquid with a Reynold's number of 1000 is exhibiting what type of flow?
Laminar
What rheological model best describes the flow behavior of melted chocolate?
The Casson or Casson/Steiner model (the Windhab model is also acceptable and recommended by the IOCCC as of 2000)
What type of sensors have resistance characteric fall off with increasing temperature?
Negative temperature coefficient
Describe the plot of the sheer force vs viscosity for the following: Newtonian, Pseudoplastic, Thixotrophic
Newtonian: Viscosity remains constant with sheer force; Pseudoplastic: Viscosity decreases with increasing shear stress; Thixotropic: Viscosity decreases over time under constant shear stress
Which of the following four choices is considered the least severe thermal processing method for foods? a. sterilization; b. pasteurization; c. commercial sterilization; d. blanching
d. blanching
What is the main purpose of food processing?
To extend shelf life of a product by reducing or eliminating microbial activity and ensure food product safety
What are the 3 main components of a microwave heating system?
Magnetron, waveguide, and cavity
List three advantages of intermediate moisture foods.
Refrigeration is not required, spoilage is slower, relatively cheap and energy efficient
How do you calculate lethality?
Area under the curve of time vs lethal rate
If the D value of the critical organism is three and the product is a high acid food, what should the F value of the process be?
F = 15 (=5D) (accept 15, 18 or 21).
Turbulent flow is characterized by NRE = _______________
rho.v.D/nu (rho = density, v = flow velocity, D = orifice diameter, nu = viscosity)
What is the freezing method used in ice-cream making?
Scrapped surface
What is the processing involving heat for cocoa beans to brew?
Roast
What is the purpose of Acidity Control in processing?
The more acid present in a food, the lower the pH becomes, lowering the potential of microbial spoilage, and requires less heat treatment
Name 3 enzymes required to produce high fructose corn syrup.
Alpha-amylase, glucoamylase, glucose isomerase
What is the boiling point definition?
The temperature at which the vapor pressure becomes equal to the atmospheric pressure (760 nm)
What are some ways to heat process food?
Retort, aseptic, pasteurize, blanch, hot fill
In separations such as distillation what is the name of the plot used by engineers to describe the physical state at each step?
McCabe-Thiele plot
Discuss the principle of HTST processing and why it is used.
By heating food at a high temperature and short time, many desirable nutrients and sensory components can be retained but many undesirable microorganisms and enzymes can be destroyed. It is based on the principle of different z values for vitamins and bacteria
What type of electronic radiation is emitted by Cobalt-60 and used to irradiate foods?
Gamma rays
What is flash cooling?
The process of removing heat, moisture, and entrained air from the product prior to filling
What is the critical Reynolds Number for tube flow?
2100
What is an example of a newtonian fluid? Ketchup, oil, mayonnaise, honey
Oil
What is the can defect 'paneling' caused by?
Excessive external pressure during cooling compared to internal can pressure, resulting in deformation of the can body.
What parameter is held constant to determine the D-value?
Temperature
What is Just noticeable difference (JND) in frozen foods?
Just noticeable difference (JND): defined as the length of time for a panel of human subjects to distinguish the product being evaluated from the same product held at a reference temperature (typically -35º C).
Describe the meaning of 150-grade pectin.
A 150 grade pectin is one that will form a satisfactory gel at a ratio of 1 kg (or unit) pectin to 150 kg (or unit) sugar.
Define coextrusion
The process of extruding 2 or more materials through a single die with 2 or more orifices arranged so that the extrudates merge or weld together into a laminar structure.
What is thermal vapor recompression?
As a way to reduce energy consumption a thermocompressor which uses high pressure steam as a motive fluid is added to a typical steam heated evaporator. The motive steam at approximately 150 psig enters the thermocompressor and expands as it passes through a diffuser=
When making extra virgin olive oil what is the maximum number of hours required from harvest to processing?
24
What is the purpose of doing exhausting?
To prevent air expansion with heat, removes container distortion. Removal of O2 prevents internal corrosion in containers and prevents oxidative changes in foods.
What is the primary preservation mechanism in freeze-drying?
Removal of water by sublimation, lowering water activity
Caramel coloring is mostly used in what food?
Beer
Approx. how many BTU's are required to change 1lb of water to steam at one atm and 212F?
~1000 (970.6)
What is aseptic processing?
Food and container are sterilized separately and then filled in a sterile environment
What are the components of a super critical fluid extraction system?
Solvent compressor or pump, an extractor, temp/pressure control system, a separator/absorber
What does a correlation coefficient define?
a statistical measure of the strength of a linear relationship between two variables
What is the function of the Bostwick consistometer?
Measures consistency of tomato products
In extrusion, which surface is rough and which one is smooth? Inside surface of barrel or outside surface of screw?
The inside surface of barrel is rough and outside surface of screw is smooth.
With conductive heat transfer, the cold point of a can to be thermally processed is where?
At the geometric center
In a closed vessel, what happens to the density of gas when the temperature changes?
The density of gas stays the same
In fluid dynamics, what dimensionless number represents the ratio of inertial forces to viscous forces and is used to determine whether a fluid flow is laminar or turbulent?
Reynolds number (Re)
What is tempeh?
A fermented Indonesian soybean product made with Rhizopus oligosporus.
What are the effects of drying on shrinkage?
Shrinkage (reduction in volume due to moisture loss): biopolymers cannot support their weight in the absence of water, gravity causes to shrink, collapse of cell walls and from gel-like to fibrous, important phenomenon impacting dried food quality (reducing wettability, changing texture, decreasing product absorbency) isotropic anisotropic(fish and seafood, fruit and veg)
Rank the following pulse waveforms used in pulsed electric field processing in order of increasing electrical efficiency: oscillatory, square wave, exponentially decaying
Square wave, exponentially decaying, oscillatory
What non-thermal technology uses electric fields to inactivate microbes?
Pulsed electric fields.
What are the stages of drying?
A-B: initial settling down period to heat up the product and water. B-C: constant rate period; free water vaporization at surface, surface temp=wbTemp, external controlled-the resistance to heat and mass transfer is located solely in air stream, constant rate. C-D: falling rate period; no free water at the product surface, internal moisture has to migrate to surface, if diffusion the drying rate is controlled by the rate of diffusion inside the product, drying rate decreases. D-E: second falling rate period; bound water removal
What gas is used to pasteurize spices?
Ethylene oxide
What is the purpose of a plate heat exchanger in milk pasteurization?
To rapidly heat and cool milk for efficient pasteurization while conserving energy through heat recovery.
What are the 2 principal methods employed in peeling potatoes?
Abrasion and lye.
In canned vegetable processing, peroxidases are used as an indicator of adequacy of which process?
Blanching
What are the different types of evaporators?
Batch pan, tubular evaporators (natural circulation, rising film, falling film, rising falling film, forced circulation evaporator, agitated thin film [wiped film]) plate evaporators ( rising falling, falling, parvap, paraflash
Single drum, double drum, and twin drum are all types of what?
(drum) Driers
Which gas often removed from packaging in thermal processes?
O2
What is the SI unit for density?
Kg/m3
Of the four options, which would be the most versatile piece of equipment which can be used for both dry and moist heat cooking in foodservice operation? a) convection steamer (pressureless steamer); b) tilting skillet (tilting brazier); c) Steam Jacketed Kettle; d) Conveyor oven with infra-red impingers
b) tilting skillet (tilting brazier)
What are the factors that affect in-container sterilization time?
Type of product, size of containers, agitation of container, retort temp, type of container, heat resistance of microbes and enzymes, pH of foods
What is standard atmospheric pressure in kiloPascals?
101 kPa
Which dimensionless number can be used as an index of laminar or turbulent flow?
Reynold's number
Full form of PEF in food processing.
Pulsed Electric Field
What type of heat exchanger is most commonly used for the freezing of ice cream?
Scraped surface heat exchanger
What is Liquid oxidation and how does it relate to Maillard Browning?
1. Liquid oxidation - causes an oxidized flavor or rancidity. - Vacuum packaging, antioxidants, inhibitors, and modified atmosphere storage can prevent or inhibit liquid oxidation. 2. Maillard Browning - chemical reduction between reducing sugars and proteins leads to the brown color.
Describe the steps in the high-temperature short-time (HTST) pasteurization of milk.
Milk is heated to 72°C (161°F) for 15 seconds → immediately cooled to ≤10°C → held in sterile tanks → packaged aseptically.
What salt is traditionally used to coagulate tofu?
Calcium sulfate
What are the four methods used for peeling potatoes and apples?
Mechanical, Heating (blanching), Lye peeling, Dry caustic peeling
What two metal wires compose a T-type thermocouple?
Copper and constantan
What equipment is preferred to sterilize canned soups?
Rotary retort
What is the major stumbling block for the growth of food irradiation?
Consumer acceptance
What are the types of pasteurization methods?
Batch type and continuous type
What are the 2 most common approved sources of gamma rays in food irradiation?
Cobalt-60 and Cesium-137
A batch of juice is being heated from 25 C to 90 C. Given the specific heat capacity (Cp) of the juice is 4.0 kJ/kg.K, calculate the heat (Q) required to raise the temperature of 150 kg of the juice.
Q = m.Cp.deltaT where m=150 kg, Cp=4.0 kJ/kg.K, and Delta T = 90 C - 25 C = 65 C (or 65 K). Q = 150 kg x 4.0 kJ/kg.K x 65 K= 39,000 kJ (or 39 MJ).
What are the two roles of salt in bread making?
Changes taste, effects rheological properties by making dough stronger
What happens in the freezing phase?
Freezing: to freeze mobile water of product, (fast freezing small ice crystals and slower drying, slow freezing large ice crystals and faster drying)
What are some of the advantages of a tubular heat exchanger?
Few gaskets, low maintenance costs, compact units, no moving parts
What are the two types of heat transfer important in retort processing?
Convection and conduction
Name 3 types of driers
Freeze dryer, tray drier, drum dryer
What are the components of a spray drying unit?
Feed tank, high pressure pump, air heater, nozzle atomizer, drying chamber, inlet duct, primary product collector, secondary product collection, main cyclone, exhaust fan
Name two direct and two indirect methods of thermal processing.
Direct: steam injection, steam infusion, baking, frying, microwave cooking, retorting; Indirect: plate heat exchange, scraped surface heat exchange, tube type heat exchange.
What are the names of time-dependent liquids that obtain a constant apparent viscosity only after a finite time has elapsed after application of shear?
Thixotropic; Rheopectic
Why is freeze drying different from other forms of drying?
Water sublimes from ice to the vapor phase
Which of the following is the SI unit for viscosity? (a) N-m (b) Pa-s (c) N/m (d) J/ K
(b) Pa-s
What is the advantage of traditional thermal processing over non-thermal processing in terms of survival of pathogens?
Thermal processing can destroy spores
Which dimensionless number relates momentum diffusivity to thermal diffusivity?
Prandtl number.
For any canning process, a curve of the temperature versus the time can be created. The sterilization process is complete and adequate when the integral under the curve equals what?
The F-value needed for that process
Describe the difference between HTST pasteurization and UHT processing.
HTST (High-Temperature Short Time): ~72°C for 15 sec, extends shelf life for days to weeks under refrigeration. UHT (Ultra-High Temperature): ~135°C for 1–2 sec, produces commercially sterile product with months of shelf life unopened.
To be called peanut butter the product must contain 90% peanuts. Name 3 items used as the other 10% of peanut butter.
Salt, sugar(sweetener) hardened vegetable oil, or emulsifier
What does "STP" mean, and what are its values?
Standard Temperature and Pressure: 14.7 psia or 760 mm Hg and 0°C
Name four types of commercial thermal processing.
Dry oven, steam retorting, HTST, UHT, aseptic, hot fill, frying, flaming, baking, broiling
What's the equation for Planck-Einstein relation with respect to radiation?
E = h (nu) = h.c/(lambda)
What is the importance of evaporation?
One of the big reasons is that we want to minimize the material that we have to ship, for example orange juice, you can ship a lot more as concentrate than as juice, saving lots of money on shipping and space for storage.
How does the Long-Tube Vertical Falling Film Evaporator operate?
Product flows downwards. Used in Dairy and Fruit industry.
Discuss membrane concentration of liquid foods.
Based on ability of semipermeable membranes of appropriate physicals and chemical nature to discriminate between molecule primarily on the basis of size and to a lesser extent on shape and chemical composition. A membranes role is to act as a selective barrier enriching certain components in a feed.
What are some of the advantages and disadvantages of microwave heating?
Advantages: Higher heating rates; no direct contact between the heating source and the heated material; selective heating may be achieved; greater control of the heating or drying process; reduced equipment size and waste Disadvantages: Radiation; the texture of food, color, and taste will change
What chart is used to estimate heat penetration during canning?
Ball’s process time chart.
List three positive effects of properly used thermal processing on the nutritive value of foods.
Improves digestibility, inactivates degradative enzymes, inactivates antimetabolites
Describe the winterization process for oils.
The oil is cooled and then solids are filtered so that the long-chained saturated fats do not crystalize at low temperatures
Full name of BDA?
Bone dry air.
Name four basic principles of food processing.
1) Moisture removal 2) Heat treatment 3) Low-heat treatment 4) Thermal processing 5) Nonthermal processing (traditional & nontraditional) 6) Acidity control
What is the process of addition of hydrogen to unsaturated fatty acids?
Hydrogenation
Name the process whereby a food is heated under vacuum at temperatures sufficient to cook and pasteurize the product but not sufficient to sterilize it?
Sous-Vide (French for "Under vacuum")
What is the graph of water activity vs. water content called?
Moisture sorption isotherm (MSI)
Which of the following modes of heat transfer are used in the retort: A.conduction, B.Convection, or C.Radiation?
A. Conduction and B. Convection
In the SI system (Systeme International d'Unites) what are the units applied to the following seven dimensions or measurements? Length, Mass, Time, Electric current, Thermodynamic temperature, Amount of substance, Luminous intensity.
Length-Meter; Mass-Kilogram; Time-Second; Electric current-Ampere; Thermodynamic temperature-Kelvin; Amount of substance-mole; Luminous intensity-candela
Food radiation is capable of destroying all the following in foods except, A. microrganisms, B. bacteria, C. viruses, D. insects, E. prion
Prion
What is D value? What are the units?
It stands for decimal reduction time, time taken to reduce the no. of microbes by 90% or 1 log. D value has units of time
What is Newton's First Law?
Every body persists in its state of rest or motion in a straight line unless acted upon by a force.
What is the term referring to the ratio of mass and volume?
Density
Which heating technology strongly depends on presence of polar molecules?
Microwave cooking
Name one of the two truly cryogenic freezing media used in freezing fruits and vegetables.
Liquid nitrogen or dry ice
What is the principle of exhausting?
Gases occupy greater volume at a higher temperature (apply heat increase air volume, seal container, cool , create partial vacuum
What is the science of flow and deformation of materials under pressure?
Rheology
What is Irradiation considered to be?
Food additive
Name 2 chemical agents used to accelerate bleaching of wheat flour.
Chlorine dioxide (widely used), and benzoyl peroxide
What is exhausting?
Removal of air from headspace of container
What equation can be used to relate the effect of a frictionless fluid flow through pipes to a pressure drop?
Bernoulli Equation
Why do we need vacuum in canned foods?
Loss of gases from tissues, container stability, exclusion of oxygen from headspace, and prevention of buckling during the retort process
Define the Biot number.
Dimensionless quantity used for heat transfer calculations. The ratio of the heat transfer resistance inside of and at the surface of the body.
What is the minimum product temperature necessary for expansion of an extruded material?
100?C (In order for expansion to occur, moisture in the product must be able to flash-vaporize)
What is Low-Temperature Treatment used for?
Done to a) slows spoilage reactions b) freezes the water in food to reduce aW i.e. refrigerating
What are some of the benefits of a thermistor?
They are preferable in simple applications due to their low cost and simple electronic circuitry, also they can be produced in very small designs with a fast response and low thermal mass
What factors can influence microbial growth during refrigeration?
- Initial micro population - Characteristics of the food - Effect of processing - Refrigeration temp - Refrigerator load/ capacity
What is the purpose of a deaerator in an aseptic processing system?
To remove air and prevent lipid oxidation as the product temperature is increased during the process
Why is stannous chloride added to asparagus canned in glass jars, and how much is allowed?
1) It controls discoloration due to oxidation of rutin 2) Not more than 15 ppm in glass containers with unlined metal lids; 20 ppm with inert, lined lids.
What is the major rheological property that distinguishes a Newtonian fluid from a Bingham plastic fluid?
A yield stress. (A Bingham plastic fluid has a yield stress and a Newtonian fluid does not. If the contestant has described the difference to the judges' satisfaction without actually saying "yield stress", the answer may be accepted)
What are two reasons for adding salt in vegetable fermentations?
Leach out nutrients, inhibit competitive bacteria, inhibit degradative enzymes
Why are the first small crystals remelted and recrystallized in freeze concentration?
Bc melting required the addition of heat and changing from solid to liquid. Known as ripening and forms the heart of separate nucleation and growth process
Resistance temperature detectors, also known as RTD are PTC sensors. What does PTC stand for?
Positive temperature coefficient
With respect to distillation, what is a vaporize/condensation stage called?
A theoretical plate
In southeast Asian cuisine, Caramel color is added to
Soy Sauce
What types of containers are used in retorts?
Metal cans, glass jars or bottles, flexible pouches, ridged trays
Name 8 of the 12 methods to preserve foods.
Pickling, salting, smoking, canning, bottling, pasteurization, refrigeration, sterilization, dehydration, lyophilization, chemical additives, radiation
What is relative humidity?
RH Φ=(mole fraction water)/(mole fraction water saturated )100=(pressure h2o vap)/(press sat h2o vap)100 how close the air is to saturation
What are the advantages of using Reverse Osmosis (RO) and Ultrafiltration (UF)?
Advantages of using membranes: - Low temperature - Lower costs - Lower floor requirements.
If convection heating predominates during thermal processing of a canned food product, where is the cold spot located with respect to the can geometry?
At the center point 1/3 of the way up from the bottom of the can
Material and energy balances take the general form of total mass in equals total mass out, or total energy in equals total energy out. In continuous processes, what additional aspect is added to the balance?
Time (mass per time in equals mass per time out)
With respect to thermal processing, what term (or symbol) is defined as the number of equivalent minutes at a temperature of 250 F delivered to a container or unit of product calculated using a z-value of 18 F?
F sub zero, Sterilization process equivalent time
What is the frequency range for infrared radiation?
430 THz down to 300 GHz
What effect does the physical state of the food have on processing time in in-container sterilization?
Physical state (liquid, solid, suspended particle, paste) conduction in solids and liquids and pastes, convection in liquid
What is the pressure (in kPa) of apple juice that is held at a 10m high tank assuming the density of 1kg/m3?
Density x gravity x height= 1 x 9.81 x 10= 98kPa
A number 16 scoop is equal to how many ounces?
2 oz
What are the disadvantages of osmotic dehydration?
Longer drying times, leaching of natural acids, floating of food pieces and necessity for agitation, disposal of used osmotic medium high of BOD, lack of knowledge of microbial development in medium and products, reduction in acidity levels of fruits, substantial modification of original product composition (flavor)
What are three types of food containers commonly used in retorting?
Metal containers (cans), glass containers, retort pouches
Which enzyme is deactivated in the "hot break" process in juice production?
Pectinmethylesterase
Term for temp at which Vapor Press = press of surrounding?
Boiling pt
why would a manufacturer add egg white or glycerol monostearate to a pasta formulation?
Increases firmness, decreases loss during cooking, reduces stickiness
What is the Ohm Law?
V = iR
Which kind of thermal couple is used in thermal processing, which is in high pressure, and which is in extrusion?
Type T, K, J
What is the Weissenberg effect?
The tendency of some viscoelastic fluids to climb up a rod that is rotating in them. (fluid flows in a right angle to the direction of shear stress)
What processing strategy is being explored to reduce acrylamide formation without altering sensory quality?
Enzymatic asparaginase treatment.
What is commercial under counter refrigerator known as?
Low Boy
What device is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field?
Magnetron
What are the advantages of freeze concentration?
Freeze concentration operating at subzero and is a closed system: No loss of aromas or other volatile components, Retention of all sensory properties of the original feed product, No thermal degradation, Minimized oxidation, No loss of solids, The process is specifically interesting for the treatment of heat sensitive substances and for all applications where maximum retention of a product quality is a key aspect
Describe the basic principle of freeze-drying and its advantage over conventional drying.
Freeze-drying (lyophilization) removes water by sublimation under vacuum at low temperatures, preserving flavor, nutrients, and structure better than conventional drying.
Name 3 types of heat treatment during food processing and what is their purpose.
Blanching (inactivates enzymes), pasteurization (kill pathogenic bacteria), and sterilization (kill all bacteria and other organisms)
What food characteristics influence microwave heating?
Dielectric properties, thermal properties (specific heat), size and shape of food, food orientation in microwave, physical state of water (ice and water), moisture content, salt content, oil content
What is Latent heat or hidden heat?
Latent heat or hidden heat (λ): is defined as the amount of heat energy transferred to or from a material and results in phase change only without changing its temperature.
Name 2 types of dielectric heating.
Radio frequency and microwave heating
Name two substances that may be used for commercial caffeine extraction?
Methylene chloride or supercritical carbon dioxide or water
Thermistors are NTC sensors. What does NTC stand for?
Negative temperature coefficient
What are 2 major contributions of chemicals released as smoke from burning wood during smoking?
Flavor enhancement and Preservation
In thermal processing (specifically heat penetration) what is the symbol or ratio term used to relate the actual initial temperature of the product to the intercept temperature?
J, lag factor
What was the name of the first aseptic packaging system?
The Dole system
Explain what is meant by aseptic processing.
The food and container are sterilized separately and are filled in a sterile environment
Name 5 ways that processors can reduce the microbial population or growth of microoragnisms in a food product.
Heat treatment, refrigeration (or decreasing temperature), decrease water activity, removing contaminated portions (or trimming), using chemicals (accept both addivitves and sanitizers, such as chlorine), encouraging the growth of fermentation microorganisms, minimizing contamination, cleaning and sanitization of equipment and facilities, etc.
What is extracted from coffee beans using supercritical fluid extraction?
Caffeine
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