Food Processing and Engineering

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

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

What are some of the internal conditions that affect drying?

Properties of food, thermo conductivity, density, porosity, aw, sorption isotherms

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 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.

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 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

Name 3 sanitizers commonly used in food processing.

Quats (quaternary ammonium compounds), chlorine, iodophores

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.

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

What is co-current operation?

Rapid initial drying, inefficient heat transfer at end of drying, formation of internal splits of porosity

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 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 the 4 purposes of evaporation industry?

Reduce the volume of a product Preconcentrate a liquid Increase solid content in food Reduce the microbial load

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

List three advantages of intermediate moisture foods.

Refrigeration is not required, spoilage is slower, relatively cheap and energy efficient

What three parameters determine hold tube length?

Residence time, system flow rate, hold tube internal diameter

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.

Name 4 types of membrane separation systems.

Reverse Osmosis, nanofiltration, ultrafiltration, microfiltration

Turbulent flow is characterized by NRE = _______________

rho.v.D/nu (rho = density, v = flow velocity, D = orifice diameter, nu = viscosity)