Food Processing and Engineering

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)

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.

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

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 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

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.

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.

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 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 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

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.

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.

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.

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

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.

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.

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)

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 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 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