Food Processing and Engineering

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 the four phases of Refrigerated storage?

Commercial storage Transport storage Retail storage Home storage.

Name the 4 steps of refrigeration.

Compression, condensation, expansion, evaporation

Name the four basic components of a mechanical refrigeration system.

Compressor, condenser, evaporator, expansion valve

What are four parameters which affect the efficiency of lye peeling operations?

Concentration of lye; Time; Temperature of solution; Lye and peel removal systems

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).

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).

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).

Name 3 necessary elements of proper refrigeration.

Constant temp, humidity control, and air circulation

What factors affect heat penetration in canned foods?

Container size/shape, product consistency (homogenous or not), type of retort (still vs agitating)

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.

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.

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 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 four variables used when calculating the Reynolds number of a fluid?

D = pipe diameter, V = mean fluid velocity, ρ = mass density, μ = fluid viscosity.

What changes occur in quality during food processing?

Degradation of pigments Loss of vitamins Enzyme activity Oxidation of lipids.

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)

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

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

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