Food Processing and Engineering

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 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)

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.

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 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

How does the process of freeze drying preserve food?

Lowered water activity, vacuum application

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

Explain the steps of freeze drying.

Lyophilization, freezes food then puts it through a vacuum, this evaporates solid frozen food, sublimation dries the food.

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

What are the 3 main components of a microwave heating system?

Magnetron, waveguide, and cavity

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

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 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)

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

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

Give three examples of classes of foods which are low acid.

Meats, seafood, vegetables (except tomatoes), some fruits.

What are the four methods used for peeling potatoes and apples?

Mechanical, Heating (blanching), Lye peeling, Dry caustic peeling

Name the three methods of producing a vacuum in cans.

Mechanical, thermal, or live steam injection

What are the pre-fixes for million, billion, and trillion?

Mega, Giga, Tera (10^6, 10^9, 10^12)

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