Chapter 19: Thermal Preservation: Hot and Cold Processing
These flashcards outline methods of food preservation through heat and cold processing, including cooking, refrigeration, and pasteurization. They highlight how these techniques destroy or slow down harmful microorganisms and enzyme activity to extend shelf life and ensure safety.
What is heat processing?
transfers heat energy into food and destroys
enzymes and bacteria (microorganisms) that cause spoilage and contamination
Key Terms
What is heat processing?
transfers heat energy into food and destroys
enzymes and bacteria (microorganisms) that cau...
What is cold processing?
pulls heat energy from food to slow molecular movement, thus slowing spoilage
Cooking extends shelf life as long as what?
As the food is also packaged to prevent recontamination
What is pasteurization?
low-heat treatment that destroys pathogenic microorganisms and stops enzyme activity
What products are pasteurized?
Beer, wine, fruit juice, milk, oysters, and eggs
The processing time and temperature depends on what?
depend on the microorganisms and enzymes in a food
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| Term | Definition |
|---|---|
What is heat processing? | transfers heat energy into food and destroys enzymes and bacteria (microorganisms) that cause spoilage and contamination |
What is cold processing? | pulls heat energy from food to slow molecular movement, thus slowing spoilage |
Cooking extends shelf life as long as what? | As the food is also packaged to prevent recontamination |
What is pasteurization? | low-heat treatment that destroys pathogenic microorganisms and stops enzyme activity |
What products are pasteurized? | Beer, wine, fruit juice, milk, oysters, and eggs |
The processing time and temperature depends on what? | depend on the microorganisms and enzymes in a food |
Batch pasteurization is best with what? What is batch pasteurization? |
- Heated in a large vat with slow stirring, pumped over a cooling plate, then packaged and sealed |
What does high temperature-short time pasteurization (HTST) do? |
- Liquids are pumped through heat exchangers, then cooling tubes, and immediately packaged and sealed |
HTST milk is heated to what temperature? For how long? | 72oC for 15 seconds |
UHT milk is heated to what temperature? For how long? | 140oC for 4 seconds |
Is UHT processing of milk pasteurizing? What does this process allow? | NO, it is sterilizing - Lets consumers store milk or juice for several months without refrigeration |
What is commercial sterilization used for? What does it destroy? | – is used for canned foods in sealed containers |
What do sealed cans prevent? | Recontamination and growth of any spores that may be present |
What does sterilization destroy? How is it accomplished? What is it limited to? |
|
What temperature are foods subjected to in sterilization? | 121oC for 15 minutes |
What does aseptic mean? | Free of pathogens |
What does aseptic canning involve? How is it done? | involves sterilizing the food, placing it in sterilized containers, and sealing the containers |
What are retorts? | Large commercial pressure canners with special locks and valves |
What is the difference between still and agitating retort? |
|
What is the goal of thermal processing? | add enough heat energy to preserve a food product while maintaining as many original qualities as possible |
When is heat transfer by conduction used? | when food does not move in the container, such as corned beef hash, pumpkin pie filling, and tomato paste |
Is heat transfer by conduction or convection slower? | Conduction is slower because of less molecular motion in more-viscous food |
When is heat transfer by convection used? How does this process work? |
|
What is the cold point? | the last point in a can or mass of food to reach the desired temperature |
Where is the cold point located when heating by conduction? | In the center of the can |
Where is the cold point located when heating by convection? | Just below the center of the can |
What is the thermal death curve? | the line plotted on a graph showing the time needed to destroy pathogens at a given temperature |
The lower the temperature, the longer the _ | cooking time |
How does sugar, starch, protein, fats and oils affect the heat-processing method? | interfere with wet heat penetrating the food |
How does fat affect the heat processing method? | Slow the conduction process |
Name 3 factors to consider when choosing a heat-processing method. | 1) Safety (destroying microbes) |
What are the 4 levels of heat preservation? |
|
What is a method to heat food after packaging? | With a retort |
What is a method to heat food before pasteurization? | Pasteurization | aseptic canning |