Chapter 19: Thermal Preservation: Hot and Cold Processing

Question 1

What is Thermal Preservation?

Answer 1

Thermal Preservation of food involves changing its temperature

Question 2

What is Heat Processing?

Answer 2

Transfer heat energy into food and destroys enzymes and bacteria that cause spoilage

Question 3

What is Cold Processing?

Answer 3

Pulls heat energy from food to slow molecular movement, thus slowing spoilage

Question 4

What is the Goal of Food Preservation?

Answer 4

Goal of food preservation is o increase the shelf life of a food

Question 5

Heat does what to enzymes?

Answer 5

Heat denatures enzymes and destroys microorganisms that lead to food spoilage and contamination

Question 6

Cooking does what for Shelf Life?

Answer 6

Cooking Extends shelf life as long as the food is also packaged to prevent recontamination

Question 7

What is Pasteurization?

Answer 7

is a low-heat treatment that destroys pathogenic microorganisms and stops enzyme activity

Question 8

What are some examples of foods that are Pasteurized?

Answer 8

Beer, wine, fruit juice, milk, oysters and eggs are pasteurized
- Processing time and temperature depend on the microorganisms and enzymes in a food

Question 9

What is Batch Pasteurization?

Answer 9

Batch Pasteurization is best with liquids; they are heated in a large vat with slow stirring, pumped over a cooling plate, then packaged and sealed

Question 10

What is High Temperature-short time Pasteurization (HTST)?

Answer 10

it rapidly heats and cools liquids;liquids are pumped through heat exchangers, then cooling tubes, and immediately packaged and sealed

Question 11

What happens to HTST milk?

Answer 11

It is forced between metal plates or through pipes heated on the outside by hot water and milk is heated to 72C (161F) for 15 seconds

Question 12

Ultra high-temperature (UHT) sterilization means what?

Answer 12

Ultra high-temperature (UHT) sterilization holds the milk at a temperature of 140C for 4 seconds

• During UHT processing milk is sterilized and not pasteurized
• This process lets consumers store milk or juice for several months without refrigerations

Question 13

What is Commercial Sterilization?

Answer 13

1. Is used for canned foods in sealed containers
2. Is a method used commercially as well as for foods canned at home
3. Destroys all microorganisms that cause illness, produce toxins, or result in spoilage

Question 14

Sealed cans prevent what?

Answer 14

Sealed cans prevent recontamination and growth of any spores that may be present

Question 15

What is Sterilization?

Answer 15

it destroys microorganisms completely, is accomplished by moist heat and is limited to pureed or liquid foods

Question 16

For Sterilization what temperature should food be at?

Answer 16

All parts of all food must reach 121C for 15min

Question 17

What does Aseptic mean?

Answer 17

Aseptic means free of pathogens

Question 18

What is Aseptic Canning?

Answer 18

1. Involves sterilizing the food, placing it sterilized containers, and sealing the containers
2. Can be used for a wide range of container sizes and packaging materials

Question 19

What are Retorts/

Answer 19

Retorts are large commercial pressure canners with special locks and valves

Question 20

For the Retorts process what is monitored?

Answer 20

Temperature and pressure are monitored during the heating process

Question 21

What are Still Retorts?

Answer 21

Since cans of food do not move in a still retort, food is more likely to burn, therefore temperature is limited

Question 22

What are Agitating Retorts?

Answer 22

Agitating retorts gently shake cans during processing

Question 23

Heat changes what?

Answer 23

Heat changes texture, flavour and nutritive value of foods

- Goal is to add heat energy to preserve a food product while maintaining as many original qualities as possible

Question 24

What is Heat Transferred by Conduction?

Answer 24

Used when food does not move in the container, such as corned beef hash, pumpkin pie filling and tomato paste
- Size and shape of container are important considerations

Question 25

What is Heat Transfer by Convection?

Answer 25

sets up currents in liquids that speed the transfer of heat energy; is used for liquids, purees and chunks of food suspended in liquid
- Time and temperature are based on the size of the food chunks

Question 26

What is the Cold Point?

Answer 26

the last point in a can or mass of food reached the desired temperature

Question 27

Where is the Cold Point located when being heated by conduction?

Answer 27

Located in the centre of the can when heating by conduction

Question 28

Where is the Cold Point located when being heated by convection?

Answer 28

Located just below the centre of the can when heating by convection

Question 29

What are some time versus temperature considerations?

Answer 29

Balance the destructive effects of heat on the pathogens against those on food products

Question 30

What is the Thermal Death Curve?

Answer 30

is 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 needs to be

Question 31

Food Components affect the heat-processing method because of?

Answer 31

1. Potential microorganisms, ingredients, particle size, and food density must be considered
2. The temperature needed to destroy microbes varies
3. Sugar, starch, protein, fats, and oils interfere with wet heat penetrating the food

Question 32

What are some ingredients that slow the conduction process?

Answer 32

Some ingredients, such as fat, slow the conduction process

Question 33

As the density and particle size increases what also increases?

Answer 33

As the density and particle size increase, processing time also increases

Question 34

What are some Factors to consider when choosing a heat-processing method?

Answer 34

1. Safety: deciding which method will destroy harmful microbes
2. Food Quality: Deciding the treatment that will destroy microorganisms while maintaining the highest food quality possible
3. Cost: completing a cost study