Chapter 19: Thermal Preservation: Hot and Cold Processing Flashcards
What is Thermal Preservation?
Thermal Preservation of food involves changing its temperature
What is Heat Processing?
Transfer heat energy into food and destroys enzymes and bacteria that cause spoilage
What is Cold Processing?
Pulls heat energy from food to slow molecular movement, thus slowing spoilage
What is the Goal of Food Preservation?
Goal of food preservation is o increase the shelf life of a food
Heat does what to enzymes?
Heat denatures enzymes and destroys microorganisms that lead to food spoilage and contamination
Cooking does what for Shelf Life?
Cooking Extends shelf life as long as the food is also packaged to prevent recontamination
What is Pasteurization?
is a low-heat treatment that destroys pathogenic microorganisms and stops enzyme activity
What are some examples of foods that are Pasteurized?
Beer, wine, fruit juice, milk, oysters and eggs are pasteurized
- Processing time and temperature depend on the microorganisms and enzymes in a food
What is Batch Pasteurization?
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
What is High Temperature-short time Pasteurization (HTST)?
it rapidly heats and cools liquids;liquids are pumped through heat exchangers, then cooling tubes, and immediately packaged and sealed
What happens to HTST milk?
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
Ultra high-temperature (UHT) sterilization means what?
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
What is Commercial Sterilization?
- Is used for canned foods in sealed containers
- Is a method used commercially as well as for foods canned at home
- Destroys all microorganisms that cause illness, produce toxins, or result in spoilage
Sealed cans prevent what?
Sealed cans prevent recontamination and growth of any spores that may be present
What is Sterilization?
it destroys microorganisms completely, is accomplished by moist heat and is limited to pureed or liquid foods
For Sterilization what temperature should food be at?
All parts of all food must reach 121C for 15min
What does Aseptic mean?
Aseptic means free of pathogens
What is Aseptic Canning?
- Involves sterilizing the food, placing it sterilized containers, and sealing the containers
- Can be used for a wide range of container sizes and packaging materials
What are Retorts/
Retorts are large commercial pressure canners with special locks and valves
For the Retorts process what is monitored?
Temperature and pressure are monitored during the heating process
What are Still Retorts?
Since cans of food do not move in a still retort, food is more likely to burn, therefore temperature is limited
What are Agitating Retorts?
Agitating retorts gently shake cans during processing
Heat changes what?
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
What is Heat Transferred by Conduction?
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
What is Heat Transfer by Convection?
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
What is the Cold Point?
the last point in a can or mass of food reached the desired temperature
Where is the Cold Point located when being heated by conduction?
Located in the centre of the can when heating by conduction
Where is the Cold Point located when being heated by convection?
Located just below the centre of the can when heating by convection
What are some time versus temperature considerations?
Balance the destructive effects of heat on the pathogens against those on food products
What is the Thermal Death Curve?
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
Food Components affect the heat-processing method because of?
- Potential microorganisms, ingredients, particle size, and food density must be considered
- The temperature needed to destroy microbes varies
- Sugar, starch, protein, fats, and oils interfere with wet heat penetrating the food
What are some ingredients that slow the conduction process?
Some ingredients, such as fat, slow the conduction process
As the density and particle size increases what also increases?
As the density and particle size increase, processing time also increases
What are some Factors to consider when choosing a heat-processing method?
- Safety: deciding which method will destroy harmful microbes
- Food Quality: Deciding the treatment that will destroy microorganisms while maintaining the highest food quality possible
- Cost: completing a cost study
