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Nusc 3233 Final Exam Questions And Accurate Answers
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Nusc 3233 Final Exam QuestionsAnd Accurate Answers
Methods of Food Preservation: Why - Answer Safety
Retard growth of microorganisms
Kill bacteria, yeast and mold
Unsafe foods
Gastrointestinal upset - death
Quality is secondary to safety
Pennsylvania Hepatitis cases excess 500 - Answer Green onion
Salmonella poona in 2015 - Answer Cucumbers
Case Count: 732
States: 35
Deaths: 4
Hospitalizations: 150
Recall: Yes
Listeriosis, 2015 - Answer Soft cheese
Case Count: 24
States: 9
Deaths: 1
Hospitalizations: 22
Recall: Yes
Methods of Preservation what it does - Answer 1. Freezing- Kills some microorganisms
and slows growth of others.
2. Canning- Kills all microorganisms
3. Pasteurization- Kills harmful microorganisms, does not permit long storage time
,**At moisture below 13%, food can be stored in shelf for long periods of time**
4.Drying:
Dehydrates microorganisms
5. Irradiation
Used to limited extent. Likely to increase in the future
6. Salting
Sometimes used to preserve fish and meat
7. Sugar and Pickling
Provide hostile environment for microorganisms
Freezing - Answer Popular method
Relative convenience
Good storage from 6 to 12 months
Quality of food may deteriorate over time
Does not compromise safety
Deterioration depends on product
Strawberries versus bread
Supercooling - Answer Reduction of the temperature of water below freezing until
crystallization begins
Temperature then rises to 0 °C due to latent heat of crystallization
Latent Heat of Crystallization - Answer Heat released during transition from the liquid
state (higher energy) to the frozen stage (lower energy)
Methods of Freezing - Answer Timing is everything:
Sharp Freezing (slow)
Still air ( T -23 to -30°C)
Blast Freezing (fast)
Air blast freezers (-30 to - 45°C)
Indirect-contact freezing (fast)
Placing packages of food in contact with cold shelves or passing liquids through a
,chilled tube
Cryogenic liquids (fast)
Substances that are liquids at extremely cold temperatures
Foods that can be frozen - Answer 1. Perishable raw foods
meats, poultry, fruits and vegetables
2. Perishable heated or cooked foods
Blanched vegetables, T.V dinners, baked items
3. Semi-perishable foods
bread, dough products, cheese, butter
4. Non-perishable foods
Nuts
Fruits and Vegetables - Answer Washed before freezing
Vegetables are blanched
Grape juice pasteurized
Complications with processing equipment
Meats and Poultry - Answer No treatment before packaging
Changes in color and flavor
Unsaturated fat promotes rancidity
Drip loss = losses in volume and juiciness.
Rapid freezing
Avoid formation of large crystals
Perishable heated foods - Answer -Baked products
-Salad dressings or emulsions break when frozen
Use of safflower oil (crystallizes at -7°C)
-Meringues
Considerable loss of quality during frozen storage
-Starched-thickened mixtures curdle
, Tendency of starch to retrograde
Amylopectin versus Amylose in starch
Canning - Answer Preservation of Food by heat
Careful control of time and temperature
Can be stored for 2 years
Commercially sterile - Answer Food that has been heat processed enough to kill all
pathogenic microorganisms and spores
Logarithmic order of Death - Answer -Percentage of bacteria and bacterial spores killed
per minute at constant temperature
-A deficiency in one minute of heating can make critical difference in the number of
pathogens
Thermal Death Time Curve - Answer -The higher the temperature the quicker the
microorganisms die.
-Defined as: Comparison of the rate of death of pathogenic microorganisms over a
range of processing temperatures.
-By processing under pressure, the time is reasonable
Microorganisms versus spores : Clostridium Botulinum - Answer -Spore forming,
anaerobic microorganisms that need to be destroyed during the thermal processing.
-Spores are much more resistant to everything including thermal processing.
Canning convection/conduction - Answer -Liquid foods are heated by Convection
-Solid foods are heated by Conduction
-Cold -Point: Coldest area of food in a can being heat-processed
Convection - Answer Heating by convection is influenced by the shape and composition
of food.
Options for Canners - Answer -Still Retorts
-Agitated Retorts
-Pressure canner
-Containers- Cans, retort Pouches
ex. horizontal retort, vertical retort
Canning at Home - Answer Use Pressure Canner
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