Course:FNH200/Lessons/Lesson 07/Page 07.4

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7.4 Summary of Lesson 7

  • Low temperature processing and its packaging materials are designed to extend the food's shelf life by slowing down microbial growth and chemical/enzymatic reactions.
  • Microbial growth and chemical/enzymatic reactions will resume once the food is thawed or exposed to "warmer" temperatures.
  • Refrigeration (cool storage) refers to temperatures between -2°C to16°C . In particular at 4°C. This provides only a short term shelf-life extension in food as psychrotrophic organisms can still grow.
  • During refrigeration, the temperature, humidity and gas atmosphere composition must be monitored in order to prevent undesirable changes in the food.
  • Modified atmosphere packaging (MAP) is commonly used with some refrigerated products to enhance the shelf life of the product.
  • Below -9.5°C, there is no significant growth of spoilage or pathogenic organisms
  • Freezing refers to temperatures below the freezing point of water. In the food industry, a minimum of -18°C is required. Food is preserved by the use of lower temperatures and lower water activity.
  • During freezing, several factors (e.g. freezing rate, final storage temperature, etc) must be controlled in order to prevent undesirable changes (oxidation reactions, freezer burn, ice crystal damage, etc)
  • Packaging materials should assist in preventing these undesirable changes.

Supplemental Videos:

  1. Individually Quick Freeze (IQF) of sardines
  2. How to Make Frozen Treats


Potter, N. N. and J.H. Hotchkiss. 1998. Cold Preservation and Processing. Chapter 9 in Food Science, 5th ed. Chapman and Hall, New York, NY.


FNH 200 Course content on this wiki page and associated lesson pages was originally authored by Drs. Brent Skura, Andrea Liceaga, and Eunice Li-Chan. Ongoing edits and updates are contributed by past and current instructors including Drs. Andrea Liceaga, Azita Madadi-Noei, Nooshin Alizadeh-Pasdar, and Judy Chan.

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1. Syneresis leads to the following change(s) in refrigerated foods:

Staling of bread
Loss of crispness and flavour in fruits and vegetable
Colour change in fresh meat
Loss of nutrients
Drip loss in fish

2. Which package material below is NOT suitable for frozen products?

Foil film
Glass bottle
Plastic film
Tetra pak

3. A slush freezer is an example of

Air Freezing
Indirect Contact Freezing
Immersion Freezing
Cryogenic Freezing

4. Psychrotrophic organisms can grow while food is stored in the refrigerator.


5. Under freezing conditions, chemical reactions can still occur.