Freezers And Food Safety

- Freezing foods to 0°F inactivates any microbes--bacteria, yeasts and molds--present in food. Once thawed, however, these microbes can again become active, multiplying under the right conditions to levels that can lead to food-borne illness. Since they will grow at about the same rate as microorganisms on fresh food, you must handle thawed items as you would any perishable food.

- Trichina and other parasites can be destroyed by sub-zero freezing temperatures. But it is not recommended to rely on home freezing to destroy trichina. However, thorough cooking will destroy all parasites.

- Enzymes present in animals, vegetables, and fruit promote chemical reactions such as ripening.

Ultimately, enzyme activity can lead to the deterioration of food quality. Enzyme activity does not harm frozen meats or fish and is neutralized by the acids in frozen fruits. But most vegetables that freeze well are low-acid and require a brief, partial cooking  (blanching) to prevent deterioration.

Source(s):

USDA Fact Sheets "Safe Food Handling"