Food stored constantly at 0 degree F will always be safe. Only the quality suffers with lengthy freezer storage.
Freezing keeps food safe by slowing the movement of molecules, causing microbes to enter a dormant stage. Freezing preserves food for extended periods because it prevents the growth of microorganisms that cause both food spoilage and food borne illness.
Freezing to zero degrees Fahrenheit 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 then grow at about the same rate as microorganisms on fresh food, you must handle thawed items as you would any perishable. Thorough cooking will destroy bacteria.
Trichina and other parasites can be destroyed by sub-zero freezing temperatures. However, very strict government-supervised conditions must be met.
It is not recommended to rely on home freezing to destroy trichina. Thorough cooking will destroy all parasites.
Freshness and quality at the time of freezing affect the condition of frozen foods. If frozen at peak quality, foods emerge tasting better than foods frozen near the end of their useful life.
So freeze items you won’t use quickly sooner rather than later. Store all foods at 0 degree F or lower to retain vitamin content, color, flavor and texture. The freezing process itself does not destroy nutrients. In meat and poultry products, there is little change in nutrient value during freezer storage.
Enzyme activity can lead to the deterioration of foods quality. Enzymes present in animals, vegetables and fruit promote chemical reactions, such as ripening.
Freezing only slows the enzyme activity that takes place in foods. It does not halt these reactions which continue after harvesting. 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 to prevent deterioration. This is called “blanching.” For successful freezing, blanch or partially cook vegetables in boiling water or in a microwave oven.
Then rapidly chill the vegetables prior to freezing and storage. Consult a cookbook for timing.
Proper packaging helps maintain quality and prevent “freezer burn.” It is safe to freeze meat or poultry directly in its supermarket wrapping but this type of wrap is permeable to air.
Unless you will be using the food in a month or two, over-wrap these packages as you would any food for long-term storage using airtight heavy-duty foil, plastic wrap or freezer paper, or place the package inside a plastic bag. Use these materials or airtight freezer containers to repackage family packs into smaller amounts or freeze foods from opened packages.
It is not necessary to rinse meat and poultry before freezing. Freeze unopened vacuum packages as is.
If you notice that a package has accidentally torn or has opened while food is in the freezer, it is still safe to use; merely over-wrap or re-wrap it.
Freezer burn does not make food unsafe, merely dry in spots. It appears as grayish-brown leathery spots and is caused by air reaching the surface of the food.
Cut freezer-burned portions away either before or after cooking the food. Heavily freezer-burned foods may have to be discarded for quality reasons.
Color changes can occur in frozen foods. The bright red color of meat as purchased usually turns dark or pale brown depending on its variety.
This may be due to lack of oxygen, freezer burn or abnormally long storage. Freezing doesn’t usually cause color changes in poultry.
However, the bones and the meat near them can become dark. Bone darkening results when pigment seeps through the porous bones of young poultry into the surrounding tissues when the poultry meat is frozen and thawed.
The dulling of color in frozen vegetables and cooked foods is usually the result of excessive drying due to improper packaging or over-lengthy storage.
Freeze food as fast as possible to maintain its quality. Rapid freezing prevents undesirable large ice crystals from forming throughout the product because the molecules don’t have time to take their positions in the characteristic six-sided snowflake.
Slow freezing creates large, disruptive ice crystals. During thawing, they damage the cells and dissolve emulsions. This causes meat to “drip”–lose juiciness. Emulsions such as mayonnaise or cream will separate and appear curdled.