Why do we emphasize storing frozen foods at 0 degrees F? Even though other freezer temperatures can stop the growth of microorganisms, quality will continue to be lost even at these cold temperatures. The recommended shelf life listings we have for frozen foods are based on a storage temperature of 0 degrees F. and expected retention of good quality. Warmer temperatures, even though the food may still be frozen, will result in shorter retention times for quality.
Even though blanching for specific time at a given temperature is recommended to inactivate enzymes, oxygen around the food as well as the dryness of the air in a freezer will cause other quality losses. And foods that are not blanched, or are inadequately blanched, will have active enzymes. Enzymatic and oxidative changes in stored food will occur more slowly at freezer temperatures than higher ones, but they still will proceed. One chemical reaction that will proceed, even though slowly, in the freezer is oxidative rancidity of fats (including those contained within meats, poultry, etc.).
Another way to protect quality of frozen foods is to achieve a fast rate of freezing. The faster that the water in foods gets frozen, the more protective for quality. Fast freezing promotes the formation of smaller ice crystals than slow rates of freezing. The smaller the ice crystals, the less damage done to cell walls and the texture of foods.
Fast freezing can be promoted by making sure hot or warm foods are completely cooled before putting them into the freezer, using small package size, and then spreading your packages out within the freezer until the food is frozen. The packages can then be stacked or arranged together if you wish, but while they still becoming frozen, make sure the cold air can surround all sides of the package. It is a good organizational plan to package your foods into suitable serving sizes anyway, but a good rule of thumb to promote fast freezing is to keep each package size fairly small. If you know you will be placing a large quantity of foods into the freezer at once, consider setting the temperature control of your freezer to -10 degrees F. or lower about 24 hours in advance. Usually about 2 to 3 pounds of food per cubic foot of storage space can freeze within 24 hours.
Speaking of freezing foods that are first blanched or cooked, make sure they are completely cooled before even putting them into your freezer containers or bags, also. An important reason is to promote quick freezing once inside the freezer for food quality and energy efficiency; however, another reason is the size of those ice crystals again! Moisture that condenses on a lid or sides of a package from hot steam will lead to quality-damaging large ice crystals inside the package.
Freezing food is an excellent way to preserve the freshness in most foods, as well as the nutrients, colors and tastes. However, there are best practices to make sure these advantages are realized. For more readings on this topic:
Freezing Pointers: http://nchfp.uga.edu/how/freeze/pointers.html
General Shelf Life of Frozen Foods: http://nchfp.uga.edu/how/freeze/freezer_shelf_life.html
How to Freeze Specific Foods: http://nchfp.uga.edu/how/freeze.html