March is National Frozen Food Month, a good time to discuss the commercial freezing of food and the safe handling of these foods.

According to the Library of Congress, Clarence Birdseye invented the quick-freezing method in 1924 and this method is still used today, albeit with improved technologies. Prior to the invention of this method, food would freeze at a slower rate, which would allow ice crystals to form inside the food. Upon defrosting, the ice crystals would melt, and the food would lose flavor and texture. The quick-freeze methods allow for foods to be frozen in minutes, thus allowing the food to retain its quality.

Commercially frozen foods are processed when the food is at peak quality, which means foods retain their nutritional value, freshness and flavor. This makes frozen fruit and vegetables a great alternative during the winter months when fresh varieties may be out of season or not readily available. Moreover, frozen foods are consistently priced year-round.

When purchasing frozen foods, transport the food as quickly as possible and place it in the freezer. It is best to bring ice packs and an insulated bag to help keep the food frozen while transporting. Food should not be left out for more than two hours, or one hour if the temperature is higher than 90 F.

Your freezer should be set to 0 F or colder to maintain the best quality of frozen food. Freezer thermometers can be purchased at your local home goods or big box store as an inexpensive and convenient way to ensure your freezer is operating properly.

Most refrigerator/freezer combinations have a frost-free freezer, which means that the freezer cycles as much as 32 F several times a day to keep frost from building up inside the unit. This cycling can affect the quality of food over time. If you are going to store frozen food for long periods, such as over several months, it may be best to invest in a deep-freeze style freezer, which will not undergo temperature cycling.

Check quality dates on frozen foods, and use the oldest food first. There are only three safe ways to thaw food: in the refrigerator, in cold water, or in the microwave. Never defrost food on the kitchen counter or outdoors.

Most commercially prepared foods have specific instructions for defrosting, cooking and using the food. These instructions have been placed on the food package by the processors to ensure that the food will ultimately be safe and to maintain quality. It is imperative to follow the instructions and never cook food in a manner not stated on package instructions.

Many are unaware frozen vegetables must usually be cooked before consumption to ensure safety and should not be added to other foods without cooking. When cooking frozen food, always verify that the food has reached the correct internal temperature as stated in the instructions.

Any cooked leftover food should be placed in the refrigerator or freezer within two hours after cooking. Leftovers stored in the refrigerator should be eaten within 3-4 days. Be sure to always heat leftovers to 165° degrees before consuming.

Dr. Stephanie Smith is an assistant professor and statewide consumer food specialist for Washington State University Extension. She can be reached at

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