WSU Thurston County

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Lacey WA  98503

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Thurston County Extension

Food Safety: Food Preserving

The Olympian, November 11, 1998

Frozen foods add variety to our diets throughout the year as well as give you a head start in planning family meals. Freezing is also a great way to make use of leftovers. Here are some answers to the most frequently asked questions about freezing and the quality of frozen foods.

QUESTION: What is freezer burn?

ANSWER: If a food is improperly wrapped or frozen, it can develop freezer burn. Basically, the exposed surface of the food loses moisture and dries leaving white or gray spots on the product. The loss of moisture affects texture, color, and flavor of the product. You can avoid freezer burn by removing as much air as possible from the package and sealing the package airtight. It doesn’t affect safety of the food.

QUESTION: Does freezing kill bacteria?

ANSWER: Freezing does not kill all the microorganisms in food. At temperatures of 0ºF or less, their growth and multiplication is limited. Remember that when the food is thawed, bacteria can begin to grow again at temperatures above 40ºF.

QUESTION: If the power goes off, how long will the food in my freezer stay frozen?

ANSWER: If your freezer is located in a cool place, is full, well insulated, and remains unopened, food can remain frozen for several days. A half filled freezer, however will only keep food frozen for about 24 hours.

QUESTION: What’s the best temperature setting for my freezer?

ANSWER: The optimum temperature of your freezer is 0ºF or less. Chest and upright freezers can be set to maintain this temperature setting. If you’re using a refrigerator-freezer combination, it may not be possible to have such low temperatures. The only way to be sure is to use a freezer/refrigerator thermometer that registers temperatures from minus 20ºF to 80ºF. Place the thermometer near the top and front of the freezer and leave it there for at least six hours without opening the door before checking the temperature. Checking and maintaining a temperature of 0ºF or less keeps products in your freezer high quality.

QUESTION: I bought chocolate in bulk and tried to freeze it. The surface has developed a white discoloration. Is it safe to eat?

ANSWER: This discoloration is called "bloom". It can be caused by two circumstances. If the chocolate was stored too long at room temperature or exposed to high temperatures, the cocoa fat could have migrated to the surface of the chocolate. Generally when bloom occurs in refrigerated or frozen chocolate, the product has been loosely wrapped during storage. During storage, water sometimes condenses on the surface. The moisture draws sugar in the chocolate to the surface causing bloom. "Bloom" may look unappetizing, but it’s safe to eat the chocolate.

QUESTION: Can I use bread wrappers for freezing food?

ANSWER: No. It’s best to use polyethylene (plastic) bags that are designed for freezer use. Bread wrappers are not sufficiently moisture-vapor resistant for freezer use. Check the label on storage bags to determine if they are appropriate for freezing.

B. Susie Craig

Area Faculty

WSU Cooperative Extension Thurston County

WSU Extension programs and employment are available to all without discrimination.  Evidence of noncompliance may be reported through your local Extension Office.   Cooperating agencies: Washington State University, U.S. Department of Agriculture, and the county of Thurston.

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