WSU Thurston County

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Lacey WA  98503

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Thurston County Extension

Food Safety: Cooking Equipment

The Olympian, December 16, 1998

Microwave cooking has been around for a long time. The speed of cooking many foods in a microwave oven is still a major advantage when compared to oven or stove top cooking. There are, however, some traits unique to microwave cooking that affect how evenly and safely food is cooked.

QUESTION: How do microwave ovens work?

ANSWER: Microwaves work by converting electrical energy to microwave radiation in a special vacuum tube in the oven. Microwave energy may also be called electromagnetic energy. Other forms of electromagnetic energy include heat, light, and radio waves. The microwaves are reflected within the cooking unit and are absorbed by the food.

Almost all food contains some amount of water. If you remember some of your basic high school chemistry, you’ll recall that water molecules and the bonds between the oxygen and hydrogen are rather unique. When the reflected microwaves hit the water molecules, they cause the bonds between the hydrogen and water to vibrate very rapidly. This energy is converted to heat in the food.

QUESTION: We frequently use the microwave to defrost food. Should we remove the store wrapping prior to defrosting?

ANSWER: Great question! Often, foam trays and plastic wraps are not heat stable at the high temperatures produced in a microwave. As the food defrosts and heats, melting or warping may occur and cause chemicals from the trays or wrapping to migrate into the food. This migration could be a health and safety hazard. Instead, place the food on a microwave safe plate or container that will collect any drippings. Check the labels on any container you use to make sure they are microwave safe.

QUESTION: How soon after defrosting meat or poultry in the microwave should we cook the food?

ANSWER: Cook the meat or poultry immediately after micro-thawing. Microwave units typically have cold spots because of the irregular way the microwaves enter the oven and are absorbed by the food. So some areas may begin to cook during the defrosting time. If you hold partially cooked food without fully cooking, you may have an opportunity for pathogenic bacteria to grow and multiply.

QUESTION: I defrosted a pot roast and forgot to take it out of the microwave. Can I go ahead and cook it?

ANSWER: Food should not be left out of refrigeration for more than two hours. Pot roasts are expensive, but if it’s been longer than two hours, you should throw the meat out. "When in Doubt, Throw It Out."

QUESTION: Our pottery dinnerware isn’t labeled for use in the microwave. Is there any way we can tell if it’s safe to use for re-heating food?

ANSWER: According to the Food Safety and Inspection Service of the USDA, there is an easy test you can perform at home. Place the empty dinnerware in the microwave alongside one cup of water in a glass measuring cup. Microwave on high for 1 minute.

If the dish remains cool, it’s safe to use. If the dish gets warm or hot to the touch, don’t use it in the microwave.

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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