Microwave, plastics a bad combination

A lot of people microwave leftovers in plastic margarine tubs, plastic wrap or plastic bags. But are these safe practices?

Here's what experts with the USDA's Meat and Poultry Hotline and one manufacturer of plastic storage wrap have to say about these and other questions:

Q: Is it safe to microwave-heat foods in margarine tubs or cottage cheese containers?

No. Cold-food storage containers are intended for those uses only. They have not been tested or approved for any other use, including cooking. Do not use margarine tubs, whipped topping or cottage cheese containers for heating food. They are not heat stable and chemicals from the plastic could migrate into the food during heating.

Q: What about using plastic wrap in the microwave oven?

The major concern over the use of plastic wrap during food preparation is the potential harmful effects of migration of certain chemicals, called "plasticizers," from the film to the food during cooking.

Avoid direct contact of the food with plastic wrap when reheating in the microwave. Manufacturer S.C. Johnson & Son recommends clearing an inch of space between the food and the wrap before microwaving, and folding back the corner of the wrap to allow steam to escape. They do not recommend using the wrap for poaching or steaming foods.

Also, remove store wrap before microwave defrosting. Foam trays and plastic wraps are not heat stable at high temperatures. Melting or warping from hot food could leach chemicals into the food.

Q: Are there cautions for microwaving foods in plastic storage bags?

Food should not be microwaved in thin plastic storage bags. Plasticizers may have been added to the plastic material. Glass and glass ceramic cookware are safe for use in the microwave. Oven cooking bags, wax paper, parchment paper and white microwave paper towels would be safe to use if labeled for microwave use.

Q: Is it safe to use paper grocery bags for cooking or baking?

No. Grocery bags are not intended or formulated for cooking foods. Components such as metal fragments, glue and chemicals may be present at higher-than-acceptable limits and can migrate into the food. And these bags may not be sanitary, either.

Q: What about the safety of storing food in plastic grocery or trash bags?

Again, the USDA's answer is no. These are not made from food- grade plastic, and chemicals from them may leach into the food.

For additional information on the safety of food packaging materials, call the manufacturer or the USDA Meat and Poultry Hotline at (800) 535-4555 , or contact the CSU Extension Office at 636-8930.

- Ryan is a consumer and family-education agent for Colorado State University Cooperative Extension. Contact the Springs extension office: 636-8920

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