LSU AgCenter Nutritionist Explains Whats Safe For Microwaving

Elizabeth S. Reames  |  1/5/2005 3:03:36 AM

News You Can Use For January 2005

Consumers often ask about the safety of using plastic wrap or plastic containers in microwave ovens. According to LSU AgCenter nutritionist Dr. Beth Reames, only plastic containers or packaging labeled "microwave safe" should be used in microwave ovens.

Reames adds that if plastic wrap is used when microwaving, it should not be allowed to come into direct contact with food.

The Food and Drug Administration carefully reviews the substances used to make plastics designed for food use. These include microwave-safe plastic coverings that keep food from splattering and microwave-safe containers that hold frozen dinners.

The concerns expressed about the safety of using plastic wraps in the microwave have involved two compounds: dioxins and DEHA.

Dioxins and dioxin-related compounds are pollutants that may produce health hazards ranging from birth defects to cancer. Reames explains that dioxins may be a by-product of some industrial processes that use chlorine and incineration of chlorinated plastics such as polyvinyl chloride. PVC is a component of some plastic wraps and food packaging. One major manufacturer, Saran Wrap, has reformulated its product so that it no longer contains PVC or any other chlorinated substance.

There is no research demonstrating that dioxins are produced when the same plastics are heated in a microwave oven. Ed Machuga, consumer safety officer with the U.S. Food and Drug Administration, wrote, "We have no evidence that plastic containers can produce dioxins when heated in microwave ovens. In fact, most, if not all, plastic containers would not even have the correct chemical composition to theoretically form dioxins."

DEHA is a softening compound added to some plastic containers and wraps to make them more pliable. Studies have shown that DEHA, if present, can migrate to food from plastic containers and plastic film at high temperatures. However, plastic materials used in microwaveable and dual-ovenable food containers such as those used to hold TV dinners must undergo approval by FDA before they can be marketed for their intended use. As part of this approval process, manufacturers must provide data showing that dietary exposure to these low molecular weight migrants do not pose a safety problem.

The U.S. Environmental Protection Agency removed DEHA from its list of toxic chemicals in the late 1990s after extensive research, and the scientific consensus is that it is not toxic to humans in the minute amounts resulting from migration from plastics into foods.

To minimize the amount of these chemicals migrating from plastic films to fatty foods, FDA recommends that, if these films are used to cover food being heated in a microwave oven, the consumer should try not to let the film touch the actual surface of the food.

In addition, consumers should only use food-approved, microwave-safe plastic containers and film wraps for microwave heating.

"Consumers should be sure to use any plastics for their intended purpose and in accordance with directions," Reames says, adding, "If there are no instructions for microwave use, use a different plate or container that you know is microwave-safe. Such containers are made to withstand high temperatures."

USDA's Food Safety and Inspection Service on cooking foods safely in microwaves gives the following advice about containers and wraps:

• Use only cookware that is specially manufactured for use in the microwave oven. Glass, ceramic containers and all plastics should be labeled for microwave oven use.

• Don’t use margarine tubs, take-out containers, whipped topping bowls and other one-time use containers in microwave ovens. These containers can warp or melt, possibly causing harmful chemicals to migrate into the food.

• Use safe items like plastic wraps, wax paper, cooking bags, parchment paper and white microwave-safe paper towels. Do not, however, let plastic wrap touch foods during microwaving.

• Never use thin plastic storage bags, brown paper or plastic grocery bags, newspapers or aluminum foil in the microwave oven.

In addition, the American Plastics Council recommends that carryout containers from restaurants should not be used in the microwave. These containers may melt or warp, which can increase the likelihood of spills and burns.

Also, discard containers that hold prepared microwavable meals after you use them because they are meant for one-time use.

Reames advises placing microwave-safe plastic wrap loosely over food so that steam can escape, and don’t let it directly touch your food. Some plastic wraps have labels indicating that there should be a 1-inch or more space between the plastic and the food during microwave heating.

Covering food helps protect against contamination, keeps moisture in and allows food to cook evenly.

For information on related nutrition, family and consumer topics, visit the FCS Web site at
Extension/Departments/fcs/.  For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.


On the Internet: LSU AgCenter:
Source: Beth Reames (225) 578-3929, or

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