Why Do We Cover Food in the Microwave With Plastic?

Microwave oven

When cooking food in the microwave, you can cover the dish with a microwave-safe plastic lid or with plastic wrap. Reusable lids are preferable from an environmental point of view.

Spatter

Plastic placed over food in the microwave helps prevent spatter. Anyone who has ever warmed up baked beans, for example, will notice that a lack of a cover results in explosive mess.

Cooking

Putting plastic over food in the microwave helps the food cook evenly and helps the food maintain its natural moisture. The steam generated also helps kill bacteria.

Metal

CD "cooked in a microwave oven

Metal placed over food in the microwave causes the microwave to malfunction. High-frequency microwaves are contained by the oven itself. Metal turns some of the microwave energy into electricity, causing sparks that will ultimately damage the oven.

Microwave-safe

According to Harvard University, while it is technically possible to be harmed by eating food microwaved in and under plastic, so long as you use products labeled microwave-safe you will not be harmed.

Warning

It is a good idea to put a vent in any plastic wrap placed over the food. Otherwise, take extreme care when lifting wrap or other plastic covers from the food, as the hot steam can quickly scald you.

References

• ChemistryQuestion.com: Microwaves and Metal
• Harvard University: Safety of Plastics in Microwaves
• Department of Agriculture: Cooking With Microwaves

Resources

• Plasticsinfo.org: Plastics and Microwaves