We do this without thinking about it. Pop something in the microwave and heat it up, lickety-split. But what’s going on in there? Where does the heat come from? If you use a plastic container, do harmful particles spread into your food?
How it works
A microwave is a radio wave. The radio frequency that most microwaves use has very unique properties. At about 2.5 gigahertz, radio waves are absorbed by water, fats and sugars, but are not absorbed by glass, ceramics or most plastics substances.
As the water, fat and sugar molecules absorb the microwaves, atomic motion, or heat is created. Essentially, the molecules within the food vibrate, heat up and cook. The container itself is not warmed, but heat can transfer from the cooking food to the container.
Is plastic safe in the microwave?
It depends on who you ask.
Plastic manufacturers say that if the container is marked “microwave safe” that means it has been tested by the FDA at various temperatures and cooking times and found to withstand the heat properly. However, the FDA only tests containers that are to be labeled “microwave safe.” Many plastic containers, such as those used for takeout food, margarine tubs or other storage units, are not designed to withstand the high heat of the cooked food and may leak chemicals.
Plasticizers, substances used to make plastic containers, may leach into food. A chemical called diethylhexyl adipate is particularly prone to leak into fatty foods such as cheese or meat during the cooking process.
A study conducted by the Milwaukee Journal Sentinel led to the conclusion that it’s simply not a good idea to let plastic touch your food in the microwave.
The newspaper tested several plastic containers that were indeed labeled as microwave safe. They found Bisphenol A (BPA) leaching from every container in the test. Even plastics generally considered as safer, those with recycling codes of 1, 2 and 5, were found to leak.
"There is no such thing as safe microwaveable plastic," said Frederick vom Saal, Ph.D. a University of Missouri professor who managed the study.
BPA is a chemical that disrupts the endocrine system and has been found to cause neurological and developmental damage in laboratory animals. BPA behaves like a hormone and mimics estrogen. Exposure can lead to genital defects, behavioral changes and abnormal development of mammary glands similar to those seen in women at high risk for breast cancer. Infants and children are most at risk for such complications.
As convenient as plastic storage containers are, the only sure way to avoid possible leaching of chemicals is not to use them when heating up food.
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