The Truth About Microwave Cooking Safety

February 3, 2009

Many people assume that cooking foods in a microwave is essentially no different than cooking in an oven – just quicker. Although microwave cooking can indeed be done safely, you should not ignore some simple rules for increased assurance.

First, understand that even though microwave cooking is referred to as “nuking,” there is no radioactive danger to food cooked this way. Microwave ovens work by bouncing microwaves inside the oven. The energy in these microwaves is similar to the heat energy in a conventional oven (which also consists of waves, just of a slightly different frequency). X-rays and nuclear radiation are at the other end of the energy spectrum and contain energies a million times more powerful.

The main danger posed by microwaves is an inattention to the danger of bacterial contamination. Foods cooked in a conventional oven must also address this issue, but microwave ovens pose their own special problems.

According to recent USDA studies, almost all poultry products contain some amount of salmonella contamination. About 25% to 45% of ground chicken samples tested, for example, contain bacterial contamination. Ground turkey averages about 20% to 25% contamination, while chicken broilers average about 10% to 12%. So you should assume that any poultry products you are cooking start off with some salmonella contamination. Egg products contain their own contamination issues as well.

That’s why you should be concerned about “cold spots” that usually occur in microwaved foods. Microwaves do not spread as evenly in the oven as heat waves, and some food ingredients (specifically water, fat and sugars) tend to attract more wave energy and thus cook faster. Other parts of the food cook more slowly, leaving uneven temperatures. Since heat is what kills any bacterial contamination, you must be sure to encourage even heating.

This is the reason for rotating foods, stirring foods halfway through cooking, checking meat temperatures with thermometers, and letting food “rest” after the cooking cycle is over. Even after the oven is off, some parts of the food (again, water, fats and sugar) will continue to vibrate from the energy they absorbed and help further cooking.

Also, microwave energy does not “cook from the inside,” as is sometimes heard. Microwaves actually penetrate from the outside and only travel about 1 to 1.5 inches into thick cuts of meat. Any further cooking of the inside is done through heat conduction from the outer layers (just like a regular oven), so thermometers should be used to make sure that the inside of meat products have heated to recommended temperatures.

Another problem with microwave cooking relates to layers of moisture on the outside of the product (e.g., a layer of ice crystals). The microwave energy will be spent evaporating this moisture, while still heating the layers below this surface, leaving the surface layer actually cooler than the inside. You should thus not only check the inside temperature, but make sure the outer skin has heated thoroughly.

Some people believe that microwaving in plastic containers carries a danger of adding carcinogens to your food. Not really. Most hard plastic containers are safe to use. Cold storage plastics, such as margarine tubs, take-out containers and other such one use containers should not be used, however, because they can warp and melt from the heat and add chemicals to your food. Plastic wrap over food is safe, as long as the wrap does not touch the food itself.

All in all, microwave cooking is convenient and can also be safe if you carefully monitor temperatures. Of course, if you want to cook that 2 inch thick t-bone with a crusty outside and pink interior, you’d best stick to regular ovens or grills.