Microwave - Microwave Ovens: The Facts

In today's society, microwave ovens have become ubiquitous. We have embraced this means of technology as a necessary part of our lives. How could we ever warm up that cup of coffee or soup if we did not have a microwave?

The microwave oven has been with us for a long time, too. When the microwave oven first was introduced many people thought that all this radiation going around penetrating food to cook it was somewhat frightening and that eating it just had to be unhealthy somehow. How could a mother heat up her infant's formula with the contamination of the microwaves? The horror!

Today most people own microwaves and many cannot imagine their lives without one. As time passed though, people came around and recognized the innovative microwave oven as a welcome addition to the home. Being able to heat up those holiday left-overs in nothing short of a jiffy was simply an incredible time-saver.

Here are some of the lesser-known facts about microwaves:

* In a microwave oven, food may be heated for so short a time that it is cooked unevenly, since heat requires time to diffuse through food, and microwaves only penetrate to a limited depth. Microwave ovens are frequently used for reheating previously cooked food, and bacterial contamination may not be killed if the safe temperature is not reached, resulting in food borne illness.

* A second problem is due to food composition and geometry, and must be addressed by the cook, who should arrange the food so that it absorbs energy evenly, and periodically test and shield any parts of the food that overheat. In some materials with low thermal conductivity, where dielectric constantly increases with temperature, microwave heating can cause localized thermal runaway. Uneven heating in frozen foods is an example. Ice absorbs the microwave much slower than liquid water. Defrost in the microwave to bring your food to the same temperature. The cooking will be a much better even temperature.

Some dangers:

* Liquids, when hated in a microwave oven in a container with a smooth surface, can superheat; that is, reach temperatures that are a few degrees in temperature above their normal boiling point, without actually boiling. The boiling process can start explosively when the liquid is disturbed, such as when the operator removes the container from the oven and a steam burn is the result. A common myth is that only distilled water will do this; this is not true.

* Putting anything metal in the microwave is still dangerous for it will conduct the radiation from the metal. Some cases have been documented where Chinese food warmed in the oven with its metal handle have caused microwave fires.

* Homemade microwave popcorn bags have been sealed using a metal staple, which is then heated and sets fire to the bag. This type of accident can pose a dangerous situation because of the extremely flammable mixture of popcorn and oil in the bag.

* Metal wire-containing twist ties are notorious for microwave sparking. Thus, it is a good practice to remove any metal-containing objects from a microwave oven.

How about Radiation?

* In the United States of America Microwave ovens produced after 1971 must meet the Food and Drug Administration safety requirements for radiation leakage; less that 5 mW/cm2 at 5 cm from the surface of the oven. This is far below the exposure level that is currently considered to be harmful to human health.

* The radiation produced by a microwave oven is non-ionizing. As such, it does not have the cancer risks associated with ionizing radiation such as X-rays, ultraviolet light, and nuclear radioactive decay. Any cancer risk from microwave oven would necessarily occur by an unknown mechanism.

Following the instructions supplied by the manufacturer is the safest way to determine if your microwave is safe. Whether there will be a long term effect or not is hard to measure until the test of time. The information supplied at this time is that it is relatively safe if it is used correctly.

So the bottom line is that there is a slightly different skill to using a microwave oven instead of a conventional oven, and there are some fire-hazards to consider -- but we're all smart enough not to put a box of tissues in a conventional oven, we just need to get used to thinking of metal as a fire hazard in a microwave.

And the radiation thing is totally busted. Microwave radiation causes liquid water to heat up and not much else. Being inside a microwave that was cooking would be a bad thing, but the same could be said for a conventional oven. From the outside, they're equally safe.