The U.S. Department of Agriculture estimates that 90 percent of U.S. homes have at least one microwave oven. These appliances play an important role in helping us prepare meals in today’s busy lifestyles. But because microwaves can cook unevenly and leave cold spots where bacteria can survive, follow these special rules for cooking or reheating foods.

Know the Wattage of Your Microwave

If your microwave’s wattage is lower than the wattage mentioned in the cooking instructions on the food package, it will take longer than the instructions say to cook the food to a safe internal temperature. The higher the wattage of a microwave oven, the faster it will cook food. If you don’t know the wattage of your microwave oven, see if it’s stated on the inside of the oven’s door, on the serial number plate on the back of the oven, or in the owner’s manual.

Microwave-Ready Foods

Don’t take shortcuts when cooking microwave-ready foods. Always follow package instructions closely. Many microwave foods need to “stand” for a few minutes after the microwave has turned off. Stand times are not optional, but an essential part of the cooking process during which the temperature of the food continues to rise.

Microwave Defrosting

Microwave ovens can be used to help defrost many types of frozen foods. However, only use them to defrost meat, poultry or fish if you plan to continue cooking the food immediately after thawing.

Most frozen foods need to be removed from their original packaging before defrosting. Use the defrost setting on your microwave or set the unit at 30 percent power. When defrosting in a microwave, rotate and turn the food frequently, and break apart larger food items where possible. When thawing ground meat, scrape and remove thawed portions as they soften.

Reheating Foods

Microwave ovens are great for warming leftovers. Be sure to rotate and stir the food frequently to eliminate cold spots and reheat all leftovers to at least 165º F.

Use a Food Thermometer

Because microwave output varies, cooking time can differ from one unit to the next. Use a food thermometer and test foods in multiple spots to make sure they have reached a safe internal temperature. Digital thermometers are best to use because they are accurate and respond quickly to temperature changes. Always observe any stand times specified in the cooking instructions. Stand time is the time after the food is removed from the heat source, but the food continues to cook.

General Microwave Oven Cooking

Some additional tips to keep in mind when using a microwave oven for any type of cooking:

  • Arrange foods as evenly as possible in a covered dish. Add a small amount of water to the dish if needed, as moisture helps in the microwave cooking process.
  • Stir or rotate food throughout the microwave cooking process to eliminate cold spots and to promote more even cooking.
  • Cook large cuts of meat on medium power (50 percent), which helps allow the heat to reach the center without overcooking outer surfaces.
  • Don’t confuse microwave and conventional ovens. If the package says to cook the food in a conventional oven, don't try the microwave instead. 
  • Use cookware that is specially manufactured for use in the microwave. Plastic storage containers like margarine tubs, take-out containers and other one-time use containers are usually not microwave safe and may warp or melt.

Microwave cooking has a firmly established place in most homes. Just remember that even with these time-saving appliances, you must still follow proper food handling procedures to keep food safe.