Health Library

Safe Microwave Cooking

PD V20 FD001677 Microwave ovens do not cook food like other appliances. In a regular oven, hot air makes both the food and its container hot, while in a microwave, the air is cool. The microwave oven emits microwaves which cause food molecules to vibrate. The resulting friction causes heat. This heat can get hot enough to kill the bacteria in foods. However, there are a few limitations.

These microwaves heat the molecules on the outside of the food. This can, in turn, heat further inside the food, but usually there are cold spots. These cold spots are uncooked or unheated food where bacteria can survive. But, there are some things you can do to prepare food safely and deliciously in a microwave.

Important Things to Do When Cooking in a Microwave

  • Arrange the food.
    • Cut the food into pieces that are the same size, if possible. Cutting will give the food more edges and edges get more exposure to microwaves.
    • Since outer areas receive more heat than the center, arrange thicker pieces on the outside of the dish.
  • Cover the food.
    • Cover the dish with a lid, paper towel, or plastic wrap. Do not let the plastic wrap touch the food; see below. This will trap steam. This moist heat will destroy bacteria and help even the temperature throughout the food.
  • Rotate the food.
    • Some microwaves have a rotating dish in the center. If yours does not, stop the microwave half way through the cooking time to rotate the dish.
  • Stir the food.
    • Stopping the cooking half way through the cooking time to stir the food is the best way to ensure elimination of cold spots and bacteria.
  • Let it sit.
    • Food continues to cook after the microwave turns off. This is due to the vibration of the outer food cells penetrating the heat to the inner cells. This is important for the thorough heating and killing of bacteria.

These guidelines are important whether you are cooking raw food or reheating a meal.

Food Safety Temperatures

It is important to become familiar with your microwave. Different ovens will take longer to cook the same food. All foods should be cooked right away after defrosting. Never partially cook food and store it for later use.

  • Large cuts of meat should be cut smaller. If that is not possible, then meats should be cooked on 50% power (medium) to allow the heat to reach the center without overcooking the outer areas.
  • Use a food thermometer to verify that the food has reached a temperature where the bacteria have been destroyed. Safe cooking temperatures:
    • Red meat: 160˚F (71°C)
    • Poultry: 165˚F (74°C)
    • Pork: 160˚F (71°C)
    • Leftovers: 165˚F (74°C)
  • Cooking a stuffed poultry in a microwave is not recommended.

Be especially careful when heating baby formula in a microwave, as it may result in a scald to the baby's mouth or throat. Even though a bottle might not feel warm to the touch after it has been microwaved briefly, there may be hot spots within the formula.

Containers and Wraps

It is important to cook food in a container that will not melt. If the container melts, harmful chemicals can leak into the food.

Use cookware made of:

  • Glass
  • Ceramic
  • Other containers labeled specifically for microwave use

Never use:

  • Aluminum foil
  • Plates made of Styrofoam or plastic plates that do not say they are microwave safe
  • Storage containers such as margarine tubs and take-out containers with metal handles

Plastic wraps are commonly used to cover food while cooking in a microwave. Some wraps have chemicals that would be harmful if they leaked into the food. Precautions should be taken to make sure that the plastic wrap does not touch the food at all. Never reuse plastic wrap. Alternatively, a paper towel or a lid for a microwave-safe container might be the safest way to go.

Microwave Oven and Nutrition

Microwaves themselves do not destroy nutrients. However, heat can cause the nutrient level in foods to be reduced. Water can dissolve and wash away some vitamins. This is true of any type of cooking. There has been some speculation that microwaved food can be harmful to people. There is no credible experimental evidence to back up that statement.

Resources

Academy of Nutrition and Dietetics
http://www.eatright.org

United States Department of Agriculture
Food Safety and Inspection Servicehttp://www.fsis.usda.gov

Canadian Resources

Canadian Partnership for Consumer Food Safety Education
http://www.canfightbac.org

Health Canada
http://www.hc-sc.gc.ca

References

Cooking meat safely. Clemson University Cooperative Extension Service website. Available at: http://www.clemson.edu/extension/hgic/food/food%5Fsafety/handling/hgic3580.html. Accessed April 10, 2013.

Cooking safely in the microwave oven. United States Department of Agriculture website. Available at: http://www.fsis.usda.gov/Fact%5FSheets/Cooking%5FSafely%5Fin%5Fthe%5FMicrowave/index.asp. Updated May 24, 2011. Accessed April 10, 2013.

Microwave cooking and nutrition. The Harvard Medical School Family Health Guide website. Available at: http://www.health.harvard.edu/fhg/updates/Microwave-cooking-and-nutrition.shtml. Updated June 2008. Accessed April 10, 2013.

Microwave ovens and food safety. Health Canada website. Available at: http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/prod/micro-f-a-eng.php. Published July 2005. Accessed April 10, 2013.

Microwave ovens and food safety. United States Department of Agriculture website. Available at: http://www.fsis.usda.gov/pdf/microwave%5Fovens%5Fand%5Ffood%5Fsafety.pdf. Updated October 2011. Accessed April 10, 2013.

Safely preparing and reheating foods in microwave ovens. Academy of Nutrition and Dietetics website. Available at: http://www.eatright.org/Media/content.aspx?id=6442459585&terms=plastic%20wraps. Accessed April 10, 2013.

United States Department of Agriculture and United States Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th Edition, Washington, DC: United States Government Printing Office, December 2010.