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 mainly 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 resulting in 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. This will trap steam. This moist heat will destroy bacteria and help even the temperature throughout the food. Do not let the plastic wrap touch 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 get more even heating and 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. Microwave heating is not advised for warming or thawing breast milk. The excess heat can destroy proteins and other nutrients.
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:
- Other containers labeled specifically for microwave 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.
Eat Right—Academy of Nutrition and Dietetics
Food Safety and Inspection Service—United States Department of Agriculture
Canadian Partnership for Consumer Food Safety Education
Cooking meat safely. Clemson University Cooperative Extension Service website. Available at: http://www.clemson.edu/extension/hgic/food/food_safety/handling/hgic3580.html. Updated June 2011. Accessed February 14, 2017.
Cooking safely in the microwave oven. United States Department of Agriculture website. Available at: http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/appliances-and-thermometers/cooking-safely-in-the-microwave/cooking-safely-in-the-microwave-oven. Updated August 8, 2013. Accessed February 14, 2017.
Dietary guidelines for Americans 2010. US Department of Agriculture and US Department of Health and Human Services. Available at: http://www.health.gov/dietaryguidelines/dga2010/DietaryGuidelines2010.pdf. Accessed February 14, 2017.
Microwave cooking and nutrition. The Harvard Medical School Family Health Guide website. Available at: http://www.health.harvard.edu/staying-healthy/microwave-cooking-and-nutrition. Updated January 2015. Accessed February 14, 2017.
Microwave ovens and food safety. United States Department of Agriculture website. Available at: http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/appliances-and-thermometers/microwave-ovens-and-food-safety/ct_index. Updated August 8, 2013. Accessed February 14, 2017.
Storing and preparing expressed breast milk. American Academy of Pediatrics Healthy Children website. Available at: http://www.healthychildren.org/English/ages-stages/baby/breastfeeding/Pages/Storing-and-Preparing-Expressed-Breast-Milk.aspx. Updated September 9, 2016. Accessed February 14, 2017.
Last reviewed February 2017 by Michael Woods, MD, FAAP Last Updated: 3/6/2015