Safe Microwave Cooking
Microwave ovens don’t 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, which 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 the cook 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 uniform pieces 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. (Note: Don’t 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 doesn’t, 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 uniform heating and killing of bacteria.
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 immediately after defrosting. Never partially cook food and store it for later use.
- Large cuts of meat should be cut smaller if possible. If 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 the food has reached a temperature where the bacteria have been destroyed. Safe cooking temperatures:
- Red meat: 160˚F
- Poultry: 180˚F
- Pork: 160˚F (medium), 160˚F (well)
- Leftovers: 165˚F
- Cooking a stuffed poultry in a microwave is not recommended.
It is important to remember that a microwave is not a sterilizer and it cannot be used to sterilize jars or bottles. Also, one need to 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 micro-waved briefly, there may be hot spots within the formula.
It is important to cook food in a container that won’t 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 paper, Styrofoam, or plastic
- Storage containers such as margarine tubs and take-out containers
Plastic wraps are commonly used to cover the 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 doesn’t 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 don’t 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 (stove or conventional oven).
There has been some speculation that microwaved food can be harmful to people. There is no credible experimental evidence to back up that statement.
American Dietetic Association
US Department of Agriculture
Canadian Partnership for Consumer Food Safety Education
Microwave Ovens and Food Safety
Cooking meat safely. Clemson University Cooperative Extension Service website. Available at: http://hgic.clemson.edu/factsheets/HGIC3580.htm . Accessed April 8, 2007.
Cooking safely in the microwave oven. United States Department of Agriculture website. Available at: http://www.fsis.usda.gov/Fact_Sheets/Cooking_Safely_in_the_Microwave/index.asp . Accessed on April 8, 2007.
Microwave cooking: does it destroy nutrients in vegetables? The Mayo Clinic website. Available at: http://www.mayoclinic.com . Accessed April 8, 2007.
Plastic wraps: are they safe in your kitchen? The American Dietetic Association website. Available at: http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/home_4326_ENU_HTML.htm . Accessed April 8, 2007.
Last reviewed April 2007 by Marcin Chwistek, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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