The shape and consistency of food affects how evenly they heat in microwave ovens. Food with symmetrical shapes, especially round or oval, and with even thickness (less that 1 inch) generally heat the most uniformly. For thicker portions, better results may be obtained with reduced power for longer periods such that the outer portions don’t overcook before the center is heated thoroughly. To promote uniform cooking, arrange food items evenly in a covered dish and add some water, if the food is fairly dry, to promote more even absorption of microwaves. Bone can shield meat from thorough cooking, so, where possible, debone large pieces of meat. It is important that foods be stirred, rotated, and inverted, if possible, halfway through cooking for more even distribution of microwaves and heat throughout the food. Even if a turntable is used, it is best to place the food off-center and to stir foods top to bottom or turn foods over, if possible.
Use microwave-safe containers. Do not use foam containers for cooking or reheating foods unless labeled microwave-safe. Cover the dish with a lid, microwave-safe plastic wrap, or a clean, unprinted, white paper towel, but leave a small opening for steam to escape. Allow enough space between the food and the plastic wrap so the wrap doesn’t touch the food. The steam that is created by using a lid will help heat the food more evenly and will also help destroy any harmful bacteria.
Just as other types of ovens, microwave cooking can destroy bacteria and other pathogens; however, food can cook less evenly than in conventional ovens, resulting in cold spots, due to factors described earlier. For best results in both the quality and safety of frozen or refrigerated foods, consumers should follow the cooking instructions on product labels and observe the standing times, if provided. Adjustments to the cooking time, due to oven wattage or other factors, may be necessary to reach the desired temperature before serving. For frozen or refrigerated foods that do not have labeled cooking instructions, it is suggested that the following cooking temperatures—as recommended by the United States Department of Agriculture (USDA)—be reached in all parts of the food.
- Ground meats: 160° F (71° C)
- Ground poultry: 165° F (74° C)
- Beef, veal, and lamb steaks, roasts, and chops: 145° F (63° C)
- All cuts of fresh pork: 160° F (71° C)
- Poultry: 165° F (74° C)
- Eggs and dishes containing eggs (i.e. casseroles, soufflés, etc.): 160° F (71° C)
- Fish/seafood: 145° F (63° C)
- Foods to be reheated that have previously been cooked and cooled by the consumer (i.e. leftovers): 165° F (74° C)
After the cooking time has ended and proper standing time has been allowed, the temperature of the food should be checked. Remove the food from the microwave and use a food thermometer to check the food in several places to ensure that a safe temperature has been reached throughout. Keep in mind all microwave ovens vary in power.
* Do not leave the thermometer in the food while microwaving, unless the thermometer is labeled as safe for microwave use, as this may result in arcing and could be a potential fire hazard.