Safely preparing microwaveable foods

At Conagra Brands, we know that Americans' lives are busier than ever. And because of this, the microwave oven has become an indispensable tool in getting a hot meal on the family table fast.

So we're committed to providing safe, wholesome and convenient microwaveable foods. Our packaging, instructions and recipes are designed on the basis of in-depth research of microwaves and their cooking characteristics.

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Special care must be taken when cooking or reheating meat, poultry, fish and eggs to make sure they are prepared safely. According to the United States Department of Agriculture (USDA), microwave ovens can cook unevenly and leave "cold spots" where harmful bacteria can survive. For this reason, it is important to use a food thermometer and test food in several places to be sure it has reached the recommended safe temperature to destroy bacteria and other pathogens that could cause foodborne illness.

Food Safety Fundamentals

What should you keep in mind when preparing food in a microwave oven? Whether you're preparing food using traditional methods or in a microwave oven, the same food safety fundamentals apply.

Reducing or eliminating bacteria is one of the most important factors in avoiding foodborne illness. Bacteria can't be seen, smelled or touched, but they can be found on foods, on kitchen surfaces, on cooking vessels and utensils, and even on your hands.

Fight Bac!, a food safety education program, sums up how you can fight bacteria with its "Core Four Practices."

  • CLEAN: Wash hands and surfaces often.
  • SEPARATE: Don't cross-contaminate!
  • COOK: Cook to proper temperature.
  • CHILL: Refrigerate promptly, preferably in less than two hours.

For more details about how to eliminate bacteria, visit

Other sources of great information and food-handling tips can be found at, and

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Microwave Oven Basics

Below are answers to just a few of the questions you might have about using your microwave to cook your favorite foods.

The USDA is another great resource to learn more about how microwaves cook and safety tips you should keep in mind. You can learn more by downloading their brochure, "Microwave Ovens and Food Safety."

Q: What are the advantages to microwave cooking?

A. Naturally, the No. 1 advantage to preparing foods in a microwave is speed. Using a microwave oven is one of the fastest ways to prepare and heat foods.

Of course, like with a fast car, this speed must be managed carefully. For example, with the electronic keypad on most microwave ovens, it might be easy to add extra zeros and drastically extend the cooking time. If cooked in a microwave for too long, foods with a high fat or sugar content might heat to the point where they could catch fire. Carbohydrate-rich foods, such as potatoes, might become dried to the point where the center is scorched, but appear normal from the outside.

Q: What is a microwave-safe plate or container?

A: You only should use cookware that is specially manufactured for use in a microwave oven. These might include containers made of glass, ceramic or plastic. If they're safe to use in the microwave, they usually will be labeled that way.

Examples of items safe to use in the microwave oven*:

  • Any utensil or container specifically labeled for microwave use
  • Heatproof glass
  • Glass-ceramic
  • Oven cooking bags
  • Baskets (straw and wood) for quick warm-ups of rolls or bread. Line the basket with napkins to absorb moisture from food.
  • Most paper plates, towels, napkins and bags. For optimal safety, use white, unprinted materials.
  • Wax paper, parchment paper and heavy plastic wrap. Plastic wrap should not touch the food; and you should cut a small slit in it to allow steam to escape.
  • Heat-susceptor packaging, which is used in many packaged, microwaveable meals, including some made by ConAgra Foods

Items that are not safe to use in a microwave oven:

  • Cold storage containers: margarine tubs, cottage cheese containers and yogurt cartons, etc.
  • Brown paper bags and newspapers
  • Metal pans
  • Foam-insulated cups, bowls, plates or trays
  • China with metallic paint or trim
  • Chinese takeout containers with metal handles
  • Metal "twist ties" on package wrapping
  • Food wrapped in aluminum foil
  • Food cooked in any container or packaging that has warped or melted during heating

* Source: U.S. Department of Agriculture

Q: If metal shouldn't be used, why do I sometimes see instructions that use foil?

A: Under certain circumstances, it can be safe to use small amounts of aluminum foil in a microwave oven. However, always consult the owner's manual of your particular microwave oven and follow the manufacturer's recommendations for aluminum foil.

You can find more details about how you should and should not use aluminum foil on the U.S. Department of Agriculture's website.

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Handling, Storing and Preparing Frozen Microwaveable Foods

Q: Why do I need to keep frozen foods frozen?

A: Unless the package instructions state otherwise, frozen microwaveable foods must be kept frozen until you are ready to prepare them for both food safety and food quality reasons. For example, if a ready-to-cook food is thawed before use, it could give any bacteria present in raw ingredients time to multiply. It also is best to avoid partially thawing and refreezing foods. This causes moisture to be lost from the food and leads to the formation of ice crystals. The moisture loss indicated by ice formation might affect how the food cooks, as well as the overall quality. Ideally, frozen foods should be placed in a freezer at 0°F as soon as they're brought home from the store and kept there until used.

Q: Why is it so important to carefully follow preparation instructions?

A: Although some microwaveable foods only require heating before consumption ("ready-to-heat"), some foods contain raw ingredients that must be cooked ("ready-to-cook"). For these, making sure the food reaches an appropriately safe temperature is vital for optimum safety. Food product manufacturers create preparation instructions specifically to produce optimum food quality and safety. These instructions might include specific cooking and standing times to achieve the desired result. Any deviations could result in food that has residual bacteria or that simply is not as high quality as it could be.

Q: What is "standing time" and how important is it?

A: The cooking instructions on our packaging include standing time because it's actually a part of the cooking process. Some foods need this additional cooking time to ensure that the food is thoroughly cooked for safety and quality. This also allows the food to achieve optimum quality without overcooking.

Q: What is the wattage of my oven and why is it important?

A: The higher the wattage of a microwave oven, the faster it will cook food. For optimum food safety, it's important to know the wattage of your oven in order to adjust cooking times, if necessary. If you have a very low wattage oven, it might even be best not to prepare certain foods in your microwave, and you should use conventional methods instead. Remember, microwave ovens that are 700 watts or lower will only heat — not cook — your food. A microwave oven must be 1,100 watts to cook food.

If you don't know the wattage of your microwave oven, look 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. If you still can't find the wattage, you should contact the manufacturer of your microwave.

One way to estimate the wattage of your microwave oven is to do a "time-to-boil" test.*

Measure a cup of water in a 2-cup glass measuring cup. Add ice cubes and stir until the water is ice cold. Discard ice cubes and pour out water until you are left with 1 cup. Set the microwave on high for 4 minutes and watch the water through the window to see when it boils.

  • If water boils in less than 2 minutes, it is a very high wattage oven — 1,000 watts or higher.
  • If water boils in 2 1/2 minutes, it is a high wattage oven — about 800 watts or higher.
  • If water boils in 3 minutes, it is an average wattage oven — 650 to 700 watts or higher.
  • If water boils in more than 3 minutes or not by 4 minutes, it is a slow oven — 300 to 500 watts.
  • Source: U.S. Department of Agriculture

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Q: How should I check the temperature of microwaved foods?

A: You can use an ordinary food thermometer to check if your food has reached a safe internal temperature. Unless the food thermometer is labeled safe for microwave cooking, do not leave it in the food during microwaving. Instead, use an instant-read food thermometer to test the temperature of the food after removing it from the microwave oven.

Check the food's temperature after the cooking time and standing time, if any, have elapsed. Make sure to insert the thermometer into different locations within the food to make sure the proper temperature has been reached throughout.

For a list of safe cooking temperatures, visit

Q: What should I do if I want to save leftover portions?

A: Follow food safety guidelines as you would for any other food. Transfer food to a clean storage container and refrigerate within two hours. Don't save and reuse the microwaveable container that came with your food to heat other foods. Discard containers when you're finished with them.