Food Safety with Appliance Thermometers

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One of the critical factors in controlling bacteria in food is controlling temperature. Pathogenic microorganisms grow very slowly at temperatures below 40 °F, multiply rapidly between 40 and 140 °F, and are destroyed at temperatures above 140 °F.

For safety, foods must be held at proper cold temperatures in refrigerators or freezers and they must be cooked thoroughly. But how would a consumer know if the refrigerator was cold enough, or if the oven was heating at the proper temperature?

Appliance thermometers are specially designed to measure the temperature of the air in either the refrigerator/freezer or the oven. Some refrigerator thermometers have long metal probes and are similar in appearance to food thermometers. Other refrigerator thermometers, and most oven thermometers, are designed to hang from a wire rack or sit on a shelf.

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Using Appliance Thermometers

Refrigerator/Freezer Thermometers
Refrigerator/freezer thermometers are specially designed to provide accuracy at cold temperatures.

For safety, it is important to verify the temperature of refrigerators and freezers. Refrigerators should maintain a temperature no higher than 40 °F. Frozen food will hold its top quality for the longest possible time when the freezer maintains 0 °F.

An appliance thermometer can be kept in the refrigerator and freezer to monitor the temperature at all times. This can be critical in the event of a power outage. When the power goes back on, if the refrigerator is still 40 °F and the freezer is 0 °F or below, the food is safe.

  • To measure the temperature in the refrigerator:
    Put the thermometer in a glass of water and place in the middle of the refrigerator. Wait 5 to 8 hours. If the temperature is not 38 to 40 °F, adjust the refrigerator temperature control. Check again after 5 to 8 hours.
  • To measure the temperature in the freezer:
    Place the thermometer between frozen food packages. Wait 5 to 8 hours. If the temperature is not 0 to 2 °F, adjust the freezer temperature control. Check again after 5 to 8 hours.

Oven Thermometers
An oven thermometer can be left in the oven to verify that the oven is heating to the desired temperatures. When cooking meat and poultry, it is important that the oven be set at 325 °F or higher. These thermometers can measure temperatures from 100 to 600 °F.

To check the accuracy of an oven, hang the oven thermometer from a rack in the center of the oven (you may have to adjust the oven racks). Set the oven for 325 to 350 °F and allow it to preheat. Once the oven has reached the set temperature, open the oven door and read the thermometer. The oven maintains its temperature by cycling on and off, especially if the door has been opened. Check the temperature again after 5 minutes.

If the oven is not maintaining the set temperature, the oven thermostat will have to be adjusted by a service center representative authorized by the manufacturer. However, if, after testing the oven temperature at several settings (325, 350, 375, and 400 °F), it is consistently high or low by the same amount (say, 25 °F), this can be factored into the temperature setting. For example, if you know that your oven runs “hot” by 25 °F and you need to bake something at 350 °F, set the oven for 325 °F. Always check the oven thermometer to verify the temperature.

Microwave Oven Probes
A microwave oven probe can be plugged into the microwave and inserted in the food being cooked. Some microwaves can be programmed to cook the food until a desired temperature is reached. Check the owner’s manual for more information. Some thermometers are specially designed to be used in the microwave oven, but most food thermometers are not microwave-safe. Check the packaging instructions for more information.

Additional Appliances and Thermometers Resources

Appliance Thermometers | PDF
Appliance thermometers help you know if the refrigerator is cold enough, or if the oven is heating at the proper temperature.

Cooking Safely in the Microwave Oven | PDF | En Español | En Español PDF
This fact sheet lists the basics for safe microwave cooking or reheating.

Deep Fat Frying and Food Safety | PDF
Important guidelines to prevent deep fat frying injuries at home, and to ensure that food is cooked to a safe temperature.

Is It Done Yet? | PDF | En Español
Learn how to use a food thermometer—it’s not just for turkey anymore! Includes recommended internal temperatures and a recipe for safe, delicious, Fiesta Burgers.

Kitchen Thermometers | PDF | En Español | En Español PDF
An illustrated guide to these essential tools, which come in several types and styles and vary in level of technology and price.

Microwave Ovens and Food Safety | PDF
This comprehensive fact sheet answers all your microwave questions.

Refrigeration & Food Safety | PDF
A refrigerator is one of the most important pieces of equipment in the kitchen for keeping foods safe.

Slow Cookers and Food Safety | PDF | En Español | En Español PDF
Used correctly, this counter top appliance is safe and convenient.

Specialty Devices and Safe Food Handling | PDF | En Español | En Español PDF
Facts about thawing trays, solar box cooking, disposable temperature indicators, thermoelectric cooler/warmers.

Thermy™ Coloring Page (PDF Only)
Kids, print a copy and color it any way you like.