BAC DOWN! Keep Cold Foods Cold

(FN612, Revised Jan. 2024)

Give bacteria the cold shoulder. Find the Chill challenge, the chill solution and the cool rules in this brochure.

Lead Author
Lead Author:
Julie Garden-Robinson, Ph.D., R.D., L.R.D. Food and Nutrition Specialist, NDSU Extension Service
Web only
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The Chill Challenge

According to the U.S. Food and Drug Administration and U.S. Department of Agriculture Food Safety and Inspection Service, refrigeration at 40 F or below is one of the most effective ways to reduce the risk of foodborne illness. Microorganisms grow more rapidly at warmer temperatures, and research shows that keeping a constant refrigerator temperature of 40 F or below helps slow growth of these harmful microbes.

The Chill Solution

The best way to make sure your refrigerator is maintaining the recommended temperature at 40 F or below is to check it with a refrigerator thermometer. This type of thermometer usually is a separate tool that stays in the refrigerator and displays the actual temperature. It is not a numbered dial that helps you adjust temperature. Refrigerator thermometers are available at grocery, discount and hardware stores and are recommended for all home refrigerators.

When using a refrigerator thermometer, follow these important tips:

  • Always follow the thermometer manufacturer’s instructions for placing the thermometer in the refrigerator.
  • Make sure your refrigerator thermometer reads 40 F or below. Keep in mind that some normal events might cause your refrigerator thermometer to read higher than 40 F temporarily. These include:
  • Initial placement of the thermometer inside the refrigerator
  • A refrigerator door being open for an extended time
  • Hot foods recently placed in the refrigerator
  • The refrigerator’s automatic defrost cycle
  • Your refrigerator cycles on and off. According to NSF International (www.nsf.org), you should check the thermometer at the time your refrigerator compressor just turns on. This is when your refrigerator is at its highest temperature. If the thermometer reads above 40 F, adjust the control dial according to the manufacturer’s directions.

Cool Rules

  • Use a refrigerator thermometer to be sure the temperature is consistently 40 F or below. The ideal freezer temperature is 0 F or lower.
  • Use foil, plastic wrap, plastic bags or airtight containers designed for use with food to package foods for refrigerator storage. Freeze foods in containers or materials designed for freezer storage. Moisture- and vapor-proof materials are best.
  • Clean the refrigerator regularly. Remove spoiled foods immediately so decay cannot pass to other foods.
  • Refrigerate or freeze perishables, prepared food and leftovers within two hours of purchase or use. Always marinate in the refrigerator.
  • Never defrost food at room temperature. Thaw food in the refrigerator. For a quick thaw, submerge food in cold water in an airtight package or thaw in the microwave if you will be cooking it immediately.
  • Use or discard chilled foods on a regular basis. Don’t depend on maximum storage time. For more information, the “Food Storage Guide” (FN579) is available on the NDSU Extension website:
  • Don’t go too low. As you approach 32 F, ice crystals can begin to form and lower the quality of some foods, such as raw fruits, vegetables and eggs. A refrigerator thermometer will help you determine whether you are too close to this range.

For More Information

Contact your local NDSU Extension office or visit

The Partnership for Food Safety

NDSU Extension: