Fighting BAC!® by Chilling Out

After being out in chilly winter weather, coming into a warm, cozy home for a hot meal is comforting. But warm temperatures are comfortable for bacteria as well, and leftovers should not be left out under conditions where they can grow and cause foodborne illness. The safest place for leftovers - winter, spring, summer, or fall - is in the refrigerator where they can "chill out."

Foodborne bacteria grow rapidly when food is left out on the counter. Room temperatures fall in the "Danger Zone," between 40 and 140°F, where bacteria grow rapidly. It is estimated that as many as 9,000 deaths and 6.5 to 33 million illnesses yearly are directly linked to foodborne pathogens (bacteria and other microorganisms that cause illness). And many of these illnesses are caused by food that are left out on the counter at room temperature.

"CHILL: Refrigerate promptly" is one of the four principles of the Fight BAC!® campaign, a public-private partnership of industry, consumer groups, and government, including the U.S. Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS). 

Why is Chilling Important?
The reason chilling food is so important is that cold temperatures keep harmful bacteria from growing. Most bacteria and other pathogens grow very slowly, if at all, at refrigerator temperatures. Listeria monocytogenes is one exception. Freezing will stop growth, but does not destroy bacteria.

Campylobacter jejuni, Clostridium botulinum, Clostridium perfringens, Escherichia coli O157:H7, Salmonella, Streptococcus (Group A), Listeria monocytogenes, Shigella, and Staphylococcus aureus are nine prominent pathogens that concern food safety experts. When ingested on food, they or their toxic products can cause foodborne illness. Pathogenic bacteria can grow in just about any food, but prefer meat, poultry, seafood, eggs, and dairy products, as well as vegetables such as beans, grains, and other low acid foods.

To survive and reproduce, bacteria need time and the right conditions: food, moisture, and a warm temperature. Most pathogens grow rapidly at temperatures above 40°F. The ideal temperature for bacterial growth is between 40 and 140°F - what FSIS calls the "Danger Zone."

Some bacteria can double their numbers every 20 minutes at temperatures above 40°F. In 2 hours, these bacteria can become so great in number that they may cause an illness or form toxins that cause illness.

Pathogenic bacteria can be found on raw meat and poultry products. If these foods are refrigerated, most of the pathogens do not reproduce, and those that do, grow slowly. They will be destroyed when the product is cooked. If raw products are left out at warmer temperatures, these pathogens can produce a heat-stable toxin that might not be destroyed by cooking.

Pathogenic bacteria do not generally affect the taste, smell, or appearance of a food. In other words, one cannot tell that a food has been mishandled or is dangerous to eat. For example, food that has been left too long on the counter may be dangerous to eat, but could smell and look fine. If a food has been left in the "Danger Zone" for more than 2 hours, discard it, even though it may look and smell good. Never taste a food to see if it is spoiled.

Cold temperatures (below 40°F) can significantly slow down bacterial growth, but only heat (above 140°F) can destroy bacteria.

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How to Chill Cooked Foods to Keep Them Safe

  • Divide cooked foods into shallow containers for rapid cooling.
  • Stir soups and stews to speed the release of heat.
  • A large cut of meat or whole poultry should be divided into smaller pieces and wrapped separately or placed in shallow containers before refrigerating.
  • Cover containers and refrigerate within 2 hours.
  • Store in the refrigerator and use within 4 days, or freeze and use within 2 to 3 months for best flavor and moistness.

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January 1999

Last Modified Jun 16, 2013