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Food Safety and Inspection
Service United States Department of Agriculture Washington, D.C. 20250-3700 |
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Food Safety and Inspection
Service United States Department of Agriculture Washington, D.C. 20250-3700 |
Frequently Asked Questions
Updated April 10, 2002
What are spoilage bacteria?Spoilage bacteria are microorganisms too small to be seen without a microscope that cause food to deteriorate and develop unpleasant odors, tastes, and textures. These one-celled microorganisms can cause fruits and vegetables to get mushy or slimy, or meat to develop a bad odor.
Do spoilage bacteria make people sick?Most people would not choose to eat spoiled food. However, if they did, they probably would not get sick.
Pathogenic bacteria cause illness. They grow rapidly in the "Danger Zone" -- the temperatures between 40 and 140 °F -- and do not generally affect the taste, smell, or appearance of food. Food that is left too long at unsafe temperatures could be dangerous to eat, but smell and look just fine. E. coli O157:H7, Campylobacter, and Salmonella are examples of pathogenic bacteria.
How do bacteria spoil food?There are different spoilage bacteria (see question below) and each reproduces at specific temperatures. Some can grow at the low temperatures in the refrigerator or freezer. Others grow well at room temperature and in the "Danger Zone." Bacteria will grow anywhere they have access to nutrients and water. Under the correct conditions, spoilage bacteria reproduce rapidly and the populations can grow very large. In some cases, they can double their numbers in as little as 30 minutes. The large number of microorganisms and their waste products cause the objectionable changes in odor, taste, and texture.
What are the different types of spoilage bacteria?Mesophiles (MEZZ-oh-files) prefer moderate temperatures ranging from 41 to 50 ° F. In a favorable medium, these bacteria double their numbers in as little as 30 minutes.
Psychrotrophs (SIGH-crow-trowfs) can grow at about 32 ° F (the freezing temperature of water), but grow best at moderate temperatures.
Thermophiles prefer a warmer temperature. The optimum temperature for growth is usually between 131 and 149 ° F. Some can grow in temperatures as low at 95 ° F or as high as 167 to 194 ° F.
Psychrophiles (SIGH-crow-files) prefer low temperatures. They can grow at temperatures of 32 ° F or lower, but they can also thrive at moderate temperatures of 59 to 68 ° F. They are quite common in environments where the temperature remains consistently low. They are mainly of marine origin and have little consequence in food.
For Further Information, Contact:
FSIS Food Safety Education Staff
Meat and Poultry Hotline:
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