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U.S. Department of Health and Human Services


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List of Terms: D

Return to Comprehensive List of Terms


Temperature Chart
Recommended Safe Cooking

>Danger Zone 
The temperature range in which most bacteria can grow.

Food Safety Implication: Some bacteria can double their numbers within minutes and form toxins that cause illness within hours. That's why it's important to keep food below or above the temperatures at which bacteria can grow. Usually this is below 40° F (4° C) (some pathogenic bacteria can grow at 32° F [0° C] or above 140° F [60° C]).

Food Safety Precautions:

  • Cook food to safe internal temperatures (see the Safe Cooking Temperatures chart at right). Use a food thermometer to check.
  • Keep hot foods hot. Maintain hot cooked food at 140° F (60° C) or above.
  • Reheat cooked food to 165° F (74° C). Never let the temperature fall below 140° F (60° C).
  • Keep cold foods cold. Store food in the refrigerator (40° F [4° C] or below) or freezer (0° F [-18° C] or below).
  • Don't leave food out at room temperature for more than 2 hours.

Note: For more about handling foods safely, see the 4 Cs section.


>Deoxyribonucleic Acid (DNA)
A molecule that forms a double helix composed of units called nucleotides. Each nucleotide is composed of a sugar (deoxyribose) connected to 1 of 4 nitrogenous bases by a phosphate molecule. DNA encodes genetic information in all living cells and in many viruses (also see Nucleic Acid and Ribonucleic Acid).

DNA Model
Photo: James A. Sullivan/Cells Alive
A bacterium's genetic information is contained
on a ladder-like DNA molecule like the one above.

Food Safety Implication: In bacteria, the DNA molecule encodes the information for factors that enable it to grow, reproduce, and confer virulence (ability to cause illness). Each organism's DNA can be used to distinguish it from related organisms. When there is an outbreak of foodborne illness, epidemiologists can determine the source of bacteria in foods by examining the pathogen's DNA "fingerprint."

The Fabulous Five

The discovery of the double-helical structure of DNA began in 1951. The 5 people responsible for its discovery were:

  • Francis Crick
  • Rosalind Franklin
  • Linus Pauling
  • James Watson
  • Maurice Wilkins


> Disinfectant (see Sanitizer)