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The temperature range in which food-borne bacteria can grow is known as the danger zone. Food safety agencies, such as the United States' Food Safety and Inspection Service (FSIS), define the danger zone as roughly 4 to 60 °C (39 to 140 °F). The FSIS stipulates that potentially hazardous food should not be stored at temperatures in this range in order to prevent foodborne illness (for example, a refrigerator's temperature must be kept below 4 °C (40 °F)), and that food that remains in this zone for more than two hours should not be consumed. Foodborne microorganisms grow much faster in the middle of the zone, at temperatures between 21 and 47 °C (70 and 117 °F).
Food-borne bacteria, in large enough numbers, may cause food poisoning, symptoms similar to gastroenteritis or "stomach flu" (a misnomer, as true influenza primarily affects the respiratory system). Some of the symptoms include stomach cramps, nausea, vomiting, diarrhea, and fever. Food-borne illness becomes more dangerous in certain populations, such as people with weakened immune systems, young children, the elderly, and pregnant women. In Canada, there are approximately 11 million cases of food-borne disease per year. These symptoms can begin as early as shortly after and as late as weeks after consumption of the contaminated food.
Time and temperature control plays a critical role in food safety. To prevent time-temperature abuse, the amount of time food spends in the danger zone must be minimized. A logarithmic relationship exists between microbial cell death and temperature: a significantly large number of cells may survive slightly lower temperatures. In addition to reducing the time spent in the danger zone, foods should be moved through the danger zone as few times as possible when reheating or cooling.
Foods that are potentially hazardous inside the danger zone: