The Effects of Temperature on Foodborne Bacteria

Although bacteria are everywhere around us, it is only when they find a favorable environment that they multiply and cause harm. In food left at room temperature for 8 hours, a single bacterium can grow to a population of more than 16 million. According to the Centers for Disease Control and Prevention, an estimated 48 million people get sick, 128,000 are hospitalized and 3,000 die from foodborne diseases (both bacterial and viral) every year. Keeping food at the right temperature will decrease the incidence of foodborne illness.

Optimal Growth Temperature

• Bacteria can grow within a wide range of temperatures from 14 degrees Fahrenheit to more than 212 degrees Fahrenheit. Foodborne bacteria grow most rapidly at temperatures between 40 to 140 degrees, referred to as the "Danger Zone" by the USDA. Foodborne bacteria thrive at the human body temperature of 98.6 degrees.

At Low Temperatures

• At refrigerator temperatures of 40 degrees or below, the activity of foodborne bacteria slows but does not stop. The slow and steady growth of bacteria spoils foods stored at this temperature for prolonged periods. Full activity of these foodborne bacteria resumes when the food reaches room temperature. Foodborne bacteria are inactive at freezing temperatures and frozen food is safe so long as the storage temperature is at or below 0 degrees; however, bacteria are fully active in thawed foods and pose the same health concerns as bacteria in fresh foods.

At High Temperatures

• A temperature higher than 140 degree (the upper limit favorable for their growth) kills foodborne bacteria. Cooking and reheating foods at temperatures between 145 to 165 degrees ensures the destruction of bacteria. When cooking, it is important to ensure that both the internal and external parts of food reach this temperature. Uneven cooking temperatures within cooked food allow bacteria harboring inside the food to remain viable. Cooking food at high temperature for an extended time destroys all foodborne bacteria.

Common Foodborne Bacteria

• In its 2011 report, the Centers for Disease Control and Prevention reported Campylobacter, Salmonella, Clostridium perfringens, Staphylococcus aureus and E.coli O157:H7 as the most common foodborne bacteria.