- The FDA recommends that all perishables left at room temperature for more than two hours be discarded.
- Bacteria grow most rapidly between 40 degrees Fahrenheit (4.4 degrees Celsius) and 140 degrees Fahrenheit (60 degrees Celsius), doubling in amount every 20 minutes.
- Many bacteria produce heat-resistant toxins that cannot be destroyed by reheating at a high temperature.
It happens. You finish your dinner and get distracted by your favourite TV show or a phone call from mum, only to realise hours later that your leftovers are still sitting on the kitchen counter. Are they salvageable or should you toss tomorrow’s lunch into the trash? The answer depends on how long your food sat out at room temperature.
The US Food and Drug Administration (FDA) recommends abiding by the “2-Hour Rule”
The “2-hour rule” states that perishables left at room temperature for more than two hours should be discarded. If the food is being kept in an area that is 90 degrees Fahrenheit (32.2 degrees Celsius) or above, leftovers should be refrigerated to 40 degrees Fahrenheit (4.4 degrees Celsius) or below within one hour. This may seem like a relatively short amount of time for food to become unsafe.
The US Department of Agriculture (USDA) explains, however, that bacteria exists everywhere in nature, and it is not uncommon for trace amounts staphylococcus aureus, salmonella enteritidis, E. coli, Campylobacter, clostridium perfringens, or Bacillus cereus to be present in food.
Bacteria grow most rapidly between 40 degrees Fahrenheit (4.4 degrees Celsius) and 140 degrees Fahrenheit (60 degrees Celsius) the temperature the USDA refers to as the “danger zone” and can take as little as 20 minutes for the number of bacteria to double.
According to experts at the University of Nebraska-Lincoln, just one bacterium can grow to over 2,097,152 bacteria in seven hours when kept at room temperature. Therefore before serving, it’s safest to keep your cold food in the refrigerator 40 degrees Fahrenheit (4.4 degrees Celsius) or below, and your hot dishes in the oven set at 200 degrees Fahrenheit (93.3 degrees Celsius) to 250 degrees Fahrenheit (121.1 degrees Celsius). If you are serving food buffet-style, the FDA recommends keeping hot food in chafing dishes, slow cookers, or warming trays at or above 140 degrees Fahrenheit (60 degrees Celsius), and cold food on ice. Anything that is kept at room temperature should be refrigerated within two hours.
There is a common misconception that if you leave your food out too long, you can kill the bacteria by reheating it
The Washington State Department of Health debunks that myth explaining that staphylococcus and bacillus cereus produce heat-resistant toxins that cannot be destroyed with high temperatures.
The FDA’s “Bad Bug Book” warns that staphylococci exist in virtually all foods that are handled directly by humans or are of animal origin, and is present in the nasal passages, throats, hair, and skin of at least 50% of healthy individuals.
Some foods are more susceptible to harmful bacteria than others
Foods that are most associated staphylococcal food poisoning, include meat, poultry, egg products, and foods that are eaten cold such as salads (specifically egg, tuna, chicken, potato, and macaroni), cream-filled pastries, sandwich fillings, and milk and dairy products. Anytime you leave food out too long, you risk food poisoning which can lead to fever, diarrhoea, vomiting, dehydration, and in rare cases paralysis, meningitis, and death.
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