The ‘five second rule’ seems to have been around forever, and is commonly used as an excuse for people to still eat the food they have inadvertently dropped. Now scientists have put this theory to the test, measuring just how long it would take for bacteria to stick to foods with different variables after dropping on the floor.
Researchers as Manchester Metropolitan University examined cooked pasta, a biscuit, bread with jam and fried food to determine whether bacteria would latch to them in less than five seconds. The reasoning behind these foods is that they are all commonplace food items and they contain different amounts of water, which is known to sustain bacterial growth.
The results proved that the foods with higher salt or sugar contents were least likely to pick up harmful bacteria. The salty ham and the sugary bread and jam were retrieved from the floor within three seconds, and showed very little sign of bacterial growth. However when the dried fruit and the cooked pasta were retrieved after three seconds they both showed signs of klebsiella. Klebsiella is a strain of bacteria that can lead to a wide range of diseases, including pneumonia, urinary tract infections, septicaemia and soft tissue conditions. More alarming is how quickly the foods picked up these dangerous bacteria, with the dried fruit picking it up in five seconds, and the cooked pasta in just three seconds.
While this study clearly demonstrates just how quickly bacteria can spread in certain types of food, the type of floor the food is dropped on is still worth taking into account, as some surfaces are far cleaner than others. New York Times writer Harold McGee wrote about the topic in 2009 after testing a bologna sandwich that was put in contact with salmonella. “If you drop a piece of food, pick it up quickly, take five seconds to recall that just a few bacteria can make you sick, then take a few more to think about where you dropped it and whether or not it’s worth eating.”
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