Everyone has seen it happen; most people have done it themselves. You drop a piece of food on the ground, only to pick it up and exclaim, “Five-second rule!” before popping it back into your mouth. Many people have been raised around the idea that when food is dropped on the floor, it is still considered “clean” as long as it’s picked up within five seconds. This concept is known as the “five-second rule.”

The thought process behind the five-second rule is that it takes time before germs and bacteria can be transferred from the surface on which the food was dropped to the food itself. In September 2016, Rutgers professor Donald Schaffner and Robyn Miranda, one of Schaffner’s graduate students, decided it was time to scientifically determine whether the five-second rule was a myth or a fact. “We decided to look into this because the practice is so widespread. The topic might appear ‘light’ but we wanted our results backed by solid science,” Schaffner explained.

An extensive experiment was designed involving testing out different foods on different surfaces with different time intervals of surface contact. Watermelon, bread, bread with butter, and gummy candy were the four foods tested by Schaffner and Miranda in order to provide a variety of moisture content and texture. Stainless steel, ceramic tile, wood, and carpet were used as the four surfaces, all of which can be found in most households. Finally, the research team used four different lengths of “drop time:” less than one second, the standard five seconds, 30 seconds, and 300 seconds. The bacteria observed was Enterobacter aerogenes, a bacteria similar to Salmonella that naturally occurs in the human digestive system.

The results Schaffner and Miranda gathered were not what most people want to hear. It turns out bacteria doesn’t need much time at all to get onto your food, and as Schaffner stated, “Bacteria can contaminate instantaneously.”

However, this doesn’t mean the five-second rule is entirely invalid. To some degree, time does impact how much bacteria can contaminate your food. But, there are many other factors to consider as well. Bacteria travels through moisture, so dryer foods are likely to have smaller amounts of bacteria when dropped. Also, surface texture greatly influences the rate of bacteria transfer. Carpet transferred the least bacteria; the smoother steel and tile surfaces transferred the most.  

Family and Consumer Sciences teacher Marta Brooks admits to using the five-second rule from time to time in her personal life, but added, “If you are preparing something for a group of people, I would not use anything that’s on the floor.”

“[The food] is going to pick up something, and that something might lead to foodborne illness,” Brooks elaborated.

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Source: http://news.rutgers.edu/research-news/rutgers-researchers-debunk-%E2%80%98five-second-rule%E2%80%99-eating-food-floor-isn%E2%80%99t-safe/20160908#.WE32fsszXxM