Researchers Reveal the Truth About the ‘Five Second Rule’

Unfortunately, researchers have now proven that the ‘five second rule’ for eating food off the floor is, in fact, not scientifically accurate.

The time it takes bacteria to transfer onto food can actually be less than one second, according to researchers at Rutgers University led by professor Donald Schaffner, an extension specialist in food science.

A ‘Pop Culture’ Myth

“The popular notion of the ‘five-second rule’ is that food dropped on the floor, but picked up quickly, is safe to eat because bacteria need time to transfer,” said Professor Schaffner.

“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,” he added.

Their first findings confirmed that moisture, surface type and the fabled contact time all have a part to play in cross contamination.

Those variables were explored further by testing four food types (watermelon, bread, bread and butter, and gummy sweets), four surfaces (ceramic tiles, wood, stainless steel and carpet) and four contact times (less than one second, 5 seconds, 30 seconds, 300 seconds) at the university labs in New Brunswick.

So what did they find?

Watermelon was the most easily contaminated food, which led researchers to conclude that moisture is the strongest player in terms of cross contamination. If you do drop your watermelon, though, make sure it’s on a carpet, which had lower transfer rates than stainless steel and ceramic tiles. Gummy sweets were found to be the safest food to drop.

“Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer,” Professor Schaffner said. “Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.”

He went on to say that, in essence, the five second rule is an oversimplification of what actually happens when bacteria transfer from a surface to food.

So in a way we were right all along. Kind of.

Author: Ryan Child

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