The Grapevine

Is It Safe To Follow The Five-Second Rule? How Fast Bacteria Gets On Food

You may have grown up believing the “five-second rule,” which says food that's just fallen on the floor is safe to eat, but according to a new study from Rutgers University, the rule may need some adjusting. The research suggests that germs can find their way onto your food no matter how quickly you’re able to pick it up off the ground.

The five-second rule does not apply to everything. Factors such as moisture, type of surface, and contact time mean that bacteria can contaminate a fallen object in less than one second. So, you don't want to cry over spilled milk, but you also shouldn't drink it. 

gummibar Gummy candies have the least amount of bacteria contamination. But what happens if they fall on the floor? Photo Courtesy of Pixabay

"The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," said study author Donald Schaffner in a recent press release. "Bacteria can contaminate instantaneously."

For the study, the researchers tested four surfaces — stainless steel, ceramic tile, wood and carpet — and four different foods, including watermelon, bread, bread and butter, and gummy candy. They also looked at four different contact times: less than one second, five, 30, and 300 seconds. They used two media, tryptic soy broth or peptone buffer, to grow Enterobacter aerogenes, a nonpathogenic "cousin" of Salmonella naturally occurring in the human digestive system.

Results showed that the wetter the food, the higher the risk of transfer; watermelon had the highest levels of contamination while gummy candies had the least. Where the food was dropped also played a role in contamination levels; carpet had very low transfer rates compared with those of tile and stainless steel.

Although debunking the five-second rule may not exactly be hard science, many of the bacteria found on floor surfaces could be dangerous to our health and cause sickness. And while these findings may not change your habit of eating food off the floor, at least now you can be aware of the risks involved.

Source: Miranda RC, Schaffner D. Longer Contact Times Increase Cross-Contamination of Enterobac Aerogenes from Surfaces to Food. Applied And Environmental Microbiology . 2016

Read More:

5-Second Rule Is Real: NASA Engineer Proves You Can Eat That Cookie After It Falls On The Ground: Read Here

5-Second Rule May Buy You Time With Dropped Food, But You're Still Taking A Risk: Read Here

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