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Rutgers scientists debunk '5-second rule'

Two Rutgers scientists debunked the “five-second rule” after testing various foods dropped on different types of flooring. – Photo by Georgette Stillman

Although Rutgers Professor Donald Schnaffner debunked the popular "five-second rule" surrounding dropping food on the floor, Donald Schaffner admits he has eaten a chocolate chip or two after they fell.

According to new research completed by Robyn Miranda, a graduate student in New Brunswick, and Donald Schaffner, professor and extension specialist in food science, bacteria does not wait five seconds before jumping on food that was dropped on the floor.

Schaffner, who has been doing cross-contamination research for about 15 years, said the inspiration behind this research began when he saw a press release about the five-second rule published by an English university.

“It was getting a lot of media attention and press and I went to the university website to learn more and what I discovered was they had done some research, but they didn’t have a paper,” Schaffner said. “It wasn’t peer reviewed.”

He said he was irritated by this because he dedicated much of his time to doing cross examination research in his laboratory, while others were getting attention for publishing something Schaffner “wouldn’t even qualify as science because it hadn’t been peer reviewed.”

Schaffner and Miranda sat down together and designed experiments that would prove or disprove the five-second rule.

Moisture on the floor largely contributes to bacteria that ends up on food, Schaffner said. Out of the four foods they studied, watermelon had the highest transfer of bacteria.

“Bacteria need moisture to transfer from one surface to another so a wet food is going to garner a lot more bacteria from the surface than a dry food,” Schaffner said. “We took a pure strain of bacteria we grew in the laboratory, and then we deliberately inoculated four different surfaces with those microorganisms.”

The team tested food using carpet, ceramic tile, wood and stainless steel surfaces, he said.

Before eating a piece of food from the floor, Schaffner urges people to ask themselves what the state of the floor is, what the likelihood the food is contaminated with bacteria, what the nature of the food in terms of moisture is and how long it was on the floor.

Schaffner also said the five-second rule is not just a popular culture notion but is serious science that contributes to people's scientific understandings.

“If everybody who ever ate food off the floor immediately got violently ill, pretty soon we would learn to stop doing that, but because we have often eaten food off the floor in the past and not gotten sick, people conclude it’s okay,” Schaffner said.

Keoni Nguyen, a School of Arts and Sciences sophomore, said she refuses to eat food off the floor, even if it’s been less than five seconds.

“I think it’s gross. I would just rather just get new food than pick up the food that fell,” Nguyen said.

Samantha Carney, a School of Arts and Sciences senior, said depending where she is and where the food was dropped would influence her decision to eat it or not.

Carney also said that if she does drop food and chooses to eat it, she will probably rinse it off first.

Colleagues from Clemson University have previously researched this topic, Schaffner said. But he believes this is the most comprehensive research done regarding the five-second rule.

“I like to think of our research as being very exhaustive. We looked at a lot more variables than they looked at in their studies,” said Schaffner. “We recently submitted for peer review and was recently accepted in a pretty good journal, probably the best journal that I can publish microbiology in today.”

Only after doing the research and getting it published in Applied and Environmental Microbiology did Schaffner believe this research was ready to be released to the press.

The research can be found online at American Society for Microbiology’s journal, Applied and Environmental Microbiology.

Nick Huber is a School of Arts and Sciences senior majoring in journalism and media studies. He is a staff writer for The Daily Targum. He can be found on Twitter @njhuber95Huber.


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