Aug 30, 2016 | EcoSure Food Safety Monitor

By Miriam Eisenberg, MS, RD, CP-FS

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Just a bit of fun research…thanks to Barfblog (yes, it’s a real site –– check it out ), I am sharing research findings on the old five-second rule – that food dropped on the floor and picked up before five seconds is still safe to eat. Or is it?

Professor and food microbiologist Donald W. Schaffner and graduate student Robyn Miranda of Rutgers University took a closer look at "the rule.” Research results show that no matter how fast you pick up food that falls on the floor, you will pick up bacteria with it. Findings of the Is The Five-Second Rule Real report appeared online this month in the American Society for Microbiology’s journal Applied and Environmental Microbiology.

Following up on two previous reports that were not from peer-reviewed journals that said food from the floor could be fine, Professor Schaffner noted that even though the five-second rule is a bit of folklore it still raised important public health issues that demanded closer scrutiny. He cited research by the Centers for Disease Control and Prevention (CDC), which found that surface cross-contamination was the sixth most common contributing factor out of 32 in outbreaks of food-borne illnesses.

Professor Schaffner and Ms. Miranda, tested four surfaces—stainless steel, ceramic tile, wood and carpet—and four different foods—cut watermelon, bread, buttered bread and strawberry gummy candy. The foods were dropped from a height of 5" onto surfaces treated with a bacterium with characteristics similar to Salmonella.

The researchers tested four contact times — less than 1 second and 5, 30 and 300 seconds. A total of 128 possible combinations of surface, food and seconds were replicated 20 times each, yielding 2,560 measurements.

The research found that the five-second rule has some validity in that longer contact times resulted in transfer of more bacteria. But no fallen food escaped contamination completely. “Bacteria can contaminate instantaneously,” Professor Schaffner said in a news release. Carpet had a very low rate of transmission of bacteria compared with tile and stainless steel; transfer rates from wood varied.

he composition of the food and the surface on which it falls matter as much if not more than the length of time it remains on the floor, the study found. Watermelon, with its moisture, drew the highest rate of contamination and the gummy candy the least.

In conclusion, just as food dropped on the restaurant kitchen floor would never be served to foodservice customers, whenever or wherever you drop food, throw it away.