Eating food off the floor is not safe, for bacteria may transfer in less than a second, says a study that disproves the widely accepted notion that it is all right to scoop up food within a “safe" 5-second window.

Professor Donald Schaffner from Rutgers University, US, found that moisture, type of surface and contact time all contribute to cross-contamination. In some instances, the transfer begins in less than a second, he said. “The popular notion of the ‘5-second rule’ is that food dropped on the floor, but picked up quickly, is safe to eat because bacteria need time to transfer," Prof. Schaffner said.

The researchers tested four surfaces—stainless steel, ceramic tile, wood and carpet—and four different foods (watermelon, bread, bread and butter and gummy candy). They also looked at four different contact times—less than one second, 5, 30 and 300 seconds. Watermelon had the most contamination, and gummy candy the least. “Transfer of bacteria from surfaces to food appears to be affected most by moisture," said Prof. Schaffner.

The study was published in the Applied And Environmental Microbiology journal.

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