In a very interesting development, a latest study has debunked the belief that it was safe to eat food fallen on the floor if picked up within “five seconds”.
Professor Donald W Schaffner, a food microbiologist at Rutgers University in New Jersey, said a two-year study he led concluded that no matter how fast you pick up food that falls on the floor, you will pick up bacteria with it.
The findings in the report — “Is the Five-Second Rule Real?” — appeared online this month in the American Society for Microbiology’s journal, Applied and Environmental Microbiology.
Researchers at Aston University’s School of Life and Health Sciences in England reported in 2014 that food picked up a few seconds after being dropped is “less likely to contain bacteria than if it is left for longer periods of time,” giving rise to news accounts suggesting that eating the food might be harmless. Those findings, and research done at the University of Illinois in 2003, did not appear in a peer-reviewed journal, Professor Schaffner noted.
Even though the five-second rule is a bit of folklore, it still raised important public health issues that demanded closer scrutiny, he said. He cited research by the Centers for Disease Control, 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 a master’s thesis student, Robyn C Miranda, tested four surfaces — stainless steel, ceramic tile, wood and carpet — and four different foods: cut watermelon, bread, buttered bread and strawberry gummy candy. They were dropped from a height of five inches onto surfaces treated with a bacterium with characteristics similar to salmonella.
The researchers tested four contact times — less than one second and five, 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 explained.
Carpet had a very low rate of transmission of bacteria compared with tile and stainless steel; transfer rates from wood varied.
The 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.
William K Hallman, an experimental psychologist and a professor at the Department of Human Ecology at Rutgers University, said people do not put every decision through a risk-benefit filter and instead rely on cognitive shortcuts called heuristics to help in their daily lives.
But sometimes those shortcuts can be based on flawed assumptions or missing information. Because germs are out of sight, the belief is there is no harm in picking up fallen food from the floor and eating it.
People also do not recognise the symptoms of food-borne illnesses and tend to blame them on the last thing they ate, so they do not connect how their earlier actions might have made them sick. So, if food falls on the floor, it should only be discarded.