You drop some food on the floor, but you know you’ve got five seconds to pick it up and eat it before germs get to it, right?
After all, it’s the ‘safe-food’ window, and it’s even been featured in
two TV shows.
But it’s yet another urban myth—or probably is, depending on the surface on which you’ve dropped the food and the food you’ve dropped.
In fact, some foods start attracting germs the moment they hit the floor, a researcher from Rutgers University in New Jersey has established. Donald Schaffner, a professor and specialist in food science, has discovered that the amount of moisture in the food, the type of surface and length of time the food is left on the surface before being picked up can all play a part in determining the time before contamination starts.1
Schaffner tested four surfaces—stainless steel, ceramic tile, wood and carpet—and four different foods—watermelon, bread, buttered bread and a gummy sweet—and checked for contamination after less than a second, then after five, 30 and finally 300 seconds. The surfaces were dry, but had been contaminated with Enterobacter aerogenes, a non-pathogenic ‘cousin’ of Salmonella.
In all, they calculated 128 possible combinations of surface, food and seconds that, when repeated 20 times each, yielded 2,560 measurements in total. They found that the slice of watermelon was almost completely contaminated at five seconds, while the gummy sweet had the least amount of bacterial contamination... but would you really want to stick that in your mouth?
Floored food: a history
The great Mongol ruler Genghis Khan (1162–1227) told his army that food was safe to eat even if it had been left on the ground for five hours.
But in 2014, researchers at Aston University in the UK brought that down a tad—to a few seconds, in fact. They reckoned that food picked up after a few seconds after being dropped is “less likely to contain bacteria than if it is left for longer periods of time”, which sort of makes sense.
A telephone survey of 1,000 Americans discovered that most of them agreed: 81 per cent of women and 64 per cent of men said they followed the five-second rule.
William Hallman, a psychologist at Rutgers, said: “We sort of joke about the five-second rule, but people act as if germs take some period of time to race to the item that fell on the floor.”
As we now know, they don’t.