FIVE THINGS ABOUT A POPULAR RULE

1 RULE IS BROKEN

If you drop food, the rule says you have a five-second window to pick it up and it will remain clean enough to eat. That’s so wrong, says a study published in the journal Applied and Environmental Microbiology.

2 BACTERIA ACT FAST

“Bacteria can contaminate instantaneously,” Donald Schaffner, a Rutgers University biologist and an author of the research, said. There are 31 known pathogens responsible for an estimated nine million cases of food-borne illness a year, according to the Centers for the Disease Control and Prevention.

3 BLAME JULIA CHILD

Though the origins of the five-second rule are murky, scientists point to Julia Child flubbing a potato pancake flip in an episode of The French Chef as a precursor. Her pancake doesn’t land on the floor, just on the stovetop, so she cooks it anyway. “Remember, you are alone in the kitchen and nobody can see you,” Child said. A 2003 University of Illinois survey indicated seven in 10 women and six in 10 men were familiar with the rule.

4 LETTING IT SLIP

Researchers dropped watermelon cubes, Haribo strawberry gummies, plain white bread and buttered bread on to various surfaces from a height of 12 centimetres. Those surfaces — carpet, ceramic tile, stainless steel and wood — were slathered with Enterobacter aerogenes, a bacteria similar in food-clinging ability to salmonella. Carpet transferred fewer bacteria than steel or tile. Wood showed a large variation.

5 MELON-CHOLY

“Bacteria don’t have legs, they move with the moisture,” Schaffner said. Wet food has the most risk of transfer. Watermelon soaked up the most bacteria, the Haribo candies the least. The scientists concluded that the fivesecond rule is a “significant oversimplification” for the chance of bacteria transfer. So, don’t drop that watermelon.