Watch this before you pick up that fallen grape.
It’s inevitable: Everyone drops food at some point (more often than we’d like to admit). We’d like to say it’s fine as long as you pick it up ASAP (five-second rule!), but scientists say, “Nope.”
One 2016 study actually set out to see if this five-second rule had any validity to it. The researchers meticulously recorded the amount of bacteria present on a variety of foods (including watermelon, bread, and even gummy worms) after letting them sit on such surfaces as tile, carpet, wood, and stainless steel.
Sure, the foods picked up more bacteria the longer they rested on the floor, so the five-second rule may prevent giving your food fewer germs. But the researchers specifically note that some transfer of bacteria happens “instantaneously,” or under one second.
Does following the five-second rule really matter? Another study from 2007 specifically tested the presence of Salmonella typhimurium on food that had been dropped on wood, tile, and carpet. This pathogen was found to survive for up to four weeks on the floor and still be able to transfer to food. In other words, even if you think your floor is more-or-less clean, those cherry tomatoes that scattered across the kitchen floor could be a ticket to a foodborne illness. (If it helps, here’s a trick to slicing tomatoes so they won’t spill in the first place!)
However, the five-second rule does not simply apply to the floor. It’s not uncommon to rest your apple on your office desk or set some bread directly on the kitchen counter if you’re going to take your PB&J out the door with you. Sterile surfaces like dishes are always the safest bet, unless you know the surface is, in fact, clean enough to eat from.
Dawson P, Han I, Cox M, Black C, Simmons L. Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five-second rule. J Appl Microbiol 2007;102(4):945-53.
Miranda RC, Schaffner DW. Longer contact times increase cross-contamination of Enterobacter aerogenes from surfaces to food. Appl Environ Microbiol 2016;82:6490-6.