Food Safety: The Five Second Rule
Every once in a while a scientist/SF writer needs to get down to Earth. The other day a couple of Kenyon biology students stopped by my office to propose a term project in food safety. They plan to test an apparently well-known maxim known as the five second rule. This rule (well known, apparently, to everyone but me) says that if a piece of food is dropped on the floor, it’s safe to eat so long as you pick it up within five seconds.
Although I could not find much published in Science or Nature, several researchers do claim to have put this pressing question to the test. Paul Dawson at Clemson University said his students tested it and found that the rule absolutely doesn’t work–the fallen food is full of picked-up microbes. However, I smelled a rat (no pun) since I saw no raw data.
Then I found Dawson’s article from Journal of Applied Microbiology, “Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five-second rule.” There’s a mouthful all right. The data there are really more about survival time of pathogens on floors (measured in hours or days–a sobering thought in itself) but it does show that, be it five seconds or thirty, your slice of white bread is going to pick up plenty of hitchhikers to the microbial galaxy of your human body.
A high school student, Jillian Clarke, doing summer research at the University of Illinois at Urbana-Champaign, found different results. She found that the university floors at Illinois were too clean to pick up any microbes. (Take that, Clemson.) She also found interesting social observations, such as that “Cookies and candy are much more likely to be picked up and eaten than cauliflower or broccoli.”
Would you eat food picked up off the floor? In your home? Camping in the woods? If there were no more left?