University of Illinois - High-school student Jillian Clarke investigated the scientific validity of the "5-second rule" during her apprenticeship in Hans Blaschek's University of Illinois lab this summer. You know the rule: If food falls to the floor and it's in contact with the floor for fewer than 5 seconds, it's safe to pick it up and eat it.
According to Clarke, a senior at the Chicago High School for Agricultural Sciences, the 5-second rule dates back to the time of Genghis Khan, who first determined how long it was safe for food to remain on a floor when dropped there. Khan had slightly lower standards, however; he specified 12 hours, more or less.
Among Clarke's findings:
--Seventy percent of women and 56 percent of men are familiar with the 5-second rule, and most use it to make decisions about tasty treats that slip through their fingers.
--University floors are remarkably clean from a microbial standpoint.
--Women are more likely than men to eat food that's been on the floor.
--Cookies and candy are much more likely to be picked up and eaten than cauliflower or broccoli.
--And, if you drop your food on a floor that does contain microorganisms, the food can be contaminated in 5 seconds or less.
A participant in the College of Agricultural, Consumer and Environmental Sciences' summer Research Apprentice Program, Clarke began by swabbing 1-inch squares of floors in a variety of locations on the U of I campus, including floors in high-traffic areas. "We were shocked," said Meredith Agle, a Ph.D. candidate in Blaschek's food microbiology labs, who helped Clarke with the experiment. "We didn't even find a countable number of bacteria on the floor. We thought we might have made a mistake, so we tried again with the same result. "Then we went back to look for spore-forming organisms, such as Bacillus, something that would resist dry conditions, but we couldn't find any spores either," Agle said.