Anyone who has children probably knows the 5-second rule: A piece of food falls on the floor. If it’s picked up within 5 seconds, it’s probably okay to eat - right?
Maybe not, according to Kansas State University food scientist Karen Blakeslee.
Blakeslee, who is the Rapid Response Coordinator for K-State Research and Extension, cited recent research at the University of Illinois that put the "rule" to the test. Jillian Clarke, a high school senior, did an internship there last summer and tested the 5-second rule.
"She swabbed several floors in various locations across campus, including high traffic areas, for general microbial load. To her and other researchers’ surprise, the floors were remarkably clean, Blakeslee said. "They retested the same areas and had the same results. They also tested for spore-forming bacteria that survive in dry conditions and did not find any spores."
Further tests were conducted using smooth and rough 2-inch tiles from the hardware store and a supply of gummy bears and fudge-striped cookies. These foods were chosen after a survey showed that people were more apt to pick up sweet foods than other foods, she said.
"Because candy and cookies are naturally low in microflora, they were considered good test candidates," Blakeslee added. "The tiles were sterilized and inoculated with E. coli. After inoculation, 25 grams of cookies or candy were placed on the tiles for 5 seconds. The food and tiles were examined, using environmental scanning electron microscopy." The results, she said, showed that the food picked up E. coli within 5 seconds. More E. coli was transferred to the gummy bears from smooth tiles than rough tiles.
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