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The Five-Second Rule: Fact or Fiction?

By Dan Flynn and Suzanna Schreck

Whether you abide by the five-second rule, seven-second rule or five hour rule you may want to consider new research completed by Clemson University scientist Paul Dawson. He and his students recently published a study (pdf) in the Applied Journal of Microbiology delving into the science behind the infamous five-second rule. Dawson's team analyzed the ability of bologna and bread to pick up the bacteria Salmonella Typhimurium from tile, wood, and carpet.  They discovered that the dangerous bacteria can last on dry surfaces for up to 4 weeks in high enough populations to be transferred to both bread and bologna immediately upon contact.  With bologna, 99 percent of bacterial cells were transferred from tile after 5 seconds of contact. Transfer from carpet to bologna was very low when compared with transfer from wood and tile.   "This study demonstrates the ability of bacteria to survive and cross-contaminate other foods even after long periods of time on dry surfaces, thus reinforcing the importance of sanitation on food contact to minimize the risk of foodborne illness," the authors state. Dawson is a food scientist at the food science and human nutrition department at Clemson University.  His work on the five-second rule was recently showcased in National Geographic magazine.  The article made a strong case for the "zero-second rule." His work focused on household surfaces like wood and tile. Many scientists agree that these surfaces are most likely to be contaminated with bacteria like Salmonella, but that outdoor surfaces are normally pretty clean. "It's OK to brush off the bagel that fell from the stroller onto the sidewalk and give it to your screaming child, for example, because the pavement is cleaner than the kitchen floor in terms of the types of germs that cause illnesses," said Dr. Harley Rotbart, a professor of microbiology and pediatric infectious diseases at the University of Colorado School of Medicine. "The kitchen floor, however, is probably a zero-second zone because the bacteria from uncooked meat and chicken juices are more hazardous than the 'soil' bacteria outside," said Rotbart.  Rotbart is the author of "Germ Proof Your Kids."
Researchers agree that most people will pick up food from any surface if they want it badly enough.

Full post as published by Food Safety News on July 24, 2010 (boomark / email).