
 
 CTVNews.ca Staff 
 
 
 
 
 
 A newly released study may finally answer the question: Is the five-second rule valid? 
 
 According to research published in the journal of Applied and Environmental Microbiology, the answer is complicated. 
 
 Researchers from Rutgers University coated four different surfaces with Enterobacter aerogenes, a microorganism similar to Salmonella. 
 
 Next, they dropped watermelon, bread, bread with butter and gummy bears on each surface and left them there for different lengths of time. 
 
 The scientists found some bacteria transfer happens “instantaneously,” essentially debunking the idea that food is safe to eat if picked up in fewer than five seconds. 
 
 At the same time, they found contamination increased over time, lending some credence to the idea that food is safer to eat if picked up sooner. 
 
 They also found that some foods pick up bacteria faster than others. Watermelon had the highest rate, regardless of other variables, while gummy bears had the lowest. 
 
 Buttered and plain bread had similar transfer levels – meaning it doesn’t really matter whether your buttered toast falls butter up or butter down. 
 
 The researchers note that a 2005 episode of the TV show Mythbusters found no difference between food that had been left for two seconds or six seconds. 
 
 They write that their research “clearly showed that contact time does influence bacterial transfer.” 

 Turns out bacteria may transfer to candy that has fallen on the floor no matter how fast you pick it up. 
 
 Rutgers researchers have disproven the widely accepted notion that it’s okay to scoop up food and eat it within a “safe” five-second window. Donald Schaffner, professor and extension specialist in food science, found that moisture, type of surface and contact time all contribute to cross-contamination. In some instances, the transfer begins in less than one second. 
 
 Their findings appear online in the American Society for Microbiology’s journal, Applied and Environmental Microbiology. 
 
 “The popular notion of the ‘five-second rule’ is that food dropped on the floor, but picked up quickly, is safe to eat because bacteria need time to transfer,” Schaffner said, adding that while the pop culture “rule” has been featured by at least two TV programs, research in peer-reviewed journals is limited. 
 
 “We decided to look into this because the practice is so widespread. The topic might appear ‘light’ but we wanted our results backed by solid science,” said Schaffner, who conducted research with Robyn Miranda, a graduate student in his laboratory at the School of Environmental and Biological Sciences, Rutgers University-New Brunswick. 
 
 Photo: Shutterstock/Joe Belanger Researchers found carpet has very low bacteria transfer rates compared with those of tile and stainless steel. 
 
 The researchers tested four surfaces – stainless steel, ceramic tile, wood and carpet – and four different foods (watermelon, bread, bread and butter, and gummy candy). They also looked at four different contact times – less than one second, five, 30 and 300 seconds. They used two media – tryptic soy broth or peptone buffer – to grow Enterobacter aerogenes, a nonpathogenic “cousin” of Salmonella naturally occurring in the human digestive system. 
 
 Transfer scenarios were evaluated for each surface type, food type, contact time and bacterial prep; surfaces were inoculated with bacteria and allowed to completely dry before food samples were dropped and left to remain for specified periods. All totaled 128 scenarios were replicated 20 times each, yielding 2,560 measurements. Post-transfer surface and food samples were analyzed for contamination. 
 
 Not surprisingly, watermelon had the most contamination, gummy candy the least. “Transfer of bacteria from surfaces to food appears to be affected most by moisture,” Schaffner said. “Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.” 
 
 Perhaps unexpectedly, carpet has very low transfer rates compared with those of tile and stainless steel, whereas transfer from wood is more variable. “The topography of the surface and food seem to play an important role in bacterial transfer,” Schaffner said. 
 
 So while the researchers demonstrate that the five-second rule is “real” in the sense that longer contact time results in more bacterial transfer, it also shows other factors, including the nature of the food and the surface it falls on, are of equal or greater importance. 
 
 “The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food,” Schaffner said. “Bacteria can contaminate instantaneously.”
– The five-second rule is off by about five seconds in many cases, and not in the direction you hoped. That's what Rutgers researchers say in a new study debunking the classic kitchen rule, which declares it safe to eat food off the floor if scooped up in a flash. "We decided to look into this because the practice is so widespread," despite little research to back it up, Donald Schaffner tells Rutgers Today. After dropping watermelon, bread, bread with butter, and gummy candy on stainless steel, tile, wood, and carpeted surfaces crawling with salmonella-like bacteria about 2,500 times—and leaving the food untouched for one, five, 30, or 300 seconds—Schaffner and his team found that food could become contaminated "instantaneously," they report in Applied and Environmental Microbiology. The longer food sat on the surface, the more bacteria was usually transferred. But in certain cases, contamination occurred immediately, Schaffner says. That's because bacteria "move with the moisture, and the wetter the food, the higher the risk of transfer." Watermelon, for example, was contaminated most often, and gummy candy least often. To sum up, "the five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," Schaffner says. If you are going to eat food off the floor, carpet is your best bet, since it was least likely to transfer bacteria, say researchers—who point out a 2005 Mythbusters episode found no differences between food left on the floor for two or six seconds, per CTV News. (When it comes to pesticide residue, strawberries are the worst.)