We’ve done it before and have seen kids do it: drop a piece of biscuit or potato chip on the floor, frantically pick it up, say “Wala pang 5 seconds!” and take a bite. Findings from a recent study show, however, that we may have to rethink this 5-second habit and simply quit eating food that’s been on the floor.
Published in the journal Applied and Environmental Microbiology, research from Rutgers University in the U.S. found that it could take less than a second for bacteria to transfer onto food that’s been dropped on the floor (like you, our eyes popped at this info). Contamination depended on how moist the food was, its surface type and how long it was in contact with the ground.
“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,” said author of the study Donald Schaffner, professor and extension specialist in food science.
“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.
The experiment was tested on four surfaces: carpet, wood, ceramic tile and stainless steel. Four different foods were dropped on them: watermelon, bread, bread and butter, and gummy candy. The food were either left on the surface for less than one second, five, 30 or 300 seconds. This is called contact time. As a contaminant, they used a naturally occurring bacteria (enterobacter aerogenes, if you want to know) in the human digestive system.
Taking all of this together, there was a total of 128 scenarios that the researchers conducted 20 times each. Then, they analyzed each food sample for contamination.
Results showed that watermelon had the most contamination and gummy candy the least. “Transfer of bacteria from surfaces to food appears to be affected most by moisture,” said Schaffner. “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.”
A carpeted surface showed to have very low transfer rates compared to tile and stainless steel. Wood, on the other hand, was sometimes a miss and sometimes a hit. “The topography of the surface and food seem to play an important role in bacterial transfer,” Schaffner said.
In a news release, the research found that the five-second rule has some validity in that longer contact times resulted in transfer of more bacteria. But no fallen food escaped contamination completely.
“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.” Meaning, you still shouldn’t eat that gummy bear that fell on the carpet, and especially not that watermelon that fell on the tiled-floor.
This doesn’t just apply to food either. Think of your baby dropping his pacifier on the floor. The pacifier is wet with his saliva, whch will most likely pick up a lot of bacteria.
Cleaning it with your hand isn’t going to do the pacifier, your baby and you any good either. “That is double-dipping--you are exposing yourself to bacteria and you are adding your own bacteria to that which contaminated the dropped item. No one is spared anything with this move,” Dr. Jorge Parada, medical director of the infection prevention and control program at Loyola University Health System, told Science Daily.
You can keep your baby’s pacifier clean by washing it with hot, soapy water after each use, advises the Canadian Pediatric Society. You can opt to sterilize the pacifier by putting it in boiling water for 5 minutes.