The 5-Second Rule: Is it Fact or Fiction?
If you drop food on the floor, do you toss it in the trash? Or do you take advantage the “five-second rule” that says if you scoop it up off the floor within five seconds of dropping it you’re good to go?
“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,” says Donald Schaffner, co-author of a new study aimed to evaluate the degree to which the five-second rule actually works.
“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,” notes Schaffner.
The researchers used four different test surfaces. These included stainless steel, ceramic tile, wood and carpet.
Then, they tested what happened when they dropped watermelon, bread, bread and butter, or gummy candy on the surfaces. The test scenarios included one, five, 30 and 300 seconds of contact time with the surfaces.
Overall, they performed 128 different drops, repeating each one 20 times. Finally, the team analyzed the food samples for contamination.
Once the results were tallied, it turned out that the watermelon ended up with the most contamination. The gummy candy had the least.
This wasn’t a surprise to Schaffner who explains that bacteria moves with moisture.
“The wetter the food, the higher the risk of transfer,” he explains. “Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.”
When compared to tile and stainless steel, the lowest rate of transfer occurred on the carpet. The wood transfer was much more variable.
So while it’s true that food accumulates less bacteria during a five second period, the amount of bacterial transfer also depends on the surface it falls on.
“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.”
Rutgers researchers debunk ‘five-second rule’: Eating food off the floor isn’t safe. Press Release. Rutgers University via EurekAlert. Sept 2016.