You’ve probably heard about the five-second rule: the idea that if you drop food on the floor, you have five seconds to pick it up and eat it before it gets too “contaminated” to safely ingest. But does this “rule” actually have any scientific basis? Here, researchers tested how long it took for bacteria to be transferred to food (specifically, bologna and bread) resting on different surfaces (tile, wood, and carpet). They found that 5 seconds of contact was enough to transfer 99% of bacteria from the tile to the bologna, but a much smaller number of bacteria were transferred when the food was dropped on carpet. So there you have it: if you drop your food on the carpet, feel free to pick it up, brush off the lint, and enjoy. But if you drop it on tile, you might want to go ahead and grab another slice of bologna.
Three experiments were conducted to determine the survival and transfer of Salmonella Typhimurium from wood, tile or carpet to bologna (sausage) and bread.
METHODS AND RESULTS:
Experiment 1. After 28 days, 1.5 to 2.5 log(10) CFU cm(-2) remained on tile from and the more concentrated media facilitated the survival of S. Typhimurium compared with the more dilute solutions. Experiments 2 and 3. The bacterial transfer rate to food decreased as the bacterial residence time on the surface increased from 2, 4, 8 to 24 h with transfers of 6.5, 4.8, 4.6 and 3.9 log CFU ml(-1) in the rinse solutions, respectively. Over 99% of bacterial cells were transferred from the tile to the bologna after 5 s of bologna exposure to tile. Transfer from carpet to bologna was very low (<0.5%) when compared with the transfer from wood and tile (5-68%).
(i) Salmonella Typhimurium can survive for up to 4 weeks on dry surfaces in high-enough populations to be transferred to foods and (ii) S. Typhimurium can be transferred to the foods tested almost immediately on contact.
SIGNIFICANCE AND IMPACT OF THE STUDY:
This study demonstrated 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.”