Some scientists are calling a timeout on the five-second rule. The popular notion that says it’s OK to eat food that is picked up from the floor within five seconds is substantially oversimplified, Rutgers University researchers have found.

The bottom line: Bacteria will transfer to food no matter how quickly it gets scooped up. Exactly how much cross-contamination occurs is a function of the type of food, the kind of floor surface and the amount of time involved, researchers said. The findings appeared recently in the journal Applied and Environmental Microbiology.

The researchers tested four surfaces — wood, carpet, tile and stainless steel — and four foods — gummy candy, bread, watermelon and bread with butter. The foods were dropped repeatedly on the surfaces for intervals ranging from one second to five minutes.

After obtaining more than twenty-five hundred measurements, the researchers determined that food type greatly affects contamination: The watermelon had the most germs, while the gummy candy had the least. That, researchers said, suggests that moister foods attract more bacteria after being dropped.

The type of surface also made a difference: Carpet was, by far, the least likely to transmit contamination compared with stainless steel and tile. The contamination rate for food dropped onto a wood surface varied.

The researchers found one truth in the five-second rule: The longer food sits on a dirty surface, the more bacteria it collects. But they said other factors, such as the type of food and the surface it lands on, affect contamination much more.

Overall, the research suggests that time may have run out for the old five-second rule.