Forget the "five-second rule," says a new study that debunks the notion that food dropped on the floor is safe to eat as long as you pick it up quickly. Rutgers University research shows that bacteria are quicker than you are, and can transfer to food in less than a second.

Professor Donald Schaffner found that moisture, the type of surface, and contact time all contribute to cross-contamination. In some instances, the transfer begins in less than one second.

"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 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.

Schaffner and graduate student Robyn Miranda tested four surfaces — stainless steel, ceramic tile, wood and carpet — and four different foods (watermelon, bread, bread and butter, and gummy candy).

They also tested four different contact times — less than one second, five, 30 and 300 seconds — using Enterobacter aerogenes, a nonpathogenic cousin of Salmonella.

Watermelon was the most easily contaminated and gummy candy was 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."

Surprisingly, carpet has very low transfer rates compared with those of tile and stainless steel. The ability to transfer germs from wood surfaces is variable. "The topography of the surface and food seem to play an important role in bacterial transfer," Schaffner said.

"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."

Their study was published in the American Society for Microbiology's journal, Applied and Environmental Microbiology.

Where did the "five-second rule" originate? No one knows for sure. It didn't start, although the story is passed around, with Julia Child when she dropped a piece of meat on the floor during her cooking show "The French Chef." But it's a wide-spread quote.

A 2003 study found that 70 percent of women and 56 percent of men recognized the "rule."

Some bacteria are particularly dangerous, such as some strains of E. coli, and only a few cells can infect a person.