Researchers at Rutgers University in New Jersey have once again disproven the widely accepted notion that it is OK to quickly scoop up food fallen on the floor and eat it safely. This is often referred to as the 5-second rule. If a food only stays on the floor a few seconds, that timeframe is not long enough for bacteria to adhere to the food and be transferred to you when it is eaten. Not so.
The researchers tested four surfaces – stainless steel, ceramic tile, wood and carpet with four different foods – watermelon, bread, bread and butter, and gummy candy. They also looked at four different contact times – less than a second, 5, 30 and 300 seconds. They took over 2,500 measurements to insure the accuracy of their tests.
What did they find out? Time does matter. The longer the food was in contact with any surface the more bacteria were transferred to the food. So an M&M that your child dropped yesterday on the kitchen floor should not be eaten when he spies it the next day. Though in most cases using the 5-second rule will probably not cause illness, the researchers did show that some of the bacteria transfer was instantaneous with contact.
The more moisture a food has the greater the bacteria transfer. In this experiment watermelon collected the most bacteria and gummy candies the least. This is an important point if your child’s moist pacifier falls on the floor. One unexpected finding was that carpeted surfaces had the lowest transfer rate for bacteria as compared to stainless steel and tile. Wood was variable.
Bottom line: The 5-second rule is an oversimplification of whether food is safe to eat. If food falls on the floor, throw it away.
