A college professor and her students at Connecticut College, in New London, CT, have put the “5-second rule” to the test in a real world environment to see how the long-standing “rule” stood up.
The “5-second rule” is a bit of conventional wisdom/old wives tale that says a piece of food that has fallen onto the floor is fine to eat if you retrieve it within 5-seconds of dropping it. The rule was actually proven in 2003 at the University of Illinois when a curious researcher coated the floor with E. coli and dropped gummy bears and cookies onto it to see how much bcteria they picked up.
The Connecticut team wanted to test the rule in a non-lab environment (how many people smear their floors with E. coli?) and took their samples of apple slices and Skittles, chosen because they wanted a “wet” food and a “dry” food, to the college’s highly trafficked main cafeteria. The items were dropped in intervals of 5 seconds to 5 minutes before being tested. It took about 1 minute for the apple slices to develop bacteria and 5 minutes for the Skittles, so the researchers concluded that the standard should be 30 seconds, with a notation that dry and/or porous foods may last for up to 1 minute and still be safe to eat.
All of this is good to know when you drop a couple pieces of popcorn at home and scoop them up again, but negative test results aren’t enough to make me want to eat a piece of food dropped on the floor of a public cafeteria no matter how long it is considered to be “safe to eat.”