Spot on Science: 5 Second Rule

Winter is certainly the season for stuffing our faces with tasty treats. From Thanksgiving to New Year’s I know for me it’s a marathon of meals. But have you ever overloaded your plate though and lost a cookie to the floor? [slow motion cookie falling] Noooo!

Five second rule! You can eat it if it didn’t touch the floor for more than five seconds, right? Maybe not. Some scientists at Rutgers University took the five second rule to the lab to see if it really is okay to eat food that has fallen on the floor. They dropped watermelon, buttered bread, plain bread and gummy candies on different floor types like tile, wood and carpet. Then they tested the food for bacteria. Turns out contamination for some of the food was instant. Bacteria transferred the most to the watermelon and the least to the gummy candy. According to the researchers this is because bacteria don’t have legs to just hop on the food, they need moisture to help them hitch a ride. So the wetter the fallen food the more bacteria it’s going to pick up.

Surprisingly they found bacteria transferred more easily from tile floors than from carpeted ones. And while they did note the longer the food is on the ground the dirtier it gets, five seconds is still plenty enough time to make you think twice about biting into that fallen cookie. 

Instructional Links

Website Article: Kids Health, 5-Second Rule

Magazine Article: Science News, Time to Retire the 5-second Rule, October 29, 2016

May Need Password

Game: Partnership for Food Safety Education, The Food Detectives Fight Bac!

PDFs: K-State Research and Extension, Kids a Cookin', Food Safety Tips

Experiment: Science Bob: Experiments, Growing Bacteria for Science Fairs

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