Monday, May 14, 2007

Cutting Edge Science With Bologna Proves The Efficacy of "The 5 Second Rule"

We have all done it. You are cooking something, maybe a steak, or something else that you can’t bear to part with, it slips off of the spatula and splat……hits the ground. You are confronted with 3 options: Be a civilized human and throw it away, be a Cro-Magnon and put it back on the plate and reserve it for yourself, or be a Neanderthal and pick it up and serve it to one of your unwitting guests (for the record, my nickname when I was on the wresting team in high school was Cro-Mag. They were almost right.) I am usually thinking “As long as I pick it up within five seconds, I can serve it to Kristen and she will never be the wiser." But ask yourself; do you really believe in the five second rule? Do you honestly believe that if the food in question is picked up within 5 seconds, somehow, the transfer of bacteria to food will be substantially less than if it were left on the ground for longer than 5 seconds? I for one, have always followed the five second rule, though I didn't really believe that it made a difference how long the food was left on the ground. Cutting edge science had now actually demonstrated that abiding by the five second rule can substantially diminish the risk of contracting a food borne illness. I came across an article in The New York Times written by Harold McGee, the author of the must-read food science book On Food and Cooking, where he addresses this question. Harold McGee’s article is based on a scientific research paper published in The Journal of Applied Microbiology. To make a long story short, adhering to the five second rule can substantially minimize the transfer of bacteria to that tasty morsel that you drop on the floor. The authors of the study apply a controlled amount of Salmonella to tile, wood, and carpet and quantify the transfer of Salmonella to bologna and sliced bread. The interpretation of the data is not strait forward though, it is dependent on how long the bacteria has been present on the surface of question.
To make a long story short, as the bacterial residence time on a wood surface approaches 24 hours, ten times more salmonella was transferred from wood to bologna when they were left in contact for 30 sec. or 60 sec. as compared to 5 sec. The results are similar to bologna dropped on carpet except that the 10 fold difference in contamination level is observed as little as 8 hours after inoculating the carpet with Salmonella. Eight hours after inoculation of ceramic tile with Salmonella, the transfer of bacteria to white bread (not that any of us would own white bread….) is approximately five fold less if in contact for 5 sec. as compared to 30-60 sec. After a residence time of 8 hours on tile, salmonella transfer to bologna after 30 sec. and 60 sec. is increased 5 to 10 fold respectively, as compared to 5 sec.
The bottom line is that the five second rule is now backed by hard scientific evidence demonstrating that adherence to this rule can minimize bacterial contamination two fold. Now my guilty conscience will not drive me to call Kristen and casually ask how she is feeling the day after serving her dropped food.

Dawson, P., I. Han, M. Cox, C. Black, and L. Simmons. 2007. Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five second rule. J. Appl. Micro. 102: 945-953.

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