Remember the five second rule? If you pick up food dropped on the floor within five seconds, it’s still safe to eat? Researchers at Rutgers have made it a lot more complicated, by studying the influence of different floor surfaces on different foods. A Rutgers news release reports that with the right (or wrong) combination of floor surface and food, contamination begins in less than one second. The researchers tested four surfaces – stainless steel, ceramic tile, wood and carpet – and four different foods (watermelon, bread, bread and butter, and gummy candy). They also looked at four different contact times – less than one second, five, 30 and 300 seconds. They used two media – tryptic soy broth or peptone buffer – to growEnterobacter aerogenes, a nonpathogenic “cousin” of Salmonellanaturally occurring in the human digestive system. In all, 128 scenarios were replicated 20 times each, yielding 2,560 measurements. Wow!
Not surprisingly, because moisture speeds the transfer of bacteria, watermelon had the most contamination, gummy candy the least. Surprisingly, carpet has very low transfer rates compared with those of tile and stainless steel, whereas transfer from wood is more variable. The bottom line: if you drop a lot of food, try eating gummy bears while standing on a carpet.