It’s the excuse that may have saved you from having to throw out Maltesers that rolled to the floor, but is it just one of those playground folk tales with no basis in science?
Cathy Moir, a food microbiologist and food safety specialist at the CSIRO, wrote in the Sydney Morning Herald to shed some light on the five second rule.
According to a peer-reviewed study, four food types were tested (watermelon, bread, bread and butter, and gummy sweets) with four different surfaces (stainless steel, ceramic tile, wood and carpet) that were contaminated with bacteria.
The study found:
- It’s true that the longer contact time the more contamination can occur, but time is not necessarily of the essence as microorganisms from one surface can instantaneously contaminate another.
- Higher moisture foods (such as the watermelon) allowed transfer of more microorganisms compared to other foods (such as the gummy sweets).
- The weakest microbial transfer occurred when food was dropped on to carpet compared to stainless steel, in particular.
“The majority of the microorganisms in a normal home are likely to be harmless to human health,” wrote Cathy.
So, it seems that there isn’t much truth to the rule – but we’ll probably use it again to save food from being victims of our own clumsiness.