Sunday, October 25, 2020

The Five Second Rule


Someone mentioned the 5 Second Rule the other day about food which fell on the floor.  It started me thinking about its origins and validity.  As a community service, here is a post on it. 



The five-second rule, sometimes also the ten-second rule, is a food hygiene myth that states that there is a defined window where it is permissible to pick up food (or sometimes cutlery) after it has been dropped and thus exposed to contamination. Some may believe this assertion, whereas most people employ the rule as an amusing social fiction that allows them to eat a dropped piece of food, despite the potential reservations of their peers. 
- Wikipedia

A simple rule stating that food dropped on the ground is still perfectly edible if it is picked up in five seconds. Ingeniously created by guys for the sole purpose of reducing wasted food and allowing a person that second chance they needed to enjoy their food. 
- Urban Dictionary 


Is there any truth to the 5 Second Rule? 

I would imagine that there are a number of variables to be taken into account beyond just the time spent on the floor, including the nature of the floor and the nature of the food. Can you imagine picking up and eating something one dropped on the floor of the roadside rest stop toilets on the way to Canberra (assuming one took food in, to start with), or eating again a peanut butter sandwich that fell spread down. 

A look at the truth or otherwise of the rule later. 


According to the Oxford English Dictionary, the first mention in print of some sort of rule came from the 1995 novel Wanted: Rowing Coach, which referenced a “twenty-second rule.” A few years later, in the 2001 animated film Osmosis Jones, a character follows the “ten-second rule” and eats a germ-infested egg, which sends his body’s immune system into disarray. 

There are instances before then of the practice of using dropped food, even though it did not yet have a name. In a 1963 episode of Julia Child’s cooking show The French Chef, Childs attempted to flip a potato pancake in a pan, missed, and the pancake landed on the stovetop. Childs simply looked straight into the camera and said, “You just scoop it back into the pan. Remember, you are alone in the kitchen and nobody can see you.” It is considered that Child’s action helped popularise the practice in the minds of the public. See the failed flip at: 


There have been various studies done and reports published on the accuracy or otherwise of the rule: 

A study at the University of Illinois at Urbana-Champaign was conducted Jillian Clarke and supervised by Meredith Agle. Floors in the lab, hall, dormitory, and cafeteria were swabbed and found to have relatively low bacteria counts, probably because the floors were dry. Most pathogens like salmonella, listeria, or E. coli can't survive without moisture. Cookies and gummi bears were placed on both rough and smooth sterile tiles covered with measured amounts of E. coli. According to Agle: "We did see a transfer of germs before five seconds, we were dealing with a large number of cells." 

A more thorough study in 2006 using salmonella on wood, tiles, and nylon carpet, found that the bacteria were able to thrive under dry conditions even after twenty-eight days. Tested after eight hours of exposure, the bacteria was still able to contaminate bread and bologna in under five seconds. But a minute-long contact increased contamination about tenfold (especially tile and carpet surfaces). 


The five-second rule was featured in an episode of the Discovery Channel series MythBusters, which discovered that there was no significant difference in the number of bacteria collected. The aspects that affect the contamination process is the moisture, surface geometry and the location. Here is the full written report on the Mythbusters examination: 

The Five Second Rule 

Myth: if you pick up a piece of food that has fallen on the floor before five seconds is up, no bacteria will get on it 

See also: NYTimes article on Clemson University Five-Second Rule study, "The Five-Second Rule Explored, or How Dirty Is That Bologna?" 

Test 1: MythBusters HQ samples 

Jamie and Adam used contact plates to test various locations in the MythBusters shop for bacteria. Each contact plate was placed on the floor for five seconds and labelled with the location. They incubated the contact plates for 24 hours and then counted the number of bacteria on them. 

They got different results from locations that were adjacent to each other, so they decided that it would be important to eliminate location as a variable in the test. 

Mini-myth: Toilet seat is the cleanest spot in the house 

While they were collecting samples around the shop, Adam also placed a contact plate on the toilet seat for comparison. It did have less bacteria colonies than the other samples, though it seems that the other samples were all collected from the floor. 

Test 2: Evenly contaminated surface 

In order to eliminate location as a variable they created some evenly contaminated surfaces with beef broth. They dropped wet food (pastrami) and dry food (cracker) onto the surface for two and six seconds. They also did a control sample for comparison. 

The wet pastrami picked up more bacteria than the dry crackers, but there wasn't a discernible difference between the two-second and six-second samples. They would need to do more testing to single out time as a factor in the test. 

Jamie: "I don't think the results were all that conclusive." 

Mini-myth: Dog mouths are cleaner than human mouths 

Adam and Lulu the Dog both licked a contact plate. After incubating the samples, the dog's sample had less bacteria colonies than Adam's. 

Adam: "I don't eat my own poo" 

According to LiveScience: "Despite a habit of licking things no human would dare, Fido's mouth is often touted as scientifically more sterile. Truth is, oral bacteria are so species-specific that one can't be considered cleaner than the other, just different." 

Test 3: Contact plates on evenly contaminated surface 

They decide to eliminate food as a variable in the test and instead just apply the contact plates to the beef brothed surface for two seconds and six seconds. Both showed tremendous amounts of bacteria with no real difference based on time. 

They found that the amount of bacteria that was picked up depended on the moisture of food, the surface geometry of food, and the location that it was dropped on, but there was no correlation to the amount of time it was dropped. 

Myth busted. 


As against this, germ expert Professor Anthony Hilton, from Aston University, has said that although retrieving dropped food can never be completely without risk, there is little to be concerned about if the food is only there momentarily. “Obviously, food covered in visible dirt shouldn't be eaten, but as long as it's not obviously contaminated, the science shows that food is unlikely to have picked up harmful bacteria from a few seconds spent on an indoor floor That is not to say that germs can't transfer from the floor to the food. Our research has shown that the nature of the floor surface, the type of food dropped on the floor and the length of time it spends on the floor can all have an impact on the number that can transfer.” 

It comes as a survey of 2,000 people found 79 per cent admitted to eating food that had fallen on the floor. 



So there you are, you pays your money and takes your choice. 


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