Is it really safe to pick up and eat food that falls to the floor if it hasn’t been on the floor for more than 5 Seconds? Fascinating question if you ask me. I remember back when we were kids if anyone in class accidentally dropped their lunch on the floor, we all assumed that the devil had taken a bite off it, and picking it up could kill you or leave you possessed ?. Well, its been years and we know better, or do we?
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I know you must have heard of the five second rule
somehow, and you have no clue how valid this well-adopted rule is. If you’re just hearing about it, the 5 second rule
is a ‘so-called’ food hygiene practice that food (or sometimes cutlery) dropped on the ground will not be significantly contaminated with bacteria if it is picked up immediately
(within five seconds) of being dropped. As funny as it may sound, many of us actually believed and applied this rule while growing up, and it gained so much popularity in households, restaurant kitchens, schools and almost anywhere people prepare or consume food.
Well, I got a little curious and did some digging. It turns out that the 5-second rule, where food is apparently ‘safe’ to eat if dropped on the floor and picked up before 5 seconds is false, and there are facts to prove it. While you may be tempted to pick up that last slice of pizza that fell to the floor, give it a little pat here and there and eat, science has shown that this is completely unsafe behavior.
By testing different foods on different surfaces to see how fast bacteria jumps on it, researchers found that bacteria can jump on our dropped snacks in under 1 second, which of course, is terrible news for big eaters everywhere, including myself.
Donald Schaffner, a member of the research team from Rutgers University said,
“The popular notion of the 5 second rule is that food dropped on the floor but picked up quickly, is safe to eat because bacteria need time to transfer. We decided to look into this because the practice is so widespread. The topic might appear ‘light,’ but we wanted our results backed by solid science.”
The research team decided to perform an experiment to investigate this, and they used four different types of surfaces we commonly interact with, which are stainless steel, ceramic tile, wood, and carpet. They also selected different foods to drop on them, such as watermelon, dry bread, buttered bread, and gummy candies. They grew Enterobacter aerogenes – a safe, non-pathogenic relative of Salmonella – in the lab, and covered their test surfaces in it.
The experiment was set, and each food sample was dropped on each bacteria-covered surface and left on the surfaces for different time intervals: 1 second, 5 seconds, 30 seconds, and 300 seconds. The team completed a total of 128 different trials, and the experiment was replicated 20 times. For certainty, up to 2,560 individual measurements were used to analyze the amount of contamination on each food item.
The team discovered that the biggest factor that influenced bacteria transfer was the amount of moisture present in the food, followed by the type of surface it falls on. While bacteria didn’t have to wait for 5 seconds to jump on the food, the longer food was left on the surface, the more bacteria jumped on the food.
“Transfer of bacteria from surfaces to food appears to be affected most by moisture. Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.”
The experiment exposed that longer contact times lead to higher levels of contamination, and picking up food that has stayed on the floor less than 5 seconds is still unsafe because 5 seconds is enough time for bacteria to transfer – especially if the food is wet or sticky like watermelon or candy, which had the highest levels of contamination across the tests.
“The 5-second rule is a significant over-simplification of what actually happens when bacteria transfer from a surface to food, Bacteria can contaminate instantaneously.”
The experiment also showed that surfaces covered with Carpet are actually the best to limit bacteria transfer because the structure minimizes the amount of contact it has with the food.
There have been other studies to test the validity of the 5 second rule. Still, Donald Schaffner and his team hope that their experiment and analysis of different types of foods and surfaces will help people to understand how the popular piece of advice is not something you want to base your hygiene practices around.
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