We may have heard of the five-second rule when applied to dropping food on the ground. Basically, you have five seconds to pick it up before it gets swamped with all the bad germs on your floor. Ironically, nobody knows where this rule came from. However, new research has a different view of dropping food altogether.

Before we look at this in more detail, let’s look at some history. The great Mongol ruler, Genghis Khan (1162-1227), told his army that food was safe to eat even if it had been left on the ground for five hours. Note the ‘five’ in there, not sure if there is any connection here.

However, in 2014, researchers at Aston University in the UK brought that down, somewhat, to a few seconds. They believed that food picked up after a few seconds, after it was dropped, is “less likely to contain bacteria than if it is left for longer periods of time”.

A telephone survey of 1,000 Americans discovered that most of them agreed; 81 per cent of women and 64 per cent of men said they followed the five-second rule. William Hallman, a psychologist at Rutgers University, New Jersey, said: “We sort of joke about the five-second rule, but people act as if germs take some period of time to race to the item that fell on the floor.” We will now see that they don’t.

The five-second rule could be another urban myth. Or it could depend greatly on the surface where the food was dropped.  Returning to Rutgers University, it has been established that food begins to attract germs as soon as it hits the floor. A researcher, Donald Schaffner, who is a professor and specialist in food science, has discovered that the amount of moisture in the food, the type of surface and the length of time the food is left on the surface before being picked up can all play a part in determining the time before contamination begins (Appl. Environ. Micorbiol., 2016).

In the UK around a million people each year suffer a food-related illness. The National Health Service source states that many of these cases could have been avoided through basic hygiene

Schaffner tested four surfaces: stainless steel, ceramic tile, wood and carpet. He also tested four different foods: watermelon, bread, buttered bread and a gummy sweet.  He checked for contamination after less than one second, then after five seconds, after 30 and finally 300 seconds. The surfaces were dry, but had been contaminated with Enterobacter aerogenes, a non-pathogenic cousin of salmonella.

Subsequently, they calculated 128 possible combinations of surface, food and seconds that, when repeated 20 times each, yielded 2,560 measurements in total.

The findings were that the slice of watermelon was almost completely contaminated in five seconds; the gummy sweet, however, had the least amount of bacterial contamination (you would still not want to put it in your mouth though).  In total the four foods attracted contamination as follows:

■ Watermelon – after five seconds it was 97 per cent contaminated.

■ Bread – after five seconds it was 94 per cent contaminated.

■ Buttered bread – after five seconds it was 82 per cent contaminated.

■ Gummy sweet – after five seconds it was 62 per cent contaminated.

A microbiologist, Ronald Cutler, from Queen Mary, University of London, endorses that the five-second rule is not based on science. He, too, set out to prove this by testing food items. His trial involved dropping pieces of pizza, apple and buttered toast onto different surfaces. This time they were artificially coated with E. Coli, to emulate what would happen if food was dropped onto heavily contaminated surfaces. The study aimed to determine if the time the sample was left on the surface affected the degree of contamination picked up while there.

Dr Cutler analysed the food samples and found that they were all covered in germs, when compared with the control samples that had not been dropped (a bit obvious).

Once again the samples were dropped and picked up either immediately, or after five or 10 seconds, each sample was heavily contaminated. “The five-second rule has little effect on the amount of bacteria you would pick up from a heavily contaminated surface. No matter if it is at home on the carpet, the kitchen floor, or in the street, my advice is, if you drop it, chuck it.”

So, in conclusion, the idea that dirt is ‘good’ and hygiene is somehow ‘unnatural’ has been popularised in some media. For those who believe a little dirt never hurt anyone, there are some interesting statistics. In the UK around a million people each year suffer a food-related illness. (This does not break down into food dropped, or not dropped, on the floor, however).Of these million people, around 20,000 require hospital treatment and up to 500 may die as a result.

The National Health Service (NHS) source states that many of these cases could have been avoided through basic hygiene such as handwashing and preparing and cooking food correctly.

The main lesson to learn from all this research is if you drop food on the floor, it’s better to bin it than put it in your mouth.

kathrynmborg@yahoo.com

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