If you’ve ever accidentally dropped a piece of food on the floor and swiftly retrieved it because you did it within ‘the three second rule’, scientists believe that you might be onto something.

Researchers from Manchester Metropolitan University (MMU) discovered that the old age ‘three second rule’ when it comes to food dropped on the floor momentarily is safe – but mostly with salty, fatty processed foods.

During the study, researchers tested five different food items (cooked pasta, ham, biscuits, dried fruit and jam) to find out how long it take them to pick up bacteria (if any) three, five and 10 seconds after being dropped on the floor.

Although processed foods, which are high in fat, salt and sugar, have little nutritional value, they fared best during the bacteria tests.

Researchers discovered that processed ham, bread and jam posed less risk, as all of these food items had little or no bacteria growth when retrieved off the floor.

“Ham is a processed meat preserved with salt and nitrates which prevents the growth of most bacteria,” explains MMU technical officer Kathy Lees.

“The bread and jam showed no bacterial growth after time on the floor, which can be linked to the high sugar content of the jam which makes it unlikely to support microbial growth.”

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Biscuits were also deemed relatively harmless after being dropped on the floor.

“No specific organisms were detected on the biscuit, which has a low water activity level and low adhesion ability,” adds Lees.

In contrast, dropped dried fruit and cooked pasta carried the highest risk after three seconds, as researchers found signs of Pseudomonas - a bacteria that can cause septicaemia, soft tissue and urinary tract infections (UTIs).

Dried fruits were contaminated with Klebsiella after being discarded on the floor for more than five seconds, another potentially harmful germ that can cause UTIs.

Cleaning company Vileda who worked with the MMU during this study, also warned of the potential germs in our kitchen mops.

“Pseudomonas can often be present on mops and each time a floor is cleaned the bacteria is being spread increasing the chance of contamination,” says Lindsay Taylor from Vileda.

“Five mums took part in the study and admitted dropping dummies and fruit almost daily and letting their children have them.

“Mop heads need to be replaced regularly – every three months ideally – yet often people leave this until closer to a year. Ideally, floors should be mopped once a day yet a third of Brits only mop once a week.”