The five-second rule is the unofficial guideline for determining what food is safe to eat after falling onto the floor. But everything we thought about the popular theory looks set to change, with a new study confirming that the timeframe isn’t that accurate after all.

While there are a bounty of foods that should be scooped up within five seconds, there’s a long list that have up to half an hour before they need to be saved from the ground. Researchers at Aston University in Birmingham proved their theory by dropping a range of different foods on surfaces that include carpet, linoleum and tiles which contained 10 million bacteria.

The results determined that those foods classified as ‘rigid’ are able to sit on the floor for up to 30 minutes without falling victim to additional contamination over time. These are foods that include chocolate, toast, biscuits, sandwiches and chips. But foods that don’t fall into this category (the non-rigid) should still stick to the five-second tradition. These are lollies, pasta, hot chips, doughnuts and the like.

Not only is type of food that has fallen important, but also the type of floor surface. Carpet makes no difference when it comes to contamination over time, but food on a floor made from laminate or tile does. Put simply, the longer food sits on a hard floor, the more bugs the food will attract.

“People may not realise that dry foods, hard foods are really quite low-risk,” explains lead researcher Professor Anthony Hilton. “Not only do they not pick up much bacteria on impact with the floor, but they do not get any additional contamination over time

“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.”