You know those times when you’ve just promised a biscuit to a four-year old, and then you accidentally scatter them all over the kitchen floor, leaving the four-year old with a look of pure horror and dismay on her face?
What do you do?
Normally, I’d just scoop the pile of broken biscuits up and dump them straight in the bin, but this time The Five Second Rule was invoked.
What on earth is the Five Second Rule, I asked?
The Five Second Rule, I was told (quite confidently, I thought), states that if a piece of dropped food rests on the floor for less than five seconds, it’s still OK to eat.
This is scientific FACT, apparently.
Some discussion followed about this supposed rule probably being a load of old rubbish, but The Invoker remained adamant that everybody knows about the Five Second Rule, and that it was only a biscuit anyway.
Asking around on Twitter and at work confirmed that there are plenty of people out there who’ve heard of the rule, although the time boundaries seem to be flexible depending on location, and many people seemed to think that it was probably incorrect, but followed it anyway. This, obviously, makes no sense at all.
It sound like an urban myth, and in my experience, when things sound like urban myths, they normally are.
It seems common sense to expect that food that comes into contact with an unclean surface would pick up traces of whatever made the surface unclean in the first place, and there’s been plenty of research done to prove just this.
A paper published in the Journal of Applied Microbiology (links to .pdf) investigated the Five Second Rule in some detail, and concluded that salmonella could survive for up to four weeks on a dry, hard surface.
That’s a long time.
Even worse is the finding in the same paper that 99% of bacteria present on a floor tile were transferred onto a piece of bologna during five seconds of contact. That’s just normal, resting contact…they didn’t use the bologna like a mop, it was just put on the tile.
This isn’t the whole story, though.
There’s huge variation in bacteria transfer levels depending on the type of food and the type of surface it lands on. Generally speaking, a piece of bread landing on carpet is probably going to be OK, but a slice of ham landing on a kitchen floor isn’t. Anything in between is likely to show a sliding scale of contamination – it seems that the harder the surface and the wetter the food, the bigger the problem.
That’s all relative, though, because it doesn’t take much salmonella or e-coli to make you seriously ill and the transfer of some pathogens between surface and food happens immediately on contact. This makes perfect sense – as food impacts a surface, it is bound to pick things up easily and immediately. Try this for yourself by sprinkling some caster sugar on the floor and dropping a piece of ham on top of it. The sugar will stick to the ham, even if you pick it up immediately.
Now, imagine that those specks of sugar clinging to your ham are salmonella.
Still feel hungry?
Another factor to think about is the condition of the floor the food gets dropped on. I suspect that most kitchen floors aren’t quite as clean as their owners think they are – they’re high traffic areas susceptible to all kinds of lingering spills and stains…perfect breeding grounds for bacteria colonies. In contrast, outdoor surfaces are very likely to be cleaner than your kitchen – sun and rain see to that – so a biscuit dropped by a child onto a pavement should be fine. The types of pathogens present in a kitchen are more likely to be harmful than those found outside.
Think chicken blood dripping onto a kitchen floor.
I’m definitely not in favour of paranoia here – exposure to all kinds of nasties is necessary to build and maintain a healthy immune system, and the desirability of the dropped food item and their relative need to it it now are powerful factors
This isn’t about being a clean freak or wrapping your kids in cotton wool….just don’t eat ham off the kitchen floor.
And that muffin up there in the photo? It took about ten minutes to take the shot, and after I’d done, and bearing in mind everything I’ve just written, I decided to throw it away.
What do you think? Do you eat food that’s fallen on the floor?