Honey is a natural sweetener, and bacteria loves to feast on sugar. But honey is remarkably resistant to spoilage. What's behind its ability to beat the bugs?

Most jarred delights have a limited shelf life – they're just one mucky spoon dip away from growing a luscious crop of mould or a thriving colony of bacteria. But there are certain foods with peculiar staying power, capable of staying edible for years.

Honey is one of these magical substances. In a sealed environment, while the golden stuff may crystallise, turning thick and chunky, it will not go off. This persistent ability to resist decay is down to honey's chemistry, and the way in which it is made.

When we say that food has spoiled, what we actually mean is that something else has got to it first, something microscopic. Bacteria, fungi, and moulds are present in at least low numbers in many foods, and a number of the procedures humans use to preserve food are designed to discourage these creatures consuming it.

Many of these microorganisms tend to prefer moist conditions, higher (but not too high) temperatures, a mellow pH, and plenty of oxygen around to use in their metabolism. Dehydrating meat or fruit, then, deprives them of water. Cooking food to a high heat and then moving it into the fridge for storage first kills off many bugs and puts a damper on the growth of any left behind. Suspending food in a pickling mixture wards off all but the most acid-loving creatures. Sealing something in a jar limits the oxygen they have access to.

Even food that's been put through a gauntlet of preservation procedures usually has a limited shelf life, as you might know if you have ever opened a jar of butterscotch sauce from the back of grandma's fridge, sealed in 1985, to find a thick carpet of fuzz within. (Don't ask me how I know.)

We are always fighting a losing battle against these organisms, and whether it's a whiff of vinegar that tells us the Lactobacillus has had its way with the orange juice, or black mould spots on the inside wall of the peanut butter jar, the signs of their presence are often unsubtle, and unavoidable.

But honey is an unusual case, and here is........

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