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I have read that honey never spoils. Is this claim true? If so, what is it about honey that can cause it to remain edible for thousands of years?

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wiki says 'Most microorganisms do not grow in honey because of its low water activity of 0.6.' citing this book –  ratchet freak Dec 14 '11 at 0:28

2 Answers 2

up vote 22 down vote accepted

It is common knowledge that sugar will help microorganism growth (that's why, for instance, when you rehydrate freeze-dried yeast you add a pinch of sugar to help it restart its activity).

Too much sugar (or any other solute, really), however, is not good for microbial growth.

One parameter that is usually taken into account is the water activity.

Quoting Wikipedia:

[Water activity] is defined as the vapor pressure of a liquid divided by that of pure water at the same temperature; therefore, pure distilled water has a water activity of exactly one.
As the temperature increases, aw typically increases, except in some products with crystalline salt or sugar.
Higher aw substances tend to support more microorganisms. Bacteria usually require at least 0.91, and fungi at least 0.7.

Honey generally has a water activity between 0.5 and 0.6. (See this PDF), too low to support microbial growth.

Honey is in fact a well known antimicrobial, although the high sugar content is not the only factor contributing to this (low pH and presence of several antibacterial compounds play a role there).

To answer the question: does honey ever go bad?

From the US National Honey Board website

Honey stored in sealed containers can remain stable for decades and even centuries! However, honey is susceptible to physical and chemical changes during storage; it tends to darken and lose its aroma and flavor or crystallize. These are temperature-dependent processes, making the shelf life of honey difficult to define. For practical purposes, a shelf life of two years is often stated. Properly processed, packaged and stored honey retains its quality for a long time. If in doubt, throw it out, and purchase a new jar of honey!

So, essentially, if you stored it properly you will not have any issue.

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While I think your points are indisputable, can you answer the question directly? I mean: a sterilised can of beans should never go bad, for just as good reasons, but they do, because the can corrodes, for example... Can you, given your answer, assure us that honey is always safe to eat? –  Sklivvz Dec 14 '11 at 8:26
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I'm not talking about a sterilized can of honey, but about an open one... simply honey is not a good place for microorganisms to live. Anyway, I'll try and expand the answer tonight. –  nico Dec 14 '11 at 11:08
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agreed. So if I pick up a jar of honey, can I always eat it without fear of getting a disease? –  Sklivvz Dec 14 '11 at 11:47
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@Sklivvz unless to much moisture gets into the honey diluting it and raising the water activity –  ratchet freak Dec 14 '11 at 13:30
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@Sklivvz: sure, but those are quite specific and rare cases of contamination I would say. In fact I did not say that it does NEVER go bad ;). I couldn't find a proper ref for it, but apparently they found still good honey in the Pyramids... (I don't doubt they did, but the evidence on the fact that they tasted it and it was good is extremely anecdotal) –  nico Dec 15 '11 at 6:32

Honey can go bad

Osmophilic organisms are microorganisms adapted to environments with high osmotic pressures, such as high sugar concentrations.

[...]

Osmophile yeasts are important because they cause spoilage in the sugar and sweet goods industry, with products such as fruit juices, fruit juice concentrates, liquid sugars (such as golden syrup), honey and in some cases marzipan.

(Wikipedia)

Honey can be fermented into mead by adding water and yeast.

Mead is a honey-based fermented beverage that has been produced and enjoyed since before the dawn of recorded history.

Honey can contain spores of botulinum:

C. botulinum spores in honey used to sweeten infants milk or water, when ingested, geminate in the infants intestinal tract, colonize it and produce toxin in vivo.

So in short, assuming that honey does not go bad is completely wrong.

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Would you really call "mead" a honey which went BAD? ;) I know many who would disagree. –  Suma Dec 16 '11 at 2:52
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@Suma: In this case, "going bad" doesn't mean it's not useful; it's just not useful as honey anymore. To someone who's expecting grapes, wine doesn't fit the criteria (besides, not everyone likes wine), and similarly if one expects honey, and gets mead, then they may also be disappointed (besides, not everyone likes mead). –  Randolf Richardson Dec 16 '11 at 4:04
    
I would argue that mead doesn't really count, since it stops really being honey once you dilute it –  Richard Tingle Jun 30 at 14:34

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