The chemical secrets that help keep honey fresh for so long
29 comments
·July 4, 2025cypherpunks01
This article is missing what I think is a pretty important PSA on the topic of bacteria in honey:
Honey commonly contains small amounts of the anaerobic bacteria Clostridium botulinum, which causes botulism.
This is why you should not feed honey to infants, because their immune systems cannot safely handle any amount of it yet. Even though the levels apparently are small enough for the rest of humans to consume worry-free.
bjelkeman-again
The story misses that lactic acid bacteria are fairly common in honey and seem to be out competing other bacteria and have anti microbial effects.
__mharrison__
Recently went through first aid training and the instructor claimed putting honey on wounds would help them heal faster.
(Sample size 1) I tried it on myself and a wound that was stubborn about healing was better very quickly.
cryptonector
Really high sugar concentrations will pop the cells of any simple organisms.
kragen
No, low. High sugar concentrations mean low water activity, which osmotically pumps water out of cells, not into them, so they shrivel rather than popping.
Terr_
I like to imagine it as humans stranded in a strange land where all the geography is dry cake. And only dry cake.
xattt
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kragen
This story can be summarized as "Low water activity and low pH keep honey fresh permanently." The other 14 paragraphs are just filler. Moreover, even that summary is factually incorrect; low water activity and low pH don't come close to explaining honey's astounding shelf life, which amounts to centuries in many cases.
https://en.wikipedia.org/wiki/Honey#Preservation in particular mentions gluconic acid and hydrogen peroxide produced by the bees' glucose oxidase, and https://en.wikipedia.org/wiki/Honey#Medical_use_and_research also mentions its content of methylglyoxal, which damages DNA and cross-links proteins somewhat like formaldehyde, thus killing microorganisms; mãnuka honey is required to contain at least 85mg/kg of methylglyoxal, according to https://en.wikipedia.org/wiki/M%C4%81nuka_honey. I suspect that there is a great deal more research on the topic.
It's disappointing to see such a low-quality article on the BBC website; I generally regard the BBC as a reliable source.
vlovich123
Are you sure this isn’t just the Gell-Mann effect? It sounds like you’re probably better informed about this than the typical person and might be expecting a lot more detail than a newspaper would be endeavoring to try to convey.
jagged-chisel
I think the point is that the article is conveying too much of the wrong kind of details.
kragen
vlovich123 may be correct that I am giving the BBC too much credit in general. But I don't think I'm especially well-informed; I'd never heard of methylglyoxal before looking this up in Wikipedia.
I agree that its focus is somewhat wrong. I don't think that the backgrounder on the importance of food preservation is completely without value. It's just that it's already fairly well known that food rots and why.
My larger objection, though, is that there are important, well-established reasons for honey to be far less perishable than other substances of similar water activity and pH, and the article does not mention them even briefly. I think it's fine to have lots of the wrong kind of details, but it's not fine to omit the right ones.
jfengel
I don't see why anything other than low water and pH are necessary. Stories about ultra long lasting honey come from the desert, which will dessicate it further.
(The stories about pyramid honey always imply that it's fresh and liquid. It's not. It's dried out and usually completely crystallized.)
There may be other effects on top of that, but if you made a sucrose solution thick enough it too will last forever.
kragen
If you can get an aqueous solution of solids to completely crystallize (and sucrose does like to crystallize), it won't support microorganisms, but if it doesn't crystallize, it will have a critical "deliquescence relative humidity". When the relative humidity of the air is above the DRH†, the solution absorbs water from the air rather than giving up water to the air, and if there are crystals in it, they tend to shrink instead of growing.
Different solutes have different DRHs, but there are many of them whose affinity for water is so strong that their DRH is so low that under normal circumstances they never completely dry out. Some of them are commonly used as desiccants, such as lye, calcium chloride, and magnesium chloride. In general, mixing solutes tends to impede crystallization, so more heterogeneous mixtures like honey tend to have lower DRH than more homogeneous mixtures like pure sucrose.
(This is an engineering reason to add something like lemon juice when you make simple syrup: the citrate hydrolyzes some of the sucrose into glucose and fructose, greatly impeding crystallization and greatly improving your chances of having a pourable syrup when you want to use it next month.)
Under many circumstances, honey will eventually absorb enough water from the air by this mechanism to permit the growth of yeasts and bacteria. But it takes a remarkably long time.
______
† The DRH does vary with temperature, but in most cases only slightly over the human-survivable range, so you can say "CaCl₂ has a DRH of about 40%" and be correct enough for many purposes.
gerdesj
"which amounts to centuries in many cases."
Pretty sure I read about honey found in a Pharaoh's tomb - that's millennia, not centuries.
Quick search:
https://www.smithsonianmag.com/science-nature/the-science-be...
kragen
I edited "millennia" into "centuries" in my comment above because the Wikipedia article claimed those claims didn't pan out:
> (However, no edible honey has been found in Egyptian tombs; all such cases have been proven to be other substances or only chemical traces.[29])
...but the citation is from 01975.
The Smithsonian page is a great link! It mentions that the pH of honey is 3–4.5 (another crucial fact omitted from the BBC article) and mentions the peroxide, but not the methylglyoxal.
The Smithsonian article contains this link:
> Modern archeologists, excavating ancient Egyptian tombs, have often found something unexpected amongst the tombs’ artifacts: pots of honey, thousands of years old, and yet still preserved
which goes to a Google Books page I can't see (perhaps because I'm in Argentina) of a book from 02006 that is apparently about beekeeping, not archaeology, called "Letters from the Hive", published by Random House Children's Books.
The copy of the book that I've been able to get does talk extensively about the uses of honey in ancient Egypt, but, unless I missed it, doesn't mention pots of honey being found in tombs at all.
Even if so, it's unclear whether the book would have evidence posterior to Wikipedia's 01975 citation; it isn't the kind of book that cites its sources.
gerdesj
I'm so sorry but I can't help myself: 01975 is the dialling code for somewhere in Aberdeenshire!
WP: "(However, no edible honey has been found in Egyptian tombs; all such cases have been proven to be other substances or only chemical traces.[29])"
[29] is https://gwern.net/doc/history/1975-leek.pdf - this does not look like a peer reviewed paper. They do look to be reputable and they refute some rubbish documented cases of ancient honey but not all of them.
I'm going to call out the WP article as being factually wanting on that point.
giantg2
The real secret is osmotic pressure.
comrade1234
Osmotic pressure? Ok I'll read the article.
mhb
Similarly, chocolate.
dylan604
You can take honey that has crystalized and set it in sunlight to "melt" back into the gooey goodness, but you can't do that to chocolate that has that white powdery stuff on it.
mhb
Right. Once the undesirable crystals in chocolate have formed it has to be re-tempered to get the desirable ones to dominate. But it hasn't spoiled.
quibono
I've often wondered about this - is sunlight really all that's needed?
liquidpele
Heat is needed, not sunlight.
bdamm
You can zap it in the microwave for 10-15 seconds, but I always feel terribly guilty for some inexplicable reason.
tekla
Bloom isn't spoilage.
mayormaura
[dead]
Same principle (low water activity) is how Nutella keeps fresh for so long without refrigeration: its water activity is even lower than honey.
Here’s the definition of water activity from FDA:https://www.fda.gov/inspections-compliance-enforcement-and-c...