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I just read this question on Quora about distilling during pre-industrial age, which reminded me about multiple discussions I have heard or read during the years about whether the fermentation process used to produce alcoholic (ethanol) beverages produces methanol.

As far as I understand it, yeast, sugar and water results in ethanol. A similar process to get methanol would require you to (destructively) distil wood (methanol is also called something like wood alcohol in many languages) and since you usually don't include wood when making beverages, there should be no methanol in the result.

Furthermore, non-hard liquor like beer and wine do never have a "methanol problem" although, especially wine(-like liquids) often is used as a base when producing hard liquor. Besides, when binge drinking, you typically drink similar amounts of pure ethanol independently of if you drink wine or hard liquor.

My guess is that a reasonably controlled fermentation process of grapes/barley/fruits/grain/etc doesn't result in any noticeable amounts of methanol and if you distil it and keep everything and mix it good it is as safe as drink as home made wine and beer. The problem with methanol, my guess again, is that people in the "moonshine business" sometimes dilute the result with methanol because it is cheaper.

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    $\begingroup$ By quick search you can easily realize non-distilled alkoholic beverages like wine (red more than white) do contain minor amounts of methanol and there are law limits for it, much lower than level causing problems. For spirits, aside of illegal methanol mixing, there can be problem with amateur distillation, if early low boiling T fraction is consumed, as it is significantly enriched by methanol. $\endgroup$
    – Poutnik
    Apr 30, 2022 at 13:03
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    $\begingroup$ You're right that fermentation of pure sugar should not produce methanol, but crude fruits (like grapes) contain a lot of pectin, and hydrolysis of the methyl esters in pectin yields methanol in the fermentation. $\endgroup$
    – Andrew
    Apr 30, 2022 at 14:23
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    $\begingroup$ BTW, the large ethanol:methanol ration makes the small amount of methanol less dangerous, since liver enzymes that convert methanol to far more toxic formaldehyde are engaged by the process of metabolizing ethanol. Clinically, this can be used to treat methanol poisoning - pubmed.ncbi.nlm.nih.gov/7083094 . Do not try this at home. $\endgroup$ May 1, 2022 at 2:18
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    $\begingroup$ I am really surprised that this question hasn't received any answers at all! $\endgroup$
    – d-b
    Nov 3, 2022 at 17:04
  • $\begingroup$ @d-b probably because Andrew and DrMoishe already summed it up perfectly, but see below for my attempt :P $\endgroup$
    – nonchip
    Apr 24, 2023 at 6:17

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tl;dr: No, but yeast, plants and water do.

Any Pectin you have in your source material will contribute to Methanol production, and distillation (when you're doing it wrong, especially the remixing bit) can easily increase the resulting concentration high enough to be damaging, while a "natural fermentation" would be too diluted.


As far as I understand it, yeast, sugar and water results in ethanol.

First things first, there are plenty yeasts that might do different things, but most "traditionally used ones" (including baking yeast!) would convert monosaccharides (fructose, glucose, galactose) into ethanol and CO2.

Also, they usually contain enzymes or get help by e.g. lactic acid bacteria in SCOBY fermentations (or the brewer has to do preprocessing steps to help that conversion along) that break down di- (lactose, sucrose) or polysaccharides (starch etc) into monosaccharides.

One of those enzymes contained in a lot of yeasts and plants happens to be "pectin methyl esterase", which converts Pectin (a "heteropolysaccharide", so "one of the things that can be broken down to simple sugar", and incidentally also "the stuff plants contain EVERYWHERE as a structural material"). As a side product, this will essentially always produce methanol.

Also there are some other (but rarer) ways to produce it, such as by various strains of various fermenting bacteria producing more or less of it depending on what they ferment.

A similar process to get methanol would require you to (destructively) distill wood

Thing is, this is a completely different process. Fermentation, the thing you (presumably) want to produce ethanol, will produce methanol in the "pectin eating step". Distilling wood is a dissimilar, alternative process to get high amounts of methanol quickly without the fermentation.

and since you usually don't include wood when making beverages

well you do though. grapes are "wood", grains are "wood", apples are a LOT of "wood", etc, given pectin content is all that matters for the yeasts, not "whether it looks/feels woody" ;)

Furthermore, non-hard liquor like beer and wine do never have a "methanol problem"

they do, almost all of them contain methanol, just usually so little you don't notice. additionally they contain a LOT more ethanol, which literally just dilutes the toxic effect of the methanol in your body.

the main issue is that when distilling, you're increasing the overall concentration so much, it becomes very nontrivial for your body very quickly, especially if you're keeping a lot of the early product.

Note that despite the popular misconception the post you linked to keeps spreading, a distillation will not produce outputs "in steps" ("methanol first, then ethanol, then water"), but it's all "smooth transitions". so the very first drop will contain the most methanol, and the very last drop will contain the most water, but it will also contain some trace of methanol still, as will anything in between (and as will the first drop already contain a trace of water).

So you're essentially dealing with a tradeoff between "the more of the early stuff i get, the more methanol i get" vs "the more of the early stuff i throw out, the more i'm wasting, and the more i might be throwing out flavors i want to keep".

My guess is that a reasonably controlled fermentation process of grapes/barley/fruits/grain/etc doesn't result in any noticeable amounts of methanol

that'll "just" give you multiple percentage points of poison usually, likely won't kill/blind you in that concentration and presuming you have a normal-sized stomach volume.

and if you distill it

Then you "distribute out" the compounds and increase overall concentration.

and keep everything and mix it good it is as safe as drink as home made wine and beer.

I mean it'll taste burnt and nothing as the original, but yeah if you literally distill everything and then remix it without taking anything out (well except for the burnt up particulates i guess), you have more or less what you started with yes.

Distillation doesn't make methanol, obviously, it only makes it easier to concentrate it on accident.

"moonshine business"

the main reason a lot of moonshiners used to poison themselves is actually just because it's a bit suspicious if you have a bunch of decent lab equipment in a forest and therefore they'd literally just taste test to figure out how much methanol there is (and if you do that all the time it adds up), or because they'd be cheap and literally just distill off the water and keep the methanol in because why not, you're doing an illegal thing anyway, might as well be negligent about it (mind you at the same time the government would literally poison random foodstuffs suspected of being used for moonshine!). I doubt they'd literally buy methanol to add it in though, i mean you're already fermenting and distilling here, why buy more alcohol, if you can just use straw or whatever to get more cheap bulk mass that then just happens to be mostly pectin and almost no sugar, so gets turned into a lot of methanol "on accident" that you then just don't bother to throw out if you're cheap like that.

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    $\begingroup$ You (humans) can't taste any difference between pure ethanol and pure methanol. $\endgroup$
    – d-b
    Apr 25, 2023 at 11:08
  • $\begingroup$ @d-b i rather won't try, so i'mma believe you, i've been told by moonshiners that they do it by taste, so i assume what they actually taste is other volatile compounds in the "heads", and just hope the ethanol follows the same curve, which then might explain why they went blind :P $\endgroup$
    – nonchip
    Apr 30, 2023 at 10:04

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