Can I get methanol poisoning from home brew beer?

Can I Accidentally Make Methanol? A Homebrewer's Guide to a Common Fear

From time to time, I see potential brewers ask if they will accidentally make methanol (AKA 'wood alcohol') when foraying into beer production. It's a legitimate fear, fueled by horror stories of people going blind from "bad moonshine." This is because methanol is genuinely dangerous. It is toxic to the human body and can have some very nasty effects if someone is poisoned - ranging from blindness to, in the worst cases, death.

You may have arrived at this page because of the sad story coming out of South Africa during 2020 where a couple died after drinking homebrew. While there are limited facts on this tragic case, we can be confident that methanol from a standard beer homebrew was not the cause. Let's separate the myths from the science.

The Short Answer: No, You Won't Go Blind

First up, the answer to the question is that the ordinary beer home brewing process makes the alcohol called ethanol - not methanol. They have slightly different chemical formulas, and brewer's yeast (Saccharomyces cerevisiae) is a biological factory perfected over millennia to produce ethanol.

So you can't get methanol poisoning from your homebrew, no matter how much extra sugar you add. It's more likely that you will just get blind drunk or meet Darth Vader!!

The Science: Fermentation vs. Distillation

The confusion and fear surrounding methanol comes from a misunderstanding between two very different processes: brewing (fermentation) and distilling.

Fermentation is a biological process. Yeast consumes sugar and produces ethanol and carbon dioxide. While some trace amounts of methanol can be produced, especially in fruit-based fermentations containing pectin, the levels are negligible and far below anything that could cause harm. Commercial fruit juices often contain more methanol than a homebrewed beer.

Distillation is a physical process of separating liquids based on their boiling points. This is where the danger lies. Methanol has a lower boiling point (64.7°C) than ethanol (78.4°C). In a backyard still, when the fermented mash (the "wash") is heated, the methanol vaporizes first. This first part of the distillate, known as the "heads," is highly concentrated with methanol. Inexperienced distillers who fail to discard the heads can indeed create a lethal product. For this reason, home distillation is illegal in most countries. If you are homebrew brewing beer, there's no risk of making a killer brew. Distillation on the other hand... stay away from that unless you've been properly trained.

Methanol Poisoning & Treatment

For educational purposes, it's important to understand what methanol poisoning involves. Methanol toxicity is the result of consuming methanol. The horrific symptoms may include a decreased level of consciousness, poor coordination, vomiting, and abdominal pain. The famous effect of decreased vision or blindness may start as early as twelve hours after exposure.

The blindness is caused by the methanol being metabolized by the body into formic acid, which then has a debilitating and damaging effect on the eye's optic nerve. Fortunately, there is a cure. The sooner the antidote, fomepizole, is administered, the greater the likelihood of a good outcome. Other treatments include dialysis and sodium bicarbonate. This is not medical advice. If you suspect a consumption incident, seek medical assistance immediately.

What About That Old Bottle of Wine?

I saw a query from a gentleman who decided to drink a glass of wine after leaving the bottle open for 2 months. The wine was disgusting, burned his throat, and gave him a headache. He wondered if it had turned into methanol.

It's more than likely that the wine's ethanol had not converted to methanol. Instead, it was exposed to oxygen and Acetobacter, a common airborne bacterium. This bacterium consumes ethanol and produces acetic acid—turning his wine into a vile vinegar!

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↣ How long can homebrew beer be left in the primary fermenter?

Is there a risk of leaving beer in the primary fermenter too long?

As a general rule of thumb, one can leave the beer in the primary fermenter as long as one needs.

There is no set maximum time limit, though there are a couple of slight risks to keep in mind.

Many brewers simply follow the beer recipe or instructions on the malt kit and leave their wort to ferment for around a week to ten days. This usually allows enough time for the first stage of fermentation to have completed.

And technically that's OK, and it's time to bottle.

But the mystery and muscle of brewing beer are that there is a whole range of chemical processes happening in that wort you're fermenting.

Sure the yeast may have produced enough alcohol to make a good drop of beer but there are still a few things that happen.

The longer you leave your beer, the more chance the yeast has to get rid of smells and other leftovers from the fermentation process.

A great example of this is the presence of acetaldehyde in the wort. This chemical forms at the beginning of the fermentation process. It tastes like sour green apple and is not really conducive to a good brew. Giving your beer batch time to work through this will mean a better tasting beer.

Wort left for a long time is harder to carbonate when bottled, is this true?

It possibly could be, depends on your circumstances.

If the beer has been left in the fermenter over winter, for example, the yeast could have become quite dormant so the bottled beer will need to be warmed for the yeast to come 'back to life'.

A trick some brewers have found is that when it comes time to bottling a long-settled wort, give it a small stir up 2 days before you bottle. It causes the yeast to mix back into the beer (it will have settled at the bottom of the fermenter). If you move the fermenter into a warmer place, then your bottled beer with have a shorter carbonation time.

What's the best way to get rid of  'apple taste' from brewed beer?

Let the yeast take the time to convert it into ethanol (alcohol).

So leaving your beer for longer than the recommended instructions on the tin of the beer kit is pretty much a smart move. Frankly, given the benefit to the beer and thus the kit manufacturer's reputation, I do not know why they don't frame the time as a minimum.

That said, when I followed Te Aro's brewing instructions for their Obligatory ale, I made damn good beer.

Exceptions aside, the longer you condition your beer, the greater reduction in acetaldehyde that will occur and the beer your beer will take.

Stout beers have even more to work through so they can happily take longer in the primary.

Another benefit of leaving the beer in the primary for longer is that there is a greater chance that your beer will clear more sediment, thus giving you clear beer. 

Many-a-brewer likes to see their lager look like a lager - that classic light yellow / orange combo. Sure, some wheat beers can be a bit hazy.

At the end of the day this comes down to personal preference as the beer taste is not generally affected.

It's also important to consider the role temperature can play in brewing. If you want a short fermentation period but it's cold, then you may have to simply allow more time because the yeast slows down the alcohol production process when chilled. 

What about leaving beer in for extra long times like 3 - 6 months?

Many brewers have reported leaving batches for months and suffered no issues.

I'd reason though that the beer was stored in a cool place - a beer wort left in a hot environment is sure to fail as the yeast would probably get cooked.

The lid was probably screwed on very tightly as well and the beer must be kept out of the light. Put a sheet over it!

My mate Julian did a beer after 8 months once (a chilli one, go figure) - it tasted fine after bottling. 

There is an issue that can happen called 'autolysis'

This is when the yeast cells die, giving off some potentially 'off flavors'. These could be hydrolytic enzymes, lipids, and metal cations that can contribute to off flavor.

If you've made a healthy batch with a quality yeast, pitched at a good temperature and brewed in a stable environment, then the risks of autolysis are quite low. 

If you are quite concerned about this, you could counter by racking your beer to a secondary, thus removing the yeast cake from the equation.

It's important to note, the same process begins again when the beer is bottle conditioned - more sugar is added to the beer for the yeast to eat - this is because CO2 is the by-product of fermentation and is trapped in the beer.

Most beers strongly benefit from being bottle conditioned for three weeks before consumption and even then they usually start to become pretty drinkable at the 5 week mark.

If you have placed a lot of hops in your beer, remember that their effect reduces over time so once a well hopped beer has reached optimal drinking time, you may as well drink them!

Extra for experts: How to increase the alcohol level in homebrew - amylase can help with attenuation.

1 comment acetaldehyde, autolysis, ethanol, fermentation, temperature