Methanol in distilling: fact and myth

Where methanol comes from

Pectin is the substance that helps hold plant cells together, and fruit is rich in it - especially the skins. Pectin carries small methyl groups; when it is broken down, by enzymes in the fruit itself or added ones, those groups are released as methanol. Yeast plays almost no part: fermenting sugar produces ethanol, not methanol.

That makes the raw material the deciding factor:

Commercial spirits reflect the same pattern. In the European Union, vodka may contain no more than 10 g of methanol per hectolitre of pure alcohol, while spirits made from fruit pomace may contain up to 1,500 g - a hundred and fifty times more, and perfectly legal.

What distilling does - and doesn't do

Distillation doesn't make methanol, and a still can't conjure it from a sugar wash. What distillation does is carry the methanol in a wash over into the spirit along with the ethanol.

Methanol behaves much like ethanol in a still. Studies of fruit spirits find it in every fraction - heads, hearts and tails - and often peaking in the early hearts rather than in the very first drops. So the cuts influence it only modestly: they matter enormously for flavour, but they can't turn a high-methanol wash into a low-methanol spirit. Keeping methanol low starts with the fruit and the fermentation.

The myths

"Methanol boils off at 65 °C, so you can drive it off first."

Pure methanol boils at about 65 °C, but a still boils a mixture. At sea level, no ethanol–water vapour is cooler than about 78 °C, and methanol leaves the still spread through the run. A reading of 65 °C at the head means the still is warming up. See why a temperature chart can't tell you when to cut.

"All the methanol is in the foreshots."

The foreshots do carry some of it, along with other volatile compounds you don't want, and discarding them is sound practice. But they don't contain all of it.

"Home distilling makes people go blind."

The poisoning outbreaks reported around the world are overwhelmingly caused by drinks mixed with industrial methanol - usually to cut costs, sometimes by mistake. A sugar or grain wash distilled with ordinary care does not produce dangerous levels of methanol. The risk is real, but it lies in adulteration, contamination and carelessness with fruit, not in distillation itself.

"If it tastes all right, it's safe."

Methanol cannot be reliably tasted or smelled in a drink. Neither the nose nor the thermometer can confirm what is in a jar of spirit.

Keeping methanol low with fruit

• Use sound, clean fruit, and remove stems and leaves.
• Ferment promptly. The longer crushed fruit sits before and during fermentation, the more pectin is broken down.
• Be wary of pectic enzymes. Winemakers use them to break down fruit and clear juice, but they can release extra methanol from the pectin. Many fruit distillers avoid them, or choose preparations made for spirits.
• Separate the liquid from the solids before distilling, rather than heating skins and pulp in the boiler.
• Cut with care, discarding the foreshots generously - while remembering that the cuts are not the main control.

Warning signs of methanol poisoning

Methanol itself is not the main problem: the body converts it into formaldehyde and formic acid, which damage the optic nerve and other organs. That conversion takes time, so symptoms are often delayed by 12 to 24 hours or more - longer if ethanol was drunk at the same time. A few tens of millilitres of pure methanol can be fatal, and smaller amounts can cause blindness.

Signs include headache, dizziness, nausea and vomiting, abdominal pain, rapid or difficult breathing, and disturbed vision - blurring, or a "snowfield" effect.

Sources and further reading

1. German Federal Institute for Risk Assessment (BfR): Questions and answers on methanol in spirits, including EU limits under Regulation (EU) 2019/787. bfr.bund.de
2. Médecins Sans Frontières: Methanol poisoning - fact sheet. methanolpoisoning.msf.org
3. Stoica, F. et al. (2020). Volatile compounds in different fractions of fruits distillate obtained by traditional distillation. Scientific Bulletin, Series F: Biotechnologies, XXIV(2). PDF

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