Wine Fault

Mercaptans

Additional

Mercaptans are volatile sulfur compounds producing garlic, onion, cabbage, or skunk-like aromas when hydrogen sulfide is not remediated during winemaking. They are more persistent than H₂S and harder to remove once formed.

Also known as: Thiols fault, Ethyl mercaptan, Cabbage smell

Typical severity: High

Cause

Ethyl mercaptan and related thiols formed from H₂S conversion or yeast sulfur metabolism under reductive conditions.

How it occurs

Untreated H₂S, copper mistreatment, or prolonged reductive aging allows mercaptans to develop. They can form in bottle if precursor conditions exist.

Prevention

Early H₂S detection, proper copper fining protocols, adequate aeration at the right stage, and avoiding over-reductive cellaring.

Descriptors created

Descriptors reduced

Commonly confused with

Common wine styles

Common grape varieties

Common regions

Related winemaking techniques

Serving implications

Beginner explanation

Mercaptans smell like cooked cabbage or rubber — worse than a brief struck-match note and unlikely to blow off.

FAQ

Can mercaptans be removed?
Limited options exist in tank (copper, aeration). In bottle, mercaptans are essentially permanent at fault levels.
How do mercaptans relate to H₂S?
H₂S often precedes mercaptans — treating H₂S early prevents evolution into harder-to-remove thiols.

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See also

Fault identification guidance reflects common wine education practice and may vary by wine style, age, and context.