Wine Fault

Hydrogen Sulfide

Chemical

Hydrogen sulfide produces rotten-egg or sewer-like aromas when yeast ferment under stress or in oxygen-starved conditions. Low levels may dissipate; persistent H₂S indicates a serious fermentation fault.

Also known as: H2S, H₂S, Rotten egg smell, Sulfide fault

Typical severity: High

Cause

Yeast reducing sulfur-containing amino acids under nutrient deficiency, high solids, or reductive ferment conditions.

How it occurs

Stressed ferments — especially with weak yeast nutrition, high Brix, or excessive lees — generate H₂S during primary fermentation. It can bind into heavier mercaptans if not addressed early.

Prevention

Adequate YAN and nutrient additions, yeast strain selection, early H₂S monitoring, copper fining when caught in tank, and controlled aeration.

Descriptors created

Descriptors reduced

Commonly confused with

Common wine styles

Common grape varieties

Common regions

Related winemaking techniques

Serving implications

Beginner explanation

Rotten egg on the nose at fermentation usually means nutrient stress — in bottle it signals a serious fault unlikely to improve.

FAQ

Can copper fix hydrogen sulfide?
Copper fining in tank can bind H₂S before bottling. Once bottled at fault levels, options are essentially none.
Does H₂S become mercaptans?
Yes — untreated H₂S can evolve into harder-to-remove mercaptans and disulfides, worsening the fault.

Related ontology entities

See also

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