Hydrogen sulphide (H₂S) is a volatile sulphur compound associated with the smell of rotten eggs. In winemaking, it can form during fermentation when yeast produces sulphur compounds, sometimes in response to nutrient stress or other fermentation conditions. At low levels it may be noticeable as a reduction-related fault; at higher levels it can mask fruit and make a wine unpleasant.
Some cases may diminish with careful aeration, but persistent hydrogen sulphide should be assessed by the winemaker. Copper treatments are sometimes used professionally under controlled, legally permitted conditions; they are not a recommendation for casual home treatment. More complex sulphur faults may not respond to simple aeration.
Example: a newly opened wine with a clear rotten-egg odour may contain hydrogen sulphide. If the smell remains after brief exposure to air, it may indicate a persistent fault.
Related terms: reduction is a broad term for wine aromas associated with limited oxygen and sulphur compounds; mercaptans are other sulphur compounds that can cause different off-odours.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
