Volatile sulfur compounds - a double-edged sword in wine

Hydrogen sulfide (H2S) is a well-known contaminant found in some wines that have so-called reductive off-odors. H2S, described as ‘rotten egg-like aroma’, brings the biggest trouble to wine maker. H2S is produced by the sulfate reduction sequence (SRS) pathway in S. cerevisiae during alcoholic fermentation.Very low levels of H2S can be detected due to its low odor threshold. It can be masking the fruity character of wine below sensory threshold, so trace amounts can have a serious effect on final wine quality.


There are several factors effect H2S production, such as deficiency of yeast assimilable nitrogen, insufficiency of pantothenic acid or pyridoxine.The deficiency of sulfur containing amino acids can trigger yeast to synthesize H2S from inorganic sulfur compounds.


Compounds derived from H2S


Mercaptanes (R-S-H)

Garlic, burnt rubber, rotten cabbage


Mercaptaneproduces a garlic, burnt rubber, cooked cabbagein wine. Thosecompounds are produced by the interaction of H2S with other wine components such as ethanol during wine fermentation or aging.


Disulfides (R-S-S-R)

Burnt rubber, garlic, cabbage, onion-like


Disulfides are formed from oxidation of sulfide or mercaptan precursors and very difficult to remove from wine,it can be reverted back to mercaptans with the addition of SO2.

Table1. Sulfur compounds for reduction odors

Sulfur compounds

Perception thresholds(ug/l)


Hydrogen sulfide


Rotten eggs



Rotten cabbage, burnt rubber



Onion, garlic, rubber

Dimethyl sulfide


Canned corn, asparagus

Dimethyl disulfide


Asparagus, garlic, rubber

Dimethyl disulfide


Vegetables, onion

Ethyl disulfide




Positive sulfur compounds

Fruity varietal Thiols

Box tree, passion fruit, grapefruit


Varietal thiols(4-mercapto-4-methylpentan-2-one (4MMP), 3-mercaptohexyl acetate (3MHA), and 3-mercaptohexan-1-ol (3MH)) have a positive impact on wine aroma and flavor. These volatile thiols are common in Sauvignon Blanc, but also have been found in other grape varieties such as Riesling, Cabernet Sauvignon, Merlot, and Semillon.

Table 2. Fruity thiols

Volatile thiols

Perceptionthreshold (ng/L)


Range in wines (ng/L)




Box tree, passion fruit, black current





Grapefruit, passion fruit





Passion fruit, box tree, guava



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Published by Fang Fang
Senior R & D Engineer
Angel Distilled spirits and Biofuels Division

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wine-off-flavor varietal-thiols mercaptanes