Hydrogen Sulfide Prevention

Hydrogen sulfide (H2S) produces a distinctive "rotten egg" smell in wine, cider, beer and other fermented beverages.

H2S is one of the most commonly occurring and persistent problems in wine production. Industry experts estimate that 90 per cent of wine producers experience problems with H2S or other volatile sulfur compounds resulting from chemical interactions with H2S. The result is that an estimated 20 per cent of contaminated wine will require some type of remediation and in rare situations some wine may even be discarded. H2S is of great concern to winemakers because it dramatically affects the sensory quality of the end product, sometimes to the point of rendering the wine unsaleable.

H2S is formed as a natural byproduct of yeast metabolism when sulfates and sulfites are used by yeast to synthesize the sulfur-containing amino acids cysteine and methionine.

Normally, most H2S, along with carbon dioxide, vaporizes from the wine. However, the minute sensory threshold of H2S means that even the smallest amount can result in a significant sensory masking problem for the winemaker. Moreover, H2S is quite reactive, and other volatile sulfur compounds may further develop from chemical modification of H2S.

Despite best efforts to address the problem, remediation of H2S (e.g., treatment with copper sulfate) also typically taints and compromises the resulting wine product. Addressing one contaminant by adding another has other complicating and undesirable ramifications.

One example of the economic cost of H2S and remediation was the 2007 rejection of 4,000 cases of a New Zealand pinot noir by its German buyer after the discovery that the wine’s copper content exceeded European standards for the metal (copper had been used to counteract the H2S). Reports indicate that the New Zealand wine company subsequently decided to sell the affected wine at various supermarkets under a different brand name, and at prices marked down by more than half. H2S can exact a significant revenue cost to commercial wineries.