Occurrence of hydrogen sulfide in wine and in fermentation: influence of yeast strain and supplementation of yeast available nitrogen

Hydrogen sulfide (H2S) is a powerful aroma compound largely produced by yeast during fermentation. Its occurrence in wines and other fermented beverages has been associated with off-odors described as rotten egg and/or sewage. While the formation of hydrogen sulfide (H2S) during fermentation has been extensively studied, it is the final H2S content of wine that is actually linked to potential off-odors. Nevertheless, factors determining final H2S content of wine have received little attention, and it is commonly assumed that high H2S-forming fermentations will result in high final concentrations of H2S. However, a clear relationship has never been established. In this report, we investigated the contribution of yeast strain and nitrogen addition to H2S formation during fermentation and its consequent occurrence the resulting wines. Five commercial Saccharomyces cerevisiae wine yeast strains were used to ferment a Chardonnay juice containing 110 mg/l of YAN (yeast assimilable nitrogen), supplemented with di-ammonium phosphate (DAP) to increase YAN concentration to moderate (260 mg/l) and high (410 mg/l) levels. In contrast to the widely reported decrease in H2S production in response to DAP addition, a non-linear relationship was found such that moderate DAP supplementation resulted in a remarkable increase in H2S formation by each of the five wine yeasts. H2S content of the finished wine was affected by yeast strain, YAN, and fermentation vigor. However, we did not observe a correlation between concentration of H2S in the finished wines and H2S produced during fermentation, with low-forming fermentations often having relatively high final H2S and vice versa. Management of H2S in wine through nitrogen supplementation requires knowledge of initial YAN and yeast H2S characteristics.