Yeast, glutathione synthesis

Because grape must contain little organic sulfur, in the form of S-amino acids and glutathione, yeast assimilates sulfate, and sulfite when added, for the synthesis of organic sulfur compounds. Sulfur metabolism is important in winemaking since, depending on the yeast strain and nutrient composition, it is the source of mostly unpleasant compounds, including H2S and mercaptans (Rauhut 1993). 

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