Concentrations of the Volatile Thiol 3-Mercaptohexanol in Sauvignon blanc Wines: No Correlation with Juice Precursors

The volatile thiol 3-mercaptohexanol (3MH) and its acetylated derivative 3-mercaptohexyl acetate (3MHA) are key contributors to the aroma of Sauvignon blanc. The concentrations of both thiols vary at least 20-fold in different wines, with differences among grape juices the major source of variation. Both thiols are produced by yeast from precursors present in the juice. At least four possible precursors have been proposed, although conversion rates for each precursor are low. The concentrations of three putative thiol precursors in 55 different Sauvignon blanc juices were compared to the concentrations of final thiols in wines fermented from each juice under controlled laboratory conditions. There were good correlations between the two thiols in each wine and among all three precursors in each juice. However, there was no correlation between the concentrations of the precursors in the juice and the final thiols in wine. Either these precursors are minor contributors to thiols in the final wine or there are other factors limiting conversion yields in different juices.