Thiol levels in Chenin blanc wines


The aim of this study was to determine the volatile thiol levels in commercial South African Chenin blanc wines. Volatile thiols were previously measured as part of a bigger study investigating the effect of skin contact on Chenin blanc wine quality and style. However, the current study is the first study world-wide specifically investigating the presence and importance of volatile thiols in Chenin blanc wine.

Project layout:
 Sixty five commercial dry South African Chenin blanc wines were analysed for volatile thiol concentrations. The two thiols analysed were 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA). The method utilised was a UPLC-MS/MS. Wines of three different ages were analysed: one, two and three years old.

Results:
  • 3MH and 3MHA were both found in concentrations above their aroma thresholds indicating that these two components contribute significantly to Chenin blanc aroma.
  • The wines displayed large differences in concentrations of these two volatile thiols.
  • The older the wine – the lower the 3MHA concentration (the most unstable volatile thiol).
  • 3MH levels correspond to levels reported in Sauvignon blanc.
  • The highest 3MH concentration measured in this study was 2929 ng/l, which is higher than the maximum measured in a 2010 study measuring the thiol levels in cultivars other than S. blanc.
  • 3MHA seems to be lower than levels reported for Sauvignon blanc.
  • 3MHA concentration was negatively influenced by wood contact. Barrel maturation introduces small amounts of oxygen into wines. Barrel matured wines are usually aged a bit longer before release into the market.

Significance of the study:
Volatile thiols are present in large concentrations in Chenin blanc and make a significant contribution to final wine aroma and quality. As a result viticultural and winemaking practices can be adapted to enhance their expression in wines, if it is the style desired. Chenin blanc is not as “neutral” as the world often perceives it to be.


Reference:
Christine Wilson, M.Sc. thesis, Department of Viticulture and Oenology, Stellenbosch University

Image source: Wikipedia

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