Viticultural and oenological influences on volatile thiols

Dr Carien Coetzee
Basic Wine

This table serves as a general indication of the effects of various viticultural and winemaking techniques on the precursors and their aromatic volatile thiols in the must and wine.

A few things need to be considered when consulting this table:

• Researchers sometimes find contradicting results due to the inherent composition of the must and wine. Therefore, tendencies reported in this table might not be applicable to every must/wine situation, however it identifies techniques that could potentially have an effect.
• A higher concentration of precursors does not necessarily result in a higher concentration of volatile thiols in the resulting wine.
• Often interactive effects are observed. For instance, one yeast strain might result in higher concentrations of thiols in a specific grape must, while showing no difference in juice from another vineyard. The significance of the increase and decrease shown in this table varies. Sometimes the process had powerful effects, multiplying the concentration of thiols in the wine. For other processes investigated, smaller increases were observed and might not necessarily have a sensorial effect.
• It is important to note that scientific studies report on “statistically significant” increases, which could sometimes translate to small increases only. Recent Winetech funded research results indicate that rather large differences in thiol concentrations need to exist for a person to detect an increase sensorially.
• In some cases, only one of the thiols were measured or the factor studied only had an effect on one or two of the main thiols. The indications in the table are thus not always applicable to all three of the main thiols.
• The summary is a broad generalisation of the results found in the studies and there are always exceptions.

For more information or the full scientific research papers, contact Carien directly.