Formation and fate of sulfur compounds associated with negative attributes in wines

The occurrence of volatile sulfur compounds (VSCs) is influenced by factors including yeast selection and fermentation conditions; the nature and quantity of precursor compounds; the availability or absence of oxygen at different points of the winemaking process; and the availability and speciation of transition metal ions such as copper. As defence against the formation of undesirable VSCs, especially hydrogen sulfide, winemakers typically rely on monitoring must-nitrogen, additions of diammonium phosphate and copper, and choice of closure and its oxygen transfer rate. However, despite these commonly used management practices, post-bottling VSC release and sulfur-related off-flavours, can still be observed in some wines. Previously, a number of sulfur-containing precursors had been assessed for their role in releasing VSCs, and results indicate that many of these do not play a significant role in post-bottling VSC release. This suggests that other precursors are present which are yet to be identified.

This project will address these knowledge gaps relating to novel precursors and their degradation mechanisms.