Winemaking interventions to modulate glutathione status
The OIV has recently passed two resolutions allowing the addition of glutathione to must and wine. (See OIV-OENO 445 addition of glutathione to must.pdf and OIV-OENO 446 addition of glutathione to wine.pdf.) An Australian evaluation of its potential benefits and risks is necessary to make a case for its inclusion in the Australia New Zealand Food Standards Code, and for the industry to subsequently make informed decisions about its use.
The concentration of glutathione in wine can be enhanced by direct addition, or indirectly as a consequence of winemaking practices. Given its role as aroma precursor, it’s not known what the effect of glutathione is on the expression of terroir and varietal characters; and glutathione has also been reported to act as precursor to a range of desirable and negative sulfur aroma compounds. Much of the previous work associated with glutathione manipulation has targeted Sauvignon Blanc, aiming to preserve varietal thiols and colour in bottled wine. While thiols also contribute to the character of wines made from other varieties, the impact of glutathione addition on wine quality and style is relatively unknown. This project aims to extend current understanding about the effects of glutathione additions in white juices and wines, in other varieties as well as in Sauvignon Blanc.
This project is a continuation of the existing four-year Wine Australia Project AWR 1502 that commenced in June 2016. The research plan includes studies of protective juice treatments, the effects of direct glutathione addition, and an assessment of microbial consumption of glutathione. The fate of added glutathione will be determined through use of labelled compounds, which will aid in the determination of the degree to which glutathione turnover contributes to H2S production. Finally, small-scale winemaking trials will be used to assess the sensory and chemical impact of glutathione treatments. This work will elucidate how glutathione in combination with other factors, can be used during grape processing to manipulate or preserve grape aroma compounds and wine quality, typicity and regional characters.