Fate of the glutathione released from inactive dry yeast preparations during the alcoholic fermentation of white musts

Abstract

Background and Aims Inactive dry yeast (IDY) preparations are widely used in the winemaking industry. Among them, glutathione (GSH)-enriched IDY (g-IDY) preparations are claimed to preserve the aroma and colour of white wines due to their antioxidant properties. It remains uncertain, however, if alcoholic fermentation (AF) influences the fate of the GSH released by IDYs and the impact of these preparations on the oxidation status of the wine, which constitutes the aim of this study. Methods and Results The evolution of the GSH concentration of white musts treated with two types of IDYs (a glutathione-enriched IDY, g-IDY, and a fermentative nutrient n-IDY without GSH) and of a control must was determined during AF. In addition, the oxidation status of the musts and the formation of grape reaction product (GRP) derivatives were also monitored. The addition of g-IDYs had little effect on the concentration of reduced GSH in the wines at the end of fermentation. The treatment of musts with IDY preparations, however, reduced the formation of derivatives of GRP and produced more reductive conditions during AF compared with that of control samples. Conclusions These results indicate that GSH released by IDYs is not available at the end of AF, but other yeast components from these preparations could be involved in the greater antioxidant status of musts treated with IDYs. Significance of the Study This study helps to understand the impact of IDY preparations during winemaking, which will assist the optimisation of their formulation for specific wine applications.