Monitoring of glutathione concentration during winemaking by a reliable high-performance liquid chromatography analytical method

Background and Aims: Glutathione (GSH) is valued in winemaking as an effective antioxidant in must and white wine if its concentration exceeds a few milligrams per litre. We report the further improvement of a previous analytical method for GSH quantification and its application to the analysis of grapes and wines. Methods and Results: Glutathione was derivatised with p-benzoquinone and detected by HPLC/UV. The analytical method was sensitive (limit of quantification, 0.43mg/L), linear (R2>0.997), accurate (recovery, 101% in grape juice and white wine) and repeatable (relative standard deviation, 3.1). The monitoring of vinifications at commercial wineries showed that Saccharomyces cerevisiae was a main source of GSH in wine, since the GSH of the grape was poorly preserved following juice preparation. Glutathione concentration decreased during wine aging on yeast lees. Conclusion: Glutathione concentration varied considerably during winemaking, and thus monitoring is essential for improving wine flavour and preventing oxidation. This method is suitable for this purpose. Significance of the Study: The analytical method proposed is reliable, fast and easy-to-apply and allows the assessment of the GSH in grape, must and wine. The strong role of the yeast on the GSH concentration in wine is reported.