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, 0.43 mg/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.