Abstract
Glutathione (GSH, γ-L-Glutamyl-L-Cysteinyl Glycine) is a tripeptide of L-glutamate, L-cysteine and glycine. GSH in wine is derived from either grapes or yeast, during alcoholic fermentation. The GSH concentration in wine is very variable and depends on the environmental conditions as well as viticultural practices. During winemaking GSH has a significant role in oxidation prevention due to its unique redox and nucleophilic properties. Since GSH is very reactive it is highly important to prepare samples immediately and under inert conditions just prior to the determination of the GSH concentration. Therefore the aim of this research was to implement a method for the quantitative determination of GSH levels in grape juices (musts) made from different Austrian grape varieties and to investigate the influence of yeast on the GSH content in wine after aging. The results of this research have shown that monitoring with nitrogen gas, sulphur dioxide and freezing process at −25 ºC led to a good protective effect on the free glutathione amount in wine and grape samples. The GSH concentration in the samples was variable. Levels were ranging from non-detectable to up to 23.10 mg/l, and it showed that grape variety has no impact on GSH concentration in the must. Furthermore the results suggest that the choice of yeast has an impact on GSH content in wine even after 6 and 18 months of aging.
Highlights
IntroductionGSH is found in two forms in the cell: reduced (GSH) and oxidized as glutathione disulphide (GSSG) [1]
Glutathione (GSH) is a tripeptide of L-glutamate, L-cysteine and glycine
GSH is found in two forms in the cell: reduced (GSH) and oxidized as glutathione disulphide (GSSG) [1]
Summary
GSH is found in two forms in the cell: reduced (GSH) and oxidized as glutathione disulphide (GSSG) [1]. GSSG is formed during oxidation of GSH, and it can be reduced back to GSH by glutathione reductase [2]. GSH is derived either from grapes where it fulfills an important role in plant cells in terms of the antioxidant system, sulphur metabolism and the detoxification of xenobiotics or from yeast during fermentation [3]. It is found that, depending on stress conditions, yeasts are able to utilize and secret GSH during alcoholic fermentation, and in addition GSH is the main sulphur compound in the yeast's cell [4,5,6]. In must and wine GSH reacts with oxidized phenolic compounds, such as caftaric acid quinones or other oxidation products [8, 9]
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