 IVES 9 IVES Conference Series 9 Evaluating analytical methods for quantification of glutathione in grape juice and wine

Evaluating analytical methods for quantification of glutathione in grape juice and wine

Abstract

AIM: Glutathione (GSH) is a powerful natural antioxidant, considered as a promising molecule against oxidative damage of aroma during winemaking and storage. His concentration in the grape juice is variable. Enological practice in the cellar can promote the preservation of the GSH in the grape juice. Recently the prescription of OIV allows to add glutathione rich substances to the must. This new practice creates an increasing interest in the quantification of GSH. Several analytical methods were published to measure GSH[1,2,3,4] and his dimer (GSSG) separately[5] or together as total glutathione[6] content. In this work we compared two analytical methods for the analyses of grape juice and wine samples.

METHODS: The first method is an enzymatic assay (EA), based on the reaction of thiol with DTNB in the presence of glutathione reductase enzyme to measure the total glutathione content. This method was automatized to allow high through-put measurements in the concentration range of 5-100mg/l. The second method, using UPLC-MS/MS, is more sensitive (LOD = 0.5mg/l) and permits simultaneous quantification of GSH, GSSG and additionally the sulfonated form of glutathione (GSSO3H).

RESULTS: The best results were obtained with 2.5g/l ascorbic acid. Using the two analytical methods, we found a strong correlation (R2=0.98) between the total glutathione (EA) and the sum of GSH and GSSG (UPLC-MS/MS) in grape juice samples (n>100), where the GSSO3H concentration was low (0-8 mg/l) comparing to the GSH and GSSG (5-100mg/l). In wine samples the total glutathione concentration was low (2-7mg/l) and the GSSO3H was more important (5-9mg/l) due to the combination of SO2 with the glutathione. View the high reactivity of GSH, a special attention should be accorded to the preparation and the storage of grape juice samples. We compared the effect of different concentration of SO2 and ascorbic acid as additives and found that 2.5g/l ascorbic acid gave the best results.

CONCLUSION

Based on our results the enzymatic assay is an economic alternative to measure the total glutathione concentration of grape juice. However for wine the UPLC-MS/MS method is recommended, to reach the necessary sensitivity and to analyze all glutathione species.

DOI:

Publication date: September 7, 2021

Issue: Macrowine 2021

Type: Article

Authors

Ágnes Dienes-Nagy

Agroscope, Nyon, Switzerland,Frédéric VUICHARD, Agroscope, Nyon, Switzerland Marie BLACKFORD, Agroscope, Nyon, Switzerland Fabrice LORENZINI, Agroscope, Nyon, Switzerland

Contact the author

Keywords

glutathione, enzymatic assay, uplc-ms/ms

Citation

Effect of supplementation with inactive yeast during alcoholic fermentation in base wine for sparkling

INTRODUCTION: Foam stability of sparkling wines is significantly favored by the presence of surface active agents such as proteins and polysaccharides [1]. For that reason, the renowned sparkling wines are aged after the second fermentation in contact with the lees for several months (even years). Thereby wines are enriched in these macromolecules due to yeast autolysis. Since this practice is slow and costly, winemakers are seeking for alternative procedures to increase their concentration in base wines. In that sense, the supplementation with inactive yeast during alcoholic fermentation has been proposed [2]. The aim of this study was to determine whether this new strategy is really useful for enriching base wines in macromolecules and for improving foam properties of the base wines.

The Soil Component of Terroir

Evidence for a specific effect of soil mineral composition on wine character is largely anecdotal. However, soil potassium supply to the vine must be properly balanced between deficiency and excess for good fruit quality.

Vine growing description of Aeolian archipelago

An agroclimatic description of Aeolian archipelago viticulture area (Me), Italy is presented. Aeolian archipelago is located off the northeastern coast of Sicily and it includes the islands of Alicudi, Filicudi, Salina, Panarea, Lipari, Stromboli and Vulcano.

Evaluation of the composition of pomace from grapes grown in the slopes of the Popocatépetl volcano (Puebla, Mexico). Feasibility of its application for obtaining functional foods

Grape pomace is the main byproduct generated during wine production and is primarily composed of skins and seeds, which are obtained after the pressing stage [1]. This byproduct retains a significant amount of nutrients, such as fiber, phenolic compounds, unsaturated fatty acids, vitamins, and minerals.

The Baco Blanc, the Armagnac hybrid variety adapted to the viticultural challenges of tomorrow

Today in the wine industry, a lot of alternatives are available for reducing phytosanitary inputs. Among these, prophylaxis, the use of biocontrol products and the deployment of pathogen-resistant vines are the most promising. eugenol (2-methoxy-4-(2-propenyl)-phenol), a molecule with recognised antifungal properties, can contribute to the last two alternatives. This molecule has been identified as an endogenous compound in the baco blanc hybrid variety used in armagnac pdo, which is at least tolerant to botrytis cinerea.