 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

The “resources profile®”: a relevant decision and support system for adapting viticultural practices to soils agronomic properties and limiting their environmental impacts

Soil is a three-dimensional complex system, which constitutes a major component of Terroir. Soil characteristics strongly influence vine development, grape oenological potentialities and thus wine quality and style.

Intra-block variations of vine water status in time and space

Vine water status was measured on 96 plots of three vines inside a vineyard block of 0.28 ha during three years: 2003, 2004 and 2005. Three physiological indicators were implemented: stem water potential, carbon isotope discrimination measured on grape sugars at ripeness (δ13C) and canopy temperature measured by high resolution remote sensing. For stem water potential, measurements were taken on every single vine of each plot.

Optimized protocol for high-quality RNA extraction from grape tissues using sorbitol pre-wash

Obtaining high-quality RNA from grape tissues, including berry pulp, berry skins, stems, rachis, or roots, is challenging due to their composition, which includes polysaccharides, phenolic compounds, sugars, and organic acids that can negatively affect RNA extraction. For instance, polyphenols and other secondary metabolites can bind to RNA, making it difficult to extract a pure sample. Additionally, RNA can co-precipitate with polysaccharides, leading to lower extraction yield. Also, sugars and organic acids can interfere with the pH and ionic properties of the extraction buffer. To address these challenges, we optimized a protocol for RNA isolation from grape tissues.

Towards multi-purpose valorisation of polyphenols from grape pomace: Pressurized liquid extraction coupled to purification by membrane processes

Grape by-products (including skins, seeds, stems and vine shoots) are rich in health promoting polyphenols. Their extraction from winery waste and their following purification are of special interest to produce extracts with high added value compounds. Meanwhile, the growing concern over environmental problems associated with economic constraints, require the development of environmentally sustainable extraction technologies. The extraction using semi-continuous subcritical water, as a natural solvent at high temperature and high pressure a technology is promising “green” technology that is environmentally friendly, energy efficient and improve the extraction process in plant tissues.

Facteurs physiques et biologiques affectant la production viticole et vinicole de la région avec dénomination d’origine “Condado de Huelva” (SW d’Espagne)

Les facteurs physiques et biologiques du milieu naturel affectant la production viticole de la R.D.O. “Condado de Huelva” et quelques relations les concernant sont étudiés dans les systèmes de la production vinicole ; le bon fonctionnement du Vignoble ayant besoin par ailleurs, du concours d’autres facteurs (Reynier, 1989 ; Paneque et al., 1996, a,b).