 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

Exploring zoxamide sensitivity in Plasmopara viticola populations: implications for fungicide management in precision agriculture

Fungicides play a critical role in managing grapevine downy mildew caused by the oomycete Plasmopara viticola, a biotrophic and polycyclic pathogen with a high risk of fungicide resistance. Zoxamide, categorized as a low to medium resistance risk, disrupts cell division by inhibiting tubulin polymerization. Resistance to zoxamide is uncommon in field isolates. This six-year study (2017-2022) aimed to detect and quantify zoxamide sensitivity in P. viticola populations across varying resistance pressures in Italian grapevine regions. Analysis of 126 samples from 57 vineyards, mainly in North-Eastern Italy, revealed that most samples exhibited EC50, EC95, and MIC values below 0.1 and 10 mg/L of zoxamide, respectively. Nineteen vineyards showed reduced sensitivity (MIC>100 mg/L), but only four samples were characterized by 24-54% resistant oospores at >100 mg/L of zoxamide.

Is it possible to approximate the technological and phenolic maturity of grapes by foliar application of elicitors?

The increase in the temperature and the more severe water stress conditions, trends observed in recent years as a consequence of climate change, are leading a mismatch between the technological and phenolic maturity of grapes

Rootstock selection moderates the effect of rising temperatures through drought tolerance and modulation of stomatal conductance

Climate change is increasing crop evapotranspiration and reducing water availability, especially in the Mediterranean area.

Impact of some agronomic practices on grape skins anthocyanin content

Wine colour is the first quality characteristic to be assessed, especially regarding red wines. Anthocyanins are very well known to be the main responsible compounds for red wine colour. Red cultivars can synthesize and accumulate anthocyanins in berry skin to express their colour. However, anthocyanin accumulation is often influenced by a series of factors, such as genetic regulation, phytohormones, environmental conditions and viticultural management.

FLAVONOID POTENTIAL OF MINORITY RED GRAPE VARIETIES

The alteration in the rainfall pattern and the increase in the temperatures associated to global climate change are already affecting wine production in many viticultural regions all around the world (1). In fact, grapes are nowadays ripening earlier from a technological point of view than in the past, but they are not necessarily mature from a phenolic point of view. Consequently, the wines made from these grapes can be unbalanced or show high alcohol content. Dramatic shifts in viticultural areas are currently being projected for the future (2).