Macrowine 2021
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

Related articles…

Effect of one-year cover crop and arbuscular mycorrhiza inocululation in the microbial soil community of a vineyard

The microbial composition of the soil is an important factor to consider in viticulture, since its influence on the “terroir” and on the organoleptic properties of the wine have been demonstrated. Different agronomic techniques have the potential to modify the composition and functionality of the soil microbial community. Maintaining green covers is known to increase soil microbial diversity. The direct application of inoculum of beneficial microorganisms to the soil has also been used to increase their abundance. However, the environmental conditions of each site seem to have a determining weight in the result of these practices. In this study, we compared the effect on the microbial community of a cover crop with legumes in autumn and the inoculation of grapevines with commercial inoculum bases on Rhizophagus irregularis and Funeliformis mosseae in the previous spring. The study has been carried out in a vineyard in Binissalem, Mallorca, Spain. After applying the treatments, we will analyze the soil microbial communities using the data obtained from Illumina amplification of soil DNA from the 16S and ITS regions to analyze bacteria and fungi community, respectively. In addition, we will record the physicochemical characteristics of the soil at each sampling point. The result showed that agronomic management, in the short term, has less influence than soil characteristics on the composition of the soil microbiome. With these results, we can conclude that in a vineyard, agricultural techniques should focus on improving the characteristics of the soil to improve the biodiversity of the soil microbiota.

The interplay between grape ripening and weather anomalies – A modeling exercise

Current climate change is increasing inter- and intra-annual variability in atmospheric conditions leading to grapevine phenological shifts as well altered grape ripening and composition at ripeness. This study aims to (i) detect weather anomalies within a long-term time series, (ii) model grape ripening revealing altered traits in time to target specific ripeness thresholds for four Vitis vinifera cultivars, and (iii) establish empirical relationships between ripening and weather anomalies with forecasting purposes. The Day of the Year (DOY) to reach specific grape ripeness targets was determined from time series of sugar concentrations, total acidity and pH collected from a private company in the period 2009-2021 in North-Eastern Italy. Non-linear models for the DOY to reach the specified ripeness thresholds were assessed for model efficiency (EF) and error of prediction (RMSE) in four grapevine cultivars (Merlot, Cabernet Sauvignon, Glera and Garganega). For each vintage and cultivar, advances or delays in DOY to target specified ripeness thresholds were assessed with respect to the average ripening dynamics. Long-term meteorological series monitored at ground weather station by means of hourly air temperature and rainfall data were analyzed. Climate statistics were obtained and for each time period (month, bimester, quarter and year) weather anomalies were identified. A linear regression analysis was performed to assess a possible correlation that may exist between ripening and weather anomalies. For each cultivar, ripeness advances or delays expressed in number of days to target the specific ripening threshold were assessed in relation to registered weather anomalies and the specific reference time period in the vintage. Precipitation of the warmest month and spring quarter are key to understanding the effect of climate change on sugar ripeness. Minimum temperatures of May-June bimester and maximum temperatures of spring quarter best correlate with altered total acidity evolution and pH increment during the ripening process, respectively.

Short-term relationships between climate and grapevine trunk diseases in southern French vineyards

[lwp_divi_breadcrumbs home_text="IVES" use_before_icon="on" before_icon="||divi||400" module_id="publication-ariane" _builder_version="4.19.4" _module_preset="default" module_text_align="center" module_font_size="16px" text_orientation="center"...

Elevational range shifts of mountain vineyards: Recent dynamics in response to a warming climate

Increasing temperatures worldwide are expected to cause a change in spatial distribution of plant species along elevational gradients and there are already observable shifts to higher elevations as a consequence of climate change for many species. Not only naturally growing plants, but also agricultural cultivations are subject to the effects of climate change, as the type of cultivation and the economic viability depends largely on the prevailing climatic conditions. A shift to higher elevations therefore represents a viable adaptation strategy to climate change, as higher elevations are characterized by lower temperatures. This is especially important in the case of viticulture because a certain wine-style can only be achieved under very specific climatic conditions. Although there are several studies investigating climatic suitability within winegrowing regions or longitudinal shifts of winegrowing areas, little is known about how fast vineyards move to higher elevations, which may represent a viable strategy for winegrowers to maintain growing conditions and thus wine-style, despite the effects of climate change. We therefore investigated the change in the spatial distribution of vineyards along an elevational gradient over the past 20 years in the mountainous wine-growing region of Alto Adige (Italy). A dataset containing information about location and planting year of more than 26000 vineyard parcels and 30 varieties was used to perform this analysis. Preliminary results suggest that there has been a shift to higher elevations for vineyards in general (from formerly 700m to currently 850 m a.s.l., with extreme sites reaching 1200 m a.s.l.), but also that this development has not been uniform across different varieties and products (i.e. vitis vinifera vs hybrid varieties and still vssparkling wines). This is important for climate change adaptation as well as for rural development. Mountain areas, especially at mid to high elevations, are often characterized by severe land abandonment which can be avoided to some degree if economically viable and sustainable land management strategies are available.

Simulating climate change impact on viticultural systems in historical and emergent vineyards

Global climate change affects regional climates and hold implications for wine growing regions worldwide. Although winegrowers are constantly adapting to internal and external factors, it seems relevant to develop tools, which will allow them to better define actual and future agro-climatic potentials. Within this context, we develop a modelling approach, able to simulate the impact of environmental conditions and constraints on vine behaviour and to highlight potential adaptation strategies according to different climate change scenarios. Our modeling approach, named SEVE (Simulating Environmental impacts on Viticultural Ecosystems), provides a generic modeling framework for simulating grapevine growth and berry ripening under different conditions and constraints (slope, aspect, soil type, climate variability…) as well as production strategies and adaptation rules according to climate change scenarios. Each activity is represented by an autonomous agent able to react and adapt its reaction to the variability of environmental constraints. Using this model, we have recently analyzed the evolution of vineyards’ exposure to climatic risks (frost, pathogen risk, heat wave) and the adaptation strategies potentially implemented by the winegrowers. This approach, implemented for two climate change scenarios, has been initiated in France on traditional (Loire Valley) and emerging (Brittany) vineyards. The objective is to identify the time horizons of adaptations and new opportunities in these two regions. Carried out in collaboration with wine growers, this approach aims to better understand the variability of climate change impacts at local scale in the medium and long term.