terclim by ICS banner
IVES 9 IVES Conference Series 9 THE EFFECT OF COPPER ON THE PRODUCTION OF VARIETAL THIOLS DURING THE ALCOHOLIC FERMENTATION OF COLOMBARD AND GROS MANSENG GRAPE JUICES

THE EFFECT OF COPPER ON THE PRODUCTION OF VARIETAL THIOLS DURING THE ALCOHOLIC FERMENTATION OF COLOMBARD AND GROS MANSENG GRAPE JUICES

Abstract

Nowadays, the rapid growth of vineyards with organic practices and the use of copper as the only fungicide against downy mildew raises again the question of the effect of copper on varietal thiols in wine, especially 3-sulfanylhexan-1-ol (3SH) and its acetate (3SHA). A few decades ago, several works indicated that the use of copper in the vineyard had a negative effect on the content of varietal thiols in Sauvignon blanc wines [1, 2]. However, these studies only considered the concentration of the reduced form (RSH) of varietal thiols, without quantifying the oxidised ones. For this purpose, we proposed to monitor both reduced and oxidised forms of varietal thiols in wine under copper stress during alcoholic fermentation to have a more complete picture of the biological and chemical mechanisms. In the present work, Colombard and Gros Manseng grape juices were fermented under different copper levels (from 0.2 to 3.88 mg/L) to mimic the consequences of organic practices on grape and must. The consumption of thiol precursors and the release of varietal thiols (both free and oxidised forms of 3SH and 3SHA) were monitored by LC-MS/MS according to previously published methods [3, 4]. It was found that the highest copper content (3.6 and 3.88 mg/L for Colombard and Gros Manseng, respectively) significantly increased yeast consumption of precursors (by 9.0 and 7.6% for Colombard and Gros Manseng, respectively). Surprisingly, this higher consumption of precursors was not associated to higher thiol concentrations. Indeed, for both varieties, the content of free thiols in the wine decreased significantly (by 84 and 47% for Colombard and Gros Manseng, respectively) with the increase of copper in the starting must, as already described in the literature [1, 2]. However, the sum “reduced+oxidized” forms of 3SH produced during fermentation was constant for the Colombard must regardless of the copper conditions, which means that the effect of copper was only oxidative for this variety. In Gros Manseng, on the other hand, the sum “reduced+oxidized” forms of 3SH increased with the copper content, up to 90%. This last result suggests that copper probably modifies the regulation of the production pathways of varietal thiols and has also a key role of oxidation. These results complement our knowledge on the effect of copper during thiol-oriented fermentation and the importance of considering both “reduced+oxidized” forms to distinguish chemical from biological effects.

 

1. Darriet, P., et al., Effects of copper fungicide spraying on volatile thiols of the varietal aroma of Sauvignon blanc, Cabernet Sauvignon and Merlot wines. VITIS-GEILWEILERHOF-, 2001. 40(2): p. 93-100.
2. Hatzidimitriou, E., et al., Incidence d’une protection viticole anticryptogamique utilisant une formulation cuprique sur le niveau de maturité des raisins et l’arôme variétal des vins de Sauvignon:(Bilan de trois années d’expérimentation). Journal International des Sciences de la Vigne et du Vin, 1996. 30(3): p. 133-150.
3. Roland, A., et al., Innovative analysis of 3-mercaptohexan-1-ol, 3-mercaptohexylacetate and their corresponding disulfides in wine by Stable Isotope Dilution Assay and nano-liquid chromatography tandem mass spectrometry. Journal of Chromatography A, 2016. 1468: p. 154-163.
4. Bonnaffoux, H., et al., First identification and quantification of S-3-(hexan-1-ol)-γ-glutamyl-cysteine in grape must as a potential thiol precursor, using UPLC-MS/MS analysis and stable isotope dilution assay. Food Chemistry, 2017. 237: p. 877-886

DOI:

Publication date: February 9, 2024

Issue: OENO Macrowine 2023

Type: Poster

Authors

G. Dournes1, T. Dufourcq², L. Suc1, J.-R. Mouret1 and A. Roland1*

1. SPO, Université de Montpellier, INRAE, Institut Agro, Montpellier, France
2. Institut Français de la Vigne et du Vin, Pôle Sud-Ouest, Caussens, France

Contact the author*

Keywords

3-sulfanylhexan-1-ol, copper, alcoholic fermentation, yeast

Tags

IVES Conference Series | oeno macrowine 2023 | oeno-macrowine

Citation

Related articles…

VOLATILE COMPOSITION OF WINES USING A GC/TOFMS: HS-SPME VS MICRO LLE AS SAMPLE PREPARATION METHODOLOGY

Wine aroma analysis can be done by sensorial or instrumental analysis, the latter involving several me-thodologies based on olfactometric detection, electronic noses or gas chromatography. Gas Chromatography has been widely used for the study of the volatile composition of wines and depending on the detection system coupled to the chromatographic system, quantification and identification of individual compounds can be achieved.

Read More

REGULATION OF CENTRAL METABOLISM IN THE LEAVES OF A GRAPE VINES VA- RIETAL COLLECTION ON A TEMPERATURE CLINE

Grape (Vitis vinifera) is one of the world’s oldest agricultural fruit crops, grown for wine, table grape, raisin, and other products. One of the factors that can cause a reduction in the grape growing area is temperature rise due to climate change. Elevated temperature causes changes in grapevine phenology and fruit chemical composition. Previous studies showed that grape varieties respond differently to a temperature shift of 1.5°C; few varieties had difficulties in the fruit development or could not reach the desired Brix level.

Read More

ALCOHOLIC FERMENTATION AND COLOR OF ROSÉ WINES: INVESTIGATIONS ON THE MECHANISMS RESPONSIBLE FOR SUCH DIVERSITY

Color is one of the key elements for the marketing of rosé wines due to their packaging in transparent bottles. Their broad color range is due to the presence of pigments belonging to phenolic compounds extracted from grapes or formed during the wine-making process. However, the mechanisms responsible for such diversity are poorly understood. The few investigations performed on rosé wines showed that their phenolic composition is highly variable, close to that of red wines for the darkest rosés but very different for light ones [1]. Moreover, large variations in the extent of color loss taking place during fermentation have been reported but the mechanisms involved and causes of such variability are unknown.

Read More

INOCULATION OF THE SELECTED METSCHNIKOWIA PULCHERRIMA MP1 AS A BIOPROTECTIVE ALTERNATIVE TO SULFITES TO PREVENT BROWNING OF WHITE GRAPE MUST

Enzymatic browning (BE) of must is caused by polyphenol oxidases (PPOs), tyrosinase and laccase. Both PPOs can oxidize diphenols such as hydroxycinnamic acids (HA) to quinones, which can later polymerize to form melanins [1], which are responsible of BE in white wines and of oxidasic haze in red wines. SO₂ is the main tool used to protect must from BE thanks to its capacity to inhibit PPOs [2]. However, the current trend in winemaking is to reduce and even eliminate this unfriendly additive. Among the different possible alternatives for protecting must against BE, the inoculation with a selected Metschnikowia pulcherrima MP1 is without any doubt one of the most promising ones.

Read More

SENSORY CHARACTERIZATION OF COGNAC EAUX-DE-VIE AGED IN BARRELS REPRESENTING DIFFERENT TOASTING PROCESS

Cognac is an outstanding french wine spirit appreciated around the world and produced exclusively in the Nouvelle-Aquitaine region, and more precisely in the Cognac area. According to AOC regulations (Appellation D’origine Controlée), the spirit required at least 2 years of continuous ageing in oak barrels to be granted the title of Cognac. The oak wood will import color, structure and organoleptic complexity. The different steps during barrel-making process, such as seasoning and toasting, influence the above quality attributes in both wines and spirits.

Read More