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IVES 9 IVES Conference Series 9 OIV 9 OIV 2024 9 Orals - Oenology, methods of analysis 9 Evolution of oak barrels C-glucosidic ellagitannins

Evolution of oak barrels C-glucosidic ellagitannins

Abstract

During oak wood contact, wine undergoes important modifications that modulate its organoleptic quality and complexity, including its aroma, structure, astringency, bitterness and color. Vescalagin and castalagin are the two main c-glucosidic ellagitannins found in oak wood used for wine aging wood but lyxose/xylose derivatives (grandinin and roburin e) and dimeric forms (roburins a,b, c and d) are also present. The presence of several hydroxyl groups in the ortho-positions at the periphery of the structure of the ellagitannin isomers allows these molecules to undergo oxidation or condensation reactions with other compounds. The hydroalcoholic nature of wine allows the extraction of these compounds from wood to wine, but due to their high reactivity, their levels in wine are much lower than could be expected. Natural or artificial.  In order to know the compounds that oak wood yields to the wine, the use of synthetic wine has the advantage of ensuring the absence of any microbial activity. At the same time, by using synthetic wine, ensures that no fermenting compounds,which could also come from the barrels, will exist. To better understand the net oak wood impact on wine composition, a model wine was used in two 225 l barrels. This approach minimized any effect which may have arisen due to compounds naturally present in wines, and kept away microbial activity. Therefore, the objectives of the present study were i) to study oak barrels ellagitannins evolution after 12 months of aging  and ii) to determine their derived forms using lc/ms and 1d/2d-nmr spectroscopy.  The 8 principal c-glucosidic ellagitannins extracted after 1 month of oak wood contact, whereas their concentration increased drastically after 2 months, varied from 2.64 mg/l to 25.16 mg/l in the case of vesacalagin. Hydrolysis, reduction, oxidation, and substitution reactions took place after one month of oak wood contact. Among such evolutionary compounds, β-1-o-ethylvescalagin formed by the reaction of ethanol on the hydroxylated c-1 center of vescalagin through a nucleophilic substitution has been identified. A derivative form of vescalagin oxidative solvolysis has also been appeared at two months of contact. The oxidation form of castalagin and the reduction form of its diastereomer vescalagin appeared after one month of contact. These results constitute an initial approach of comprehensive ellagitannins evolution during aging in model wine solution being in contact with oak barrels.

Évolution des ellagitanins c-glucosidiques du bois de chêne 

Lors du contact avec le bois de chêne, le vin subit des modifications importantes qui modulent sa qualité organoleptique et sa complexité, notamment ses arômes, sa structure, son astringence, son amertume et sa couleur. La vescalagine et la castalagine sont les deux principaux ellagitanins c-glucosidiques que l’on trouve dans le bois de chêne utilisés pour l’élevage du vin, mais leurs dérivés glycosidiques avec lyxose/xylose (grandinine et roburine e) et leurs formes dimériques (roburines a, b, c et d) sont également présents. La position des groupes hydroxyle des ellagitanins permet à ces molécules de subir des réactions d’oxydation ou de condensation avec d’autres composés. La nature hydroalcoolique du vin permet l’extraction de ces composés à partir du bois de chêne au vin, mais en raison de leur forte réactivité, leurs niveaux dans le vin sont beaucoup plus faibles par rapport à quoi on pourrait s’attendre.  Afin de connaître les composés que le bois de chêne apporte au vin, l’utilisation de la solution modele du vin assure l’absence de toute activité microbienne. A même temps, il garantit qu’il n’y aura pas de composés de fermentation, qui pourraient également provenir du bois de chêne. Pour mieux comprendre l’impact net du bois de chêne sur la composition du vin, une solution modèle du vin a été utilisé dans deux fûts de 225 l. Cette approche a minimisé tout effet qui aurait pu se produire en raison de composés naturellement présents dans le vin. Par conséquent, les objectifs de la présente étude étaient i) d’étudier l’évolution des ellagitanins en fûts de chêne après 12 mois d’elevage et ii) de déterminer leurs formes dérivées en utilisant lc/ms et 1d/2d-nmr spectroscopie. Les 8 principaux ellagitanins c-glucosidiques sont extraits après 1 mois de contact avec le bois de chêne, alors que leur concentration augmente drastiquement après 2 mois, variant de 2,64 mg/l à 25,16 mg/l dans le cas de la véscalagine. Les réactions d’hydrolyse, de réduction, d’oxydation et de substitution ont eu lieu après un mois de contact avec le bois de chêne. Parmi ces composés d’evolution, β-1-o-éthylvescalagine formée par la réaction de l’éthanol sur le carbonne c-1 de la vescalagine par substitution nucléophile a été identifiée. Une forme dérivée de la solvolyse oxydative de la vescalagine est également apparue après deux mois de contact. La forme oxydative de la castalagine et la forme de reduction de son diastéréoisomère vescalagine sont apparues après un mois de contact. Ces résultats constituent une première approche de l’évolution complète des ellagitanins au cours de l’élevage en solution modèle du vin qui était en contact avec le bois de chêne.

Publication date: November 18, 2024

Issue: OIV 2024

Type: Article

Authors

Chira Kleopatra¹, Barbara Reyes Gamboa¹, Pierre-Louis Teissèdre¹

¹ Unité mixte de recherche 1366 œnologie, INRAE, Bordeaux INP, Institut des Sciences de la Vigne et du Vin, Université de Bordeaux – 210 chemin de Leysotte – CS 50008, Villenave d’Ornon, France

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Tags

IVES Conference Series | OIV | OIV 2024

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