<p style="text-align: justify;">Les auteurs proposent une nouvelle technique d'estimation du degré de polymérisation des tanins du raisin et du vin, utilisant un aldéhyde spécifique des structures phénoliques renfermant des noyaux phloroglucinols ; la ρ-dimethylaminocinnamaldéhyde (DMACH). Cet aldéhyde est utilisé pour la première fois pour la détermination du degré de condensation des procyanidines. L'indice obtenu avec cet aldéhyde est d'autant plus faible que le degré de polymérisation des tanins est élevé. Le protocole retenu permet de réaliser des mesures avec un coefficient de répétabilité moyen de 5 p. cent (au seuil de confiance α = 95 p. cent). La méthode permet, d'une part d'estimer le degré de polymérisation moyen des procyanidines et d'autre part de mesurer l'influence de certaines pratiques (consommation de l'oxygène dissous, ajout d'acetaldéhyde, supplémentation en extrait phénolique) sur la variation du degré de condensation moyen des tanins.</p>
<p style="text-align: justify;">Au cours de ce nouveau travail, nous nous proposons d'étudier l'adsorption et la désorption sélective des composés phénoliques du vin rouge sur la p.v.p., appliquée plus particulièrement au fractionnement des flavolanes.</p>
Seed extracts of one clone of Merlot Noir were studied during maturation using low-pressure and high-performance liquid chromatography to observe changes in composition and to follow the evolution of the main procyanidins. These observations have prompted our laboratory to investigate the polymerisation of procyanidins associated with their extraction with an alcoholic solvent. We report the observed correlations for procyanidin dimers, which are relatively high between procyanidins B 2 /C 1 /A 2 themselves (linked by C 4 -C 8 bond), but which are non-existent between procyanidins linked by C 4 -C 8 and by C 4 -C 6 bonds. These observations have enabled us to propose a hypothesis regarding procyanidin oligomer biosynthesis.
Abstract.Proceeding with a similar way as previous works, we characterised the presence of lignins in wines. This natural polymer was chosen as biomarker. It's a remarkably stable in time and typical wood component. We used the thioacidolysis reaction with ethanethiol and boron trifluoroetherate as reagents, to obtain some characteristic phenylpropane units from the lignin polymer. Identification was performed by mass spectrometry coupled with gas chromatography (GPG/SM) of thioacidolysis products in trimethylsililated form. The aim of this study is the demonstration of wine aging in barrel before bottling.
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