Les anthocyanes des feuilles de différentes varietés de Vitis vinifera L. entre la véraison des raisins et la chute des feuilles

The contents of total and individual anthocyanins in red leaves of three Vitis vinifera L. cvs (Merlot noir, Cabernet Sauvignon and Gamay Freaux) was determined by HPLC at three stages of seasonal development (veraison and maturity of grapes, leaf fall). The anthocyanin composition of leaves and berries was rather different. There was some variation between cultivars: leaves of the red-juice grape were richer in anthocyanins than leaves of the non-colouring cultivars. In all cultivars, the anthocyanin content of leaves increased during grapeberry maturation, then decreased until leaf fall

Global volatile signature and polyphenols patterns in Vespolina wines according to vintage

The global volatile signature of Vespolina wines from different vintages was established using solid-phase microextraction combined with gas chromatography–mass spectrometry (HS-SPME/GC-qMS). Wines were also characterised in terms of bioactive compounds (such as individual polyphenols, biogenic amines and their precursors) by high-performance liquid chromatography (RP-HPLC). In addition, some physic ochemical parameters, such as the total phenolic content, total tannins and antioxidant capacity, were evaluated. Seventy-one volatile compounds and thirty-three bioactive compounds were identified in Ves polina wines. The application of multivariate analysis to the obtained data revealed that 2-phenylethyl acetate, ethyl nonanoate, 2-hexanol, isoamyl octanoate and ethyl 2-hydroxymethylbutanoate were the pri mary compounds responsible for Vespolina wines classification, mainly indicative for wines of 2015 and 2013 vintages. Conversely, wines from 2008 and 2009 vintages showed highest values of procyanidin B1, catechin, gallic acid, trans-piceid and trans-resveratrol.info:eu-repo/semantics/publishedVersio

Localisation des tanins dans la pellicule de baie de raisin

La localisation des taoins dans Ja pellicule de raisin a été étudiée en combinant les resultats obtenus par deux méthodes: observation microscopique (photonique et électronique à  transmission), et analyse chimique de différentes fractions obtenues après isolement des cellules pelliculaires sous forme de protoplastes. Trois grands groupes de tanins ont ainsi été déterminées selon leur localisation: tanins libres dans le suc vacuolaire, visualisés sous forme de granules qui augmentent de taille au fur et à mesure que l'on se rapproche de la surface de la pellicule; des tanins liés ont été mis en évidence dans deux autres localisations: tanins liés aux polysaccharides des parois cellulaires par des liaisons osidiques et tanins liés avec les protéines constitutives de la face interne des membranes vacuolaires.Localization of tannins in grape berry skinsThe localization of tannins in grape berry skins has been studied by associating results obtained with two methods: light and transmission electron microscopy, and chemical analysis of the fractions obtained after isolation of cells as protoplasts. According to their location, three groups of tannins were determined. The first consists of free tannins in solution in the vacuolar sap (these tannins appear in the form of granules decreasing in size from the skin surface to the pulp). Two other groups are constituted by bound tannins: those bound to the proteins of the internal face of the tonoplast, and those bound to the cell wall polysaccharides by osidic bonds

Influence de SO2 et de l'acide ascorbique sur l'activité antiradicalaire des tanins, mesurée sur l'anion superoxyde. Application aux vins rouges

Pour des concentrations habituellement utilisées en oenologie, le SO2 ne presente pas d'activité antiradicalaire à l'égard de l'anion superoxyde. L'acide ascorbique est un antiradicalaire dont les performances sont fonction de sa concentration. Les différents tanins testés présentent tous de très importantes activités antiradicalaires. Dans les vins rouges, ce sont donc pour l'essentiel les procyanidines qui captent les radicaux libres superoxydes. Influence of SO2 and ascorbic acid on the scavenger effect of tannins, measured on superoxide anion. Application to red wines At usual oenological concentrations SO2 does not have a scavenger effect on superoxide anion. Ascorbic acid is an antiradical the effect of which varies with concentration. Different tannins, e.g. castalagin, pentagalloylglucose, procyanidins B2 and B4, (+)-catechin and garlic acid, are shown to have significant antiradical effects. In red wines in particular procyanidins have a scavenger effect on free superoxide radicals