Glycosidase activities in sound and rotten grapes in relation to hydrolysis of grape monoterpenyl glycosides

β-D-glucopyranosidase, α-L-arabinofuranosidase and α-L-rhamnopyranosidase activities were studied in grapes, both during maturation and in sound and rotten mature fruits. Enzymic activities increased during maturation. At maturity, in sound grapes, β-D-glucopyranosidase and α-L-arabinofuranosidase activities were the highest ones. Berry infection by fungi results in a decrease in β-glucosidase activity, while the others increase. The effect of an enzymic extract from a culture of Botrytis cinerea towards synthetic terpenyl glycosides showed that hydrolysis was strong for β-terpenyl rutinosides and weak for β-terpenyl 6-0-α-L-arabinofuranosyl-β-D-glucopyranosides

Différentiation des cépages portugais Loureiro et Alvarinho basée sur la composition monoterpénique libre

IBQF; Com. Vit. Região Vinhos Verdes (EVAG); Adega C.R. Monção; Casa da Tapada

Teneur en norisoprénoïdes en c13 des cépages Portugais loureiro et alvarinho

Les cépages portugais Loureiro et Alvarinho sont importants pour l'économie de la Région portugaise des "Vinhos Verdes". Ces deux variétés de raisin sont à l'origine de vins blancs monovarietaux réputés, présentant des caractéristiques aromatiques intéressantes. Ce travail a pour objectif d'approfondir les connaissances sur l'une des composantes du potentiel aromatique de ces deux cépages, les norisoprénoïdes en C13, composés dérivés des caroténoïdes. Les essais ont été conduits sur des échantillons de raisins du millésime 1996, deux de Loureiro et deux d'Alvarinho, provenant de deux sub-régions des "Vinhos Verdes", les plus recommandées pour l'obtention de vin de qualité; un troisième échantillon d'Alvarinho provient d'un type de sol différent. Quatorze composés norisoprénoïdes en C13 ont été identifiés et quantifiés dans la fraction glycosylée des deux variétés. Une analyse en composantes principales utilisant les teneurs en ces composés permet de distinguer nettement les deux cépages. L'Alvarinho est un peu plus riche que le Loureiro, notamment en ce qui concerne le 3-oxo-7,8-dihydro-α-ionol, le 3-hydroxy-7,8-déhydro-β-ionol, le 3-oxo-α-ionol et la 3-hydroxy-β-damascone. Par contre le Loureiro contient des teneurs plus élevées en 3- hydroxy-7,8-dihydro-β-ionol.IBQF ; Ambassade de France au Portuga l; JNICT ; Comissão de Viticultura da Região dos Vinhos Verdes (EVAG) ; Adega C.R. Monção ; Casa da Tapada ; Solar de Serrade

Etude de la composition lipidique du raisin, Vitis vinifera L.: Evolution au cours de la maturation et localisation dans la baie

Lipid composition of grapevine berries, Vitis vinifera L.:Changes during maturation and localization in the berryQuantitative determinations in four grapevine varieties, Vitis vinifera L., gave evidence that the level of fatty acids in mature be rries was around 0.045 %, for t he main part unsaturated acids. Linoleic, pa lmit ic, linolenic and oleic acids were the most abundant, followed by stearic and behenic acids . No free fatty acids were found. Phospholipids formed the largest fraction prior to neutral and glycolipids. Glycolipids showed a high level of linolenic acid, while in phospho- and neutral lipids linoleic acid was highest. In the three fractions, polyunsaturated acids made up more th an half of total fatty acids. No differences were found between grape varieties. During grape maturation, changes in fatty acid levels were low, except for linolenic acid, which decreased consistently, this decline was concerned with neutral and glycolipids. Consequently, the potential of herbaceous flavour decreased progressively during berry maturation. Fatty acids were 1.5-3 times lower in pulp than in skin; thus, the skin can contribute to a large enrichment of fatty acids in juice, polyunsaturated derivatives, especially linolenic acid, being highest. In consequence, the presence of a !a rge part of grape herbaceous flavour potential in the skin was confirmed. Fatty acid patterns were s imilar in pulp and in skin, with more than half consisting of polyunsaturated compounds. There were a lso identical patterns for other lipids such as phospholipids, which were t he most abundant, followed by neutral and glycolipids

La macération pelliculaire dans la vinification en blanc - Incidence sur la composante volatile des vins

Skin contact in white wine processing- Effects on the volatile constituents of winesWines were made from three different white vine cultivars, Chenin, Chardonnay, Bourboulenc by standard white wine processing, with and without skin contact, and their volatile constituents were analysed using gas chromatography standard procedures. 61 substances were identified and quantified in quadruplicate. One-way analyses of variance for each component were performed in which skin contact wine was compared to the control wine for each vine cultivar. Skin contact was shown to increase significantly most volatile components except volatile acids. In attempt to classify the wines investigated, principal component analysis was conducted using the amounts of compounds differing significantly in variance analysis

The flavour of muscat wine: the sensory contribution of some volatile compounds

International audienc

Glycosides des terpenols precurseurs d'aromes: exemple du raisin

National audienc

Influence of wine structurally different polysaccharides on the volatility of aroma substances in a model system

International audienc