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

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

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

International audienc

Absolute configuration of free and bound 3-hydroxy-B-Damascone and of 3-oxo-a-ionol B-D-glucopyranoside in tobacco

International audienc

Connaissance aromatique des cepages et qualite des vins

National audienc

Effect of use of pure yeast culture (Saccharomyces cerevisiae-K1) on aromatic compounds of emir wine [Emir üzümünün şaraba i·şlenmesinde saf maya (Saccharomyces cerevisiae-K1) kullaniminin aroma maddeleri üzerine etkisi]

In this study, aroma compounds of the wines obtained from white Emir grapes grown in Nevşehir-Ürgüp region by spontanous fermentation and by use of pure culture of "Saccharomyces cerevisiae-K1" were investigated. Aroma compounds were extracted by Amberlit XAD-2 resin and were eluted by pentan/dichloromethane (2/1) solvent and then analysed by gas chromatography and identified by gas chromatography mass spectrometry (GC-MS). A comparison of the aroma compounds of the wines obtained by spontanous fermentation and by use of pure culture showed that the latter contained higher amount of high alcohols and carbonyl compounds, and lower amount of volatile phenols, esters being at the same level. Additionally, it was found that 4-vinylphenol and 4-vinylguaiacol formed by "Saccharomyces cerevisiae-K1" was very low because of the poor decarboxylase activity of this strain. Statistical analysis of sensory evaluation showed that there was a significant difference between the wines. However, the difference between the wines in terms of the preference of the panel members was not significant

Effect of simulated alcoholic fermentation on aroma components of grape berries during anaerobic metabolism

International audienc

Méthode d'analyse de composés volatils de baies de raisin en hypoxie

National audienc

Anaérobiose carbonique du raisin Muscat. 2 - Evolution de la répartition des terpénols libres et liés

International audienc