Ethanol triggers grape gene expression leading to anthocyanin accumulation during berry ripening

Recent studies have shown that low doses of ethanol stimulate the maturation of some fruits. The present work showed that spraying Cabernet Sauvignon grapes, with 5% ethanol at veraison enhances the anthocyanin accumulation. Veraison is the time when the berries turn from green to purple. HPLC analysis showed a marked increase in the total concentrations of the derivatives of delphinidin, cyanidin, petunidin, peonidin and malvidin from the fourth day after the ethanol treatment until harvest. This was not linked to a difference in berry weight in comparison to controls. Two distinct expression patterns were found for anthocyanin biosynthesis genes in the treated and untreated berries. For one group, consisting of chalcone synthase, flavanone-3-hydroxylase, dihydroxyflavonol-4-reductase and leucoanthocyanidin dioxygenase, the expression was inhibited or unchanged by the ethanol treatment, whereas for UDP glucose-flavonoid 3-O-glucosyltransferase (UFGT) there was a marked increase in expression from 1 to 20 days after ethanol treatment. These results suggest that the UFGT gene is a key factor in the observed anthocyanin accumulation following ethanol treatment

Dissecting genetic architecture of grape proanthocyanidin composition through quantitative trait locus mapping

<p>Abstract</p> <p>Background</p> <p>Proanthocyanidins (PAs), or condensed tannins, are flavonoid polymers, widespread throughout the plant kingdom, which provide protection against herbivores while conferring organoleptic and nutritive values to plant-derived foods, such as wine. However, the genetic basis of qualitative and quantitative PA composition variation is still poorly understood. To elucidate the genetic architecture of the complex grape PA composition, we first carried out quantitative trait locus (QTL) analysis on a 191-individual pseudo-F1 progeny. Three categories of PA variables were assessed: total content, percentages of constitutive subunits and composite ratio variables. For nine functional candidate genes, among which eight co-located with QTLs, we performed association analyses using a diversity panel of 141 grapevine cultivars in order to identify causal SNPs.</p> <p>Results</p> <p>Multiple QTL analysis revealed a total of 103 and 43 QTLs, respectively for seed and skin PA variables. Loci were mainly of additive effect while some loci were primarily of dominant effect. Results also showed a large involvement of pairwise epistatic interactions in shaping PA composition. QTLs for PA variables in skin and seeds differed in number, position, involvement of epistatic interaction and allelic effect, thus revealing different genetic determinisms for grape PA composition in seeds and skin. Association results were consistent with QTL analyses in most cases: four out of nine tested candidate genes (<it>VvLAR1</it>, <it>VvMYBPA2</it>, <it>VvCHI1</it>, <it>VvMYBPA1</it>) showed at least one significant association with PA variables, especially <it>VvLAR1 </it>revealed as of great interest for further functional investigation. Some SNP-phenotype associations were observed only in the diversity panel.</p> <p>Conclusions</p> <p>This study presents the first QTL analysis on grape berry PA composition with a comparison between skin and seeds, together with an association study. Our results suggest a complex genetic control for PA traits and different genetic architectures for grape PA composition between berry skin and seeds. This work also uncovers novel genomic regions for further investigation in order to increase our knowledge of the genetic basis of PA composition.</p

Influence of sample and mobile phase pH on HPLC-DAD-MS analysis of anthocyanins and other phenolic compounds in wine

In this study, the influence of pH of the wine sample (pH 1.2 and 3.3) and of the HPLC mobile phase (1 and 2 % formic acid in the solvent) on anthocyanin and phenolic acid analysis was explored. Wine samples acidified at pH 1.2 were analyzed immediately, after 30 min, 2h and 3.5h, in order to check if any degradation of phenolic compounds occurred during the storage. Maximum response of the flavylium cation of peonidin-3-glucoside (at 520 nm), statistically significant (p 0.05), meaning that both 1% and 2% formic acid in the mobile phase are suitable for anthocyanin analysis. Regarding phenolic acids, lower peak intensities, statistically significant (p < 0.001), were obtained in the negative ion mode with 2 % formic acid in the mobile phase, presumably due to the lower proportion of acids in the anionic form under more acidic conditions. Thus, 1% formic acid in the mobile phase and acidification of the sample at pH £ 1.2 were selected as the best compromise for simultaneous analysis of anthocyanins and phenolic acids. Acidification of the wine samples at pH 1.2 followed by a 30 min delay enabled total transformation of chalcone and carbinol forms into the corresponding flavylium cations, without causing degradation of the other wine phenolics. The optimized conditions were applied for MS identification of 69 compounds from different phenolic groups present in Vranec wine

Étude de l’impédance de l’interface métal/verre

La représentation dans le plan complexe de l’admittance de cellules symétriques du type O2, métal/verre/métal, O2, permet d’étudier les caractéristiques électriques des interfaces platine/verre et or/verre en s’affranchissant de la relaxation de conduction de l’électrolyte. Les verres étudiés appartiennent aux systèmes SiO2 — Na2O et P2O5 — Na2O. Aux basses fréquences (10-4 Hz-1 kHz) les courbes expérimentales sont des arcs de cercle. L’analyse de la répartition, en fonction de la fréquence, des points expérimentaux sur ceux-ci permet de trouver une expression analytique de l’admittance. Cette expression suggère une analogie entre l’impédance de l'interface métal /verre et celle d’un circuit RC parallèle. Les valeurs des capacités d’interface et des résistances de transfert ainsi déduites dépendent de la nature du métal, de la température et de la pression partielle d’oxygène au voisinage de l’interface

HPLC analysis of hydroxycinnamic acid derivatives in Smederevka and Chardonnay wines

A reversed phase liquid chromatographic method for identification and quantification of hydroxycinnamic acid derivatives was used to analyze their content in Macedonian white wines, Smederevka and Chardonnay (Vitis vinifera L.) produced under different vinifications. Winemaking procedures for both varieties included addition of two doses of SO2 (50 and 100 mg/L) and two yeasts for fermentation (Vinalco and Levuline). Separation of the components by direct injection into HPLC was performed using reversed-phase Atlantis dC18 column, monitored at 320 nm, and the mobile phase consisted of water/formic acid (99:1; solvent A), and acetonitrile/water/formic acid (80:19:1; solvent B). The main phenolic acids present in the wines were caftaric acid (caffeoyltartaric acid) and coutaric acid (coumaroyltartaric acid). In addition, HPLC-MS analysis was carried out to confirm the identity of the separated compounds, recording the spectra in negative ion mode. In general, differences in their contents in Smederevka and Chardonnay wines were observed. Thus, Chardonnay wines were richer in phenolic acids compared to Smederevka wines. The dominant component in Chardonnay wines was trans-caftaric acid, while, trans-coutaric dominated in Smederevka wines. Regarding the influence of SO2, it was observed that wines with higher dose of SO2 contained higher levels of acids, since SO2 suppress the activity of oxidases, preventing oxidation of these readily oxidizable phenols and wine browning. The influence of the yeast on the content of phenolic acid derivatives was not significant. Principal component analysis was performed in order to check if the studied wines can be distinguished, showing separation of the samples according to the variety and SO2 doses

Influence of maceration time, SO2 and yeast strain on the content of phenolic compounds in wines from Vranec and Merlot varieties

Red wines from V. vinifera Vranec and Merlot grapes produced using a series of identical fermentation conditions for all wines (maceration times of 3, 6 and 10 days, two doses of sulphur dioxide, 30 and 70 mg/L SO2, and two yeasts for fermentation, Macedonian yeast-Vinalco and French yeast-Levuline) were subject of investigation. The concentration of phenolic acids, anthocyanins and flavan-3-ol monomers was determined by reversed-phase HPLC, while analysis of proanthocyanidins was performed by HPLC after acid-catalysed cleavage in the presence of phloroglucinol. Vranec wines were richer in anthocyanins and hydroxycinnamic acids and showed higher content of condensed tannins in comparison to the Merlot wines obtained under the same technological conditions. Vranec wines reached highest concentrations of anthocyanins after 6 days of maceration, while gradual increase of proanthocyanidins was observed both for Vranec and Merlot wines with increased pomace contact. The highest contents in acylated anthocyanins and proanthocyanidins were found in Vranec wines fermented with French yeast, macerated for 10 days. Differences in the extraction kinetics between the two yeast strains can probably be attributed to differences in their fermentation kinetics. Higher doses of SO2 resulted in increased extraction of all phenolic compounds. Statistical treatments of the data, using cluster analysis and principal component analysis, showed a clear separation of the samples, mainly according to the variety, followed by sub-grouping related to the maceration time and SO2 content

Les vignes sauvages ont-elles un intérêt ? Analyses des composés phénoliques et des propriétés antioxydantes des pellicules du raisin dans des échantillons de Vitis vinifera silvestris et Vitis vinifera Sativa

Une analyse des polyphénols totaux, des anthocyanes, des acides phénols, des stilbènes et des propriétés antioxydantes de raisins de Vitis vinifera silvestris par rapport à Vitis vinifera sativa – Pinot noir et Syrah – a révélé un potentiel intéressant sur quelques lambrusques autochtones, en particulier la première authentifiée dans les Pyrénées ariégeoises. Les détails se trouvent dans la référence ‘PAV 2014, n°11, 7-15

La pulvérisation d’éthanol à la véraison pourrait assouplir les vins en période caniculaire

Si les prévisions sont exactes, le réchauffement de la planète devrait modifier les activités viticoles dans un futur proche. Curieusement, c’est en étudiant les retards de maturité en zones fraîches du piémont pyrénéen, que nous avons peut-être découvert un traitement palliatif de certaines déviations métaboliques en période caniculaire. Les tanins des vins de 2003, issus de raisins traités à la véraison avec de l’éthanol, ont été significativement mieux appréciés que ceux des vins témoins et des vins issus de vignes traitées avec de l’éthéphon (précurseur de l’éthylène). Nous avons observé que le traitement avec de l’éthanol était associé à une baisse de la teneur en tanins des pellicules, ainsi qu’une baisse du degré de polymérisation moyen, ce qui rend les vins correspondants moins astringents. La pulvérisation d’éthanol entraîne également une augmentation du volume de la baie, ce qui pourrait avoir un effet de dilution des matières solides, intéressant les années caniculaires. Lors des deux années suivantes, non caniculaires, la pulvérisation d’éthanol n’a pas donné de différences appréciables par rapport aux vins témoins, voire une légère diminution de l’appréciation des vins par analyse sensorielle. Ces deux années là, c’est l’éthylène qui a donné les vins les mieux appréciés surtout grâce à une couleur plus soutenue. Ces études nécessitent des validations en zones chaudes ou lors d’autres périodes caniculaires. Des études d’adaptation à la canicule sur un plus long terme (variétés, méthodes culturales) restent primordiales

Effect of different yeast strains and their culture conditions on the prevention of wine model solution browning by yeast lees

Correspondance auteur: Salmon J.M. E-mail: [email protected] audienceThe purpose of this work was to examine the possible involvement of yeast membrane components in the adsorption of browning compounds from oxidized white wine. For this purpose, different yeast strains and growth conditions (aerobiosis and anaerobiosis) were tested for their ability to prevent browning of two model solutions consisting of (+)-catechin/acetaldehyde and (+)-catechin/glyoxylic acid. The obtained results showed that the effects of yeast lees are different according to the type of the studied model solution and the growth conditions that affect both the quantity and the quality of membrane sterols of the yeasts. Moreover, in vitro experiments proved that yeast membrane sterols could be likely involved in the yeast's ability to adsorb polyphenolic compounds and mainly the colorless intermediate compounds of the browning reaction