Michael Jourdes

Cabernet sauvignon red wine astringency quality control by tannin characterization and polymerization during storage

Cabernet Sauvignon wine grape variety is an emblematic cultivar of Bordeaux winegrowing region. Twenty-three vintages of Cabernet Sauvignon wines from chateau Mouton Rothschild were studied using chemical and sensory analysis. Total phenolic compounds, total anthocyanins, total tannins, hue, CI (colour intensity), titratable acidity, ethanol level and pH were evaluated. Percentage of galloylation (%G), of prodelphinidins (%P) as well as mean degree of polymerization (mDP) were also determined. Sensory analysis concerning astringency intensity using a 0–7 point scale was performed in parallel. Correlations between bottle wine ageing and mDP and astringency were obtained. Increasing age gave lower scores in astringency intensity (R2xa0=xa00.598, pxa0=xa00.000) and inferior mDP values (R2xa0=xa00.851, pxa0=xa00.000). In addition, we evidenced that mDP is an analytical parameter for estimating astringency (R2xa0=xa00.556, pxa0=xa00.000) in red CS (Cabernet Sauvignon) wine from Pauillac denomination.

Identification, amounts, and kinetics of extraction of C-glucosidic ellagitannins during wine aging in oak barrels or in stainless steel tanks with oak chips

The C-glucosidic ellagitannins are found in wine as a result of its aging in oak barrels or in stainless steel tanks with oak chips. Once dissolved in this slightly acidic solution, the C-glucosidic ellagitannins vescalagin can react with nucleophilic entities present in red wine, such as ethanol, catechin, and epicatechin, to generate condensed hybrid products such as the β-1-O-ethylvescalagin and the flavano-ellagitannins (acutissimin A/B and epiacutissimin A/B), respectively. During this study, we first monitored the extraction kinetic and the evolution of the eight major oak-derived C-glucosidic ellagitannins in red wines aged in oak barrels or in stainless steel tank with oak chips. Their extraction rates appeared to be faster during red wine aging in stainless steel tanks with oak chips. However, their overall concentrations in wines were found higher in the wine aged in barrels. The formation rates of the vescalagin-coupled derivatives were also estimated for the first time under both red wine aging conditions (i.e., oak barrels or stainless steel tanks with oak chips). As observed for the oak-native C-glucosidic ellagitannins, the concentrations of these vescalagin derivatives were higher in the red wine aged in oak barrels than in stainless steel tanks with oak chips. Despite these differences, their relative composition was similar under both red wine aging conditions. Finally, the impact of the oak chips size and toasting level on the C-glucosidic ellagitannins concentration in wine was also investigated.

A preliminary characterization of Aglianico (Vitis vinifera L. cv.) grape proanthocyanidins and evaluation of their reactivity towards salivary proteins.

The flavan-3-ol and proanthocyanidin composition of Aglianico seeds and skins were for the first time determined by HPLC-MS in comparison with the international grapes Merlot and Cabernet Sauvignon. Monomers [(+)-catechin C, (-)-epicatechin EC, (-)-epicatechin-3-O-gallate, ECG] and oligomers [B1, B2, B3, B4 dimers and trimer C1] were identified and quantified in grape extracts. In order to evaluate the reactivity towards salivary proteins of model wine solutions of seeds and skins monomeric/oligomeric and polymeric fractions, the Saliva Precipitation Index (SPI) was carried out. Fractions were also analyzed for their mean degree of polymerization (mDP), percentage of galloylation (%G) and of prodelphinidin (%P) by phloroglucinolysis. Aglianico was the most effective in precipitating proteins than Merlot and Cabernet Sauvignon, mainly for the high percentage of galloylation of grape fractions. The mDP and the percentage of ECG in terminal units resulted to significantly contribute to the precipitation of salivary proteins by grape proanthocyanidins.

Rapid and simple method for the quantification of flavan-3-ols in wine

A rapid and simple reverse-phase liquid chromatography coupled with fluorescence detection is proposed for the rapid simultaneous analysis of three monomeric flavanols and six procyanidins (i.e., five dimers and one trimer) in wine. Good resolution and low detection limits were obtained for (+)-catechin, (−)-epicatechin, (−)-epicatechin 3-O-gallate, dimers B1, B2, B3, B4 and B2-gallate and trimer C1. The method has been validated for linearity, precision and accuracy. Good performances in terms of selectivity and sensitivity have been also achieved. Moreover, new fluorimetric method has been developed in order to achieve the quantification of (−)-epicatechin 3-O-gallate and procyanidin B2-gallate by fluorescence detection.

Chip electrophoresis as a novel approach to measure the polyphenols reactivity toward human saliva

Saliva is a biological fluid with a multifunctional role that makes it interesting in terms of research and diagnostic possibilities. In food research, human saliva represented a useful tool by which we measure the tactile sensation elicited by polyphenol‐rich beverages called astringency. A method based on SDS‐PAGE analysis of saliva before and after the binding reaction with wine polyphenols has been successfully used in previous studies for measuring wine astringency by means of the saliva precipitation index. In this work, chip electrophoresis was used alternatively to SDS‐PAGE and results were compared. Chip electrophoresis provides a very good reproducibility for wine and grape astringency. Moreover, this approach is much faster than the conventional SDS‐PAGE method requiring several hours for an analysis. Another advantage over traditional gel is lower sample and reagent volume requirements, as well as the lower and less toxic wastes, contributing benefits to health and environment. The application of this novel method allowed, using the principal component analysis, to distinguish grapes and wines according to the saliva precipitation index and structural characteristics determined by the phoroglucinolysis analysis.

Metabolic and RNA profiling elucidates proanthocyanidins accumulation in Aglianico grape

Aglianico grapes are known for their high content of proanthocyanidins (PAs), which are responsible for the astringency of wines derived from this cultivar. However, the accumulation of PAs and their genetic control during berry development remain largely unexplored. This work aimed to monitor astringency-causing PAs in Aglianico berries and correlate them with the expression of 14 key genes. Berries were collected during ripening and dissected in skins and seeds. PAs were fractionated and the content of total phenolics, flavans, anthocyanins, tannins reactive towards salivary proteins and tannin structural composition were evaluated. The results provided evidence that PAs were more abundant in seeds than in skins as expected, with differences in the structural composition between tissues, which did not varied during ripening. Expression analysis showed that Aglianico is able to accumulate polyphenols due to its ability to modulate key genes in a tissue-specific manner.

Erratum to: Rapid and simple method for the quantification of flavan-3-ols in wine

M. A. Silva I. Ky M. Jourdes P.-L. Teissedre (&) Unite de Recherche Oenologie, EA 4577, USC 1219 INRA, Faculte d’Oenologie, Institut des Sciences de la Vigne et du Vin, Universite Bordeaux Segalen, 210 chemin de Leysotte, CS 50008, 33882 Villenave d’Ornon Cedex, France e-mail: p.teissedre@u-bordeaux2.fr Table 2 Validation parameters determined for the proanthocyanidins liquid chromatography coupled with fluorescence detection method