Cédric Saucier

Grape Variety Effect on Proanthocyanidin Composition and Sensory Perception of Skin and Seed Tannin Extracts from Bordeaux Wine Grapes (Cabernet Sauvignon and Merlot) for Two Consecutive Vintages (2006 and 2007)

Grape variety [Cabernet Sauvignon (CS) and Merlot (M)] effect on the proanthocyanidin composition and sensory perception of wine grapes from Bordeaux vineyards for two successive vintages (2006 and 2007) is reported. The flavan-3-ol monomers [(+)-catechin = C, (-)-epicatechin = EC, (-)-epicatechin-O-gallatte = ECG] and the proanthocyanidin oligomers [dimers B1, B2, B3, and B4 and trimer Cat-Cat-Epi (T)] in grape seed and skin tannin extracts were identified and quantified at harvest. Proanthocyanidin subunit compositions, percentage of galloylation (%G), and percentage of prodelphinidins (%P) as well as mean degree of polymerization (mDP) of the proanthocyanidin fraction were determined. Sensory analysis concerning the astringency and bitterness intensity of the proanthocyanidins of skin and seed tannin extracts was also performed. The results showed that proanthocyanidin composition can be greatly affected by grape variety. For both vintages between CS and M, significant differences were found on mDP (p < 0.05) in seed tannin extracts, whereas in skin tannin extracts, significant differences were observed for %G and %P (p < 0.05). Sensory analysis showed that grape variety influenced neither astringency nor bitterness intensity perception for both skin and seed tannin extracts for the two successive vintages studied. A positive correlation was found between astringency intensity, mDP, and B3 content in skin tannin extracts.

Impact of Oxygen Dissolved at Bottling and Transmitted through Closures on the Composition and Sensory Properties of a Sauvignon Blanc Wine during Bottle Storage

This work outlines the results from an investigation to determine the effect of the oxygen dissolved at bottling and the specific oxygen barrier properties of commercially available closures on the composition, color and sensory properties of a Bordeaux Sauvignon Blanc wine during two years of storage. The importance of oxygen for wine development after bottling was also assessed using an airtight bottle ampule. Wines were assessed for the antioxidants (SO(2) and ascorbic acid), varietal thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol), hydrogen sulfide and sotolon content, and color throughout 24 months of storage. In addition, the aroma and palate properties of wines were also assessed. The combination of oxygen dissolved at bottling and the oxygen transferred through closures has a significant effect on Sauvignon Blanc development after bottling. Wines highly exposed to oxygen at bottling and those sealed with a synthetic, Nomacorc classic closure, highly permeable to oxygen, were relatively oxidized in aroma, brown in color, and low in antioxidants and volatile compounds compared to wines sealed with other closures. Conversely, wines sealed under more airtight conditions, bottle ampule and screw cap Saran-tin, have the slowest rate of browning, and displayed the greatest contents of antioxidants and varietal thiols, but also high levels of H(2)S, which were responsible for the reduced dominating character found in these wines, while wines sealed with cork stoppers and screw cap Saranex presented negligible reduced and oxidized characters.

(+)-Catechin—acetaldehyde condensation products in relation to wine-ageing

Abstract Dimers resulting from acetaldehyde-flavanol condensation were studied in an acidic hydroalcoholic medium (12% ethanol pH 3.2) in order to simulate the conditions of wine tannin-transformation during the wine-ageing process. One of the dimers was isolated after hemisynthesis and studied by mass spectrometry, NMR and molecular mechanics. Mass spectrometric analysis was in accordance with a dimeric structure with a CH-CH 3 linkage. NMR showed the presence of a 6–8 (ethane-1,1-diyl)di(+)-catechin. The carbon atoms, C-6 and C-8, involved in the linkage, have, an asymmetric conformation, with the two catechols in an equatorial position.

Effect of Micro-oxygenation on Color and Anthocyanin-Related Compounds of Wines with Different Phenolic Contents

Several factors may affect the results obtained when micro-oxygenation is applied to red wines, the most important being the moment of application, the doses of oxygen, and the wine phenolic characteristics. In this study, three red wines, made from Vitis vinifera var. Monastrell (2005 vintage) and with different phenolic characteristics, were micro-oxygenated to determine as to how this technique affected the formation of new pigments in the wines and their chromatic characteristics. The results indicated that the different wines were differently affected by micro-oxygenation. In general, the micro-oxygenated wines had a higher percentage of new anthocyanin-derived pigments, being that this formation is more favored in the wines with the highest total phenol content. These compounds, in turn, significantly increased the wine color intensity. The wine with the lowest phenolic content was less influenced by micro-oxygenation, and the observed evolution in the degree of polymerization of tannins suggested that it might have suffered overoxygenation.

High Performance Thin Layer Chromatography (HPTLC) Analysis of Red Wine Pigments

An HPTLC method has been developed to give qualitative and quantitative information on red wine pigments. The samples are prepared by solid-phase extraction (SPE) on C18 cartridges. Analytical determination is done by chromatography on C18 silica gel plates with isocratic elution with methanol—water—trifluoracetic acid, 55 + 45 + 1 (v/v). This method leads to the clear separation of the three classes of Vitis vinifera anthocyanins with good statistical repeatability and reproducibility for wines of different vintages. It also enables evaluation of the amount of polymeric pigments in red wines.

Rosé Wine Fining Using Polyvinylpolypyrrolidone: Colorimetry, Targeted Polyphenomics, and Molecular Dynamics Simulations

Polyvinylpolypyrrolidone (PVPP) is a fining agent polymer used in winemaking to adjust rosé wine color and to prevent organoleptic degradations by reducing polyphenol content. The impact of this polymer on color parameters and polyphenols of rosé wines was investigated, and the binding specificity of polyphenols toward PVPP was determined. Color measured by colorimetry decreased after treatment, thus confirming the adsorption of anthocyanins and other pigments. Phenolic composition was determined before and after fining by targeted polyphenomics (Ultra Performance Liquid Chromatography (UPLC)-Electrospray Ionization(ESI)-Mass Spectrometry (MS/MS)). MS analysis showed adsorption differences among polyphenol families. Flavonols (42%) and flavanols (64%) were the most affected. Anthocyanins were not strongly adsorbed on average (12%), but a specific adsorption of coumaroylated anthocyanins was observed (37%). Intermolecular interactions were also studied using molecular dynamics simulations. Relative adsorptions of flavanols were correlated with the calculated interaction energies. The specific affinity of coumaroylated anthocyanins toward PVPP was also well explained by the molecular modeling.