Two experimental Syrah red wines with different polyphenol contents were used to study the impact of acetaldehyde addition on olfactory perception. Free acetaldehyde levels were measured in red wine by Head Space-Gas Chromatography-Mass Spectrometry (HS-GC-MS) to determine the acetaldehyde combination levels for those wines. Significant differences were observed for both sensory threshold and acetaldehyde combination for the wines. A descriptive sensory analysis of the wines was then performed by using a trained panel and a Hierarchical-Check-All-That-Apply (HCATA) analysis of the wines with or without acetaldehyde addition. The results show that classical cited sensory descriptors for acetaldehyde (overripe apple and oxidized apple) varied significantly between the control wines and those with acetaldehyde addition. Non-acetaldehyde related descriptors (fresh vegetable, fresh flowers, cocoa, and meat juice) were also significantly impacted in the samples with increasing acetaldehyde additions. This suggests possible interactions between acetaldehyde and other volatile compounds that can create antagonistic or synergistic effects between the molecules or at the olfactory receptor level.

A Syrah red wine ageing experiment was set up during 24-months and the influence of four micro-agglomerated corks were investigated. Specific phenolic ageing markers were selected and hemi-synthesized: vitisin B, malvidin-ethyl-catechin, and epicatechin-sulfonate. A targeted quantification method of these markers was then developed and validated by using ultra-high performance liquid chromatography - triple quadrupole mass spectrometry (UHPLC-QqQ-MS) operating in MRM (Multiple Reaction Monitoring). Results showed a significant decline in native grape polyphenol levels (anthocyanins, flavanols) as ageing progresses while pyranoanthocyanins, ethyl-linked pigments, and flavanol-sulfonates content increased. The cork oxygen transfer rate emerged as a pivotal factor and had significant effects on polyphenolic concentration evolution but had no significant impact on flavanol-sulfonate formation. These results provide valuable insights into the chemical evolution ongoing during wine ageing, accentuating the pivotal role of cork stopper selection in preserving wine quality over time.

In order to obtain information on the oxidative behavior of red wines, oxygen consumption rates and electrochemical changes (cyclic voltammetry) were measured for nine red wines subject to three different accelerated ageing tests: chemical (with hydrogen peroxide), enzymatic (with laccase from Trametes versicolor), and temperature (at 60 °C). Oxidative behavior depended both on the wine sample and accelerated ageing test type. A good correlation was observed between electrochemical parameters of charges for reference/non-oxidized wines, in accordance with their antioxidant capacity, and the variation of charges after enzymatic and temperature tests, meaning that cyclic voltammetry could be used in order to predict these two oxidation tests and reflect the wine sensitivity towards respective oxidation targets. However, it was not possible to predict wine chemical oxidation test based on hydrogen peroxide from the electrochemical measurements.

Metabolic skeletal muscle (SM) dysfunction, triggered by increased oxidative stress and mitochondrial impairment, is a pivotal contributor to obesity-associated insulin resistance (IR). Addressing obesity and SM IR demands substantial lifestyle changes including regular exercise and dietary adjustments that are difficult to follow over time. This prompted exploration of alternative approaches. Grape polyphenols (GPPs) have demonstrated a positive impact on metabolism, although few studies have focused on SM. Since grape polyphenolic content and composition depend on tissue and ripening, we explored the antioxidant potential of GPPs from skin (Sk) and seeds (Sd) extracted before veraison (Bv) and at mature (M) stages, on palmitate-induced IR in primary human SM cells. Despite their important difference in polyphenol (PP) content: Sd-BvPP > Sd-MPP/Sk-BvPP > Sk-MPP, all extracts reduced lipid peroxidation by 44–60%, up-regulated the heme-oxygenase 1 protein level by 75–132% and mitochondrial activity by 47–68%. Contrary to the other extracts, which improved insulin response by 50%, Sd-BvPP did not. Our findings suggest that compounds other than stilbenoids or anthocyanin-type molecules, present only in grape Sk, could play an active role in regulating SM oxidative and metabolic stress and insulin sensitivity, paving the way for further exploration of novel bioactive compounds.

L'évolution des polyphénols des vins rouges de Syrah lors du vieillissement en bouteille implique de nombreuses réactions oxydatives ou non. Elle peut être modulée par le choix de la perméabilité à l'oxygène de l'obturateur liège utilisé. La prédiction, la caractérisation et la maîtrise via ce biais de cette évolution constitue un véritable enjeu pour la filière œnologique, notamment pour adapter l'obturateur en fonction du potentiel de vieillissement du vin. Au cours de cette thèse, deux types d'approches analytiques de suivi des transformations chimiques d'évolution des vins rouges de Syrah ont été utilisées: une approche globale non ciblée et une approche ciblée.Concernant l'approche non ciblée, des modèles de prédiction de trois tests de vieillissement accélérée des vins rouges (chimique, enzymatique et thermique) ont été établis. Ils se sont révélés précis et puissants (R² > 0.89 pour toutes les modélisations). Ces modèles, ont montré l'importance des polyphénols dans la capacité des vins à résister à l'oxydation lors du vieillissement. L'étude de métabolomique non ciblée des vins rouges de Syrah pendant le vieillissement a pu mettre en évidence des marqueurs moléculaires du vieillissement et de la perméabilité du bouchon. Ainsi, nous avons montré l'importance de molécules de type CHO (polyphénols) et CHON (peptides) dans les vins jeunes et une augmentation des composés CHO (pyranoanthocyanes), CHNOS et CHOS (réactions de sulfonation) pendant le vieillissement.Concernant l'approche ciblée, l'étude de l'impact de l'acétaldéhyde et de la composition phénolique sur la perception sensorielle des vins rouges de Syrah a été étudiée dans un premier temps. La concentration en polyphénols va impacter la combinaison de l'acétaldéhyde. De plus, selon la concentration en acétaldéhyde, des descripteurs tels que "végétal", "baies rouges" ou "pâtisseries" ont été surexprimés. Ces observations suggèrent que l'acétaldéhyde peut interagir avec des composés volatils ou non, créant ainsi des effets antagonistes ou synergiques. Dans un deuxième temps, la synthèse de trois marqueurs du vieillissement (vitisine B, malvidine-éthyl-catéchine, épicatéchine sulfonate), suivie du développement d'une méthode de quantification par UHPLC-QqQ-MS, ont été réalisés. Les cinétiques d'évolution ont montré une diminution des polyphénols natifs ainsi qu'une augmentation des marqueurs ciblés au cours du vieillissement. De plus, un effet de la perméabilité du bouchon sur ces composés (polyphénols natifs ou marqueurs) a été montré, excepté sur la formation des flavanols-sulfonates.