Same Yeast, Different Wines: Impact of different Grape variety Must Composition on Fermentation Dynamics and Wine Composition

Polyphenols are major quality determinants in red wines, extracted during skin maceration as previously studied in chapter 3. However, during red winemaking, maceration and alcoholic fermentation are concomitant processes. While much is known about how yeasts drive fermentation, the reciprocal impact of polyphenolic diversity on Saccharomyces Cerevisiae metabolism remains poorly characterized. This study investigates: (1) Metabolic Interactions: how varietal polyphenolic profiles, affect the fermentative behaviour of Saccharomyces cerevisiae (fermentation kinetics, primary and secondary metabolisms); (2) Polysaccharide Modulation: how the previously described modulation of polyphenol extraction by cell wall polysaccharides indirectly influences yeast activity. This study was based on the accurate analysis of polyphenolic distribution (anthocyanin and tannins) in wines of 32 varieties: 14 Vitis vinifera varieties (Alicante, Cabernet Sauvignon, Carignan, Cinsault, Fer Servadou, Grenache, Petit Verdot, Pinot, Syrah, Tannat, Nielluccio, Pinotage, Touriga Nacional, Xinomavro); and 18 disease-tolerant, interspecific hybrid varieties which possess resistance genes to the principal diseases (downy and powdery mildew), mixing different hybridization programs (1212N, 3160-27-4N, 3176N, 3322-226N, 3328-168N, G14, Artaban, Cabernet Cantor, Cabernet Volos, Monarch, Merlot Khorus, Pinotin, Prior, Sirano, Vidoc, Clinton, Herbemont, Isabelle), harvested in the 2023 vintage. Wines were vinified under standardized microvinification conditions. S.cerevisiae fermentative behaviour was assessed by (1) on-line monitoring of fermentation (CO2 release); (2) analysis of primary metabolism indicators (central carbon metabolism CCM): glycerol, acetate and succinate; and (3) secondary metabolism through fermentative aroma contents (higher alcohols, ethyl esters and esters acetates). Finally, cell wall polysaccharides were analysed with Comprehensive Microarray Polysaccharide Profiling (CoMPP) and grouped in 6 families: cellulose, hemicellulose, homogalacturonans (HGs) and their esterification ratio, Type-I rhamnogalacturonans (RGI), Arabinogalactan Proteins (AGP), and extensins. The data was treated using a multiparametric statistical approach, including Principal Component Analysis (PCA) as well as Analysis of Variance (ANOVA).