Deepening the understanding of polyphenol extraction mechanisms and structural drivers by assessing cell wall composition in Vitis vinifera and interspecific hybrids.

Anthocyanins and tannins constitute key organoleptic compounds in wine (contributing to color and astringency/bitterness mouthfeel, respectively) and accumulate in grape berries during ripening. In the present chapter, the scientific objectives are to: (1) assess the variability of polyphenol extraction within a set of red grape varieties with a wide range of polyphenolic potentials at both global and chemical levels, (2) investigate the mechanisms of polyphenol extraction by identify the main structural features that modulate these processes; and (3) characterize the variability of skin cell wall polysaccharide composition within a large set of varieties grouping Vitis vinifera and interspecific hybrids red grapes,. The knowledge gained will provide insights for winemakers on the extraction of key quality compounds during the maceration/fermentation process. This study was based on the detailed analysis of berry compartments (skin, flesh, seeds), musts and 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 using Vinimag Microvinification device. We analysed, five anthocyanin families in grapes skins and wines, according to their substituents (mono- and di-glucosides, acetylated, caffeoyl, and coumaroyl); five tannin categories, according to their Degree of Polymerization (DP>50; 50<20; 6<20; 5<4, and dimers-trimers) in wines, skins and seeds grapes. Additionally, six families of skin cell wall polysaccharides - cellulose, hemicellulose, homogalacturonans (HGs) and their esterification ratio, Type-I rhamnogalacturonans (RGI), Arabinogalactan Proteins (AGP), and extensins. Data were processed using a multiparametric statistical approach at a qualitative level (Principal Component Analysis) and Analysis of Variance (ANOVA).