Disentangling Variety and Terroir Effects on Red Wine Chemical Composition: A Subregional Analysis of Three Grape Cultivars Across Occitanie Vineyards

Understanding the respective roles of grape variety and terroir in wine composition remains a key issue in viticulture, particularly at the subregional scale. Furthermore, in our study, all the selected varieties (32) could not be harvested from the same location. To ensure the methodological robustness of this study, it is mandatory to establish the extent of the terroir effect before accurately interpreting the results related to varietal differences. This study investigated the influence of variety and harvest location on red wine composition using three cultivars, Artaban (hybrid), Cabernet Sauvignon, and Syrah (Vitis Vinifera), grown in three terroirs of Occitanie in France (La Clape, Domaine de Cazes, and Ouveillan), and vinified under standardized microvinification conditions. We analysed the following components: anthocyanins and tannins (at a global level and differentially according to anthocyanin substitutions and tannin degree of Polymerization DP), varietal thiols in wines (3SH, 3SHA) and their precursors in must before fermentation (G3SH, Cys3SH, γ-GluCys3SH, CysGly3SH, NAC3SH, G4SMP, Cys4SMP), and wine polysaccharides (mannoproteins (MPs), Polysaccharides rich in Arabinose and Galactose (PRAG) and Type-II rhamnogalacturonan (RGII)). The data was analysed using a multiparametric statistical approach including Principal Component Analysis (PCA) as well as Analysis of Variance (ANOVA) with two factors: variety and harvest location.