Biochemical markers of grape berry textural maturity and their implications for compound extractability and wine physico-chemical stability

Abstract

In the context of climate change, grape ripening is increasingly suffering a decoupling between technological, phenolic, and textural maturity. Textural maturity is closely associated with the structural and biochemical evolution of skin cell walls, whose composition and macromolecular organization determine the extractability of oenologically relevant compounds during winemaking (1,2). The aim of this study is to investigate the evolution of grape skin cell wall composition throughout ripening and to identify biochemical markers capable of predicting the extractability of polysaccharides and phenolic compounds in wine, with direct consequences for wine quality and physicochemical stability over time. Cabernet Sauvignon grapes were harvested at different stages of technological maturity from véraison onwards within a selected vineyard plot over two consecutive vintages. Skin degradation was assessed through mechanical measurements (penetrometry) and by monitoring pectolytic enzymatic activities involved in cell wall remodeling. Cell wall composition was first characterized in isolated grape skins using chemical approaches, including polysaccharide analysis by size-exclusion chromatography (SEC) and phenolic profiling by high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS). The extractability of polysaccharides and phenolic compounds of oenological interest was subsequently assessed in wines produced by controlled microvinifications performed on the same grape batches. Wine samples were analysed using SEC for polysaccharide profiling and HPLC–MS for phenolic characterization. Results demonstrate that ripening-related modifications in skin cell wall composition and organization significantly modulate the extractability of macromolecules and phenolic compounds into wine, thereby influencing its structural balance and stability. These preliminary studies must be confirmed to identify robust indicators of textural maturity as predictive tools to guide harvest decisions and optimize vinification strategies according to targeted wine styles, while offering opportunities to reduce oenological inputs.

References

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2. Vidal S, Williams P, Doco T, Moutounet M, Pellerin P. (2003). The polysaccharides of red wine: total fractionation and characterization. Carbohydr Polym.54(4):439‑47.