Pectic polysaccharides modulate colloidal stability and astringency perception of bottle aged Cabernet Sauvignon wines

Anthocyanins, tannins, and polymeric pigments, which are formed during red wine aging, are arguably the most important phenolic constituents of red wine, because they provide color, color stability, and mouthfeel properties like astringency. The extraction of polyphenols is accompanied with the extraction of grape-derived pectic polysaccharides leading to interactions between the two compound classes during fermentation and wine aging affecting tannin and pigment precipitability. Thereby, the implications for red wine quality are dependent on the structural features of the polysaccharides. In this study, polyphenolic and pectic polysaccharide composition of commercially available Cabernet Sauvignon wines, which were subjected to forced aging, were characterized to investigate the effect of red wine aging on the interactions between polysaccharides and polyphenols. This was accomplished by removing polysaccharides from the wines and comparing the polyphenolic composition of the wines and the reconstituted polysaccharide-free wines. Descriptive sensory analysis including "overall astringency", "unripe" and "dry" was conducted on all samples to examine the implications of polysaccharide-polyphenol interactions on the astringency perception of red wines. The analyzed wines can be classified into two groups based on their colloidal stability, whereby large, neutral, and highly esterified polysaccharides promoted tannin and pigment protein precipitability and impaired the age-related formation of pigmented tannins. Small, acidic, and polar pectin fragments show a preventive effect on the precipitation of polyphenols. Sensory analysis revealed that the perception of the astringency sub-qualities "unripe" and "dry" are related to the interactions between pectic polysaccharides and polyphenols. Depending on the polysaccharide composition, the astringency of the wines increased or decreased during aging.