Effects of Grape Seed Proanthocyanidins with Different Polymerization Degrees on the Phenolic Compounds and Sensory Quality of Cabernet Sauvignon Wine During Bottle Aging

Wine phenolic composition is strongly influenced by tannin structure, yet how the polymerization degree of exogenous proanthocyanidins modulates wine quality during aging remains unclear. This study investigated the effects of adding grape seed proanthocyanidins (GSP) with different mean degrees of polymerization (mDP 4.63, 3.29, and 1.31) to Cabernet Sauvignon wine by analyzing phenolic compounds, tannin structure, anthocyanin components, CIELAB color parameters, and astringency over 6 months of bottle aging. Low-mDP GSP (rich in galloylated monomers) provided the biggest initial phenolic boost, while high-mDP GSP (dominated by non-galloylated units) sustained tannin enrichment throughout aging. Low-mDP GSP accelerated tannin maturation and color evolution toward aged wine characteristics, with Mv-3-Coglu identified as a key precursor for brick-red hue development. Sensory evaluation revealed that high-mDP GSP enhanced coarse and drying astringency, whereas low-mDP GSP promoted velvety mouthfeel. These findings establish that GSP polymerization degree critically determines phenolic evolution, color stability, and mouthfeel during bottle aging, providing a scientific basis for selecting structure-specific proanthocyanidins to achieve targeted wine quality outcomes.