Interactions of Vitis vinifera L. cv. Pinot Noir grape anthocyanins with seed proanthocyanidins and their effect on wine color and phenolic composition

The initial concentration of anthocyanin and proanthocyanidin in wine affects the development of SO₂-resistant pigments, as well as color and non-color contributing polymeric fractions. However, the effect of extracted monomeric Pinot Noir (Vitis vinifera L. cv.) grape anthocyanins with seed proanthocyanidins are poorly studied. In model ferments, the reaction of purified Vitis vinifera L. cv. Pinot noir monomeric anthocyanins with seed proanthocyanidins extract were investigated at high and low concentrations of each reactant. During wine aging, monomeric anthocyanins decreased whereas SO₂-resistant pigments increased. Higher anthocyanin concentrations retained more soluble tannins in model ferments during aging, while those with higher anthocyanin and lower proanthocyanidin concentrations had the highest MCP-tannin concentration in model ferments. HPLC analysis showed that the color contributing polymeric fractions are dependent upon the initial concentration of anthocyanin/proanthocyanidin ratios and more inclined towards high anthocyanin/low proanthocyanidin concentrations. Wine color parameters were measured in the form of L*, a*, b*, C (chroma) and H (hue) values and showed a decrease in hue and chroma in model wines after aging. The color data supported the HPLC findings that the initial anthocyanin/proanthocyanidin ratio was critical for the establishment of a color contributing polymeric fractions and stable deep red color in wines