Development of wine colour and non-bleachable pigments during the fermentation and ageing of (Vitis vinifera L. cv.) Cabernet Sauvignon wines differing in anthocyanin and tannin concentration

Non-bleachable (SO₂-resistant) pigment formation in wine is related to the concentration of grape-derived anthocyanin and tannin, but their relative impact on the formation and composition of SO₂-resistant pigments is poorly understood. Colour development during fermentation and ageing was analysed in two wines produced from grape batches with different anthocyanin and tannin concentrations. Higher anthocyanin and tannin concentrations extracted during fermentation were associated with increased wine colour density, total SO₂-resistant pigments and SO₂-resistant polymeric pigment. During ageing, wine colour density decreased, but differences between the respective wine treatments were retained. Wine tannin concentration was unchanged with age, anthocyanin decreased, and SO₂-resistant pigments increased. Fractionation of wines indicated that SO₂-resistant pigments in both polymeric and non-polymeric forms increased with ageing. Increases in tannin pigmentation over time were associated with decreased tannin molecular mass, reflecting the conversion of tannin to lower molecular mass pigmented polymers. The formation of polymeric pigment during ageing was related to the initial wine tannin concentration. However, non-polymeric forms of SO₂-resistant pigments increased to a greater extent in wines with higher initial anthocyanin and tannin concentrations. The data suggests that both polymeric and low molecular mass anthocyanin derivatives are important for stable wine colour development.