The Determination of Anthocyanins in Aging Red Wines: Comparison of HPLC and Spectral Methods

Total free anthocyanin contents of red table wines and port wines measured by high performance liquid chromatography (HPLC) were much lower than those estimated by the spectral method of Somers and Evans. Differences between the methods were greatest in young wines and decreased with aging. HPLC indicated that very young red table wines contained 20% to 35% polymeric pigments, and freshly-made port wines contained 17% to 69% polymeric pigments, expressed as proportions of total wine color in acid solution. A large part of the polymers were formed during skin fermentation. The findings indicate that oligomeric pigments formed during red wine aging are partially bleached by the bisulfite used in the spectral method so that anthocyanin contents calculated on this basis are too high. Progressive increases in pigment resistance to bleaching by bisulfite and decreases in color gain on polymer acidification are envisaged, as oligomeric and polymeric pigments of increasing complexity are formed during wine aging. Losses of total pigments and total free anthocyanins were logarithmic with time during port wine aging. The rate constant of anthocyanin loss as determined by HPLC is suggested as a true measure of anthocyanin aging in port wine.