Features of Determination of Dihydroxylated Anthocyanins in Wines

This work present the results of the study of the complexation of Al3+ with anthocyanins of red wines (cyanidin-3-O-glucoside and delphinidin-3-O-glucoside). By using the examples of delphinidin-3-O-glucoside and pelargonidine-3-O-glucoside, it is shown that only dihydroxylated forms of anthocyanins are capable of forming a complex with Al3+, while non-hydroxylated anthocyanins form no similar complexes. In the selected conditions, the total contents of dihydroxylated anthocyanins in wines made from different grape varieties (calculated for cyanidin-3-O-glucoside) are determined, which vary for red wines from 8.7 mg/dm(3) for Cabernet (Kuban Vine) to 27.1 mg/dm(3) for wine made from the Saperavi grape variety. The highest contents of these forms of anthocyanins have been obtained for wines made from the grape varieties of Saperavi, Krasnostop, and Cabernet. To determine the relationship between dihydroxylated anthocyanins and monomeric forms, the total content of monomeric forms of anthocyanins in the studied wines is determined by pH-differential spectrophotometry. It has been found that the share of these forms of anthocyanins in the total content of monomeric forms was 9-14%. A high degree of correlation between the total contents of dihydroxylated and monomeric forms of anthocyanins has been obtained (r(c) = 0.98; r(t) = 0.63 for n = 10; alpha = 0.05). The relationships between the total contents of anthocyanins (both monomeric and dihydroxylated) and spectral characteristics (color intensity and nuance) have been determined as is recommended by the OIV (International Organization of Vine and Wine) to estimate the quality of wines. It is shown that wines with the highest content of dihydroxylated and monomeric forms of anthocyanins are characterized by higher color intensities.