Varietal differentiation of grapes cv. 'Vranac', 'Kratosija' and 'Cabernet Sauvignon' from Montenegro according to their polyphenolic composition

This paper presents the results of investigations into the polyphenolic profile of grapes from the red grape varieties 'Vranac', 'Kratosija' and 'Cabernet Sauvignon' grown in the Montenegrin wine region. Using an RP-HPLC method the composition of anthocyanins and hydroxycinnamic acids (HCA) in the fresh grapes was analysed. Results of the analysis of anthocyanins show that the Montenegrin grape varieties have the same order of the relative concentration of monoglucosid, non-acylated anthocyanins: Mv-3-gl > Pn-3-gl > Pt-3-gl > Dp-3-gl > Cy-3-gl, but with a different relative amount of anthocyanins in 'Vranac' and 'Kratosija'. The concentration of p-coumarylated derivates was higher than the concentration of acetylated ones in 'Vranac' and 'Kratosija'. In contrary, grapes of the variety 'Cabernet Sauvignon' have a relatively high amount of acylated derivates and more acetylated anthocyanins than p-coumarylated ones. Therefore the ratio between acetylated and coumarylated anthocyanins varied widely among the varieties: 'Vranac' 0.46, 'Kratosija' 0.15 and 'Cabernet Sauvignon' 2.07. The content of total anthocyanins varied significantly between the examined varieties: 'Vranac' (1360 mg/kg), 'Kratosija' (591 mg/kg) and 'Cabernet Sauvignon' (1116 mg/kg). The studied varieties were characterised by differences in the HCA profile (relative content of caftaric/coutaric/fertaric acid): 69/21/11 for 'Vranac'. 75/11/14 for 'Kratosija' and 73/20/7 for 'Cabernet Sauvignon'. The values for trans-coutaric/trans-caftaric ratio varied significantly between the varieties and amounted to 0.236 for 'Vranac', 0.107 for 'Kratosija' and 0.213 for 'Cabernet Sauvignon'. The total HCA contents in the skin and pulp were different in the examined varieties. Principal component analysis showed that each studied variety had a unique profile compared to the content of anthocyanins and hydroxycinnamic acids. These properties are reliable criteria for varietal identification.