Biochemical properties of the fresh and frozen black currants and juices

Thirteen black currant varieties (Ribes nigrum L.) cultured in Serbia were characterized for their pomological properties and chemical composition (total phenolics, total anthocyanins, anthocyanin aglycones, sugars, and vitamin C). The average amount of vitamin C varied from 122.4 to 193.2 mg/100 g fresh weight (FW), while concentration of invert sugars ranged from 6.3% to 11.1%. The highest amounts of total phenolics and anthocyanins were detected in variety Ometa (278.9 mg of gallic acid equivalents per 100 g of FW [mg GAE/100 g FW] and 135.4 mg/100 g, respectively). Quantitative analyses of anthocyanin aglycones in berries were performed using high-performance liquid chromatography, and delphinidin was found to be dominant compound in 11 varieties. Total phenolics and anthocyanins contents decreased during the processing of berry fruits to juices, and the reduction of anthocyanins was more pronounced, 12%-80%. The radical scavenging activity of black currant juices was investigated by 1,1-diphenyl-2-picrylhydrazyl, and the IC(50) value ranged from 1.9 to 4.0 mg/mL. Our results also showed that freezing as a way of preservation and storage could save important phytochemicals and health benefits of berries and berry juices. The amount of total phenolics in berries increased during 1 year of storage by 46.09%-171.76% and in juices by even 107.58%, while the amount of total anthocyanins in berries and juices decrease by 5.63%-52.76% and 13.04%-36.82%, respectively.