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.

Biochemical properties of red currant varieties in relation to storage.

Eleven red currant varieties (Ribes rubrum L.) cultured in Serbia were evaluated for some of their biochemical properties such as total phenolics, anthocyanins, ascorbic acid, invert sugar, soluble solid content, and acidity. The average amount of ascorbic acid varied from 50.5-71.6 mg/100 g FW, while concentration of invert sugars ranged from 6.0%-9.0%. The highest amounts of total phenolics and anthocyanins were detected in variety Redpoll (153.4 mg GAE/100 g FW and 19.3 mg/100 g, respectively). Red currants were processed to juice, and the phenolic and anthocyanin contents changed as a result of processing. Berries and juices were long-term stored at -18 °C and changes in phytochemicals were monitored. In berries, storage caused the decrease of ascorbic acid content up to 49%, and a general reduction of total phenolics was also noticed. In juices, total phenolics content increased after one year of storage. In both berries and juices total anthocyanins increased during storage by up to 85% and 50%, respectively. This study demonstrates that certain varieties, namely Redpoll, Jonkheer and London Market are good source of phytochemicals, retaining the nutritional value during processing and storage.