Reverse osmosis process for the concentration of black currant juice was carried using AFC-99 tubular membrane at 30 degrees C and 45 bar. The contents of selected flavonols and anthocyanins were analyzed after centrifugation; enzyme treatment by Panzym Super E and by Rohapect berry followed by centrifugation; and ultrafiltration black currant juices and juice concentrates. The total soluble solid (TSS) content of the juices increased from the initial 17.6-17.9 degrees Brix to 24-24.8 degrees Brix in the case of the centrifuged juice in the concentration process. Similarly, it increased from 14.5-15.5 degrees Brix to 23.1-23.4 degrees Brix for the Panzym Super E treated juice, and from 16.1-16.9 degrees Brix to 22.5-23.1 degrees Brix for the Rohapect berry treated black currant juices. The ultrafiltered juice had the lowest initial TSS content between 14.1 and 14.9 degrees Brix and it increased to 22.1-23.1 degrees Brix. The average permeate fluxes during the concentration process were 7.3 L m(-2) h(-1) for the centrifuged juice, 11.9 L m(-2) h(-1) for the Panzym Super E treated juice, 9.2 and 13.1 L m(-2) h(-1) for the Rohapect berry treated and ultrafiltered juice, respectively. Analysis indicated that the enzymatic treatment resulted in the increase of anthocyanin and flavonol content of the juices. The centrifugation process decreased the amount of anthocyanins and flavonols to some extent. The juice clarified by ultrafiltration had significantly lower concentrations of anthocyanins and flavonols, while the juices treated by Panzym Super E had the highest levels of these flavonoids. This study recommends enzymatic pre-treatment by Panzym Super E, since it improves the permeate flux in reverse osmosis during the concentration process, and results in a juice concentrates highest in anthocyanins and fiavonols. (C) 2010 Elsevier Ltd. All rights reserved.