Influence of processing parameters on permeate flow and retention of aroma and phenolic compounds in chokeberry juice concentrated by reverse osmosis

Reverse osmosis (RO) concentration of chokeberry juice, a rich source of polyphenols, at three different pressures (45, 50 and 55 bar) and two temperature regimes (with cooling and without cooling of the retentate) was studied. Concentration was carried out on a laboratory membrane unit with plates and frames on composite Alfa Laval membranes RO98pHt. Juice was concentrated till 24.9% of total soluble solids content (TSSC). The permeate flow highly depended on processing parameters and varied from 15.19 +/- 3.22 L/m(2)h at the beginning to 8.00 +/- 2.21 L/m(2)h at the end of processes. Total phenolic compounds (4 anthocyanins, 2 flavonols and 2 phenolic acids) were determined by high performance liquid chromatography (HPLC). Twenty four volatile compounds were identified by gas chromatography with mass spectrometry (GC-MS) in chokeberry juice and concentrates. Processes at 50 and 55 bar with cooling proved to be the best in terms of chokeberry aroma, antioxidant activity and total phenolic compounds retention.