Clarification and concentration of pomegranate juice (Punica granatum L.) using membrane processes

The production of concentrated pomegranate juice was investigated by using a two-step membrane process based on: (1) a clarification step of the fresh non- depectinized juice performed by hollow-fiber ultrafiltration (UF) membranes; (2) a concentration step of the clarified juice by using an osmotic distillation (OD) apparatus. Both processes were performed at ambient temperature (25 ± 2°C) producing a clear juice and a concentrated juice with a total soluble solids (TSS) content of 162 g kg-1 and 520 g kg-1, respectively. The performance of UF and OD operations was evaluated in terms of productivity (permeate and evaporation fluxes) and quality of the processed juice. Suspended solids were completely removed in the clarification step, while soluble solids and organic acids were recovered in the permeate stream of the UF process. Rejections of the UF membrane towards polyphenols and anthocyanins were of 16.5% and 11.7%, respectively. The antioxidant activity of pomegranate aril juice, attributed to a great extent to total phenols and anthocyanins content, was efficiently preserved during the concentration step independently on the achieved level of total soluble solids. An integrated membrane process scheme for the production of concentrated pomegranate juice with potential applications for food, pharmaceutical and cosmetic sectors was proposed.