Preservation of antioxidant capacity and flux enhancement in concentration of red fruit juices by membrane processes

A complex membrane procedure with enhanced effectiveness for fruit juice concentration was proposed. The method was realized by an ultrafiltration-membrane osmotic distillation (UF–MOD) sequence, treating red fruit juices of great dietary value. A three-dimensional ultrafiltration membrane test equipment was applied for clarification of the raw juices. For the MOD experiments, a hollow-fiber membrane contactor was used, maintaining different bulk temperature on each side of the hydrophobic membrane supplied and using an osmotic salt solution as the receiving phase. Total antioxidant activity variation — determined by an improved version of the ABTS decolourization assay — of the final products coming from the UF–MOD sequence confirmed the assumptions of a mild fruit juice concentration method. In this installation, the concentration process could be successfully carried out, incorporating the main advances of each method used, whereas satisfying the highest consumer requirements.