Pilot-plant-scale test of clarification and sterilization of apple juice using ultrafiltration ceramic membranes

Raw depectinized apple juice was clarified and sterilized in a cross-flow pilot-plant-scale ultrafiltration system using ceramic tubular membranes (MEMBRALOX^?, Pall) with mean pore size of 100 nm. The experiment showed that the optimum operation conditions were as follows: the transmembrane pressure was 0.85×10⁵ Pa, the temperature was 50℃, and the feed flow velocity was 5 m/s. The flux recovery rate could be bept at 98% with the mixed solution of 0.5% hypochlorite sodium solution and 4% NaOH solution as the cleaning agent. Analytical results showed that: suspended solids and large molecules could be mostly removed, but pH, acidity, sugar and soluble solid content of the juices didn't change significantly. The bacteria challenge tests and the storage tests testified the asepsis state and biological stability of the filtrated fruit juice. Therefore, the cross-flow system equipped with the 100 nm ceramic ultrafiltration membrane had a great potential to the commercial prospect.