Solute and Enzyme Recoveries in Apple Juice Clarification using Ultrafiltration

Enzyme treated apple juices, obtained after pressing on a commercial processing line, were clarified by UF using a plate and frame system. The 50,000 molecular weight cut-off membranes operated at 50°C and 5 bar pressure yielded average recovery of 99.6% and 99.3% soluble solids and titratable acids, respectively, in the permeate and rejected 36.3% of the residual pectinase activity which was available for possible reuse. Proper membrane cleaning to maintain high flux was very important in UF clarification; a 1% Ultrasil solution was more efficient than a 0.1% NaOH solution and reduced need for centrifugation and/ or vacuum filtration prior to UF.