Effective clarifying process of reconstituted apple juice using membrane filtration with filter-aid pretreatment

Filtration characteristics of apple juices pretreated with various filter-aids were studied to select an appropriate process for the clarification with higher permeate flux and lower membrane fouling, and for the production of high quality juice. Bentonite of 0.5% was superior filter-aid than 0.2% polyvinylpolypyrrolidone (PVPP), 0.1% activated carbon of 10–14 mesh, and the enzyme mixture of 0.03% pectinase and 0.003% amyalse in reducing juice turbidity, although PVPP was best in tannin rejection. Permeate fluxes during membrane filtration were effectively increased by filter-aids pretreatment, especially bentonite. From considering the recovery of permeate flux drop with time, ultrafiltration (MWCO 30,000) was presumed to be proper than microfiltration (0.01 μm pore size). In the quality change of apple juice, bentonite pretreatment and membrane filtrations improved color without the deteriorational changes of pH, total acidity, and the contents of total sugar, organic acid and Vitamin C, which are important quality index in fruit juice. Finally, ultrafiltration with bentonite pretreatment was optimal process for the effective clarification and the high quality of apple juice.