Single strength apple juices (10° Brix) were processed by reverse osmosis to 20-25°Brix, primarily at 20°C. A pilot scale plate and frame UF-RO system equipped with cellulose acetate (CA) membranes, CA-865 and/or CA-990, or high resistance (HR) membranes, HR-95 and/or HR-98, was operated at pressures of 35-45 bar. At 45 bar, the larger pore-sized CA-865 possessed the highest processing capacity of 26.9 L/m2/hr (from 10°Brix to 20°Brix) and concentration limits of 35° Brix, but had low recovery of solutes and flavor volatiles. The HR-95 and HR-98 had similar processing capacities of 15-16 L/m2/hr and concentration limits of 20-25° Brix at 45 bar. The recoveries of 97% solutes and 87% apple flavor volatiles were obtained using either the HR-95 or the HR-98.