SELECTIVE REMOVAL OF POLYPHENOLS AND BROWN COLOR IN APPLE JUICES USING PES PVP MEMBRANES IN A SINGLE-ULTRAFILTRATION PROCESS/

Home-made membranes made of polyethersulfone (PES) and polyvinylpyrrol idone (PVP) were studied and compared with commercial cellulose membra nes to reduce the amount of polyphenols and yellowish brown pigment in model solutions and apple juice. PES/PVP membranes were prepared with different pore sizes by varying the PES/PVP composition. At a pressur e of 1 bar, no water flux was obtained through the membrane without PV P. In comparison with membranes, the PES/PVP membranes were found more effective for the reduction of polyphenols, as well as discoloration. The flux was also remarkably higher. Polyphenol removal rates from th e model solution were up to 40% for a membrane prepared out of a solut ion with 22.5 wt% polymer in which the PES/PVP ratio is 3.5. Initial a dsorption and flux values could be restored easily by regenerating the membranes in 0.1 M NaOH solution for 30 min.