Selective removal of polyphenols and brown colour in apple juices using PES/PVP membranes in a single-ultrafiltration process

Home-made membranes made of polyethersulfone (PES) and polyvinylpyrrolidone (PVP) were studied and compared with commercial cellulose membranes 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 pressure of 1 bar, no water flux was obtained through the membrane without PVP. 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 the model solution were up to 40% for a membrane prepared out of a solution with 22.5 wt% polymer in which the PES/PVP ratio is 3.5. Initial adsorption and flux values could be restored easily by regenerating the membranes in 0.1 M NaOH solution for 30 min.