Clarification of pomegranate juice (punica granatum L.) by hollow fibre membranes: Analyses of membrane fouling and performance

BACKGROUND:Membrane based clarification of fruit juiceshas becomeapopular unitoperation inmodernfruit juice processing industries. In this work modified poly(ether ether ketone) and polysulfone hollow fibre membranes, with high water flux and molecular weight cut-off, were prepared via the dry-wet spinning technique through the phase inversion process and characterized by scanning electron microscopy,water permeability and dextran rejection. The preparedmembraneswere used to clarify pomegranate juice with the aim to preserve the phenolic fraction and to obtain high permeation fluxes. The effect of transmembrane pressure and axial feed velocity on permeation flux and hydraulic resistances of the prepared membranes was investigated. RESULTS: Permeate fluxes increased by increasing the axial velocity of the juice. The flow-pressure curves followed the gel-polarization model. All resistances, with the exception of the membrane resistance increased by increasing the operating pressure and decreased with the axial feed velocity. Polysulfone membranes exhibited higher steady state permeate flux (47 Lm-2 h-1) and lower rejection towards flavonoids (24.1%) and phenolic compounds (25.1%) in selected operating conditions. CONCLUSION: Polysulfone membranes were suitable for preserving phenolic compounds in the clarification of pomegranate juice. For these membranes operating conditions giving maximum permeation fluxes and minimum fouling index were identified.