Crossflow microfiltration of passion fruit juice after partial enzymatic liquefaction

To obtain clarified passion fruit juice, crossflow microfiltration after enzymatic liquefaction was studied using ceramic membranes with 0.2 mu m pore size. The effect of a high-rate enzymatic treatment for the degradation of suspended solids was assessed, resulting in the selection of a commercial enzymatic preparation. Partial enzymatic liquefaction of cell-wall polysaccharides prior to microfiltration provided an unusual pattern of flux increase after a short decline when crossflow velocity was high (7 m s(-1)). It was found that a synergistic effect between pectinase and cellulase activities enhanced permeate flux increase. With total recycling at 36 degrees C, the combination of low transmembrane pressure (150 kPa) and high enzyme concentration (1 ml l(-1)) provided the highest flux (113 1 h(-1) m(-2)). These conditions were then assessed with concentration in order to verify industrial feasibility and evaluate physicochemical characteristics of final products. A volumetric reduction ratio of 3 was maintained during 18 h without any decrease in permeate flux, which fluctuated around 40 1 h(-1) m(-2). The quality of permeate was satisfying even its aromatic strength was weakened. Retentate had similar characteristics of raw juice and could be recycled in order to use its residual enzyme activity. (C) 2000 Elsevier Science Ltd. All rights reserved.