EFFECT of pH and ENZYMATIC TREATMENT ON MICROFILTRATION and ULTRAFILTRATION of TANGERINE JUICE

Tangerine (Citrus reticulata blanco) juice clarification by crossflow microfiltration and ultrafiltration using polysulphone flat sheet membranes with nominal molecular weight cut off of 25,000, 50,000, 100,000 and 0.1 μm, 0.2 μm pore sizes was studied. the juice was pretreated by polygalacturonase and pH adjustment. the treated juice was clarified with a laboratory scale filtration unit with effective filtration area of 14 cm2. Filtration conditions were transmembrane pressure of 93 to 194 kPa, crossflow velocity of 0.96 to 3.5 m/s and 25°C. Membrane performance was evaluated in terms of volume flux and clarity (% transmittance) of the permeate. Pretreatment of the juice by polygalacturonase and adjustment to pH 2 with HCl resulted in a clearer supernatant than enzyme treatment alone. Maximum flux was obtained with the 0.1 μm microfiltration membrane. Flux increased with transmembrane pressure and crossflow velocity. Flux at 194 kPa and 3.5 m/s was 69 L per square meter per hour. Permeate clarity was better at higher transmembrane pressure and lower velocity, due to the effect of the polarized/fouling layer of solute on the membrane surface, which acted as a secondary “dynamic” filter.