WHEY MICROFILTRATION PERFORMANCE - INFLUENCE OF PROTEIN-CONCENTRATIONBY ULTRAFILTRATION AND OF PHYSICOCHEMICAL PRETREATMENT

Microfiltration with membranes of 0.2 mum pore size was used to clarif y and defat whey previously ultrafiltered at various volume concentrat ion ratios (VCR, 1-5.5). Physicochemical pretreatment of whey combinin g calcium addition (in order to reach a final concentration in the ran ge 1.3-3.3 g-kg-1), pH increase to 7.3 and a heat treatment (60-degree s-C, 1 0 min) were carried out. The efficiency of microfiltration, per formed at a constant permeation flux, was compared with centrifugation . Pretreatment of retentate concentrated to a VCR of 5.5, led to poor hydraulic performance: a continuous increase in transmembrane pressure (TP) over the whole run (60 min) from 0.05 to 0.15 MPa brought eviden ce of rapid membrane fouling. A low total nitrogen matter recovery (TN Mr) of 0.41 was obtained. Pretreatment of VCR 2.5 and VCR 4.0 retentat es allowed higher TNMr (0.65) and better hydraulic performance, ie slo wer TP increase to be obtained. With no physicochemical pretreatment, VCR 2.5-4.0-5.5 retentates led to improved hydraulic performance and h igher TNMr (0.90).