Whey microfiltration performance: influence of protein concentration by ultrafiltration and of physicochemical pretreatment

Abstract

Microfiltration with membranes of 0.2 urn pore size was used to c1arify and defat whey previously ultrafiltered at various volume concentration ratios (VCR, 1-5.5). Physicochemical pretreatment of whey combining calcium addition (in order to reach a final concentration in the range 1.3-3.3 g'kg-1), pH increase to 7.3 and a heat treatment (60°C, 10 min) were carried out. The efficiency of rnicrofiltration, performed 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 evidence of rapid membrane fouling. A low total nitrogen matter recovery (TNMr) of 0.41 was obtained. Pretreatment of VCR 2.5 and VCR 4.0 retentates allowed higher TNMr (0.65) and better hydraulic performance, ie slower TP increase to be obtained. With no physicochemical pretreatment, VCR 2.5-4.0-5.5 retentates led to improved hydraulic performance and higher TNMr (0.90).