Ultrafiltration of Soluble and Heat Precipitated Whey Protein Concentrates

Abstract

Recent studies (1) have indicated the potential for flux improvements in ultrafiltration of isoelectrically precipitated soy proteins in comparison to soluble soy proteins. Significantly different transmembrane-pressure-drop vs permeate flux profiles, and protein content vs flux profiles of the soluble and precipitated systems were related to flux improvements at high protein concentrations. The ultrafiltration of previously UF-prepared 50 litre aliquots of heated (90°C, 15 minutes) 1.2% protein retentates (12% TS) and diafiltrates (5.5% TS) from cottage cheese whey in a DDS Lab-20 UF unit equipped with 20 GR61-PP polysulphone membranes did not result in improvement of UF performance compared to identical soluble systems. In conditions of 200–1100 kPa and 20°C, fully heat denatured and precipitated protein systems did not result in higher flux rates for a given applied transmembrane pressure. Precipitated whey proteins, when concentrated batchwise, exhibited a more rapid drop in permeate flux and at a lower TS content than soluble whey proteins. At 17.5% TS, near the maximum concentration of 18% TS obtained in the diafiltered precipitated system, the measured viscosity was 2 30 centipoise. This compared to 45 centipoise for a 17.5% TS diafiltered soluble concentrate.