Effect of pH on the fractionation of whey proteins with a ceramic ultrafiltration membrane

The purpose of this work was to investigate the potential of membrane ultrafiltration for the fractionation of clarified whey. Employing a 300 kDa tubular ceramic membrane in a continuous diafiltration mode, the effect of working pH was evaluated by measuring the flux-time profiles and the retentate and permeate yields of alpha-lactalbumin, P-lactoglobulin, BSA, IgG and lactoferrin. At pH 3, 9 and 10 permeate fluxes ranged from 68 to 85, 91 to 87 and 89 to 125 L/(m(2)h), respectively. On the other hand, around the isoelectric points of the major proteins (at pH 4 and 5), permeate fluxes varied from 40 to 25 and from 51 to 25 L/(m 2 h), respectively. For alpha-lactalbumin and P-lactoglobulin, the sum of retentate and permeate yields was around 100% in all cases, which indicates that no loss of these proteins occurred. After 4 diavolumes, retentate yield for alpha-lactalbumin ranged from 43% at pH 9 to 100% at pH 4, while for P-lactoglobulin, was from 67% at pH 3 to 100% at pH 4. In contrast, BSA, IgG and lactoferrin were mostly retained, with improvements up to 60% in purity at pH 9 with respect to the original whey. (c) 2006 Elsevier B.V. All rights reserved.