Effect of hydrodynamic conditions on fractionation of β-lactoglobulin tryptic peptides using nanofiltration membranes

Fractionation of a β-lactoglobulin (β-LG) peptide mixture by nanofiltration (NF) membranes was investigated. Peptide mixture was prepared by tryptic hydrolysis of commercial β-LG followed by ultrafiltration (UF) for enzyme removal. The peptide mixture (permeate) was further fractionated using an Osmonics-SG13 cellulose acetate NF membrane with a molecular weight cut-off (MWCO) of 2500 g mol−1. The effect of hydrodynamic parameters on a “resistance-in-series” model and transmission of tracer peptides was studied at 0.5 wt.% hydrolysate concentration by varying the operating pressure (0.200 and 0.500 MPa), recirculation rate (0.17 and 0.29 m s−1), and recirculation time (30 and 120 min). A detailed comparison on individual peptide transmission revealed that increasing recirculation time to 120 min, at lower recirculation rates, greatly affected peptides β-LG 102–105 and β-LG 142–148 at both operating pressures. Our results are indicative of important changes in NF selectivity as affected by hydrodynamic conditions and recirculation time via possible peptide–peptide interactions occurring in the so-called weakly attached layer.