Whey proteins carry bioactive sequences that can be released by enzymatic hydrolysis. Often, the resulting hydrolysates are in the need of a fractionation process to improve or define their bioactivity. In this work, a whey protein concentrate was hydrolysed with trypsin and the obtained peptides were separated by means of membrane ultrafiltration/nanofiltration. Three pH values (2, 6 and 8) were assayed for two polyethersulfone membranes having different pore sizes (1 and 5 kDa). beta-lactoglobulin peptides predominated in the hydrolysate as it was preferentially cleaved. Peptides net charge, charge distribution and size explained peptide transmissions. The highest transmissions were achieved at pH values near peptides isoelectric point. The best separation factors were obtained at basic pH values. A new membrane strategy was developed for obtaining permeates enriched in bioactive peptides from a complex hydrolysate. (C) 2016 Elsevier Ltd. All rights reserved.