The objective of this work was to fractionate a bovine haemoglobin peptic hydrolysate mixture by electrodialysis with ultrafiltration membranes (EDUF) to increase the value of slaughterhouse by-products such as blood protein. A raw hydrolysate and a discolored hydrolysate (from which the haem was previously removed by ultrafiltration) were treated by EDUF. EDUF appeared to be a very selective separation method and due to the nature and concentration of peptides present in the hydrolysates, migration of cationic peptides was favoured. However, the migration rates were higher for the discolored hydrolysate, with a peptide migration quite doubled in comparison with the raw hydrolysate: the raw hydrolysate contains haem, which severely decreased the peptide migration by fouling the membrane. This demonstrated that pre-treatment of the hydrolysate by ultrafiltration to remove molecules with high molecular weights, could be a good alternative to preserve EDUF permselectivity all along the treatment and during consecutive runs. (C) 2010 Elsevier B.V. All rights reserved.