Peptide adsorption occurring on conventional anion- and cation-exchange membranes is one of the main technological locks in electrodialysis (ED) for hydrolysate demineralization. Hence, the peptide fouling of monovalent anion (MAP) and monovalent cation (MCP) permselective membranes was studied and compared to conventional membranes (AMX-SB and CMX-SB). It appeared that the main peptide sequences responsible for fouling were TPEVDDEALEKFDK, VAGTWY and VLVLDTDYK for both anionic membranes; and ALPMHIR and TKIPAVFK for both cationic membranes. However based on the MS-MS results, the fouling was about 97-100% lower for MAP than AMX-SB and 95-100% lower for MCP than CMX-SB. This was explained by the differences in charge sign distribution at the membrane surface. Consequently, monovalent membranes can represent a very interesting opportunity for treatment of hydrolysate solution in electrodialytic processes by practically eliminating peptide fouling. At our knowledge, it was the first time that such a demonstration was done.