Ion-exchange membranes undergo fouling by aromatic amino acids during the electrodialysis demineralization process. It is shown that fouling of heterogeneous anion-exchange membrane MA-41 occurs at current densities close to the limiting values. As a result, membrane conductivity decreases significantly in solutions containing phenylalanine and sodium chloride. IR spectra confirm the presence of amino acid anions and bipolar ions in membrane phase after electrodialysis demineralization of phenylalanine containing solutions. Contact angle measurements of membranes equilibrated in solution containing aromatic amino acid reveal an increase of membrane surface hydrophobicity. (C) 2010 Elsevier B.V. All rights reserved.