The effect of applying an external electrical field during lactoferrim (LF) and whey protein solutions microfiltration was studied. The impact of electrical field strength (0-3333 V m(-1)) and polarity on the permeation flux and protein transmission were investigated. The influence of LF iron saturation was also assessed. The electrically-enhanced membrane filtration (EMF) experiments were performed on a purpose-built flat-sheet module and operated in a full recirculation mode at low transmembrane pressure (0.7 x 10(5) Pa) and feed velocity (0.05 m s(-1)). The results showed that the application of an electrical field had an important impact on protein transmission. Selectivity enhancements were obtained, particularly when the cathode was on the retentate side. In that configuration (3333 V m(-1)), the separation factors obtained between LF and the two main whey proteins beta-lactoglobulin (beta-LG) and alpha-lactalbumin (alpha-LA) were, respectively, 3.0 and 9.1. Under those conditions, the electrical field increased permeation flux by a factor 3, suggesting an important decrease of membrane fouling. LF iron saturation also influenced its transmission under the electrical field and separation factors between holo-LF and beta-LG or alpha-LA were, respectively, up to 6.7 and 62.4 at 1667 V m(-1). This study shows the potential of EMF as regards LF fractionation in more complex fluids such as cheese whey. (c) 2007 Elsevier B.V All rights reserved.