The influence of various emulsifier types (anionic, nonionic, and zwitterionic) on the mean particle size, transmembrane flux, and membrane fouling in repeated membrane homogenization using a Shirasu porous glass (SPG) membrane has been investigated. Oil-in-water (O/W) emulsions (40 wt % corn oil stabilized by 0.06-2 wt % sodium dodecyl sulfate (SDS) or 0.1-2 wt % Tween 20 at pH 3 or 0.5-2 wt % beta-lactoglobulin (beta-Lg) at pH 7) were prepared by passing coarsely emulsified feed mixtures five times through the membrane with a mean pore size of 8.0 mu m under the transmembrane pressure of 100 kPa. The flux increased as the number of passes increased, tending to a maximum limiting value. The maximum flux for the Tween 20-stabilized emulsions (5-47 m(3.)m(-2.)h(-1)) was smaller than that for the SDS-stabilized emulsions (29-60 m(3.)m(-2.)h(-1)) because less energy was needed for the disruption of a SDS-stabilized droplet due to the lower interfacial tension. The mean particle size after five passes was 4.1-6.8 and 6.4-8.7 mu m for 0.1-2 wt % SDS and Tween 20, respectively. The flux in the presence of beta-Lg was much smaller than that in the presence of SDS and Tween 20, which was a consequence of more pronounced membrane fouling, due to the protein adsorption to the membrane surface. After five passes through the membrane, the fouling resistance in the presence of 2 wt % beta-Lg (1.1 x 10(10) l/m) was 2 orders of magnitude higher than that for 0.5 wt % Tween 20 and an order of magnitude higher than the membrane resistance. If a clean membrane was used in the fifth pass, a 2-fold reduction of the fouling resistance was observed.