The objective of this study was to compare the behavior of different ceramic membranes during skimmed milk microfiltration. Permeate flow rates, protein rejection, and decimal reduction of bacteria were compared for three different 1.4-mm pore size ceramic membranes, one of which was considered traditional (ceramic multichannel membrane) while the other two had a modified structure (on either the macroporous support or the filtering layer). Permeate flux ranged from 400 to 530 Lm(-2) h(-1) at 0.5 bar of transmembrane pressure. Protein rejection values between 0.8 and 2.9% were obtained. Temperature (21-45 degrees C) did not have a significant effect. Membranes showed decimal reduction in total bacterial count between 3.5 and 5.2, with Isoflux (R) membranes showing higher values. The lifespan of microfiltered milk was extended to 10 days in the absence of heat treatment.