ABILITY OF CERAMIC MEMBRANES TO REJECT LIPIDS OF DAIRY-PRODUCTS

Sweet buttermilk, skim milk and sweet whey were microfiltered on ceram ic membranes to remove the residual fat. Pore diameters of membranes w ere 1.4 0.8, 0.5, 0.2 and 0.1 mu m. The results exhibited a size-exclu sion mechanism, approximately according to Ferry's law. There was a st rong correlation between lipid and protein retentions. The correlation made possible a selective removal of lipids from sweet whey (86%) wit hout a too high retention of protein (29%) using a 0.2 mu m membrane. Buttermilk and skim milk contained casein and lipid particles with a d iameter around 200 nm; therefore, a size-exclusion mechanism was unabl e to achieve selective separation of lipids. Chemical modification (pH adjustment, calcium and citrate addition) of buttermilk had little ef fect on lipid retention.