Cross-flow microfiltration - An extension of membrane processing of milk and whey

Current interest in dairy applications of the microfiltration technology has evolved due to the availability of ceramic membranes, first developed for use in the field of nuclear technology. As the primary goal of microfiltration is the removal particles from fluids, the clarification of whey has been the first application of cross-flow microfiltration in the dairy industry. Mineral membranes with pore sizes in the order of 0.1-1.0 microns effectively remove residual whey fat as well as bacteria; the protein is retained only if it is present in the form of large aggregates or associated with the fat. Narrow pore MF membranes (0.1-0.2 microns) retain casein micelles from skim or whole milk while undenatured whey proteins pass into the permeate. After adequate diafiltration, the casein-N can be increased to 96% of the total true-protein-N. Wide pore microfiltration membranes are now available for skimmilk processing to reduce the load of bacteria and spores thus leading to significant shelf-life improvements. However, these membranes cannot handle whole milk as the smaller fat globules penetrate the pores blocking the flow.