6 - Novel Membrane Technologies for Protein Concentration and Fractionation

Abstract

Innovative membrane technologies for separation and concentration of proteins in foods are described in this chapter. The engineering principles of membrane separation are described first, including the models of Smith and Deen for transmission of protein in a cylindrical pore and the impact of the electrostatic double layer, surface charge density, protein net charge, protein diameter, and membrane pore diameter. The stagnant film model for membrane separations, first used by Alan Michaels in 1968, is used to explain the impact of permeate flux, mass transfer, and protein concentration on the thickness of the deposit layer formed on the membrane surface. Advances in charged ultrafiltration membranes and using membrane stages are used to illustrate the future replacement of chromatography by membranes for the purification and fractionation of proteins. The development of mass balance models for ultrafiltration and diafiltration, when combined with replacing constant transmembrane pressure control with constant polarization index control, are shown to eliminate the need for the current practice of expensive and time-consuming Edisonian experimental trials to develop and scale-up new membrane separation processes. Examples taken from the manufacture of ultrafiltered milk, soy protein concentrate, cheese whey protein concentrate, fractionation of α-lactalbumin and β-lactoglobulin from milk, and micellar casein concentrate fractionation from milk serum protein are used to illustrate the different sections in the chapter. As shown in this chapter, advances in membrane technology will continue to increase its use in the food industry for the foreseeable future.