MICROPOROUS ULTRAFILTRATION OF SKIM MILK

Membranes with porosities of 100 and 200 nm were used to obtain a 4:1 milk volume reduction. Average micelle diameters determined from electron micrographs were 46 nm (permeate) and 52 nm (permeate) for the 100-nm-pore fractions and 46 and 55 nm for the 200-nm-pore fractions. The calculated average micellar volumes of the retentate fractions were about twice those of the corresponding permeate fractions. Casein-whey ratios were 0.7-0.9 in the permeates and 5.0-7.7 in the retentates. Higher alpha(s2)- and lower beta-casein contents were found in the permeate micelles than in the retentates.