Studies on Milk Powders. IV. The Foam and Sediment Fractions of Reconstituted Whole Milk

Whole milk powder was reconstituted and the resultant whole milk was passed through a 200-mesh sieve. This treatment removed virtually all the foam or scum from the surface of the milk. The milk was then centrifuged. The insoluble material (foam fraction) which remained on the sieve, and the insoluble material (sediment fraction) which was recovered by centrifugation, were washed with water and freeze-dried. The dried foam fraction contained about 50% more fat than did the sediment fraction. Melting point and iodine value determinations on the ether-extractable portions of the foam and sediment indicated that the fat of the sediment contained a higher proportion of unsaturated fatty acids than did the fat of the foam. Results of electrophoretic analyses of the ether-insoluble portions of the foam and sediment indicated that the major protein constituent of the sediment was beta-laetoglobulin, and that of the foam was casein.