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Summary 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-lactoglobulin, and that of the foam was casein.

Summary Butter oil was fractionated to obtain products melting at 19–21, 22–24, and 28–30° C. Agglomerated milk powders were prepared, each containing one of these fat fractions, and one powder was prepared containing the unfractionated butter oil. The wettabilities and dispersibilities of the four products were compared with those of commercial whole milk powder and commercial instant skimmilk powder. The results showed that the melting point of the fat in a milk powder affects greatly its wettability and dispersibility. In particular, the milk powder which contained the butterfat fraction melting at 19–21° C. had approximately the same wettability and dispersibility as commercial instant skimmilk powder. The results suggest that control of the physical properties of the fat component of a dried milk powder provides a means of preparing a milk powder with the fat content of whole milk powder and the wettability and dispersibility of a Superior grade of instant skimmilk powder.

Summary Experiments have shown that a spray-dried, agglomerated milk powder containing approximately 25% low-melting (19–21° C.) butter oil fraction, has about the same wettability and dispersibility at 24° C. as a superior grade of instant skimmilk powder. The interfacial tension (oil-water) of this low-melting butter oil fraction was lower than that of higher-melting fractions which yielded much less wettable milk powders. This suggested that the interfacial tension of the fat may play an important role in wettability. Milk powders were prepared from homogenized mixtures of butter oil and condensed skimmilk. In one series of experiments surface active agents were added to the butter oil and in another series they were added to the condensed skimmilk. Wettability measurements on the various milk powders showed that the monoglycerides (Myverol) exerted a more pronounced effect on wettability when they were incorporated in the nonfat portion of the milk, and the Span and Tween preparations exerted a more pronounced effect when they were incorporated in the fat portion of the milk. The results showed that alterations in the interfacial tension of the fat component of a milk powder does not of itself exert a marked effect on wettability.

Strontium-90 and cesium-137 were determined in 40 samples of human milk obtained from 21 different communities in Alaska, as well as in polar bear, dall sheep, and harp seal milk. The average cesium-137 content (pCi per gram of ash) of all samples of human milk collected in Alaska in 1968 was only 3.3% of the average value for all samples of human milk collected in the Northwest Territories in 1967. The average strontium-90 content of the same Alaskan milks was about 10% higher than that of the human milk collected in the Northwest Territories.