Milk Powders. V. Effects of the Interfacial Tension of Butter Oil in Powder on the Wettability of the Powder

Abstract

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.