Studies on Milk Powders. III. The Preparation and Properties of Milk Powders containing Low-Melting Butter Oil

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Abstract
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 wettabflities 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 19-2) ° C. had approximately the same wettability and dispersibility as com- mercial 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. The problem of preparing milk powders that will disperse readily in cold water has attracted widespread attention in recent years. Skimmilk powders can be made readily dispersible in water by a pro'eess commonly known as instanti- zation. A recent patent (5) describes an instantization process for skimmilk powder whereby tile milk powder is continuously moistened causing the particles to adhere together in the form of light, porous, random aggregates of a size substantially larger than the size o'f the original milk particles. The excess moisture is then removed from these aggregates to provide a final product that has a moisture content of less than 6%. In this connection, it may be recalled that the legal standard in the U.S.A. requires a moisture content of less than 5% in the final product. However, it has been found that the application to whole milk powder of the method (5) does not yield a readily dispersible product. Ashworth and Bendixen (1) have claimed that the physical state of the casein is a factor limiting the rate of dispersion of milk powder. They demon- strated that precondensation of the fluid milk to 40% total solids before spray- drying produced a powder which dispersed much more readily than did one made from the same milk precondensed to 20% total solids. Stone et al. (6) measured the self-dispersion of milk powders which varied in fat content from 7.5 to 48.3%. They found that self-dispersion decreased as the fat content of the powders was increased. Experiments in which the tempera- ture of the water varied showed that milk powder dispersed more readily in