Phase stability of concentrated dairy products.

The interactions between the two most important colloids in milk, fat globules and casein micelles, were investigated. Mixtures of oil droplets (as a model for fat globules) and casein micelles were prepared, and their phase behavior was studied. It was found that the oil droplets and the casein micelles phase separate as a result of depletion interaction. The experimentally determined phase boundary is consistent with a prediction by theory that involves no adjustable parameters. Furthermore, it is shown that the kinetics of phase separation can be explained by the differences in viscosity of the samples. The results are of relevance to the behavior of concentrated dairy products such as whipping cream and evaporated milk.