Properties of Emulsions Stabilized with Milk Proteins: Overview of Some Recent Developments

Abstract

The physico-chemical properties of oil-in-water emulsions that are stabilized by milk proteins are determined largely by the nature of the adsorbed layer at the surface of the dispersed droplets. Detailed information on the structure of the adsorbed layer is now available for some of the pure milk proteins, especially b-casein and b-lactoglobulin. Recent analysis of the segment density profiles that are normal to the surface has shown clear differences in layer structure between the disordered casein and the globular whey protein. The phosphoserine residues of b-casein are essential in providing the thickness and stericstabilizing properties of the layer. Surface coverage and segment density profile are sensitive to bulk protein concentration, pH, ionic strength, and calcium ion content. Functional properties of commercial milk protein ingredients are influenced also by compositional and structural heterogeneity. Unadsorbed protein may make additional contributions to the properties of casein-stabilized emulsions, especially creaming and flocculation behavior.