Influence of β-lactoglobulin and calcium chloride on the molecular structure and interactions of casein micelles

Targeted processing of casein micelles (CM) requires a basic understanding of their molecular structure as well as their interactions with each other and with other components. In this study, angle- and concentration-dependent static and dynamic light scattering is applied to investigate changes in the molecular weight, size, and intermolecular interactions of CM after the addition of β-lactoglobulin (β-Lg) and calcium chloride. Addition of a surplus of β-Lg impairs the colloidal stability of CM. In the presence of 0.5 wt% β-Lg and natural calcium chloride concentrations (10 mM), the molecular weight of CM is reduced and the radius of gyration is increased. Both changes can be explained by the release of αS2-casein and κ-casein, which were determined in higher concentration free in solution by High performance liquid chromatography. In contrast, the structure of casein micelles is not altered by the presence of β-Lg at elevated calcium chloride concentrations. The repulsive forces between the CM show no significant dependence on β-Lg for all calcium chloride concentrations tested.