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 α_S2-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.