Structure and stability of nanogel particles prepared by internal cross-linking of casein micelles

Cross-linking all caseins within the casein micelles with the enzyme transglutaminase creates nanogel particles consisting of a covalently linked casein network from which micellar calcium phosphate (MCP) can be removed without compromising structural integrity. These casein nanogel particles show similar light, neutron and X-ray scattering behaviour to native casein micelles, indicating similarity in size and substructure. Casein nanogel particles are more stable to heat-induced coagulation, but less stable to acid-induced coagulation than native casein micelles. Changing the MCP content of casein nanogel particles to levels between 0% and 150% of its original concentration strongly affected colloidal stability of the particles. Stability to both heat- and acid-induced coagulation increased with decreasing MCP content. Casein nanogel particles offer applications not only in traditional dairy products, but also in products and applications where the integrity and biocompatibility of the nanogel particle is important.