In the project PROFOS, FrieslandCampina and NIZO food research studied the functionality of casein focusing on water holding and viscosity. By combining various techniques, the distribution of water in the casein micelles was determined. A distinction can be made between water bound by the protein, water associated with the k-casein brush, and water entrapped in the casein micelles. The distribution of water in the casein micelles leads to voluminous protein particles with relatively high viscosity. In sodium caseinate, the caseins exist as small particles. For these caseinate particles, the main contributor to viscosity is their non-spherical particle shape.
Based on the results of this study we may describe the structure of the casein micelle as a porous network of non-spherical casein particles linked by calcium phosphate nanoclusters. These casein particles are the same as those found in sodium caseinate.
Pictures below: schematic representation of casein micelles (cross-sections)
(drawing by Rogier Trompert Medical Art)