Structure of casein micelles and their complexation with tannins

Abstract

We have investigated the structure of casein micelles using small-angle X-ray scattering, spanning three orders of magnitude in scattering vector. The high-resolution scattering data can be modeled in terms of a polydisperse spherical core–shell structure with the core consisting of a protein matrix reticulated with ellipsoidal calcium phosphate nanoparticles and a brush layer of κ-caseins. This model is validated by means of the structural modification induced by the addition of small tannins which have an affinity towards the proline groups on the proteins. Small tannins are readily incorporated into the protein matrix in large numbers without causing significant change in the globular size of the micelles, but instantaneously (within 2 ms) disintegrating the embedded colloidal calcium phosphate nanoparticles.