Internal Structure of Casein Micelles from Bovine Milk

The internal structure of casein micelles frmn bovine milk has been reinvestigated. Observations from electron microscopy, X-ray diffraction, and enzymatic digestion of the micelles followed by centrifugation suggested that electron-dense particles in the micelles are probably granules of colloidal calcium phosphate and not protein aggregates. These granules are embedded in a surrounding matrix of caseins to form the micelle. The loci of formation of the calcium phosphate granules may be either the ester phosphate groups or the e-amino groups of lysine.