Stability of caseinate solutions in the presence of calcium

The presence of calcium ions in aqueous solutions of bovine caseinate leads to the formation of large aggregates that precipitate after centrifugation. The residual fraction of soluble casein in the supernatant was measured as a function of the calcium concentration and the total caseinate content. It was found to be determined by the calcium concentration independent of the caseinate concentration. The soluble casein was characterized using light scattering and consisted of small aggregates with a radius of about 12 nm containing about 15 casein molecules. The composition of the soluble casein was determined with chromatography and was increasingly poor in α_s1-casein with increasing calcium content. The solubility of calcium caseinate was determined and related to the total calcium ion concentration.