Solubility of calcium and zinc in model solutions based on bovine and human milks.

The solubility of calcium, magnesium, and zinc in model solutions based on the low molecular weight components of bovine and human milks was examined over a pH range similar to that found in the human digestive system. Zinc was removed from solution in all models as calcium phosphates precipitated. The pH at which precipitable calcium phosphates formed was altered by the concentration of inorganic phosphate. All calcium and zinc in a model based on human milk remain in solution up to pH 6.5 while in a model based on bovine milk they were in solution up to pH 5. The use of simple model solutions may provide information useful for understanding the different bioavailabilities of minerals from skimmed bovine and human milks.