The effect of heat on the calcium salts and rennet coagulability of cow's milk. ∗

Abstract

Summary

It is shown that the partial fixation of the calcium salts of milk by pasteurization or boiling is readily explained simply on the grounds of the effect of heat on colloidal solutions of CaHPO₄, the calcium phosphate natural to cow's milk.

It is shown further that the effect of heat in retarding the rennet coagulability of milk is not related directly to the loss of colloidal CaHP0₄ because the addition of colloidal CaHP0₄ to dialyzed milk does not restore its coagulation by rennet, while the addition of CaCl₂ or HCl does restore this property.

The phenomenon of rennet coagulation is discussed briefly from the standpoint of the chemical and physico-chemical reactions involved, and also from the standpoint of the possible bearing which the addition of calcium salts to heated milk has on this phenomenon.