[Relationship between thermal treatment of milk and hysteresis of the milk protein system. II. Studies on casein micelles (author's transl)].
The association of colloidal calcium phosphate with the casein micelles is the principal reason for hysteresis of the milk protein system. Because of this association the secondary calcium phosphate cannot be titrated at its pK = 7.2, but only at lower pH values depending on the previous thermal treatment of the milk. However after overcoming certain energy barriers it can be titrated (between pH 5.8 and 5.2), but then calcium phosphate is separated irreversibly from the micelles. Therefore in the subsequent base titration other molecular conditions are passed through than in acid titration. The consequence is a hysteresislike titration curve. By heating, the surface of the micelles are covered successively with serum proteins. Due to this coating additional diffusion barriers are constructed. The diffusion of the protons into the interior of the micelles is measurably retarded. The expansion of the hysteresis loop can be determined quantitatively.
[Relationship between thermal treatment of milk and hysteresis of the milk protein system. II. Studies on casein micelles (author's transl)]. The association of colloidal calcium phosphate with the casein micelles is the principal reason for hysteresis of the milk protein system. Because of this association the secondary calcium phosphate cannot be titrated at its pK = 7.2, but only at lower pH values depending on the previous thermal treatment of the milk. However after overcoming certain energy barriers it can be titrated (between pH 5.8 and 5.2), but then calcium phosphate is separated irreversibly from the micelles. Therefore in the subsequent base titration other molecular conditions are passed through than in acid titration. The consequence is a hysteresislike titration curve. By heating, the surface of the micelles are covered successively with serum proteins. Due to this coating additional diffusion barriers are constructed. The diffusion of the protons into the interior of the micelles is measurably retarded. The expansion of the hysteresis loop can be determined quantitatively.