Partition of milk salts between colloidal and soluble phases

7 Partition of milk salts between colloidal and soluble phases 

Certain of the milk salts (e.g. chlorides, and the salts of sodium and potassium) are sufficiently soluble to be present almost entirely in the dissolved phase. The concentration of others, in particular calcium phosphate, is higher than can be maintained in solution at the normal pH of milk. Consequently, these exist partly in soluble form and partly in an insoluble or colloidal form associated with casein. The state and distribution of these salts has been extensively reviewed by Pyne (1962) and Holt (1985). 

The dividing line between soluble and colloidal is somewhat arbitrary, its exact position depending very much on the method used to achieve separation. However, a fairly sharp separation between the two phases is not difficult since the insoluble salts occur mainly associated with the colloidal casein micelles. 

---