Effect of Various Salts on the Coagulation of Casein

Abstract

Addition of potassium or sodium chloride (80 or 130 mM) to skimmilk increased the time the milk could be held in frozen storage without development of 4% precipitate by volume. Addition of phosphate or calcium (10 mM) had the opposite effect. Addition of large amounts of sodium chloride (up to 1.0 M) offset the destabilizing effect of phosphate or calcium at 0, 10, and 20° F., but addition of similar amounts of potassium chloride stabilized the samples only at 10 and 20° F. Addition of potassium chloride (1.0 M or more) and of phosphate (100 mM or more) induced gelation of milk at room temperature. Addition of sodium chloride and phosphate did not induce gelation. Addition of either potassium or sodium chloride (2.3 M) shifted approximately 20% of the insoluble calcium and 7.5% of the insoluble phosphate to the soluble forms, displaced calcium from casein, and increased the dissociation of calcium citrate. A possible explanation of these effects, based on the interlinking of potassium-calcium-caseinate micelles by precipitating calcium phosphate, is presented. © 1959, American Dairy Science Association. All rights reserved.