Effect of Various Salts on the Coagulation of Casein

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Abstract
Addition of potassium or sodium chloride (80 or 130 m[image]) to skim milk increased the time the milk could be held in frozen storage without development of 4% precipitate by volume. Addition of phosphate or calcium (10 m[image]) had the opposite effect. Addition of large amounts of sodium chloride (up to 1.0 [image]) offset the destabilizing effect of phosphate or calcium at 0, 10, and 20[degree]F, but addition of similar amounts of potassium chloride stabilized the samples only at 10 and 20[degree]F. Addition of potassium chloride (1.0 [image]or more) and of phosphate (100 m[image] 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 [image]) 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-casemate micelles by precipitating calcium phosphate, is presented.