Factors Affecting the Heat Stability of Milk

Abstract

Removal of colloidal calcium phosphate from milk by acidification and dialysis increased heat stability of the milk and eliminated the minimum from the heat stability-pH relation. If dissolution of the colloidal phosphate had approached completion, the normal heat stability-pH relation was not recovered by reprecipitation of the phosphate by neutralization before dialysis. Increasing the degree of forewarming progressively decreased coagulation time at 140 C at all equivalent points on the heat stability-pH curve, but the cumulative heating time decreased markedly in only one of five milks tested. The behavior of an individual milk after forewarming depended upon its original pH relative to the pH of maximum heat stability. With milks from 20 individual cows, both maximum and minimum heat stability (min) were significantly correlated with β-lactoglobulin content (mg n/ml) (r = +0.50 and −0.52, respectively). Inorganic components, and ratios of these, were not correlated with maximum heat stability. © 1962, American Dairy Science Association. All rights reserved.