Factors Affecting the pH-Sensitivity of the Heat Stability of Milk from Individual Cows

Abstract

The heat stability of milk passes through a maximum and a minimum as the pH is increased from 6.4 to 7.0. The position of the maximum was displaced slightly to the acid side with addition of phosphate, and slightly towards the alkaline side with addition of Ca, but the maximum heat stability attainable was only slightly affected by small additions (up to 3 m[image]/1) of these ions. The occurrence of the maximum and minimum in the pH-heat stability reaction was dependent upon the presence of [beta]-lactoglobulin. The maximum heat stability of calcium-caseinate-phosphate complex resuspended in ultrafiltrate from milk increased, and the minimum decreased, with increasing addition of [beta]-lactoglobulin from 0.1 to 0.6 mgm [image]/ml. However, it could not be concluded that [beta]-lactoglobulin was the only factor influencing the pH-heat stability response in normal milks. It is suggested that the denatured [beta]-lactoglobulin-casein (or K-casein) complex is the pH-sensitive component.