CLEAVAGE OF THE LINKAGE BETWEEN COLLOIDAL CALCIUM-PHOSPHATE AND CASEIN ON HEATING MILK AT HIGH-TEMPERATURE

In order to examine the effect of heating on the changes in the linkage between colloidal Ca phosphate (CCP) and casein, high-performance gel chromatography of casein micelles disaggregated by 6 M-urea was carried out using 6 M-urea simulated milk ultrafiltrate as the effluent. Although the CCP content increased when whey protein-free (WPF) milk was heated at 60–90 °C for 10 min, almost no changes in the content of casein aggregates cross-linked by CCP were observed. The content of casein aggregates cross-linked by CCP decreased from 51.9 to 46.1% in WPF milk and from 52.3 to 43-6% in concentrated WPF milk on heating at 135–140 °C for 75 s, indicating the cleavage of the linkage between CCP and casein. The cleavage of the linkage between CCP and casein on heating was considered to occur without liberation of ester phosphate groups. It was suggested that the transformation of CCP to another form was responsible for the cleavage between CCP and casein on heating milk at high temperature. © 1990, Proprietors of Journal of Dairy Research. All rights reserved.