Effects of pH and calcium contents on the enzyme-induced coagulation of UHT treated milk

Abstract

UHT milk does not coagulate with milk-clotting enzymes, but it will coagulate by calcium addition or the pH adjustment lower than 6.1. The purpose of this study is to make clear the mechanism of coagulation of UHT milk by measuring the dynamic viscoelasticity. Differences in the physical properties of chees curd were observed between calcium addition and acidification. We considered the reason that with calcium addition, the increase in micellar calcium phosphate and the additional formation of casein micelles strengthen the interaction between casein micelles, whereas acidification causes the elution of micellar calcium phosphate into the whey fraction and reduce the electrostatic repulsion between micelles.