Heat-induced coagulation of goat milk: modification of the environment of the casein micelles by membrane processes

Unlike bovine milk, goat milk is characterised by a very low heat stability at its natural pH (i.e., 6.6-6.7). In the present work, combined membrane processes were used to evaluate how modi- fying the environment of the casein micelles affects the heat stability of milk. It was shown that the in- crease of 1.4 times of the caseins: whey proteins ratio, either through a reduction of whey proteins content or selective concentration of caseins, increased the heat coagulation temperature from 135 o C to 141 o C. Further improvement of the stability was obtained by concomitant dilution of both whey proteins and soluble low molecular weight components. From these results, we propose that the de- stabilising effect of whey proteins at the natural pH is linked to their ability to sensitise casein mi- celles to heat-induced precipitation of calcium phosphate. Goat milk / heat stability / membrane processing / casein:whey proteins ratio