The detailed chemical composition of 25 milks from different breeds of cow, sheep and goat were related to their properties of rennet clotting, coagulum development and syneresis at pH 6·4. Experiments in which concentrations of fat and whey proteins in milk were manipulated, and in which milks were homogenized at different pressures, were also carried out and the effects observed were related to the above processes.
The composition of milks varied widely and many relations between concentrations of components could be related to their known modes of secretion from the alveolus or to their structural functions in the colloidal phase of milk. Rennet clotting was related to total Ca concentration and also to the proportions of αs- and β-caseins present. Coagulum strength was strongly related to total casein concentration in milk but was unaffected by total fat content or by casein/fat ratios. Syneresis was inversely related to fat content of milk and little affected by coagulum strength. Homogenization retarded syneresis, probably by altering coagulum structure and modifying entrapment of fat globules within the coagulum.