Composition of poorly and non-coagulating bovine milk and effect of calcium addition.

Ninety-nine individual milk samples from 37 cows in lactation week 10-35, selected for producing well or poorly/non-coagulating milk, were compared regarding protein composition, total calcium content, casein micelle size, pH, and coagulating properties after addition of 0·05% CaCl₂. The results showed that a low κ-casein concentration in milk was a risk factor for non-coagulation. CaCl₂ addition improved coagulating properties (coagulation time, curd firmness) of nearly all samples and eliminated differences between poorly/non-coagulating and well-coagulating milk, particularly regarding curd firmness.

Casein retention in curd and loss of casein into whey at chymosin-induced coagulation of milk.

Impact of milk protein composition on casein (CN) retention in curd during the milk coagulation process was studied using a model cheese making system. Individual milk samples from 110 cows in mid lactation of the Swedish Red and Swedish Holstein breeds with known genotypes of beta-casein, kappa-casein and beta-lactoglobulin were defatted, coagulated with chymosin, subjected to syneresis and subsequent pressing simulated by centrifugation. The results indicated that kappa-casein concentration of milk plays an important role in the curd formation process and initial syneresis (whey after cutting), whereas an increased CN ratio was associated with less casein in whey after simulated pressing.