Size of native and heated casein micelles, content of protein and mineralsin milk from Norwegian Red Cattle - effect of milk protein polymorphism and different feeding regimes

Milk samples of 59 cows of the Norwegian Red Cattle breed receiving three d ifferent supplementary concentrates, were analysed for genotypes of caseins and whey proteins, the content of different milk salts (Ca2+, Ca, Mg and c itrate), the content of total protein, casein and whey protein and the mean micellar size of native and heated casein micelles. The genotype of alpha( s1)-casein had a statistically significant effect on the content of protein and casein, and the content of whey protein and the casein number were sig nificantly influenced by different feeding regimes, and the content of citr ate. The mean size of native and heated casein micelles was significantly i nfluenced by the feeding regimes, genotype of alpha(s1)-casein (native mean size only) and kappa-casein, pH and the content of casein, whey protein an d casein number. The heat-induced changes in mean micellar size were signif icantly affected by the calcium ion activity which accounted for approximat ely 40% of the total variation. (C) 2000 Elsevier Science Ltd. All rights r eserved.