THE INFLUENCE OF GENETIC-VARIANTS OF MILK-PROTEINS ON THE COMPOSITIONAL AND TECHNOLOGICAL PROPERTIES OF MILK .1. CASEIN MICELLE SIZE AND THE CONTENT OF NONGLYCOSYLATED KAPPA-CASEIN

Milk samples (total = 203) containing different genetic variants of th e milk proteins were analyzed for the average casein micelle diameter. In addition, most samples (n = 191) were analyzed for the content of nonglycosylated kappa-casein by IPG-IEF. Special attention was paid to the rare genetic variants (alpha(s1)-Cn C, beta-Cn B or C, and kappa- Cn C or E). There were highly significant (p<0.001) relationships betw een the genotypes of the beta-Cn, kappa-Cn and beta-Lg locus and the a verage diameter of the casein micelles. The kappa-Cn locus had the gre atest influence on the average micelle size, which increased from 190 nm to 229 nm in the following order: kappa-Cn BC/BB<AB<AC<BE<AA<AE. A highly significant relationship (p<0.001) was also observed between th e genotypes of the kappa-Cn locus and the content of non-glycosylated kappa-casein, which increased in the following order: AC/AE<AA<AB<BE<B C<BB. Milk of the type beta-Lg BB contained significantly more (p<0.05 ) non-glycosylated kappa-casein than the type beta-Lg AB and AA. The a llele kappa-Cn B in the genotypes AB, BC and BE induced a significantl y greater amount of non-glycosylated kappa-casein than the alleles A, C and E, whereas the A-allele induces significantly less non-glycosyla ted kappa-casein than the alleles B and E.