GENETIC-POLYMORPHISM OF KAPPA-CASEIN AND RENNET COAGULATION TIME - EFFECTS OF SERUM PHASE COMPONENTS

Using individual milks from 6 pairs of cows differing in kappa-casein phenotype, we have confirmed improvements in rennet coagulation proper ties in the milks of kappa-BB homozygotes, employing the HOLTER-FOLTMA NN linear relationship between RCT and reciprocal chymosin concentrati on as our diagnostic tool. The renneting behaviour of milk from a kapp a-BB cow gives a lower slope and smaller intercept than that of its ka ppa-AA partner. These differences are not exchanged when the milk sera are interchanged by prolonged cross-dialysis of one milk against that of its partner, though there are movements of slope and intercept in the direction anticipated from the changes to new soluble calcium (Ca- S) and pH levels. Though they can be influenced by Ca-S and pH, the di fferences observed in rennet coagulation properties between kappa-case in phenotypes are not due to variations in mineral content of these mi lks.