Impact of genetic variants of milk proteins on chymosin-induced gelation properties of milk from individual cows of Swedish Red dairy cattle

Chymosin-induced gelation properties of the milk of around 400 Swedish Red dairy cows was investigated with the aim of identifying genetic protein variants that influence chymosin-induced gelation for optimisation of cheese milk through breeding practices. The variation in chymosin-induced gelation properties was shown to be large in the milk of Swedish Red and there was a high frequency of cows producing non-coagulating milk, 18%. The present study showed that the common composite β-κ-casein genotypes A1A2/AE and A2A2/AA were associated with both poor gelation properties and non-coagulation in the milk of Swedish Red. The present study suggests that if the frequencies of composite genotypes A1A2/AE and A2A2/AA were decreased in the Swedish Red population in favour for A1A1/AA and A1A1/AE, this could have a positive effect on the rennetability of the milk.