Abstract:In order to detect the polymorphisms of κ-casein and αs1-casein gene in yak milk from seven different pastures in certain areas of Qinghai province, the effect of gene polymorphisms on cheese coagulation characteristics was analized. Yak milk somatic cells were extracted, and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis technique was used to extract DNA for PCR amplification and enzymatic digestion, followed by gene typing based on electrophoresis bands. Yak milk proteins were also extracted and high-performance liquid chromatography(HPLC) was used to analyze the chromatographic profiles of various samples compared to the standard samples, with a focus on peak time and peak shape for gene typing. The rheological characteristics during coagulation for different genotypes of yak milk were determined by rheometer. Cheese coagulation time was recorded, and cheese yield was calculated. The results showed that there were three genotypes for the κ-casein gene in yak milk, i.e., type AA, AB and BB. The analysis of the three genotypes and coagulation characteristics showed that the A allele was favorable in terms of coagulation time. Similarly, for the αs1-casein gene in yak milk, three genotypes (AA, AB, and BB) were also identified. The analysis of the coagulation time, cheese yield, maximum dynamic viscosity, and maximum shear rate revealed that the B allele was favorable. The above results suggest that both κ-casein and αs1-casein of yak milk in seven Qinghai farms have gene polymorphisms. The A allele in κ-casein and B allele in αs1-casein are the main effective genes affecting the coagulation characteristics of yak milk.
