Relation Between α-Casein Content and Coagulation Properties of Milk from Swedish Dairy Goats

ABSTRACT

High frequency of Swedish Landrace goats are the carriers of a mutation, where the affected goats are not able to produce α_S1-casein (α_S1-CN) in the milk. As a consequence the lack of this protein is connected to lower cheese yield. The aim of this study was thus to determine the relationship between the α_S1-CN content and coagulation properties of milk from Swedish Landrace goats. Milk samples from 62 dairy goats from two herds were analysed. As many as 44% goats showed low or no production of α_S1-CN. Only 24% of the investigated goats showed high production of this protein. The coagulation properties of milk from the dairy goats were clearly influenced by the concentration of α_S1-CN. The milk from low level α_S1-CN animals resulted in 15% longer coagulation time and 60% weaker gels compared to the gel firmness of the high expressing group. The coagulation time was strongly associated with the pH of the milk (p<0.001), where the milk with low α_S1-CN content had higher pH. Further, goat milk with low levels of α_S1-CN was shown to have significantly lower total protein (p<0.05) compared to milk from high expressing α_S1-CN goats.

Keywords:

α-casein, capillary zone electrophoreses, coagulation time, gel firmness, rheology, Swedish Landrace goats.