Effect of somatic cell counts on ewes' milk protein profile and cheese-making properties in different sheep breeds reared in Spain

Bulk tank ewe's milks from Assaf, Castellana and Churra breeds categorized within three different Somatic Cell Count (SCC) groups (LSCC: <500 000; MSCC: 1 000 000 to 1 500 000; and HSCC: 2 500 000 to 3 000 000 cells ml(-1)) were used to investigate changes in capillary electrophoresis protein profiles and cheese-making properties. The results do not reveal a significant effect of SCC on total casein contents, because the sum of beta-caseins decreased as SCC increased; no statistically significant differences were observed for the sum of alpha-caseins, and the values of kappa-casein were higher in the HSCC milk. However, the soluble proteins other than alpha-lactalbumin and beta-lactoglobulin increased with SCC. Regarding the effect of breed, the Assaf breed had the lowest contents of kappa-CN, alpha(s1)-I-CN, alpha(s1)-II-CN (1)-CN, alpha(s1)-III-CN, beta(1)-CN and beta(2)-CN. The protein profile was significantly correlated with curd textural properties. alpha(s1)-I-CN was the most influential variant because it was positively correlated with a large number of textural parameters. Cheese yield was positively correlated with all casein variants except alpha(s1)-III-CN, showing that the milk from local breeds were more suitable for cheese-making clue to their higher contents of all the casein variants. Regarding curd texture properties LSCC milk curds showed more cohesiveness, associated with its lower content of alpha(s1)-III-CN and Castellani milk curds showed the highest values for firmness owing to their higher content of alpha(s1)-I-CN.