Effects of somatic cells on the protein profile of hard ovine cheese produced from different breeds

Abstract

Bulk tank ewe's milks with low (<500,000 ml−1), medium (1,000,000–1,500,000 ml−1) and high (>2,500,000 ml−1) somatic cell counts (SCC) from three breeds were used to manufacture hard ewes’-milk cheese. Physico-chemical analysis and capillary electrophoresis of fresh cheeses and cheeses that had been ripened for 1, 2, 3 and 6 months were carried out. The results showed that high SCC levels in milk affected the moisture content of only freshly made cheeses and the pH, fat content and fat acidity of ripened cheeses. Regarding proteolysis, the levels of all β-CNs in freshly made cheeses were significantly lower as the SCC values increased and the Castellana breed was the most affected by SCC levels because a significant decrease in all α-CNs was also observed as SCC levels rose. Analysis of the casein profile by principal component analysis (PCA) revealed that there were no clear differences according the SCC up to the third month. However in the third and sixth months cheeses with low levels of SC were closely grouped and characterised by the highest levels of intact caseins. Regarding the effect of breed, the results point to a more intense proteolytic activity in the Assaf breed, whose more matured cheeses showed the highest content of casein proteolytic fragments.