CONICET | Buscador de Institutos y Recursos Humanos

Lipolysis is an important biochemical event occurring during cheese ripening and has been studied quite extensively in varieties such as Blue and hard Italian cheeses where lipolysis reaches high levels and is a major pathway for flavour generation by release of fatty acids(1). E. faecium was the most frequently isolated species from artisanal ewes milk cheese from Argentine (2). The contribution of enterococci presence in matured cheeses on development of good and acceptable flavour or not, is still debated. The present work evaluates the contribution of E. faecium strains to lipolysis of ewes milk cheese. In order to achieve this aim, we followed the lipolysis during the ripening of miniature cheeses under controlled microbiological conditions made from ewes milk by quantification of free fatty acids (FFAs), and we analyses the esterases and lipases activities. The cheeses were made with two strains: E. faecium O227 (A) and E. faecium O214 (B) and we compared the association between Enterococcus strains (C). At the start of ripening, the cheese A presented 1,404 g/Kg of FFAs and increased by 1.2 times at the end of ripening (30 d old). FFAs of cheese B increased 1.56 times and cheese C 4.41 times (6.46 g/Kg) at the end of ripening. The ratio of long chain FFAs (C16-18) decreased in cheese A from 73% to 59.32%, in cheese B from 87% to 67% and C from 85 to 83%; whereas the ratio of short chain FFAs increased from 4% to 9.7%, 3.2% to 6.2% and 1.4 to 2.2% in cheese A, B and C, respectively. Studies on esterase and lipase activities using a-naphtyl derivatives of fatty acids shown that E. faecium O214 present 3 esterases (E1: Rf= 0.53, E2: Rf= 0.57; E3 Rf= 0.77) that released derivatives of short chain fatty acids . The specific activities were: C3= 2.60 ± 1.44 U/mg; C4= 0.205 ± 0.021U/mg and C6= 2.21 ± 0.26 U/mg. E. faecium O227 presented 3 esterases ( E1: Rf= 0.27, E2: Rf= 0.54; E3 Rf= 0.63) that released derivatives of short chain fatty acids. No activities were detected on derivatives of longer chain fatty acids. Our results showed different amounts of FFAs released according to enterococci strains used in make of cheese. The FFAs content depended thus mainly on the Enterococcus strain activity. The strains contribute to lipolysis of ewes milk cheese and the interaction of them increased the release of short FFAs, which contribute to flavour. Key words: lipolysis, ewes milk cheese, flavour.

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