CONICET | Buscador de Institutos y Recursos Humanos

Flavour development in cheese results from the metabolic activities of cheese bacteria, by glycolysis, proteolysis, lipolysis and citrate metabolism. Enterococcus faecium was the most frequently isolates species from artisanal ewes milk cheese. There are contradictory reports on the influence of enterococci on cheese flavour. However, the beneficial role of enterococci in the formation of cheese flavour has led to the inclusion of enterococci strains in certain starter cultures for different European cheeses. The purpose of the present work was to determine biochemical properties of enterococci, such as acidification ability, proteolytic, lipolytic activity, citrate utilization and diacetyl-acetoin production, which are relevant to development cheese flavour. A total of 8 E. faecium strain isolated from artisanal ewes milk cheese were screened for biochemical properties relevant to flavour production. Strains exhibited low ovine milk acidifying ability. Only E. faecium Ov242 and Ov254 reduced the pH below 5.0 at 12 h of growth. Analysis OPA and APY Zym test showed the enterococci strains exhibited low extracellular proteolytic activity. Important activities (2.3, 2.0, 1.3) of the aminopeptidases of leucine, valine and cystine were recorded for the all enterococci. The lypolytic activities were relatively higher. Postelectrophoretic detection of esterase activities showed an intracellular complex esterolytic system, detecting a maximum of two or three bands per strain. Their esterases released derivatives of short chain fatty acids, with higher specific activities to a-naphtil-butyrate and caproate. The fraction intracellular of all strain hydrolyzed tributyrine and tricapriline. The fraction extraxellular of E. faeium Ov 214 and Ov242 hydrolyzed tributyrine. All strains were able to utilize citrate in complex medium LAPT at 6 h of growth and increased of medium pH of 6.5 to 6.8. The diacetyl and acetoin production in milk was observed for all strains, except for the Ov167 strain. Conclusion: The enterococci strains examined in this study were poor acidifiers in milk, low proteolytic, higher lipolytic activity and showed ability to metabolise citrate. These biochemical properties would allow that E. faecium strains may be usefull as adjunct cultures. The results show that the enterococi possesses a metabolic potential to contribute in the development of cheeses flavour. Key words: ewes milk cheese, flavour, citrate metabolism, lipolysis

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