Rol of enterococci in development of ewe’s milk cheese flavour from northwest Argentine

MEDINA, R.; ABEIJÓN, C.; KATZ, M.; OLIVER, G. AND GONZÁLEZ, S.

Jaén

Conferencia; Food safety under extreme conditions…a conference on small scale production units of traditional fermented foods; 2004

Universidad de Jaén

  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 ewe’s 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. Post–electrophoretic 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 metabolize 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.