Technical attribute-based selection of Enterococcus strains for addition to a starter culture for making a ewe's-milk cheese

The use of lactic starters alone does not usually suffice to ensure that cheeses will attain fully satisfactory sensory qualities. There is a need to develop widespread use starter cultures which are individually tailoredto the manufacturing requirements of individual cheeses and contain both lactic acid bacteria and a controlled supplementary flora. The technical attributes of 35 enterococcal strains isolated from ovine milk and Idiazabal cheese have been assayed. The strains belonged to the species Enterococcus durans, E. faecalis, and E. faecium. The attributes considered were acid production, aminopeptidase activity, proteolytic activity, and lipolytic activity. Classification of the strains using principal component analysis (PCA) yielded 3 factors: Aminopeptidase activity was the factor that explained the highest percentage of the variance for the strains. The PCA results also indicated that the strains tested could not be classified by species based on the assays of the attributes considered here. Nine enterococcal strains with low acid production and proteolytic activity levels but high aminopeptidase and lipolytic activity levels were selected.