Caseinolysis in cheese by Enterobacteriaceae strains of dairy origin

AIMS: To study the effect of Enterobacteriaceae strains of dairy origin on caseins under cheese manufacture and ripening conditions. METHODS AND RESULTS: Strains belonging to the genera Enterobacter, Escherichia, Hafnia and Serratia were isolated from fresh raw milk cheeses. Residual caseins in cheeses made from milk individually inoculated with 10 strains of Enterobacteriaceae were determined by capillary electrophoresis. Hierarchical cluster analysis of strains based on data of residual caseins grouped together strains from the same genus, excepting Hafnia strains, which were separated into two groups. Serratia was the most proteolytic genus in our study. Preferences for degradation of casein fractions differed among the four genera studied. CONCLUSIONS: Enterobacteriaceae strains posses proteolytic systems active on all casein fractions under cheese manufacture and ripening conditions. The effects on caseins were similar for strains belonging to the same genus. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of Enterobacteriaceae in cheeses may affect proteolysis during ripening. Assays of Enterobacteriaceae proteolytic activity on milk agar plates may underestimate their caseinolytic activity in cheese.