PROTEOLYTIC ABILITIES OF SOME LACTIC-ACID BACTERIA IN A MODEL CHEESE SYSTEM

Various lactic acid bacteria were blended into freshly-made starter-fr ee Cheddar-type cheese (acidified with glucono-delta-lactone) to form slurries that were ripened anaerobically at 32 degrees C for five days . Reversed-phase HPLC analysis of the water-soluble nitrogen extracts from the slurries (secondary proteolysis) showed differences in the nu mbers and areas of peptide peaks, suggesting differences in proteolyti c abilities among species and strains of lactic acid bacteria. Tertiar y proteolysis, assessed by spectrophotometric measurements of Cd-ninhy drin colour yields of the water-soluble nitrogen extracts also showed differences in the concentrations of free amino acids produced by the different lactic acid bacteria. Results suggest that casein proteolysi s by starter and non-starter bacteria during cheese ripening may be sp ecific for various species and strains of lactic acid bacteria.