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

Various lactic acid bacteria were blended into freshly-made starter-free 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 numbers and areas of peptide peaks, suggesting differences in proteolytic abilities among species and strains of lactic acid bacteria. Tertiary proteolysis, assessed by spectrophotometric measurements of Cd-ninhydrin 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 proteolysis by starter and non-starter bacteria during cheese ripening may be specific for various species and strains of lactic acid bacteria.