A Model to Assess Lactic Acid Bacteria Aminopeptidase Activities in Parmigiano Reggiano Cheese During Ripening

Effect of single environmental variables (a, pH; b, NaCl concentration; c, temperature) on enzyme activities (EA). Enzyme activities are reported as percentage of the values obtained under most favorable conditions (run 19).

Combined effect of 2 environmental variables (a, temperature and NaCl concentration; b, pH and temperature; c, pH and NaCl concentration) on the PepL enzymatic activity (EA; μmol of β-naphthylamide released per h per mL of sample). The variable not present in each figure is kept constant to its central value (i.e., pH 5.5, NaCl 3.0%, temperature 19°C).

Combined effect of 2 environmental variables (a, temperature and NaCl concentration; b, pH and temperature; c, pH and NaCl concentration) on the PepX enzymatic activity (EA; μmol of β-naphthylamide released per h per mL of sample). The variable not present in each figure is kept constant to its central value (i.e., pH 5.5, NaCl 3.0%, temperature 19°C).

Predicted enzymatic activities of X-prolyl dipeptidyl aminopeptidase (PepX; Δ) and peptidase with high specificity for leucine and alanine (PepL; ■) in 2 different zones of Parmigiano Reggiano cheese wheel during different steps of the cheese ripening at 18°C. Dotted line = internal zone; solid line = external zone.