Autolysis of lactobacilli during Cheddar cheese ripening

Experiments were undertaken to determine whether mesophilic lactobacilli un dergo autolysis during Cheddar cheese ripening. Intracellular marker enzyme s (IME), including D-lactate dehydrogenase, prolinase and a proline iminope ptidase, specific to these lactobacilli, were identified to distinguish lys is of the lactobacilli from that of the starter lactococci. Cheese was manu factured with addition of single strains of mesophilic lactobacilli and Lac tobacillus helveticus DPC 4571.. During ripening, the numbers of mesophilic lactobacilli remained high in all cheeses, but the numbers of strain 4571 decreased. The IMEs of the mesophilic lactobacilli could not be detected in the cheese juice and the indicators of proteolysis were similar to that of the control cheese. In the cheese made with the thermophilic strain DPC 45 71, two IMEs, D-LDH and proline iminopeptidase, were detected in the cheese and the indicators of proteolysis were increased. It was concluded that me sophilic lactobacilli do not autolyse during cheese ripening, but strain 45 71 did and that the release of intracellular enzymes influenced proteolysis . When cheese was made commercially with strain 4571, the IMEs were detecte d in the experimental cheese, indicators of proteolysis were increased and the cheese had an improved flavour, relative to a control cheese. This sugg ests that there is a correlation between lysis of Lb. helveticus, increased proteolysis and improved flavour.