The effect of plasmin activity and cold storage of cheese milk on the composition, ripening and functionality of mozzarella-type cheese

The effects of casein hydrolysis by plasmin on composition, ripening and functionality in mozzarella-type cheese were studied. Milk was stored at 4°C for 0, 24 and 48 h, with and without added plasmin, before batch pasteurization and the manufacturing of mozzarella-type cheese. In parallel experiments, the effects of incubation of milk with added plasmin for 2 h at 37°C prior to cheese manufacture and of an increase in the level of rennet added during cheesemaking were studied. Plasmin addition adversely affected the rennet coagulation properties of the milk and led to increased (two- to three-fold) plasmin activity in cheese and greater plasmin-associated hydrolysis of β-casein to γ-caseins during ripening. Melted cheese flow rate and stretchability increased over ripening and melting time decreased, but functional properties were not affected by eitherplasmin activity or cold storage. Overall, neitherplasmin activity (at the levels studied) nor cold storage greatly affected the composition or functionality of mozzarella-type cheese.