THE ROLE OF STARTER PEPTIDASES IN THE INITIAL PROTEOLYTIC EVENTS LEADING TO AMINO-ACIDS IN GOUDA CHEESE

The initial proteolytic steps in Gouda cheese leading to amino acid ni trogen (AN) have been found to reflect the essential action of the cel l-bound, cell-envelope proteinase (CEP) of lactococci on the primary p roduct of chymosin action on alpha(sl)-casein, fragment 1-23 (alpha(sl )-CN(f1-23)) as observed in vitro under cheese conditions. In the abse nce of CEP, alpha(sl)-CN(f1-23) accumulates in cheese and the producti on of AN falls. In such a cheese, only a slow conversion of alpha(sl)- CN(f1-23), catalysed by an intracellular endopeptidase, could be detec ted. In the presence of CEP, the early appearance in cheese of product s of the action of this endopeptidase indicates significant early lysi s of cells. The distinct specific actions of different types of CEP, c haracteristic of different lactococcal strains, on alpha(sl)-CN(f1-23) in vitro are also recognized in cheese and therefore CEP may be expec ted to direct further proteolysis to some extent. Increasing salt conc entration in the cheese moisture does not influence initial alpha(sl)- casein conversion but inhibits the subsequent conversion of alpha(sl)- CN(f24-199), as well as AN production in cheese significantly. Dehydra tion of the rind additionally influences proteolysis negatively. The i mportance of initial alpha(sl)-casein conversion and degradation of al pha(sl)-CN(f1-23) for the development of flavour in cheese is discusse d.