Peptides identified during emmental cheese ripening: Origin and proteolytic systems involved

To determine the proteolytic changes occurring during Emmental cheese ripen ing, peptides released in cheese aqueous phase were analyzed by reversed-ph ase HPLC and identified by tandem mass spectrometry sequencing, for which d ifferent strategies were illustrated by some examples. Among the 91 peptide s identified, most of them arose from alpha (s1)- (51) and beta -caseins (2 8), and a few arose from alpha (s2)- (9) and kappa -caseins (1). An attempt was made to correlate the released peptides with the proteolytic systems p otentially involved during Emmental cheese manufacture. Besides the well-kn own action of plasmin on beta- and alpha (s2)-caseins, and in the absence o f residual fungal coagulant from Endothia parasitica, two other proteinases seem to be involved in the hydrolysis of alpha (s1)-casein in Emmental che ese: cathepsin D originated from milk and cell-envelope proteinase from the rmophilic starters. Moreover, peptidases from starters were also active thr oughout ripening, presumably like those from nonstarter lactic acid bacteri a, in contrast to those from propionic acid bacteria.