CHARACTERIZATION OF THE OLIGOPEPTIDES OF PARMIGIANO-REGGIANO CHEESE SOLUBLE IN 120 G TRICHLOROACETIC ACID L/

The non-protein nitrogen (NPN) of samples of Parmigiano-Reggiano chees e ripened for 6 and 15 months was fractionated by ion-exchange chromat ography on a Cu2+-Chelex column to separate oligopeptides from free am ino acids. Peptide components were isolated by reversed-phase HPLC and identified by fast atom bombardment-mass spectrometry (FAB-MS). Only the NPN fraction of 6 month old cheese samples contained enough peptid es to be further characterized. On the basis of FAB-MS spectral result s, 39 oligopeptides were identified, the main components being phospho peptides. Two sets of both intact and partly dephosphorylated peptides , accounting for a total of 19 phosphopeptides, were formed by the hyd rolysis of p-casein and belonged to regions 1-20 and 6-28 of beta-case in. The formation and potential role of these peptides in cheese is di scussed.