Proteolysis of beta-casein as a marker of Grana Padano cheese ripening

Proteolysis has a critical role in defining the typical organoleptic charac teristics of Grana Padano, a well-known Italian cheese. During the ripening process, hydrolysis of beta -casein produces different fragments, the most abundant and widely studied of which are gamma -caseins, three polypeptide s containing the HOOC-terminal portion of beta -casein. By sodium dodecyl s ulfate-PAGE and a specific anti-beta -casein monoclonal antibody, two beta -casein-derived bands were identified in Grana Padano cheese: beta (a) and beta (b). Thanks to the identification of the amino acid sequences, it was shown that: a) beta (a) contains gamma (1)-casein [beta -casein (29-209)] a nd the correlated peptide [beta -casein (30-209)]; b) beta (b) contains gam ma (2)-casein [beta -casein (106-209)] and gamma (3)-casein [beta -casein ( 108-209)]. The production of beta (a) and beta (b) by the three enzymes most involved in cheese proteolysis (pepsin, chymosin, and plasmin) was evaluated by perf orming in vitro digestions. A significant correlation between abundance of some polypeptides and ripening process was shown.