Uncommonly Thorough Hydrolysis of Peptides during Ripening of Ragusano Cheese Revealed by Tandem Mass Spectrometry
2011
Gagnaire, Valérie | Carpino, Stefania | Pediliggieri, Concetta | Jardin, Julien | Lortal, Sylvie | Licitra, Giuseppe
Ragusano is a pasta filata cheese produced from raw milk in Sicily. The proteolysis was extensively analyzed after stretching (day 0), at 4 and 7 months of ripening through soluble nitrogen, urea-PAGE, and peptide identification by tandem mass spectrometry. After stretching, 123 peptides were identified: 72 arising from beta-casein, 34 from alphas1-casein, and 17 from alphas2-casein. The main protein splitting corresponded to the action of plasmin, chymosin, cathepsin D, cell envelope proteinase, and peptidase activities of lactic acid bacteria. Unlike other types of cheeses, <10% residual beta- and alphas-caseins remained intact at 7 months, indicating original network organization based on large casein fragments. The number of identified soluble peptides also dramatically decreased after 4 and 7 months of ripening, to 47 and 25, respectively. Among them, bioactive peptides were found, that is, mineral carrier, antihypertensive, and immunomodulating peptides and phosphopeptides.
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