COMBINED HIGH-RESOLUTION CHROMATOGRAPHIC TECHNIQUES (FPLC AND HPLC) AND MASS SPECTROMETRY-BASED IDENTIFICATION OF PEPTIDES AND PROTEINS IN GRANA-PADANO CHEESE

The 0.2 mol/L trisodium citrate soluble N fraction of 14- and 38-month -old Grana Padano (GP) cheese diafiltered through 3- and 10-kDa cut-of f membranes gave two fractions containing peptides with a molecular ma ss lower than 3 kDa, and higher than 10 kDa. 91 and 38 oligopeptides l ower than 3 kDa were identified by using a combination of fast-atom bo mbardment/mass spectrometry and Edman degradation in the 14- and 38-mo nth-old GP cheese samples respectively. Peptides higher than 10 kDa we re submitted to preparative fractionation on Mono Q column with a step wise ionic strength gradient and then by reverse phase-HPLC on a C4 co lumn. Some native caseins and large-derived peptides were identified b y using a combination of electrospray mass spectrometry and Edman degr adation.