DETERMINATION OF THE PEPTIDE SIZE RANGE OF AN EXTENSIVELY HYDROLYZED PROTEIN HYDROLYSATE

FPLC on a Superdex Peptide 10/30 HR column and Vie HPLC-MS-FAB (HPLC-m ass spectrometry with fast atom bombardment) on-line system were compa red for determination of the molecular weights of peptide standards an d an extensively hydrolysed whey protein hydrolysate. FPLC on Superdex Peptide gave rather incorrect molecular weights for small peptide sta ndards. It fractionated the peptides of the whey protein hydrolysate r ather well according to the molecular weight, but all the fractions al so contained small peptides. The HPLC-MS on-line system was a sensitiv e and precise method for small peptides. As the molecular weight of th e analyte increased the ionization of the peptide became more difficul t, which lowered its sensitivity. Preliminary fractionation of the whe y protein hydrolysate with FPLC on Superdex Peptide column and pooling of the fractions separately from successive elutions improved the sen sitivity, and the suppression of some peptides was avoided. HPLC-MS-FA B gave slightly lower molecular weights for the whey protein hydrolysa te fractions than FPLC on Superdex Peptide. The HPLC-MS-FAB results we re well supported by matrix-assisted laser desorption/ionisation time- of-flight mass spectrometry (MALDI-TOF MS) analyses.