Identification of peptides in cheddar cheese by electrospray ionization mass spectrometry

Extracts of defatted mild, medium and sharp Cheddar cheese and a commercial Cheddar cheese flavor preparation were subjected to reversed-phase high-performance liquid chromatography (RP-HPLC) for separation of peptides. Fractions were subjected to electrospray ionization mass spectrometry (ESI-MS) for molecular weight (MW) determination and mass spectrometry/mass spectrometry (MS/MS) was used for amino acid sequence determination. The combination of MW and amino acid sequence was used for peptide identification. Peptides were compared with the known sequences of casein peptides and cleavage sites were identified. These techniques resulted in the confirmation of 13 peptides from alpha(s1)-casein, seven from beta-casein and five from kappa-casein. No peptides corresponding to alpha(s2)-casein were identified. (C) 1998 Elsevier Science Ltd. All rights reserved.