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-pe rformance liquid chromatography (RP-HPLC) for separation of peptides. Fract ions were subjected to electrospray ionization mass spectrometry (ESI-MS) f or molecular weight (MW) determination and mass spectrometry/mass spectrome try (MS/MS) was used for amino acid sequence determination. The combination of MW and amino acid sequence was used for peptide identification. Peptide s were compared with the known sequences of casein peptides and cleavage si tes were identified. These techniques resulted in the confirmation of 13 pe ptides from alpha(s1)-casein, seven from beta-casein and five from kappa-ca sein. No peptides corresponding to alpha(s2)-casein were identified. (C) 19 98 Elsevier Science Ltd. All rights reserved.