Mass mapping analysis as a tool for the identification of genetic variants of bovine β-casein

Matrix-assisted laser desorption ionisation time-of-flight mass spectrometric analysis of the tryptic digest of β-casein A2 and β-casein B was performed before and after the separation of the peptides by LC. The overlapping of the chromatograms showed that all peaks were present in both samples, except for one only found in the tryptic digest of the A2 variant and two in the B variant. Experimental masses could be assigned to those peptides produced by tryptic digest of β-casein variant. This peptide mapping strategy and current methodological improvements represent a promising tool for the identification of milk genetic variants with the difference of an amino acid substitution.