Characterization and determination of casein glycomacropeptide in dairy products by UHPLC–MS/MS based on its characteristic peptide.

• UHPLC-MS/MS method was applied to detect casein glycomacropeptide in dairy products. • Characteristic peptide was qualitatively confirmed by high-resolution mass spectrometry. • Labeled amino acid condensation method was used to get isotope-labeled characteristic peptides. • The oxidation conditions (oxidant concentration, temperature, and time) were optimized. The ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method was built to quantify the casein glycomacropeptide (CGMP) in bovine dairy products accurately based on targeted proteomics. Qualitative analysis of theoretical peptides was carried out using high-resolution mass spectrometry (HRMS) and protein software. Isotope-labeled characteristic peptides were acquired via the labeled amino acid condensation method to correct the matrix effects. Peptide MAIPPK was the representative characteristic peptide for distinguishing the CGMP from κ -casein through trypsin digestion. After optimizing the pre-treatment conditions, the final 8% oxidant concentration was selected and the 10% formic acid concentration with 2.5 h oxidation time. Moreover, the results of methodological verification showed that the recovery rate was 103.7%, meanwhile the precision of inter-day and intra-day was less than 5%. In conclusion, the research demonstrated the characteristic peptide MAIPPK could quantitatively applied to detect CGMP in dairy products. [ABSTRACT FROM AUTHOR]