Identification and quantification of native beta-casomorphins in Australian milk by LC-MS/MS and LC-HRMS

Beta-casomorphin 5 (BCM5) and beta-casomorphin 7 (BCM7) in 14 commercial pasteurised milks from around Australia were investigated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-high resolution (Orbitrap) mass spectrometry (LC-HRMS). Collision induced dissociation HRMS was used to confirm the presence of BCM7 in milk extracts. The accurate mass-to-charge ratio ( m/ z) and relative abundance of BCM7 parent ion and fragments in milk extracts matched with those obtained from the analysis of a BCM7 standard solution. The deviation against the theoretical values of the measured m/ z of BCM7 (parent ion and fragments) all gave results below 5. ppm (relative error). BCM5 was below limit of detection (LOD) for all milks, while BCM7 was between 0.13 and 2.38 ng/g in 10 milks and below LOD in the others. Pasteurised milks containing the highest and lowest BCM7 levels were produced in Western Australia