Identification of bioactive peptides and quantification of β-casomorphin-7 from bovine β-casein A1, A2 and I after ex vivo gastrointestinal digestion

This study investigated whether different genetic variants of beta-casein (beta-CN) give rise to different bioactive peptides during digestion. beta-CN was purified from bovine milk of genetic variants Al, A2 and I, and digested with human gastrointestinal juices in a static ex vivo model. Mass spectrometry analyses revealed that the peptide (60)YPFPGPIPN(68) was exclusively identified from variants containing proline at position 67. Most strikingly, the opioid peptide beta-casomorphin-7, (60)YPFPGPI(66), was identified from both variants Al and A2 after simulated digestion, though with concentration being somewhat higher after digestion of the variant Al, compared with variants A2 and I. The peptides (HLPLP138)-H-134 and (LHLPLP138)-L-133 were both identified after initial 5 min of duodenal digestion. In conclusion, genetic variation of beta-CN may affect proteolysis during digestion; however, the release of beta-casomorphin-7 (BCM7) does not seem to be linked solely to variant Al, as earlier suggested by relevant published literature on in vitro digestion. (C) 2017 Elsevier Ltd. All rights reserved.