Abstract
•In vitro digestion of casein from A1/A2 milk releases BCM-7 at physiological timeframes.
•Significantly less BCM-7 is released when A2 milk is digested.
•Pepsin, pancreatin and LAP enzymes are essential to produce a BCM-7 rich digest fraction.
•LAP is essential to promote cleavage of the N-terminal valine promoting enhanced release of BCM-7.
Gastrointestinal (GI) digestion of bovine milk promotes release of biologically active peptides, including β-casomorphins (BCMs). Previous studies demonstrate release of BCM-7 by digestion of A1 β-casein (β-CN), but the conditions required to increase the amount of BCM-7 released during digestion are unclear. In this study, a simple in vitro digestion method employing pepsin, pancreatin and leucine aminopeptidase (LAP) enzymes was used to digest CN isolated from regular and A2 milk. LC-MS analysis revealed that CN isolated from regular milk digested with pepsin-pancreatin released BCM-7 and Val-BCM-7 over time. Additionally, LAP, which cleaves the N-terminal valine, increased the yield of BCM-7. In contrast, significantly less BCM-7 and Val-BCM-7 were released by digestion of CN isolated from A2 milk. This simple method for digesting bovine casein can now be used to provide a platform for future work aimed at better understanding the reported gut health benefits of A2 compared to A1 milk.