Doan D Nguyen

Ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS/MS) enables simultaneous identification and quantification of beta-casomorphine 5 (β-CM5) and beta-casomorphin 7 (β-CM7) at the level of ng/mL in milk. This analytical technique uses stable isotope-labeled beta-casomorphin 5 (β-CM5-d10) and beta-casomorphin 7 (β-CM7-d10) to achieve accurate quantitation of target peptides. In addition, solid-phase extraction (SPE) can be used for concentration and purification of milk extracts to improve the limits of detection and quantitation of the method.

Milk proteins including casein are sources of peptides with known bioactivity. One of these peptides is beta-casomorphin (BCM), which belongs to a group of opioid peptides formed from β-casein variants. BCM7 has been demonstrated to be enzymatically released from the A1 or B β-casein variant. Epidemiological evidence suggests the peptide BCM7 is a risk factor for the development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases, but this has not been thoroughly substantiated by research studies. High-performance liquid chromatography coupled to mass spectrometry detection techniques have been used to analyze BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and also in a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yogurts. The finding that BCMs are present in cheese suggests they could also form in yogurt, but be degraded during yogurt processing. Whether BCMs do form in yogurt and the amount of BCM forming or degrading at different processing steps need further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown.