Effect of Thermal Processing on the Release of Beta Casomorphins-7 during simulated in-vitro Digestion of A1 and A2 Milk

Abstract

The study evaluated the influence of genetic variants and thermal processing on the release of β-casomorphins-7 (BCM-7) during simulated in-vitro digestion. Cross-bred Karan Fries bovine animals were segregated into A1A1 and A2A2 genotypes for the procurement of pure A1 and A2 milk. BCM-7-like peptides were detected only after gastrointestinal digestion from both genotypes, using reverse-phase high-performance liquid chromatography (RP-HPLC). The concentration of these peptides was 74-146ng/mL in digestive extracts of A2 variants, which was significantly lower than 900-1612 ng/mL in A1 variants. Pasteurization led to a reduction in peptide levels to 46-79ng/mL and 340-1132ng/mL in extracts from A2 and A1 variants, respectively. Upon sterilization, a marked decrease in peptide formation was observed, 84.79% in A1 and 84.56% in A2 milk. This indicated a strong negative correlation between heat severity and BCM-7-like peptide formation. Mass spectrometry analysis of selected RP-HPLC fractions confirmed the presence of BCM-7-like peptides in both variants, with a higher specificity toward histidine at position 67 compared to proline.