Abstract:The effects of five pretreatments (acid, alkali, heat, ultrasound, and high pressure) on the production of angiotensin-converting-enzyme (ACE) inhibitory peptide from collagen were explored. After pretreatment, collagen was hydrolyzed by Alcalase, and the degree of hydrolysis (DH), ACE inhibitory activity, and the molecular weight distribution of the hydrolysate were measured. Results showed that alkali- and ultrasound-treated groups had higher DH and ACE inhibition rate than the untreated group, which indicated that these two pretreatments can favor exposure of sites in the triple-helical region of collagen. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the structure of collagen, and the results showed that alkali treatment changed the configuration of collagen, affected the balance of non-covalent bonds, and exposed the hydrophobic site completely in the triple-helical region of collagen. However, the integrity of the subunits was maintained. Ultrasound treatment damaged the covalent bonds in the helical region of collagen and exposed more hydrophobic sites, which was helpful for alcalase hydrolysis. In contrast, acid, heat, and high-pressure treatments mostly affected the non-helical region of collagen, and could not promote the release of ACE inhibitory peptide from collagen during enzymatic hydrolysis.
