Separation of angiotensin I ‐converting enzyme inhibitory peptides from bovine connective tissue and their stability towards temperature, p H and digestive enzymes

Summary Bovine collagen was isolated from connective tissue, a by‐product in the meat processing industry and characterised by SDS ‐ PAGE . Alcalase and papain were employed to generate collagen hydrolysates with different degree of hydrolysis ( DH ). In vitro angiotensin I‐converting enzyme ( ACE ) inhibitory activities were evaluated and the two most potent hydrolysates from each enzyme were separated by two‐step purification. Both alcalase‐catalysed and papain‐catalysed hydrolysates exhibited strong ACE inhibitory capacities with IC 50 values of 0.17 and 0.35 mg mL −1 , respectively. Purification by ion‐exchange chromatography and gel filtration chromatography revealed higher ACE inhibitory activities in one fraction from each enzyme with IC 50 values of 3.95 and 7.29 μg mL −1 . These peptide fractions were characterised as 6‐12 amino acid residues by MALDI‐TOF/MS. The peptides retained their activity (>90%) after exposure to processing temperature and pH and in vitro simulated gastrointestinal digestion. The present results demonstrated that collagen peptides can be utilised for developing high value‐added ingredients, for example ACE inhibitory peptides.