Twelve kinds of food proteins were hydrolyzed by Bacillus licheniformis alkaline proteases to form peptides of average chain length, 2.26-4.02. The hydrolyzates from shrimp, crab and sardine contained many di- and tri-residues whose angiotensin I converting enzyme (ACE) inhibitory activities were stronger than that of the hydrolyzates from soy bean, hair tail, oyster, beef, chicken, pork, chicken egg yolk, chicken egg white and casein. The IC50 was 0.072, 0.075 and 0.076 mg protein/ml, respectively. Hydrophobic amino acid residues situated in the interior of protein molecules were exposed by fragmentation with proteases, and the peptides containing hydrophobic amino acid residues were found in aqueous solution. The peptide from casein showed the highest hydrophobicity and whose taste was the most bitter.
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