Antioxidative and ACE inhibitory activities of protein hydrolysates from the muscle of brownstripe red snapper prepared using pyloric caeca and commercial proteases

Protein hydrolysates from the muscle of brownstripe red snapper (Lutjanus vitta) prepared using Alcalase or Flavourzyme as the first step with 40% degree of hydrolysis (DH), followed by hydrolysis with pyloric caeca protease (PCP) as the second step for 2 (HAP) and 1 h (HFP), respectively, were prepared and determined for their antioxidative and angiotensin I-converting enzyme (ACE) inhibitory activities. HAP had the higher DPPH and ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP), while HFP showed the higher ferrous chelating activity and ACE inhibitory activity (p < 0.05). Both HAP and HFP were able to retard lipid oxidations in lecithin–liposome and β-carotene–linoleic acid oxidation model systems in dose-dependent manner. HAP and HFP contained 87.36 and 86.55% protein (wet basis), respectively with glutamic acid/glutamine as the major amino acids, followed by aspartic acid/asparagine, lysine, alanine and leucine, respectively. HFP showed a slightly greater efficiency in prevention of lipid oxidation in all systems tested. Antioxidative activities, except DPPH radical scavenging activity, of both HAP and HFP after being subjected to gastrointestinal tract model system (GIMs) increased, suggesting the enhancement of antioxidative activities of both hydrolysates after ingestion.