Production of Dual Inhibitory Hydrolysate by Enzymatic Hydrolysis of Squid Processing By-product.

Squid processing by-product contains unutilized abundant proteins. In this study, 6 proteases (pepsin, protamex, trypsin, neutral protease, alkaline protease, and papain) were firstly employed to hydrolyze the squid processing by-product protein. The neutral protease-digested hydrolysate was found to have the most promising ACE (angiotensin-converting enzyme) inhibitory activity. Based on Box-Behnken design, the optimal hydrolysis process was determined to be: 52.4 ℃ of temperature, 5.7 h of time, pH 7.1, and 8151 U/g of enzyme. Under these conditions, the ACE inhibition rate and polypeptide content of the hydrolysate were 84.26% and 229.09 mg/g, respectively. Subsequently, ultrafiltration was performed, and the ACE and renin inhibitory activities of the filtrate (< 1 kDa) were the highest, reaching 87.48 ± 1.76% and 69.72 ± 1.16%, with IC50 values of 1.34 ± 0.12 mg/mL and 1.47 ± 0.06 mg/mL, respectively. However, these activities decreased to 35.15 ± 1.31% and 43.17% ± 1.42%, respectively, after digestion by simulated gastrointestinal juice. Nevertheless, this is the first report representing the neutral protease-digested hydrolysate of squid processing by-product as a potential source of both ACE and renin inhibitors.