Enzymatic Hydrolysis Optimization for Preparation of Tuna Dark Meat Hydrolysate with Antioxidant and Angiotensin I-Converting Enzyme (ACE) Inhibitory Activities

Abstract

The hydrolysates of tuna dark meat with high angiotensin I-converting enzyme (ACE) inhibitory and antioxidant activities were prepared using three enzymes. The effect of concentration (0.5–3.0%, w/w) and hydrolysis time (30–180 min) on yield, degree of hydrolysis (DH), ACE inhibitory activities, and antioxidant capacity was determined. The optimum conditions were the same: 180 min extraction while the concentration of alcalase, neutrase, and flavourzyme were 2.43, 2.62, and 2.62% (w/w), respectively. The hydrolysate resulted in the range of 36.5–50.0% for DH, 5.79–7.71% for yield, 0.29–1.11, 0.28–0.53, and 0.24–0.31 mg/mL IC50 values with 2,2-diphenyi-l-picrylhydrazyl radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and ACE inhibitory activity, respectively, and 0.41–1.35 FeSO4/g for ferric reducing antioxidant power (FRAP). The hydrolysates showed high solubility. Emulsion stability and emulsifying activity index decreased, while foam stability and expansion increased with increasing concentration. Hydrolysates using flavourzyme were fractioned using ultrafiltration membranes. The <1 kDa fraction had significantly higher ACE inhibitory and antioxidant activities.