Optimization of enzymatic protein hydrolysis conditions to obtain maximum angiotensin-I converting enzyme (ACE) inhibitory activity from flower crab (Portunis pelagicus) meat

In this study, optimization of enzymatic protein hydrolysis conditions of flower crab meat (FCM) to yield maximum angiotensin converting enzyme (ACE) inhibitory activity was carried out. First, screening of commercial food grade enzymes (Alcalase®, Neutrase®, Protamex® and papain) was carried out to select the most suitable proteinase to yield ACE inhibitory activity. A 3-level face-centered central composite design (CCD) was employed to optimize four hydrolysis conditions including temperature (45-55°C), hydrolysis time (1-3 hr), pH (6-8) and enzyme to substrate ratio (E/S) (1-3%). Half maximal inhibitory concentration (IC50) of FCM hydrolysate prepared at optimum condition was also determined. It was found that the highest ACE inhibitory activity (85.52%) was given by Neutrase® after 2 hr hydrolysis. Hence, Neutrase® was used in the optimization study. It was found that the enzymatic hydrolysis condition of FCM towards ACE inhibitory activity could be predicted by a quadratic model. The optimum enzymatic hydrolysis condition to obtain maximum ACE inhibitory activity was at temperature of 54°C, E/S of 3%, pH of 7 and hydrolysis time of 1 hr. It was found that the predicted value of ACE inhibitory activity (97.21%) was close to that of experimental value (90.34%) with the IC50of0.425±0.05 mg/ml.