Optimisation of enzymatic protein hydrolysis of mud crab (Scylla sp.) to obtain maximum antioxidant activity using response surface methodology

Abstract

This study reported optimisation of enzymatic hydrolysis of mud crab meat using Protamex® to obtain maximum antioxidant activity using Response Surface Methodology (RSM). Prior to optimisation, screening of commercial food grade proteinases was carried out using Alcalase®, Protamex®, Neutrase® and papain. Protamex® was observed to give the highest DPPH scavenging activity. The enzymatic hydrolysis conditions used in the optimisation study were temperature (45-65ºC), pH (5.5-7.5), hydrolysis time (1-4 hours) and enzyme to substrate (E/S) ratio (1-3% Protamex®). A face-centered Central Composite Design (CCD) was employed. It was found that the relationship between hydrolysis conditions and DPPH scavenging activity could be explained by a quadratic model. Optimum condition was found to be at 54ºC, pH 5.5, 1% Protamex® and 1 hour of hydrolysis time. Validation experiment shows that the experimental DPPH scavenging activity (82.39 ± 0.16%) was close to the predicted value (82.64%). The hydrolysate prepared at optimum condition contained 5.52% moisture, 74.81% crude protein, 13.13% ash, 6.26% carbohydrate and 0.28% crude fat with IC50 for DPPH scavenging activity of 3.48 ± 0.05 mg/mL. This study shows that RSM can be used to explain the relationship between enzymatic hydrolysis conditions of mud crab meat and its antioxidant activity.