Antioxidant Activities of Okra Protein Concentrate and Isolate after Enzymatic Hydrolysis

Abstract

Three different proteolytic enzymes (pepsin, trypsin and papain) were used to prepare okra seed protein concentrate and okra seed protein isolate hydrolysates. The hydrolysates were assayed for antioxidant properties using radical scavenging, reducing power and metal chelating assays. The highest degree of hydrolysis (after 360 min) for okra protein isolates was 35.20%, 35.21% and 10.53% for pepsin, papain and trypsin respectively. The highest degree of hydrolysis (after 360 min) for okra protein concentrates was 26.8%, 28.59% and 6.47% for pepsin, papain and trypsin respectively. Pepsin hydrolysates showed higher metal chelating activity and radical scavenging activity than trypsin and papain hydrolysates. Trypsin hydrolysates showed the lowest antioxidant activities, which may be due to the low degree of hydrolysis. In general, for antioxidant activity, there was an increase in activity with an increase in the degree of hydrolysis. Similar antioxidant activity was found in both the okra protein isolate and concentrate hydrolysates except for metal chelating activity which was higher in okra protein isolate hydrolysates. This may be due to the higher ash concentration in the concentrates (9.4% in concentrates vs. 2.6% in isolates). In this study, pepsin hydrolysates with a final DH of 35.2% showed higher reducing power and metal chelating activity than trypsin and papain hydrolysates. Okra protein hydrolysates were found to have varying levels of antioxidant activity, which was dependent on the specificity of the protease and proportional to the degree of hydrolysis achieved.