Kasran, M.¹*, Mohamed, N.² and Ishak, Z.¹

Abstract
Protein hydrolysates were produced from black tilapia protein isolate. The degree of hydrolysis was determined and antioxidant and antihypertensive properties of protein hydrolysates were evaluated. Protein solubility was tested within pH range between 3 to 8 before protein extraction. Black tilapia proteins were most insoluble at pH 5.2 and hence proteins were extracted at pH 5.2. SDS-PAGE electrophoretogram showed black tilapia having molecular weight ranging from 10 to 150 kDa. Amino acids analysis revealed that there were no significant difference of the individual amino acids in protein isolate and protein hydrolysates/100 g protein where glutamic acid was the most abundant. The degree of hydrolysis of black tilapia reached an optimum value after 4 h of hydrolysis. The ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays were used to determine the antioxidant properties of protein hydrolysates. Antihypertensive activity of protein hydrolysates was performed via angiotensin converting enzyme (ACE) inhibitory activities. In vitro, the bioactivity of these hydrolysates showed high antioxidant activity (DPPH inhibition, 90% with IC50 value of 0.47 mg/mL and FRAP value, 166 mM Fe(II)/g dry wt. sample) while anti-hypertension activity (ACE inhibitory activity) was 81%. The results showed black tilapia protein hydrolysates exhibited antioxidant and antihypertensive activities.

Keywords: protein extraction, protein hydrolysates, DPPH, FRAP, ACE inhibitory

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