Extraction of protein and antioxidant and antihypertensive properties of protein hydrolysates derived from black tilapia (Oreochromis placidus)

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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