ANTIOXIDANT ACTIVITIES OF SARDINELLE HEADS AND/OR VISCERA PROTEIN HYDROLYSATES PREPARED BY ENZYMATIC TREATMENT

Abstract

ABSTRACT The antioxidant activities of protein hydrolysates prepared from heads and/or viscera of sardinelle (Sardinella aurita) by treatment with different proteases were evaluated using various in vitro antioxidant assays. All hydrolysates showed different degrees of hydrolysis and varying degrees of antioxidant activity. The hydrolysates obtained by treatment with crude enzyme from Mustelus mustelus intestines exhibited the highest radical-scavenging activity. However, Alcalase hydrolysates displayed the greater reducing power activities. Further, sardinelle heads protein hydrolysates were found to strongly suppress the discoloration of β-carotene compared with control. Both Alcalase protein hydrolysates obtained from heads or viscera were then fractionated by size exclusion chromatography on a Sephadex G-25, into two and four major peptide fractions, respectively. All fractions exhibited antioxidant activity, and fraction P4 with molecular mass around 3.5 kDa from sardinelle viscera protein hydrolysates was found to exhibit the highest radical-scavenging activity. PRACTICAL APPLICATIONS In Tunisia, sardinelle (Sardinella aurita) catches were about 13,300 tons in 2002. During processing, solid wastes including heads and viscera are generated and can be seen as 30% of the original raw material. These by-products constitute an important source of proteins. An interesting alternative to valorize these by-products is to transform sardinelle proteins by-products into biologically active peptides by protease treatments. The results clearly demonstrated that sardinelle by-products protein hydrolysates have excellent antioxidant activities, and thus, they have great potential as a source for natural antioxidants.