Antioxidant activity of fractionated foxtail millet protein hydrolysate

The objective of the study was to assess the antioxidant potential of defatted foxtail millet protein hydrolysates (DFMPH). Gel filtration (Sephadex G-25) chromatography was used to fractionate DFMPH. The amino acid composition, ABTS, DPPH, inhibition of linoleic acid autoxidation, metal-chelating free radical scavenging ability, and reducing power were tested to determine their antioxidant potency. The antioxidant activity of fraction (FIV) (85.71%) was closer to that of α-tocopherol (86.27%) but lower than that of BHT (butylated hydroxytoluene) (92.44%) in the linoleic acid oxidation system. Furthermore, FIV exhibited higher ABTS (2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid), DPPH (1,1-diphenyl-2-picrylhydrazyl) and metal-chelating activity than the other fractions with a significant difference (P < 0.05). Amino acid profile revealed that FIV, with the strongest antioxidant activity, had the highest hydrophobic amino acids content (51.94%) and hydrophobicity (8.62 kJ/moL amino acid residue "AAR"). Molecular weight of the fractions varied from 77-1042 Da. The data obtained by the in vitro systems established antioxidant potency of DFMPH fractions. © 2008 IFRJ, Faculty of Food Science & Technology, UPM.