Corn protein was hydrolysed by three microbial proteases and further separated by sequential ultra-filtration
to 12 hydrolysate fractions which were investigated for free radical scavenging capacity and chelating
activity. The oxygen radical absorbance capacity (ORAC) of the hydrolysates varied significantly
between 65.6 and 191.4 lmoles Trolox equivalents (TE)/g dried weight with a small peptide fraction
(NP-F3) produced by neutral protease (NP) possessing the highest antioxidant activity. The 1,1-diphenyl-
2-picrylhydrazyl radical (DPPH) scavenging activities of the hydrolysate fractions also varied significantly
between 18.4 and 38.7 lmoles TE/g. Two fractions (AP-F2 and AP-F3) produced by alkaline
protease (AP) showed the strongest activity. However, no significant difference was detected on the chelating
activity of the fractions. NP-F3, AP-F2, and AP-F3 were incorporated into ground beef to determine
their effects on lipid oxidation during 15-day storage period. NP-F3 was the only fraction that inhibited
lipid oxidation at both 250 and 500 lg/g levels by as much as 52.9%.