Production and functional characterisation of antioxidative hydrolysates from corn protein via enzymatic hydrolysis and ultrafiltration

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 μmoles 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 μmoles 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 μg/g levels by as much as 52.9%.