Wheat germ protein hydrolysates (WGPH) were obtained by enzymatic hydrolysis of defatted wheat germ protein isolates using Alcalase 2.4L FG. The degree of hydrolysis (DH) of WGPH was determined to be about 25% using pH-stat method. The molecular mass distribution of WGPH was lower than 1500 Da. The antioxidant and free radical-scavenging activities of WGPH were investigated by employing several in vitro assay systems, including the linoleic acid emulsion model system, 1,1-diphenyl-2-picrylhydrazyl (DPPH)/superoxide/hydroxyl radical-scavenging, reducing power, and ferrous ion-chelating activity. The antioxidant activity of WGPH was close to that of alpha-tocopherol in a linoleic acid emulsion system. WGPH showed scavenging activity against free radicals such as DPPH, superoxide, and hydroxyl radicals. The radical-scavenging effect was in a dose-dependent manner, and the EC50 values for DPPH, superoxide, and hydroxyl radicals were found to be 1.30, 0.40 and 0.12 mg/mL, respectively. Moreover, WGPH also exhibited notable reducing power and strong chelating effect on Fe2+. The data obtained by the in vitro systems obviously established the antioxidant potency of WGPH. (c) 2006 Elsevier Ltd. All rights reserved.