The aim of this study was to investigate the possible mechanism for increasing the antioxidant activity on peptide Glutamine‐Tryptophan‐Phenylalanine‐Histidine (QWFH) from pine nut (Pinus koraiensis) protein by a pulsed electric field (PEF). The antioxidant capacity of PEF‐treated QWFH increased significantly (p < 0.05) through 1,1‐diphenyl‐2‐pycryl‐hydrazyl radical scavenging and oxygen radical absorbance capacity assays. A series of mechanism exploration methods, including reversed‐phase high‐performance liquid chromatography, ultraviolet absorption spectroscopy, intrinsic fluorescence spectra, circular dichroism spectroscopy, and 1D and 2D nuclear magnetic resonance spectroscopies, were applied. QWFH chain was not cleaved by the PEF treatment, while more aromatic amino acids (Trp and Phe) were exposed to the polar solvent. In addition, the content of random coil of QWFH in solution was increased and its active hydrogen was changed after the PEF treatment. Moreover, the long‐range connectivity between OH (14.234 ppm) on 4‐H His, NαH (7.295 ppm) on 3‐H Phe, and NαH2 (6.801 ppm) on 1‐H Gln disappeared due to the PEF. Practical applications Antioxidants have been extensively explored as a potential drug to decrease the risk of certain chronic diseases. Food‐derived bioactive compounds are safer than synthetic antioxidants for human health and well‐being. And the PEF technology is one of the promising processes for improving the biological activity of food components. Currently, the activity of the antioxidant peptide QWFH increased after a PEF treatment. The basic structure of QWFH did not change, but the unfolding of the secondary structure on the peptide chain and the displacement of the active hydrogen increased the antioxidant activity of the peptide. Thus, the range of application of a PEF has been expanded and it also benefited the development of more functional factors in the functional food industry.

PEF treatment increased peptide linkage stretch vibration and altered hydrogen bonding of KCHKP. The stability of the α-helix structure was influenced by hydrogen bonds within the peptide linkage of KCHKP induced by PEF and was related to changes in antioxidant activity. © 2017 Society of Chemical Industry.

Information on antioxidant peptides derived from corn germ meal (CGM) is seldom reported. In this paper, three novel antioxidant peptides including Met–Gly–Gly–Asn (MGGN; 377.42 Da), Met–Asn–Asn (MNN; 377.42 Da), and Met–Glu–Asn (MEN; 392.43 Da) were purified from the most active fractions of corn germ meal hydrolysate, and their activity was evaluated by radical scavenging, oxygen radical absorbance capacity, cellular antioxidant activity (CAA), and intracellular reactive oxygen species scavenging assays. MNN had a higher value for the CAA assay (1,213.79 μmol of QE/100 mmol) and could be most effective in preventing conditions favorable to intracellular oxidative stress. Finally, electron paramagnetic resonance spectroscopy directly verified the above experimental results by measuring the number of •OH trapped in the system. Thus, CGM could be considered as a potential source of antioxidant peptide and MNN might be regarded as a natural antioxidant. Practical applications CGM is a by‐product of corn industrial that includes ground corn germ and other parts of the corn kernel. In the past, some of them were discarded by factories in China. In this study, three novel antioxidant peptides were isolated from the hydrolysate of CGM, which greatly increased its economic value. In addition, these peptides have huge potential to serve as antioxidants in pharmaceutical, cosmetic, and functional food industries.