Abstract: In order to investigate the effect of oxidative modification with reactive aldehyde on the structural and emulsifying properties of walnut protein, acrolein (0–1 mmol/L) was selected as a representative secondary byproduct of lipid peroxidation induced by lipoxygenase (LOX) for incubation with walnut protein. The results showed that the carbonyl content of walnut protein significantly increased from 4.287 to 11.078 nmol/mg with increasing aldehyde concentration, accompanied by a decrease in free sulphydryl and total sulphydryl by 55.18% and 31.13%, respectively suggesting that acrolein caused significant changes to walnut protein. The solubility of walnut protein decreased by up to 84% with the increase in its degree of oxidation, and the surface hydrophobicity declined from 469.47 to 412.22; the contents of α-helix and β-sheet increased, while the contents of β-turn and random coil decreased. In addition, the emulsifying capacity and emulsion stability of walnut protein decreased from 46.87 to 9.86 m2/g and from 25.93 to 17.63 min, respectively. All of these results indicate that acrolein can lead to oxidative structural modification of walnut protein, thus causing damage to the emulsifying properties of the protein.

Key words: acrolein, protein oxidation, walnut protein, structure, emulsifying properties