Effects of Oxidation by Malondialdehyde On the Structure and Function of Rice Bran Protein

The effect of malondialdehyde (MDA) as a representative reactive secondary oxidation product from lipid peroxidation reaction on the structure and functional properties of rice bran protein (RBP) as well as its structure-activity relationship was investigated by means of the theory of protein chemistry and spectroscopies. It was found that the carbonyl content of RBP increased with increasing MDA concentration, while the free amino content decreased gradually. Besides, the α-helix and β-sheet content of oxidized RBP increased with MDA concentration, whereas the opposite was true for the random coil and β-turn. The maximum absorption wavelength (λmax) of oxidized RBP was blue-shifted. The subunit composition of RBP was not significantly affected by low concentrations of MDA. With increasing the MDA concentration, the intensity of bands near 53, 49, 36, 21 and 14 kDa all decreased and the color became lighter; the 36, 21 and 14 kDa bands gradually disappeared. Increasing MDA concentration led to higher, particle size, polydispersity index (PDI), turbidity and foam stability but lower solubility, surface hydrophobicity, emulsifying capacity, emulsion stability and foamability of oxidized RBP. © 2019, China Food Publishing Company. All right reserved.