Study on Mechanism of Soy Protein Oxidation Induced by Lipid Peroxidation Products

Oxidative modification of soy protein by lipid peroxidation products, which was potentially present in a lipoxygenase-catalyzed polyunsaturated fatty acid peroxidation system, was investigated in this study. 13SHydroperoxy- 9Z, 11E-Octadecadienoic acid (HPODE), malondialdehyde and acrolein were selected as representative primary product and secondary byproducts of lipid peroxidation and 2, 2'-azobis-(2-amidinopropane) dihydrochloride (AAPH) -derived peroxyl radical peroxyl radicals were chosen to simulate lipid peroxidationderived free radical. Incubation of soy protein with increasing concentration of AAPH, HPODE, malondialdehyde and acrolein resulted in gradual generation of protein carbonyl derivatives, loss of free sulphydryl groups, total sulphydryl groups, free amine, available lysine, surface hydrophobicity and formation of oxidation aggregates. The average distribution model of protein accessible groups could explain majority mechanism of lipid peroxidation products-mediated soy protein oxidation. Primary oxidation aggregates further developed into insoluble aggregates by covalent cross-linking also may provide a partial mechanism of lipid peroxidation products-mediated soy protein oxidation.