Structural modification of soy protein by the lipid peroxidation product malondialdehyde

Abstract

AbstractBACKGROUND: Protein oxidation results in covalent modification of structure and deterioration of functional properties of target protein. Oxidation extent of soy protein was affected by the content and type of lipid peroxidation (LPO) products in defatted soybean flours during storage and processing. Malondialdehyde (MDA) was selected as a secondary byproduct of LPO to investigate the effects of oxidative modification of LPO‐derived reactive aldehyde on soy protein structure.RESULTS: MDA reacted with ε‐amino and sulfhydryl groups of soy protein, and resulted in an increase in protein carbonyl groups but a decrease in sulfhydryl/disulfide, free amines and lysine. The decrease in solubility, surface hydrophobicity and intrinsic fluorescence indirectly indicated that MDA induced soy protein aggregation, and results of high‐performance size‐exclusion chromatography directly showed that gradual aggregation of soy protein was induced by increasing concentration of MDA. Results of electrophoresis indicated that MDA caused soy protein aggregation, and non‐disulfide covalent bonds were involved in aggregate formation.CONCLUSION: The results showed that sensitivity of soy protein was related to MDA concentration. Soy protein gradually aggregated with increase of MDA concentration; β‐conglycinin was more sensitive to MDA modification than glycinin. Copyright © 2009 Society of Chemical Industry