Comparative time-course of lipid and myofibrillar protein oxidation in different biphasic systems under hydroxyl radical stress

This study aimed to investigate the relative reaction rate of protein and lipid oxidation in different biphasic model systems (linoleic acid; liposome; emulsion) containing myofibrillar protein (MFP at 1, 8 and 20 mg/mL) under hydroxyl radical stress. Protein oxidation markers exhibited significant changes in 2 h: reduced tryptophan fluorescence intensity, carbonyl formation, and extensive polymerization of myosin. In contrast, no detectable changes (P >.05) in lipid peroxide occurred within 2 h except for samples with 1 mg/mL MFP which showed an early TBARS formation. Of the three biphasic systems, the oxidative stability of lipids followed the order of emulsion > linoleic acid > liposome, indicating the steric role of proteins. In general, MFP was more susceptible to radicals than lipids, and a higher protein:lipid ratio was associated with a slower TBARS production and more rapid protein oxidation, suggesting a sacrificing role of MFP to protect lipids.