Effect of Hydroxyl Radical-Induced Oxidation on Gel Properties of Silver Carp Myofibrillar Protein

In this study, silver carp myofibrillar protein (MP) was oxidized with different concentrations of H₂O₂ (0.0-10.0 mmol/L) in the Fenton system (H₂O₂-VC-FeCl₃) to explore the effect of oxidation degree on protein gel formation and gel properties. The sulfhydryl content of MP was measured. The gel strength, whiteness, water-holding capacity, moisture distribution and microstructure of MP gels were determined. The results showed that as H₂O₂ concentration increased, the total sulfhydryl content, whiteness and water-holding capacity of MP increased first and then decreased. When the H₂O₂ concentration in the system was low (0.1-0.5 mmol/L), the gel strength and whiteness were both improved. The area of pores in the three dimensional gel structure became smaller, the distribution became more uniform, and the water-holding capacity of MP gels was enhanced. However, at high H₂O₂ concentration (5.0-10.0 mmol/L), the gel whiteness decreased, and the gel structure became disordered, the pore area became larger, the pore distribution became nonuniform, and the water-holding capacity decreased, indicating a deterioration in gel quality. Therefore, appropriate oxidation (0.1-0.5 mmol/L H₂O₂) contributed to the improved properties of protein gels. The analysis of the peptide composition by liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed that the major oxidation regions of MP by hydroxyl radicals were the heavy chain of myosin and actin. Moreover, methionine, cysteine, aspartic acid and glutamic acid were recognized as the high-frequency oxidation sites of MP.