The effect of two-stage heating mode on the properties of silver carp surimi gel added with glucose oxidase (GOD) was studied. The results showed that at the gelation stage, the gel strength, water-holding capacity, whiteness and immobile water content of surimi were the highest under the high-temperature short-time (40 ℃/1 h) mode, and the free water content was the lowest, and the gel network formed was the most compact. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern showed that the strength of myosin heavy chain (MHC) was reduced under the high-temperature short-time mode, suggesting that the protein was degraded more under this condition. At the maturation stage, microwave heating provided the highest gel strength, water-holding capacity and whiteness and the smallest trichloroacetic acid (TCA)-soluble peptide content, free water content and equivalent pore size, and resulted in the formation of an orderly and dense three-dimensional network. The SDS-PAGE pattern showed that compared with water bath heating, the intensity of MHC was higher under microwave heating, suggesting that microwave heating promotes the formation of disulfide bonds. Therefore, a suitable heating mode can improve the quality of surimi gel.

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.