Effect of Carboxymethyl Chitosan Magnetic Nanoparticles Plus Herring Antifreeze Protein on Conformation and Oxidation of Myofibrillar Protein From Red Sea Bream (Pagrosomus major) After Freeze-Thaw Treatment

The effects on the quality of frozen red sea bream, which were pretreated by soaking in solutions containing trehalose, carboxymethyl chitosan magnetic nanoparticles (CCMN), and glycerin or 0.1% herring antifreeze protein (hAFP), were investigated. In this study, the viscoelastic properties of protein studied with the dynamic rheology, Raman and intrinsic fluorescence spectrometry were used to explore the conformation changes of MFP. Surface hydrophobicity, particle size, and zeta potential were carried out to analyze protein aggregation. Solubility, the content of total sulfhydryl/disulfide bond/carbonyl/dityrosine, and the Ca2+-ATPase activity were measured to explore the degree of protein oxidation. SDS-PAGE was conducted to analyze the protein denaturation. Results showed that the pretreatment of red sea bream with soak solutions could improve the viscoelasticity of fillets protein, stabilize the secondary and tertiary conformation of the MFP, inhibit the protein aggregation and oxidation, and decrease the degree of protein denaturation compared with the control (4 °C thawing), especially the soak solutions containing hAFP could minimize the freeze-thaw damage. To summarize, the hAFP helped to retain the above characteristics of frozen fillets much better than that of conventional cryoprotectants (glycerin) to improve the quality of the frozen product after thawing.