Effects of Freeze-Thaw Treatment and Freeze Storage on the Binding Characteristics of Snakehead Myofibrillar Protein to Characteristic Flavor Substances in Fish Soup with Pickled Mustard Greens

The purpose of this study was to explore the effect of freeze treatment on the binding characteristics of fillets to flavor substances in fish soup with pickled mustard greens. The study focused on the effects of freeze-thaw treatment and freeze storage on the physicochemical properties of snakehead myofibrillar protein and its binding characteristics to hexanal, octanal, linalool and myrcene. The results showed that after 7 days of storage, the solubility of myofibrillar protein decreased by about 26% in the freeze-thaw group. Compared with the freeze storage group, the oxidation degree and tertiary structural changes of myofibrillar protein were higher and more soluble aggregates were formed in the freeze-thaw group. The solubility of myofibrillar protein decreased by about 33% in the freeze storage group, which showed a more significant decrease compared to the freeze-thaw treatment (P < 0.05), resulting in more insoluble aggregates. The major force for the aggregation of myofibrillar proteins after freezing was non-covalent bonding. Molecular docking results indicated that linalool, hexanal and octanal could bind to myofibrillar proteins through hydrophobic interactions and hydrogen bonds, while the major driving force for the binding of myrcene to myofibrillar proteins was hydrophobic interaction. Freeze treatment reduced the binding capacity of hexanal and octanal to sulfhydryl groups in myofibrillar proteins through hydrogen bonds, improved the surface hydrophobicity of myofibrillar proteins, but increased the binding ability of myrcene and linalool to myofibrillar proteins. Freeze-thaw treatment increased the binding capacity of myofibrillar proteins to myrcene compared with freeze storage treatment. The results of this research provide a theoretical basis and reference for flavor control of frozen prepared fish soup with pickled mustard greens.