Modification of reduced-sodium carp myofibrillar protein by a combined strategy with ultrasound and MgCl2 treatment: physicochemical, structural and functional properties

This study explored the modification by which high-intensity ultrasound (HIU, 20 kHz, 300 W) combined with magnesium chloride (MgCl₂, 0–40 mM) influences the physicochemical, structural and functional attributes of reduced-sodium carp myofibrillar protein (MP). The zeta potential (11.39 mV), solubility (80.86 %), surface hydrophobicity (68.72 μg), emulsification activity (20.73 m2/g) and UV intensity significantly elevated after treatment with HIU and 40 mM MgCl₂. Moreover, this combined treatment declined the particle size, total sulfhydryl content, and intrinsic fluorescence intensity of MP. FT-IR analysis revealed that the synergistic processing modified the secondary structure of MP, characterized by an increase in β-sheet and random coil content, while declining the α-helix and β-turn content. SDS-PAGE results revealed that myosin heavy- chain and actin-specific bands increased the band intensity. Additionally, the combined treatment resulted in a lower shear stress and G’ value, and the alteration of the particle size and secondary structure was evidenced by rheological variation. The results revealed that the combination of HIU and MgCl₂ treatment is promising as an effective method for application in the reduced-sodium aquatic product processing industry.