Relationship between structural properties and functionality of common carp myofibrillar protein under low ionic...

This study investigated the effects of high-intensity ultrasound (HIU) at different power levels (100, 200, 300, 400, 500, and 600 W) on the physicochemical, structural, and functional properties of common carp myofibrillar protein (MP) under low ionic strength condition. HIU treatment (particularly at 500 W) significantly reduced particle size (from 136.97 to 14.76 μm) and turbidity (from 0.946 to 0.611) of MP, while increasing the absolute zeta potential (from 9.06 mV to 17.81 mV) (P < 0.05), indicating improved dispersion stability of MP under low ionic strength condition. In addition, HIU treatment dissociated myosin filament aggregates into smaller and more uniformly distributed particles. Structural analyses revealed that HIU treatment promoted conformational rearrangements, including decreased α-helix (from 36.48 % to 32.73 %) and random coil (from 36.62 % to 31.83 %) content and increased β-sheet (from 9.62 % to 16.72 %) and β-turn (from 17.29 % to 18.73 %), accompanied by enhanced exposure of reactive sulfhydryl groups (from 31.78 μmol/g to 49.04 μmol/g) (P < 0.05). These changes were further supported by increased surface hydrophobicity, UV absorbance and fluorescence intensity. Consequently, functional properties were markedly improved with solubility increasing from 1.21 % to 21.43 %, and emulsifying activity index (EAI) and emulsifying stability index (ESI) reaching maximum values at 500 W (P < 0.05). Multivariate analyses (hierarchical cluster analysis (HCA) and principal component analysis (PCA)) demonstrated clear clustering between low-power and high-power treatments and revealed strong correlations between structural changes and functional properties. Overall, moderate HIU (500 W) effectively transformed MP into a more flexible and functional state, providing a promising strategy for improving protein functionality in low-salt systems. In conclusion, HIU treatment effectively enhanced the dispersion stability and emulsifying properties of MP under low ionic strength condition by modulating their particle structure and molecular conformation, providing a promising strategy for improving protein functionality in low-salt food systems.