Structural Basis for High-Intensity Ultrasound Treatment in Rheology of Myofibrillar Protein Extracted from <i>White Croaker</i> in Relation to Their Solubility

Abstract

Previous studies have shown that the functionality of myofibrillar protein (MP) extracted from White Croaker was inferior to that from mammalian. Solubility, rheological property and structural changes of MP extracted from White Croaker altered by high-intensity ultrasound treatment (frequency: 20 kHz, power: 500 W) (HIUT) at different time (0, 2, 4, 6, 8 & 10 min) were evaluated and correlation analysis between them were focused in this study. HIUT significantly enhanced solubility of MP suspensions (0.6 M KCl). The MP exhibited highest solubility after 10 min by HIUT. The steady-state shear test indicated that HIUT decreased the zero shear viscosity of MP and increased the fluidity. HIUT broke up MP aggregates and induced myosin heavy chain (MHC) degradation, while lower corresponding molecular weight contents showed in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). HIUT unfolded MP, induced migrations of surface charge groups especially negative charge groups, and increased the exposure of more charged groups and active chromogenic group residues (Tryptophan (Trp), Tyrosine (Tyr) and phenylalanine residue), showing an increase in the zeta potential, the ultraviolet visible absorption spectroscopy (UV) and intrinsic fluorescence intensity. Correlation analysis and principal component analysis (PCA) exhibited that there was a high correlation between the improvement in solubility, the zero shear viscosity of MP and its indexes of structural changes after HIUT. This work provided useful knowledge for the modification of fish MP.