The mechanism underlying increased myosin solubility in pearl mussels (Hyriopsis cumingii) by epigallocatechin gallate at low NaCl level

The poor water solubility of myosin hinders the full utilization of its functions and limits its application in the food industry. The aim of this study was to investigate the effect of epigallocatechin gallate (EGCG) on the solubility of myosin in pearl mussel (Hyriopsis cumingii) muscle at low NaCl level and the underlying action mechanism. The results showed that myosin solubility increased with the increase of EGCG concentration at 0.2 M NaCl level. The polyphenol binding equivalent and thermodynamic characterization analysis implied that EGCG was mainly bound to myosin via hydrogen bonding and van der Waals force to form an EGCG-myosin complex, and compared with 0.5 M NaCl, the binding affinity of EGCG and myosin decreased at low NaCl level. Structural analysis suggested that EGCG caused myosin endogenous fluorescence quenching, a wavelength redshift and a β-sheet content increase, exposing the aromatic amino acid residues inside myosin molecules to the surface in a polar environment. Scanning electron microscopy observation and particle size result indicated that the introduction of EGCG reduced the particle size of myosin, which was more distinct at 0.2 M NaCl level. Therefore, EGCG ordered and stabilized the myosin structure at low NaCl level by forming a complex with myosin, effectively improving the myosin solubility.