In this work, nano fish bone (NFB) was prepared from silver carp bones and added to silver carp myosin. The speciation changes and distribution of calcium in NFB (NFB-Ca) during myosin gelation were investigated by measurement of various calcium species, surface element analysis, microstructure examination and low-filed nuclear magnetic resonance (LF-NMR). Results showed that the Ca content of myosin with the addition of NFB significantly increased compared to that without added NFB. NFB-Ca existed mainly in an insoluble form in myosin (> 95%). Heating treatment at 40 ℃ significantly increased the ionic Ca content; however, ionic-Ca was transformed into other forms at 90 ℃. Therefore, it was suggested that part of the soluble Ca released from NFB participated in the formation of salt bridges and consequently was transformed into insoluble calcium, facilitating myosin cross-linking. As a result, a continuous and uniform gel network structure was observed under laser confocal scanning microscopy (LCSM). Meanwhile, LF-NMR showed that the compact microstructure could help to hold more water and decrease water mobility. In addition, the surface Ca of myosin with NFB increased, and the distribution uniformity of Ca was improved after heating treatment.

In the present study, the effect of high intensity ultrasound (HIU) on the physicochemical properties of silver carp myosin with different salt concentrations (0.1, 0.2, 0.3, 0.5, 1.0, 2.0 mol/L NaCl) was investigated in terms of solubility, particle size distribution, static rheological properties, and microscopic morphology. The changes in physicochemical properties of myosin induced by HIU were affected by salt concentrations. At low salt concentration (0.1 mol/L), HIU obviously disrupted the structure of myosin filaments, resulting in decreased particle size and zero shear viscosity, and increased fluidity. Moreover, the solubility of HIU treated myosin with low salt concentration was increased about ten times compared to the untreated control with the same salt concentration, while it was close to that of the untreated control with 0.2 mol/L NaCl. For myosin with medium and high NaCl concentrations (0.5 and 1.0 mol/L), the solubility was better than that with low salt concentration. HIU could induce conformational changes in myosin, resulting in exposure of reactive groups and a further increase in the solubility. However, HIU was less effective in increasing the solubility of myosin at medium and high than at low salt concentrations. In summary, HIU can improve the physicochemical properties of myosin more at low than at medium and high salt concentrations, which might provide a theoretical basis for the production of low-salt surimi products.