Abstract: Myosin from silver carp was sonicated with varying powers (100, 150, 200 and 250 W) for 3, 6, 9 or 12 min. The changes in the chain conformation, secondary structure and rheological properties of myosin were evaluated by UV absorption spectroscopy, circular dichroism spectroscopy and a rheometer. It showed that the low-temperature self-assembly of myosin was depressed by high intensity ultrasound (HIU) treatment, resulting in decreased zero shear viscosity and increased fluidity. HIU treatment induced the conversion of myosin α-helix to relatively loose β-sheet and random coil, resulting in the exposure of active groups buried inside the molecules. This structural change was beneficial for forming intermolecular interactions during heating and reducing the gelation temperature. Furthermore, ultrasonic treatment under appropriate conditions (100 or 150 W for 12 min) could improve the gel-forming capacity of myosin, but it could lead to a decrease in the gel-forming capacity at too high powers (200 or 250 W for 12 min). Selecting the appropriate ultrasonic treatment is of great importance for improving gelation properties of surimi.

Key words: myosin, high intensity ultrasound, structure, rheological properties, silver carp