Abstract: This study was performed to investigate changes in the characteristics of goose breast muscle actomyosin treated with high-intensity ultrasound (frequency 20 kHz, power 800 W, total time 42 min, on-time 2 s and off-time 3 s) during freezing storage. Untreated sample was used as a control. The effect of ultrasonic treatment and different storage time (0, 6, 12, 24, 36 and 48 h) at 4 ℃ on goose breast muscle actomyosin was determined by ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, circular dichroism spectroscopy, ATPase activity, zeta potential, particle size, viscosity, cathepsin activity and scanning electron microscopy. The results showed that ultrasound treatment changed the conformation and significantly reduced the ATPase activity, particle size and viscosity, and significantly increased the zeta potential and cathepsin B, D, L and H activities of actomyosin compared with the control group. Moreover, the surface microstructure significantly changed after ultrasound treatment, transforming the actomyosin structure from complete and ordered arrangement into broken and disordered protein particles. The above findings suggested that ultrasonic treatment could change actomyosin conformation and aid in the dissociation of actomyosin into small molecule proteins, which can provide the theoretical basis for applying ultrasonic treatment to improve goose breast muscle tenderness and quality.

Key words: actomyosin, protein secondary structure, enzyme activity, protein conformation