Abstract: To study the enhancing effect of dual-frequency ultrasound combined with vacuum drying on the drying of basa fish surimi, we evaluated the dehydration pattern, water status, microstructure and rheological properties of the surimi during vacuum drying under different ultrasound power-frequency combinations. The results showed that applying dual-frequency ultrasound shortened the drying time by 41.67%-85.42% and increased the average drying rate by 71.29%-585.16% compared with the control without ultrasound. The results of low-field nuclear magnetic resonance (LF-NMR) illustrated that the content of free water decreased, and the decrease in free water was accelerated with increasing ultrasonic power, while the content of semi-bound water initially increased and subsequently decreased. The results of scanning electron microscope demonstrated that increasing ultrasonic power was beneficial to the formation of mass transfer microchannels in basa fish surimi, thereby reducing mass transfer resistance. Rheological characterization revealed that the surimi maintained the characteristics of pseudoplastic fluid and elastic fluid after double-frequency ultrasound combined with vacuum drying. In addition, the shear stress, apparent viscosity, storage modulus (G’) and loss modulus (G”) increased to different extents. This study can provide references for the application of dual-frequency ultrasound combined with vacuum drying.

Key words: basa fish surimi; dual-frequency ultrasound; vacuum drying; drying characteristics; water mobility; rheology