However, the total freezing time of the highest power intensity UAF-4 was the longest (806 s). This might be attributed to the fact that heat produced by ultrasound cannot be neglected in freezing process. More acoustic energy is converted into heat and absorbed by the medium when more ultrasonic wave is delivered to the medium. Similar results were reported by Hu et al. and Li and Sun who also got the similar trends on the material of dough and potatoes, respectively.