Influence of power ultrasound on ice nucleation of radish cylinders during ultrasound-assisted immersion freezing

• Ultrasound-assisted immersion freezing of radish cylinders on nucleation was studied.
• A good linear relationship between nucleation temperature and ultrasound application onset temperature was observed.
• Power ultrasound facilitated the nucleation effectively.
• Ultrasound treatment (−0.5 °C, 7 s, 0.26 W cm−2) was optimal conditions for the nucleation of radish cylinders.

The effect of ultrasound-assisted immersion freezing on the dynamic nucleation of ice and the delay from ultrasound application onset to nucleation commencement of radish cylinder samples were studied. The samples were frozen in 30% (w v−1) CaCl2 solution (−20 °C) in an ultrasonic bath system. To evaluate nucleation, ultrasound irradiation (20 kHz) was carried out with different durations (0 s, 3 s, 7 s, 10 s or 15 s), onset temperature (−0.5, −1, −1.5 and −2 °C) and intensities (0.09, 0.17, 0.26 and 0.37 W cm−2). The results showed that ultrasound irradiation was able to induce nucleation and the nucleation temperature of radish cylinder samples exhibited a good fit to linear equation with the ultrasound irradiation temperature under 7 s duration and 0.26 W cm−2 intensity. Ultrasound irradiation temperature at −0.5 °C for 7 s duration with intensity of 0.26 W cm−2, was an optimal ultrasound application conditions for the nucleation inducement of radish cylinder samples. The results of the current study implied that ultrasound offered promising application to control the crystallization process in freezing of solid foods.