Effect of ultrasonic waves on the freezing rates of potatoes in degassed coolant and untreated coolant.

ABSTRACT

BACKGROUND: Ultrasonic waves are shown to enhance the rate of freezing. OBJECTIVE: To elucidate the mechanism of immersion freezing of potatos with ultrasonic waves. MATERIALS AND METHODS: Ultrasound is applied to potato samples immersed in degassed coolant and untreated coolant. Sonic waves were intermittently applied at temperature below -1 degree C. The freezing rates were measured under different experimental conditions. RESULTS: The use of ultrasonic waves increased the freezing rates of potatoes immersed in both degassed coolant and untreated coolant. However, the freezing rate in the degassed coolant was less than that in the untreated coolant. CONCLUSION: Heat transfer on the interface between the potato sample and sonicated degassed coolant appears to be less than that within the sample in the absence of cavitation. The interface heat transfer between the potato sample and untreated coolant is likely improved due to ultrasonic cavitation.