Development of high-quality cryopreservation by active control of ice formation utilizing ultrasonic vibration

主动控制结晶的方法是一种很有前途的食品低温保存技术。本课题的目的是研究超声波振动对水过冷的影响。两种类型的超声波振动；(a)频率为1MHz的调幅振动和(b)调幅振动进行了测试。在调幅振动情况下，过冷度随超声功率的增大而减小。另一方面，对于调幅振动，在调幅频率为20-25kHz时，过冷性增强较弱。进一步指出，超声功率对提高过冷度有最优值，超声振动的作用有促进成核和减少成核两个方面。在此基础上，讨论了超声辐照下生物组织超声结晶的机理。

A method to actively controlling crystallization is one of promising technique for cryopreservation of food. The object of this project is to study the effects of ultrasonic vibration on supercooling of water. Two types of ultrasonic vibration; (a)amplitude-regulated vibration at frequency of 1MHz and (b)amplitude-modulated vibration, were tested. Regarding the case of amplitude-regulated vibration, the supercooling degree decreased with increasing ultrasonic power. On the other hand, as for amplitude-modulated vibration, a weak enhancement of supercooling was found at amplitude-modulated frequency of 20-25kHz. Furthermore, it was indicated that there is optimum value of ultrasonic power for enhancing supercooling degree, since the action of ultrasonic vibration would have two aspects as to promote and reduce nucleation. Summarizing these results, the mechanism of sonocrystalization in biological tissue was discussed in relation to method of ultrasonic irradiation.