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超低温保存技术。本课题的目的是研究超声振动对水过冷的影响。测试了两种类型的超声振动：(A)频率为1 MHz的调幅振动和(B)调幅振动。对于调幅振动的情况，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20-25 kHz时，过冷度有微弱的增强。此外，由于超声振动的作用具有促进形核和抑制形核两方面的作用，因此存在提高过冷度的最佳超声功率。在总结这些结果的基础上，结合超声辐照的方法，对生物组织中的声晶化机理进行了讨论。

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.