Ultrasonic Assistance of Food Freezing

Publisher Summary This chapter illustrates the various effects that power ultrasound generates when it is applied to the specific field of food freezing. Cavitation in the unfrozen liquid phase is one of the most significant phenomena provoked by the action of the acoustic energy. Cavitation results in the occurrence of microstreaming, which is able to enhance the heat and mass transfer accompanying the freezing process. Cavitation also benefits initiating the occurrence of nucleation and increasing the rate of nucleation as the gas bubbles produced can act as nucleating agents. Crystal fragmentation is another significant acoustic phenomenon, which can lead to crystal size reduction and, indeed, is one of the most important aspects that many freezing processes target. Resulting from these acoustic effects, power ultrasound has proved itself to be an effective method in assisting food freezing, and its benefits are wide-ranging. It can be utilized to induce nucleation and to control crystal size distribution in the frozen products during solidification of fluid food. If it is applied to the process of freezing fresh foodstuffs, it not only can increase the freezing rate but also can improve the quality of the frozen products. Application of power ultrasound can also benefit the prevention of incrustation on the freezing surface. The ability of power ultrasound in performing these functions is affected by a wide variety of parameters, such as the duration, intensity, or frequency of ultrasonic waves.