When big energy extraction of ultrasonic wave ACTS on the medium, the vibration are in a state of thin, medium is torn into many small hole natural product extraction equipment, instantaneous is closed, these small holes up to thousands of atmospheric pressure transient pressure when closed, the cavitation phenomenon. The strengthening effect of ultrasonic on the extraction and separation of various components mainly results from its cavitation.
Cavitation in the great pressure caused by the tiny air bubbles burst to the bursting of the broken cell wall and the whole organisms in instantaneous, shortens the time of break and at the same time, the effects of the vibration ultrasonic enhanced the release of intracellular substances, diffusion and dissolution, can significantly improve the efficiency of extraction. The process of ultrasonic crushing is a physical process without chemical reaction, and the bioactive substance is kept unchanged. Cavitation occurs in tiny air bubbles in the liquid core under high intensity ultrasonic oscillation, growth, shrinkage and collapse, and a series of dynamic process in the collapse of a very short time, at the same time around the cavitation bubble produce high temperature and high pressure, strong shock waves and winds of more than 400 kmoh micro jet, stripping, pitting on the surface of solid and crushing function creates a new active surface, the interface effect increased mass transfer surface area. The turbulent effect caused by cavitation makes the mass boundary layer thin in the solid-liquid interface, resulting in a decrease in the concentration gradient of solute in the interface layer. The perturbation effect caused by cavitation can strengthen the diffusion of the micro-hole in solid liquid mass transfer process, so as to strengthen the eddy diffusion and accelerate the extraction process. The ultrasonic frequency is increased, the extraction time is prolonged, and the polymerization effect produced by ultrasonic field causes the extraction temperature to rise. The turbulence effect, perturbation effect, interfacial effect and clustering effect are related to the frequency, power and temperature of the ultrasonic field. In the process of extraction of natural products, cell wall-breaking, balancing speed and the diffusion of the solute is associated with the ultrasonic power per unit area, and will affect the extraction efficiency and recovery rate, therefore generally choose low frequency high power ultrasound.
Although ultrasonic extraction effect is very good in small sample preparation in the laboratory and has been widely used, especially in the analysis of sample processing, the characteristic of its rapid, efficient has widely, but the scope and intensity of the ultrasonic field limits the time to deal with the amount of material, the lack of effective means of engineering amplification method and limits its application in mass production.