A novel on-line ultrasonic extraction system for determination of the optimal ultrasonic frequency for plant material

An ultrasonic extraction efficiency or yield varies with the change of ultrasonic frequency, because each kind of plant material possesses a unique natural resonant frequency. Only when the ultrasonic frequency is equal to the natural resonant frequency of the plant material, the extraction efficiency or yield will be up to the highest value. With existing ultrasonic extraction technologies or devices, it may be difficult to determine the optimal ultrasonic frequency for different plant materials because of selecting only one or a few frequency points. To determine the optimal ultrasonic frequency, this paper presented a novel ultrasonic extraction technology in our laboratory, which is an on-line extraction system for the determination of the optimal ultrasonic frequency well suited for various plant materials. This system was composed of eight similar working groups, for which the ultrasonic frequency band was set in a range of 18-82 kHz. A determination method for the optimal ultrasonic frequency was carried out by two steps, including determining the optimal frequency band and frequency point. In order to evaluate the performance of this extraction system, a comparative experiment of hesperidin from tangerine peels was also performed under the same extraction conditions. The results showed that the highest extraction efficiency of extracting hesperidin from tangerine peels appeared at 47.5 kHz, which gave a higher extraction yield compared to the existing ultrasonic extraction technology, and also significantly shortened the extraction time. The novel extraction system was developed to efficiently extract plant material by determining optimum extraction frequency via two steps. Extraction experiments show that this extraction system gave a higher extraction yield compared to existing ultrasonic extraction method.