Abstract: Commonly, selective extraction is produced by solubility in different solvents. Then different ultrasonic yields affectdifferent ingredients from plants differently , and make their motorial velocities to be different. Studying the velocity can makecertain the selectivity of ultrasonic extraction. In this paper, preliminary investigating the extraction speed of the amino acid andthe caffeine of green tea were influenced by single-frequency ultrasonic extraction(SFU), dual-frequency-complex ultrasonicextraction (DCU) and dual-frequency-alternant ultrasonic extraction(DAU) at two ultrasonic frequencies in low ultrasonicintensities, and the experimental plan of various experimental conditions, such as temperature, solid and liquid rate, intensity(upto 0.6W/cm2), frequency(28kHz and 40kHz), time were done according to uniform design by DPS, or the data was processed withPLS procedure, and the effect of the factors on this extraction speeds in the optimum conditions was confirmed by the standardregression coefficient, and quantitative compare the amino acid extraction speed (AAS) with the caffeine extraction speed (CFS). The result shows that DAU affected this speeds more intensively, but the AAS increment was not more than the CFS. In addition,frequency and intensity influenced CFS specially and it was positive correlation in SFU, on the contrary, negative correlation forAAS, by all appearances the high CFS depended on high frequency and high intensity. These are a port of reason that differentingredients are extracted by different ultrasonic yields.

Key words: green tea, selective extraction, several frequencies ultrasound, extraction velocity