Influence of sonication process parameters to the state of liquid concentration of extracted rebaudioside A from Stevia (Stevia rebaudiana bertoni) leaves

The purpose of this work was to develop a process to obtain Stevia extract of a better quality and quantity under influence of ultrasound technique. The chemical compositions, anti-nutritional factor and heavy metals of raw material were tested firstly in (w w−1) in our previous work. The extraction process was assisted by ultrasonication at power 360 W for 12 min using three different types of solvents (water, ethanol and isopropyl alcohol) in different concentrations, that is, 10, 20, 30, 40, 50, and 60% (v v−1) to optimize the extraction process. Stevia leaves extractions, analyzed by HPLC, indicated that isopropyl alcohol (60% v v−1) gave the highest rebaudioside A yield (35 g 100 g−1). This optimum concentration was used in the next set of experiments to optimize ultrasonic power and time. Optimum applied power and sonication time was found 18 min and 480 W, respectively. The extraction yield obtained under optimum process conditions for water, ethanol and isopropyl alcohol were 32.79, 33.85 and 37.10 (g 100 g−1), respectively. Compared to classical methods like maceration and heat extraction, the utilization of ultrasound-assisted extraction proved to be a much simpler and efficient way to obtain rebaudioside A from Stevia rebaudiana leaves.