Ultrasonically assisted extraction of total carbohydrates from Stevia rebaudiana Bertoni and identification of extracts

In the present study, in order to maximize the yield of total carbohydrates from Stevia rebaudiana Bertoni, Stevia LUYU-131 was used as test material, and response surface methodology (RSM) was employed to optimize the ultrasound-assisted extraction condition. The results indicated the optimal extraction conditions were an extraction temperature of 68 °C, a sonic power of 60 W and an extraction time of 32 min. Using the ultrasound-assisted extraction, the yield of extracts increased by a factor of 1.5 at the lower extraction temperature (68 °C) and the extraction time (32 min) substantially shortened compared with that of classical extraction. The components analysis of crude extracts revealed that the relative amount of rebaudioside A increased in the ultrasound-assisted extracts as compared with extracts obtained by classical process, and the ultrasound-assisted extracts had better quality.