Extraction of glycyrrhizic acid from licorice root using ultrasound: Process intensification studies

This work deals with the intensification of extraction process of glycyrrhizic acid (GA) from licorice using ultrasound. Various process parameters such as extraction time, solvent to solute ratio, extraction temperature and ultrasound frequency which affect the extraction yield are optimized. The maximum yield of 36.4 mg of GA/g of licorice is obtained at optimized parameters of 10 min time, 30:1 solvent to solute ratio, 40 degrees C temperature and 25 kHz frequency. The yield obtained with ultrasound assisted extraction (UAE) is compared with that of Soxhlet and batch extraction of GA. It is observed that the ultrasound assisted extraction not only gives higher yield but also reduces the extraction time as compared to conventional method. Temperature has no effect on ultrasound assisted extraction while higher frequency of ultrasound gives slightly better extraction yield. Further the kinetics of this extraction process is also investigated based on the second order rate equation available in the literature. Extraction rate constant, initial extraction rate and equilibrium concentration for different solvent to solute ratio and temperatures are predicted. Model validation is done successfully by plotting experimental and predicted values of concentration of GA in extract. (C) 2012 Elsevier B.V. All rights reserved.