Microwave-Assisted Subcritical Water Extraction of Steviol Glycosides from Stevia rebaudiana Leaves

Abstract

A rapid method that combines microwave heating and subcritical water extraction to extract steviol glycosides from Stevia rebaudiana (Bertoni) or stevia leaves was developed and compared to conventional thermal solvent extraction methods. Within only 1 minute after subcritical water condition at 140°C being reached, the yields of major steviol glycoside, rebaudioside A and stevioside, and less polar steviol glucoside, rebaudioside C, from stevia leaves were comparable to conventional extraction method that used 70% ethanol under sonication for 45 minutes. This new hybrid extraction technique may provide a cost-effective and green approach for commercial production of high-purity steviol glycoside sweeteners and their “organic” versions without the use of highly expensive “organic” ethanol.