Extraction of stevia glycosides with CO2 plus water, CO2 plus ethanol, andCO2 plus water plus ethanol

Stevia leaves are an important source of natural sugar substitute. There ar e some restrictions on the use of stevia extract because of its distinctive aftertaste. Some authors attribute this to soluble material other than the stevia glycosides, even though it is well known that stevia glycosides hav e to some extent a bitter taste. Therefore, the purpose of this work was to develop a process to obtain stevia extract of a better quality. The propos ed process includes two steps: i) Pretreatment of the leaves by SCFE; ii) E xtraction of the stevia glycosides by SCFE using CO2 as solvent and water a nd/or ethanol as cosolvent. The mean total yield for SCFE pretreatment was 3.0%. The yields for SCFE wi th cosolvent of stevia glycosides were below 0.50%, except at 120 bar, 16 d egrees C, and 9.5% (molar) of water. Under this condition, total yield was 3.4%. The quality of the glycosidic fraction with respect to its capacity a s sweetener was better for the SCFE extract as compared to extract obtained by the conventional process. The overall extraction curves were well descr ibed by the Lack extended model.