In this method, the clarified water extract is mixed with a water immiscible organic solvent and agitated vigorously. The solvent has higher affinity towards steviol glycosides than water and it absorbs the glycosides from the water extract.
After the mixing, the solvent-water extract mixture is allowed to stand for some time. On standing the solvent and water layer separates. The water layer, which is now devoid of any steviol glycosides, is sent to effluent treatment plant. The solvent layer is then treated with activated carbon to decolorize it and filtered to separate suspended activated carbon particles.
Then the decolorized solvent is concentrated by evaporation under vacuum and solvent is recovered for recycling. Steviol glycosides start crystallizing out from the solvent after it gets concentrated to a certain level.
The crystals are separated from the mother liquor by a basket centrifuge. The mother liquor is sent back to the process and the crystallized glycosides are sent for further purification through recrystallization. We have made several improvement of this process to make it more efficient. For solvent extraction we have successfully developed a continuous process based on Kuhni type extractor. For quick and efficient seperation of solvent phase, special disc stack centrifuge is also successfully employed.