I have been working on the development of a cheap, energy efficient and simple process of steviol glycoside extraction from my Sun Biotechnology days (2005). The common extraction technologies involves a very extensive infrastructural requirements and are not at all efficient in terms of energy efficiency, water use efficiency and space utilization efficiency. To overcome the drawbacks associated with the available technologies, the below described technology was developed and tested in large scale. I pasted here the HPLC of first crystallized sample. At that time leaves with high Reb A was unavailable, thus the sample contained more stevioside and less Reb A.
Description of the technology
Process flow chart
Dry leaves are first extracted with hot water either through recycling percolation or by counter current continuous extracton
Dired Stevia leaves
Then the water extract is cooled by passing through a heat excahnger supplied with cold water. Then it is allowed to settle and filtered
Water immscible organic solvent system
The filtered water extract is then solvent extracted with a mixed water immiscible organic solvent in a counter current continious solvent extractor.
Then the water and organic solvent phases are seperated with high speed disk stack centrifuges
The water phase goes for effluent treatment and disposal
The organic solvent phase is then heated and passed through activated carbon column to remove pigments and impurities
The decolorized organic solvent phase is then evaporated under partial vacuum to crystallize steviol glycoside
The evaporated solvent is cooled by heat exchangers supplied with chilled coolant and directly recycled in the process
The crystallized steviol glycoside is then seperated from the mother liquor by centrifugation and dried in vacuum dryers.
Dried steviol glycoside is recrystallized from a different solvent system and dried to further purify it and to sepreate individual glycosides.
Salient Features of the new Technology
It took me almost 2 years to develope the basic technological framework and to test it in laboratatory scale. Then a pilot facility for production of 2.0 Kgs per day was built. After standardizing the major process parameters in this pilot facility, the work for its scalling up began in 2009. A commercial scale extraction unit was first built in Baddi, Himachal Pradesh, India with economic assitance from Technology Information and Forecasting Council, Department of Science and Technology, Government of India. In this unit, the first batch of crystallized steviol glycoside was produced in 22nd March, 2010.