Small Scale Stevia Extraction

I am happy to announce that the construction of miniature steviol glycoside extraction set-up is completed successfully. We have adopted resin free extraction technology for this extraction system. The system consists of the following steps –

  1. Extraction with hot water by percolation

  2. Electro-coagulation and filtration

  3. Continuous counter current solvent extraction from the water extract

  4. Decolorization of solvent phase by activated carbon

  5. Evaporation of solvent under reduced pressure for TSG crystallization and solvent recovery.

 

The first crystallization yields TSG of 90% purity – which can be purified into TSG 95% and Reb A 98% by recrystallization.

In our set-up, we used miniature versions of industrial equipment, as far as practicable. All the custom equipment are fabricated in our laboratory, including the continuous counter current liquid-liquid extractor. This set-up will be used as a process modification and standardization platform.

The process has the following advantages –

  1. Semi-continuous process

  2. Lesser number of process steps.

  3. Lesser number of equipment.

  4. More efficient extraction with less water use

  5. Higher energy efficiency

  6. Less floor space requirement

  7. No separate solvent recovery system required

  8. No costly nanofiltration system

  9. Lower consumable cost

  10. No spray drying, hence no solvent vapour loss

Dried crystallized steviol glycoside

Crystallized steviol glycoside

Crystallized steviol glycoside 10X magnification

In our process we do not employ spray drying method to separate solid TSG from alcoholic solution. Vacuum evaporation method used by us produces large crystals instead of powders. The crystals are less hygroscopic than spray dried powders and more resistant to oxidation in air.

The technology is also suitable for small sized extraction unit. With this technology, the process economy is less dependent on the production scale. Small yet economically viable extraction units with processing capacity as low as 30 – 40 Kg dry leaves per day can also be built by adopting this technology.

Chromatogram of the crystalized steviol glycoside

Adoption of Electro-coagulation method for water extract clarification

For clarification of primary water extract, we have used electro-coagulation process instead of conventional chemical coagulation and precipitation with chemicals like Calcium Carbonate, Ferric Chloride, various alums and poly-electrolytes. The electro coagulation process removes gelatinous materials, plant pigments, tannins and polyphenols, emulsified oily and waxy materials and proteins. Adoption of this process reduces the overall operating cost and eliminates the coagulant chemical use.

We have worked out the optimal electrode material and configuration, current density, polarity reversal rate and other process parameters for efficient clarification water extract of stevia leaves and to prepare the extract for downstream processing.

Continuous Counter Current Liquid-Liquid Extraction

For selectively transferring steviol glycoside from water phase to solvent phase, we have used a Continuous Liquid-Liquid Counter Current Extractor prototyped by us. We have optimized the equipment design and process parameters like water extract pre-treatment for minimization of emulsification, solvent flow rate, water extract dosing rate, mixing speed etc.   

Vacuum Evaporation

Steviol glycosides cannot be crystallized from water or ethyl/methyl alcohol.  In conventional industrial process, these solvents are partially removed from the solution by vacuum evaporation or nano-filtration to make a concentrated solution. In case of alcohols, the solvent recovered from this stage is purified again by distillation for its recycle in the process. The concentrated solution is then spray dried to prepare solid steviol glycosides.

In our process, steviol glycoside can be directly crystallized from the solvent we used. We used vacuum evaporation for solvent removal and recovery. The crystallized can be separated from the mother liquor by centrifugation/filtration. The mother liquor can be reprocessed along with the subsequent batch. The recovered solvent from this process can be directly re-used in the process. This process saves equipment cost, process time and process cost.  

Process Automation

We are in the last phase of assembling a micro-controller based electronic control system for the extraction system. All the process parameters can be programmed in this control system by the operator and then the system runs with minimal human intervention. This system integrates an array of sensors, valves and switches and runs on a complex algorithm developed by us. This automation is expected to reduce the possibility of operator error.

All the process parameters are stored in non-volatile memory, so the Re-programming is not required whenever the extraction equipment are turned off and turned on again. Even an unskilled person can run the whole system once it is programmed. We are planning to dispatch all the extraction system pre-programmed from our fabrication facility, so that the entire extraction line becomes a “plug and play” system. The default process parameters can be changed by the operator to adapt the system to local conditions.

This control system provides visual and audio alarms if there is any equipment failure or process error. The process parameters and process status is continuously displayed in LCD Screens. Programming is done with a simple keypad interface. The programming is also very simple and prompt based.

Controller for the Primary Extractor

Displays and Prompts

Membrane Keypad Interface

Technology Release

Scaled up technology is ready and will be released to a limited number of organizations interested in setting up of pilot and small commercial scale stevia extraction unit. We shall provide comprehensive technical hand-holding service from planning to trial run. Our miniature facility is also open for inspection after fulfillment of certain terms and conditions. If you are interested, kindly register your name by filling the form at left hand side or directly mailing me at -

<stevia.technology@gmail.com>.