Extracting steviol glycosides from the stevia plant
You have probably heard of ‘steviol glycosides’ and ‘stevia’ and wonder what the difference is. Steviol glycosides is the extract from the stevia plant (stevia rebaudiana) and it is what gives the leaves their sweet taste. Similar to how sucrose is the extract from the sugar plant. Here’s how we at The Real Stevia Company produce our Real Stevia™ product.
The path from leaf to sweetener is done in six steps:
Collecting the dried leaves from the collection sites where our smallholder farmers have deposited them.
Immersing the leaves in warm water to extract the sweet taste of the leaves – the steviol glycosides.
Filtering out unwanted parts of the leaf.
Through a series of filters we take out fibers, salts and the green color. Undissolved parts are filtered out in mechanical filters and dissolved salts and other ions are separated based on their molecular charge in large columns filled with charged particles, which attract the ions we want to remove from the extract liquid. In the last step we choose a column with charged particles that attract the sweet molecules from the stevia leaf – the steviol glycosides. As the other solutes have run through this last column we pour food grade ethanol over the steviol glycosides, which cause them to be released and mixed with the ethanol. This process heightens the concentration of steviol glycosides as all impurities and contaminates that could affect the taste are removed.
Most of the ethanol is recaptured so it can be reused later. This happens in a concentration step where the temperature is increased under low pressure in order to quickly and energy efficiently make the ethanol evaporate.
Drying and crystallization.
The concentrated steviol glycoside and ethanol mixture is dried in a large tower. The method is called spray drying and works by spraying the liquid into the tower at the same time as warm, clean air is blown into the tower. The liquid then dries quickly and crystallized steviol glycosides drop down to the bottom of the spray dryer, where it is collected. This is where the movie ends.
In order to create different tasting stevia extracts a re-crystallization is then used to change the concentration of the different steviol glycosides in the extract. Re-crystallization is a process where the stevia extract from step 5 is dissolved in a mixture of water and food grade ethanol. The mixture is then cooled down at which point the steviol glycoside found in the highest concentration will start to crystallize. By doing this a separation of different steviol glycosides can be obtained.
The final end product is made up of pure crystals of steviol glycoside that are ready for use as a sweetener by the food and beverage industry. To ensure consistent safety and production, a strict control system has been implemented, with quality checks at each stage of the process, from leaf to finished product. The stevia extracts are exactly the same compound outside the leaf as they are found in the leaf. Consequently, the high quality of our grown leaves and extraction process directly contribute to the great taste of the stevia extract.
Below you can see the entire described process in a short animation!