While stevia refers to the entire plant, Rebaudioside A or Reb A is the primary steviol glycoside that make stevia sweet. There are typically 10 different steviol glycosides that can be found in varying concentrations within the stevia plant.
10 Steviol Glycosides found in Stevia
- Dulcoside A
- Rebaudioside A
- Rebaudioside B
- Rebaudioside C
- Rebaudioside D
- Rebaudioside E
- Rebaudioside F
Extraction Process of Steviol Glycosides
In order to be used in foods the glycosides need to be purified into extracts, which can be done with simple water/alcohol extraction techniques. The extraction process does not effect the composition or structure of the steviol glycosides.
The first step in the extraction process involves soaking the stevia leaves in hot water in order to separate the liquid from the plant. The plant is further purified using water and/or food grade alcohol to make a fine white powder.
In the United States, stevia extracts must be comprised of 95% steviol glycosides in order to be used as a general purpose sweetener. While the overall percentage of steviol glycosides needs to be above 95%, the industry often refers to stevia based on its primary glycoside Rebaudioside A.
Sensory Analysis of Reb A
Most manufacturers produce stevia that has a Reb A concentration of 95% or higher. This is because although stevia is 200 to 300 times sweeter than sugar, its flavor profile is often found to be unfavorable by many consumers, which is more noticeable in lower concentrations of Reb A. Stevia has eight different flavor characteristics which can be tasted in the following order:
- Sweet Taste
- Bitter Taste
- Sweet Aftertaste
- Total Aroma
Even stevia extracts with a high percentage of Reb A, still has some of these negative attributes however, it is less noticeable.
Human taste buds contain different receptors to identify sweet and bitter compounds. While there is only one receptor responsible for sweetness, there are 25 that identify bitterness; however, only two receptors, hTAS2R4 and hTAS2R14 are activated when consuming stevia. The challenge for stevia is that sweetness and bitterness come from the same glycoside and the different solutions that have been developed typically will effect both bitterness and sweetness together.
Innovations in the stevia industry
Companies looking to use stevia in their product formulations are looking for innovative solutions to solve the taste defect issues found in stevia. There are three different approaches that have been used:
Several companies have developed synthetic solutions to help reduce stevia’s aftertaste. Synthetic chemicals are used as a bitter blocker to block a bitter taste from binding with a bitter taste receptor. Without the binding affect a person would not be able to perceive the bitterness from stevia. Synthetic solutions however are not 100% effective and are often limited to specific applications and tend to lose some of the total sweetness.
Other companies have developed genetically modified solutions to help with the aftertaste. Companies have created methods to genetically modified yeast to produce Reb A glycosides. Although the yeast is genetically modified the Reb A glycosides are considered natural by the FDA; however, the Non-GMO project verified committee has already commented saying that they will not be approving any product using this method.
Another company has taken a different approach and developed an organic bitter blocker derived from mushrooms that effectively improves stevia’s flavor profile. Bitterness, licorice, astringency, sweetness aftertaste, aftertaste and cooling effect are all improved will maintaining total sweetness. The organic technology has recently been adopted by some of the top stevia manufacturers in the world.
History of Stevia
Stevia is a native shrub to South America which has been used for centuries as a sugar substitute. Stevia was first commercialized in Japan just over 40 years ago, which was used as a natural sweetening agent. Now stevia has been approved for use in Korea, Mexico, Taiwan, China, Russia, Australia, Argentina, New Zealand, Colombia, Peru, Uruguay, Brazil and Malaysia. However, as of mid 2015 India has approved stevia extracts to be used in foods, which has exponentially grown the stevia market place.
Consumers Driving the Stevia Market
The World Health Organization (WHO), estimates that stevia could replace 20-30% of all dietary sweeteners within the coming years. This is based on consumers becoming more educated on the effects of sugar and artificial sweeteners, which in turn is driving demand for natural, non-caloric, high intensity sweetener alternatives like stevia. With new technologies and innovations the stevia market could soon become a successful alternative to sugar.