Stevia Rebaudiana Bertoni or simply Stevia is a native perennial plant originally found at the border regions of Paraguay and Brazil. Cousin of the Chrysanthemum family,the stevia plant has been used as a “sweet treat” or “Kae-he” by guarani Indians for hundreds of years. The plant was made known outside South America first in 1888 by an Italian, Dr. Bertoni, and subsequently introduced to other parts of the world during the 1900's. Dr. Bertoni named the plant after himself and a Paraguayan chemist name Rebaudi. The plant today is commercially cultivated in over 20 countries including Brazil, China, Japan, Korea, and Thailand.
Stevia Plant
Stevia is a small green plant that contains around 10% of stevia-glycosides (sweet components) in its leaves. Stevia in its natural herbal form is approximately 10 to 15 times sweeter than common table sugar and when eaten has a refreshing somewhat bitter sweet aftertaste.
Stevia Glycosides - Sweet Yet Bitter Taste
Stevia leaves contain 6 main glycosides or sweet components where each glycoside contains a different level of sweetness. The two main glycosides are Stevioside and Rebaudioside A (RebA). Typically, Stevioside represents 5-10% of the dry weight of a stevia leaf and the refined white powder extract is 150-250 times sweeter than sugar. The main drawback of Stevioside is its strong bitter menthol-like aftertaste.
RebA on the other hand is 2-4% of the dry weight of a stevia leaf and the extract is 300-350 times sweeter than sugar. RebA is the sweetest glycoside in the leaf and does not generate an aftertaste.
There are also other related compounds including Rebaudioside-C, D, & E and Dulcoside-A&C, as well as minor glycosides that are found in very small quantities in the leaf. They are less sweet and also contribute to the bitterness. A typical stevia extract that combines all 6 glycosides is around 250 sweeter than sugar and has a strong bitter menthol-like aftertaste.

Over the years, a number of breeding programs have been set up in various countries to improve the yield, disease resistance as well as ratio of RebA to Stevioside glycosides in the stevia leaf. Although successful to a certain extend,
the programs still can not possibly remove the bitter and astringent aftertaste associated with Steviosides.

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