We are often asked whether our products are pure stevia. The answer depends on exactly what is meant by pure stevia.
A lot of people who first come to stevia are advised by their friends/colleagues, or Google search, to only purchase pure stevia. Unfortunately stevia is not like cane sugar where you obtain exactly the same product from different sources (allowing, perhaps, for a difference in the granule size between suppliers).
Stevia leaves contain 6 stevia components (called glycosides), where each component contains a different level of sweetness. The two main components are Stevioside and Rebaudioside A (RebA). Generally, Steviosides represent 5-10% and RebA represents 2-4% of the dry weight of a stevia leaf respectively. There are other related compounds that are found in very small quantities in the leaf and they are less sweet and also contribute to the bitterness often tasted in inferior quality stevia.
Stevioside extract is generally 200-300 times sweeter than sugar but has that bitter menthol-like aftertaste. RebA extract is between 300-450 times sweeter, depending upon the grade, than sugar and is the sweetest compound in the leaf with much less of an aftertaste. Very high grade RebA (the higher the RebA number, the higher the sweetness level), as high as 98%, but generally 95-97% are the grades that most use to obtain the best sweetness level and taste.
Sometimes even high grade RebA has a slight aftertaste that some people do not like, which is the reason why manufacturers often add a filler (inulin, erythritol etc) to the product. This is not only to overcome that potential taste issue but also to reduce the sweetness level to one that consumers can manage. Our Naturally Sweet Stevia Blend has Erythritol and our SweetLeaf Stevia has inulin as the fillers.
So when customers ask whether we use pure stevia the answer is "Yes" we use only RebA 98 grade in our products but, apart from our pure stevia extract products (OREBA40, OREBA97 and our NSS97E) they do contain fillers so the question that should be asked is whether the product is a high grade stevia - not whether it is pure stevia.