Stevia a natural high intensity sweetener

30/06/2011

Stevia is a genus of about 240 species of herbs and shrubs in the sunflower family, native to subtropical and tropical regions from western North America to South America. The species stevia rebaudiana, commonly known as sweetleaf, sugarleaf, or simply stevia, is widely grown for its sweet leaves. 

Steviol glycosides are natural constituents of the plant Stevia Rebaudiana Bertoni, which belongs to the Compositae (Asteraceae) family. Steviol glycosides are of interest due to their sweetening properties, and stevioside and rebaudioside are the principle components of them. The product is obtained from the leaves of Stevia Rebaudiana Bertoni. The leaves are processed with hot water and the aqueous extract is further concentrated and purified. The final product may be spray-dried. Steviol glycosides preparations are white or slightly yellowish white crystalline odourless or having a slight characteristic odour, water soluble powders, which are 200 to 300 times sweeter than sucrose.

Stevia extracts generally contain a high percentage of the glycosides stevioside and rebaudioside A, and smaller amounts of other steviol glycosides i.e rebaudioside C, dulcoside A, rubusoside, steviolbioside, and rebaudioside B. The composition of the extracts depends on the composition of the leaves, influenced by soil and climate, and on the extraction and purification processes used. The impurities occurring in extracts of the Stevia leaves are typical plant materials, such as pigments and saccharides.

Chemical Names

Stevioside: 13-[(2-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy] kaur-16-en-18-oic acid, β-D-glucopyranosyl ester

Rebaudioside A: 13-[(2-O-β-D-glucopyranosyl-3-O-β-Dglucopyranosyl-β-Dglucopyranosyl)oxy]kaur-16-en-8-oic acid, β-D-glucopyranosyl ester

Rebaudioside B: 13-[(2-O-α-L-rhamnopyranosyl-3-O-β-D-glucopyranosyl)oxy]kaur-16-en-18-oic acid, β-D-glucopyranosyl ester

Dulcoside A: 13-[2-O-α-L-rhamnopyranosyl-β-D-glucopyramosyl]oxy]kaur-16-en-18-oic acid,β-D- glucopyranosyl ester 

Steviol glycoside extracts have broad applications as sweetener in the manufacture of fruit and milk drinks, desserts, yoghurt, delicacies, confectioneries, fruit products, processed seafood products, pickles, table-top sweeteners and dietary supplements. The extracts are suitable for cooking purposes as they are heat stable, unlike some artificial sweeteners such as aspartame. However, they are unsuitable for certain confectionary such as fudge or icing as they lack bulking property. Water extracts of the crushed leaves of the stevia plant have been used for many years as a sweetener in some countries in South America and Asia. It is also known that stevia leaves are used to prepare a sweetened tea in a number of countries throughout the world. 

Rebaudisode A has the least bitterness of all the sweet compounds in the stevia plant, and is the measured key component. Typically stevia is supplied as steviol glycosides with purities in the 95-100% range, with the percentage of the key rebaudisode A being quoted along with the sum of the other related Glucocides. Typically rebaudisode A in the range 40-80% is used in food and beverages as the taste and sweetness is suitable, while the Rebaudisode A in the 95-98% range are used in table to sweeteners. 

Safety Considerations

Stevioside and Stevia extract are considered as food additives under the Australian and New Zealand Food Standards Code, Standard 1.3.1. food additives. It is permitted to be used as per Standard 1.3.1 Food additives schedule 1 as follows:

• INS Number Additive Name Max Permitted Level
• 960 Steviol glycosides 115 mg/kg
• (calculated as steviol equivalents)

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