Stevia water extracts

Extraction of stevia sweeteners from dried leaves can be accomplished with acetonitrile in the presence of calcium carbonate solution (116) or with boiling water adjusted to pH 9.0 (107). Ahmed and Dobberstein (117) extracted stevioside and rebaudioside A and C from dried leaves of S. rebaudiana in a micro-Soxhlet apparatus. They observed that chloroform/methanol provided the best results, compared to chloroform or to chloroform/methanol/water. Extraction of stevioside, rebaudioside A and C, and dulcoside A can also be performed by subcritical fluid extraction using C02 and methanol as a modifier. Such an extraction technique has been gaining popularity as an analytical tool because it is rapid, simple, and less expensive in terms of solvent cost (110). Beverages, tabletop sweeteners, beverages containing pulp, and candies are prepared as indicated in Sec. I.C (110,115,118). 

Examples of other antiviral crude extracts from the Anthemideae tribe included the ethanol extract of Santolina oblongifolia Boiss. [56], and the hot water extract from Stevia rebaudiana Bertoni which showed anti-human rotavirus activity [57]. Another Santolina species, Santolina etrusca (Lacaita) Marchi et Dam., was also active against Saprolegnia ferax [24]. 

Pure stevioside is a white hygroscopic powder (The Merck Index, 1976) and commercial extracts vary from cream to tan powders. The solubility of pure stevioside in water is 1.2 g/1 (The Merck Index, 1976). Commercial extracts have solubilities that range from 300 to 800 g/1 (Stevia Corporation, 1986). The relative sweetness of stevia extracts varies from 15 to 300 (O Donnell, 1983 Richard, 2002 Tunaley et al., 1987 ) The taste of stevioside is characterised by a lingering sweetness and liquorice, bitter off-taste (O Donnell, 1983). This limits its commercial application and it is generally not used as a sole sweetener in most applications. 

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