Stevioside polymorphic and amorphous forms, methods for their formulation, and uses
Exemplary embodiments of this invention encompass a method for purifying a substantially crude stevioside, methods for preparing polymorphic and amorphous forms of stevioside, and the polymorphic and amorphous forms prepared therefrom.
1. A method for purifying a polymorphic and/or amorphous form of stevioside consisting of:
combining a crude stevioside mixture containing an extract from Stevia plants and an aqueous organic solvent to form a stevioside solution, the aqueous organic solvent containing water in an amount from about 5% to about 25% by weight and at least one organic solvent; and
crystallizing the stevioside solution in a single crystallization step to obtain a polymorphic and/or amorphous stevioside composition containing stevioside in a purity greater than 95% by weight on a dry basis;
wherein the crude stevioside mixture contains comprises stevioside in a purity from about 60% to about 85% by weight on a dry basis; and
wherein the at least one organic solvent is selected from the group consisting of acetone, acetonitrile, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, tert-butanol, isobutanol, and mixtures thereof.
2. The method of claim 1 , wherein the crude stevioside mixture contains stevioside in a purity from about 70% to about 85% by weight.
3. The method of claim 1 , wherein the at least one organic solvent is selected from the group consisting of methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, tert-butanol, and isobutanol.
4. The method of claim 3 , wherein the at least one organic solvent is ethanol.
5. The method of claim 1 , wherein the organic solvent or aqueous organic solvent and the crude stevioside mixture are present in the stevioside solution in a weight ratio from about 3 to about 5 parts organic solvent or aqueous organic solvent to 1 part crude stevioside.
6. The method of claim 1 , wherein the aqueous organic solvent contains water in an amount from about 10% to about 25% by weight.
7. The method of claim 1 , wherein the stevioside solution in the single crystallization step is stirred or unstirred.
8. The method of claim 1 , wherein the method is carried out at room temperature.
9. The method of claim 1 , wherein the stevioside composition contains stevioside in a purity greater than 97% on a dry basis.
10. The method of claim 1 , wherein the stevioside composition contains stevioside in a purity greater than 98% by weight on a dry basis.
11. The method of claim 1 , wherein the stevioside composition contains stevioside in a purity greater than 99% by weight on a dry basis.