Glucosyl stevia composition

1. A process for producing a highly purified glucosyl stevia composition, comprising the steps of:

adding starch into water to form a starch suspension;

adding a mixture of α-amylase and CGTase into the starch suspension and incubating for about 0.5 to 2 hours at about 75-80° C., resulting in a first liquefied starch suspension;

inactivating the α-amylase by low pH heat treatment;

cooling the first liquefied starch suspension and adjusting the pH to about 5.5 to 7.0;

adding steviol glycosides into the first liquefied starch suspension, resulting in a first reaction mixture;

adding CGTase into the first reaction mixture and incubating for about 12 to 48 hours at about 55-75° C.;

removing non-reactant maltoologosaccharides by contacting the first reaction mixture with macroporous adsorbent resin and subsequently eluting adsorbed diterpene glycosides with aqueous ethanol to result in a glycoside-containing first aqueous ethanol eluate;

removing ethanol from the first aqueous ethanol eluate, resulting in a first aqueous eluate;

concentrating and drying the first aqueous eluate to obtain the first dried glucosyl stevia composition;

preparing a second liquefied starch suspension in the same manner as the first liquefied starch suspension;

adding the first dried glucosyl stevia composition into the second liquefied starch suspension, resulting in the second reaction mixture;

adding CGTase into the second reaction mixture and incubating for about 12 to 48 hours at about 55-75° C.;

inactivating the enzyme in the second reaction mixture by heat treatment;

decolorizing the second reaction mixture;

removing non-diterpene compounds by contacting the decolorized second reaction mixture with macroporous adsorbent resin and subsequently eluting adsorbed diterpene glycosides with aqueous ethanol to result in a glycoside-containing second aqueous ethanol eluate;

desalting the glycoside-containing second aqueous ethanol eluate with ion-exchange resins;

removing ethanol from the second aqueous ethanol eluate, resulting in a second aqueous eluate; and

concentrating and drying the second aqueous eluate to obtain the highly purified glucosyl stevia composition;

wherein the highly purified glucosyl stevia composition comprises steviol glycosides and their derivatives having up to twenty α-1,4-glucosyl residues.

2. The process according to claim 1 , wherein the mixture of α-amylase and CGTase contains about 0.001-0.2 KNU of α-amylase per one unit of CGTase.

3. The process of claim 2 , wherein the mixture of α-amylase and CGTase contains about 0.05-0.1 KNU of α-amylase per one unit of CGTase.

4. The process according to claim 1 , wherein the weight of added steviol glycosides is about equal to that of the starch used to make the first liquefied starch suspension.

5. The process according to claim 1 , wherein the added steviol glycosides are selected from the group consisting of stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, dulcoside A, steviolbioside, rubusoside, as well as other steviol glycosides found in Stevia rebaudiana Bertoni plant and mixtures thereof.

6. The process according to claim 1 , wherein the weight of added first dried glucosyl stevia composition is about equal to that of the starch used to make the second liquefied starch suspension.

7. The process according to claim 1 , wherein the first dried glucosyl stevia composition comprises stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, dulcoside A, steviolbioside, rubusoside, and α-1,4-glucosyl derivatives thereof with up to nine α-1,4-glucosyl residues.

8. The process according to claim 1 , wherein the CGTase is produced by cultures of Bacillus stearothermophilus.

9. The process according to claim 1 , wherein the CGTase added to the first or second reaction mixture_is added at amount of about 0.2-4 units per gram of solids.

10. The process according to claim 1 , wherein the CGTase added to the first or second reaction mixture is added at amount of about 0.5-1.2 units per gram of solids.

11. The process according to claim 1 , wherein the decolorizing is performed using activated carbon.

12. The process according to claim 1 , wherein the decolorizing is performed using ion exchange resins or membranes, said membranes being selected from the group consisting of ultrafiltration, nanofiltration, and reverse osmosis membranes.

13. The process of claim 1 , wherein removing maltooligosaccharides and non-diterpene compounds from the first or second reaction mixture is conducted with a plurality of sequentially connected columns packed with a macroporous adsorbent resin, followed by washing the columns with water, then washing with about 10-50% (v/v) ethanol, disconnecting the columns, and then eluting each column individually with 30-100% ethanol.

14. The process according to claim 1 , wherein the desalting is performed by passing the eluate through columns packed with ion exchange resins or membranes, said membranes being selected from the group consisting of ultrafiltration, nanofiltration, and reverse osmosis membranes.

15. The process according to claim 1 , wherein the highly purified glucosyl stevia composition has at least about 95% total steviol glycosides on an anhydrous basis.

16. The process according to claim 1 , wherein the highly purified glucosyl stevia composition has less than 10% unreacted steviol glycosides on an anhydrous basis.

17. A sweetener composition comprising a highly purified glucosyl stevia composition made by the process of claim 1 , and an additional sweetening agent selected from the group consisting of: stevia extract, steviol glycosides, stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, dulcoside A, steviolbioside, rubusoside, other steviol glycosides found in Stevia rebaudiana Bertoni plant and mixtures thereof, Luo Han Guo extract, mogrosides, high-fructose corn syrup, corn syrup, invert sugar, fructooligosaccharides, inulin, inulooligosaccharides, coupling sugar, maltooligosaccharides, maltodextins, corn syrup solids, glucose, maltose, sucrose, lactose, aspartame, saccharin, sucralose, sugar alcohols, and a combination thereof.

18. A flavor composition comprising a highly purified glucosyl stevia composition made by the process of claim 1 , and an additional flavoring agent selected from the group consisting of: lemon, orange, fruit, banana, grape, pear, pineapple, mango, bitter almond, cola, cinnamon, sugar, cotton candy, vanilla, and a combination thereof.

19. A food ingredient comprising a highly purified glucosyl stevia composition made by the process of claim 1 , and an additional food ingredient selected from the group consisting of: acidulants, organic and amino acids, coloring agents, bulking agents, modified starches, gums, texturizers, preservatives, antioxidants, emulsifiers, stabilizers, thickeners, gelling agents, and a combination thereof.

20. A food, beverage, cosmetic or pharmaceutical product comprising a highly purified glucosyl stevia composition made by the process of claim 1 .