HIGHLY SOLUBLE STEVIA SWEETENER

Abstract

A method for making highly soluble stevia sweetener compositions is described. The resulting sweetener compositions readily provide high-concentration solutions and also possess superior taste qualities. The compositions can be used as sweeteners, sweetness enhancers, and flavor enhancers in food, beverages, cosmetics, and pharmaceuticals.

Description

The invention relates to a process for the preparation of highly soluble sweet glycosides from a Stevia rebaudiana Bertoni plant, and more particularly for the preparation of highly soluble compositions containing rebaudioside D. Description of the Related Technique The extract of the Stevia rebaudiana (Stevia) plant contains a mixture of different sweet diterpene glycosides, which share a common aglycone—steviol—and differ in the presence of carbohydrate residues at the C13 and C19 positions of the steviol molecule. These glycosides accumulate in Stevia leaves and comprise approximately 10–20% of the total dry weight. Typically, on a dry weight basis, the four main glycosides found in Stevia leaves are Dulcoside A (0.3%), Rebaudioside C (0.6–1.0%), Rebaudioside A (3.8%), and Stevioside (9.1%). Other glycosides identified in Stevia extract include Rebaudioside B, C, D, E, and F, Steviolbioside, and Rubusoside. Steviol glycosides differ from one another in their taste properties. Some of them possess significant bitterness, a persistent licorice aftertaste (Prakash I., DuBois GE, Clos JF, Wilkens KL, Fosdick LE (2008) Development of rebiana, a natural, non-caloric sweetener.Food Chem. Toxic!.. 46, S75-S82). Q / czLn / nznz / B / Yi Rebaudioside D or Reb D (CAS No: 63279-13-0) is one of the sweet glycosides found in Stevia rebaudiana. Studies show that Reb D has a very desirable flavor profile, with almost no bitterness and a persistent licorice aftertaste typical of other steviol glycosides. These properties multiply the significance of Reb D and attract greater interest for methods of preparing Reb D. However, highly purified steviol glycosides have relatively low water solubility. For example, the thermodynamic equilibrium solubility of Rebaudioside A (Reb A) at room temperature is only 0.8%. On the other hand, it is well known that steviol glycosides exhibit the so-called polymorphism (Zell TM, Padden BE, Grant DJW, Schroeder SA, Wachholder KL, Prakash I., Munsona EJ, (2000) Investigation of Polymorphism in Aspartame and Neotame Usinq Solid-State NMR Spectroscopy, Tetrahedron, 56, 6603-6616). Particularly, the amorphous, anhydrous, and solvate forms of Reb A differ significantly from each other in terms of solubility, which is one of the main criteria for the commercial viability of a sweetener. In this respect, as shown in Table 1, the hydrate form of Reb A exhibits the lowest solubility (Prakash I. DuBois GE, Clos JF, Wilkens KL. Fosdick LE (2008) Development of rebiana, a natural, non-caloric sweetener, Food Chem. Toxicol., 46, S75-S82). It was shown that Reb A 10 can transform from one polymorphic form to another under certain conditions (United States Patent Application 11 / 556,049). Table 1 Properties of the forms of Rebaudioside A (Application of United States Patent 11 / 556,049) q / cz Ln / nznz / Ε / γΐΛΐ - Polymorphic Forms Form 1 Hydrate Form 2 Anhydrous Form 3 Solvate Form 4 Amorphous Dissolution rate in H2O at 25°C Very low (<0.2% in 60 minutes) Intermediate (<30% in 5 minutes) High (>30% in 5 minutes) High (>35% in 5 minutes) Alcohol content <0.5% <1% 1-3% <0.05% Content of >5% <1% <3% 6.74% > N humidity Reb D has very low water solubility compared to Reb A. At room temperature, it can only dissolve to a concentration of 0.01–0.05%. When heat is applied, an expert can achieve a solution concentration of up to 0.5%. However, upon cooling to room temperature, Reb D will quickly recrystallize from the solution. Considering the high sweetness intensity of Reb D (approximately 200 times that of sugar), even a 0.05% solubility may seem sufficient for many applications. Many food production processes use highly concentrated ingredient mixtures before producing final food products. In such cases, much higher concentrations of dissolved Reb D are required. It is noted that using heat to dissolve Reb D may not be feasible in compositions containing heat-sensitive components. Furthermore, maintaining high mixing temperatures for extended periods to prevent premature crystallization of Reb D can cause thermal degradation of the mixture components or undesirable changes in organoleptic properties. U.S. Patent Application 12 / 612,374 describes a method for preparing an anhydrous form of Reb D, which has approximately 0.15% solubility at 50°C. The method requires heat-treating the Reb D powder at a temperature of 80–110°C for approximately 50–120 hours under vacuum. It is noted that the described method allows for the preparation of a form of Reb D with limited solubility and still requires a significant temperature increase for dissolution. The prolonged vacuum heat-treating time is also a disadvantage. U.S. Patent Application 12 / 700,223 describes a method for preparing supersaturated solutions of Reb D, wherein the mixture of Reb D with aqueous liquid is heated to 75–90°C and then gradually cooled to provide a relatively stable 0.3% Reb D solution. It is noted that the method describes only a solubilization technique for a specific aqueous liquid and does not provide an easily usable form of the highly soluble Reb D. U.S. Patent Application 13 / 022,727 describes inclusion complexes of steviol glycosides and cyclodextrins, where the glycoside-to-cyclodextrin ratio ranges from 1:1 to 1:20 and the solubility of the complexes ranges from 0.1–7%. It is noted that some techniques described in the application, such as freeze-drying, are difficult to implement in large-scale, multi-ton production runs. The significant proportion of the non-sweet (low-sweetness) compound (i.e., cyclodextrin) also reduces the overall sweetness of the mixture. There is a need to develop highly soluble forms or compositions of Reb D that possess high sweetness intensity and provide stable solutions at room temperature. Furthermore, considering the similar chemical structures of Reb D and other steviol glycosides, as well as other terpene glycosides, there is also a need to develop procedures that can be used in the case of other glycosides as well. Brief Description of the Invention The invention relates to a method for producing a sweetener comprising the steps of providing Stevia sweetener powder, solubilizing it in water under gradient temperature treatment conditions to produce a highly stable concentrated solution, and spray-drying the highly stable concentrated solution to obtain a highly soluble Stevia sweetener powder. Hereafter, the term steviol glycoside(s) shall mean Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, Stevioside, Steviolbioside, Dulcoside A, Rubusoside or other steviol glycoside and combinations thereof. Hereafter, unless otherwise specified, the solubility of the material is determined in reverse osmosis (RO) water at room temperature. Where solubility is expressed as the number of grams of soluble material in 100 grams of solvent. It is to be understood that both the above general description and the following detailed description are exemplary and explanatory and are proposed to provide further explanation of the invention as claimed. Detailed Description of the Invention A process for the preparation of highly soluble Stevia sweetener, particularly a Stevia sweetener comprising Reb D, is described herein. Crystalline Reb D has an inherently low solubility, ranging from approximately 0.01% to 0.05%. Therefore, there is a need for a process in which a highly soluble Reb D or compositions thereof are prepared. In one embodiment of the present invention, the starting materials, comprising sweet glycoside(s) from the plant extract of Stevia rebaudiana Bertoni, including Rebaudioside D, Stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside E, Rebaudioside F, Steviolbioside, Dulcoside A, Rubusoside and other steviol glycosides and combinations thereof, were combined with water in a ratio of 1:1 to 1:10, preferably 1:3 to 1:6 (w / v). The resulting mixture was further subjected to a gradient heat treatment, yielding a highly stable, high-concentration solution. A gradient of 1°C per minute was used to heat the mixture. The mixture was heated to a temperature of 110–140°C, preferably 118–125°C, and held at this maximum temperature for 0–120 minutes, preferably 50–70 minutes. After heat treatment, the solution was cooled to approximately 80°C at a rate of 1°C per minute. This highly stable, high-concentration solution shows no crystallization during up to 1 hour of incubation. The solution was spray-dried using a laboratory spray dryer with an inlet temperature of 175°C and an outlet temperature of 100°C. Highly soluble amorphous compositions of Reb D were obtained with >1% solubility in water at room temperature. In another embodiment of this invention, the starting materials were selected from the group that includes Reb D, Reb A, Rebaudioside B (Reb B) and steviolbioside (Sbio). In yet another formulation, combining Reb D and Reb B, treating them, and spray-drying them using the methods described above resulted in a composition with significantly higher solubility (approximately 1%) compared to the composition obtained by combining Reb D and Reb A in the same ratio (approximately 0.5%). This phenomenon was unexpected, since both Reb D and Reb B have <0.1% solubility, while Reb A used in the experiment had >5% solubility. Therefore, combinations of Reb D and Reb A were expected to have higher solubility compared to combinations of Reb D and Reb B. In one modality the combination comprises Reb D and Reb B in a ratio of 50%:50% to 80%:20%, preferably 70%:30% to 80%:20%. The resulting product has a solubility that varies from 0.5% to 2%. In yet another method, Reb B was converted completely or partially into its carboxylate salt form. The solution containing Reb D and Reb B, after heat treatment and subsequent cooling (as described above), was mixed with a base solution to achieve a pH level of 4.5–7.0, preferably 5.5–6.5. The resulting mixture was spray-dried as described above. Alternatively, other reactions capable of converting Reb B into its carboxylate salt form can also be used. The preferred cations were K+ and Na+, and the bases were KOH and NaOH, respectively. However, those skilled in the art should recognize that other carboxylate salts of Reb B can be prepared in a similar manner. In one experiment, the flavor properties of compositions comprising Reb D and Reb B were compared to compositions comprising Reb D and Reb A in the same ratio. The evaluation shows that the Reb D and Reb B combinations exhibited superior flavor properties compared to the Reb D and Reb A combinations. In particular, the Reb D and Reb B compositions showed almost no lingering bitterness and a more rounded, sugar-like flavor profile. The resulting compositions can be used as sweeteners, sweeteners, and flavor enhancers in various food and beverage products. Examples, but not limited to, include carbonated soft drinks, ready-to-drink beverages, energy drinks, isotonic drinks, low-calorie drinks, zero-calorie drinks, sports drinks, teas, fruit and vegetable juices, juice drinks, dairy drinks, yogurt drinks, alcoholic beverages, powdered drinks, bakery products, cookies, cakes, baking mixes, cereals, confectionery, sweets, candies, chewing gum, dairy products, flavored milk, yogurts, flavored yogurts, cultured milk, soy sauce and other soy-based products, salad dressings, mayonnaise, vinegar, frozen desserts, meat products, fish products, bottled and canned foods, table sweeteners, fruits, and vegetables. ' 4 m.ricc cP- ΌΙΙθόθΓΙ Additionally, the compositions in drug and pharmaceutical preparations and cosmetics, which include but are not limited to oral preparations, cough syrup, vitamin preparations and The compositions are toothpaste, mouthwash, chewable tablets, lozenges, and the like. They can be combined with other food sweeteners. Non-limiting examples of rebaudioside B glycosides, E, rebaudioside as well as other steviol, rebaudioside dulcoside glycosides used as flavorings and sweetening ingredients include stevioside, rebaudioside A, rebaudioside D, rebaudioside steviolbioside, rubusoside, steviol found in the plant extract syrup of Stevia rebaudiana Bertoni and mixtures thereof, stevia, Luo Han Guo extract, mogrosides, high fructose corn, corn syrup, invert sugar, fructooligosaccharides, inulin, mulo-oligosaccharides, coupling sugar, maltooligosaccharides, maltodextrins, corn syrup solids, glucose, maltose, sucrose, lactose, aspartame, saccharin, sucralose, sugar alcohols. Flavor limitations include lemon, Examples not Linux Nutb Q / czLn / nznz / E / Yi orange, fruit, banana, grape, pear, pineapple, bitter almond, cola, cinnamon, sugar, cotton candy, vanilla flavors. Non-limiting examples of other food ingredients include flavors, acidulants, organic and amino acids, coloring agents, bulking agents, modified starches, gums, texturizers, preservatives, antioxidants, emulsifiers, stabilizers, thickeners, and gelling agents. The following examples illustrate preferred embodiments of the invention. It is understood that the invention is not limited to the materials, proportions, conditions, and procedures set forth in the examples, which are illustrative only. EXAMPLE 1 Preparation of concentrated Reb D solution 100 g of rebaudioside D produced by PureCircle Sdn Bhd (Malaysia), with 98.1% purity (dry weight basis), having a water solubility of 0.03% at room temperature, was mixed with 400 g of water and incubated in a thermostatically controlled oil bath. The temperature was increased at 1°C per minute to 121°C. The mixture was maintained at 121°C for 1 year, and then the temperature was decreased to 80°C at 1°C per minute to make Solution #1. EXAMPLE 2 Preparation of concentrated solution of Reb D and Reb A 13 g of rebaudioside D with 98.1% purity (dry weight basis), having a water solubility of 0.03% and 30 g of rebaudioside A with 98.6% purity (dry weight basis) and having a water solubility of 5.5%, both produced by PureCircle Sdn Bhd (Malaysia), were mixed with 400g of water and subjected to heat treatment as described in EXAMPLE 1 to make Solution #2. EXAMPLE 3 Preparation of concentrated Reb D and Reb B solution 70 g of rebaudioside D with 98.1% purity (dry weight basis), having a water solubility of 0.03-6 and 30 g of rebaudioside B with 99.0% purity (dry weight basis), and having a water solubility of 0.01%, both produced by PureCircle Sdn Bhd (Malaysia), were mixed with 400 g of water and subjected to heat treatment as described in EXAMPLE 1 to make Solution #3. EXAMPLE 4 Stability of concentrated solution Solutions #1, #2, and #3, prepared according to EXAMPLE 1, EXAMPLE 2, and EXAMPLE 3, were estimated in terms of their stability. The results are summarized in Table 2. Table 2 Stability of concentrated solution (80°C) Time, Observation.............._... Q / czLn / nznz / B / Yi Min 1 Solution 111 Solution #2 Solution #3 Cloudy solution Clear solution Clear collusion 5 Intense crystallization Cloudy solution Clear solution 15 Viscous suspension of crystals Intense crystallization Clear solution 30 Solidified crystalline mixture Viscous suspension of crystals Clear solution 60 Solidified crystalline mixture Solidified crystalline mixture Cloudy solution Q / czLn / nznz / E / Yi It can be observed that the solution prepared by combining reb D and reb B shows greater stability towards crystallization. EXAMPLE 5 Preparation of highly soluble Rebaudioside D compositions Solutions #1, #2, and #3, prepared according to EXAMPLE 1, EXAMPLE 2, and EXAMPLE 3, were recently spray-dried using a YC-015 Laboratory Spray Dryer (Shanghai Pilotech Instrument & Equipment Co. Ltd., China) operating at an inlet temperature of 175°C and an outlet temperature of 100°C. The solutions were maintained at 80°C to prevent premature crystallization. Solution #1 yielded sample #1, solution #2 yielded sample #2, and solution #3 yielded sample #3. The amorphous powder samples obtained were compared for solubility (Table 3). Table 3 Solubility of Rebaudioside D compositions Solubility, % Observation #3 1 Sample #1 Sample #2 Sample 0.01 Clear solution Clear solution Clear collusion 0.05 Slightly cloudy solution Clear solution Clear solution 0.5 Cloudy solution Slightly cloudy solution Clear solution 1.0 Visible undissolved matter Cloudy solution Clear solution 1.5 Visible undissolved matter Visible undissolved matter Slightly cloudy solution EXAMPLE 6 Taste profile of Rebaudioside D compositions The flavor profiles of sample #1, sample #2, and sample #3 prepared according to the EXAMPLE 5 - A model zero-calorie carbonated beverage was prepared according to the formula presented below. q / cz Ln / nznz / E / γΐΛΐ Ingredient Amount, % Cola Flavor 0.34 0 _______ Orthophosphoric Acid 0.100 ____ Sodium Citrate 0.310 Sodium Benzoate 0.018 . Citric Acid 0.018 ____________ Sample # 1 or 2 or 3_________________ 0.050 Carbonated water | _____— The sensory properties were evaluated by 20 panelists. The results are summarized in Table 4. Table 4 Evaluation of zero-calorie carbonated beverage samples Taste Attribute Number of panelists who detected the attribute Sample #1 Sample #2 Sample #3 Bitter taste 0 10 0 Astringent taste 0 12 1 Aftertaste 0 11 1 Comments Amount of taste Clean (20 of Bitter aftertaste Clean (18 of sweet 20) (11 of 20) 20) Evaluation Satisfactory Satisfactory (7 Satisfactory complete (20 of 20) of 20) (17 of 20) The results above show that the beverages prepared using the compositions comprising Reb D and Reb B (sample #3) have a flavor profile almost identical to that of pure Reb D (sample #1), while exceeding pure Reb D in solubility by almost 20 times. On the other hand, the compositions comprising Reb D and Reb A (sample #2) have lower solubility and a different flavor profile compared to sample #3. EXAMPLE 7 Preparation of the Reb D and Reb B carboxylate salt composition: 30 g of rebaudioside D with 98.1% purity (dry weight basis), having a water solubility of 0.03%, and 30 g of rebaudioside B with 99.0% purity (dry weight basis) and having a water solubility of 0.01%, both produced by PureCircle Sdn Bhd (Malaysia), were mixed with 400 g of water and subjected to heat treatment as described in EXAMPLE 1 to make the concentrated solution. The pH of the solution was adjusted with 40% KOH to pH 6.0 and the solution was spray-dried as described in EXAMPLE 5. The flavor profile of the resulting carboxylate salt composition was compared to sample #3 from EXAMPLE 5, according to the procedure described in EXAMPLE 6. No significant differences were revealed between sample #3 and the carboxylate salt composition during the comparison. The process of the present invention resulted in a Rebaudioside D composition that demonstrated a high degree of water solubility and a superior flavor profile. Although the preceding embodiments describe the use of Rebaudioside D, Rebaudioside B, and Rebaudioside A, it is understood that any Stevia-based sweetener may be used and prepared in accordance with this invention, and all Stevia-based sweeteners are contemplated to be within the scope of the present invention. Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Furthermore, the scope of the application is not intended to be limited to the particular embodiments of the invention described herein. Since one of ordinary skill in the art will readily appreciate the description of the invention, compositions, processes, methods, and steps, currently existing or later to be developed, that substantially perform the same function or achieve substantially the same result as the corresponding embodiments described herein may be used in accordance with the invention.

Claims

1. A method for producing a highly soluble Stevia sweetener, characterized in that it comprises the steps of: A) providing a first Stevia sweetener; B) providing a second Stevia sweetener that is different from the first Stevia sweetener; C) providing water; D) mixing the water and the first and second Stevia sweeteners to make a mixture; E) increasing the temperature of the mixture to 110-140 °C by a gradient heat treatment method to make a solution; F) maintaining the solution at an elevated temperature for 0-120 minutes; G) decreasing the temperature of the solution by a gradient method to obtain a highly stable, high-concentration Stevia sweetener solution;and H) spray-drying the high-stability, high-concentration Stevia sweetener solution to provide the high-solubility Stevia sweetener, wherein the high-solubility Stevia sweetener exhibits a water solubility at RT of at least @ 0.5 grams per 100 grams of water, at least @ 1.0 grams per 100 grams of water, Q / czLn / nznz / B / Yi at least @ 5.0 grams per 100 grams of water, or at least approximately 10.0 grams per 100 grams of water.; 2. The method according to claim 1, characterized in that the first Stevia sweetener is selected from the group consisting of: Stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, Steviolbioside, Dulcoside A, Rubusoside or other steviol glycosides and a mixture thereof.

3. The method according to claim 1, characterized in that the second Stevia sweetener is selected from the group consisting of: Stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F, Steviolbioside, Dulcoside 15 A, Rubusoside or other steviol glycoside and a mixture thereof.

4. The method according to claim 1, characterized in that a ratio of the first and second Stevia sweeteners is approximately 99:1 to 1:99, approximately 50:50 to 95:5, or approximately 70:30 to 90:10 (w / w)- 5. The method according to claim 1, characterized in that the first Stevia sweetener is rebaudioside D. 25 6. The method according to claim q / cz Ln / nznz / E / YiAi 1, characterized in that the second Stevia sweetener is rebaudioside B, rebaudioside A, steviolbioside, a mixture of rebaudioside A and rebaudioside B, a mixture of rebaudioside A and steviolbioside, a mixture of rebaudioside A, rebaudioside B and steviolbioside, or a mixture of rebaudioside B and steviolbioside.

7. The method according to claim 1, characterized in that a ratio of water to the first and second Stevia sweeteners combined is approximately 1:1 to 10:1, or approximately 3:1 to 6:1 (v / w).

8. The method according to claim 1, characterized in that the temperature of the mixture is increased to approximately 11S-125=C.

9. The method according to claim 1, characterized in that the temperature of the mixture is increased to 110-140 °C or approximately 118-125 °C at a gradient of approximately 1 °C per minute.

10. The method according to claim 1, characterized in that the solution is maintained at a temperature of approximately 110-140°C or approximately 118-125°C for a period of approximately 0-120 minutes or approximately 50-70 minutes.

11. The method according to claim 1, characterized in that the temperature of the solution is cooled to a temperature of approximately 80°C at a gradient of approximately 1°C per minute to obtain the high stability and high concentration Stevia sweetener solution.

12. The method according to claim 1, characterized in that the spray drying is carried out in a spray drying apparatus operating at inlet temperatures of approximately 175 °C and outlet temperatures of approximately 100 °C.

13. The method according to claim 1, characterized in that the pH of the high-stability, high-concentration Stevia sweetener solution is adjusted by means of an alkaline solution to approximately pH 4.5 to 7.0, or approximately pH 5.5 to 6.

5.

14. A highly soluble Stevia sweetener powder, characterized in that it is made by the process according to claim 1.

15. A highly soluble Stevia sweetener made by the process according to claim 1, characterized in that it comprises a mixture of rebaudioside D and rebaudioside B, wherein rebaudioside B is partially or completely converted to a carboxylate salt.

16. An educational composition, characterized in that it comprises a highly soluble Stevia sweetener made by the process according to 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 the 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, maltodextrins, corn syrup solids, glucose, maltose, sucrose, lactose, aspartame, saccharin, sucralose, sugar alcohols and a combination thereof.

17. A flavor composition, characterized in that it comprises a highly soluble Stevia sweetener made by the process according to 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.

18. A food ingredient, characterized in that it comprises a highly soluble Stevia sweetener made by the process according to claim 1 and an additional food ingredient selected from the group consisting of: organic and amino acidulants, coloring agents, bulking agents, modified starches, gums, texturizers, preservatives, antioxidants, emulsifiers, stabilizers, thickeners, gelling agents and a combination thereof.

19. A food, beverage, cosmetic or pharmaceutical product, characterized in that it comprises a highly soluble Stevia sweetener made by the process in accordance with claim 1.

20. A highly soluble stevia composition, characterized in that it comprises a mixture of rebaudioside D and rebaudioside B, in a ratio of approximately 50%:50% to approximately 80%:20% (w / w), wherein the composition has a solubility ranging from 0.5% to 2%.

21. A food, beverage, cosmetic or pharmaceutical product, characterized in that it comprises the composition of stevia according to claim 20.