US 7,923,552 B2 · High yield method of producing pure rebaudioside A · patentgrep

Loading patent…

Abstract

The invention provides a high throughput, high purity, high yield system and method of isolating and purifying rebaudioside A (“Reb A”), with acceptable water solubility for all commercial uses, from commercially available Stevia rebaudiana starting material. The invention also provides a means of maximizing yields of 99+% purity Reb A based on the attributes of a given batch of Stevia starting material. The Reb A produced by the invention is water soluble, devoid of bitterness heretofore associated with rebaudioside sweeteners, non-caloric, and suitable for use as a reagent and as an ingredient in orally consumed products, e.g., as a sweetener, flavor enhancer, and flavor modifier.

Drawings

Claims26

Dependent claims

A method of purifying rebaudioside A from Stevia starting material comprising:

(i) formulating a selected EtOH solvent consisting of water and ethanol, (ii) performing a first reflux stage by refluxing the Stevia starting material in the selected EtOH solvent and optionally performing additional reflux stages using retentate isolated from a refluxed mixture or from a stirred wash mixture, (iii) optionally, performing one or more stirred wash stages, and (iv) performing an ethanol purge and drying stage,
wherein formulating a selected EtOH solvent comprises either (A) a reflux solvent approximation, wherein, based on the asserted or labeled purity of a batch of Stevia starting material, for a Stevia starting material labeled or asserted to be 90% rebaudioside A purity, the reflux solvent is formulated as ethanol and water, and for every 5% decrease in rebaudioside A purity below 90% rebaudioside A purity in the Stevia starting material, based on the asserted or labeled purity of a batch of Stevia starting material, increasing the water content of reflux solvent 1% above a baseline of 6% water, and the remaining volume of the reflux solvent is ethanol, or (B) preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest purity rebaudioside A.

A method of purifying rebaudioside A from Stevia starting material comprising:

Formulating a selected EtOH solvent consisting of water and ethanol for the Stevia starting material;
Mixing and refluxing the Stevia starting material in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture;
Mixing and stirring the retentate in ethanol to create a stirred wash mixture;
Separating a retentate by filtering the stirred wash mixture;
and
Purging the ethanol and drying the retentate, wherein the dried retentate is rebaudioside A,
wherein formulating a selected EtOH solvent for the Stevia starting material comprises either (A) a reflux solvent approximation, wherein, based on the asserted or labeled purity of a batch of Stevia starting material, for a Stevia starting material labeled or asserted to be 90% rebaudioside A purity, the reflux solvent is formulated as ethanol and water, and for every 5% decrease in rebaudioside A purity below 90% rebaudioside A purity in the Stevia starting material, based on the asserted or labeled purity of a batch of Stevia starting material, increasing the water content of reflux solvent 1% above a baseline of 6% water, and the remaining volume of the reflux solvent is ethanol, or (B) preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest purity rebaudioside A.

5 more elements

A method of purifying rebaudioside A from Stevia starting material comprising:

Formulating a selected EtOH solvent consisting of water and ethanol for the Stevia starting material;
Mixing and refluxing the Stevia starting material in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture, and optionally mixing and stirring the retentate in ethanol to create a stirred wash mixture and separating a retentate by filtering the stirred wash mixture;
Mixing and refluxing the retentate in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture, and optionally mixing and stirring the retentate in ethanol to create a stirred wash mixture and separating a retentate by filtering the stirred wash mixture;
Optionally repeating one or more times the preceding two steps;
and
Purging the ethanol and drying the retentate, wherein the dried retentate is rebaudioside A,
wherein formulating a selected EtOH solvent for the Stevia starting material comprises either (A) a reflux solvent approximation, wherein, based on the asserted or labeled purity of a batch of Stevia starting material, for a Stevia starting material labeled or asserted to be 90% rebaudioside A purity, the reflux solvent is formulated as ethanol and water, and for every 5% decrease in rebaudioside A purity below 90% rebaudioside A purity in the Stevia starting material, based on the asserted or labeled purity of a batch of Stevia starting material, increasing the water content of reflux solvent 1% above a baseline of 6% water, and the remaining volume of the reflux solvent is ethanol, or (B) preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest purity rebaudioside A.

6 more elements

A method of purifying rebaudioside A from Stevia starting material comprising:

(i) formulating a selected EtOH solvent consisting of water and ethanol, (ii) performing a first reflux stage by refluxing the Stevia starting material in the selected EtOH solvent and optionally performing additional reflux stages using retentate isolated from a refluxed mixture or from a stirred wash mixture, (iii) optionally, performing one or more stirred wash stages, and (iv) performing an ethanol purge and drying stage,
wherein formulating a selected EtOH solvent comprises preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity and yield, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest yield of rebaudioside A final product that has a rebaudioside A purity acceptable to the user.

A method of purifying rebaudioside A from Stevia starting material comprising:

Formulating a selected EtOH solvent consisting of water and ethanol for the Stevia starting material;
Mixing and refluxing the Stevia starting material in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture;
Mixing and stirring the retentate in ethanol to create a stirred wash mixture;
Separating a retentate by filtering the stirred wash mixture;
and
Purging the ethanol and drying the retentate, wherein the dried retentate is rebaudioside A,
wherein formulating a selected EtOH solvent for the Stevia starting material comprises preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity and yield, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest yield of rebaudioside A final product that has a rebaudioside A purity acceptable to the user.

5 more elements

A method of purifying rebaudioside A from Stevia starting material comprising:

Formulating a selected EtOH solvent consisting of water and ethanol for the Stevia starting material;
Mixing and refluxing the Stevia starting material in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture, and optionally mixing and stirring the retentate in ethanol to create a stirred wash mixture and separating a retentate by filtering the stirred wash mixture;
Mixing and refluxing the retentate in the selected EtOH solvent to create a refluxed mixture;
Separating a retentate by filtering the refluxed mixture, and optionally mixing and stirring the retentate in ethanol to create a stirred wash mixture and separating a retentate by filtering the stirred wash mixture;
Optionally repeating one or more times the preceding two steps;
and
Purging the ethanol and drying the retentate, wherein the dried retentate is rebaudioside A,
wherein formulating a selected EtOH solvent for the Stevia starting material comprises preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity and yield, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest yield of rebaudioside A final product that has a rebaudioside A purity acceptable to the user.

6 more elements

Dependencies are inferred from the claim text.

Description21,607 words

Summary3,557 words

#1. Technical Field

#The invention is in the technical field of the purification of rebaudioside A (also known herein as “Reb A” and “RA”) from crude extracts from the plant Stevia rebaudiana, L. Bertoni (“Stevia”). Reb A is a diterpene glycoside found, along with many other glycosides, sterebins, and other compounds, in Stevia extracts. Reb A is the sweetest tasting (roughly 250 to 450 times the sweetness of sucrose at sweetener concentrations used in comestibles) glycoside in Stevia and has enormous commercial potential as a non-caloric sweetener. Generally speaking, the Stevia glycosides, except rebaudioside A, have an undesirable aftertaste (some have a bitter aftertaste), which generally limits the use of such non-Reb A glycosides as sweeteners. Moreover, sterebins (a group of diterpene compounds commonly known as “yellow oil”) in Stevia extracts have an extremely bitter taste, even in minute concentrations. In short, the technical field, and the technical problem, is to isolate, especially at industrial scale, 99+% purity Reb A from crude Stevia extract; such purity eliminates the bitterness or off-taste that characterizes all currently available Stevia sweeteners.

#2. Related Art

Brief description of the drawings14 figures

#FIG. 1 shows an overall view of the laboratory embodiment of the invention.

#FIG. 2 shows the steps in the reflux stage of the laboratory process.

#FIG. 3 shows the steps in the stirred wash stage of the laboratory process.

Detailed description17,855 words

#The invention comprises (i) a high purity, high yield laboratory process that provides 100% pure rebaudioside A using Stevia starting material; (ii) a high throughput, high purity, high yield industrial process, derived directly from the laboratory process, that provides commercial quantities of 99+% purity rebaudioside A using Stevia starting material; (iii) the rebaudioside A made by those processes; (iv) uses of such rebaudioside A; and (v) a means of maximizing yields of a target purity of Reb A based on the attributes of a given lot of Stevia starting material.

#The utility of the laboratory process lies in the ability to produce 100% pure, water soluble Reb A for research, analytic, and synthetic purposes. The utility of the industrial process lies in the ability to produce commercial quantities (e.g., thousands of kilograms) of 99+% purity Reb A for the beverage, food, baking, candy, personal care product, pharmaceutical, tobacco, and other industries, as well as for research, analytics, and synthesis. As a result of the perceived sweetness of very low concentrations of pure Reb A, for most uses, including beverages, Reb A water solubility of less than 1% is acceptable (concentrates require higher solubility, but within the final product solubility range provided by the invention).

#Reb A is significantly less expensive to produce using the invention compared with existing processes, even though the invention produces Reb A of far higher purity. The means provided herein of maximizing yields of 99+% purity Reb A based on the attributes of a given lot of Stevia starting material enables even greater savings in production costs compared with existing processes. Stevia starting material with greater than 40% purity Reb A content is preferred for use with the invention; the additional reflux stages typically required for Stevia starting material of less than RA40 quality typically make the process financially disfavored, and Stevia starting materials with greater than 40% purity Reb A are readily available. RA40 and higher Stevia starting materials are available from Shandong Chengwu Aoxing Stevia Production Co., Ltd., Datianji Town, Chengwu County, Shandong, People's Republic of China, as well as other sources known in the art. Stevia starting materials typically do not exceed RA80; however, a few commercially available, significantly more expensive Stevia extracts, such as the one sold under the product name of Rebaudio by Morita Kagaku Kogyou, Ltd., Joto-ku, Osaka, Japan, have approximately 90% Reb A content. In the reflux and stirred wash stages of the present invention, denatured ethanol is typically preferred for cost reasons, particularly for the industrial embodiment of the invention; absolute ethanol is approximately ten times as expensive as denatured ethanol in the U.S., but in locales where both denatured and absolute ethanol have substantially the same cost, absolute ethanol is preferred over denatured ethanol for use as a sole solvent and as a reflux solvent component. Denatured ethanol containing additives other than 1% ethyl acetate (e.g., ethanol denatured with 5% isopropanol) can be used in the invention, but typically result in reduced yields and purity of final product. Alkanols other than ethanol can be used, but using ethanol avoids food safety issues related to other alkanols.