Method for preparing rebaudioside B using stevia mother liquor and rebaudioside B product

Abstract

This invention discloses a method for preparing rebaudine B from stevia mother liquor and a rebaudine B product, relating to the field of rebaudine B preparation technology. It addresses the technical problems of complex preparation processes, harsh reaction conditions, and poor quality of rebaudine B obtained in existing technologies. The method for preparing rebaudine B from stevia mother liquor includes: passing a solution of stevia mother liquor through an anion exchange resin column; eluting the anion exchange resin with an alkaline alcohol solution to obtain an eluent containing rebaudine B; adjusting the pH of the eluent to 3-4.5 with an acid solution; stirring the eluent until rebaudine B crystals precipitate; filtering and drying the filter cake to obtain the rebaudine B product. The method for preparing rebaudine B from stevia mother liquor provided by this invention is used for the preparation of high-quality rebaudine B products.

Description

Technical Field

[0001] This invention relates to the field of rebaudioside B preparation technology, and in particular to a method for preparing rebaudioside B using stevia mother liquor saccharide and a rebaudioside B product. Background Technology

[0002] Stevia glycosides are novel natural sweeteners extracted from the leaves of Stevia repens, a perennial herbaceous plant belonging to the Asteraceae family. They are characterized by high sweetness and low calories, making them an ideal sweetener to replace sucrose. Rebaudioside B is one of the sweet components of steviol glycosides. Studies have found that in addition to its strong sweetness, Rebaudioside B also has the physiological effect of lowering blood lipids, making it a new generation of functional sweetener. However, the content of Rebaudioside B in steviol glycosides is relatively small, and the current process for producing Rebaudioside B using purified steviol glycosides is very costly and difficult to mass-produce and widely use.

[0003] Existing technology provides a method for preparing rebaudioside B, which involves alkaline hydrolysis of rebaudioside I to prepare laminarin and rebaudioside B. The specific steps include: maintaining an aqueous solution of rebaudioside I at 80℃–100℃ for 0.5 h; adding alkali at a catalyst-to-substrate molar ratio of 1:10–20:1; reacting at 80℃–100℃ for 2–10 h until rebaudioside I is completely hydrolyzed; then neutralizing with 0.1 mol / L acid; the laminarin product remains in solution, while the other product, rebaudioside B, precipitates out. After filtration, the filter cake is dried to obtain rebaudioside B. However, this method is complex, requires harsh reaction conditions, and results in the coexistence of laminarin and rebaudioside B in solution after acid neutralization, leading to poor quality of the prepared rebaudioside B product. Even recrystallization with alcohol cannot completely remove impurities. Therefore, a new method for preparing rebaudioside B is urgently needed to solve these technical problems. Summary of the Invention

[0004] To address the technical problems of complex preparation processes, harsh reaction conditions, and poor quality of rebaudine B obtained in existing technologies, this invention provides a method for preparing rebaudine B using stevia mother liquor and a rebaudine B product. Therefore, this invention is achieved through the following technical solution.

[0005] In a first aspect, the present invention provides a method for preparing rebaudioside B using stevia mother liquor saccharide, comprising:

[0006] The solution of stevia mother liquor glycosides is passed through an anion exchange resin column, so that rebaudioside B in the solution is adsorbed by the anion exchange resin, and the remaining stevia glycosides are effluent.

[0007] The anion exchange resin was eluted with an alkaline alcohol solution to obtain an eluent containing rebaudioside B.

[0008] The pH of the eluent was adjusted to 3-4.5 with an acid solution, and the eluent was stirred until rebaudioside B crystals precipitated. After filtration, the filter cake was dried to obtain the rebaudioside B product.

[0009] Compared with existing technologies, in the method for preparing rebaudioside B using stevia mother liquor of the present invention, during the process of passing the stevia mother liquor solution through an anion exchange resin column, because rebaudioside B in stevia mother liquor contains a carboxyl group at the C19 position, the charge of the sulfonic acid group or hydroxyl group on the surface of the anion exchange resin first interacts with the charge of the rebaudioside B containing the carboxyl group in the solution. Rebaudioside B forms a stable polymer on the surface of the anion exchange resin, thus being adsorbed by the anion exchange resin. Since the anion exchange resin has a strong adsorption capacity for rebaudioside B, the present invention uses an alkaline alcohol solution with stronger desorption capacity as a desorption agent to desorb the rebaudioside B adsorbed by the anion exchange resin, obtaining a desorbed solution containing rebaudioside B. This invention, by adjusting the pH of the eluent to 3-4.5, inhibits the ionization of the carboxyl groups of rebaudioside B in the eluent, allowing rebaudioside B to exist in a molecular state within the eluent. After crystallizing and separating the rebaudioside B from the eluent, the rebaudioside B product can be obtained. The above technical solution of this invention solves the technical problems of complex preparation processes, harsh reaction conditions, and poor quality of rebaudioside B obtained in existing technologies.

[0010] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, the alkaline-alcoholic solution is a mixed solution of 30-50 wt% alkaline solution and 60-85 wt% alcohol solution; wherein the volume ratio of alkaline solution to alcohol solution in the alkaline-alcoholic solution is 1:(8-80).

[0011] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, the alkaline solution comprises 30-50 wt% NaOH solution, 30-50 wt% KOH solution, or 30-50 wt% ammonia solution; and / or,

[0012] The alcohol solution includes a 60-85 vt% methanol solution, a 60-85 vt% ethanol solution, or a 60-85 vt% propanol solution.

[0013] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, the injection volume of the dissolved solution (dry solids) is 60-120 g / 100 ml of the volume of the anion exchange resin.

[0014] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, before obtaining the eluent containing rebaudioside B and adjusting the pH of the eluent to 3-4.5 with an acid solution, the method further includes:

[0015] The eluent was concentrated to an alcohol concentration of 10–40 wt% and a solid content of 5–20 wt% under conditions of a temperature of 50–90 °C and a stirring rate of 25–100 rpm.

[0016] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, the solution of the stevia mother liquor is a mixed solution of stevia mother liquor and pure water, wherein the mass ratio of stevia mother liquor to pure water in the mixed solution is 1:(4-50); and / or,

[0017] The total glycoside content in the stevia mother liquor is 40-60 wt%, with the remainder being impurities; among the total glycosides, the content of rebaudioside B is 3-12 wt%.

[0018] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, during the process of adjusting the pH of the eluent to 3-4.5 with an acid solution, the concentration of the acid solution is 5-40 wt%; and / or,

[0019] The acid solution includes 5-40 wt% hydrochloric acid, 5-40 wt% nitric acid, or 5-40 wt% acetic acid.

[0020] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, during the process of concentrating the eluent until rebaudioside B crystallizes out, the crystallization temperature is 30-60°C and the stirring rate is 25-100 rpm.

[0021] Furthermore, in the method for preparing rebaudioside B using stevia mother liquor provided by the present invention, the temperature during filter cake drying is 65–95°C.

[0022] Secondly, the present invention provides a rebaudioside B product, which is prepared according to the above-mentioned method of preparing rebaudioside B using stevia mother liquor saccharide. The rebaudioside B product contains rebaudioside B content >96wt%, the content of other stevia glycosides <2wt%, and the balance is flavonoids. The overall recovery rate of rebaudioside B is >85%.

[0023] Compared with the prior art, the beneficial effects of the rebaudioside B product provided by the present invention are the same as those of the method for preparing rebaudioside B using stevia mother liquor as described in the above technical solution, and will not be repeated here. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 The liquid chromatogram of lebodiin B prepared in Example 3 of this invention is shown. Detailed Implementation

[0026] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0027] Existing technology provides a method for preparing rebaudine B, which involves alkaline hydrolysis of rebaudine I to prepare laminarin and rebaudine B. The specific steps include: maintaining an aqueous solution of rebaudine I at 80℃–100℃ for 0.5 h; adding alkali at a catalyst-to-substrate molar ratio of 1:10–20:1; reacting at 80℃–100℃ for 2–10 h until rebaudine I is completely hydrolyzed; then neutralizing with 0.1 mol / L acid; the laminarin product remains in solution, while the other product, rebaudine B, precipitates out. After filtration, the filter cake is dried to obtain rebaudine B. However, this method is complex, requires harsh reaction conditions, and results in the coexistence of laminarin and rebaudine B in solution after acid neutralization, leading to poor quality of the prepared rebaudine B product. Even recrystallization with alcohol cannot completely remove the impurities.

[0028] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for preparing rebaudioside B using stevia mother liquor saccharide, comprising:

[0029] The solution of stevia mother liquor glycosides is passed through an anion exchange resin column, so that rebaudioside B in the solution is adsorbed by the anion exchange resin, and the remaining stevia glycosides are effluent.

[0030] The anion exchange resin was eluted with an alkaline alcohol solution to obtain an eluent containing rebaudioside B.

[0031] The pH of the eluent was adjusted to 3-4.5 with an acid solution, and the eluent was stirred until rebaudioside B crystals precipitated. After filtration, the filter cake was dried to obtain the rebaudioside B product.

[0032] Using the above technical solution, in the method for preparing rebaudioside B from stevia mother liquor of the present invention, during the process of passing the stevia mother liquor solution through an anion exchange resin column, because rebaudioside B contained in the stevia mother liquor has a carboxyl group at the C19 position, the charge of the sulfonic acid group or hydroxyl group on the surface of the anion exchange resin first interacts with the charge of the rebaudioside B containing the carboxyl group in the solution. Rebaudioside B forms a stable polymer on the surface of the anion exchange resin, allowing it to be adsorbed by the anion exchange resin. Specifically, the anion exchange resin includes a strongly basic anion exchange resin, a polystyrene-type anion exchange resin, or a polyacrylamide-type anion exchange resin. Since the anion exchange resin has a strong adsorption capacity for rebaudioside B, the present invention uses an alkaline alcohol solution with stronger desorption capacity as a desorption agent to desorb the rebaudioside B adsorbed by the anion exchange resin, obtaining an eluent containing rebaudioside B. This invention adjusts the pH of the eluent to 3-4.5, which inhibits the ionization of the carboxyl group of rebaudioside B in the eluent, allowing rebaudioside B to exist in the eluent in a molecular state. After crystallizing and separating the rebaudioside B in the eluent, the rebaudioside B product can be obtained.

[0033] It should be understood that in the method for preparing rebaudioside B using stevia mother liquor of the present invention, in order to improve the desorption efficiency of the alkaline-alcoholic solution for rebaudioside B adsorbed by the anion exchange resin and to improve the recovery rate of rebaudioside B, the present invention also needs to control the concentrations of the alkaline solution and the alcohol solution in the alkaline-alcoholic solution, as well as the mixing ratio of the alkaline solution and the alcohol solution in the alkaline-alcoholic solution. For example, the alkaline-alcoholic solution is a mixture of 30-50 wt% alkaline solution and 60-85 wt% alcohol solution, and the volume ratio of the alkaline solution to the alcohol solution in the alkaline-alcoholic solution is 1:(8-80). Furthermore, when the volume ratio of the alkali solution to the alcohol solution in the alkali-alcohol solution is 1:(30-40), the optimal desorption effect can be achieved, ensuring complete desorption of rebaudioside B while minimizing the destruction of its structure. As another example, the alkali-alcohol solution can be a mixture of 30 wt% alkali solution and 60 wt% alcohol solution, 40 wt% alkali solution and 70 wt% alcohol solution, or 50 wt% alkali solution and 85 wt% alcohol solution, and the volume ratio of the alkali solution to the alcohol solution in the alkali-alcohol solution can be 1:8, 1:25, 1:50, or 1:80.

[0034] It should also be understood that in the method for preparing rebaudioside B using stevia mother liquor of the present invention, in order to improve the desorption efficiency of the alkaline-alcoholic solution for rebaudioside B adsorbed by the anion exchange resin, it is necessary to control the types of the alkaline solution and the alcoholic solution. For example, the alkaline solution includes 30-50 wt% NaOH solution, 30-50 wt% KOH solution, or 30-50 wt% ammonia solution; the alcoholic solution includes 60-85 wt% methanol solution, 60-85 wt% ethanol solution, or 60-85 wt% propanol solution; as another example, the alkaline solution can be 30 wt% NaOH solution, 40 wt% KOH solution, or 50 wt% ammonia solution, and the alcoholic solution can be 60 wt% methanol solution, 70 wt% propanol solution, or 85 wt% ethanol solution.

[0035] It should also be understood that in the method for preparing rebaudioside B using stevia mother liquor of the present invention, in order to achieve saturated adsorption of rebaudioside B in the solution by the anion exchange resin, it is also necessary to control the feed amount of the solution. For example, the feed amount of the solution after drying of solids is 60 to 120 g / 100 ml of the volume of the anion exchange resin; in another example, the feed amount of the solution after drying of solids can be 60 g / 100 ml, 80 g / 100 ml or 120 g / 100 ml of the volume of the anion exchange resin.

[0036] As one possible implementation, in the method for preparing rebaudine B using stevia mother liquor of the present invention, before adjusting the pH of the eluent containing rebaudine B to 3-4.5 with an acid solution, the method further includes: concentrating the eluent to an alcohol concentration of 10-40 vt% and a solid content of 5-20 wt% under conditions of a temperature of 50-90°C and a stirring rate of 25-100 rpm. By using the above technical solution, the present invention, by controlling the alcohol content of the eluent to 10-40 vt% and the solid content to 5-20 wt%, ensures that the rebaudine B in the eluent is in a saturated state, thereby improving the crystallization efficiency of rebaudine B during the crystallization stage. For example, the temperature can be 50°C, 60°C, 80°C, or 90°C, and the stirring rate can be 25 rpm, 45 rpm, 55 rpm, 70 rpm, or 100 rpm.

[0037] As one possible implementation, in the method for preparing rebaudioside B using stevia mother liquor of the present invention, the solution of the stevia mother liquor is a mixed solution of stevia mother liquor and pure water, wherein the mass ratio of stevia mother liquor to pure water in the mixed solution is 1:(4-50); and / or,

[0038] The total glycoside content in the stevia mother liquor is 40-60 wt%, with the remainder being impurities; among the total glycosides, the content of rebaudioside B is 3-12 wt%.

[0039] By employing the above technical solution, the present invention mixes stevia mother liquor sugar and pure water, which disperses rebaudin B and other components in the stevia mother liquor sugar in the pure water, resulting in a uniformly mixed solution. This facilitates the uniform adsorption of rebaudin B by the anion exchange resin when the solution passes through a column. Controlling the mass ratio of stevia mother liquor sugar to pure water in the mixed solution can indirectly control the flowability of the solution and the content of each component in the solution. Furthermore, to improve the yield of rebaudioside B, the present invention controls the total glycoside content in the stevia mother liquor to be 40-60 wt%, and the rebaudioside B content in the total glycosides to be 3-12 wt%. During the column chromatography process of the solution on the anion exchange resin, the anion exchange resin specifically saturates and adsorbs rebaudioside B, so that the adsorption sites on the anion exchange resin are filled with rebaudioside B, and the remaining stevia glycosides and impurities flow out with the effluent. For example, the total glycoside content in the stevia mother liquor can be 40 wt%, 50 wt%, or 60 wt%, and the rebaudioside B content in the total glycosides can be 3 wt%, 5 wt%, 7 wt%, or 12 wt%.

[0040] It should be understood that in the method for preparing rebaudioside B using stevia mother liquor of the present invention, during the process of adjusting the pH of the eluent to 3-4.5 with an acid solution, in order to improve the efficiency of pH adjustment of the eluent and for safety considerations, it is also necessary to control the concentration and type of the acid solution. For example, the concentration of the acid solution is 5-40 wt%. Further, the acid solution includes 5-40 wt% hydrochloric acid, 5-40 wt% nitric acid, or 5-40 wt% acetic acid. In another example, the acid solution can be 5 wt% hydrochloric acid, 25 wt% hydrochloric acid, 30 wt% nitric acid, 40 wt% nitric acid, or 20 wt% acetic acid.

[0041] It should also be understood that in the method for preparing rebaudine B using stevia mother liquor of the present invention, during the process of concentrating the eluent until rebaudine B crystallizes out, in order to improve the crystallization efficiency of rebaudine B, it is also necessary to control the temperature and stirring rate during crystallization. For example, the temperature during crystallization is 30-60°C and the stirring rate is 25-100 rpm; in another example, the temperature during crystallization can be 30°C, 40°C or 60°C, and the stirring rate can be 25 rpm, 40 rpm, 60 rpm or 100 rpm.

[0042] It should also be understood that in the method for preparing rebaudioside B using stevia mother liquor of the present invention, in order to reduce the drying time and avoid damage to the structure of rebaudioside B during drying, the drying temperature needs to be controlled. For example, the drying temperature is 65-95°C, and in another example, the drying temperature can be 65°C, 70°C, 80°C or 95°C.

[0043] Secondly, the present invention provides a rebaudin B product, which is prepared according to the above-mentioned method of preparing rebaudin B using stevia mother liquor saccharide. The rebaudin B product contains rebaudin B content >96wt%, the content of other stevia glycosides <2wt%, and the balance is flavonoids. The overall recovery rate of rebaudin B is >85%.

[0044] Compared with the prior art, the beneficial effects of the rebaudioside B product provided by the present invention are the same as those of the method for preparing rebaudioside B using stevia mother liquor as described in the above technical solution. At the same time, by controlling the content of rebaudioside B in the rebaudioside B product to be >96wt% and the content of other stevia glycosides to be <2wt%, the present invention achieves an overall recovery rate of rebaudioside B >85%, thus obtaining a high-quality rebaudioside B product and maintaining the overall recovery rate of rebaudioside B at a high level.

[0045] To better understand the present invention, specific embodiments are provided below to further illustrate its content; however, the scope of the present invention is not limited to the embodiments described below. Unless otherwise specified, all raw materials used in the following embodiments are commercially available.

[0046] Example 1

[0047] This embodiment provides a method for preparing rebaudioside B using stevia mother liquor saccharide, including the following steps:

[0048] S100, 500g of stevia mother liquor saccharide is dissolved in pure water to obtain a solution; wherein, the mass ratio of stevia mother liquor saccharide to pure water is 1:4, and the total glycoside content of the stevia mother liquor saccharide is 40.9wt% and the rebaudioside B content is 3.1wt%;

[0049] S200, the solution from step S100 is passed through a column of a strong basic anion exchange resin. Rebaudioside B in the solution is adsorbed by the strong basic anion exchange resin, and the remaining steviol glycosides are effluent. The volume of the strong basic anion exchange resin is 420 ml, the flow rate of the solution through the strong basic anion exchange resin is 3 BV / h, and the injection volume of the solution (dry solids) is 120 g / 100 ml of the volume of the strong basic anion exchange resin.

[0050] S300, using 1000 ml of an alkaline-alcoholic solution as the eluent, the rebaudioside B adsorbed by the strongly basic anion exchange resin is eluent to obtain an eluent containing rebaudioside B; wherein, the alkaline-alcoholic solution is a mixture of 30 wt% NaOH solution and 60 wt% methanol solution, and the volume ratio of the NaOH solution to the methanol solution in the alkaline-alcoholic solution is 1:8, and the flow rate of the alkaline-alcoholic solution through the column in the strongly basic anion exchange resin is 2 BV / h;

[0051] S400, 40wt% hydrochloric acid is added to the eluent in step S300 to adjust the pH of the eluent to 3, and the eluent is stirred at 30°C and 100rpm until rebaudioside B crystals precipitate. The eluent is filtered using a Buchner funnel to obtain a rebaudioside B filter cake, and the rebaudioside B filter cake is dried at 65°C to obtain a high-quality rebaudioside B product.

[0052] In this embodiment, a total of 13.8g of rebaudioside B product was prepared. The rebaudioside B product contained 96.5wt% rebaudioside B and 1.4wt% other steviosides. The overall recovery rate of rebaudioside B was 85.9%.

[0053] Example 2

[0054] This embodiment provides a method for preparing rebaudioside B using stevia mother liquor saccharide, including the following steps:

[0055] S100, 500g of stevia mother liquor saccharide is dissolved in pure water to obtain a solution; wherein, the mass ratio of stevia mother liquor saccharide to pure water is 1:50, and the total glycoside content of the stevia mother liquor saccharide is 59.4wt% and the rebaudioside B content is 12.0wt%;

[0056] S200, the solution from step S100 is passed through a polystyrene anion exchange resin column. Rebaudioside B in the solution is adsorbed by the polystyrene anion exchange resin, and the remaining steviol glycosides are effluent. The amount of polystyrene anion exchange resin used is 830 ml, the flow rate of the solution through the polystyrene anion exchange resin is 3 BV / h, and the injection volume of the solution (dry solids content) is 60 g / 100 ml of the polystyrene anion exchange resin volume.

[0057] S300, using 2000 ml of an alkaline-alcoholic solution as the eluent, the rebaudioside B adsorbed by the polystyrene anion exchange resin is eluent to obtain an eluent containing rebaudioside B; wherein, the alkaline-alcoholic solution is a mixture of 50 wt% KOH solution and 85 wt% ethanol solution, and the volume ratio of the KOH solution to the ethanol solution in the alkaline-alcoholic solution is 1:80, and the flow rate of the alkaline-alcoholic solution through the polystyrene anion exchange resin is 2 BV / h;

[0058] S400, under the conditions of 50°C and 25 rpm, the eluent is concentrated to an alcohol concentration of 10 wt% and a solid content of 5 wt%.

[0059] S500: In step S400, 5 wt% nitric acid is added to the concentrated eluent to adjust the pH of the eluent to 4.5. The eluent is stirred at 60°C and 25 rpm until Rebaudioside B crystals precipitate. The eluent is filtered through a Buchner funnel to obtain a Rebaudioside B filter cake. The Rebaudioside B filter cake is then dried at 95°C to obtain a high-quality Rebaudioside B product.

[0060] In this embodiment, a total of 56.1g of rebaudioside B product was prepared. The rebaudioside B product contained 97.4wt% rebaudioside B and 0.8wt% of other steviol glycosides. The overall recovery rate of rebaudioside B was 91.1%.

[0061] Example 3

[0062] This embodiment provides a method for preparing rebaudioside B using stevia mother liquor saccharide, including the following steps:

[0063] S100, 500g of stevia mother liquor saccharide is dissolved in pure water to obtain a solution; wherein, the mass ratio of stevia mother liquor saccharide to pure water is 1:20, and the total glycoside content of the stevia mother liquor saccharide is 49.4wt% and the rebaudioside B content is 8.2wt%.

[0064] S200, the solution from step S100 is passed through a polyacrylamide anion exchange resin column. Rebaudioside B in the solution is adsorbed by the polyacrylamide anion exchange resin, and the remaining steviol glycosides are effluent. The amount of polyacrylamide anion exchange resin used is 500 ml, the flow rate of the solution through the polyacrylamide anion exchange resin is 3 BV / h, and the injection volume of the solution (dry solids content) is 100 g / 100 ml of the volume of the polyacrylamide anion exchange resin.

[0065] S300, using 1500 ml of an alkaline-alcohol solution as the eluent, the rebaudioside B adsorbed by the polyacrylamide anion exchange resin is eluent to obtain an eluent containing rebaudioside B; wherein, the alkaline-alcohol solution is a mixture of 40 wt% ammonia and 70 wt% propanol solution, and the volume ratio of the ammonia to the propanol solution in the alkaline-alcohol solution is 1:40, and the flow rate of the alkaline-alcohol solution through the polyacrylamide anion exchange resin is 2 BV / h;

[0066] S400, under conditions of 90°C and 100 rpm, the eluent is concentrated to an alcohol concentration of 40 wt% and a solid content of 20 wt%.

[0067] S500: 30 wt% acetic acid is added to the concentrated eluent from step S400 to adjust the pH of the eluent to 3.5. The eluent is stirred at 45°C and 50 rpm until Rebaudioside B crystals precipitate. The eluent is filtered through a Buchner funnel to obtain a Rebaudioside B filter cake. The Rebaudioside B filter cake is then dried at 80°C to obtain a high-quality Rebaudioside B product.

[0068] In this embodiment, a total of 38.2g of lebodiin B product was prepared, such as... Figure 1 As shown, liquid chromatography analysis revealed that the rebaudioside B content in the product was 97.1 wt%, while the content of other steviol glycosides was 1.1 wt%. The overall recovery rate of rebaudioside B was 90.5%.

[0069] Example 4

[0070] This embodiment provides a method for preparing rebaudioside B using stevia mother liquor saccharide, including the following steps:

[0071] S100, 500g of stevia mother liquor saccharide is dissolved in pure water to obtain a solution; wherein, the mass ratio of stevia mother liquor saccharide to pure water is 1:35, and the total glycoside content of the stevia mother liquor saccharide is 45.7wt% and the rebaudioside B content is 6.5wt%;

[0072] S200, the solution from step S100 is passed through a column of a strong basic anion exchange resin. Rebaudioside B in the solution is adsorbed by the strong basic anion exchange resin, and the remaining steviol glycosides are eluted as the effluent. The volume of the strong basic anion exchange resin is 520 ml, the flow rate of the solution through the strong basic anion exchange resin is 3 BV / h, and the injection volume of the solution (dry solids content) is 96 g / 100 ml of the volume of the strong basic anion exchange resin.

[0073] S300, using 1000 ml of an alkaline-alcohol solution as the eluent, the rebaudioside B adsorbed by the strongly basic anion exchange resin is eluent to obtain an eluent containing rebaudioside B; wherein, the alkaline-alcohol solution is a mixture of 45 wt% ammonia and 80 wt% ethanol, and the volume ratio of the ammonia to the propanol in the alkaline-alcohol solution is 1:30, and the flow rate of the alkaline-alcohol solution through the column in the strongly basic anion exchange resin is 2 BV / h;

[0074] S400, under the conditions of a temperature of 75°C and a stirring speed of 70 rpm, the eluent is concentrated to an alcohol concentration of 25 wt% and a solid content of 12 wt%.

[0075] S500: 35 wt% acetic acid is added to the concentrated eluent from step S400 to adjust the pH of the eluent to 4.0. The eluent is stirred at 50°C and 60 rpm until Rebaudioside B crystals precipitate. The eluent is filtered through a Buchner funnel to obtain a Rebaudioside B filter cake. The Rebaudioside B filter cake is then dried at 70°C to obtain a high-quality Rebaudioside B product.

[0076] In this embodiment, a total of 29.3g of rebaudioside B product was prepared. The rebaudioside B product contained 96.8wt% rebaudioside B and 1.4wt% of other steviol glycosides. The overall recovery rate of rebaudioside B was 87.3%.

[0077] Comparative Example 1

[0078] The method for preparing rebaudioside B using stevia mother liquor provided in this comparative example is basically the same as that in Example 1, except that in step S300, the 60 wt% methanol solution in the alkaline alcohol solution is replaced by an equal amount of 30 wt% NaOH solution as the eluent to elute the rebaudioside B adsorbed by the strongly basic anion exchange resin, and an eluent is obtained. The concentration of the NaOH solution is the same as that in Example 1.

[0079] In this comparative example, a total of 6.8 g of rebaudioside B product was prepared. The rebaudioside B product contained 93.5 wt% rebaudioside B and 0.4 wt% other steviol glycosides. The overall recovery rate of rebaudioside B was 41.0%.

[0080] It can be seen that, compared with the alkaline alcohol solution, the amount of rebaudioside B adsorbed by the anion exchange resin in this comparative example, using NaOH solution as the eluent, is much lower than the 13.8g of rebaudioside B in Example 1, and the content of rebaudioside B in the rebaudioside B product of this comparative example is much lower than the 96.5wt% in Example 1. This is because the anion exchange resin has a strong adsorption capacity for rebaudioside B, and the alkaline solution cannot completely eluent the rebaudioside B adsorbed by the anion exchange resin.

[0081] Comparative Example 2

[0082] The method for preparing rebaudioside B using stevia mother liquor provided in this comparative example is basically the same as that in Example 1, except that in step S300, the 30wt% NaOH solution in the alkaline alcohol solution is replaced by an equal amount of 60wt% methanol solution as the eluent to elute the rebaudioside B adsorbed by the strongly basic anion exchange resin, and an eluent is obtained. The concentration of the methanol solution is the same as that in Example 1.

[0083] In this comparative example, 1.2 g of rebaudioside B product was prepared. The rebaudioside B product contained 90.7 wt% rebaudioside B and 3.2 wt% other steviol glycosides. The overall recovery rate of rebaudioside B was 7.0%.

[0084] It can be seen that, compared to the alkaline-alcoholic solution, the comparative example using methanol solution as the eluent to elute rebaudine B adsorbed by the anion exchange resin yielded a significantly lower amount of rebaudine B product compared to the 13.8 g in Example 1. Furthermore, the rebaudine B content in the comparative example was significantly lower than the 96.5 wt% in Example 1. This is because the anion exchange resin has a strong adsorption capacity for rebaudine B, and using alcohol solution as the eluent cannot effectively elute the rebaudine B adsorbed by the anion exchange resin. Therefore, this invention, by mixing 30–50 wt% alkaline solution and 60–85 wt% alcohol solution to obtain an alkaline-alcoholic solution, and using this alkaline-alcoholic solution as the eluent, can achieve the elution of rebaudine B adsorbed by the ion exchange resin, obtaining a high-quality rebaudine B product, and maintaining an overall rebaudine B recovery rate above 85%.

[0085] As can be seen from the above embodiments, comparative examples, and test data, under the conditions of the embodiments of the present invention, by mixing 30-50 wt% alkaline solution and 60-85 wt% alcohol solution to obtain an alkaline-alcohol solution, and using the alkaline-alcohol solution as a desorbent, the rebaudioside B adsorbed by the ion exchange resin can be desorbed, resulting in a high-quality rebaudioside B product. The overall recovery rate of rebaudioside B is maintained above 85%, which solves the technical problems of complex preparation process, harsh reaction conditions, and poor quality of rebaudioside B obtained in the prior art.

[0086] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing rebaudioside B from stevia mother liquor sugars, characterized in that, The method comprises the following steps: passing a sweetener solution of a stevia mother liquor through an anion exchange resin column, so that rebaudioside B in the solution is adsorbed by the anion exchange resin, and the rest of the steviol glycosides flow out as effluent; eluting the anion exchange resin with an alkaline alcohol solution to obtain an elution solution containing rebaudioside B; adjusting the pH value of the elution solution to 3-4.5 by using an acid solution, and stirring the elution solution until rebaudioside B is crystallized out, filtering the filter cake, and drying the filter cake to obtain a rebaudioside B product. The alkaline alcohol solution is a mixed solution of 30-50 wt% of an alkaline solution and 60-85 wt% of an alcohol solution, the volume ratio of the alkaline solution to the alcohol solution in the alkaline alcohol solution is 1:(8-80), the alkaline solution comprises 30-50 wt% of a NaOH solution, 30-50 wt% of a KOH solution, or 30-50 wt% of ammonia water, and the alcohol solution comprises 60-85 wt% of a methanol solution, 60-85 wt% of an ethanol solution, or 60-85 wt% of a propanol solution.

2. The method of preparing rebaudioside B from steviol sugar liquor according to claim 1, wherein, The sample amount of the solution of the stevia mother liquor sugar is 60-120 g / 100 ml of the volume of the anion exchange resin.

3. The method of preparing rebaudioside B from steviol sugar liquor of claim 1, wherein, After the elution solution containing rebaudioside B is obtained, and before the pH value of the elution solution is adjusted to 3-4.5 by using an acid solution, the method further comprises the following steps: concentrating the elution solution to an alcohol concentration of 10-40 wt% and a solid content of 5-20 wt% at a temperature of 50-90 ℃ and a stirring speed of 25-100 rpm.

4. The method of preparing rebaudioside B from steviol sugar liquor of claim 1, wherein, The solution of the stevia mother liquor sugar is a mixed solution of the stevia mother liquor sugar and pure water, and the mass ratio of the stevia mother liquor sugar to the pure water in the mixed solution is 1:(4-50); and / or The total glycoside content in the stevia mother liquor sugar is 40-60 wt%, and the rest is impurities; wherein the rebaudioside B content in the total glycosides is 3-12 wt%.

5. The method of preparing rebaudioside B from steviol sugar liquor of claim 1, wherein, In the process of adjusting the pH value of the elution solution to 3-4.5 by using an acid solution, the concentration of the acid solution is 5-40 wt%; and / or The acid solution comprises 5-40 wt% of hydrochloric acid, 5-40 wt% of nitric acid, or 5-40 wt% of acetic acid.

6. The method of preparing rebaudioside B from steviol sugar liquor of claim 1, wherein, In the process of concentrating the elution solution until rebaudioside B is crystallized out, the temperature during crystallization is 30-60 ℃, and the stirring speed is 25-100 rpm.

7. The method of preparing rebaudioside B from steviol sugar liquor of claim 1, wherein, The temperature during drying of the filter cake is 65-95 ℃.

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