A method for recovering rebaudioside b in stevia mother liquor sugar by electrodialysis

Abstract

The application discloses a method for recovering rebaudioside B in stevia mother liquor sugar by electrodialysis, which comprises the following steps: dissolving the stevia mother liquor sugar in a solvent, adjusting the pH of the solution, and obtaining a mother liquor sugar solution; pumping the mother liquor sugar solution into an electrodialysis-ultrafiltration coupling device for separation, processing until the pH of the dilute liquid is lower than 7.5, and ending the processing; combining the materials in the anion chamber and the cation chamber to obtain ion phase materials, and collecting the dilute liquid in the dilute chamber at the same time; concentrating the ion phase materials by using a reverse osmosis membrane, collecting the intercept liquid and the permeate liquid; heating the intercept liquid and adding acid liquid to adjust the pH, and precipitating until the weight of the liquid is unchanged; filtering the liquid, drying the filter cake, and obtaining rebaudioside B products; and vacuum heat-concentrating the dilute liquid and then spray drying to obtain mixed stevia glycoside products. The method uses stevia mother liquor sugar as raw material, and high-content rebaudioside B main products and mixed stevia glycoside by-products are prepared, the added value of the products is improved, and the waste liquid in the process is recycled and utilized, which is economic and environmental.

Description

Technical Field

[0001] This invention relates to the field of rebaudine B production technology, and specifically to a method for recovering rebaudine B from stevia mother liquor using electrodialysis. Background Technology

[0002] Although rebaudioside B is less sweet than rebaudioside A, it has a better taste, no off-flavor, and also has the effect of lowering blood sugar, making it a stevioside compound with great application potential. Currently, the preparation method for rebaudioside B is chemical hydrolysis, but this method requires harsh reaction conditions and generates a large amount of waste liquid during the reaction, which is environmentally unfriendly.

[0003] Currently, many stevia producers inevitably generate a portion of stevia mother liquor after producing their main product, high-content rebaudioside A, and other types of stevia. This mother liquor has low total glycoside content, poor taste, and low economic value. Testing has revealed a high rebaudioside B content in this mother liquor; therefore, finding a way to recover rebaudioside B from the mother liquor is of significant importance.

[0004] Patent CN102093447B discloses a method for purifying steviol glycoside RB. This patent involves adsorbing the mother liquor sugar onto a macroporous adsorption resin column, then eluting the adsorbed steviol glycosides onto the resin column with 70-75 wt% ethanol. The eluent is collected in fractions, concentrated, and precipitated. The resulting solid and liquid are dried separately to obtain crude steviol. The crude steviol obtained by this method contains both rebaudioside B and other steviol glycoside components. To refine rebaudioside B, a 48-hour crystallization process using a mixed solvent is required, followed by solid-liquid separation to obtain a high-content rebaudioside B product. The above method is not only complex to operate, but also suffers from incomplete separation when collecting the rebaudioside B fractions using a single gradient solvent. Furthermore, the crystallization time is long, requiring a mixed solvent for separation during crystallization purification, making solvent recovery difficult. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for recovering rebaudioside B from stevia mother liquor by electrodialysis, which addresses the shortcomings of existing technologies. This method uses low-value stevia mother liquor as raw material to produce a high-content rebaudioside B main product and mixed stevia glycoside by-products, thereby increasing the added value of the products. In addition, the waste liquid in the process is recycled, which is economical and environmentally friendly.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0008] (1) Preparation of mother liquor sugar solution:

[0009] Dissolve the stevia stock solution in a solvent, adjust the pH of the solution, and obtain the stock solution solution.

[0010] (2) Electrodialysis-ultrafiltration coupled treatment:

[0011] The above-mentioned mother liquor sugar solution is pumped into an electrodialysis-ultrafiltration coupling device for separation. The treatment continues until the pH of the desalination solution is below 7.5. After the treatment is completed, the materials in the anion and cation chambers are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0012] (3) Concentration:

[0013] The above-mentioned ionic phase material is concentrated using a reverse osmosis membrane, and the retentate and permeate are collected.

[0014] (4) Acid precipitation:

[0015] The above retentate was heated, and then acid was added to adjust the pH of the solution. The precipitate was allowed to settle until the weight of the solution remained unchanged.

[0016] (5) Filtration and drying:

[0017] The liquid is filtered, and the filter cake is dried to obtain Lebodiin B product;

[0018] (6) Desalination solution treatment:

[0019] The collected desalination liquid was vacuum thermally concentrated and then spray-dried to obtain a mixed steviol glycoside product.

[0020] Preferably, in step (1), the solvent is purified water, and the ratio of stevia mother liquor sugar to solvent is (10-15)g:100ml.

[0021] Preferably, in step (1), the pH adjuster used to adjust the pH of the solution is an alkaline solution, which is either a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 5-40 wt%.

[0022] Preferably, in step (1), the pH of the solution is adjusted to 10-11.

[0023] Preferably, in step (2), during the separation process, the flow rate of the mother liquor sugar solution is 20-40 ml / min; and the effective membrane area is 30-40 cm². 2 The membrane molecular weight is 10,000-20,000, and the electric field strength is 10-15 V / cm.

[0024] Preferably, in step (3), the temperature during reverse osmosis membrane concentration is 30-65℃, the membrane pressure is 3-6MPa, and the solid content of the retentate is 10-20wt%.

[0025] Preferably, in step (3), the permeate is used in the dissolution process of the stevia mother liquor sugar in step (1).

[0026] Preferably, in step (4), the conditions for acid precipitation are: temperature 75-90℃, pH 4.0-5.5.

[0027] Preferably, in step (4), the acid solution is one of hydrochloric acid solution, sulfuric acid solution, and citric acid solution, wherein the concentration of the hydrochloric acid solution is 5-35 wt%, the concentration of the sulfuric acid solution is 5-35 wt%, and the concentration of the citric acid solution is 20-50 wt%.

[0028] Preferably, in step (6), the conditions for vacuum thermal concentration are: vacuum -0.06 to -0.1 MPa, temperature 65-85°C, and concentration to a solid content of 45-60 wt%.

[0029] Preferably, in step (6), the spray drying conditions are: inlet temperature 165-190℃ and outlet temperature 75-90℃.

[0030] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] 1. This invention uses stevia mother liquor syrup as raw material to produce rebaudioside B as the main product and mixed stevia glycoside by-products, thereby improving economic value. Moreover, the method is simple, has a large single batch processing capacity, good separation effect, and produces rebaudioside B with high purity and high yield.

[0032] 2. This invention uses electrodialysis technology to treat the mother liquor sugar solution. By optimizing the process conditions, rebaudine B is effectively separated from other steviol glycosides in the mother liquor sugar, thus achieving the initial enrichment of rebaudine B.

[0033] 3. In this invention, the collected ionic phase material containing rebaudioside B is sequentially treated with membrane and acid precipitation. By optimizing the conditions of this process, impurities are effectively removed, and a high-content rebaudioside B product is obtained. Furthermore, the waste liquid in the membrane treatment process is recycled, which is energy-saving and environmentally friendly.

[0034] 4. This invention also processes the desalination solution during the electrodialysis process and obtains mixed steviol glycoside byproducts, further improving the economic value of the mother liquor sugar. Detailed Implementation

[0035] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0036] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0037] The electrodialysis-coupling devices in the following embodiments and comparative examples are from Jiangsu Zhongding Environmental Engineering Co., Ltd.

[0038] Unless otherwise specified, the reagents used in the following examples and comparative examples are all commercially available products, and the conditions used in the following examples and comparative examples are all conventional conditions in the art.

[0039] Example 1

[0040] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0041] (1) Preparation of mother liquor sugar solution:

[0042] 1 kg of stevia mother liquor saccharide (total glycoside content 68.6 wt%, rebaudioside B content 10.1 wt%) was dissolved in 10 L of purified water. A 20 wt% sodium hydroxide solution was added to the solution to adjust the pH to 10.7, thus obtaining the mother liquor saccharide solution.

[0043] (2) Electrodialysis-ultrafiltration coupled treatment:

[0044] The above-mentioned mother liquor sugar solution was pumped into the electrodialysis-ultrafiltration coupling device (membrane effective area 40 cm²) at a flow rate of 30 ml / min. 2 The membrane molecular weight is 15000. Before electrodialysis, the electrode solution is 8wt% KCl solution. The feed solution to be treated is added to the ion chamber (50v / v% purified water). The separation process is carried out under the condition of electric field strength of 14V / cm until the pH of the desalination solution is lower than 7.5. After the process is completed, the materials in the anion chamber and the cation chamber are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0045] (3) Concentration:

[0046] The above ionic phase material was concentrated using a reverse osmosis membrane (the temperature during concentration was 45°C and the membrane pressure was 4.0 MPa) to obtain a retentate with a solid content of 13 wt%, while the permeate was collected. The permeate was used for the dissolution of stevia mother liquor sugar in step (1).

[0047] (4) Acid precipitation:

[0048] The above retentate was heated to 85°C, and then a 10wt% hydrochloric acid solution was added to adjust the pH of the solution to 4.5. The precipitate was allowed to settle until the weight of the solution remained unchanged.

[0049] (5) Filtration and drying:

[0050] The above liquid was filtered, and the filter cake was dried to obtain 94.8g of rebaudioside B product (rebaudioside B content was 96.1wt%, and the rebaudioside B yield was 90.2%).

[0051] (6) Desalination solution treatment:

[0052] The collected desalination liquid was vacuum thermally concentrated (vacuum -0.08MPa, temperature 75℃) until the solid content of the concentrate was 49wt%. Finally, the concentrate was spray-dried (inlet temperature 185℃, outlet temperature 86℃) to obtain a mixed steviol glycoside product.

[0053] Example 2

[0054] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0055] (1) Preparation of mother liquor sugar solution:

[0056] 1 kg of stevia mother liquor saccharide (total glycoside content 60.4 wt%, rebaudioside B content 3.9 wt%) was dissolved in 7 L of purified water. A 40 wt% potassium hydroxide solution was added to the solution to adjust the pH to 10.0, thus obtaining the mother liquor saccharide solution.

[0057] (2) Electrodialysis-ultrafiltration coupled treatment:

[0058] The above-mentioned mother liquor sugar solution was pumped into the electrodialysis-ultrafiltration coupling device (with an effective membrane area of ​​40 cm²) at a flow rate of 20 ml / min. 2 The membrane molecular weight is 20,000. Before electrodialysis, the electrode solution is 8 wt% KCl solution. The feed solution to be treated is added to the ion chamber (50 v / v% purified water). The separation process is carried out under the condition of electric field strength of 10 V / cm until the pH of the desalination solution is lower than 7.5. After the process is completed, the materials in the anion chamber and the cation chamber are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0059] (3) Concentration:

[0060] The above ionic phase material was concentrated using a reverse osmosis membrane (the temperature during concentration was 65°C and the membrane pressure was 3.0 MPa) to obtain a retentate with a solid content of 10 wt%, while the permeate was collected. The permeate was used for the dissolution of stevia mother liquor sugar in step (1).

[0061] (4) Acid precipitation:

[0062] The above retentate was heated to 90°C, and then a 5 wt% sulfuric acid solution was added to adjust the pH of the solution to 4.0. The precipitate was allowed to settle until the weight of the solution remained unchanged.

[0063] (5) Filtration and drying:

[0064] The above liquid was filtered, and the filter cake was dried to obtain 34.9g of rebaudioside B product (rebaudioside B content was 95.6wt%, and the rebaudioside B yield was 85.5%).

[0065] (6) Desalination solution treatment:

[0066] The collected desalination liquid was vacuum thermally concentrated (vacuum -0.1MPa, temperature 65℃) until the solid content of the concentrate was 45wt%. Finally, the concentrate was spray-dried (inlet temperature 175℃, outlet temperature 81℃) to obtain a mixed steviol glycoside product.

[0067] Example 3

[0068] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0069] (1) Preparation of mother liquor sugar solution:

[0070] 1 kg of stevia mother liquor saccharide (total glycoside content 74.8 wt%, rebaudioside B content 14.2 wt%) was dissolved in 10 L of purified water. A 5 wt% sodium hydroxide solution was added to the solution to adjust the pH to 11, thus obtaining the mother liquor saccharide solution.

[0071] (2) Electrodialysis-ultrafiltration coupled treatment:

[0072] The above-mentioned mother liquor sugar solution was pumped into the electrodialysis-ultrafiltration coupling device (membrane effective area 30 cm²) at a flow rate of 40 ml / min. 2 The membrane molecular weight is 20,000. Before electrodialysis, the electrode solution is 8 wt% KCl solution. The feed solution to be treated is added to the ion chamber (50 v / v% purified water). The separation process is carried out under the condition of electric field strength of 15 V / cm until the pH of the desalination solution is lower than 7.5. After the process is completed, the materials in the anion chamber and the cation chamber are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0073] (3) Concentration:

[0074] The above ionic phase material was concentrated using a reverse osmosis membrane (the temperature during concentration was 30°C and the membrane pressure was 6.0 MPa) to obtain a retentate with a solid content of 20 wt%, while the permeate was collected. The permeate was used for the dissolution of stevia mother liquor sugar in step (1).

[0075] (4) Acid precipitation:

[0076] The above retentate was heated to 75°C, and then a 50wt% citric acid solution was added to adjust the pH of the solution to 5.5. Precipitation continued until the weight of the solution did not change.

[0077] (5) Filtration and drying:

[0078] The above liquid was filtered, and the filter cake was dried to obtain 131.5g of rebaudioside B product (rebaudioside B content was 96.0wt%, and the rebaudioside B yield was 88.9%).

[0079] (6) Desalination solution treatment:

[0080] The collected desalination liquid was vacuum thermally concentrated (vacuum -0.06MPa, temperature 85℃) until the solid content of the concentrate was 60wt%. Finally, the concentrate was spray-dried (inlet temperature 165℃, outlet temperature 75℃) to obtain a mixed steviol glycoside product.

[0081] Example 4

[0082] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0083] (1) Preparation of mother liquor sugar solution:

[0084] 1 kg of stevia mother liquor saccharide (total glycoside content 64.1 wt%, rebaudioside B content 6.4 wt%) was dissolved in 8 L of purified water. A 15 wt% potassium hydroxide solution was added to the solution to adjust the pH to 10.3, thus obtaining the mother liquor saccharide solution.

[0085] (2) Electrodialysis-ultrafiltration coupled treatment:

[0086] The above-mentioned mother liquor sugar solution was pumped into the electrodialysis-ultrafiltration coupling device (with an effective membrane area of ​​30 cm²) at a flow rate of 25 ml / min. 2 The membrane molecular weight is 10000. Before electrodialysis, the electrode solution is 8wt% KCl solution. The feed solution to be treated is added to the ion chamber (50v / v% purified water). The separation process is carried out under the condition of electric field strength of 12V / cm until the pH of the desalination solution is lower than 7.5. After the process is completed, the materials in the anion chamber and the cation chamber are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0087] (3) Concentration:

[0088] The above ionic phase material was concentrated using a reverse osmosis membrane (the temperature during concentration was 39°C and the membrane pressure was 5.4 MPa) to obtain a retentate with a solid content of 15 wt%, while the permeate was collected. The permeate was used for the dissolution of stevia mother liquor sugar in step (1).

[0089] (4) Acid precipitation:

[0090] The above retentate was heated to 81°C, and then a 25 wt% hydrochloric acid solution was added to adjust the pH of the solution to 4.3. The precipitate was allowed to settle until the weight of the solution remained unchanged.

[0091] (5) Filtration and drying:

[0092] The above liquid was filtered, and the filter cake was dried to obtain 57.6g of rebaudioside B product (rebaudioside B content was 95.8wt%, and the rebaudioside B yield was 86.2%).

[0093] (6) Desalination solution treatment:

[0094] The collected desalination liquid was vacuum thermally concentrated (vacuum -0.07MPa, temperature 81℃) until the solid content of the concentrate was 53wt%. Finally, the concentrate was spray-dried (inlet temperature 190℃, outlet temperature 90℃) to obtain a mixed steviol glycoside product.

[0095] Example 5

[0096] A method for recovering rebaudioside B from stevia mother liquor using electrodialysis includes the following steps:

[0097] (1) Preparation of mother liquor sugar solution:

[0098] 1 kg of stevia mother liquor saccharide (total glycoside content 71.5 wt%, rebaudioside B content 12.2 wt%) was dissolved in 9 L of purified water. A 30 wt% sodium hydroxide solution was added to the solution to adjust the pH to 10.5, thus obtaining the mother liquor saccharide solution.

[0099] (2) Electrodialysis-ultrafiltration coupled treatment:

[0100] The above-mentioned mother liquor sugar solution was pumped into the electrodialysis-ultrafiltration coupling device (with an effective membrane area of ​​40 cm²) at a flow rate of 35 ml / min. 2 The membrane molecular weight is 20,000. Before electrodialysis, the electrode solution is 8 wt% KCl solution. The feed solution to be treated is added to the ion chamber (50 v / v% purified water). The separation process is carried out under the condition of electric field strength of 13 V / cm until the pH of the desalination solution is lower than 7.5. After the process is completed, the materials in the anion chamber and the cation chamber are combined to obtain the ionic phase material. At the same time, the desalination solution in the desalination chamber is collected.

[0101] (3) Concentration:

[0102] The above ionic phase material was concentrated using a reverse osmosis membrane (the temperature during concentration was 54°C and the membrane pressure was 4.7 MPa) to obtain a retentate with a solid content of 17 wt%, while the permeate was collected. The permeate was used for the dissolution of stevia mother liquor sugar in step (1).

[0103] (4) Acid precipitation:

[0104] The above retentate was heated to 87°C, and then a 30wt% sulfuric acid solution was added to adjust the pH of the solution to 5.1. The precipitate was allowed to settle until the weight of the solution remained unchanged.

[0105] (5) Filtration and drying:

[0106] The above liquid was filtered, and the filter cake was dried to obtain 112g of rebaudioside B product (rebaudioside B content was 95.8wt%, and the rebaudioside B yield was 87.9%).

[0107] (6) Desalination solution treatment:

[0108] The collected desalination liquid was vacuum thermally concentrated (vacuum -0.09MPa, temperature 69℃) until the solid content of the concentrate was 55wt%. Finally, the concentrate was spray-dried (inlet temperature 181℃, outlet temperature 83℃) to obtain a mixed steviol glycoside product.

[0109] To verify the effectiveness of the method provided by this invention in processing stevia mother liquor syrup, the following description uses Example 1 as a reference and combines several comparative examples for further explanation.

[0110] Comparative Example 1

[0111] Compared with Example 1, the difference is that the pH of the mother liquor sugar solution is 8, and other conditions are the same as in Example 1, yielding 46.4g of rebaudioside B product with a rebaudioside B content of 93.8wt% and a yield of 43.1%.

[0112] Comparative Example 2

[0113] Compared with Example 1, the difference is that in step (2), the electric field strength of the mother liquor sugar solution during the electrodialysis-ultrafiltration coupling treatment is 20V / cm, and other conditions are the same as in Example 1, resulting in 85.4g of Rebaudine B product with a Rebaudine B content of 93.9wt% and a yield of 79.4%.

[0114] Comparative Example 3

[0115] Compared with Example 1, the difference is that in step (2), the electric field strength of the mother liquor sugar solution during the electrodialysis-ultrafiltration coupling treatment is 5V / cm, and other conditions are the same as in Example 1, resulting in 55.2g of Rebaudine B product with a Rebaudine B content of 94.5wt% and a yield of 51.6%.

[0116] Comparative Example 4

[0117] Compared with Example 1, the difference is that in step (3), the solid content of the retentate is 7wt%, and the other conditions are the same as in Example 1, resulting in 87.1g of rebaudioside B product with a content of 96.0wt% and a yield of 82.8%.

[0118] Comparative Example 5

[0119] Compared with Example 1, the difference is that in step (3), the solid content of the retentate is 25wt%, and the other conditions are the same as in Example 1, resulting in 100.9g of rebaudioside B product with a rebaudioside B content of 89.7wt% and a yield of 89.6%.

[0120] Comparative Example 6

[0121] Compared with Example 1, the difference is that in step (4), the pH of the solution was adjusted to 3.0, and other conditions were the same as in Example 1, resulting in 103.7g of Rebaudine B product with a Rebaudine B content of 86.3% and a yield of 88.6%.

[0122] Comparative Example 7

[0123] Compared with Example 1, the difference is that in step (4), the pH of the solution was adjusted to 6.5, and other conditions were the same as in Example 1, resulting in 75.4g of Rebaudine B product with a content of 96.1wt% and a yield of 71.7%.

[0124] Comparative Example 8

[0125] Compared with Example 1, the difference is that in step (4), the retentate was heated to 60°C, and other conditions were the same as in Example 1, resulting in 97.0g of Rebaudine B product with a content of 93.4wt% and a yield of 89.7%.

[0126] Comparative Example 9

[0127] Compared with Example 1, the difference is that in step (4), the retentate was heated to 95°C, and other conditions were the same as in Example 1, resulting in 89.3g of rebaudioside B product with a content of 95.7wt% and a yield of 84.6%.

[0128] As can be seen from the above embodiments and comparative examples, the present invention first adjusts the pH of the mother liquor sugar solution. Under alkaline conditions, rebaudioside B in the mother liquor sugar combines with metal ions. Then, the mother liquor sugar solution is treated by a combination of electrodialysis-ultrafiltration coupling technology, membrane impurity removal, and acid precipitation technology, so that rebaudioside B is separated from other types of steviol glycosides in the mother liquor sugar, thereby obtaining a high content of rebaudioside B. At the same time, by optimizing the various process conditions, the yield of rebaudioside B is also significantly improved.

[0129] Compared to the examples, the pH of the mother liquor sugar solution in Comparative Example 1 was too low, resulting in a significant decrease in the yield of rebaudioside B. This was because the low pH prevented sufficient ionization of rebaudioside B in the mother liquor sugar solution. Comparative Examples 2 and 3 showed that both excessively high and insufficient electric field strength affected the separation effect during electrodialysis-ultrafiltration coupling. Excessive electric field strength led to polarization, which reduced ion transport efficiency, increased resistance, and decreased separation efficiency, thus lowering the yield of rebaudioside B. Conversely, insufficient electric field strength prevented sufficient separation of rebaudioside B, reducing the product yield. In Comparative Examples 4 and 5, the purity of rebaudioside B was affected by both low and high solid content in the retentate. Low solid content resulted in more rebaudioside B dissolving in the water, leading to insufficient precipitation during acid analysis and a low product yield. Conversely, excessively high solid content caused rebaudioside B to precipitate along with impurities, affecting the purity of rebaudioside B. The pH and temperature during acid precipitation both affect the purity and yield of rebaudioside B. In Comparative Example 6, the solution pH was too low; in Comparative Example 7, the solution pH was too high; in Comparative Example 8, the acid precipitation temperature was lowered; and in Comparative Example 9, the acid precipitation temperature was too high. All of these factors affected the purity and yield of rebaudioside B. This is because at low pH or low temperature, impurities will precipitate along with the rebaudioside B product, resulting in a low product content. Conversely, at high pH or high acid precipitation temperature, the product content will be high, but some rebaudioside B product will dissolve in the solvent, thus reducing the yield.

[0130] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for recovering rebaudioside B from stevia mother liquor using electrodialysis, characterized in that, Includes the following steps: (1) Preparation of mother liquor sugar solution: The stevia mother liquor sugar was dissolved in a solvent, and the pH of the solution was adjusted to 10-11 using an alkaline solution to obtain the mother liquor sugar solution. (2) Electrodialysis-ultrafiltration coupled treatment: The above-mentioned mother liquor sugar solution was pumped into an electrodialysis-ultrafiltration coupling device for separation. Treatment continued until the pH of the desalinated solution was below 7.

5. After treatment, the materials from the anion and cation chambers were combined to obtain the ionic phase material. Simultaneously, the desalinated solution in the desalination chamber was collected. During the separation process, the flow rate of the mother liquor sugar solution was 20-40 ml / min; the effective membrane area was 30-40 cm². 2 The membrane molecular weight is 10,000-20,000, and the electric field strength is 10-15 V / cm; (3) Concentration: The above-mentioned ionic phase material is concentrated using a reverse osmosis membrane, and the retentate and permeate are collected. The temperature during reverse osmosis membrane concentration is 30-65℃, the membrane pressure is 3-6MPa, and the solid content of the retentate is 10-20wt%. (4) Acid precipitation: Heat the above retentate to 75-90℃, then add acid to adjust the pH of the solution to 4.0-5.5, and let it precipitate until the weight of the solution does not change. (5) Filtration and drying: The liquid is filtered, and the filter cake is dried to obtain Lebodiin B product; (6) Desalination solution treatment: The collected desalination liquid was vacuum thermally concentrated and then spray-dried to obtain a mixed steviol glycoside product.

2. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (1), the solvent is purified water, and the ratio of stevia mother liquor sugar to solvent is (10-15) g: 100 ml.

3. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (1), the alkaline solution is either sodium hydroxide solution or potassium hydroxide solution, and the concentration of the alkaline solution is 5-40 wt%.

4. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (3), the permeate is used in the dissolution process of the stevia mother liquor sugar in step (1).

5. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (4), the acid solution is one of hydrochloric acid solution, sulfuric acid solution, and citric acid solution, wherein the concentration of the hydrochloric acid solution is 5-35 wt%, the concentration of the sulfuric acid solution is 5-35 wt%, and the concentration of the citric acid solution is 20-50 wt%.

6. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (6), the conditions for vacuum thermal concentration are: vacuum -0.06 to -0.1 MPa, temperature 65-85℃, and concentration to a solid content of 45-60 wt%.

7. The method for recovering rebaudioside B from stevia mother liquor using electrodialysis according to claim 1, characterized in that, In step (6), the spray drying conditions are: inlet temperature 165-190℃ and outlet temperature 75-90℃.