A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor syrup

Abstract

This invention discloses a method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor, comprising the following steps: dissolving stevia mother liquor in purified water to obtain a stevia mother liquor solution; adding a pH adjuster to the stevia mother liquor solution to adjust the pH to 6.5-7.0, obtaining a solution to be treated; filtering the solution to be treated once using a hollow fiber membrane, and washing the retentate with purified water to obtain a retentate and a permeate; subjecting the permeate to vacuum concentration and spray drying sequentially to obtain a mixture of steviol glycosides; heating the retentate and adjusting the pH to 4.5-5.0, performing sedimentation treatment, filtering while hot, and drying the filter cake to obtain the rebaudioside B product. This invention uses stevia mother liquor as raw material to produce a mixture of steviol glycosides with high total glycoside content, rebaudioside B, and feed additives, improving the economic value of stevia mother liquor. The process is simple, easy to operate, and suitable for large-scale industrial production, with significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of steviol glycoside recovery technology, specifically to a method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor. Background Technology

[0002] Steviosides are a modern, novel natural sweetener extracted from the leaves of stevia, a perennial herbaceous plant belonging to the Asteraceae family. Characterized by high sweetness and low calories, they are an ideal sweetener to replace sucrose. Rebaudioside B is the active ingredient isolated from stevia, and its sweetness is 150 times that of sucrose. While less sweet than rebaudioside A, its aftertaste is significantly less bitter, resulting in a superior taste. In addition to its sweetness, studies have found that rebaudioside B also regulates blood sugar and lipids, relieves constipation, and promotes metabolism. It can be used as an adjunct treatment for diseases such as diabetes and hyperlipidemia, making it a stevioside compound with significant application potential.

[0003] The traditional preparation process of rebaudine B involves the hydrolysis of rebaudine A. While this method yields a high content of rebaudine B, the raw material price is high. Currently, the preparation of steviol glycosides generates a portion of stevia mother liquor. This mother liquor has a low total glycoside content, poor taste, and low economic value, but it contains a certain amount of rebaudine B. Therefore, recovering rebaudine B from the mother liquor would not only increase its economic value but also reduce the preparation cost of rebaudine B. Current methods for recovering rebaudine B from stevia mother liquor mainly involve using macroporous adsorption resins to adsorb steviol glycosides from the mother liquor solution, followed by elution with ethanol solutions of different concentrations. The eluent is collected in segments, concentrated, and precipitated to obtain crude stevia, which is then purified using solvents. However, these methods generate a large amount of waste liquid, have poor separation efficiency, and are difficult to recover the solvent. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for recovering steviol glycoside mixtures and rebaudioside B from stevia mother liquor, addressing the shortcomings of existing technologies. This invention uses stevia mother liquor as raw material and utilizes the high-efficiency separation characteristics of hollow fiber membranes to achieve preliminary separation of the steviol glycoside mixture, rebaudioside B, and most impurities. Then, under certain conditions, acid precipitation is performed to obtain a steviol glycoside mixture with high total glycoside content, rebaudioside B, and feed additives, thereby improving the economic value of stevia mother liquor. The entire process is simple, easy to operate, and suitable for large-scale industrial production, demonstrating significant economic and social benefits.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor sugars includes the following steps:

[0007] (1) Dissolving raw materials:

[0008] Stevia stock solution was dissolved in purified water to obtain a stevia stock solution.

[0009] (2) pH adjustment:

[0010] Add a pH adjuster to the above stevia mother liquor sugar solution to adjust the pH of the solution to 6.5-7.0 to obtain the solution to be treated;

[0011] (3) Hollow fiber membrane separation:

[0012] The above-mentioned liquid to be treated was filtered once using a hollow fiber membrane, and purified water was added to the retentate for washing to obtain retentate and permeate;

[0013] (4) Preparation of steviol glycosides:

[0014] The above permeate was first concentrated under vacuum and then spray-dried to obtain a mixture with high content of steviol glycosides.

[0015] (5) Preparation of Lebaudi Glycoside B:

[0016] The retentate was heated and its pH was adjusted to 4.5-5.0 for sedimentation. After sedimentation, it was filtered while hot and the filter cake was dried to obtain Lebodiin B product.

[0017] Preferably, in step (1), the concentration of the stevia mother liquor sugar solution is 0.1-0.2 g / ml.

[0018] Preferably, in step (2), the pH adjuster is one of calcium oxide and calcium hydroxide.

[0019] Preferably, in step (3), the hollow fiber membrane used for filtration is of model NF-10 to 20; the material of the hollow fiber membrane is polyvinylidene fluoride, the membrane operating pressure is 0.3-0.5 MPa, and after the membrane has been running for 20-40 minutes, the permeate is back-fed for 30-60 seconds.

[0020] Preferably, in step (3), when the retentate is filtered to 10-15% of the original volume, purified water is added to the retentate to carry the material. The amount of purified water added is half the volume of the retentate. This process is repeated 2-3 times.

[0021] Preferably, in step (4), the vacuum concentration temperature is 60-80℃, the vacuum degree is -0.06~-0.1MPa, and the solid content of the concentrate after vacuum concentration is 30-55wt%.

[0022] Preferably, in step (4), the inlet temperature during spray drying is 160-190℃ and the outlet temperature is 70-95℃.

[0023] Preferably, in step (5), the settling temperature is 75-90℃ and the time is 1-3h.

[0024] Preferably, in step (5), the pH is adjusted using one of hydrochloric acid, acetic acid, and citric acid.

[0025] Preferably, in step (5), the filter cake is washed with purified water 1-2 times during filtration, and the washing liquid and filtrate are combined and dried to obtain feed additive.

[0026] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. This invention uses stevia mother liquor as raw material and combines hollow fiber membrane separation and acid precipitation technologies to separate rebaudioside B and other steviol glycosides, obtaining a mixture of steviol glycosides with high total glycoside content and rebaudioside B, and also obtaining by-product feed additives, thereby improving the economic value of stevia mother liquor.

[0028] 2. In this invention, stevia mother liquor sugar is dissolved in water and the pH of the solution is effectively adjusted. Then, hollow fiber membrane separation is used. Based on the high efficiency separation characteristics of hollow fiber membrane and reasonable adjustment of separation conditions, the initial separation of steviol glycoside mixture from rebaudioside B and most impurities is achieved, ensuring the high purity of steviol glycoside mixture product.

[0029] 3. This invention effectively regulates the temperature and pH during the precipitation of rebaudine B, effectively promoting the precipitation and purification of rebaudine B and improving the product yield and purity. This invention also recovers feed additives derived from the waste liquid generated during the process, further enhancing the economic value of stevia mother liquor saccharide.

[0030] 4. The entire process of this invention is simple, easy to operate, and suitable for large-scale industrial production, with significant economic and social benefits. Detailed Implementation

[0031] 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.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0033] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available, and all conditions are conventional technical conditions in the art.

[0034] Example 1

[0035] A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor; comprising the following steps:

[0036] (1) Dissolve 2.0 kg of stevia mother liquor sugar (total glycoside content 60.5 wt%, rebaudioside B content 3.9 wt%) in 10 L of purified water to obtain stevia mother liquor sugar solution;

[0037] (2) Add calcium oxide to the above stevia mother liquor sugar to adjust the pH of the solution to 6.5, and obtain the solution to be treated;

[0038] (3) The liquid to be treated was filtered using a polyvinylidene fluoride hollow fiber membrane (Singapore San Yi Membrane Technology Co., Ltd., membrane model NF-20) at a membrane pressure of 0.3 MPa. Every 40 minutes of membrane operation, the permeate was back-fed for 60 seconds. When the concentration was reduced to 10% of the original volume, half the volume of purified water was added to the concentrate and the filtration was continued. This process was repeated twice, and the retentate and permeate were collected.

[0039] (4) The above permeate was concentrated at a temperature of 60°C and a vacuum of -0.1 MPa to obtain a concentrate with a solid content of 55 wt%. The concentrate was spray-dried (inlet temperature 190°C, outlet temperature 95°C) to obtain 1277 g of high-content steviol glycoside mixture (total glycoside content 85.5 wt%).

[0040] (5) Heat the above retentate to 75°C, add hydrochloric acid to adjust the pH of the solution to 4.5, precipitate for 3 hours, filter while hot after precipitation, wash the precipitate with purified water, dry the filter cake to obtain 72.1g of rebaudioside B product, the content of rebaudioside B is 95.4wt%, the yield is 88.2%, the washing liquid and filtrate are mixed and dried to obtain feed additive.

[0041] Example 2

[0042] A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor; comprising the following steps:

[0043] (1) Dissolve 2.0 kg of stevia mother liquor sugar (total glycoside content 74.5 wt%, rebaudioside B content 14.1 wt%) in 20 L of purified water to obtain stevia mother liquor sugar solution;

[0044] (2) Add calcium hydroxide to the above stevia mother liquor sugar to adjust the pH of the solution to 7.0, and obtain the solution to be treated;

[0045] (3) The liquid to be treated was filtered using a polyvinylidene fluoride hollow fiber membrane (Singapore San Yi Membrane Technology Co., Ltd., membrane model NF-10) at a membrane pressure of 0.5 MPa. Every 20 minutes of membrane operation, the permeate was back-fed for 30 seconds. When the concentration was reduced to 15% of the original volume, half the volume of purified water was added to the concentrate and the filtration was continued. This process was repeated 3 times, and the retentate and permeate were collected.

[0046] (4) The above permeate was concentrated at a temperature of 80°C and a vacuum of -0.06 MPa to obtain a concentrate with a solid content of 30 wt%. The concentrate was spray-dried (inlet temperature 165°C, outlet temperature 70°C) to obtain 1356 g of high-content steviol glycoside mixture (total glycoside content 86.3 wt%).

[0047] (5) Heat the above retentate to 90°C, add acetic acid to adjust the pH of the solution to 5.0, precipitate for 1 hour, filter while hot after precipitation, wash the precipitate with purified water, dry the filter cake to obtain 259.6g of rebaudioside B product, the content of rebaudioside B is 96.0wt%, the yield is 88.4%, the washing liquid and filtrate are mixed and dried to obtain feed additive.

[0048] Example 3

[0049] A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor; comprising the following steps:

[0050] (1) Dissolve 2.0 kg of stevia mother liquor sugar (total glycoside content 67.1 wt%, rebaudioside B content 6.2 wt%) in 17 L of purified water to obtain stevia mother liquor sugar solution;

[0051] (2) Add calcium oxide to the above stevia mother liquor sugar to adjust the pH of the solution to 6.7, and obtain the solution to be treated;

[0052] (3) The liquid to be treated was filtered using a polyvinylidene fluoride hollow fiber membrane (Singapore San Yi Membrane Technology Co., Ltd., membrane model NF-15) at a membrane pressure of 0.4 MPa. Every 30 minutes of membrane operation, the permeate was back-fed for 40 seconds. When the concentration was reduced to 12% of the original volume, half the volume of purified water was added to the concentrate and the filtration was continued. This process was repeated twice, and the retentate and permeate were collected.

[0053] (4) The above permeate was concentrated at a temperature of 65°C and a vacuum of -0.09 MPa to obtain a concentrate with a solid content of 42 wt%. The concentrate was spray-dried (inlet temperature 175°C, outlet temperature 78°C) to obtain 1378 g of high-content steviol glycoside mixture (total glycoside content 85.8 wt%).

[0054] (5) Heat the above retentate to 81°C, add citric acid to adjust the pH of the solution to 4.7, precipitate for 2 hours, filter while hot after precipitation, wash the precipitate with purified water, dry the filter cake to obtain 114.3g of rebaudioside B product, the content of rebaudioside B is 95.5wt%, the yield is 88.0%, the washing liquid and filtrate are mixed and dried to obtain feed additive.

[0055] Example 4

[0056] A method for recovering a mixture of steviol glycosides and rebaudioside B from stevia mother liquor; comprising the following steps:

[0057] (1) Dissolve 2.0 kg of stevia mother liquor sugar (total glycoside content 72.3 wt%, rebaudioside B content 10.8 wt%) in 13 L of purified water to obtain stevia mother liquor sugar solution;

[0058] (2) Add calcium hydroxide to the above stevia mother liquor sugar to adjust the pH of the solution to 6.8, and obtain the solution to be treated;

[0059] (3) The liquid to be treated was filtered using a polyvinylidene fluoride hollow fiber membrane (Singapore San Yi Membrane Technology Co., Ltd., membrane model NF-15) at a membrane pressure of 0.4 MPa. Every 30 minutes of membrane operation, the permeate was back-fed for 50 seconds. When the concentration was reduced to 13% of the original volume, half the volume of purified water was added to the concentrate and the filtration was continued. This process was repeated 3 times, and the retentate and permeate were collected.

[0060] (4) The above permeate was concentrated at a temperature of 75°C and a vacuum of -0.07 MPa to obtain a concentrate with a solid content of 51 wt%. The concentrate was spray-dried (inlet temperature 186°C, outlet temperature 86°C) to obtain 1401 g of high-content steviol glycoside mixture (total glycoside content 86.5 wt%).

[0061] (5) Heat the above retentate to 86°C, add hydrochloric acid to adjust the pH of the solution to 4.8, precipitate for 2 hours, filter while hot after precipitation, wash the precipitate with purified water, dry the filter cake to obtain 202.2g of rebaudioside B product, the content of rebaudioside B is 96.2wt%, the yield is 90.1%, the washing liquid and filtrate are mixed and dried to obtain feed additive.

[0062] Comparative Example 1

[0063] Compared with Example 4, the difference is that the concentration of the stevia mother liquor sugar solution is 0.3 g / ml, and other conditions are the same as in Example 4, yielding 1338 g of high-content steviol glycoside mixture (total glycoside content 85.2 wt%); 185.1 g of rebaudioside B product, with a rebaudioside B content of 92.4 wt% and a yield of 79.2%.

[0064] Comparative Example 2

[0065] Compared with Example 4, the difference is that the pH of the solution to be treated is 5.5, and other conditions are the same as in Example 4, yielding 1517g of a high-content steviol glycoside mixture (total glycoside content 80.1wt%), 167.6g of rebaudioside B product, with a rebaudioside B content of 94.3wt% and a yield of 73.2%.

[0066] Comparative Example 3

[0067] Compared with Example 4, the difference is that the pH of the solution to be treated is 8.0, and other conditions are the same as in Example 4, yielding 1354g of a high-content steviol glycoside mixture (total glycoside content 86.3wt%) and 203.9g of rebaudioside B product, with a rebaudioside B content of 91.4wt% and a yield of 86.3%.

[0068] Comparative Example 4

[0069] Compared with Example 4, the difference is that in step (3), the membrane pressure is 0.2 MPa, and the other conditions are the same as in Example 4, resulting in 1327 g of high-content steviol glycoside mixture (total glycoside content 86.1 wt%), 191.0 g of rebaudioside B product, with a rebaudioside B content of 90.7 wt% and a yield of 80.2%.

[0070] Comparative Example 5

[0071] Compared with Example 4, the difference is that in step (3), the permeate is not used for backfeeding, and the other conditions are the same as in Example 4, resulting in 1295g of high-content steviol glycoside mixture (total glycoside content 85.2wt%), 192.8g of rebaudioside B product, with a rebaudioside B content of 90.9wt% and a yield of 81.1%.

[0072] Comparative Example 6

[0073] Compared with Example 4, the difference is that in step (3), purified water is not used for washing, and the product is directly concentrated to 13% of the original volume. Other conditions are the same as in Example 4, resulting in 1106g of high-content steviol glycoside mixture (total glycoside content 86.1wt%), 176.4g of rebaudioside B product, with a rebaudioside B content of 92.4wt% and a yield of 75.5%.

[0074] Comparative Example 7

[0075] Compared with Example 4, the difference is that in step (5), the pH during precipitation treatment is 4.0, and other conditions are the same as in Example 4, resulting in 1399g of a high-content steviol glycoside mixture (total glycoside content 86.0wt%), 243.0g of rebaudioside B product, with a rebaudioside B content of 83.1wt% and a yield of 93.5%.

[0076] Comparative Example 8

[0077] Compared with Example 4, the difference is that in step (5), the pH during precipitation treatment is 6.0, and other conditions are the same as in Example 4, resulting in 1411g of a high-content steviol glycoside mixture (total glycoside content 85.9wt%), 162.1g of rebaudioside B product, with a rebaudioside B content of 96.1wt% and a yield of 72.1%.

[0078] Comparative Example 9

[0079] Compared with Example 4, the difference is that in step (5), the temperature during precipitation treatment is 60°C, and other conditions are the same as in Example 4, resulting in 1398g of a high-content steviol glycoside mixture (total glycoside content 86.4wt%), 218.9g of rebaudioside B product, with a rebaudioside B content of 91.5wt% and a yield of 92.7%.

[0080] Comparative Example 10

[0081] Compared with Example 4, the difference is that in step (5), the temperature during precipitation treatment is 95°C, and other conditions are the same as in Example 4, resulting in 1405g of a high-content steviol glycoside mixture (total glycoside content 86.1wt%), 188.7g of rebaudioside B product, with a rebaudioside B content of 96.0wt% and a yield of 83.9%.

[0082] In summary, compared with the comparative example, this invention, by optimizing the conditions in the processing, obtained a mixture of steviol glycosides with high total glycoside content and high content of rebaudioside B, thereby improving the economic value of stevia mother liquor sugar. Moreover, the entire process generates less waste liquid, making it energy-saving and environmentally friendly.

[0083] Compared with the embodiments of the present invention, in Comparative Example 1, when the solid content of the stevia mother liquor sugar solution was relatively high, the yield of the steviol glycoside mixture and the yield of rebaudioside B decreased significantly, and the purity also decreased. This was mainly because when the solid content of the stevia mother liquor sugar solution was high, the separation effect was poor when using a hollow fiber membrane. In Comparative Examples 2 and 3, the yield and purity of the steviol glycoside mixture and rebaudioside B were affected by whether the pH of the stevia mother liquor sugar solution was too high or too low. This was because under conditions of excessively high pH, ​​too much calcium salt was added, which caused other steviol glycosides or impurities besides rebaudioside B to bind with calcium ions. Under conditions of excessively low pH, rebaudioside B in the stevia mother liquor sugar could not fully complex with calcium ions.

[0084] When using hollow fiber membranes to treat the liquid to be treated, the filtration and concentration conditions are also extremely critical. In Comparative Example 4, if the membrane pressure is too low, some impurities will be retained by the hollow fiber membrane along with the complexed rebaudioside B. In Comparative Example 5, if the permeate is not used for backflushing the hollow fiber membrane during the filtration and concentration process, it will cause fouling of the hollow fiber membrane, thereby affecting its filtration efficiency and reducing the purity of rebaudioside B and the yield of the steviol glycoside mixture. In Comparative Example 6, without washing with purified water, the steviol glycoside mixture in the retentate cannot be fully separated, which not only reduces the yield of the steviol glycoside mixture but also reduces the purity of rebaudioside B; moreover, without washing, other steviol glycosides, as impurities, affect the precipitation of rebaudioside B, thus affecting the content of rebaudioside B.

[0085] Temperature and pH are critical when separating and purifying rebaudioside B in the retentate. In Comparative Example 7, under conditions of too low pH, other impurities precipitated along with rebaudioside B; in Comparative Example 8, under conditions of too high pH, ​​rebaudioside B could not be fully precipitated; in Comparative Example 9, if the precipitation temperature was too low, impurities precipitated along with rebaudioside B; while if the precipitation temperature was too high, rebaudioside B could not be fully separated.

[0086] 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 of recovering a steviol glycoside mixture and rebaudioside B in a stevia mother liquor sugar, characterized by, The method comprises the following steps: (1) dissolving raw materials: Dissolve the stevia mother liquor sugar in purified water to obtain a stevia mother liquor sugar solution; (2) pH adjustment: Add a pH adjuster to the stevia mother liquor sugar solution to adjust the pH of the solution to 6.5-7.0 to obtain a solution to be treated; (3) hollow fiber membrane separation: Filter the solution to be treated once using a hollow fiber membrane, and add purified water to the retentate for washing to obtain a retentate and a permeate; (4) preparation of a steviol glycoside mixture: Vacuum concentrate the permeate, and then spray dry it to obtain a high-content steviol glycoside mixture; (5) preparation of rebaudioside B: Heat the retentate in step (3) and adjust its pH to 4.5-5.0, then perform a settling treatment, filter the retentate while it is hot after the settling treatment, dry the filter cake, and obtain a rebaudioside B product; the settling treatment is performed at a temperature of 75-90℃ for 1-3h.

2. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor sugar according to claim 1, characterized in that: In step (1), the concentration of the stevia mother liquor sugar solution is 0.1-0.2g / ml.

3. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (2), the pH adjuster is one of calcium oxide and calcium hydroxide.

4. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (3), the hollow fiber membrane used for filtration has a model number of NF-10-20; the material of the hollow fiber membrane is polyvinylidene fluoride, the membrane operating pressure is 0.3-0.5MPa, and the permeate is used as a back feed for 30-60s after the membrane is operated for 20-40min.

5. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, characterized in that: In step (3), when the volume of the retentate is 10-15% of the original volume, add purified water to the retentate, the amount of the purified water added is half of the volume of the retentate, and repeat this process 2-3 times.

6. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (4), the vacuum concentration is performed at a temperature of 60-80℃ and a vacuum degree of -0.06- -0.1MPa, and the solid content of the concentrated solution after vacuum concentration is 30-55wt%.

7. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (4), the inlet temperature of the spray dryer is 160-190℃, and the outlet temperature is 70-95℃.

8. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (5), one of hydrochloric acid, acetic acid, and citric acid is used to adjust the pH.

9. The method of recovering a steviol glycoside mixture and rebaudioside B from a stevia mother liquor of claim 1, wherein: In step (5), the filter cake is washed 1-2 times using purified water during filtration, and the washing liquid and the filtrate are combined and dried to obtain a feed additive.