A process for preparing rebaudioside b using stevia mother liquor sugar

Abstract

The present application relates to the technical field of glycoside product, and particularly relates to a process method for preparing rebaudioside B by using stevia mother liquor sugar, comprising the following steps: (1) taking the mother liquor sugar, dissolving in purified water and reserving; (2) taking the mother liquor sugar solution, adjusting pH, adding an extractant and stirring, collecting the extraction phase and the extraction residue phase; (3) taking the extraction phase, adding a back-extracting agent and stirring, collecting the back-extraction phase and the back-extraction residue phase; (4) taking the back-extraction phase, adjusting pH, concentrating, heating, adjusting pH, stirring, filtering, collecting the filtrate and the filter cake, drying the filter cake to obtain the rebaudioside B product; (5) taking the extraction residue phase, drying to obtain a first by-product; (6) taking the back-extraction residue phase, concentrating to obtain a first concentrated solution; taking the filtrate, concentrating, and combining with the first concentrated solution, drying to obtain a second by-product. The process method can recycle the rebaudioside B in the mother liquor sugar, greatly improves the yield, the yield and the purity, and increases the economic benefits of enterprises.

Description

Technical Field

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

[0002] Stevia glycosides 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 (RB) is the active ingredient isolated from stevia, and its sweetness is 150 times that of sucrose. Although rebaudioside B is less sweet than the main product rebaudioside A (RA), its aftertaste is significantly less bitter, making RB's taste noticeably superior to RA. Besides its use as a sweetener, studies have found that rebaudioside B also has effects such as regulating blood sugar and lipids, relieving constipation, and promoting metabolism. It can be used as an adjunct treatment for diseases such as diabetes and hyperlipidemia, making it a stevia glycoside compound with significant application potential.

[0003] Traditional processes use rebaudioside A hydrolysis to obtain rebaudioside B, which, while yielding high-content rebaudioside B, significantly impacts the yield of the main product. For example, patent CN 102093447 B discloses a purification method for steviol glycoside RB. This patent adsorbs the mother liquor sugar onto a macroporous adsorption resin column, then elutes the adsorbed steviol glycosides onto the resin column with 70-75% ethanol. The eluent is collected in segments, concentrated, precipitated, and 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. Further refining of rebaudioside B requires crystallization in a mixed solvent for 48 hours, followed by solid-liquid separation to obtain a high-content rebaudioside B product. This patent has a small single-batch resin processing capacity, uses a single gradient solvent for segmented collection of the rebaudioside B segment, resulting in incomplete separation, and has a long crystallization time. Crystallization purification requires separation with a mixed solvent, and solvent recovery is difficult.

[0004] Currently, many stevia producers inevitably generate a portion of stevia mother liquor after producing their main product, high-content rebaudioside A, and other grades of stevia. This mother liquor has low total glycoside content, poor taste, and low economic value. Rebaudioside B is significantly enriched in this type of mother liquor, and how to recover rebaudioside B from the mother liquor has become one of the urgent problems to be solved by stevia producers. Therefore, to address the above-mentioned technical problems, this invention develops a process for recovering high-purity rebaudioside B from stevia mother liquor. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a process for preparing rebaudioside B using stevia mother liquor saccharide, which greatly improves the yield, output and purity of rebaudioside B, thereby increasing economic benefits for enterprises.

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

[0007] A process for preparing rebaudioside B using stevia mother liquor saccharide, the process comprising the following steps:

[0008] (1) Take the mother liquor sugar obtained during the stevia production process, add it to purified water and stir to dissolve it. The resulting mother liquor sugar solution is ready for use.

[0009] (2) Take the mother liquor sugar solution mentioned in step (1), adjust the pH to acidic, add the extractant and stir, and collect the extract phase and raffinate phase respectively;

[0010] (3) Take the extract phase from step (2), add the back-extraction agent and stir, and collect the back-extraction phase and the back-extraction residue phase respectively;

[0011] (4) Take the back-extraction phase from step (3), adjust the pH, heat the concentrated liquid after concentration, adjust the pH to acidic, keep warm and stir for a period of time, filter, collect the filtrate and filter cake respectively, and the filter cake is dried to obtain a product with a content of not less than 95 wt% of Lebaudi glycoside B.

[0012] (5) Take the raffinate from step (2), concentrate and dry it to obtain the first by-product;

[0013] (6) Take the back-extraction residue from step (3) and concentrate it to obtain a first concentrate; take the filtrate from step (4), concentrate it to obtain a second concentrate, combine it with the first concentrate, and dry it to obtain a second byproduct.

[0014] As an improved technical solution, the concentration of the mother liquor sugar solution in step (1) is 20-40 wt%, and the total glycoside content of the mother liquor sugar is 60-75 wt%, and the content of rebaudioside B is 3-10 wt%.

[0015] As an improved technical solution, in step (2), 5-15 wt% hydrochloric acid, nitric acid or sulfuric acid is used to adjust the pH to 2-3.5.

[0016] As an improved technical solution, in step (2), the extractant is water-saturated ethyl acetate, and the mother liquor sugar solution is mixed with the water-saturated ethyl acetate in a volume ratio of 1:1-3, and the extraction is performed 3-6 times.

[0017] As an improved technical solution, in step (3), the back-extraction agent is 0.5-1 wt% NaOH solution, KOH solution, or 1-2 wt% Na2CO3 solution, and the extractant phase and the back-extraction agent are mixed in a volume ratio of 1-3:1, and back-extracted 3-6 times.

[0018] As an improved technical solution, in step (4), 5-15 wt% hydrochloric acid, sulfuric acid or nitric acid is added to the back-extraction phase to adjust the pH to 7.5-8.5, and then the solution is concentrated using a nanofiltration membrane with a molecular weight cutoff of 200-800 Da to obtain a concentrate with a solid content of 5-10 wt%.

[0019] As an improved technical solution, the concentrated liquid in step (4) is heated to 50-70°C, kept warm, and 5-15wt% of hydrochloric acid, sulfuric acid or nitric acid is added to adjust the pH to 3-4. After stirring for 1-3 hours, it is filtered.

[0020] As an improved technical solution, the filtrate in step (6) is filtered using a nanofiltration membrane with a molecular weight cutoff of 200-800 Da, and the collected filtrate is then concentrated.

[0021] After adopting the above technical solution, the beneficial effects of the present invention are:

[0022] This invention utilizes the mother liquor obtained during stevia production. After dissolving in purified water and adjusting the pH to acidic, an extractant is added. The extracted phase is then subjected to back-extraction, followed by pH adjustment, concentration, and heating. The pH is then adjusted again to acidic, and the mixture is kept at this temperature and stirred for a period. The collected filter cake is dried to obtain a product with a rebaudioside B content of not less than 95 wt%. The raffinate from the extraction process is concentrated, and after solvent removal, a first byproduct with a total glycoside content of 80-90 wt% is obtained. The concentrated extracts from the back-extraction phase and the filtrate are combined and dried to obtain a product with a total glycoside content of less than 10 wt%, which can be used as a feed additive. This process is simple to operate and allows for the recovery of rebaudioside B from the mother liquor, significantly improving yield, purity, and output. It also yields other products, increasing economic benefits for enterprises. Attached Figure Description

[0023] Figure 1 This is the liquid phase detection spectrum of rebaudioside B in Example 3 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example 1

[0026] A process for preparing rebaudioside B using stevia mother liquor saccharide includes the following steps:

[0027] (1) Take 20 kg of mother liquor sugar (total glycoside content of 62.3 wt% and rebaudioside B content of 3.6 wt%) obtained during the production of stevia sugar, add it to purified water, stir to dissolve and make up to 100 L to obtain a 20 wt% mother liquor sugar solution for later use.

[0028] (2) Take 100L of the mother liquor sugar solution mentioned in step (1), adjust the pH to 2 with 5wt% hydrochloric acid, and add 100L of extractant (water-saturated ethyl acetate) in a single volume ratio of 1:1 and stir. After three extractions, collect 298L of extract phase and 102L of raffinate phase.

[0029] (3) Take 298L of the extract phase from step (2), add 298L of the back-extraction agent (0.5wt% NaOH solution) in a single volume ratio of 1:1 and stir. After three back-extractions, collect 895L of the back-extraction phase and 297L of the back-extraction residue.

[0030] (4) Take 895L of the back-extraction phase from step (3), add 5wt% hydrochloric acid to adjust the pH to 7.5, and then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 200Da (concentration pressure is 1.5MPa and temperature is 20℃) to obtain a concentrate with a solid content of 5wt%. Heat it to 50℃, keep it warm, add 5wt% hydrochloric acid to adjust the pH to 3, keep it warm and stir for 1h, filter it, collect 32L of filtrate and 1570g of filter cake, and dry the filter cake at 70℃ for 12h to obtain the Lebodi glycoside B product.

[0031] (5) Take 102L of the raffinate from step (2), concentrate it with a nanofiltration membrane with a molecular weight cutoff of 200 Da (concentration pressure is 1.5 MPa, temperature is 20℃), concentrate it to a solid content of 25 wt%, and then spray dry it (inlet temperature is 165℃, outlet temperature is 70℃) to obtain the first by-product.

[0032] (6) Take 297L of the back-extraction residue from step (3) and heat concentrate it at a temperature of 95℃ and a pressure of -0.04MPa to obtain 10L of concentrate with a solid content of 40wt%; take 32L of filtrate from step (4) and concentrate it using a nanofiltration membrane with a molecular weight cutoff of 200Da (concentration pressure of 1.5MPa and temperature of 20℃) to obtain 6.2L of retentate with a solid content of 25wt% and combine it with the concentrate. After spray drying (inlet temperature of 165℃ and outlet temperature of 70℃), the second byproduct is obtained.

[0033] Example 2

[0034] A process for preparing rebaudioside B using stevia mother liquor saccharide includes the following steps:

[0035] (1) Take 20 kg of mother liquor sugar (total glycoside content of 65.6 wt% and rebaudioside B content of 4.2 wt%) obtained during the production of stevia sugar, add it to purified water, stir to dissolve and make up to 80 L, to obtain a 25 wt% mother liquor sugar solution for later use.

[0036] (2) Take 80L of the mother liquor sugar solution mentioned in step (1), adjust the pH to 2.5 with 8wt% nitric acid, and add 120L of extractant (water-saturated ethyl acetate) in a single volume ratio of 1:1.5. After four extractions, collect 478L of extract phase and 82L of raffinate phase.

[0037] (3) Take 478L of the extract phase from step (2), add 319L of the back-extraction agent (0.8wt% KOH solution) at a volume ratio of 1.5:1, and stir. After four back-extractions, collect 1278L of the back-extraction phase and 317L of the back-extraction residue.

[0038] (4) Take 1278L of the back-extraction phase from step (3), add 8wt% hydrochloric acid to adjust the pH to 7.8, and then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 400Da (concentration pressure of 1.8MPa and temperature of 25℃) to obtain a concentrate with a solid content of 6.5wt%. Heat it to 55℃, keep it warm, add 8wt% hydrochloric acid to adjust the pH to 3.2, keep it warm and stir for 1.5h, filter it, and collect 27.4L of filtrate and 1787g of filter cake. The filter cake is dried at 80℃ for 11h to obtain the Lebodi glycoside B product.

[0039] (5) Take 82L of the raffinate from step (2), concentrate it with a nanofiltration membrane with a molecular weight cutoff of 400 Da (concentration pressure is 1.8 MPa and temperature is 25℃), concentrate it to a solid content of 25 wt%, and then spray dry it (inlet temperature is 170℃ and outlet temperature is 75℃) to obtain the first by-product.

[0040] (6) Take the 317L of back-extraction residue from step (3) and heat concentrate it at a temperature of 85℃ and a pressure of -0.06MPa to obtain 7.4L of concentrate with a solid content of 45wt%; take the 27.4L of filtrate from step (4) and concentrate it using a nanofiltration membrane with a molecular weight cutoff of 400Da (concentration pressure of 1.8MPa and temperature of 25℃) to obtain 5.9L of retentate with a solid content of 30wt%. Combine the retentate with the concentrate and spray dry it (inlet temperature of 170℃ and outlet temperature of 75℃) to obtain the second byproduct.

[0041] Example 3

[0042] A process for preparing rebaudioside B using stevia mother liquor saccharide includes the following steps:

[0043] (1) Take 20 kg of mother liquor sugar (total glycoside content of 72.3 wt% and rebaudioside B content of 8.1 wt%) obtained during the production of stevia sugar, add it to purified water, stir to dissolve and make up to 67 L, to obtain a 30 wt% mother liquor sugar solution for later use.

[0044] (2) Take 67L of the mother liquor sugar solution mentioned in step (1), adjust the pH to 3 with 10wt% hydrochloric acid, and add 134L of extractant (water-saturated ethyl acetate) in a single volume ratio of 1:2. After 5 extractions, collect 668L of extract phase and 69L of raffinate phase.

[0045] (3) Take 668L of the extract phase from step (2), add 334L of back-extraction agent (1.5wt% Na2CO3 solution) in a single volume ratio of 2:1, and stir. After 5 back-extractions, collect 1672L of back-extraction phase and 666L of back-extraction residue.

[0046] (4) Take 1672L of the back-extraction phase from step (3), add 10wt% sulfuric acid to adjust the pH to 8, and then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 800Da (concentration pressure is 2.0MPa and temperature is 30℃) to obtain a concentrate with a solid content of 7wt%. Heat it to 60℃, keep it warm, add 10wt% sulfuric acid to adjust the pH to 3.5, keep it warm and stir for 2h, and then filter it. Collect 30.2L of filtrate and 3592g of filter cake respectively. The filter cake is dried at 90℃ for 10h to obtain the Lebodi glycoside B product.

[0047] (5) Take 69L of the raffinate from step (2) and concentrate it with a nanofiltration membrane with a molecular weight cutoff of 800 Da (concentration pressure is 2.0 MPa and temperature is 30℃). The concentrate with a solid content of 28 wt% is spray dried (inlet temperature is 180℃ and outlet temperature is 80℃) to obtain the first by-product.

[0048] (6) Take the 666L of back-extraction residue from step (3) and heat-concentrate it at a temperature of 75℃ and a pressure of -0.08MPa to obtain 3.1L of concentrate with a solid content of 50wt%; take the 30.2L of filtrate from step (4) and concentrate it using a nanofiltration membrane with a molecular weight cutoff of 800Da (concentration pressure of 2.0MPa and temperature of 30℃), collect 7.5L of retentate with a solid content of 28wt% and combine it with the concentrate, and spray dry it (inlet temperature of 180℃ and outlet temperature of 80℃) to obtain the second byproduct.

[0049] Example 4

[0050] A process for preparing rebaudioside B using stevia mother liquor saccharide includes the following steps:

[0051] (1) Take 20 kg of mother liquor sugar (total glycoside content of 68.6 wt% and rebaudioside B content of 6.3 wt%) obtained during the production of stevia sugar, add it to purified water, stir to dissolve and make up to 75 L, to obtain a 35 wt% mother liquor sugar solution for later use.

[0052] (2) Take 57L of the mother liquor sugar solution mentioned in step (1), adjust the pH to 3.2 with 12wt% sulfuric acid, and add 142.5L of extractant (water-saturated ethyl acetate) in a single volume ratio of 1:2.5. After 6 extractions, collect 853L of extract phase and 59L of raffinate phase.

[0053] (3) Take 853L of the extract phase from step (2), add 341L of back-extraction agent (1wt% Na2CO3 solution) at a volume ratio of 2.5:1, and stir. After 6 back-extractions, collect 2048L of back-extraction phase and 851L of back-extraction residue phase respectively.

[0054] (4) Take 2048L of the back-extraction phase from step (3), add 12wt% nitric acid to adjust the pH to 8.2, and then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 800Da (concentration pressure of 2.4MPa and temperature of 35℃) to obtain a concentrate with a solid content of 8wt%. Heat it to 65℃, keep it warm, add 12wt% nitric acid to adjust the pH to 3.8, keep it warm and stir for 2.5h, and then filter it. Collect 24.9L of filtrate and 2785g of filter cake respectively. The filter cake is dried at 100℃ for 9h to obtain the Lebodiin B product.

[0055] (5) Take 59L of the raffinate from step (2) and concentrate it with a nanofiltration membrane with a molecular weight cutoff of 800 Da (concentration pressure is 2.4 MPa and temperature is 35℃). When the solid content is concentrated to 32wt%, spray dry it (inlet temperature is 185℃ and outlet temperature is 90℃) to obtain the first by-product.

[0056] (6) Take the 851L of back-extraction residue from step (3) and concentrate it under the conditions of 70℃ and -0.1MPa to obtain 5.2L of concentrate with a solid content of 50wt%; take the 24.9L of filtrate from step (4) and concentrate it using a nanofiltration membrane with a molecular weight cutoff of 800Da (concentration pressure of 2.4MPa and temperature of 35℃) to obtain 6.3L of retentate with a solid content of 32wt%. Combine the retentate with the concentrate and spray dry it (inlet temperature of 185℃ and outlet temperature of 90℃) to obtain the second byproduct.

[0057] Example 5

[0058] A process for preparing rebaudioside B using stevia mother liquor saccharide includes the following steps:

[0059] (1) Take 20 kg of mother liquor sugar (total glycoside content of 74.5 wt% and rebaudioside B content of 9.2 wt%) obtained during the production of stevia sugar, add it to purified water, stir to dissolve and make up to 50 L, to obtain a 40 wt% mother liquor sugar solution for later use.

[0060] (2) Take 50L of the mother liquor sugar solution in step (1), adjust the pH to 3.5 with 15wt% hydrochloric acid, and add 150L of extractant (water-saturated ethyl acetate) in a single volume ratio of 1:3. Stir and after 6 back-extractions, collect 898L of extract phase and 52L of raffinate phase respectively.

[0061] (3) Take 898L of the extract phase from step (2), add 299L of the back-extraction agent (1wt% NaOH solution) in a single volume ratio of 3:1, and stir. After 6 back-extractions, collect 1798L of the back-extraction phase and 896L of the back-extraction residue.

[0062] (4) Take 1798L of the back-extraction phase from step (3), add 15wt% sulfuric acid to adjust the pH to 8.5, and then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 400Da to obtain a concentrate with a solid content of 10wt%. Heat it to 70℃, keep it warm, add 15wt% sulfuric acid to adjust the pH to 4, keep it warm and stir for 3h, and then filter it. Collect 30.5L of filtrate and 4025g of filter cake respectively. The filter cake is dried at 110℃ for 8h to obtain the Lebodi glycoside B product.

[0063] (5) Take 52L of the raffinate from step (2) and concentrate it with a nanofiltration membrane with a molecular weight cutoff of 400 Da (concentration pressure is 2.5 MPa and temperature is 45℃). The concentrate with a solid content of 45 wt% is spray-dried (inlet temperature is 190℃ and outlet temperature is 95℃) to obtain the first by-product.

[0064] (6) Take 896L of the back-extraction residue from step (3) and heat concentrate it at a temperature of 95℃ and a pressure of -0.1MPa to obtain 1.1L of concentrate with a solid content of 55wt%; take 30.5L of filtrate from step (4) and concentrate it using a nanofiltration membrane with a molecular weight cutoff of 400Da (concentration pressure of 2.5MPa and temperature of 45℃), collect 6.8L of retentate with a solid content of 45wt% and combine it with the concentrate, and spray dry it (inlet temperature of 190℃ and outlet temperature of 95℃) to obtain the second byproduct.

[0065] To better demonstrate that the process of the present invention can improve the yield, purity and purity of rebaudioside B, and also obtain by-products, nine comparative examples are given with reference to Example 3. The rebaudioside B products and by-products obtained in Examples 1-5 and Comparative Examples 1-9 are detailed in Table 1.

[0066] Comparative Example 1

[0067] Unlike Example 3, in step (2), the pH of the mother liquor sugar solution was adjusted to 1.5, while the rest of the operations were the same.

[0068] Comparative Example 2

[0069] Unlike Example 3, in step (2), the pH of the mother liquor sugar solution was adjusted to 4, and the rest of the operations were the same.

[0070] Comparative Example 3

[0071] Unlike Example 3, the extractant in step (2) is n-butanol, while the rest of the operation is the same.

[0072] Comparative Example 4

[0073] Unlike Example 3, the concentration of the back-extraction agent in step (3) is 0.5 wt%, while the rest of the operation is the same.

[0074] Comparative Example 5

[0075] Unlike Example 3, the concentration of the back-extraction agent in step (3) is 2.5 wt%, while the rest of the operation is the same.

[0076] Comparative Example 6

[0077] Unlike Example 3, in step (4), the back-extraction phase is heated to 40°C, while the rest of the operation is the same.

[0078] Comparative Example 7

[0079] Unlike Example 3, in step (4), the back-extraction phase is heated to 80°C, while the rest of the operation is the same.

[0080] Comparative Example 8

[0081] Unlike Example 3, in step (4), the concentrated solution was heated and the pH was adjusted to 2.5, while the rest of the operation was the same.

[0082] Example 9

[0083] Unlike Example 3, in step (4), the concentrated solution was heated and the pH was adjusted to 4.5, while the rest of the operation was the same.

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from the data in Table 1, the process method of the present invention can produce high-yield, high-purity, and high-yield Rebaudin B products. Furthermore, it can be found that the Rebaudin B products obtained in Comparative Examples 1-9 are significantly lower than those in Example 3.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for preparing rebaudioside B using stevia mother liquor saccharide, characterized in that, The process includes the following steps: (1) Take the mother liquor sugar obtained during the stevia production process, add it to purified water and stir to dissolve it. The resulting mother liquor sugar solution is ready for use. (2) Take the mother liquor sugar solution mentioned in step (1), adjust the pH to 2-3.5 with 5-15wt% hydrochloric acid, nitric acid or sulfuric acid, then add the extractant and stir, and collect the extract phase and raffinate phase respectively; the extractant is water-saturated ethyl acetate, and the mother liquor sugar solution and the water-saturated ethyl acetate are mixed in a volume ratio of 1:1-3, and extracted 3-6 times; (3) Take the extract phase from step (2), add the back-extraction agent and stir, and collect the back-extraction phase and the back-extraction residue respectively; the back-extraction agent is 0.5-1wt% NaOH solution, KOH solution, or 1-2wt% Na2CO3 solution, the extract phase and the back-extraction agent are mixed in a volume ratio of 1-3:1, and back-extracted 3-6 times; (4) Take the back-extraction phase described in step (3) and add 5-15 wt% hydrochloric acid, sulfuric acid or nitric acid to adjust the pH to 7.5-8.

5. Then concentrate it with a nanofiltration membrane with a molecular weight cutoff of 200-800 Da to obtain a concentrated solution with a solid content of 5-10 wt%. Heat it to 50-70°C, keep it warm, add 5-15 wt% hydrochloric acid, sulfuric acid or nitric acid to adjust the pH to 3-4, keep it warm and stir for 1-3 hours, and then filter it. Collect the filtrate and filter cake separately. The filter cake is dried to obtain a product with a content of not less than 95 wt% of Lebaudi glycoside B. (5) Take the residual phase from step (2), concentrate and dry it to obtain the first by-product; (6) Take the back-extraction residue from step (3) and concentrate it to obtain the first concentrate; take the filtrate from step (4), concentrate it to obtain the second concentrate, combine it with the first concentrate, and dry it to obtain the second byproduct.

2. The process for preparing rebaudioside B using stevia mother liquor saccharide according to claim 1, characterized in that, The concentration of the mother liquor sugar solution in step (1) is 20-40 wt%, and the total glycoside content of the mother liquor sugar is 60-75 wt%, and the content of rebaudioside B is 3-10 wt%.

3. The process for preparing rebaudioside B using stevia mother liquor saccharide according to claim 1, characterized in that, The filtrate in step (6) is filtered using a nanofiltration membrane with a molecular weight cutoff of 200-800 Da, and the collected filtrate is then concentrated.

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