Method for preparing high-purity rebaudioside B at low cost

Abstract

The invention discloses a low-cost method for preparing high-purity rebaudioside B. The method comprises the following steps: adjusting the pH value of a stevia mother liquor sugar solution to obtain a pretreatment solution; filtering the pretreatment solution, and leaching a filter cake with purified water to obtain a filter cake I and filtrate I; the first filtrate is pumped into a cation resin column and an anion resin column to be treated, and stevioside-containing effluent is obtained; performing vacuum concentration and spray drying on the stevioside-containing effluent to obtain a stevioside mixture; mixing the filter cake I with water to obtain a first suspension, adjusting the pH value, stirring for reaction, filtering, and collecting a filter cake II; mixing the filter cake II and water to obtain a second suspension, adjusting the pH value, heating until the solid is dissolved, cooling for reaction, filtering, and collecting a filter cake III and a filtrate III; and drying the filter cake III to obtain the high-purity rebaudioside B. The method has the advantages that the stevia mother liquor sugar is used as the raw material, the high-purity rebaudioside B is recycled, the preparation cost of the rebaudioside B is reduced, the single-batch treatment capacity is large, the separation effect is good, and the yield of the rebaudioside B is high.

Description

Technical Field

[0001] The invention relates to the technical field of stevioside preparation, and in particular to a method for preparing high-purity rebaudioside B at low cost. Background Art

[0002] Stevioside is a new type of natural sweetener extracted and separated from stevia. It has the characteristics of low calories and high sweetness. Its sweetness is 250 to 300 times that of sucrose. It is non-toxic and has no side effects. It has good development prospects. Stevia contains nutrients such as glycosides, alkaloids, and flavonoids. Steviosides account for the vast majority. Steviosides are composed of a variety of monomer compounds, such as rebaudioside A, rebaudioside D, and rebaudioside B. Among them, rebaudioside A has a higher content, and other types of steviosides have a lower content. As a type of stevioside, rebaudioside B is less sweet than the main product rebaudioside A, but its bitter aftertaste is significantly weaker than the latter. Therefore, the taste of rebaudioside B is significantly better than rebaudioside A. In addition to being a sweetener, studies have found that rebaudioside B also has the effects of regulating blood sugar and blood lipids, relieving constipation, and promoting metabolism. It can be used as an auxiliary treatment for diseases such as diabetes and hyperlipidemia. It is a stevioside compound with great application potential. Therefore, how to prepare high-purity rebaudioside B is of great significance.

[0003] Chinese patent 202210275100.X provides a method for preparing high-purity rebaudioside b by alkaline hydrolysis of rebaudioside a, comprising the following steps: selecting rebaudioside a, adding water to obtain a rebaudioside a aqueous solution, adding alkali to the rebaudioside a aqueous solution to adjust the pH to 9-12, isothermally reacting at a temperature of 60-100°C for 2-24 hours, adding acid to neutralize after the alkaline hydrolysis reaction is completed, adjusting the pH to 6-8, and allowing the neutralized reaction liquid to stand to precipitate a crude rebaudioside b, and subjecting the crude rebaudioside b to solid-liquid separation and drying to obtain rebaudioside b. Although this method can obtain rebaudioside B of a certain purity, the preparation cost of rebaudioside B will increase with rebaudioside A as the raw material. Chinese Patent No. 202110998781.8 provides a process for producing rebaudioside B by high temperature cracking, comprising the following steps: (1) adding 2 to 15 L of purified water per 1 kg of reaction substrate and stirring thoroughly; the reaction substrate comprises any one or more of rebaudioside A, rebaudioside D, rebaudioside J, rebaudioside I, rebaudioside M, rebaudioside N and rebaudioside O; (2) heating the dissolved material to 110 to 180°C for cracking, and maintaining the temperature for at least 1 hour; (3) maintaining the cracking solution in a stirring state, cooling it to 20 to 40°C for crystallization, and filtering; (4) washing the filter cake obtained after filtration with purified water at a temperature of 20 to 80°C, and stopping washing when the pH value of the eluate is 5 to 7, thereby obtaining a crude filter cake; (5) further refining and purifying the crude filter cake to obtain a fine product of rebaudioside B. The above conditions are relatively harsh and energy-intensive. In view of the above problems, it is necessary to provide a low-cost preparation method of rebaudioside B. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a method for preparing high-purity rebaudioside B at low cost is provided. The method uses stevia mother liquor sugar as a raw material, recovers high-purity rebaudioside B, and reduces the preparation cost of rebaudioside B. The method is simple to operate, has a large single batch processing capacity, good separation effect, and a high yield of rebaudioside B.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A method for preparing high-purity rebaudioside B at low cost comprises the following steps:

[0007] S1: dissolving stevia mother liquid sugar in purified water to obtain a stevia mother liquid sugar solution, and adjusting the pH of the stevia mother liquid sugar solution to 10-11 to obtain a pre-treated solution;

[0008] S2: filtering the pretreated solution and washing the filter cake with purified water to obtain a filter cake 1 and a filtrate 1;

[0009] S3: pumping the filtrate into a cationic resin column and an anionic resin column connected in series for desalting and decolorizing to obtain an effluent containing steviol glycosides; the effluent containing steviol glycosides is successively subjected to vacuum concentration and spray drying to obtain a stevioside mixture;

[0010] S4: Mix the filter cake 1 and water to obtain a first suspension, adjust the pH of the first suspension to 2.5-3.5, stir to react, filter, and collect the filter cake 2;

[0011] S5: The filter cake 2 of step S4 is mixed with water to obtain a second suspension, the pH of the second suspension is adjusted to 5.0-6.0, and heated until the solid is dissolved, then cooled to react, and after the reaction is completed, filtered to collect the filter cake 3 and the filtrate 3; the filter cake 3 is washed and dried to obtain high-purity rebaudioside B, and the filtrate 3 is used in the dissolution process of the stevia mother liquor sugar in S1.

[0012] Preferably, in step S1, the concentration of the stevia mother liquor sugar solution is 0.2-0.3 g / ml.

[0013] Preferably, in step S1, when adjusting the pH of the stevia mother liquid sugar solution, the pH regulator used is calcium oxide, calcium hydroxide or a mixture of the two.

[0014] Preferably, in step S1, when adjusting the pH of the stevia mother liquor sugar solution, the temperature is controlled to be 20-50°C.

[0015] Preferably, in step S3, the pumping speed of filtrate 1 is 0.5-2 BV / h.

[0016] Preferably, in step S3, the temperature of vacuum concentration is 60-80°C, the vacuum degree is -0.1 to -0.06Mpa, and the solid content of the concentrate after vacuum concentration is 30-55wt%; and / or the air inlet temperature during spray drying is 160-190°C, and the air outlet temperature is 70-95°C.

[0017] Preferably, in step S4, when preparing the first suspension, the mass ratio of filter cake 1 to water is 1:(5-10).

[0018] Preferably, in step S4, an acid is used to adjust the pH value of the first suspension, and the acid is a mixture of one or more of hydrochloric acid, acetic acid, and citric acid.

[0019] Preferably, in step S4, the stirring reaction temperature is 50-75° C. and the time is 2-6 h.

[0020] Preferably, in step S5, the mass ratio of the filter cake 2 to water is 1:(5-15); and / or sodium hydroxide, potassium hydroxide or a mixture of both is used to adjust the pH value of the second suspension.

[0021] Preferably, in step S5, the temperature for heating until the solid is dissolved is 90-100°C, the temperature for cooling reaction is 35-45°C, and the time is 0.5-2h.

[0022] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. The present invention firstly effectively controls the solid content and pH of the stevia mother liquid sugar solution, and then performs preliminary separation of rebaudioside B and other types of steviol glycosides in the stevia mother liquid sugar by filtration. After separation, the other types of steviosides are desalted and decolorized by cationic resin and anionic resin to obtain a stevioside mixture with a high total glycoside content, thereby improving the economic value of the stevia mother liquid sugar.

[0024] 2. The present invention uses water as a purification reagent to purify the filter cake containing rebaudioside B in stages after preliminary separation, and effectively adjusts the pH value, temperature and other conditions of the purification treatment in each stage, so that rebaudioside B is effectively separated and treated, and a high content of rebaudioside B is obtained, thereby achieving efficient extraction of rebaudioside B.

[0025] 3. The method provided by the present invention has simple process steps, low energy consumption, strong operability, and is suitable for large-scale industrial production. Moreover, the product of the present invention has high purity and stable yield, and can meet the market demand for high-quality stevioside and rebaudioside B. DETAILED DESCRIPTION

[0026] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0028] In the following examples and comparative examples, unless otherwise specified, the raw materials are all commercially available and the conditions are all conventional conditions in the art.

[0029] Example 1

[0030] A method for preparing high-purity rebaudioside B at low cost comprises the following steps:

[0031] (1) dissolving 2.0 kg of stevia mother liquor sugar (total glycoside content 60.7 wt %, rebaudioside B content 6.3 wt %) in 10 L of purified water to obtain a stevia mother liquor sugar solution; adding calcium oxide to the stevia mother liquor sugar solution at 20° C. to adjust the pH to 10 to obtain a pretreated solution;

[0032] (2) filtering the pretreated liquid, washing the filter cake with purified water, and collecting the filter cake 1 and the filtrate 1;

[0033] (3) The filtrate was pumped into a cationic resin column and an anionic resin column connected in series at a flow rate of 0.5 BV / h for desalting and decolorization. The effluent was concentrated to a solid content of 30 wt % at 61° C. and a vacuum degree of -0.01 MPa, and then spray-dried (inlet temperature 190° C., outlet temperature 95° C.) to obtain 1217 g of a high-content steviol glycoside mixture with a total glycoside content of 85.6 wt %;

[0034] (4) Filter cake 1 and water were mixed and slurried in a mass ratio of 1:10 to obtain a first suspension, and the pH of the first suspension was adjusted to 2.5 with hydrochloric acid. The mixture was stirred and reacted at 75° C. for 2 h, and then filtered to obtain filter cake 2;

[0035] (5) Filter cake 2 and water are mixed and slurried in a mass ratio of 1:5 to obtain a second suspension, sodium hydroxide is added to the second suspension to adjust the pH of the second suspension to 6.0, and the mixture is heated to 100° C. to dissolve the solid, then cooled to 35° C., reacted for 0.5 h, filtered, and the filter cake is washed to obtain filter cake 3 and filtrate 3, and filter cake 3 is dried to obtain 116.7 g of high-content rebaudioside B, with a rebaudioside B content of 96.0 wt% and a yield of 88.9%; filtrate 3 is used for the dissolution process of stevia mother liquor sugar in step (1).

[0036] Example 2

[0037] A method for preparing high-purity rebaudioside B at low cost comprises the following steps:

[0038] (1) dissolving 3.0 kg of stevia mother liquor sugar (total glycoside content 74.5 wt %, rebaudioside B content 12.4 wt %) in 10 L of purified water to obtain a stevia mother liquor sugar solution; adding calcium hydroxide to the stevia mother liquor sugar solution at 50° C. to adjust the pH to 11 to obtain a pretreated solution;

[0039] (2) filtering the pretreated liquid, washing the filter cake with purified water, and collecting the filter cake 1 and the filtrate 1;

[0040] (3) The filtrate was pumped into a cationic resin column and an anionic resin column connected in series at a flow rate of 2 BV / h for desalting and decolorization. The effluent was concentrated to a solid content of 55 wt % at 80° C. and a vacuum degree of -0.06 MPa, and then spray-dried (inlet temperature 160° C., outlet temperature 75° C.) to obtain 2055 g of a high-content steviol glycoside mixture with a total glycoside content of 86.1 wt %;

[0041] (4) Filter cake 1 and water were mixed and slurried in a mass ratio of 1:5 to obtain a first suspension, and the pH of the first suspension was adjusted to 3.5 with citric acid. The mixture was stirred and reacted at 50° C. for 6 h, and then filtered to obtain filter cake 2;

[0042] (5) Filter cake 2 and water are mixed and slurried in a mass ratio of 1:15 to obtain a second suspension, potassium hydroxide is added to the second suspension to adjust the pH of the second suspension to 5.0, and the mixture is heated to 90°C to dissolve the solid, then cooled to 45°C, reacted for 2.0 hours, filtered, and the filter cake is washed to obtain filter cake 3 and filtrate 3, and filter cake 3 is dried to obtain 347.6 g of high-content rebaudioside B, with a rebaudioside B content of 95.5 wt% and a yield of 89.2%; filtrate 3 is used for the dissolution process of stevia mother liquor sugar in step (1).

[0043] Example 3

[0044] A method for preparing high-purity rebaudioside B at low cost comprises the following steps:

[0045] (1) dissolving 2.3 kg of stevia mother liquor sugar (total glycoside content 66.5 wt %, rebaudioside B content 3.9 wt %) in 10 L of purified water to obtain a stevia mother liquor sugar solution; adding calcium oxide to the stevia mother liquor sugar solution at 35° C. to adjust the pH to 10.3 to obtain a pretreated solution;

[0046] (2) filtering the pretreated liquid, washing the filter cake with purified water, and collecting the filter cake 1 and the filtrate 1;

[0047] (3) The filtrate was pumped into a cationic resin column and an anionic resin column connected in series at a flow rate of 1.0 BV / h for desalting and decolorization. The effluent was concentrated to a solid content of 40 wt % at 75° C. and a vacuum degree of -0.07 MPa, and then spray-dried (inlet temperature 175° C., outlet temperature 70° C.) to obtain 1618 g of a high-content steviol glycoside mixture with a total glycoside content of 85.7 wt %;

[0048] (4) Filter cake 1 and water were mixed and slurried in a mass ratio of 1:7 to obtain a first suspension, and the pH of the first suspension was adjusted to 2.8 with acetic acid. The mixture was stirred and reacted at 61° C. for 3 h, and then filtered to obtain filter cake 2;

[0049] (5) Filter cake 2 and water are mixed and slurried in a mass ratio of 1:12 to obtain a second suspension, potassium hydroxide is added to the second suspension to adjust the pH of the second suspension to 5.3, and the mixture is heated to 93°C to dissolve the solid, then cooled to 37°C, reacted for 1.0h, filtered, and the filter cake is washed to obtain filter cake 3 and filtrate 3, and filter cake 3 is dried to obtain 83.4g of high-content rebaudioside B, with a rebaudioside B content of 95.3wt% and a yield of 88.6%; filtrate 3 is used in the dissolution process of stevia mother liquor sugar in step (1).

[0050] Example 4

[0051] A method for preparing high-purity rebaudioside B at low cost comprises the following steps:

[0052] (1) dissolving 2.7 kg of stevia mother liquor sugar (total glycoside content 71.0 wt %, rebaudioside B content 14.3 wt %) in 10 L of purified water to obtain a stevia mother liquor sugar solution; adding calcium hydroxide to the stevia mother liquor sugar solution at 45° C. to adjust the pH to 10.7 to obtain a pretreated solution;

[0053] (2) filtering the pretreated liquid, washing the filter cake with purified water, and collecting the filter cake 1 and the filtrate 1;

[0054] (3) The filtrate was pumped into a cationic resin column and an anionic resin column connected in series at a flow rate of 1.0 BV / h for desalting and decolorization. The effluent was concentrated to a solid content of 50 wt % at 65° C. and a vacuum degree of -0.09 MPa, and then spray-dried (inlet temperature 185° C., outlet temperature 85° C.) to obtain 1710 g of a high-content steviol glycoside mixture with a total glycoside content of 86.9 wt %;

[0055] (4) Filter cake 1 and water were mixed and slurried in a mass ratio of 1:8 to obtain a first suspension, and the pH of the first suspension was adjusted to 3.0 with hydrochloric acid. The mixture was stirred and reacted at 72° C. for 5 h, and then filtered to obtain filter cake 2;

[0056] (5) Filter cake 2 and water are mixed and slurried in a mass ratio of 1:10 to obtain a second suspension, sodium hydroxide is added to the second suspension to adjust the pH of the second suspension to 5.7, the suspension is heated to 97°C to dissolve the solid, and then the temperature is reduced to 42°C. After reacting for 1.0 h, the mixture is filtered and the filter cake is washed to obtain filter cake 3 and filtrate 3. The filter cake 3 is dried to obtain 361.7 g of high-content rebaudioside B, with a rebaudioside B content of 96.1 wt% and a yield of 90.0%; the filtrate 3 is used for the dissolution process of stevia mother liquor sugar in step (1).

[0057] Comparative Example 1

[0058] Compared with Example 4, the difference is that: 2.7 kg of stevia mother liquor sugar is dissolved at a concentration of 0.4 g / ml, and other conditions are the same as Example 4, to obtain 1698 g of a high-content stevioside mixture with a total glycoside content of 84.1 wt%; 331.2 g of high-content rebaudioside B, with a rebaudioside B content of 92.3 wt% and a yield of 79.2%.

[0059] Comparative Example 2

[0060] Compared with Example 4, the difference is that in step (1), the preparation temperature of the pretreatment liquid is 10°C, and the other conditions are the same as those in Example 4, and 1712g of a high-content stevioside mixture is obtained, with a total glycoside content of 83.9wt%; 327.0g of a high-content rebaudioside B, with a rebaudioside B content of 93.2wt% and a yield of 78.9%.

[0061] Comparative Example 3

[0062] Compared with Example 4, the difference is that in step (1), the preparation temperature of the pretreatment liquid is 60°C, and the other conditions are the same as those in Example 4, and 1771g of a high-content stevioside mixture is obtained, with a total glycoside content of 82.4wt%; 301.4g of high-content rebaudioside B, with a rebaudioside B content of 95.3wt% and a yield of 74.4%.

[0063] Comparative Example 4

[0064] Compared with Example 4, the difference is that in step (1), the pH of the pretreatment liquid is 9, and the other conditions are the same as those in Example 4, and 1904 g of a high-content stevioside mixture is obtained, with a total glycoside content of 79.2 wt%; 218.0 g of a high-content rebaudioside B, with a rebaudioside B content of 95.7 wt% and a yield of 54.0%.

[0065] Comparative Example 5

[0066] Compared with Example 4, the difference is that in step (1), the pH of the pretreatment liquid is 12, and the other conditions are the same as those in Example 4, and 1652 g of a high-content stevioside mixture is obtained, with a total glycoside content of 85.2 wt%; 363.5 g of a high-content rebaudioside B, with a rebaudioside B content of 89.5 wt% and a yield of 84.3%.

[0067] Comparative Example 6

[0068] Compared with Example 4, the difference is that in step (4), the pH of the first suspension is 2.0, and the other conditions are the same as those in Example 4, and 1706 g of a high-content stevioside mixture is obtained, with a total glycoside content of 85.9 wt%; 306.6 g of a high-content rebaudioside B, with a rebaudioside B content of 92.4 wt% and a yield of 73.4%.

[0069] Comparative Example 7

[0070] Compared with Example 4, the difference is that in step (4), the pH of the first suspension is 4.5, and the other conditions are the same as those in Example 4, and 1708g of a high-content stevioside mixture is obtained, with a total glycoside content of 86.0wt%; 459.0g of a high-content rebaudioside B, with a rebaudioside B content of 75.4wt% and a yield of 89.6%.

[0071] Comparative Example 8

[0072] Compared with Example 4, the difference is that in step (4), the stirring reaction temperature is 40°C, and the other conditions are the same as those in Example 4, and 1704g of a high-content stevioside mixture is obtained, with a total glycoside content of 85.9wt%; 381.4g of a high-content rebaudioside B, with a rebaudioside B content of 90.1wt% and a yield of 89.0%.

[0073] Comparative Example 9

[0074] Compared with Example 4, the difference is that in step (4), the stirring reaction temperature is 80°C, and the other conditions are the same as those in Example 4, and 1710g of a high-content stevioside mixture is obtained, with a total glycoside content of 86.5wt%; 321.0g of a high-content rebaudioside B, with a rebaudioside B content of 95.5wt% and a yield of 79.4%.

[0075] Comparative Example 10

[0076] Compared with Example 4, the difference is that in step (5), the pH of the second suspension is 4.0, and the other conditions are the same as those in Example 4, and 1711 g of a high-content stevioside mixture is obtained, with a total glycoside content of 86.3 wt%; 431.7 g of high-content rebaudioside B, with a rebaudioside B content of 81.5 wt% and a yield of 91.1%.

[0077] Comparative Example 11

[0078] Compared with Example 4, the difference is that in step (5), the pH of the second suspension is 7.0, and the other conditions are the same as those in Example 4, and 1708 g of a high-content stevioside mixture is obtained, with a total glycoside content of 86.4 wt%; 187.0 g of a high-content rebaudioside B, with a rebaudioside B content of 96.0 wt% and a yield of 46.5%.

[0079] Comparative Example 12

[0080] Compared with Example 4, the difference is that in step (5), the temperature is lowered to 25°C, and the other conditions are the same as those in Example 4, to obtain 1710g of a high-content stevioside mixture with a total glycoside content of 86.0wt%; 376.2g of a high-content rebaudioside B with a rebaudioside B content of 93.4wt% and a yield of 91.0%.

[0081] Comparative Example 13

[0082] Compared with Example 4, the difference is that in step (5), the temperature is lowered to 55°C, and the other conditions are the same as those in Example 4, to obtain 1704g of a high-content stevioside mixture with a total glycoside content of 86.5wt%; 321.5g of a high-content rebaudioside B with a rebaudioside B content of 95.9wt% and a yield of 79.9%.

[0083] In summary, compared with the comparative example, the present invention uses stevia mother liquor sugar as raw material, and through effective optimization of various process conditions, rebaudioside B is separated from other steviol glycosides, thereby obtaining a stevia glycoside mixture with a high total glycoside content and a high content of rebaudioside B, thereby improving the utilization rate of stevia mother liquor sugar.

[0084] The solid content of the stevia mother liquor sugar solution has a certain influence on the separation effect. In Comparative Example 1, the solid content of the stevia mother liquor sugar solution is too high, and the yield of the stevioside mixture and the yield of rebaudioside B are significantly reduced. This is because under the condition of high solid content, the remaining steviosides and impurities are enriched in the filter cake 1, which not only affects the purity of rebaudioside B, but also reduces the yield of the stevioside mixture in the filtrate 1. Since the content of rebaudioside B in the filter cake 1 is low, the separation effect in the refining process is affected, and then the content and yield of the rebaudioside B product are affected.

[0085] When achieving the preliminary separation of rebaudioside B from other steviosides, the pH and temperature of the feed solution and their key, comparative examples 2 to 5, the feed solution temperature is too low, and the impurities and rebaudioside B are precipitated together in the filter cake 1 for enrichment, thereby reducing the content of rebaudioside B in the filter cake 1. When the filter cake 1 is mixed with water for pulping to prepare the first suspension, rebaudioside B can be better dissolved, resulting in a low content of rebaudioside B in the filter cake 2. The presence of impurities will take away more rebaudioside B, thereby reducing the yield. When the feed solution temperature is too high, rebaudioside B cannot be fully precipitated, thereby reducing the yield of rebaudioside B. When the pH of the feed solution is too low during precipitation, rebaudioside B cannot be fully complexed and precipitated with calcium ions, and the yield is reduced. If the pH is too high, other steviosides except rebaudioside B will be destroyed under high pH conditions, and then complexed and precipitated with calcium ions, thereby affecting the purity of rebaudioside B.

[0086] When preliminarily separating and purifying rebaudioside B, it is necessary to reasonably adjust the pH and temperature during purification to promote the dissolution of calcium salt. In Comparative Example 6, the pH is too low, and impurities will precipitate out together with rebaudioside B, thereby reducing the content of rebaudioside B in filter cake 2, and then reducing the purification effect during subsequent further refining and purification, so that the purity and yield of rebaudioside B are affected; in Comparative Example 7, the pH is too high, rebaudioside B cannot be fully precipitated, and the yield is low; in Comparative Example 8, the purification temperature is too low, and impurities will precipitate together with rebaudioside B, thereby affecting the purity of rebaudioside B, and in Comparative Example 9, the purification temperature is too high, and rebaudioside B cannot be fully precipitated, thereby reducing the yield of rebaudioside B.

[0087] When the crude rebaudioside B is purified again, the purification conditions are also extremely critical. In Comparative Examples 10 and 12, the pH is too low or the precipitation temperature is too low, and the flavonoid impurities will be precipitated together, thereby reducing the purity of rebaudioside B. In Comparative Examples 11 and 13, the pH is too high or the precipitation temperature is too high, and rebaudioside B cannot be fully precipitated, thereby reducing the yield of rebaudioside B.

[0088] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing high-purity rebaudioside B at low cost, characterized in that: The following steps are involved: S1: dissolving stevia mother liquid sugar in purified water to obtain a stevia mother liquid sugar solution, and adjusting the pH of the stevia mother liquid sugar solution to 10-11 to obtain a pre-treated solution; S2: filtering the pretreated solution and washing the filter cake with purified water to obtain a filter cake 1 and a filtrate 1; S3: pumping the filtrate into a cationic resin column and an anionic resin column connected in series for desalting and decolorizing to obtain an effluent containing steviol glycosides; the effluent containing steviol glycosides is successively subjected to vacuum concentration and spray drying to obtain a stevioside mixture; S4: Mix the filter cake 1 and water to obtain a first suspension, adjust the pH of the first suspension to 2.5-3.5, stir to react, filter, and collect the filter cake 2; S5: The filter cake 2 of step S4 is mixed with water to obtain a second suspension, the pH of the second suspension is adjusted to 5.0-6.0, and heated until the solid is dissolved, then cooled to react, and after the reaction is completed, filtered to collect the filter cake 3 and the filtrate 3; the filter cake 3 is washed and dried to obtain high-purity rebaudioside B, and the filtrate 3 is used in the dissolution process of the stevia mother liquor sugar in S1.

2. A method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S1, the concentration of the stevia mother liquor sugar solution is 0.2-0.3 g / ml.

3. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S1, when adjusting the pH of the stevia mother liquid sugar solution, the pH adjusting agent used is one of calcium oxide and calcium hydroxide or a mixture of the two; and / or when adjusting the pH of the stevia mother liquid sugar solution, the temperature is controlled to be 20-50°C.

4. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S3, the pumping speed of filtrate 1 is 0.5-2 BV / h.

5. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S3, the vacuum concentration temperature is 60-80°C, the vacuum degree is -0.1 to -0.06Mpa, and the solid content of the concentrate after vacuum concentration is 30-55wt%; and / or the air inlet temperature during spray drying is 160-190°C, and the air outlet temperature is 70-95°C.

6. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S4, when preparing the first suspension, the mass ratio of filter cake 1 to water is 1:(5-10).

7. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S4, the pH value of the first suspension is adjusted by using an acid, wherein the acid is a mixture of one or more of hydrochloric acid, acetic acid, and citric acid.

8. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S4, the stirring reaction temperature is 50-75° C. and the time is 2-6 h.

9. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S5, the mass ratio of the filter cake 2 to water is 1:(5-15); and / or sodium hydroxide, potassium hydroxide or a mixture of both is used to adjust the pH value of the second suspension.

10. The method for preparing high-purity rebaudioside B at low cost according to claim 1, characterized in that: In step S5, the temperature when the solid is heated to dissolve is 90-100°C, and the temperature of the cooling reaction is 35-45°C for 0.5-2h.