A method of separating steviol glycosides and chlorogenic acids

Abstract

The application discloses a method for separating steviol glycosides and chlorogenic acid, comprising the following steps: concentrating a stevia extract by using a nanofiltration membrane to obtain a concentrated solution; adsorbing the concentrated solution by using a resin system composed of a series connection of LX-8 and LX-T28 resin columns; after the adsorption is completed, resolving the LX-8 resin column by using 60-80wt% ethanol solution alone to obtain a chlorogenic acid resolution solution, and resolving the LX-28 resin column by using 60-80wt% ethanol solution to obtain a steviol glycoside resolution solution; and after the chlorogenic acid resolution solution is concentrated, spray drying is performed to obtain chlorogenic acid; and after the steviol glycoside resolution solution is concentrated, spray drying is performed to obtain steviol glycosides. The method uses a series connection of resin systems to treat the concentrated stevia extract, and uses different adsorption resins to adsorb and separate steviol glycosides and chlorogenic acid in the stevia extract, and the method is simple and has high separation efficiency.

Description

Technical Field

[0001] This invention relates to the field of stevia technology, and more specifically to a method for separating stevia and chlorogenic acid. Background Technology

[0002] The main component of dried stevia leaves is steviol glycosides, which are not only high in sweetness and low in calories, but also possess certain pharmacological effects. Stevia glycosides are mainly used to treat diabetes, control blood sugar, lower blood pressure, fight tumors, combat diarrhea, enhance immunity, and promote metabolism. They are also effective in controlling obesity, regulating stomach acid, and relieving nerve fatigue. Furthermore, they have significant therapeutic effects on heart disease and childhood tooth decay. Most importantly, they can eliminate the side effects of sucrose. In addition, the extract obtained from stevia also contains a certain amount of chlorogenic acid. Chlorogenic acid has antioxidant, anti-inflammatory, antibacterial, and antiviral effects, as well as anti-hyperglycemic and anti-hyperlipidemia properties. Therefore, the simultaneous extraction and separation of steviol glycosides and chlorogenic acid from stevia is of great significance.

[0003] Chinese Patent 201811159815.9 discloses an industrial method for the simultaneous preparation of stevia chlorogenic acid and steviol glycosides. Using stevia as a raw material, after alcohol extraction, the state of the liquid is adjusted to allow chlorogenic acid to exist in a free molecular state. The mixture is then extracted and separated using a water-immiscible, moderately polar organic solvent. The organic layer is enriched with stevia chlorogenic acid, and the aqueous layer is enriched with steviol glycosides. This method has the following drawbacks: low production efficiency, low product yield, high production cost, and the use of a large amount of extraction solvent.

[0004] Chinese Patent 201210421968.2 discloses a method for stepwise preparation of stevia and chlorogenic acid from stevia leaves. Specifically, ferrous salts are added to stevia extract for flocculation and precipitation to precipitate chlorogenic acid. The filtrate is then adsorbed, desorbed, and purified using macroporous adsorption resin to obtain stevia. The filter cake is dissolved in water, adsorbed, desorbed, concentrated, dried, and recrystallized using macroporous adsorption resin to obtain chlorogenic acid. The above method has the following drawbacks: the process is complex, and the separation effect still needs further improvement. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for separating stevia and chlorogenic acid, which addresses the shortcomings of the existing technology. The present invention uses stevia extract as raw material and employs a series of resin systems to process the concentrated stevia extract. Different adsorption resins are used to adsorb and separate stevia and chlorogenic acid from the stevia extract. The above method is simple and has high separation efficiency.

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

[0007] A method for separating stevia and chlorogenic acid includes the following steps:

[0008] (1) The stevia extract was concentrated using a nanofiltration membrane to obtain a concentrate;

[0009] (2) The above concentrate was adsorbed through a resin system consisting of LX-8 and LX-T28 resin columns connected in series. After the adsorption was completed, the LX-8 resin column was eluted separately with 60-80wt% ethanol solution to obtain chlorogenic acid eluent. The LX-28 resin column was eluted with 60-80wt% ethanol solution to obtain stevia eluent.

[0010] (3) The chlorogenic acid solution was concentrated and then spray-dried to obtain chlorogenic acid; the above stevia solution was concentrated and then spray-dried to obtain stevia.

[0011] Preferably, the stevia extract is prepared by using a 10-60 wt% ethanol solution as the extraction solvent to perform countercurrent extraction on stevia powder, wherein the mass ratio of ethanol solution to stevia powder is 10-20:1.

[0012] Preferably, in step (1), the nanofiltration membrane has a molecular weight cutoff of 1000-2000 Da and is concentrated to 1 / 3-1 / 5 of the stevia extract.

[0013] The solid content of the solution affects the subsequent resin separation effect. Too high a solid content will result in insufficient separation, while too low a solid content will lead to an excessive sample volume, affecting adsorption efficiency. Therefore, the stevia extract is concentrated to a suitable solid content using nanofiltration membrane.

[0014] Preferably, in step (2), the ratio of LX-8 to LX-T28 resin columns in the resin system is 1:4. When preparing the stevia solution, the first two LX-T28 resin columns in series are analyzed using a 60-80wt% ethanol solution. In the next round of feeding, LX-8 is used as the first column of the resin system, and the third and fourth LX-T28 columns from the previous round are used as the first and second LX-T28 columns in this round, and so on, in a continuous cycle.

[0015] Based on the content of chlorogenic acid and stevia in the stevia extract and the adsorption capacity of the resin, the resin system includes LX-8 resin columns connected in series and four LX-T28 resin columns. During separation, when sucrose is emitted from the tail column of LX-T28, the LX-8 resin is near saturation, and the first two LX-T28 columns are saturated. At this point, the LX-8 resin is eluted separately with ethanol solution to obtain chlorogenic acid eluate, and the first two LX-T28 columns are eluted with ethanol solution to obtain stevia eluate. After the elution is completed, in the next feeding cycle, LX-8 is still used as the first column of the resin system, the third LX-T28 column of the previous cycle becomes the first LX-T28 column of this cycle, the fourth LX-T28 column of the previous cycle becomes the second LX-T28 column of this cycle, and so on, repeating the cycle. Chlorogenic acid and stevia can be adsorbed separately with a single feeding.

[0016] Preferably, in step (2), when preparing the chlorogenic acid eluent, the volume of the ethanol solution is 1.5-2 BV of the resin column volume, and when preparing the stevia eluent, the volume of the ethanol solution is 1.5-2 BV of the resin volume.

[0017] Preferably, in step (2), the flow rate during sample loading and adsorption and during desorption is 1-1.5 BV / h.

[0018] Preferably, in step (2), the stevia extract is purified before concentration. The purification process includes adding an adsorbent to the stevia extract for adsorption treatment, followed by filtration, eluting the precipitate with hydrochloric acid solution, and collecting the eluent.

[0019] Preferably, the adsorbent is prepared by adding SDS to a mixed solution of p-toluenesulfonic acid, 2,6-diaminoanthraquinone and tetrahydrofuran, stirring and mixing, then adding water, stirring at room temperature, then adding a tetrahydrofuran solution of 1,3,5-tricarboxymethylphloroglucinol, continuing to stir and react, drying after the reaction is completed, centrifuging the reaction solution, washing the centrifuged precipitate and drying it to obtain SDS-modified COFs framework material.

[0020] Preferably, the mass ratio of SDS, p-toluenesulfonic acid, 2,6-diaminoanthraquinone, and 1,3,5-tricarboxymethylphloroglucinol is (0.05-0.1):(0.1-0.15):(0.8-0.9):0.6.

[0021] Preferably, the stirring time at room temperature is 20-30 min, the stirring speed is 400-500 r / min, and the stirring reaction time is 7-8 h.

[0022] Preferably, the amount of SDS-modified COFs framework material added is 0.02-0.05% of the mass of stevia extract, the stirring speed of the adsorption treatment is 400-500 r / min, and the time is 5-6 h.

[0023] Preferably, the concentration of the hydrochloric acid solution is 4-5 wt%, and the mass ratio of the hydrochloric acid solution to the precipitate during elution is (5-10):1.

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. This invention provides a method for separating stevia and chlorogenic acid. The method uses LX-8 and LX-T28 resins as adsorption resins. By utilizing the interaction between the resins and chlorogenic acid and stevia, chlorogenic acid and stevia are adsorbed and separated respectively. The process route is simple, does not require multiple extractions, is safe and convenient, and has high efficiency.

[0026] 2. The resin system used in this invention consists of LX-8 and LX-T28 resin columns connected in series. The ratio of LX-8 to LX-T28 resin columns is controlled to 1:4 based on the content of chlorogenic acid and stevia in the stevia extract. During adsorption, when the LX-T28 column produces sucrose, the LX-8 resin column and part of the LX-T28 resin column are saturated. Then, a certain concentration of ethanol solution is used to separately precipitate the LX-8 resin column and part of the LX-T28 resin column. During the next adsorption, the feed of multiple LX-T28 resin columns is adjusted by switching valves, thereby achieving continuous adsorption treatment with high efficiency and high product yield.

[0027] 3. The present invention further purifies the stevia eluent after resin analysis. During purification, SDS-modified COFs framework material is used, which can effectively adsorb stevia in the eluent through hydrogen bonding. Then, a certain amount of hydrochloric acid solution is used for elution, which further improves the purity of stevia. Attached image description:

[0028] Figure 1 This is a schematic diagram of the resin system.

[0029] In the figure, 1 is an LX-8 resin column; 2 is the first LX-T28 resin column; 3 is the second LX-T28 resin column; 4 is the third LX-T28 resin column; and 5 is the fourth LX-T28 resin column. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] In the following examples and comparative examples, the preparation method of stevia extract is as follows: 1 kg of stevia plant leaves were crushed and mixed with a 20 wt% solution at a mass ratio of 1:20. The mixture was then extracted countercurrently at 40°C for 2 h to obtain stevia extract. The extract contained 2.1 wt% chlorogenic acid and 27.3 wt% steviol glycosides.

[0033] like Figure 1 As shown, the resin system in the following embodiments and comparative examples includes LX-8 resin column 1, first LX-T28 resin column 2, second LX-T28 resin column 3, third LX-T28 resin column 4, and fourth LX-T28 resin column 5 connected in series.

[0034] In the following examples and comparative examples, the product yield was calculated using the following methods:

[0035] Chlorogenic acid (%) = [(Chlorogenic acid product yield × Chlorogenic acid content in chlorogenic acid product) / (Stemisia extract mass × Chlorogenic acid content in stevia extract)] × 100%;

[0036] Steviosides (%) = [(stevioside product yield × total glycoside content in stevioside product) / (stevia extract mass × stevioside content in stevia extract)] × 100%.

[0037] Example 1

[0038] A method for separating stevia and chlorogenic acid includes the following steps:

[0039] (1) Concentrate 1L of stevia extract to 1 / 5 of the original solution volume using a nanofiltration membrane with a molecular weight cutoff of 1000 Da to obtain a concentrated solution;

[0040] (2) The above concentrate is pumped into the resin system at a flow rate of 1 BV / h for adsorption treatment. The process is stopped when sweetness is observed at the tail column. Then, the LX-8 resin column is desorbed separately using a 60 wt% ethanol solution at a flow rate of 1 BV / h, with the volume of the ethanol solution controlled to be 1.5 BV of the LX-8 resin column volume, to obtain chlorogenic acid desorbate. The first LX-T28 resin column and the second LX-T28 resin column connected in series are desorbed using a 60 wt% ethanol solution at a flow rate of 1 BV / h to obtain stevia desorbate. In the next round of adsorption separation, the LX-8 resin column, the third LX-T28 resin column, the fourth LX-T28 resin column, the first LX-T28 resin column, and the second LX-T28 resin column are connected in series in sequence by switching valves, and this cycle is repeated.

[0041] (3) After concentrating the chlorogenic acid eluent, spray drying was performed to obtain 46.5g of chlorogenic acid product with a total chlorogenic acid content of 40.9wt% and a chlorogenic acid yield of 90.5%. After concentrating the above stevia eluent, spray drying was performed to obtain 274.7g of stevia product with a total glycoside content of 98.3wt% and a yield of 98.9%.

[0042] Example 2

[0043] A method for separating stevia and chlorogenic acid includes the following steps:

[0044] (1) Concentrate 1L of stevia extract to 1 / 5 of the original solution volume using a nanofiltration membrane with a molecular weight cutoff of 2000 Da to obtain a concentrated solution.

[0045] (2) The above concentrated solution is pumped into the resin system at a flow rate of 1.5 BV / h for adsorption treatment. The process is stopped when sweetness is observed at the tail column. Then, the LX-8 resin column is desorbed separately using a 60 wt% ethanol solution at a flow rate of 1.5 BV / h, with the volume of the ethanol solution controlled to be 2 BV of the LX-8 resin column volume, to obtain chlorogenic acid desorbate. The first LX-T28 resin column and the second LX-T28 resin column connected in series are desorbed using a 60 wt% ethanol solution at a flow rate of 1.5 BV / h to obtain stevia desorbate. In the next round of adsorption separation, the LX-8 resin column, the third LX-T28 resin column, the fourth LX-T28 resin column, the first LX-T28 resin column, and the second LX-T28 resin column are connected in series in sequence by switching valves, and this cycle is repeated.

[0046] (3) After concentrating the chlorogenic acid eluent, spray drying was performed to obtain 46.7g of chlorogenic acid, with a total chlorogenic acid content of 40.5wt% and a yield of 90.1%.

[0047] (4) Add 0.05g SDS to a mixed solution of 0.11g p-toluenesulfonic acid, 0.8g 2,6-diaminoanthraquinone and 2ml tetrahydrofuran. After stirring and mixing, add 4.5ml water. Stir at room temperature for 30min at 500r / min. Then add a tetrahydrofuran solution containing 0.6g 1,3,5-tricarboxymethyl phloroglucinol. Continue stirring and react for 7h. After the reaction is complete, dry the solution. Centrifuge the reaction solution. Wash the precipitate after centrifugation and dry it to obtain SDS-modified COFs framework material.

[0048] (5) Add SDS-modified COFs framework material (0.03% of the mass of stevia extract) to the above stevia extract solution, stir and adsorb at 400 r / min for 5 h, then filter, and elute the precipitate with 5 wt% hydrochloric acid solution (mass ratio of hydrochloric acid solution to precipitate is 5:1). Collect the eluent, concentrate the eluent and spray dry it to obtain 273.6 g of stevia, with a total glycoside content of 99.0 wt% and a yield of 99.2%.

[0049] Example 3

[0050] A method for separating stevia and chlorogenic acid includes the following steps:

[0051] (1) Concentrate 1L of stevia extract to 1 / 5 of the original solution volume using a nanofiltration membrane with a molecular weight cutoff of 2000 Da to obtain a concentrated solution.

[0052] (2) The above concentrated solution was pumped into the resin system at a flow rate of 1.2 BV / h for adsorption treatment. The process was stopped when sweetness was observed at the tail column. Then, the LX-8 resin column was desorbed separately using a 60 wt% ethanol solution at a flow rate of 1.2 BV / h, with the volume of the ethanol solution controlled to be 1.5 BV of the LX-8 resin column volume, to obtain the chlorogenic acid desorbent. The first LX-T28 resin column and the second LX-T28 resin column connected in series were desorbed using a 60 wt% ethanol solution at a flow rate of 1.5 BV / h to obtain the stevia desorbent. In the next round of adsorption separation, the LX-8 resin column, the third LX-T28 resin column, the fourth LX-T28 resin column, the first LX-T28 resin column, and the second LX-T28 resin column were connected in series in sequence by switching valves, and this cycle was repeated.

[0053] (3) The chlorogenic acid eluent was concentrated and then spray-dried to obtain 46.7g of chlorogenic acid with a chlorogenic acid content of 40.5wt% and a yield of 90.1%.

[0054] (4) Add 0.07g SDS to a mixed solution of 0.1g p-toluenesulfonic acid, 0.8g 2,6-diaminoanthraquinone and 2ml tetrahydrofuran. After stirring and mixing, add 4.5ml water. Stir at room temperature for 20min at 400-500r / min. Then add a tetrahydrofuran solution containing 0.6g 1,3,5-tricarboxymethyl phloroglucinol. Continue stirring and react for 7h. After the reaction is complete, dry the solution. Centrifuge the reaction solution. Wash the precipitate after centrifugation and dry it to obtain SDS-modified COFs framework material.

[0055] (5) Add SDS-modified COFs framework material (0.04% of the mass of stevia extract) to the above stevia extract solution, stir and adsorb at 400 r / min for 5 h, then filter, and elute the precipitate with 5 wt% hydrochloric acid solution (mass ratio of hydrochloric acid solution to precipitate is 6:1). Collect the eluent, concentrate the eluent and spray dry it to obtain 273.7 g of stevia, with a total glycoside content of 99.1 wt% and a yield of 99.4%.

[0056] Example 4

[0057] A method for separating stevia and chlorogenic acid includes the following steps:

[0058] (1) Concentrate 1L of stevia extract to 1 / 5 of the original solution volume using a nanofiltration membrane with a molecular weight cutoff of 1000 Da to obtain a concentrated solution;

[0059] (2) The above concentrated solution is pumped into the resin system at a flow rate of 1.5 BV / h for adsorption treatment. The process is stopped when sweetness is observed at the tail column. Then, the LX-8 resin column is desorbed separately using a 60 wt% ethanol solution at a flow rate of 1.5 BV / h, with the volume of the ethanol solution controlled to be 2 BV of the LX-8 resin column volume, to obtain chlorogenic acid desorbent. The first LX-T28 resin column and the second LX-T28 resin column connected in series are desorbed using a 60 wt% ethanol solution at a flow rate of 1 BV / h to obtain stevia desorbent. In the next round of adsorption separation, the LX-8 resin column, the third LX-T28 resin column, the fourth LX-T28 resin column, the first LX-T28 resin column, and the second LX-T28 resin column are connected in series in sequence by switching valves, and this cycle is repeated.

[0060] (3) The chlorogenic acid eluent was concentrated and then spray-dried to obtain 45.9g of chlorogenic acid with a chlorogenic acid content of 41.3wt% and a yield of 90.3%.

[0061] (4) Add 0.05g SDS to a mixed solution of 0.1g p-toluenesulfonic acid, 0.8g 2,6-diaminoanthraquinone and 2ml tetrahydrofuran. After stirring and mixing, add 4.5ml water. Stir at room temperature for 30min at 500r / min. Then add a tetrahydrofuran solution containing 0.6g 1,3,5-tricarboxymethyl phloroglucinol. Continue stirring and react for 8h. After the reaction is complete, dry the solution. Centrifuge the reaction solution. Wash the precipitate after centrifugation and dry it to obtain SDS-modified COFs framework material.

[0062] (5) Add SDS-modified COFs framework material (0.04% of the mass of stevia extract) to the above stevia extract solution, stir and adsorb at 500 r / min for 6 h, then filter, and elute the precipitate with 5 wt% hydrochloric acid solution (mass ratio of hydrochloric acid solution to precipitate is 7:1). Collect the eluent, concentrate the eluent and spray dry it to obtain 273.8 g of stevia, with a total glycoside content of 98.9 wt% and a yield of 99.2%.

[0063] Example 5

[0064] A method for separating stevia and chlorogenic acid includes the following steps:

[0065] (1) Concentrate 1L of stevia extract to 1 / 5 of the original solution volume using a nanofiltration membrane with a molecular weight cutoff of 1000 Da to obtain a concentrated solution;

[0066] (2) The above concentrated solution was pumped into the resin system at a flow rate of 1.5 BV / h for adsorption treatment. The process was stopped when sweetness was observed at the tail column. Then, the LX-8 resin column was desorbed separately using a 60 wt% ethanol solution at a flow rate of 1.3 BV / h, with the volume of the ethanol solution controlled to be 2 BV of the LX-8 resin column volume, to obtain the chlorogenic acid desorbent. The first LX-T28 resin column and the second LX-T28 resin column connected in series were desorbed using a 60 wt% ethanol solution at a flow rate of 1.5 BV / h to obtain the stevia desorbent. In the next round of adsorption separation, the LX-8 resin column, the third LX-T28 resin column, the fourth LX-T28 resin column, the first LX-T28 resin column, and the second LX-T28 resin column were connected in series in sequence by switching valves, and this cycle was repeated.

[0067] (3) The chlorogenic acid eluent was concentrated and then spray-dried to obtain 46.9g of chlorogenic acid with a chlorogenic acid content of 40.5wt% and a yield of 90.5%.

[0068] (4) Add 0.08g SDS to a mixed solution of 0.1g p-toluenesulfonic acid, 0.8g 2,6-diaminoanthraquinone and 2ml tetrahydrofuran. After stirring and mixing, add 4.5ml water. Stir at room temperature for 30min at 400r / min. Then add a tetrahydrofuran solution containing 0.6g 1,3,5-tricarboxymethyl phloroglucinol. Continue stirring and react for 8h. After the reaction is complete, dry the solution. Centrifuge the reaction solution. Wash the precipitate after centrifugation and dry it to obtain SDS-modified COFs framework material.

[0069] (5) Add SDS-modified COFs framework material (0.04% of the mass of stevia extract) to the above stevia extract solution, stir and adsorb at 400 r / min for 5 h, then filter, and elute the precipitate with 5 wt% hydrochloric acid solution (mass ratio of hydrochloric acid solution to precipitate is 8:1). Collect the eluent, concentrate the eluent and spray dry it to obtain 273.8 g of stevia, with a total glycoside content of 98.8 wt% and a yield of 99.1%.

[0070] To further illustrate the effects of the present invention, a detailed description is provided below with reference to several comparative examples.

[0071] Comparative Example 1

[0072] Compared with Example 1, the difference is that in step (1), the solution was concentrated to 1 / 6 of the original solution volume, and other conditions were the same as in Example 1, yielding 55.3g of chlorogenic acid with a total chlorogenic acid content of 31.2wt% and a yield of 82.2%, and 278.9g of stevia with a total glycoside content of 84.9wt% and a yield of 86.7%.

[0073] Comparative Example 2

[0074] Compared with Example 1, the difference is that in step (2), the flow rate of the concentrate during feeding is 2 BV / h, and other conditions are the same as in Example 1, yielding 40.2 g of chlorogenic acid with a total chlorogenic acid content of 40.5 wt% and a yield of 77.5%, and 270.4 g of stevia with a total glycoside content of 98.1 wt% and a yield of 97.2%.

[0075] Comparative Example 3

[0076] Compared with Example 1, the difference is that in step (2), when preparing the chlorogenic acid eluent and stevia eluent, the flow rate of the ethanol solution is 2 BV / h, and other conditions are the same as in Example 1, yielding 38.5g of chlorogenic acid with a total chlorogenic acid content of 40.7wt% and a yield of 74.6%, and 265.7g of stevia with a total glycoside content of 98.5wt% and a yield of 95.9%.

[0077] Comparative Example 4

[0078] Compared with Example 2, the difference is that in step (4), SDS is not added, and other conditions are the same as in Example 2, resulting in 46.3g of chlorogenic acid with a total chlorogenic acid content of 41.0wt% and a yield of 90.4%, and 264.3g of stevia with a total glycoside content of 98.7wt% and a yield of 95.6%.

[0079] Comparative Example 5

[0080] Compared with Example 2, the difference is that in step (4), the amount of SDS added is 0.01g, and the other conditions are the same as in Example 2, resulting in 46.6g of chlorogenic acid with a total chlorogenic acid content of 40.8wt% and a yield of 90.5%, and 265.2g of stevia with a total glycoside content of 98.8wt% and a yield of 96.0%.

[0081] Comparative Example 6

[0082] Compared with Example 2, the difference is that in step (4), the amount of SDS added is 0.5g, and the other conditions are the same as in Example 2, resulting in 46.5g of chlorogenic acid with a total chlorogenic acid content of 40.9wt% and a yield of 90.6%, and 273.9g of stevia with a total glycoside content of 99.1wt% and a yield of 99.4%.

[0083] In summary, this invention employs a resin system consisting of LX-8 and LX-T28 resin columns connected in series to adsorb and separate stevia extract, and combines this with membrane concentration technology. By rationally adjusting the separation and concentration conditions, the resulting stevia extract and chlorogenic acid have high yields and high purity.

[0084] 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 separating stevia and chlorogenic acid, characterized in that, Includes the following steps: (1) The stevia extract is concentrated to 1 / 3-1 / 5 of the stevia extract using a nanofiltration membrane to obtain a concentrate; the stevia extract is prepared by using a 10-60 wt% ethanol solution as the extraction solvent to perform countercurrent extraction on stevia powder, wherein the mass ratio of ethanol solution to stevia powder is 10-20:

1. (2) The above concentrate is adsorbed through a resin system consisting of LX-8 and LX-T28 resin columns connected in series. After adsorption, the LX-8 resin column is eluted separately with 60-80wt% ethanol solution to obtain chlorogenic acid eluate. The LX-28 resin column is eluted with 60-80wt% ethanol solution to obtain stevia eluate. The ratio of LX-8 to LX-T28 resin columns in the resin system is 1:

4. When preparing stevia eluate, the first two LX-T28 resin columns connected in series are eluted with 60-80wt% ethanol solution. In the next round of feeding, LX-8 is still used as the first column of the resin system. The third and fourth LX-T28 columns in the previous round are used as the first and second LX-T28 columns in this round, and so on, in a continuous cycle. The flow rate during sample loading, adsorption and elution is 1-1.5 BV / h. (3) The chlorogenic acid solution was concentrated and then spray-dried to obtain chlorogenic acid; the above stevia solution was concentrated and then spray-dried to obtain stevia.

2. The method for separating stevia and chlorogenic acid according to claim 1, characterized in that, In step (1), the molecular weight cutoff of the nanofiltration membrane is 1000-2000 Da.

3. The method for separating stevia and chlorogenic acid according to claim 1, characterized in that, In step (2), when preparing the chlorogenic acid eluent, the volume of the ethanol solution is 1.5-2 BV of the resin column volume, and when preparing the stevia eluent, the volume of the ethanol solution is 1.5-2 BV of the resin volume.

4. The method for separating stevia and chlorogenic acid according to claim 1, characterized in that, In step (2), the stevia solution was purified before concentration. The purification process included adding an adsorbent to the stevia solution for adsorption treatment, followed by filtration. The precipitate was then eluted with hydrochloric acid solution, and the eluent was collected.

5. The method for separating stevia and chlorogenic acid according to claim 4, characterized in that, The adsorbent is prepared as follows: SDS is added to a mixed solution of p-toluenesulfonic acid, 2,6-diaminoanthraquinone and tetrahydrofuran. After stirring and mixing, water is added. The mixture is stirred at room temperature for 20-30 minutes at a speed of 400-500 r / min. Then, a tetrahydrofuran solution of 1,3,5-tricarboxymethyl phloroglucinol is added. The mixture is stirred and reacted for 7-8 hours. After the reaction is completed, the mixture is dried. The reaction solution is centrifuged, and the precipitate is washed and dried to obtain the SDS-modified COFs framework material.

6. The method for separating stevia and chlorogenic acid according to claim 5, characterized in that, The mass ratio of SDS, p-toluenesulfonic acid, 2,6-diaminoanthraquinone, and 1,3,5-tricarboxymethylphloroglucinol is (0.05-0.1):(0.1-0.15):(0.8-0.9):0.

6.

7. The method for separating stevia and chlorogenic acid according to claim 5, characterized in that, The amount of SDS-modified COFs framework material added is 0.02-0.05% of the mass of stevia extract, and the stirring speed of the adsorption treatment is 400-500 r / min, and the time is 5-6 h. The concentration of the hydrochloric acid solution is 4-5 wt%, and the mass ratio of hydrochloric acid solution to precipitate during elution is (5-10):1.

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