A preparation method of fermented burdock root inulin

Abstract

The invention discloses a method for preparing fermented burdock root inulin, belonging to the technical field of biological fermentation. The technical scheme thereof mainly includes the following preparation steps: (1) pretreatment of burdock root: washing and slicing fresh burdock root and then soaking the root in citric acid solution; (2) fermentation: spraying a bacterial strain aqueous solution on the pretreated burdock root for fermentation treatment; (3) adding water to the fermented product obtained in step (2), grinding the product into a slurry, and then filtering the product to obtain a fermentation liquid; (4) filtering the fermentation liquid through an ultrafiltration membrane, and then purifying the product by a crystallization or chromatography method to obtain the inulin, thereby solving the problem of low inulin extraction rate in the burdock root.

Description

Technical Field

[0001] The invention relates to the technical field of biological fermentation, in particular to a method for preparing fermented burdock root inulin. Background Art

[0002] The main edible part of burdock is the root, which is rich in amino acids, polyphenols, polysaccharides and minerals. Inulin accounts for 35%-45% of the dry weight of burdock root and is the main active ingredient in burdock root. Inulin is a natural polysaccharide with multiple biological activities. It can promote the growth and activity of bifidobacteria and lactobacilli and inhibit the growth of harmful bacteria. It also has physiological activities such as regulating blood lipids, lowering blood sugar, immune regulation and anti-tumor. It plays an important role in regulating body balance, restoring gastrointestinal function, and promoting metabolism. In short, inulin has multiple physiological functions such as regulating intestinal microbial balance and increasing immunity.

[0003] Currently, the extraction process of inulin mostly uses water as the extraction solvent to dissolve and extract burdock. This method generally has the problems of low extraction rate and long time consumption. Summary of the invention

[0004] In order to solve the problem of low extraction rate of inulin in burdock root, the invention provides a method for preparing fermented burdock root inulin.

[0005] The present invention provides a method for preparing fermented burdock root inulin using the following technical scheme:

[0006] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0007] (1) Pretreatment of burdock root: wash and slice the fresh burdock root and soak it in citric acid solution;

[0008] (2) fermentation: spraying the bacterial strain aqueous solution onto the pretreated burdock roots for fermentation;

[0009] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0010] (4) filtering the fermentation broth through an ultrafiltration membrane, and then purifying inulin by crystallization or chromatography.

[0011] By adopting the above technical scheme, the present application can remove impurities on the surface of the burdock root after soaking it in a citric acid solution, and at the same time can soften the burdock root tissue, which is helpful for the later fermentation and can indirectly improve the extraction rate of inulin in the burdock root; after spraying the treated burdock root with an aqueous solution of bacterial strains for fermentation treatment, the extraction rate of inulin in the burdock root can be effectively improved, and after the fermentation liquid is filtered through an ultrafiltration membrane, impurities and macromolecular substances in the fermentation liquid can be effectively removed, thereby improving the purity of inulin.

[0012] Preferably, the concentration of the citric acid solution is 0.1-0.5 wt %, and the soaking time is 10-30 minutes.

[0013] Preferably, the concentration of the bacterial seed aqueous solution is 1-3%, and the spraying amount of the bacterial seed aqueous solution is 20-30% of the weight of the burdock root.

[0014] Preferably, the fermentation process includes three stages. The fermentation temperature in the first stage is 32-37°C and the fermentation time is 8-10h; the fermentation temperature in the second stage is 25-32°C and the fermentation time is 14-15h; the fermentation temperature in the third stage is 20-25°C and the fermentation time is 12-13h.

[0015] By adopting the above technical solution, the fermentation process is divided into three stages, and the fermentation temperature of each stage is different, which can ensure the efficient accumulation of inulin during the fermentation process, thereby effectively improving the extraction efficiency of inulin.

[0016] Preferably, the first stage and the second stage are both stirred and turned over after completion.

[0017] Preferably, the bacterial strain aqueous solution includes a first bacterial strain solution and a second bacterial strain solution, the first bacterial strain solution is sprayed in the first stage, and the second bacterial strain solution begins to be sprayed in the third stage, and the weight ratio of the first bacterial strain solution to the second bacterial strain solution is (2-4):1.

[0018] Preferably, the bacteria in the first bacteria solution include Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of (2-4):(1-3):1.

[0019] Preferably, the bacterial species in the second bacterial species solution is Weissella.

[0020] By adopting the above technical scheme, since the fermentation temperature in the first stage is relatively high, when the first bacterial solution composed of plant lactobacillus, enteric membrane leuconostoc and brewer's yeast is sprayed in the first stage, the metabolic activity of plant lactobacillus, enteric membrane leuconostoc and brewer's yeast can be stimulated to promote their rapid reproduction, and the higher temperature helps to shorten the delay period of bacterial growth, so that it enters the logarithmic growth phase as soon as possible, thereby improving the efficiency of burdock root fermentation, so that inulin can be efficiently accumulated. When the fermentation enters the third stage, the fermentation temperature is maintained at 20-25°C, and the lower fermentation temperature helps to slow down the growth rate of plant lactobacillus, enteric membrane leuconostoc and brewer's yeast, and when the second bacterial solution composed of Weissella is sprayed in the third stage, it helps to retain the stability of the fermentation product, reduce the risk of degradation of the fermentation product caused by excessive growth of the bacterial species, and the addition of Weissella in the third stage can further improve the fermentation efficiency, so that more inulin is accumulated in the burdock root.

[0021] Preferably, the ultrafiltration membrane used in step (4) is a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000.

[0022] Preferably, in step (1), the solid-liquid ratio of burdock root to citric acid solution is 1:(5-9).

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. The present application soaks the burdock root in a citric acid solution to remove impurities on the surface of the burdock root, and at the same time soften the burdock root tissue, which is helpful for later fermentation and can indirectly increase the extraction rate of inulin in the burdock root.

[0025] 2. The phased fermentation temperature of the present application and the use of multiple bacterial strains can promote the rapid reproduction of bacterial strains in the early stage and improve the fermentation efficiency of burdock root. In the later stage, as the fermentation continues, the fermentation temperature decreases to ensure the stability of the fermentation product. Moreover, the addition of Weissella in the third stage can further promote the further accumulation of inulin in burdock root and improve the extraction efficiency of inulin in burdock root. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the embodiments.

[0027] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0028] (1) Pretreatment of burdock root: wash and slice the fresh burdock root and soak it in citric acid solution;

[0029] (2) fermentation: spraying the bacterial strain aqueous solution onto the pretreated burdock roots for fermentation;

[0030] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0031] (4) filtering the fermentation broth through an ultrafiltration membrane, and then purifying inulin by crystallization or chromatography.

[0032] Preferably, the concentration of the citric acid solution is 0.1-0.5 wt %, and the soaking time is 10-30 minutes.

[0033] Preferably, the concentration of the bacterial seed aqueous solution is 1-3%, and the spraying amount of the bacterial seed aqueous solution is 20-30% of the weight of the burdock root.

[0034] Preferably, the fermentation process includes three stages. The fermentation temperature in the first stage is 32-37°C and the fermentation time is 8-10h; the fermentation temperature in the second stage is 25-32°C and the fermentation time is 14-15h; the fermentation temperature in the third stage is 20-25°C and the fermentation time is 12-13h.

[0035] Preferably, the first stage and the second stage are both stirred and turned over after completion.

[0036] Preferably, the bacterial strain aqueous solution includes a first bacterial strain solution and a second bacterial strain solution, the first bacterial strain solution is sprayed in the first stage, and the second bacterial strain solution begins to be sprayed in the third stage, and the weight ratio of the first bacterial strain solution to the second bacterial strain solution is (2-4):1.

[0037] Preferably, the bacteria in the first bacteria solution include Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of (2-4):(1-3):1.

[0038] Preferably, the bacterial species in the second bacterial species solution is Weissella.

[0039] Preferably, the ultrafiltration membrane used in step (4) is a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000.

[0040] Preferably, in step (1), the solid-liquid ratio of burdock root to citric acid solution is 1:(5-9).

[0041] The raw materials used in the examples of this application are all commercially available.

[0042] Example 1

[0043] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0044] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 5 kg of 0.1 wt% citric acid solution and soaked for 30 minutes;

[0045] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 32° C. for 10 hours, then stir and turn once to enter the second stage, ferment at a temperature of 25° C. for 15 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 20° C. for 12 hours; wherein: the total amount of bacterial solution is 0.2 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.133 kg, the spraying amount of the second bacterial solution is 0.067 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 1wt%;

[0046] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 2:1:1; the second bacterial solution contains Weissella;

[0047] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0048] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0049] Example 2

[0050] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0051] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.1 wt% citric acid solution and soaked for 20 minutes;

[0052] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 37° C. for 8 hours, then stir and turn once to enter the second stage, ferment at a temperature of 32° C. for 14 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 25° C. for 13 hours; wherein: the total amount of bacterial solution is 0.2 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.133 kg, the spraying amount of the second bacterial solution is 0.067 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 1-3wt%;

[0053] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 2:1:1; the second bacterial solution contains Weissella;

[0054] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0055] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0056] Example 3

[0057] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0058] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 9 kg of 0.1 wt% citric acid solution and soaked for 15 minutes;

[0059] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 37° C. for 8 hours, then stir and turn once to enter the second stage, ferment at a temperature of 32° C. for 14 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 25° C. for 13 hours; wherein: the total amount of bacterial solution is 0.3 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.2 kg, the spraying amount of the second bacterial solution is 0.1 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 2 wt %;

[0060] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 2:1:1; the second bacterial solution contains Weissella;

[0061] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0062] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0063] Example 4

[0064] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0065] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.3 wt% citric acid solution and soaked for 20 minutes;

[0066] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 37° C. for 8 hours, then stir and turn once to enter the second stage, ferment at a temperature of 32° C. for 14 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 25° C. for 13 hours; wherein: the total amount of bacterial solution is 0.3 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.2 kg, the spraying amount of the second bacterial solution is 0.1 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 3 wt %;

[0067] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 2:1:1; the second bacterial solution contains Weissella;

[0068] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0069] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0070] Example 5

[0071] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0072] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.5 wt% citric acid solution and soaked for 20 minutes;

[0073] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 37° C. for 8 hours, then stir and turn once to enter the second stage, ferment at a temperature of 32° C. for 14 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 25° C. for 13 hours; wherein: the total amount of bacterial solution is 0.3 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.2 kg, the spraying amount of the second bacterial solution is 0.1 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 3 wt %;

[0074] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 3:2:1; the second bacterial solution contains Weissella;

[0075] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0076] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0077] Example 6

[0078] A method for preparing fermented burdock root inulin comprises the following preparation steps:

[0079] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.5 wt% citric acid solution and soaked for 20 minutes;

[0080] (2) Fermentation: squeeze out the water in the burdock root obtained in step (1), and then spray the bacterial solution on the pretreated burdock root for fermentation treatment, specifically: spray the first bacterial solution in the first stage and then ferment at a temperature of 37° C. for 8 hours, then stir and turn once to enter the second stage, ferment at a temperature of 32° C. for 14 hours, stir and turn once to enter the third stage, and then spray the second bacterial solution, and then ferment at a temperature of 25° C. for 13 hours; wherein: the total amount of bacterial solution is 0.3 kg, the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.2 kg, the spraying amount of the second bacterial solution is 0.1 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 3 wt %;

[0081] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 4:3:1; the second bacterial solution contains Weissella;

[0082] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0083] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0084] Example 7

[0085] A method for preparing fermented burdock root inulin, which is different from Example 6 in that the second bacterial strain solution is not sprayed, and specifically comprises the following preparation steps:

[0086] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.5 wt% citric acid solution and soaked for 20 minutes;

[0087] (2) fermentation: squeezing out the water in the burdock root obtained in step (1), and then spraying the pretreated burdock root with a bacterial solution for fermentation, specifically: spraying 0.3 kg of a bacterial solution with a concentration of 3 wt% in the first stage, and then fermenting at a temperature of 37° C. for 8 hours, and then stirring and turning once to enter the second stage, fermenting at a temperature of 32° C. for 14 hours, stirring and turning once to enter the third stage, and then fermenting at a temperature of 25° C. for 13 hours; wherein: the bacterial solution includes Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 4:3:1;

[0088] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0089] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0090] Example 8

[0091] A method for preparing fermented burdock root inulin, which is different from Example 6 in that the fermentation temperature is not processed in stages, and specifically includes the following preparation steps:

[0092] (1) Pretreatment of burdock root: After washing and slicing fresh burdock root, 1 kg of burdock root was added to 7 kg of 0.5 wt% citric acid solution and soaked for 20 minutes;

[0093] (2) fermentation: squeezing out the water in the burdock root obtained in step (1), and then spraying the bacterial strain aqueous solution on the pretreated burdock root for fermentation treatment, specifically: spraying the first bacterial strain solution and then fermenting at a temperature of 37° C. for 8 hours, then stirring and turning once, continuing to ferment at a temperature of 37° C. for 14 hours, stirring and turning once, and then spraying the second bacterial strain solution, and then fermenting at a temperature of 37° C. for 13 hours; wherein:

[0094] The total amount of the bacterial solution is 0.3 kg, and the weight ratio of the first bacterial solution to the second bacterial solution is 2:1, that is, the spraying amount of the first bacterial solution is 0.2 kg, the spraying amount of the second bacterial solution is 0.1 kg, and the concentrations of the first bacterial solution and the second bacterial solution are both 3 wt %;

[0095] The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of 4:3:1; the second bacterial solution contains Weissella;

[0096] (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid;

[0097] (4) filtering the fermentation broth through a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000, and then purifying inulin by crystallization or chromatography.

[0098] Example 9

[0099] A method for preparing fermented burdock root inulin, which is different from Example 6 in that the first bacterial solution only includes plant lactobacillus and brewer's yeast in a weight ratio of 4:1, and the rest are the same as Example 6.

[0100] Example 10

[0101] A method for preparing fermented burdock root inulin, which is different from Example 6 in that Lactobacillus bulgaricus is used in equal proportion to replace Lactobacillus plantarum in the first bacterial solution, and the rest is the same as Example 6.

[0102] Comparative Example 1

[0103] The invention adopts an alcohol extraction method to extract inulin from burdock roots, specifically comprising the following steps: washing and crushing fresh burdock roots, taking 60% ethanol as solvent, loading the burdock root powder into a titration device, performing titration treatment with 60% ethanol, recovering the titration solution, and then recovering the ethanol through a rectification tower to obtain an ethanol-free inulin solution, centrifuging and collecting the filter cake, freeze-drying to obtain crude inulin, and then deproteinizing by enzyme method to obtain purified inulin.

[0104] Comparative Example 2

[0105] The inulin in burdock root was extracted by water extraction method, specifically, fresh burdock root was washed and crushed, and water was used as solvent with a solid-liquid ratio of 1:10, and it was extracted for 1 hour in a water bath at a temperature of 80°C, and the extract was filtered to obtain the extract, and then 95% ethanol was used for precipitation, centrifugation and filter cake were collected, freeze-dried to obtain crude inulin, and then enzymatic deproteinization was used to obtain purified burdock inulin.

[0106] Inulin extraction rate test

[0107] The content of burdock inulin in the products obtained in the above embodiments and control examples was detected, and the detection results are shown in Table 1. The method for determining the inulin content is as follows: the total sugar content in the burdock root extract was measured by the phenol-sulfuric acid method, glucose was used as the standard, and absorbance A was used as the ordinate to obtain a linear regression equation, and the total sugar content in the extract was calculated according to the equation. The reducing sugar content in the burdock root extract was measured by the 3,5-dinitrosalicylic acid method, glucose was used as the standard, absorbance A was used as the ordinate, and glucose concentration C was used as the abscissa, and a standard curve was drawn to obtain a linear regression equation, and the reducing sugar content in the extract was calculated according to the equation. The total sugar content minus the reducing sugar content is the inulin content, and the calculation formula for the inulin extraction rate is: inulin extraction rate % = inulin content in the sample / inulin content in the raw material × 100%.

[0108] Table 1 Inulin extraction rate test results

[0109]

[0110]

[0111] From the table above we can see that:

[0112] Compared with control examples 1-2, the preparation method of Examples 1-6 of the present application has an extraction rate of inulin from burdock roots of more than 80%, which is much higher than the extraction rate using water extraction or alcohol extraction, and the purity of burdock root inulin reaches more than 90%. It can be seen that the preparation method of the present application can effectively improve the extraction rate of inulin from burdock roots.

[0113] Compared with Example 6, when only the first bacterial solution is used in the fermentation process or the fermentation temperature is not staged, or the first bacterial solution lacks Enterobacter mesenteroides or Lactobacillus bulgaricus is used instead of Lactobacillus plantarum, the extraction rate of inulin from burdock root by the preparation method of Examples 7-10 is lower than that of Example 6. It can be seen that the coordination of the steps in the preparation method of the present application can effectively improve the extraction rate of inulin from burdock root.

[0114] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing fermented burdock root inulin, characterized in that: The method comprises the following preparation steps: (1) Pretreatment of burdock root: Wash and slice the fresh burdock root and soak it in citric acid solution; (2) Fermentation: Spraying the bacterial strain aqueous solution onto the pretreated burdock root for fermentation treatment, wherein the fermentation treatment includes three stages: the fermentation temperature of the first stage is 32-37° C. and the fermentation time is 8-10 h; the fermentation temperature of the second stage is 25-32° C. and the fermentation time is 14-15 h; the fermentation temperature of the third stage is 20-25° C. and the fermentation time is 12-13 h; The bacterial solution comprises a first bacterial solution and a second bacterial solution, the first bacterial solution is sprayed in the first stage, and the second bacterial solution starts to be sprayed in the third stage, and the weight ratio of the first bacterial solution to the second bacterial solution is (2-4):1; The first bacterial solution contains Lactobacillus plantarum, Leuconostoc mesenteroides and Saccharomyces cerevisiae in a weight ratio of (2-4): (1-3): 1, and the second bacterial solution contains Weissella spp.; (3) adding water to the fermented product obtained in step (2), grinding it into a slurry, and then filtering it to obtain a fermentation liquid; (4) The fermentation broth is filtered through an ultrafiltration membrane and then purified by crystallization or chromatography to obtain inulin.

2. The method for preparing fermented burdock root inulin according to claim 1, characterized in that: The concentration of the citric acid solution is 0.1-0.5wt%, and the soaking time is 10-30 minutes.

3. The method for preparing fermented burdock root inulin according to claim 1, characterized in that: The concentration of the bacterial strain aqueous solution is 1-3%, and the spraying amount of the bacterial strain aqueous solution is 20-30% of the weight of the burdock root.

4. The method for preparing fermented burdock root inulin according to claim 1, characterized in that: After the first and second stages are completed, the mixture is stirred and turned.

5. The method for preparing fermented burdock root inulin according to claim 1, characterized in that: The ultrafiltration membrane used in the step (4) is a polyetherketone ultrafiltration membrane with a molecular weight cutoff of 5000.

6. The method for preparing fermented burdock root inulin according to claim 1, characterized in that: In the step (1), the solid-liquid ratio of burdock root to citric acid solution is 1:(5-9).

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