Method for separating and extracting isoflavone aglycones from soybean processing byproducts

Abstract

The invention relates to a method for separating and extracting isoflavone aglycone from soybean processing byproducts, which comprises the following steps: mixing fresh wet bean dregs and yellow serofluid, grinding into slurry, adjusting the pH value of the slurry to 5.5-6.5, heating in a water bath, stirring, and respectively hydrolyzing soybean protein and cellulose by using soybean endogenous protease and cellulase in the slurry; adjusting the pH value of the hydrolysate to 4-5, heating and stirring under the intermittent ultrasonic action, hydrolyzing soybean isoflavone glycoside by utilizing soybean endogenous beta-glucosidase, filtering and centrifuging, and removing filter residues; and adjusting the pH value of the filtrate to be neutral, concentrating under reduced pressure, adsorbing by using a macroporous resin adsorption column, eluting the adsorption column by using deionized water and ethanol in sequence, collecting the eluent, concentrating and drying to obtain the soy isoflavone aglycone. The soy isoflavone aglycone separated and extracted from wet bean dregs and yellow serofluid is high in activity, low in preparation cost and wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing and relates to a method for separating and extracting isoflavone aglycones from soybean processing by-products. Background Art

[0002] Isoflavones (ISO) rich in soybean seeds are a secondary metabolite produced during the growth of soybeans. They have high medicinal value and important physiological functions for the human body. They are mainly divided into two categories: free aglycones and bound glycosides. The free aglycones have higher biological activity. However, soybean isoflavones mainly exist in the form of bound glycosides (glucosides). The free aglycones in the soybean isoflavones extracted from soybeans only account for 2% to 3% of the total amount. Studies have found that only when soybean isoflavone glycosides are hydrolyzed and deglycosylated to convert into free aglycones can they be absorbed by organisms. Bean dregs and yellow pulp water are by-products produced in the production process of soy products. They are basically treated as low-value-added feed or fertilizer, or directly discarded as waste, which not only wastes resources but also causes environmental pollution. However, bean dregs and yellow pulp water contain extremely rich nutrients and functional substances such as isoflavones, soybean saponins, and soybean oligosaccharides. The isoflavones separated and extracted from soybean dregs and yellow pulp water can be used as natural antioxidants and dietary supplements with health functions, which can increase the added value of soybean processing by-products.

[0003] There is a patent technology for extracting isoflavones from soybean processing byproducts in China. The patent (publication number CN102747116A, publication date October 24, 2012) relates to a production process for extracting soybean isoflavone aglycones by enzymatic hydrolysis, which includes: soaking defatted soybean meal, with a material-water ratio of 5:1 to 10:1, adding ethanol to the soaking liquid to account for 10% of the total soaking liquid mass concentration, hydrolyzing the soaking liquid with ultra-high temperature β-glucosidase, the hydrolysis temperature is 90 to 120°C, the hydrolysis time is 1 to 2 hours, solid-liquid separation, solid precipitate is extracted with 60 to 80% ethanol, the extract is filtered through a membrane, and the obtained permeate is deproteinized, concentrated under reduced pressure, and dried to obtain isoflavone aglycones. The patent (publication number CN1769280A, publication date May 10, 2006) relates to a method for extracting soybean isoflavones from yellow pulp water, which comprises: adjusting the pH of fresh yellow pulp water to 7.3-9.0 with an alkaline solution, then adding 0.5% calcium chloride, stirring and standing for 15-30 minutes, and then filtering; adjusting the pH of the filtrate to 4.5-5.6, standing for 1-2 hours at 40-50°C and filtering, and adjusting the pH of the filtrate to 3.5-5.0 with an acid solution; adsorbing the filtrate from bottom to top through a set of adsorption columns equipped with activated carbon adsorbent at 20-35°C, then eluting the adsorption column with acetone solution, and collecting the eluate; heating the eluate at 50-80°C, concentrating under reduced pressure, removing the acetone solvent, and obtaining a mixed solution containing more than 4.5% soybean isoflavones. These patent technologies use commercial enzymes, which have the problem of high extraction cost; if soybean isoflavones are directly extracted without enzymes, the extraction rate is low. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a method for separating and extracting isoflavone aglycones from soybean processing byproducts, characterized in that fresh wet dregs are mixed with yellow pulp water for grinding, pH and temperature are adjusted to activate endogenous enzymes, protein, cellulose and glycoside isoflavones are hydrolyzed to generate free aglycone isoflavones, and then isoflavone aglycones are obtained through adsorption and elution, concentration and drying. The present invention provides a method for preparing aglycones with simple process flow, environmental protection and low extraction cost.

[0005] The principle of the invention is that soybeans are enriched with soybean isoflavones through a soaking and germination process, and then the soybeans are ground by a raw pulping process, and the pulp-residue separation is performed to obtain fresh wet soybean dregs, which are then mixed with yellow pulp water produced in the process of soybean product processing and ground to obtain a mixed pulp with soybean endogenous protease, cellulase and beta-glucosidase activities, and the pH of the mixed pulp is adjusted, and the endogenous protease and cellulase are first used to hydrolyze the soybean protein and cellulose therein to fully dissolve the isoflavones in the mixed pulp, and then the endogenous beta-glucosidase is used to hydrolyze the glucosidic bonds of the isoflavones to obtain biologically active isoflavone aglycones.

[0006] The invention can effectively separate and extract soybean isoflavones with high activity from wet bean dregs and yellow pulp water, and has the advantages of low preparation cost, resource saving, environmental protection and increased economic benefits.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for separating and extracting isoflavone aglycones from soybean processing by-products comprises the following steps:

[0009] S1. Slurry preparation: fresh wet dregs and yellow pulp water were mixed and ground to obtain a mixed slurry 1;

[0010] S2. Protein and cellulose hydrolysis: adjusting the pH of the mixed slurry 1, heating and stirring, and hydrolyzing the soybean protein and cellulose in the mixed slurry 1 by endogenous soybean protease and cellulase to obtain a mixed slurry 2;

[0011] S3. Hydrolysis of isoflavone glycosides: adjusting the pH of the mixed slurry 2, and hydrolyzing the soybean isoflavone glycosides in the mixed slurry 2 by endogenous soybean β-glucosidase under ultrasonic treatment to obtain a mixed slurry 3;

[0012] S4. Collecting the supernatant: The mixed slurry 3 was filtered to remove residues and centrifuged to collect the supernatant;

[0013] S5. Adsorption: adjusting the pH of the supernatant, and after concentration, adsorbing the isoflavone aglycones in the supernatant with a macroporous resin;

[0014] S6. Elution and drying: Use deionized water and ethanol to elute the adsorption column in sequence, collect the eluate containing soybean isoflavone aglycones, and obtain isoflavone aglycones after concentration and drying.

[0015] Preferably, in step S1, the fresh wet bean dregs and yellow pulp water are mixed at a solid-liquid ratio of 1:5 to 1:7 (w / v), fully stirred, and ground to obtain a mixed pulp 1;

[0016] Further preferably, in step S1, the fresh wet bean dregs and yellow pulp water are mixed at a solid-liquid ratio of 1:6 (w / v), fully stirred, and ground to obtain a mixed slurry 1.

[0017] Preferably, in step S2, the pH of the mixed slurry 1 is adjusted to 5.5-6.5 with citric acid and sodium citrate buffer, heated and stirred in a water bath at 45-55° C., and the soybean protein and cellulose are hydrolyzed by the soybean endogenous protease and cellulase in the mixed slurry 1 for 60-70 minutes to obtain a mixed slurry 2;

[0018] Further preferably, in step S2, the pH of the mixed slurry 1 is adjusted to 5.5 with citric acid and sodium citrate buffer, heated and stirred in a 45°C water bath, and the soybean protein and cellulose are hydrolyzed by the soybean endogenous protease and cellulase in the mixed slurry 1 for 65 minutes to obtain a mixed slurry 2.

[0019] Preferably, in step S3, after adjusting the pH of the mixed slurry 2 to 4-5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides are hydrolyzed by using soybean endogenous β-glucosidase in the mixed slurry 2 at a temperature of 50-60° C. and an ultrasonic power of 150-300 W for 70-90 min to obtain a mixed slurry 3;

[0020] Further preferably, in step S3, after adjusting the pH of the mixed slurry 2 to 4.5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides are hydrolyzed by soybean endogenous β-glucosidase in the mixed slurry 2 at a temperature of 55°C and an ultrasonic power of 200 W, and the hydrolysis time is 85 min to obtain a mixed slurry 3.

[0021] Preferably, in step S3, when the isoflavone glycosides are hydrolyzed, the ultrasonic treatment adopts intermittent time-varying ultrasound, and is circulated 2 to 4 times as follows:

[0022] S31. Run for 5 minutes, pause for 2 minutes;

[0023] S32. Run for 3 minutes, pause for 4 minutes;

[0024] S33. Run for 1 minute and pause for 6 minutes.

[0025] Further preferably, in step S3, when the isoflavone glycosides are hydrolyzed, the ultrasonic treatment adopts intermittent time-varying ultrasound, and the cycle is 4 times.

[0026] Preferably, in step S4, the mixed slurry 3 is filtered to remove residues, and the filtrate is centrifuged at 1000g to 1200g for 10 to 15 minutes to obtain a supernatant;

[0027] Further preferably, in step S4, the mixed slurry 3 is filtered to remove residues, and the filtrate is centrifuged at 1100g for 12 minutes using a centrifuge to obtain a supernatant.

[0028] Preferably, in step S5, the pH of the supernatant is adjusted to neutral with NaOH, and after being concentrated under reduced pressure to 1 / 5 to 1 / 2 of the original volume, the soy isoflavones in the supernatant are adsorbed by a macroporous resin;

[0029] Further preferably, in step S5, the pH of the supernatant is adjusted to neutral with NaOH, and after being concentrated under reduced pressure to 1 / 3 of the original volume, the soy isoflavones in the supernatant are adsorbed by a macroporous resin.

[0030] Preferably, in step S6, after the adsorption column is eluted with deionized water until the washing liquid is colorless, the adsorption column is eluted with 70% to 90% ethanol at a flow rate of 1 to 3 BV / h to collect the eluate;

[0031] Further preferably, in step S6, after the adsorption column is eluted with deionized water until the washing liquid is colorless, the adsorption column is eluted with 80% ethanol at a flow rate of 2 BV / h to collect the eluate.

[0032] Preferably, in step S6, the collected eluate is concentrated to a solid content of 25% to 30%, and then subjected to vacuum freeze-drying to obtain soybean isoflavone aglycones.

[0033] Further preferably, in step S6, the collected eluate is concentrated to a solid content of 28%, and then subjected to vacuum freeze-drying to obtain soybean isoflavone aglycones.

[0034] Compared with the prior art, the method for separating and extracting isoflavone aglycones from soybean processing byproducts of the present invention has the following beneficial effects:

[0035] 1. The present invention realizes the extraction of soybean isoflavones from soybean dregs and yellow pulp water, which can efficiently utilize the by-products generated in the soybean processing process, improve the utilization rate of agricultural resources, and reduce the cost of waste treatment;

[0036] 2. The present invention utilizes soybean endogenous protease and cellulase to hydrolyze soybean protein and cellulose, which can significantly increase the dissolution rate of isoflavone glycosides; utilizes soybean endogenous β-glucosidase to hydrolyze the glucosidic bonds on soybean isoflavones to obtain physiologically active soybean isoflavone aglycones;

[0037] 3. The present invention utilizes intermittent time-varying ultrasound to assist enzymatic hydrolysis, so that the enzyme active center is fully exposed, which is conducive to full contact between the enzyme and the soybean isoflavone action site, thereby increasing the speed of the enzymatic reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Technical flow chart of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the present invention is described in detail below in conjunction with specific embodiments.

[0040] First, the term "one embodiment" or "embodiment" as used herein refers to a specific feature or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0041] Secondly, the present invention is described in detail using a process flow diagram, etc. When describing the embodiments of the present invention in detail, for the sake of convenience, the process flow diagram of the present invention will not be described according to the actual use situation, and the technical process diagram is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, reaction equipment, reaction reagent dosage, production operation, etc. should be included.

[0042] Test example:

[0043] A method for separating and extracting isoflavone aglycones from soybean processing byproducts, the experimental process is as follows:

[0044] Fresh wet bean dregs and yellow pulp water are mixed and ground in a weight ratio of 1:6, and then the pH of the mixed pulp 1 is adjusted, heated and stirred, and the soybean endogenous protease and cellulase in the mixed pulp 1 are used to hydrolyze protein and cellulose to promote the dissolution of soybean isoflavone glycosides, thereby facilitating the subsequent hydrolysis of isoflavone glycosides and obtaining more isoflavone aglycones.

[0045] In order to improve the endogenous enzyme activity and the extraction amount of isoflavone glycosides, the enzymatic hydrolysis conditions were optimized. The three-factor three-level test was carried out with the isoflavone aglycone concentration in the hydrolyzate as the response value and the enzymatic hydrolysis time, enzymatic hydrolysis temperature and enzymatic hydrolysis pH as factors. The results are shown in Table 1.

[0046] Table 1 Optimization results of enzymatic hydrolysis conditions

[0047]

[0048] The results of the multiple factor test showed that the most influential factor on the content of isoflavone aglycones extracted by enzymatic hydrolysis was enzymatic hydrolysis pH, followed by enzymatic hydrolysis temperature, and finally enzymatic hydrolysis time. The best enzymatic hydrolysis conditions were enzymatic hydrolysis time of 65 min, enzymatic hydrolysis temperature of 45℃, and enzymatic hydrolysis pH of 5.5.

[0049] Example 1

[0050] like Figure 1 As shown, the present invention provides a method for separating and extracting isoflavone aglycones from soybean processing by-products in the best embodiment, comprising the following steps:

[0051] S1. Slurry preparation: fresh wet dregs and yellow pulp water were mixed at a solid-liquid ratio of 1:6 (w / v), stirred and ground to obtain a mixed slurry 1;

[0052] S2. Protein and cellulose hydrolysis: The pH of the mixed slurry 1 was adjusted to 5.5 with citric acid and sodium citrate buffer, and heated and stirred in a 45°C water bath to utilize the soybean protein and cellulose in the mixed slurry 1 by using the soybean endogenous protease and cellulase. The hydrolysis time was 65 min to obtain a mixed slurry 2;

[0053] S3. Hydrolysis of isoflavone glycosides: After adjusting the pH of the mixed slurry 2 to 4.5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides were hydrolyzed by using endogenous soybean β-glucosidase in the dregs at a temperature of 55°C and an ultrasonic power of 200 W. The hydrolysis time was 84 min to obtain a mixed slurry 3. The ultrasonic treatment was performed by the following intermittent time-varying ultrasonic method and was repeated 4 times:

[0054] S31. Run for 5 minutes, pause for 2 minutes;

[0055] S32. Run for 3 minutes, pause for 4 minutes;

[0056] S33. Run for 1 minute, pause for 6 minutes;

[0057] S4. Collect the supernatant: The mixed slurry 3 was filtered to remove the residue, and the filtrate was centrifuged at 1100g for 12min to obtain a supernatant;

[0058] S5. Adsorption: The pH of the supernatant was adjusted to neutral with NaOH, and after being concentrated to 1 / 3 of the original volume under reduced pressure, the isoflavone aglycones in the supernatant were adsorbed by a macroporous resin;

[0059] S6. Elution and drying: Elute the adsorption column with deionized water until the washing liquid is colorless, then elute the adsorption column with 80% ethanol at a flow rate of 2BV / h, concentrate the collected eluate to a solid content of 28%, and vacuum freeze-dry to obtain soybean isoflavone aglycones.

[0060] Example 2

[0061] Specific steps:

[0062] S1. Slurry preparation: fresh wet dregs and yellow pulp water were mixed at a solid-liquid ratio of 1:6 (w / v), stirred and ground to obtain a mixed slurry 1;

[0063] S2. Protein and cellulose hydrolysis: The pH of the mixed slurry 1 was adjusted to 5.5 with citric acid and sodium citrate buffer, and heated and stirred in a 45°C water bath to utilize the soybean protein and cellulose in the mixed slurry 1 by using the soybean endogenous protease and cellulase. The hydrolysis time was 65 min to obtain a mixed slurry 2;

[0064] S3. Hydrolysis of isoflavone glycosides: After adjusting the pH of the mixed slurry 2 to 4.5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides were hydrolyzed by using endogenous soybean β-glucosidase in the dregs at a temperature of 55°C and an ultrasonic power of 200 W. The hydrolysis time was 84 min to obtain a mixed slurry 3. The ultrasonic treatment was performed in an intermittent time-varying ultrasonic manner as follows, and the process was repeated twice only after the enzymatic hydrolysis started:

[0065] S31. Run for 5 minutes, pause for 2 minutes;

[0066] S32. Run for 3 minutes, pause for 4 minutes;

[0067] S33. Run for 1 minute, pause for 6 minutes;

[0068] S4. Collect the supernatant: The mixed slurry 3 was filtered to remove the residue, and the filtrate was centrifuged at 1100g for 12min to obtain a supernatant;

[0069] S5. Adsorption: The pH of the supernatant was adjusted to neutral with NaOH, and after being concentrated to 1 / 3 of the original volume under reduced pressure, the isoflavone aglycones in the supernatant were adsorbed by a macroporous resin;

[0070] S6. Elution and drying: Elute the adsorption column with deionized water until the washing liquid is colorless, then elute the adsorption column with 80% ethanol at a flow rate of 2BV / h, concentrate the collected eluate to a solid content of 28%, and vacuum freeze-dry to obtain soybean isoflavone aglycones.

[0071] Example 3

[0072] Specific steps:

[0073] S1. Slurry preparation: fresh wet dregs and yellow pulp water were mixed at a solid-liquid ratio of 1:6 (w / v), stirred and ground to obtain a mixed slurry 1;

[0074] S2. Protein and cellulose hydrolysis: The pH of the mixed slurry 1 was adjusted to 5.5 with citric acid and sodium citrate buffer, and heated and stirred in a 45°C water bath to utilize the soybean protein and cellulose in the mixed slurry 1 by using the soybean endogenous protease and cellulase. The hydrolysis time was 65 min to obtain a mixed slurry 2;

[0075] S3. Hydrolysis of isoflavone glycosides: After adjusting the pH of the mixed slurry 2 to 4.5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides were hydrolyzed by using endogenous soybean β-glucosidase in the dregs at a temperature of 55°C and an ultrasonic power of 200 W. The hydrolysis time was 84 min to obtain a mixed slurry 3. The ultrasonic treatment was performed in an intermittent time-varying ultrasonic manner as follows, and the process was repeated only once after the enzymatic hydrolysis started:

[0076] S31. Run for 5 minutes, pause for 2 minutes;

[0077] S32. Run for 3 minutes, pause for 4 minutes;

[0078] S33. Run for 1 minute, pause for 6 minutes;

[0079] S4. Collect the supernatant: The mixed slurry 3 was filtered to remove the residue, and the filtrate was centrifuged at 1100g for 12min to obtain a supernatant;

[0080] S5. Adsorption: The pH of the supernatant was adjusted to neutral with NaOH, and after being concentrated to 1 / 3 of the original volume under reduced pressure, the isoflavone aglycones in the supernatant were adsorbed by a macroporous resin;

[0081] S6. Elution and drying: Elute the adsorption column with deionized water until the washing liquid is colorless, then elute the adsorption column with 80% ethanol at a flow rate of 2BV / h, concentrate the collected eluate to a solid content of 28%, and vacuum freeze-dry to obtain soybean isoflavone aglycones.

[0082] Comparative Example 1

[0083] A method for preparing soybean isoflavone aglycones, the preparation method is as follows:

[0084] Compared with Example 1, the difference is that step S2 of hydrolyzing protein and cellulose is omitted, and the remaining operations are the same as those in Example 1.

[0085] The specific steps are omitted.

[0086] Comparative Example 2

[0087] A method for preparing soybean isoflavone aglycones, the preparation method is as follows:

[0088] Compared with Example 1, the only difference is that the S3 soybean isoflavone hydrolysis step is omitted, and the remaining operations are the same as Example 1.

[0089] The specific steps are omitted.

[0090] Test Case

[0091] Determination method of isoflavone aglycones

[0092] Soy isoflavone aglycones were determined by high performance liquid chromatography. Sample preparation: 10 mg of sample was accurately weighed, 500 μL of 80% methanol was added, ultrasonic extraction was performed at 40°C for 1 h, centrifuged at 4°C and 1000 rpm for 10 min, the supernatant was separated and filtered through a 0.45 μm organic filter membrane, and analyzed by high performance liquid chromatography equipped with an Agilent SB-C18 column (5 μm particle size, 4.6×150 mm).

[0093] The concentrations of the standard products are: 2, 4, 8, 16, 32, and 64 μg / mL.

[0094] The conditions of HPLC were as follows: flow rate was 1 mL / min; mobile phase: solution A was 0.1% acetic acid in water, and solvent B was 0.1% acetic acid in acetonitrile. The flow conditions of HPLC included a gradient of solvent B of 13% to 35%. The duration was 52 min, the column temperature was 35°C, the injection volume was 20 μL, and the eluted isoflavones were detected at 260 nm.

[0095] Comparison of test results:

[0096] The isoflavone aglycones obtained from Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were subjected to comparative tests, and the test contents and results are as follows:

[0097] Determination of the yield of soybean isoflavone aglycones:

[0098]

[0099] Where P is the yield of soybean isoflavone aglycones;

[0100] A1—quality of soybean isoflavone aglycones;

[0101] A0—Raw material quality.

[0102] The test results are shown in Table 2.

[0103] Table 2 Test case test results

[0104]

[0105] As shown in Table 2, the yields of soybean isoflavone aglycones in Examples 1, 2 and 3 are higher than those in Comparative Examples 1 and 2. This is because in the examples, the wet bean dregs and fresh yellow pulp water mixed slurry are treated with protease and cellulase, and the soybean protein and cellulose in the hydrolyzed slurry are hydrolyzed to facilitate the further dissolution of isoflavones; at the same time, ultrasonic assisted enzymolysis is used in the hydrolysis process of soybean isoflavone glycosides, so that the enzyme active center fully acts on the glucosidic bond on the soybean isoflavone glycosides, accelerating the cleavage of the glucosidic bond; while there is no soybean protein and cellulose hydrolysis step in Comparative Example 1, and there is no soybean isoflavone glycoside hydrolysis step in Comparative Example 2, so the yields of isoflavone aglycones are not as good as those in the examples. The test results (Table 2) show that the hydrolysis of soybean protease and cellulase can significantly increase the dissolution amount of soybean isoflavones, thereby improving the yield of soybean isoflavone aglycones.

[0106] The test results (Table 2) also show that the yield of soybean isoflavone aglycones in Example 1 is higher than that in Example 2 and Example 3. This is because in Example 1, intermittent time-varying ultrasonic treatment is always used during the hydrolysis of soybean isoflavone glycosides, which is beneficial to the enzymatic hydrolysis reaction of glycoside-type soybean isoflavones, thereby improving the enzymatic hydrolysis efficiency.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for separating and extracting isoflavone aglycones from soybean processing by-products, characterized in that: The steps include: S1. Slurry preparation: fresh wet dregs and yellow pulp water were mixed and ground to obtain a mixed slurry 1; S2. Protein and cellulose hydrolysis: adjusting the pH of the mixed slurry 1, heating and stirring, and hydrolyzing the soy protein and cellulose in the mixed slurry 1 by endogenous soybean protease and cellulase to obtain a mixed slurry 2; S3. Hydrolysis of isoflavone glycosides: adjusting the pH of the mixed slurry 2, performing ultrasonic treatment, and hydrolyzing the soybean isoflavone glycosides by endogenous soybean β-glucosidase in the mixed slurry 2 to obtain a mixed slurry 3; S4. Collecting the supernatant: The mixed slurry 3 was filtered to remove residues and centrifuged to collect the supernatant; S5. Adsorption: adjusting the pH of the supernatant, and after concentration, adsorbing the isoflavone aglycones in the supernatant using a macroporous resin adsorption column; S6. Elution and drying: Use deionized water and ethanol to elute the adsorption column in sequence, collect the eluate containing soybean isoflavone aglycones, concentrate and dry to obtain soybean isoflavone aglycones.

2. The method according to claim 1, characterized in that In the step S1, fresh wet bean dregs and yellow pulp water are mixed at a solid-liquid ratio of 1:5 to 1:7 (w / v), fully stirred, and ground to prepare a mixed pulp 1.

3. The method according to claim 1, characterized in that In the step S2, the pH of the mixed slurry 1 is adjusted to 5.5-6.5 with citric acid and sodium citrate buffer, and the mixed slurry is heated and stirred in a water bath at 45-55° C. The soybean protein and cellulose in the mixed slurry 1 are hydrolyzed by the soybean endogenous protease and cellulase in the mixed slurry 1, and the hydrolysis time is 60-70 minutes to obtain a mixed slurry 2.

4. The method according to claim 1, characterized in that: In the step S3, after adjusting the pH of the mixed slurry 2 to 4-5 with citric acid and sodium citrate buffer, the soybean isoflavone glycosides in the mixed slurry 2 are hydrolyzed by using soybean endogenous β-glucosidase in the mixed slurry 2 at a temperature of 50-60° C. and an ultrasonic power of 150-300 W. The hydrolysis time is 70-90 minutes to obtain a mixed slurry 3.

5. The method according to claim 1, characterized in that In the step S3, when the soybean isoflavone glycosides are hydrolyzed, the ultrasonic treatment is performed by intermittent time-varying ultrasonic treatment in the following manner, and the process is repeated 2 to 4 times: S31. Run for 5 minutes, pause for 2 minutes; S32. Run for 3 minutes, pause for 4 minutes; S33. Run for 1 minute and pause for 6 minutes.

6. The method according to claim 1, characterized in that In the step S4, the mixed slurry 3 is filtered to remove residues, and the filtrate is centrifuged at 1000g to 1200g for 10 to 15 minutes to obtain a supernatant.

7. The method according to claim 1, characterized in that In the step S5, the pH of the supernatant is adjusted to neutral with NaOH, and after being concentrated under reduced pressure to 1 / 5 to 1 / 2 of the original volume, the soybean isoflavone aglycones in the supernatant are adsorbed by a macroporous resin adsorption column.

8. The method according to claim 1, characterized in that In the step S6, the adsorption column is eluted with deionized water until the washing liquid is colorless, and then the adsorption column is eluted with 70% to 90% ethanol at a flow rate of 1 to 3 BV / h to collect the eluate.

9. The method according to claim 1, characterized in that: In the step S6, the collected eluate is concentrated to a solid content of 25% to 30%, and then subjected to vacuum freeze-drying to obtain soybean isoflavone aglycones.

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