Method for preparing hovenia dulcis thunb extract through ultrasonic waves

Abstract

The invention relates to the technical field of plant extraction, and particularly discloses a method for preparing a hovenia dulcis thunb extract through ultrasonic waves. The method comprises the following steps: step 1, pretreating raw materials; step 2, ultrasonic assistance; step 3, multi-stage enzymolysis extraction; step 4, separating and clarifying; step 5, membrane separation and refining; and step 6, concentrating and drying: performing vacuum concentration on the extracting solution subjected to membrane separation at 50-70 DEG C, and then performing low-temperature drying under a vacuum condition to obtain the hovenia dulcis thunb extract which is good in water solubility, high in total flavone content and good in clarity. The steps of physical energy assisted wall breaking, multi-stage composite enzymolysis, membrane separation refining and the like are further organically combined, and the wall breaking efficiency is enhanced, the dissolution rate of active ingredients is increased and the clarity and water solubility of the extract are remarkably improved by optimizing the enzyme ratio, the temperature and pH conditions and the enzyme feeding time sequence and performing refined purification on the extracting solution.

Description

Technical Field

[0001] The invention relates to the technical field of plant extraction, and more particularly to a method for preparing a Hovenia dulcis fruit extract by ultrasonic wave. Background Art

[0002] In the field of plant extraction and functional ingredient preparation, traditional methods usually use organic solvents or acid-base solutions to reflux extract, soak or percolate the raw materials to obtain the desired active ingredients (such as flavonoids, saponins, etc.). However, this technical route has the following obvious shortcomings:

[0003] Solvent residues and environmental issues

[0004] The organic solvent method is prone to solvent residues, environmental pollution and safety hazards, and the recovery and post-processing processes are complicated, increasing production costs.

[0005] Although the acid-base method can achieve a higher dissolution rate for certain active ingredients, it is also easy to destroy some heat-sensitive substances and bring about problems such as equipment corrosion and waste liquid discharge.

[0006] Poor extract clarity and water solubility

[0007] When plant raw materials contain a large amount of insoluble impurities, oils or proteins, relying solely on heat reflux or immersion extraction often results in high turbidity of the extract, and the water solubility, clarity and taste of the final product are difficult to meet the application requirements of food and health products.

[0008] Although enzymatic hydrolysis is gentle and environmentally friendly, it still has limitations

[0009] In recent years, bio-enzymatic hydrolysis technology has attracted much attention because it can destroy plant cell walls at low temperatures and mild conditions. By selecting cellulase, pectinase, protease, etc., the dissolution rate of active ingredients can be improved to a certain extent, and the amount of solvent and energy consumption can be significantly reduced.

[0010] However, single-stage or single-formula enzymatic hydrolysis may still have problems such as limited enzyme activity, long extraction time, incomplete cell wall destruction of some stubborn cell tissues, and fluctuations in extraction effect when raw material batches vary greatly. Some studies have also shown that enzymatic hydrolysis alone sometimes cannot completely remove polysaccharides, colloids or protein macromolecules that affect clarity, resulting in the product appearance still not being transparent or stable enough.

[0011] Lack of multi-dimensional collaborative assistance

[0012] In existing literature and industrial applications, physical methods such as ultrasound, microwaves or pulsed electric fields are often used to accelerate the wall breaking and dissolution processes of plant tissues, respectively. However, if they are combined with enzymatic hydrolysis, it will involve a series of technical difficulties such as enzyme activity protection, physical energy input intensity and time matching, and a mature and reliable process flow has not yet been formed.

[0013] In addition, centrifugation and simple filtration can remove most impurities, but it is difficult to further remove small molecule sugars or colloids; while refining technologies such as macroporous resins and membrane separation can improve product purity and clarity, they are likely to increase equipment costs or operational complexity. Therefore, how to effectively integrate these methods in actual production remains a difficult point.

[0014] In summary, the existing technology mainly faces the following key problems:

[0015] Long extraction time and limited dissolution efficiency: It is difficult to achieve both high efficiency and mildness by relying solely on one-stage enzymatic hydrolysis or traditional thermal extraction, resulting in high energy consumption, loss of active ingredients or insufficient dissolution;

[0016] Product clarity and water solubility defects: impurities, colloids, and grease are difficult to completely remove, which affects the direct application of the finished product in the fields of food, beverages, and health products;

[0017] Insufficient adaptability to multiple batches of raw materials: Raw materials have different composition structures due to different origins and seasons, and a single process is difficult to ensure stable quality and yield;

[0018] Lack of coordinated extraction and graded purification: Physical assistance, enzymatic hydrolysis, multi-stage separation and other means have not yet formed an integrated solution in industrial applications. Summary of the invention

[0019] In order to overcome the shortcomings of the existing technology, the technical solution further combines physical energy-assisted wall breaking, multi-stage composite enzymolysis, membrane separation and refining on the basis of the original enzymatic hydrolysis process, and optimizes the enzyme ratio, temperature and pH conditions, enzyme injection sequence, and fine purification of the extract to enhance the wall breaking efficiency, improve the dissolution rate of active ingredients, and significantly improve the clarity and water solubility of the extract. In this way, it can not only shorten the extraction time, reduce solvent and energy consumption, but also ensure product purity and stable quality, providing a safer, environmentally friendly and economically feasible process route for the production of food, beverages and health products.

[0020] To achieve the above purpose, this utility provides the following technical solutions, mainly including:

[0021] A method for preparing a Hovenia dulcis extract by ultrasonication comprises the following steps:

[0022] Step 1. Raw material pretreatment: crush the Hovenia dulcis raw material into coarse powder, and sieve it in the range of 10-60 mesh;

[0023] Step 2. Ultrasonic assistance: adding a solvent to the coarse powder and applying ultrasonic waves to destroy or loosen the cell walls;

[0024] Step 3. Multi-stage enzymatic extraction: under the enzymatic conditions of the first stage, adding a first group of enzymes to the material obtained in step 2), performing enzymatic hydrolysis, and then adding a second group of enzymes under different pH or temperature conditions from the first stage for further enzymatic hydrolysis; wherein the enzymes include at least two of cellulase, hemicellulase, pectinase, protease and glucosidase;

[0025] Step 4. Separation and clarification: The extract obtained after enzymatic hydrolysis is subjected to solid-liquid separation, including filtration and centrifugation operations, to remove large particle impurities and insoluble components;

[0026] Step 5. Membrane separation and purification: the filtrate or centrifuge obtained in step 4) is separated by an ultrafiltration membrane or a nanofiltration membrane to further remove small molecule impurities or colloidal components;

[0027] Step 6. Concentration and drying: The extract separated by the membrane is vacuum concentrated at 50-70° C., and then dried at low temperature under vacuum conditions to obtain a Hovenia dulcis extract with good water solubility, high total flavonoids content and good clarity.

[0028] In a specific embodiment, the ultrasonic assistance in step 2) is applied intermittently or continuously, the ultrasonic frequency is 20-60 kHz, the power density is 50-200 W / L, and the temperature is controlled not to exceed 60° C. to avoid enzyme inactivation.

[0029] In a specific embodiment, the conditions for the first stage of enzymatic hydrolysis are pH 3.5-5.0 and temperature 45-55°C, and the conditions for the second stage of enzymatic hydrolysis are pH 5.0-7.0 and temperature 50-60°C, and the total enzymatic hydrolysis time is controlled between 2-6 hours.

[0030] In a specific embodiment, the first group of enzymes includes pectinase and papain, the second group of enzymes includes cellulase and hemicellulase, and the activity unit of each enzyme is in the range of 4000-300000 U / g, and the enzyme dosage accounts for 0.01-0.5% of the weight of the Hovenia dulcis powder.

[0031] In a specific embodiment, the membrane separation method in step 5) uses an ultrafiltration membrane with a pore size cutoff molecular weight of 1-50 kDa or a nanofiltration membrane with a pore size cutoff molecular weight of 100-1000 Da, a filtration pressure of 0.1-0.5 MPa, and cross-flow filtration is performed at 25-45°C.

[0032] In a specific embodiment, decolorization or protein removal pretreatment can be performed before membrane separation, and after membrane separation, part or all of the permeate or retentate can be returned to the enzymatic hydrolysis tank to improve the overall extraction efficiency.

[0033] In a specific embodiment, the concentrating and drying step comprises:

[0034] Concentrate to a solid content of 20-40% at 50-60°C and a vacuum degree of -0.09 to -0.095 MPa.

[0035] In a vacuum drying chamber or a spray drying tower, the temperature is controlled not to exceed 65°C for drying to obtain a yellow or light brown powder or block solid.

[0036] In a specific embodiment, the residue after centrifugation or filtration is further subjected to secondary treatment to extract oil, dietary fiber or other active substances, and the residue is used as a functional auxiliary material or feed additive.

[0037] In a specific embodiment, the method further includes testing the turbidity, transmittance and total flavonoids content of the obtained Hovenia dulcis extract, and using the test data to automatically adjust the physical energy application time, enzyme dosage or temperature conditions in step 2) and step 3) to achieve closed-loop control of the extraction process.

[0038] In a specific embodiment, the Hovenia dulcis extract prepared by the method has the following physical and chemical indicators: the turbidity of the aqueous solution is less than 10NTU, the transmittance at a wavelength of 680nm is higher than 90%, the total flavonoid content accounts for 10-30% of the mass fraction of dry matter, and is suitable for direct application in food, beverages, health products or pharmaceutical preparations.

[0039] This technical solution can achieve the following beneficial effects by further introducing physical energy-assisted cell wall breaking, multi-stage composite enzymatic hydrolysis, membrane separation and other refined purification steps on the basis of traditional enzymatic hydrolysis process:

[0040] Significantly improve extraction efficiency

[0041] The synergistic effect of physical energy (such as ultrasound, microwave, etc.) and enzymatic hydrolysis accelerates the destruction of the cell wall and extracellular matrix of Hovenia dulcis, shortens the extraction cycle, reduces energy consumption, and overall improves the dissolution efficiency of active ingredients such as flavonoids.

[0042] Improve product clarity and water solubility

[0043] Multi-stage enzymatic hydrolysis can selectively remove impurities such as pectin, protein, cellulose, etc. in stages, and further remove small molecule sugars and colloids through membrane separation, reduce turbidity, and increase transmittance, making the final product more suitable for adding to aqueous systems such as beverages and health products.

[0044] Effective protection of active ingredients

[0045] The use of mild enzymatic hydrolysis temperature and vacuum low-temperature concentration and drying process can reduce the degradation of flavonoids and other biologically active substances by high temperature or strong acid and alkali, and retain their functionality to the greatest extent.

[0046] Improved adaptability and stability

[0047] Segmented enzymatic hydrolysis and multi-stage separation can flexibly adjust process parameters according to the composition differences of different batches of raw materials, help obtain more stable product quality and yield, and reduce the risk of fluctuations caused by raw material differences.

[0048] Green and easy to scale

[0049] The process mainly uses water, enzyme preparations and physical auxiliary means. It does not require a large amount of organic solvents or strong acid and alkali treatment, and there is relatively little waste liquid and residue. Traditional filtration, centrifugation, membrane separation and other links are relatively mature in the industry, which is conducive to large-scale factory production. DETAILED DESCRIPTION

[0050] The technical scheme in the embodiment of this utility will be described clearly and completely below. Obviously, the described embodiment is only a part of the embodiment of this utility, not all of the embodiments. Based on the embodiment of this utility, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this utility.

[0051] Embodiment 1

[0052] 1. Raw material pretreatment

[0053] Raw materials and coarse powder preparation

[0054] 5 kg of Hovenia dulcis raw material (origin: Hunan, total flavonoid content detected to be about 2.3%) was taken, and after removing impurities, it was crushed into coarse powder using a high-speed grinder, and sieved using a 20-mesh screen to obtain about 4.85 kg of coarse powder.

[0055] 2. Ultrasonic assistance

[0056] Solvents and ultrasonic conditions

[0057] Mix the coarse powder with deionized water at a material-liquid ratio of 1:10 (g:mL), i.e., add 50L of water;

[0058] In a 55°C water bath, ultrasonication was performed continuously for 20 min using an ultrasonicator (frequency 40 kHz, power density about 80 W / L), and the temperature was controlled not to exceed 60°C to avoid enzyme inactivation.

[0059] equipment:

[0060] Ultrasonic cleaning machine (model: KQ-500DE), with an inner tank capacity suitable for accommodating a solution containing coarse powder, a total power of 4kW, and an adjustable frequency of 40±2kHz.

[0061] 3. Multi-stage enzymatic extraction

[0062] First stage enzymatic hydrolysis

[0063] Adjust pH to 4.0 and temperature to 50°C;

[0064] Pectinase and papain (cellulase activity unit 80,000U / g, papain activity unit 60,000U / g) were added, and the total amount of enzyme added accounted for 0.1% of the mass of Hovenia dulcis coarse powder;

[0065] The enzymatic hydrolysis was maintained for 2 hours under a stirrer (100 rpm).

[0066] Second stage enzymatic hydrolysis

[0067] Adjust pH to 6.0 and raise temperature to 55°C;

[0068] Add cellulase and hemicellulase (the activity units of each enzyme are 50,000-100,000 U / g), and the amount of enzyme added in this stage also accounts for 0.1% of the weight of the raw materials;

[0069] The enzymatic hydrolysis was continued for 2 hours.

[0070] The entire enzymatic hydrolysis process took a total of 4 hours.

[0071] 4. Separation and clarification

[0072] Use 200 mesh filter cloth for coarse filtration to remove visible large particles;

[0073] The filtrate was placed in a high-speed centrifuge (model: LG-10M, rotation speed 8,000 r / min, centrifugation for 15 minutes) to separate the insoluble precipitate and obtain a preliminarily clarified supernatant.

[0074] 5. Membrane separation and purification

[0075] The supernatant was filtered through an ultrafiltration membrane with a molecular weight cutoff of 10 kDa (cross-flow operation) at a pressure of 0.3 MPa and 30° C., and the filtrate was used as the final extract.

[0076] After membrane separation, part of the liquid in the retentate (about 10%) is returned to the enzymatic hydrolysis tank to increase the overall yield.

[0077] 6. Concentrated drying

[0078] Vacuum concentration: The obtained filtrate is concentrated at 58°C and vacuum degree -0.09MPa to a solid content of about 25%;

[0079] Drying: Drying in a vacuum drying oven (temperature 60°C, vacuum degree -0.09 MPa) for 8 hours to obtain Hovenia dulcis extract powder. The final yield is about 730 g, and the color is light yellow.

[0080] 7. Experimental data and results

[0081] Aqueous solution clarity

[0082] Take 1g of the product and add 100mL of deionized water to dissolve it. The turbidity is measured to be 8.4NTU and the transmittance at 680nm is 92.1%.

[0083] Total flavonoids content

[0084] The content was determined to be 13.5% (mass fraction of dry matter).

[0085] Comparison

[0086] Compared with the traditional single enzyme method without ultrasound and multi-stage enzymatic hydrolysis, the extraction cycle is shortened by about 1 / 3 and the total flavonoid dissolution rate is increased by about 20%.

[0087] in conclusion

[0088] This example demonstrates that the combination of intermittent ultrasound, two-stage enzymatic hydrolysis and ultrafiltration purification can obtain a Hovenia dulcis extract with good clarity and high water solubility, which is suitable for direct use in functional beverages.

[0089] Embodiment 2

[0090] 1. Raw material pretreatment

[0091] raw material

[0092] 10 kg of Hovenia dulcis raw material (origin: Jiangxi, total flavonoid content detected was 2.2%) was taken, impurities were removed, and the powder was ground into coarse powder by a grinder, and passed through a 40-mesh sieve for later use.

[0093] 2. Ultrasonic assistance

[0094] The coarse powder was mixed with deionized water at a material-liquid ratio of 1:8 (add 80 L of water), and intermittently ultrasonicated by an ultrasonic cleaning machine (model: BI LON-9000F) in a 50°C water bath: ultrasonication for 5 minutes each, standing for 2 minutes, and a total of 4 cycles; the ultrasonic frequency was 30 kHz, the power density was about 100 W / L, and the temperature was controlled at ≤55°C throughout the process.

[0095] 3. Multi-stage enzymatic extraction

[0096] First stage enzymatic hydrolysis

[0097] Adjust pH to 4.5 and temperature to 45°C;

[0098] Pectinase (30,000 U / g) and papain (20,000 U / g) were added, and the amount of enzyme added accounted for 0.05% of the mass of the coarse powder;

[0099] Stir for 1.5 hours.

[0100] Second stage enzymatic hydrolysis

[0101] Adjust pH to 6.5 and temperature to 55°C;

[0102] Add cellulase (80,000 U / g) and hemicellulase (80,000 U / g), the amount of enzyme added is 0.08% of the mass of the coarse powder;

[0103] The enzymatic hydrolysis was continued for another 2.5 hours.

[0104] The total enzymatic digestion time was 4 hours.

[0105] 4. Separation and clarification

[0106] A horizontal centrifuge (speed 7,000r / min, 10 minutes) was used to remove most of the sediment, and the upper clarified liquid was filtered through a 300-mesh filter bag to obtain about 75L of filtrate.

[0107] 5. Membrane separation and purification

[0108] A 100-500Da nanofiltration membrane system (operating pressure 0.2MPa, temperature 25°C) was used for cross-flow filtration to further remove small molecule impurities;

[0109] The retentate is recycled and reused, with about 15% refluxed to the enzymatic hydrolysis stage; the filtrate is the final extract.

[0110] 6. Concentrated drying

[0111] The filtrate was concentrated to a solid content of 30% under a vacuum degree of -0.095 MPa and 60°C;

[0112] Low-temperature spray drying was performed using a spray drying tower (inlet air temperature 65°C, outlet air temperature 50°C) to obtain about 1,450 g of a light brown powdery product.

[0113] 7. Experimental data and results

[0114] Clarity and water solubility

[0115] 1 g of powder was dissolved in 100 mL of deionized water, the turbidity was 7.3 NTU and the transmittance was 93.7%.

[0116] Total flavonoids content

[0117] The measured value is about 12.8%.

[0118] Comparative test

[0119] Compared with single ultrasonic extraction (without enzymatic hydrolysis), the multi-stage enzymatic hydrolysis in this scheme increased the dissolution rate of the active ingredients by more than 18%, and the clarity of the product was also significantly improved.

[0120] in conclusion

[0121] The use of intermittent ultrasound, two-stage enzymatic hydrolysis and nanofiltration membrane refining can not only effectively remove small molecular impurities, but also achieve a high flavonoid recovery rate, which is suitable for the preparation of raw materials for health products with high quality requirements.

[0122] Embodiment 3

[0123] 1. Raw material pretreatment

[0124] raw material

[0125] 8 kg of Hovenia dulcis (origin: Anhui, total flavonoids content was measured to be 2.5%) was taken, crushed and passed through a 60-mesh sieve to obtain about 7.75 kg of coarse powder.

[0126] 2. Ultrasonic assistance

[0127] The material-liquid ratio was 1:12 (adding 96 L of deionized water), and a probe-type ultrasonic device (model: ScientzJY92-I IDN) was used for continuous ultrasonication for 15 minutes; the ultrasonic frequency was 50 kHz, the power density was 120 W / L, and the temperature in the tank was controlled at 50-55°C.

[0128] 3. Multi-stage enzymatic extraction

[0129] First stage enzymatic hydrolysis

[0130] Adjust pH to 3.8 and temperature to 50°C;

[0131] Add pectinase (activity 100,000U / g) and papain (activity 80,000U / g), the enzyme amount accounts for 0.1% of the powder mass;

[0132] The enzymatic hydrolysis was stirred for 1.5 hours.

[0133] Second stage enzymatic hydrolysis

[0134] Adjust pH to 6.2 and raise temperature to 60°C;

[0135] Add cellulase (activity 100,000U / g) and hemicellulase (activity 80,000U / g) at an enzyme dosage of 0.12%;

[0136] Continue enzymatic hydrolysis for 2 hours;

[0137] The total enzymatic hydrolysis time was 3.5 hours.

[0138] 4. Separation and clarification

[0139] After coarse filtration with a 250-mesh filter bag to remove the residue, a disc centrifuge (speed 8,000 r / min, 15 minutes) was used to separate about 90L of clarified liquid.

[0140] 5. Membrane separation and purification

[0141] First, perform decolorization pretreatment: add 0.5% (w / v) activated carbon to the filtrate, stir at 40°C for 30 minutes and then filter;

[0142] The filtrate is cross-flow filtered through an ultrafiltration membrane with a molecular weight cutoff of 5 kDa at 0.35 MPa and 35°C; the permeate is the final extract, and 10% of the retentate can be refluxed back to the enzymatic hydrolysis tank for reuse.

[0143] 6. Concentrated drying

[0144] Vacuum Concentration

[0145] Temperature 58°C, vacuum degree about -0.09MPa, concentrated to a solid content of about 35%;

[0146] dry

[0147] The mixture was dried in a vacuum drying oven (temperature 60° C.) for 6 hours until the moisture content dropped below 6%, yielding 1,200 g of a golden yellow solid, which was crushed and passed through an 80-mesh sieve.

[0148] 7. Experimental data and results

[0149] Clarity

[0150] The turbidity of 1% (w / v) aqueous solution is about 5.6 NTU, and the transmittance at 680 nm is 95.2%.

[0151] Total flavonoids content

[0152] Measured value 14.1%.

[0153] Comparison and advantages

[0154] Under the same feed amount, the flavonoid content in the product is increased by about 25% compared with the traditional process (without using ultrasound and multi-stage enzymatic hydrolysis), and the appearance of the aqueous solution is more transparent and stable.

[0155] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0156] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a Hovenia dulcis extract by ultrasonication, characterized in that: The following steps are involved: Step 1. Raw material pretreatment: crush the Hovenia dulcis raw material into coarse powder, and sieve it in the range of 10-60 mesh; Step 2. Ultrasonic assistance: adding a solvent to the coarse powder and applying ultrasonic waves to destroy or loosen the cell walls; Step 3. Multi-stage enzymatic extraction: under the enzymatic conditions of the first stage, adding a first group of enzymes to the material obtained in step 2), performing enzymatic hydrolysis, and then adding a second group of enzymes under different pH or temperature conditions from the first stage for further enzymatic hydrolysis; wherein the enzymes include at least two of cellulase, hemicellulase, pectinase, protease and glucosidase; Step 4. Separation and clarification: The extract obtained after enzymatic hydrolysis is subjected to solid-liquid separation, including filtration and centrifugation operations, to remove large particle impurities and insoluble components; Step 5. Membrane separation and purification: the filtrate or centrifuge obtained in step 4) is separated by an ultrafiltration membrane or a nanofiltration membrane to further remove small molecule impurities or colloidal components; Step 6. Concentration and drying: The extract separated by the membrane is vacuum concentrated at 50-70° C., and then dried at low temperature under vacuum conditions to obtain a Hovenia dulcis extract with good water solubility, high total flavonoids content and good clarity.

2. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The ultrasonic assistance in step 2) is applied intermittently or continuously, with an ultrasonic frequency of 20-60 kHz, a power density of 50-200 W / L, and the temperature is controlled not to exceed 60° C. to avoid enzyme inactivation.

3. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1 or 2, characterized in that: The conditions for the first stage of enzymolysis are pH 3.5-5.0 and temperature 45-55° C., and the conditions for the second stage of enzymolysis are pH 5.0-7.0 and temperature 50-60° C., and the total enzymolysis time is controlled between 2-6 hours.

4. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The first group of enzymes includes pectinase and papain, the second group of enzymes includes cellulase and hemicellulase, and the activity unit of each enzyme is within the range of 4000-300000 U / g, and the enzyme dosage accounts for 0.01-0.5% of the weight of the Hovenia dulcis coarse powder.

5. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The membrane separation method in step 5) uses an ultrafiltration membrane with a pore size cutoff molecular weight of 1-50 kDa or a nanofiltration membrane with a pore size cutoff molecular weight of 100-1000 Da, a filtration pressure of 0.1-0.5 MPa, and cross-flow filtration is performed at 25-45°C.

6. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 5, characterized in that: Decolorization or protein removal pretreatment can also be performed before membrane separation, and after membrane separation, part or all of the permeate or retentate can be returned to the enzymatic hydrolysis tank to improve the overall extraction efficiency.

7. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The concentration and drying step comprises: Concentrate to a solid content of 20-40% at 50-60°C and a vacuum degree of -0.09 to -0.095 MPa. In a vacuum drying chamber or a spray drying tower, the temperature is controlled not to exceed 65°C for drying to obtain a yellow or light brown powder or block solid.

8. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: It also includes secondary processing of the residue after centrifugation or filtration to extract oil, dietary fiber or other active substances, and use them as functional excipients or feed additives.

9. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The method further includes testing the turbidity, transmittance and total flavonoid content of the obtained Hovenia dulcis extract, and using the test data to automatically adjust the physical energy application time, enzyme dosage or temperature conditions in step 2) and step 3) to achieve closed-loop control of the extraction process.

10. The method for preparing Hovenia dulcis extract by ultrasonic method according to claim 1, characterized in that: The Hovenia dulcis fruit extract prepared by the method has the following physical and chemical indicators: the turbidity of the aqueous solution is lower than 10 NTU, the transmittance at a wavelength of 680 nm is higher than 90%, the total flavonoid content accounts for 10-30% of the mass fraction of the dry matter, and is suitable for direct application in food, beverages, health products or pharmaceutical preparations.