Preparation method of red date extract

Abstract

The invention relates to the technical field of food processing, and particularly discloses a preparation method of a red date extract. The extract is prepared from red dates as a raw material through pretreatment, enzymolysis, solid-liquid separation, aroma recovery, concentration, membrane integrated concentration and finished product blending, and a red date extract A and a red date extract B are prepared as cores. The preparation method comprises the following steps: soaking and softening red dates, removing kernels, crushing and grinding into pulp, adjusting the pH value of the pulp, carrying out enzymolysis and heating for enzyme deactivation, carrying out solid-liquid separation, respectively carrying out aroma recovery and concentration on residues and filtrate, combining aromatic water, filtering through a ceramic membrane, concentrating through a reverse osmosis membrane, and finally mixing the two extracts to obtain a finished product. The red date extract can be used for food flavor blending and tobacco flavor blending, and is rich in flavor, free of organic solvent residues and complete in nutrient component retention; the preparation method is easy and convenient to operate, low in equipment investment, low in energy consumption, environmentally friendly, capable of fully recycling aroma substances of the red dates, capable of improving the extraction efficiency, suitable for industrial large-scale production and capable of effectively guaranteeing the product quality.

Description

Technical Field

[0001] This application relates to the field of food processing technology, and more specifically, it relates to a method for preparing a jujube extract. Background Technology

[0002] Red dates are the dried, ripe fruit of the jujube plant (Ziziphus jujuba), a member of the Rhamnaceae family. Rich in nutrients, including sugars and amino acids, red dates are a traditional natural flavoring ingredient. Their extract possesses the characteristic sweet aroma of red dates, a mild sweetness with a hint of rose-like aroma, and is widely used in food processing and tobacco flavoring. In food processing, red date extract is frequently used to flavor dairy products; in tobacco flavoring, it provides the characteristic caramelized sweetness of red dates, meeting the flavor requirements of related products. Therefore, the preparation of red date extract has significant practical application value, and there is an urgent market demand for efficient and high-quality methods for preparing red date extract.

[0003] Currently, there are various processes for preparing jujube extract. Traditional processes often employ alcohol solution extraction, high-temperature cooking, or high-temperature concentration. These processes are often inefficient, energy-intensive, and prone to significant loss of jujube flavor compounds. Furthermore, alcohol extraction can lead to environmental pollution. Some patents have attempted to improve these processes. For example, patent CN106376912A uses freeze-drying and macroporous resin adsorption technologies to recover jujube flavor compounds. However, freeze-drying equipment is costly and energy-intensive, hindering industrial production. Additionally, macroporous resin adsorption requires an alcohol solution for flavor recovery, resulting in alcohol content in the final extract, which significantly limits the product's applications. Therefore, providing a method for preparing jujube extract that requires minimal equipment investment, consumes little energy, is easy to operate, does not introduce organic solvents, fully preserves the natural flavor of jujube, improves extraction efficiency, and is suitable for large-scale industrial production has become a key technical problem that needs to be solved. Summary of the Invention

[0004] To address the problems of high equipment investment, high energy consumption, complex operation, or the need to introduce organic solvents in the preparation process of jujube extract, which result in significant loss of jujube flavor substances and make it difficult to achieve large-scale industrial production while ensuring the green and environmentally friendly nature and flavor quality of the product, this application provides a method for preparing jujube extract.

[0005] The method for preparing jujube extract provided in this application adopts the following technical solution: A method for preparing jujube extract includes the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into pulp to obtain red date pulp. S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a weakly acidic range, add enzyme solution for constant temperature enzymatic hydrolysis, and then perform enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate; S4. Residue aroma recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. S5. Primary concentration of filtrate and aroma recovery: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B; wherein, the modified chitosan reverse osmosis membrane is prepared by steps including tea tree oil spraying, ozone sterilization and laser drying. S7. Finished product preparation: Mix the jujube extract A and the jujube extract B in a certain proportion to obtain the final jujube extract.

[0006] By employing the above technical solutions, the soaking and softening process of raw materials softens the tissue structure of jujubes, promoting the initial dissolution of effective components and laying the foundation for subsequent processes. Pulverization further increases the contact area between the jujube raw materials and the enzymatic hydrolysate, making subsequent enzymatic reactions easier to carry out. Enzymatic extraction uses a gentle method to break down the cell walls of jujubes, converting difficult-to-dissolve components into easily soluble forms, effectively improving extraction efficiency while minimizing damage to the nutritional components of the jujubes. Solid-liquid separation achieves precise separation of residue and filtrate, facilitating subsequent recycling. Residue aroma recovery and primary filtrate concentration specifically recover aroma substances from the residue and filtrate, reducing flavor loss. Ceramic membrane filtration purifies the aromatic water, while tea tree oil-modified chitosan reverse osmosis membranes combine biocompatibility and high retention capacity, efficiently retaining effective components. The final product blending achieves a fusion of the flavors and effective components of the two extracts. The entire process uses pure water extraction without introducing organic solvents, replacing the traditional high-pressure and high-temperature cooking process. This not only better preserves the active ingredients in jujubes, such as cyclic adenosine monophosphate and vitamin C, but also reduces equipment investment and energy consumption. The process is simple to operate, conforms to the concept of green environmental protection, and is suitable for the needs of large-scale industrial production.

[0007] Preferably, in step S1, the mass ratio of the jujubes to deionized water is 1:4 to 1:8, and the soaking and softening time is 12h to 24h.

[0008] By adopting the above technical solution and rationally controlling the ratio of jujubes to deionized water and the soaking time, the jujubes can be fully softened, allowing for the initial dissolution of their effective components. This creates favorable conditions for subsequent grinding, pulverization, and enzymatic extraction processes. Appropriate soaking conditions prevent insufficient soaking, which can lead to a hardened jujube structure, hindering subsequent grinding and pulverization and affecting the effectiveness of enzymes during enzymatic hydrolysis. Simultaneously, prolonged soaking prevents the loss of effective components into the water, avoiding raw material waste and reduced extraction efficiency. This precise soaking control ensures the jujube raw material is in optimal processing condition, allowing subsequent processes to proceed smoothly and efficiently. This provides a fundamental guarantee for the stability of the entire preparation process and the extraction effect, further improving the quality and yield of the jujube extract.

[0009] Preferably, in step S1, the pulverizing and grinding process is carried out using a colloid mill or a homogenizer, and the fineness of the resulting jujube pulp is controlled to be able to pass through a 40-50 mesh sieve.

[0010] By adopting the above technical solution, colloid mills or homogenizers can be used for pulverization and grinding, allowing for flexible selection of equipment based on actual production needs and adapting to different scales of industrial production. Reasonable control of the fineness of the jujube pulp can break the softened jujubes into suitable particle sizes, maximizing the contact area between the jujube raw material and the subsequent enzymatic hydrolysis solution, allowing the enzyme to more fully act on the jujube cell walls. Compared to ordinary crushing methods, this precise fineness control makes the enzymatic hydrolysis process more efficient, promoting the decomposition of pectin, cellulose, and other components in the cell walls, making it easier for nutrients and flavor substances within the cells to dissolve. At the same time, suitable pulp fineness can also prevent excessively large particles from clogging subsequent filters, reducing process losses, ensuring the stability of enzymatic hydrolysis efficiency and extraction effects, providing a guarantee for the smooth implementation of subsequent processes, and improving the continuity and efficiency of the entire preparation process.

[0011] Preferably, in step S2, the weak acid range is pH 5.5 to 6.5; the isothermal enzymatic hydrolysis conditions are: reacting with an enzyme solution of 0.02% to 0.04% by mass at 45°C to 50°C for 1 to 3 hours; and the temperature-induced enzyme inactivation treatment conditions are: maintaining at 85°C to 90°C for 0.5 to 1 hour.

[0012] By employing the above technical solutions, the jujube pulp is adjusted to a suitable slightly acidic range, providing an optimal acid-base environment for the enzymatic hydrolysis reaction. This allows the enzymes to fully exert their catalytic effect and improve hydrolysis efficiency. Controlled constant-temperature hydrolysis ensures that the enzymes remain in optimal activity, specifically breaking down specific components in the jujubes and converting them into more soluble forms, further improving extraction efficiency. The gentle hydrolysis conditions also reduce the damage to heat-sensitive nutrients and flavor compounds. Temperature-based enzyme inactivation treatment promptly terminates the hydrolysis reaction, preventing excessive decomposition of jujube nutrients and the destruction or conversion of effective components into useless substances, ensuring a controllable hydrolysis process. This precise control of hydrolysis conditions not only fully dissolves the effective components and flavor compounds in the jujubes but also maximizes the preservation of their nutritional quality, laying the foundation for subsequent processes and the quality of the final product.

[0013] Preferably, in step S2, the enzyme solution contains at least one of pectinase, cellulase, and glycosidase; the alkaline solution used to adjust the pH value is a sodium hydroxide solution or potassium hydroxide solution with a mass concentration of 3% to 8%.

[0014] By employing the above technical solutions and selecting suitable enzyme solutions, pectin, cellulose, and glycosides in the cell walls of jujubes can be specifically decomposed, precisely disrupting the cell wall structure and promoting the full dissolution of effective components and flavor substances within the cells. Compared to single enzymatic hydrolysis, this selection of a complex enzyme system or a single high-efficiency enzyme can further improve extraction efficiency and effectiveness. Adjusting the pH value using sodium hydroxide or potassium hydroxide solutions within a specific concentration range allows for precise control of the jujube pulp's acidity and alkalinity, ensuring it perfectly matches the requirements of the enzymatic hydrolysis reaction. This guarantees that the enzyme remains in its optimal activity state, preventing reduced or inactivated enzyme activity due to unsuitable pH levels, which would negatively impact the hydrolysis effect. Appropriate selection and concentration control of the alkali solution also prevent damage to the effective components of jujubes and facilitates subsequent pH adjustment, ensuring the entire enzymatic hydrolysis process is efficient and stable, thus improving the quality of the jujube extract.

[0015] Preferably, in step S4, the set vacuum and temperature conditions are: vacuum degree 1 mbar to 2 mbar, temperature 50°C to 60°C; in step S5, the decompression conditions are: vacuum degree 45 mbar to 50 mbar, temperature 40°C to 50°C.

[0016] By employing the above-mentioned technical solution, the solid residue is vacuum-dried. The gentle drying conditions allow the aroma compounds in the residue to slowly volatilize, facilitating their full recovery through condensation. This avoids the decomposition or loss of aroma compounds due to high-temperature drying, maximizing the preservation of the natural flavor of the jujubes. The filtrate is then concentrated under reduced pressure. The low-temperature environment effectively reduces the loss of heat-sensitive active ingredients and aroma compounds in the filtrate, ensuring the nutritional quality and flavor of jujube extract A. This targeted control of drying and concentration conditions allows for the full recovery of aroma compounds and active ingredients from both the residue and the filtrate, improving raw material utilization and reducing waste. Simultaneously, the gentle processing conditions reduce energy consumption, aligning with green and environmentally friendly production principles, further enhancing the flavor and quality of the jujube extract, and providing high-quality intermediates for subsequent finished product formulation.

[0017] Preferably, the refrigerant temperature recovered in step S4 and the refrigerant temperature recovered in step S5 are both between 0°C and 5°C.

[0018] By employing the above-mentioned technical solution and controlling the refrigerant temperature during condensation recovery, the volatile jujube aroma substances released during vacuum drying and reduced pressure concentration can be rapidly condensed and liquefied, facilitating collection and recovery. A suitable refrigerant temperature ensures sufficient condensation of the aroma substances, reducing their volatilization loss during condensation and preventing waste due to incomplete condensation. This ensures that the recovered aromatic water contains sufficient aroma substances of excellent quality. Sufficient aroma substances provide a good foundation for subsequent membrane-integrated concentration to prepare jujube extract B, giving it a rich, natural jujube flavor. Simultaneously, precise refrigerant temperature control improves condensation recovery efficiency, shortens the production cycle, reduces energy consumption, and ensures the entire aroma recovery process is highly efficient and stable, further enhancing the overall flavor and quality of the jujube extract.

[0019] Preferably, in step S6, the ceramic membrane used for ceramic membrane filtration has a pore size of 0.05 μm to 0.2 μm and an operating pressure of 2 bar to 6 bar; the modified chitosan reverse osmosis membrane concentration operates at an operating pressure of 10 bar to 30 bar.

[0020] By employing the above-mentioned technical solutions, ceramic membrane filtration can effectively filter out impurities, macromolecular pollutants, and microorganisms from aromatic water, deeply purifying it and preventing impurities from affecting subsequent concentration and the purity of the final product. The selection of ceramic membranes is tailored to the treatment requirements of aromatic water, ensuring filtration efficiency and purification effects, and providing clean raw materials for subsequent membrane concentration processes. Modified chitosan reverse osmosis membrane concentration can efficiently concentrate aromatic water, allowing water to quickly permeate through the membrane while firmly retaining the effective components and aroma substances in jujubes, preventing the loss of effective components. This membrane-integrated concentration process does not require the introduction of organic solvents, conforms to the concept of green environmental protection, and has high concentration efficiency and low energy consumption, ensuring the purity and quality of jujube extract B, allowing it to fully retain the natural flavor and nutrients of jujubes.

[0021] Preferably, in step S6, the ozone concentration for ozone sterilization is 5 mg / L to 15 mg / L, and the treatment time is 0.2 h to 1 h; the laser power for laser drying is 200 W to 300 W, the treatment temperature is 70 °C to 90 °C, and the irradiation time is 0.2 h to 0.8 h; the spraying distance for tea tree oil is 70 mm to 90 mm, and the spraying rate is 50 mm / s to 70 mm / s.

[0022] By employing the above technical solutions, ozone sterilization treatment can thoroughly sterilize the chitosan reverse osmosis membrane after tea tree oil spraying, effectively removing microorganisms from the membrane surface, preventing microbial growth during use, and preventing microbial contamination of aromatic water and jujube extract B, thus ensuring product hygiene and safety. Laser drying treatment can quickly dry the membrane surface, firmly fixing the tea tree oil modified layer to the membrane surface, preventing the modified layer from falling off, and ensuring the long-lasting and stable modification effect of the membrane. Controlled spraying of tea tree oil allows it to evenly cover the membrane surface, fully utilizing the permeability and antibacterial properties of tea tree oil, improving the permeate flux and treatment efficiency of the reverse osmosis membrane, while enhancing the membrane's antibacterial performance and extending its service life. This precise control of membrane modification conditions ensures that the modified chitosan reverse osmosis membrane is always in optimal operating condition, guaranteeing a stable and efficient membrane concentration process, and further improving product quality.

[0023] Preferably, in step S5, the vacuum concentration is stopped when the soluble solids content of the system reaches 60% to 85%, and jujube extract A is obtained; in step S7, the mixing mass ratio of jujube extract A to jujube extract B is 1:2 to 1:5.

[0024] By adopting the above technical solution and controlling the endpoint of the primary concentration of the filtrate, the concentration of the effective components in jujube extract A can be ensured to be appropriate. This avoids both excessively low concentration, which would require large-scale concentration in subsequent formulations, increasing energy consumption and production cycle, and excessively high concentration, which would lead to excessive viscosity of the extract, affecting subsequent mixing and the quality of the finished product. Controlling the mixing ratio of the two extracts allows the nutrients in jujube extract A to fully integrate with the flavor substances in jujube extract B, achieving a balanced combination of nutrition and flavor. This results in a final jujube extract that has both sufficient effective components and a rich, natural jujube flavor. This precise control of the concentration endpoint and mixing ratio ensures the stable quality of the final jujube extract, making it suitable for practical applications in different fields such as food and tobacco, and enhancing the product's applicability and market competitiveness.

[0025] In summary, this application has the following beneficial effects: 1. This application adopts a complete process that proceeds sequentially, including raw material pretreatment, enzymatic extraction, solid-liquid separation, residual aroma recovery, primary concentration and aroma recovery of filtrate, membrane integrated concentration, and finished product blending. Due to the synergistic cooperation of each step, soaking and softening combined with pulverization and grinding replaces the traditional high-pressure, high-temperature cooking and pitting method. Low-temperature enzymatic hydrolysis reduces the number of extractions. Pure water extraction without organic solvents and membrane integrated concentration processes are used, which achieve the effects of low equipment investment, low energy consumption, simple operation, and green environmental protection. At the same time, it can fully release the flavor of jujubes and improve extraction efficiency, making it suitable for large-scale industrial production.

[0026] 2. In this application, isothermal enzymatic hydrolysis and temperature-induced enzyme inactivation under specific weakly acidic conditions are preferred. Appropriate types of enzyme solutions are selected and the pH value is adjusted with a specific concentration of alkaline solution. Since low-temperature enzymatic hydrolysis can avoid the destruction of heat-sensitive flavor substances, the enzyme solution can effectively destroy the cell wall structure of jujube and promote the dissolution of effective components. Temperature-induced enzyme inactivation can terminate the enzymatic hydrolysis reaction and avoid excessive decomposition, thus achieving the effect of fully releasing the flavor of jujube, improving extraction efficiency and preserving the effective components intact.

[0027] 3. The method of this application uses vacuum drying to recover aroma from solid residue under specific vacuum and temperature conditions, controls the refrigerant temperature to ensure full condensation of aroma substances, uses ceramic membrane filtration and modified chitosan reverse osmosis membrane to concentrate aromatic water, and modifies the reverse osmosis membrane by spraying tea tree oil, ozone sterilization and laser drying. Therefore, it achieves the effect of high recovery rate of jujube aroma substances, no introduction of organic solvents, high product purity and outstanding flavor. At the same time, the membrane modification treatment further improves the concentration efficiency and membrane performance.

[0028] 4. In this application, it is preferred to soak and soften red dates with deionized water at a specific mass ratio, control the soaking time, and use a colloid mill or homogenizer to grind and pulverize the slurry while controlling the fineness of the slurry. Because suitable soaking conditions can fully soften the red date tissue, and reasonable grinding and pulverization fineness can increase the contact area between the raw material and the enzymatic hydrolysate, the subsequent enzymatic hydrolysis reaction is more complete, the effective components are more thoroughly dissolved, the process is smoothly connected, and the energy consumption is further reduced.

[0029] 5. The method of this application controls the endpoint of the soluble solids content in the primary concentration of the filtrate, and mixes jujube extract A and extract B in a specific ratio. Since the concentration endpoint can ensure that the concentration of effective components in extract A is appropriate, the reasonable mixing ratio can make the flavor and effective components of the two extracts complement each other. Therefore, the final jujube extract has a balanced flavor and stable content of effective components, which can better meet the needs of practical applications. Attached Figure Description

[0030] Figure 1 This is a flowchart of a method for preparing a jujube extract provided in this application. Detailed Implementation

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0032] Technical Concept: The relevant technologies for preparing jujube extract suffer from numerous prominent problems. The core reasons lie in unreasonable process design, insufficient synergy among various stages, and a failure to consider extraction efficiency, product quality, and industrial suitability. Traditional preparation processes often employ alcoholic solution extraction, high-temperature cooking, or high-temperature concentration. The high-temperature and high-pressure environment easily damages heat-sensitive nutrients and flavor compounds in jujubes. The introduction of organic solvents not only causes environmental pollution but also results in solvent residues in the extract, limiting the product's application in the food and tobacco industries. Some improved processes attempt to recover flavor compounds using freeze-drying and macroporous resin adsorption technologies. However, freeze-drying equipment is costly and energy-intensive, hindering large-scale industrial production. Furthermore, macroporous resin adsorption still requires alcohol elution, failing to completely resolve the solvent residue problem. In addition, simple physical crushing is insufficient to fully disrupt the jujube cell walls, leading to incomplete dissolution of active ingredients. The failure to effectively combine soaking pretreatment with enzymatic hydrolysis further exacerbates nutrient loss and flavor degradation, making it impossible to simultaneously improve extraction efficiency, product quality, and environmental friendliness.

[0033] To address the aforementioned technical challenges, this technical solution employs a multi-step, synergistic process, combining targeted technical measures to resolve each pain point. First, it utilizes a synergistic effect of soaking and softening with grinding and enzymatic extraction. Soaking and softening effectively softens the jujube's tissue structure, creating favorable conditions for subsequent enzymatic hydrolysis. Enzymatic hydrolysis specifically breaks down pectin, cellulose, and other components in the jujube cell walls, gently and efficiently releasing intracellular active ingredients and flavor substances. Compared to traditional high-temperature processes and simple physical crushing, this significantly reduces nutrient loss and improves extraction efficiency. Second, the entire extraction process uses pure water, eliminating the introduction of any organic solvents. This avoids solvent residues and environmental pollution from the source, while better preserving active ingredients such as cyclic adenosine monophosphate (cAMP) and vitamin C in the jujube, aligning with green and environmentally friendly production principles. Furthermore, aroma compounds in the solid residue and filtrate are recovered through vacuum drying and reduced-pressure concentration, respectively, reducing flavor loss. Aromatic water is purified by ceramic membrane filtration and concentrated using a tea tree oil-modified chitosan reverse osmosis membrane. The permeability and antibacterial properties of tea tree oil enhance the membrane's processing efficiency and antibacterial performance, while the biocompatibility of chitosan ensures the product's environmental friendliness. Finally, the finished product is blended to achieve a balance of nutrition and flavor. The entire process requires minimal equipment investment, consumes little energy, and is easy to operate. The steps work synergistically, solving problems such as solvent residue, flavor loss, and low extraction efficiency in existing technologies, while also meeting the needs of large-scale industrial production.

[0034] Example 1: This example provides a method for preparing jujube extract, including the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into a pulp to obtain red date pulp. The mass ratio of jujubes to deionized water was 1:6, and the soaking and softening time was 18 hours. The pulverization and grinding process was carried out using a colloid mill, and the fineness of the resulting jujube pulp was controlled to be able to pass through a 50-mesh sieve. The colloid mill model was JM-L50, the grinding speed was 2800 r / min, and the grinding time was 15 minutes.

[0035] S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a slightly acidic range, add enzyme solution and perform enzymatic hydrolysis at a constant temperature, followed by enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. The weakly acidic range was pH 6.5; the isothermal enzymatic hydrolysis conditions were 48℃ for 2 hours using an enzyme solution with a mass percentage of 0.03%; the enzyme inactivation treatment conditions were 85℃ for 1 hour; the enzyme solution was 0.03 wt% pectinase; the alkali solution used to adjust the pH was a 5% sodium hydroxide solution; the enzymatic hydrolysis process was carried out in a sealed reactor with a stirring rate of 120 r / min.

[0036] S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate. The filtration operation was carried out using a plate and frame filter press, with a filtration pressure of 0.3 MPa and a filtration time of 30 minutes.

[0037] S4. Residue Aroma Recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. The set vacuum and temperature conditions are: vacuum 1 mbar, temperature 55℃; refrigerant temperature for condensation recovery is 0℃; and a flat plate heat exchanger with a heat exchange area of ​​2 m² is selected as the condenser. 2 The refrigerant is an aqueous solution of ethylene glycol.

[0038] S5. Primary Concentration and Aroma Recovery of Filtrate: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. The vacuum conditions are 50 mbar and 45°C; the temperature of the refrigerant recovered by condensation is 0°C; a tubular heat exchanger is used as the condenser, and the length of the heat exchange tube is 5 m; the vacuum concentration is stopped when the soluble solids content of the system reaches 75%.

[0039] S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B. The modified chitosan reverse osmosis membrane is prepared as follows: tea tree oil is uniformly sprayed onto the surface of the chitosan reverse osmosis membrane with spraying parameters of 80 mm spraying distance and 60 mm / s spraying rate; after the tea tree oil completely covers the membrane surface, ozone with a concentration of 10 mg / L is introduced for sterilization treatment for 0.5 h; after sterilization, laser irradiation is used for drying treatment with laser power of 250 W, treatment temperature of 80 ℃, and irradiation time of 0.5 h; after drying, the membrane is left to stand at room temperature for 12 h to obtain the modified chitosan reverse osmosis membrane.

[0040] The ceramic membrane used in the ceramic membrane filtration has a pore size of 0.1 μm and an operating pressure of 4 bar; the modified chitosan reverse osmosis membrane concentration has an operating pressure of 20 bar; the cross-flow rate of the ceramic membrane filtration is 3 m / s, and the feed water flow rate of the reverse osmosis membrane concentration is 50 L / h.

[0041] S7. Finished Product Preparation: Mix jujube extract A and jujube extract B in a certain proportion to obtain the final jujube extract. The mass ratio of jujube extract A to jujube extract B is 1:2. The mixing process is carried out in a mixing tank at a stirring rate of 150 r / min for 20 min. After mixing, the mixture is pasteurized at a temperature of 85℃ for 15 min, and then filled to obtain the finished product.

[0042] Example 2: This example provides a method for preparing jujube extract, including the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into a pulp to obtain red date pulp. The mass ratio of jujubes to deionized water was 1:8, and the soaking and softening time was 24 hours. The pulverization and grinding process was carried out using a homogenizer, and the fineness of the resulting jujube pulp was controlled to be able to pass through a 40-mesh sieve. The homogenizer model was GJJ-50, the homogenization pressure was 30MPa, and the homogenization was performed twice.

[0043] S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a slightly acidic range, add enzyme solution and perform enzymatic hydrolysis at a constant temperature, followed by enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. The weakly acidic range is pH 6.0; the isothermal enzymatic hydrolysis conditions are 45℃ and 3h reaction with 0.02% enzyme solution; the temperature-induced enzyme inactivation treatment conditions are 90℃ and maintained for 0.5h; the enzyme solution is cellulase; the alkaline solution used to adjust the pH value is 3% potassium hydroxide solution; the enzymatic hydrolysis process is carried out in a sealed reaction vessel with a stirring rate of 100r / min.

[0044] S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate. The filtration operation was carried out using a plate and frame filter press, with a filtration pressure of 0.25 MPa and a filtration time of 25 minutes.

[0045] S4. Residue Aroma Recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. The specified vacuum and temperature conditions are: vacuum 2 mbar, temperature 60℃; refrigerant temperature for condensation recovery is 5℃; and a flat-plate heat exchanger with a heat exchange area of ​​1.8 m² is selected as the condenser. 2 The refrigerant is an aqueous solution of ethylene glycol.

[0046] S5. Primary Concentration and Aroma Recovery of Filtrate: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. The vacuum conditions are 45 mbar and 40°C; the temperature of the refrigerant recovered by condensation is 5°C; the condenser is a tubular heat exchanger with a tube length of 4.5 m; the vacuum concentration is stopped when the soluble solids content of the system reaches 60%.

[0047] S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B. The modified chitosan reverse osmosis membrane is prepared as follows: tea tree oil is uniformly sprayed onto the surface of the chitosan reverse osmosis membrane with spraying parameters of 70 mm spraying distance and 50 mm / s spraying rate; after the tea tree oil completely covers the membrane surface, ozone with a concentration of 5 mg / L is introduced for sterilization treatment for 1 hour; after sterilization, laser irradiation is used for drying treatment with laser power of 200 W, treatment temperature of 70℃ and irradiation time of 0.8 hours; after drying, the membrane is left to stand at room temperature for 12 hours to obtain the modified chitosan reverse osmosis membrane.

[0048] The ceramic membrane used in the ceramic membrane filtration has a pore size of 0.05 μm and an operating pressure of 2 bar; the modified chitosan reverse osmosis membrane concentration has an operating pressure of 10 bar; the cross-flow rate of the ceramic membrane filtration is 2.5 m / s, and the feed water flow rate of the reverse osmosis membrane concentration is 40 L / h.

[0049] S7. Finished Product Preparation: Mix jujube extract A and jujube extract B in a certain proportion to obtain the final jujube extract. The mass ratio of jujube extract A to jujube extract B is 1:5. The mixing process is carried out in a mixing tank at a stirring rate of 120 r / min for 25 min. After mixing, the mixture is pasteurized at a temperature of 85℃ for 15 min, and then filled to obtain the finished product.

[0050] Example 3: This example provides a method for preparing jujube extract, including the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into a pulp to obtain red date pulp. The mass ratio of jujubes to deionized water was 1:4, and the soaking and softening time was 12 hours. The pulverization and grinding process was carried out using a colloid mill, and the fineness of the resulting jujube pulp was controlled to be able to pass through a 40-mesh sieve. The colloid mill model was JM-L40, the grinding speed was 2500 r / min, and the grinding time was 10 minutes.

[0051] S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a slightly acidic range, add enzyme solution and perform enzymatic hydrolysis at a constant temperature, followed by enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. The weakly acidic range is pH 5.5; the isothermal enzymatic hydrolysis conditions are 50℃ and 1h reaction with 0.04% enzyme solution; the temperature-induced enzyme inactivation treatment conditions are 87℃ and maintained for 0.8h; the enzyme solution is glycosidase; the alkaline solution used to adjust the pH value is 8% sodium hydroxide solution; the enzymatic hydrolysis process is carried out in a sealed reaction vessel with a stirring rate of 140r / min.

[0052] S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate. The filtration operation was carried out using a plate and frame filter press, with a filtration pressure of 0.35 MPa and a filtration time of 35 minutes.

[0053] S4. Residue Aroma Recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. The specified vacuum and temperature conditions are: vacuum 1.5 mbar, temperature 50℃; refrigerant temperature for condensation recovery is 2℃; and a flat-plate heat exchanger with a heat exchange area of ​​2.2 m² is selected as the condenser. 2 The refrigerant is an aqueous solution of ethylene glycol.

[0054] S5. Primary Concentration and Aroma Recovery of Filtrate: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. The vacuum conditions were 48 mbar and 48°C; the temperature of the refrigerant recovered by condensation was 2°C; a tubular heat exchanger was selected as the condenser, with a heat exchange tube length of 5.5 m; the vacuum concentration was stopped when the soluble solids content of the system reached 85%.

[0055] S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B. The modified chitosan reverse osmosis membrane is prepared as follows: tea tree oil is uniformly sprayed onto the surface of the chitosan reverse osmosis membrane with spraying parameters of 90 mm spraying distance and 70 mm / s spraying rate; after the tea tree oil completely covers the membrane surface, ozone with a concentration of 15 mg / L is introduced for sterilization treatment for 0.2 h; after sterilization, laser irradiation is used for drying treatment with laser power of 300 W, treatment temperature of 90 ℃ and irradiation time of 0.2 h; after drying, the membrane is left to stand at room temperature for 12 h to obtain the modified chitosan reverse osmosis membrane.

[0056] The ceramic membrane used in the ceramic membrane filtration has a pore size of 0.2 μm and an operating pressure of 6 bar; the modified chitosan reverse osmosis membrane concentration operates at a pressure of 30 bar; the cross-flow rate of the ceramic membrane filtration is 3.5 m / s, and the feed water flow rate of the reverse osmosis membrane concentration is 60 L / h.

[0057] S7. Finished Product Preparation: Mix jujube extract A and jujube extract B in a certain proportion to obtain the final jujube extract. The mass ratio of jujube extract A to jujube extract B is 1:3. The mixing process is carried out in a mixing tank at a stirring rate of 180 r / min for 15 min. After mixing, the mixture is pasteurized at a temperature of 85℃ for 15 min, and then filled to obtain the finished product.

[0058] In this embodiment, the extraction rate of jujube extract A was 59.2%, and the extraction rate of jujube extract B was 8.6%.

[0059] Example 4: This example provides a method for preparing jujube extract, including the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into a pulp to obtain red date pulp. The mass ratio of jujubes to deionized water was 1:5, and the soaking and softening time was 20 hours. The pulverization and grinding process was carried out using a homogenizer, and the fineness of the resulting jujube pulp was controlled to be able to pass through a 50-mesh sieve. The homogenizer model was GJJ-60, the homogenization pressure was 35MPa, and the homogenization was performed once.

[0060] S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a slightly acidic range, add enzyme solution and perform enzymatic hydrolysis at a constant temperature, followed by enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. The weakly acidic range was pH 6.2; the isothermal enzymatic hydrolysis conditions were 47℃ and 2.5h of reaction with an enzyme solution containing 0.025% by mass; the enzyme inactivation treatment conditions were 88℃ and maintained for 0.6h; the enzyme solution was pectinase; the alkali solution used to adjust the pH was a 6% potassium hydroxide solution; the enzymatic hydrolysis process was carried out in a sealed reactor with a stirring rate of 130r / min.

[0061] S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate. The filtration operation was carried out using a plate and frame filter press, with a filtration pressure of 0.32 MPa and a filtration time of 28 minutes.

[0062] S4. Residue Aroma Recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. The specified vacuum and temperature conditions are: vacuum 1.2 mbar, temperature 58℃; refrigerant temperature for condensation recovery is 3℃; and a flat-plate heat exchanger with a heat exchange area of ​​2.0 m² is used as the condenser. 2 The refrigerant is an aqueous solution of ethylene glycol.

[0063] S5. Primary Concentration and Aroma Recovery of Filtrate: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. The vacuum conditions were 47 mbar and 43°C; the temperature of the refrigerant recovered by condensation was 3°C; a tubular heat exchanger was selected as the condenser, with a heat exchange tube length of 5.0 m; the vacuum concentration was stopped when the soluble solids content of the system reached 70%.

[0064] S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B. The modified chitosan reverse osmosis membrane is prepared as follows: tea tree oil is uniformly sprayed onto the surface of the chitosan reverse osmosis membrane with spraying parameters of 78 mm spraying distance and 58 mm / s spraying rate; after the tea tree oil completely covers the membrane surface, ozone with a concentration of 12 mg / L is introduced for sterilization treatment for 0.4 h; after sterilization, laser irradiation is used for drying treatment with laser power of 260 W, treatment temperature of 78 °C and irradiation time of 0.4 h; after drying, the membrane is left to stand at room temperature for 12 h to obtain the modified chitosan reverse osmosis membrane.

[0065] The ceramic membrane used in the ceramic membrane filtration has a pore size of 0.12 μm and an operating pressure of 4.5 bar; the modified chitosan reverse osmosis membrane concentration has an operating pressure of 22 bar; the cross-flow rate of the ceramic membrane filtration is 3.2 m / s, and the feed water flow rate of the reverse osmosis membrane concentration is 52 L / h.

[0066] S7. Finished Product Preparation: Mix jujube extract A and jujube extract B in a certain proportion to obtain the final jujube extract. The mass ratio of jujube extract A to jujube extract B is 1:4. The mixing process is carried out in a mixing tank at a stirring rate of 160 r / min for 18 min. After mixing, the mixture is pasteurized at a temperature of 85℃ for 15 min, and then filled to obtain the finished product.

[0067] Comparative Example 1: The only difference between this comparative example and Example 1 is that the enzymatic hydrolysis and enzyme inactivation treatment are omitted in step S2. The jujube pulp obtained in step S1 is directly adjusted to pH 6.5 and then proceeded to step S3 for solid-liquid separation.

[0068] Comparative Example 2: The only difference between this comparative example and Example 1 is that the soaking and softening and colloid mill grinding treatment in step S1 are cancelled. Instead, pitted red dates and deionized water are mixed at a mass ratio of 1:6 and extracted under high pressure in a pressure tank at 120°C and 5 bar for 30 minutes. The enzymatic hydrolysis and enzyme inactivation treatment in step S2 are not performed. The process proceeds directly to solid-liquid separation in step S3.

[0069] Comparative Example 3: The only difference between this comparative example and Example 1 is that the vacuum drying treatment at 55°C and 1mbar in step S4 is cancelled. Instead, the solid residue is subjected to ultra-low temperature freezing extraction at -80°C and 0.01 torr for 12 hours, and the melted liquid of the ice crystals condensed in the cold trap is collected as jujube aromatic water.

[0070] Comparative Example 4: In step S6, the ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration were cancelled. Instead, the combined jujube aromatic water was treated with a macroporous resin chromatography column with a wastewater to macroporous resin mass ratio of 40:1. The mixture was circulated twice and eluted with 95% edible alcohol. The eluent was collected as jujube extract B.

[0071] Comparative Example 5: The only difference between this comparative example and Example 1 is that the chitosan reverse osmosis membrane is not modified in step S6, and the unmodified chitosan reverse osmosis membrane is used directly to concentrate the aromatic water filtered by the ceramic membrane.

[0072] Experiment 1: Determination of total soluble solids content and yield of extracts A, B, and total extract. Referring to GB / T12143-2008 "General Analytical Methods for Beverages" and GB / T8302-2013 "Tea Sampling Methods", the total mass of jujubes used in the preparation process of Examples 1-4 and Comparative Examples 1-5 was accurately recorded. Jujube extract A collected after step S5 was weighed in a pre-dried weighing bottle. Jujube extract B collected after step S6 was also weighed in a pre-dried weighing bottle. Then, 10g of the final jujube extract samples prepared in each example and comparative example were accurately weighed and placed in evaporating dishes pre-dried to constant weight. The evaporating dishes were then placed in a 105°C container. Dry the samples in a constant temperature drying oven until constant weight. After removal, cool them to room temperature in a desiccator and weigh them. Calculate the total soluble solids content by the ratio of the mass of the residue after drying to the mass of the sample. Calculate the extraction rate of extract A by dividing the mass of jujube extract A by the total mass of raw jujubes × 100%. Calculate the extraction rate of extract B by dividing the mass of jujube extract B by the total mass of raw jujubes × 100%. Calculate the total yield of the extracts by dividing the mass of extract A by the total mass of extract B by the total mass of raw jujubes × 100%. Record the total soluble solids content, extraction rate of extract A, extraction rate of extract B, and total yield for all samples.

[0073] Experiment 2: Determination of the content of jujube flavor ketone, a characteristic flavor compound of jujube Referring to GB / T23778-2009 "Determination of Volatile Flavor Components in Fruit Products by Gas Chromatography-Mass Spectrometry", 5g of each of the final jujube extract samples prepared in Examples 1-4 and Comparative Examples 1-5 were weighed and placed in 20mL headspace vials. 10mL of saturated anhydrous sodium sulfate solution was added to each headspace vial and the vials were immediately sealed. The sealed headspace vials were placed in a 60℃ constant temperature water bath for 30min to equilibrate. The sample vapor was injected into the gas chromatograph-mass spectrometer using headspace injection. The chromatographic column was set to an HP5MS capillary column, and the column temperature program was as follows: initial temperature 40℃, held for 5min, then increased to 200℃ at a rate of 5℃ / min and held for 10min. Helium was used as the carrier gas, and the flow rate was set to 1mL / min. An electron impact ion source was used as the mass spectrometer detector, and the ion source temperature was set to 230℃. The jujube flavor ketone content in the samples was determined by comparing with the characteristic ion peaks of the jujube flavor ketone standard. The jujube flavor ketone content in the samples was calculated using the external standard method. The jujube flavor ketone content values ​​of all samples were recorded and compared.

[0074] Experiment 3: Determination of Residual Organic Solvents Referring to GB5009.262-2016 "National Food Safety Standard - Determination of Solvent Residues in Food", 2g of each of the final jujube extract samples prepared in Examples 1-4 and Comparative Examples 1-5 were weighed and placed in 20mL headspace vials. 5mL of N,N-dimethylformamide was added to each headspace vial to fully dissolve the sample, and the vials were immediately sealed. The sealed headspace vials were placed in an 80℃ constant temperature water bath for 30min to equilibrate. The sample vapor was injected into the gas chromatograph using headspace injection. The chromatographic column was a DB-WAX capillary column, and the column temperature program was as follows: initial temperature 40℃, held for 5min, then increased to 150℃ at a rate of 10℃ / min and held for 5min. The detector was a flame ionization detector, and the detector temperature was set to 250℃. The carrier gas was nitrogen, and the flow rate was set to 1mL / min. The qualitative analysis was performed by comparing the retention time of the ethanol standard, and the residual amount of organic solvents such as ethanol in the sample was calculated using the external standard method.

[0075] Table 1: Summary Table of Experimental Data for Performance Testing of Jujube Extract

[0076] As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, enzymatic hydrolysis and enzyme inactivation are key steps in the preparation of jujube extract. Examples 1-3 all involve enzymatic hydrolysis of jujube pulp, which can destroy the cell wall structure of jujube, promote the dissolution of active ingredients and the release of flavor substances. However, if this step is omitted, the cell wall of jujube cannot be effectively destroyed, making it difficult for the active ingredients to dissolve fully and inhibiting the release of flavor substances, thus affecting the relevant properties of the product. This also demonstrates the important role of the enzymatic hydrolysis step in the entire preparation process.

[0077] Combining Examples 1-3 and Comparative Example 2 with Table 1, it can be seen that there is a synergistic effect between soaking and softening, grinding and pulping, and enzymatic extraction. In Examples 1-3, soaking and softening fully softens the jujube tissue, and then grinding and pulping breaks the jujubes to a suitable fineness, providing favorable conditions for subsequent enzymatic extraction, allowing the enzymatic hydrolysis to play a more complete role. However, after using high temperature and high pressure extraction and eliminating the above steps, not only is it impossible to achieve the gentle and complete dissolution of effective components, but it also destroys some heat-sensitive flavor substances. At the same time, the lack of the assistance of the enzymatic hydrolysis step further affects the product performance, indicating the importance of the synergistic effect of gentle pretreatment and enzymatic hydrolysis in the preparation process.

[0078] Combining Examples 1-3 and Comparative Example 3 with Table 1, it can be seen that the vacuum drying aroma extraction process plays a significant role in the recovery of aroma substances from jujubes. Examples 1-3 use vacuum drying to process solid residues, which can volatilize the residual aroma substances in the residues under mild conditions and recover them through condensation, thus preserving the natural flavor of jujubes to the greatest extent. However, after using ultra-low temperature freezing extraction, the recovery efficiency of aroma substances will be affected, and the flavor components in the residues cannot be fully recovered. This also shows that the vacuum drying process is more suitable for the aroma recovery of jujube residues and can better cooperate with subsequent processes to improve the relevant performance of the product.

[0079] As can be seen from Examples 1-3 and Comparative Example 4, and Table 1, the membrane-integrated concentration process consisting of ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration is the key to effectively concentrating jujube aromatic water and ensuring product purity. Examples 1-3, through this membrane-integrated process, can effectively retain flavor substances and active ingredients in the aromatic water while avoiding the introduction of organic solvents. However, by using a macroporous resin chromatography column combined with alcohol elution, not only will organic solvents be introduced, but the retention of flavor substances and the retention of active ingredients will also be affected, thus impacting product performance. This demonstrates the advantages and importance of the membrane-integrated concentration process in the preparation process.

[0080] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Table 1, it can be seen that the modification treatment of chitosan reverse osmosis membranes can significantly improve the membrane's performance. Examples 1-3, through modification steps of tea tree oil spraying, ozone sterilization, and laser drying, improved the permeation flux and retention performance of the reverse osmosis membranes, enabling more effective concentration of aromatic water filtered by ceramic membranes and fully retaining its effective components and flavor substances. However, when using unmodified chitosan reverse osmosis membranes, the membrane's retention effect and permeation performance decrease, failing to fully exert its concentration function and thus affecting the performance of related products. This indicates that the membrane modification step is a key factor in improving the concentration effect.

[0081] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing jujube extract, characterized in that: Includes the following steps: S1. Raw material pretreatment: The washed red dates are mixed with deionized water and soaked to soften them. Then, the softened red dates are pitted and crushed into pulp to obtain red date pulp. S2. Enzymatic extraction: Adjust the pH of the jujube pulp to a weakly acidic range, add enzyme solution for constant temperature enzymatic hydrolysis, and then perform enzyme inactivation treatment by heating to obtain the enzymatic hydrolysate. S3. Solid-liquid separation: The enzymatic hydrolysate is filtered to separate the solid residue from the filtrate; S4. Residue aroma recovery: The solid residue is vacuum dried under set vacuum and temperature conditions, and the jujube aroma water recovered by condensation during the drying process is collected. S5. Primary concentration of filtrate and aroma recovery: The filtrate is concentrated under reduced pressure to obtain jujube extract A, and the jujube aromatic water recovered by condensation during the concentration process is collected simultaneously. S6. Membrane-integrated concentration of aromatic water: Combine the jujube aromatic water collected in steps S4 and S5, and sequentially perform ceramic membrane filtration and modified chitosan reverse osmosis membrane concentration treatment to obtain jujube extract B; wherein, the modified chitosan reverse osmosis membrane is prepared by steps including tea tree oil spraying, ozone sterilization and laser drying. S7. Finished product preparation: Mix the jujube extract A and the jujube extract B in a certain proportion to obtain the final jujube extract.

2. The method for preparing jujube extract according to claim 1, characterized in that: In step S1, the mass ratio of the red dates to deionized water is 1:4 to 1:8, and the soaking and softening time is 12h to 24h.

3. The method for preparing jujube extract according to claim 1, characterized in that: In step S1, the pulverizing and grinding process is carried out using a colloid mill or homogenizer, and the fineness of the resulting jujube pulp is controlled to be able to pass through a 40-50 mesh sieve.

4. The method for preparing jujube extract according to claim 1, characterized in that: In step S2, the weak acid range is pH 5.5 to 6.5; the isothermal enzymatic hydrolysis conditions are: reacting with an enzyme solution of 0.02% to 0.04% by mass at 45℃ to 50℃ for 1h to 3h; the conditions for the temperature-induced enzyme inactivation treatment are: maintaining at 85℃ to 90℃ for 0.5h to 1h.

5. The method for preparing a jujube extract according to claim 1, characterized in that: In step S2, the enzyme solution contains at least one of pectinase, cellulase and glycosidase; the alkaline solution used to adjust the pH value is a sodium hydroxide solution or potassium hydroxide solution with a mass concentration of 3% to 8%.

6. The method for preparing a jujube extract according to claim 1, characterized in that: In step S4, the set vacuum and temperature conditions are: vacuum degree 1 mbar to 2 mbar, temperature 50°C to 60°C; in step S5, the decompression conditions are: vacuum degree 45 mbar to 50 mbar, temperature 40°C to 50°C.

7. The method for preparing jujube extract according to claim 1, characterized in that: The refrigerant temperature recovered in step S4 and the refrigerant temperature recovered in step S5 are both 0°C to 5°C.

8. The method for preparing jujube extract according to claim 1, characterized in that: In step S6, the ceramic membrane used for ceramic membrane filtration has a pore size of 0.05 μm to 0.2 μm and an operating pressure of 2 bar to 6 bar; the modified chitosan reverse osmosis membrane concentration operates at a pressure of 10 bar to 30 bar.

9. The method for preparing jujube extract according to claim 1, characterized in that: In step S6, the ozone concentration for ozone sterilization is 5 mg / L to 15 mg / L, and the treatment time is 0.2 h to 1 h; the laser power for laser drying is 200 W to 300 W, the treatment temperature is 70 °C to 90 °C, and the irradiation time is 0.2 h to 0.8 h; the spraying distance for tea tree oil is 70 mm to 90 mm, and the spraying rate is 50 mm / s to 70 mm / s.

10. The method for preparing a jujube extract according to claim 1, characterized in that: In step S5, the vacuum concentration is stopped when the soluble solids content of the system reaches 60% to 85%, and jujube extract A is obtained; in step S7, the mixing mass ratio of jujube extract A and jujube extract B is 1:2 to 1:5.

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