Wheat polar lipid nano-encapsulated powder and a preparation method thereof

Abstract

This disclosure relates to the field of supercritical fluid technology, specifically to a wheat polar lipid nanoparticle-encapsulated powder and its preparation method, comprising the following steps: S1, dissolving wheat polar lipids and a carrier in an organic solvent to obtain a mixture; S2, pressurizing the reaction vessel to supercritical pressure, then depressurizing, repeating this process several times to create a low-oxygen environment with controlled oxygen volume concentration; S3, introducing CO2, increasing the pressure and temperature to a supercritical state to establish a supercritical CO2 environment, then atomizing the mixture and introducing it into the supercritical CO2 environment, utilizing the antisolvent effect of the supercritical CO2 environment to co-precipitate the wheat polar lipids and the carrier, forming microspheres with a core-shell structure; S4, after co-precipitation, depressurizing using a dynamic gradient depressurization method to inhibit microsphere aggregation and structural damage, thereby obtaining wheat polar lipid nanoparticle-encapsulated powder, achieving the preparation of wheat polar lipid nanoparticle-encapsulated powder with high encapsulation efficiency, low porosity, narrow particle size distribution, and excellent antioxidant stability.

Description

Technical Field

[0001] This disclosure relates to the field of supercritical fluid technology, and more specifically, to a wheat polar lipid nanoparticle-encapsulated powder and its preparation method. Background Technology

[0002] Wheat polar lipids are complex mixtures extracted from wheat germ or bran, rich in active ingredients such as ceramides, glycolipids, and phospholipids. They possess dual functions: oral administration to promote skin hydration and topical application to repair the stratum corneum barrier, showing broad application prospects in oral beauty foods and topical cosmetics. However, wheat polar lipids face the following challenges in commercial applications: firstly, poor stability, exhibiting clumping, hardening, and rancid odor upon storage at room temperature or higher temperatures, requiring refrigeration; secondly, insufficient water dispersibility, making it difficult to prepare uniform and stable end products.

[0003] To address the aforementioned issues, those skilled in the art have attempted to employ encapsulation technologies, with common methods including spray drying, liposomes, cyclodextrin inclusion complexation, melt extrusion, and physical adsorption. However, spray drying operates at high temperatures, easily leading to the decomposition of heat-sensitive components, and its porous wall material fails to effectively inhibit oxidation. Liposomes exhibit unstable encapsulation rates, resulting in significant leakage during storage and potentially introducing toxic organic solvent residues. Cyclodextrin inclusion complexes have low loading capacities, making it difficult to encapsulate complex lipid mixtures. Melt extrusion temperatures are excessively high, causing lipid oxidation. Physical adsorption lacks physical barriers, leading to rapid oxidation and short storage time. Therefore, existing technologies struggle to simultaneously meet the comprehensive requirements of wheat polar lipids for stability, water dispersibility, and safety.

[0004] Supercritical carbon dioxide technology, due to its advantages such as mild operation, high diffusion coefficient, low surface tension, and green, residue-free operation, has been explored for the preparation of lipid nanoparticles. Existing technology discloses a method for preparing lipid nanoparticles by supercritical carbon dioxide swelling solution crystallization. This method produces a wet suspension, which is inconvenient to store and transport, and the presence of oxygen during the process makes it unsuitable for processing easily oxidized lipids. Existing technology also discloses a method for microencapsulating natural ingredients using supercritical carbon dioxide spray drying. This method requires the pre-formation of a microemulsion, is complex, and results in microcapsules with relatively large particle sizes and insufficient shell density. Existing literature does not disclose a dry powder preparation route combining hypoxia-pressure-decompression displacement, supercritical antisolvent co-precipitation, and protective dynamic depressurization for wheat polar lipids. Nor has it established the correlation between oxygen concentration, porosity, particle size distribution, and 90-day ceramide retention rate. Current technologies are all based on liposome or emulsion-like wet self-assembly systems, which generally suffer from problems such as unstable encapsulation, easy leakage during storage, and the need for preservation in aqueous or semi-solid form. They do not address the preparation of core-shell structured nanoparticles from wheat polar lipids under anaerobic conditions, nor can they simultaneously meet the comprehensive requirements for antioxidant stability, water dispersibility, and convenient storage and transportation. Summary of the Invention

[0005] The purpose of this disclosure is to provide a wheat polar lipid nano-encapsulated powder and its preparation method, which solves the technical problem that the insufficient shell density of the encapsulated powder prepared by the prior art leads to poor antioxidant stability.

[0006] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0007] According to one aspect of this disclosure, a method for preparing wheat polar lipid nano-encapsulated powder is provided, comprising the following steps: S1, wheat polar lipids and carrier are dissolved in an organic solvent to obtain a mixture; S2, pressurize the reaction vessel to supercritical pressure, then depressurize, repeat several times to create a low-oxygen environment with controlled oxygen volume concentration; S3, CO2 is introduced, and the pressure and temperature are increased to the supercritical state to establish a supercritical CO2 environment. Then, the mixture is atomized and introduced into the supercritical CO2 environment. The antisolvent effect of the supercritical CO2 environment is used to co-precipitate wheat polar lipids with the carrier to form composite microspheres with core-shell structure or adjustable shell structure. After co-precipitation in S4, a dynamic gradient depressurization method was used to depressurize the powder, thereby inhibiting microsphere aggregation and structural damage, and obtaining wheat polar lipid nano-encapsulated powder.

[0008] On the other hand, a wheat polar lipid nano-encapsulated powder is provided, prepared according to the preparation method of the wheat polar lipid nano-encapsulated powder described in one aspect, wherein the particle size D of the obtained encapsulated powder is... 90 ≤5μm, polydispersity index (PDI) ≤0.3, lipid loading ≥25%, encapsulation efficiency ≥90%, shell porosity ≤7%.

[0009] As can be seen from the above technical solutions, the exemplary embodiments disclosed herein possess at least the following advantages and positive effects: On the one hand, by repeatedly pressurizing the reaction vessel to supercritical pressure and then depressurizing it, and repeating this process several times to replace the oxygen in the vessel, a low-oxygen processing environment with controlled oxygen volume concentration is formed. This solves the technical problem of oxidation and rancidity of highly unsaturated lipids caused by the presence of oxygen in existing supercritical crystallization technologies, thereby achieving the effect of inhibiting lipid oxidation from the source and improving the storage stability of the product.

[0010] On the other hand, by using a dynamic gradient depressurization method after co-precipitation, i.e., depressurizing and holding in stages or depressurizing slowly and uniformly, the microsphere structure damage and agglomeration caused by rapid CO2 expansion due to rapid depressurization in the prior art are avoided. This results in encapsulated powder with a core-shell structure, a low-porosity shell, and a narrow particle size distribution, achieving a balance between high encapsulation rate and long-lasting antioxidant properties. As a result, the product does not clump, has no rancid odor, and retains ≥88% of the effective ingredients after being stored at 50°C for 90 days.

[0011] In summary, this technical solution significantly improves the antioxidant stability, water dispersibility, and shelf life of wheat polar lipids through a low-oxygen processing environment and a protective depressurization and decompression method.

[0012] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 This is a schematic diagram of the preparation method of wheat polar lipid nano-encapsulated powder according to the embodiments of this disclosure; Figure 2 This is a schematic diagram of the preparation method of the mixture described in step S1 of the present disclosure. Figure 3 This is a schematic diagram of the preparation method in step S2 of the present disclosure. Figure 4 This is a schematic diagram of the composite microsphere preparation method described in step S3 of the present invention. Figure 5 This is a schematic diagram of the preparation method of wheat polar lipid nano-encapsulated powder described in step S4 of the present invention. Detailed Implementation

[0014] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0015] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, steps, etc., can be employed. In other instances, well-known methods, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0016] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0017] This invention provides a method for preparing wheat polar lipid nanoparticle-encapsulated powder. Specifically, the invention involves repeatedly introducing CO2 into a reaction vessel, pressurizing it to supercritical pressure, and then depressurizing. This process is repeated several times to replace oxygen within the vessel, creating a low-oxygen processing environment with controlled oxygen volume concentration. Then, a mixture of wheat polar lipids and a carrier is atomized and introduced into the supercritical CO2 environment. The antisolvent effect of supercritical CO2 facilitates rapid co-precipitation of the two components, forming microspheres with a core-shell structure or an adjustable shell structure. After co-precipitation, a dynamic gradient depressurization method is used to depressurize, inhibiting microsphere aggregation and structural damage. This method solves the technical problems of oxidation and rancidity of highly unsaturated lipids due to the presence of oxygen and microsphere structural damage caused by rapid depressurization in existing supercritical crystallization techniques. It achieves the preparation of wheat polar lipid nanoparticle-encapsulated powder with high encapsulation efficiency, low porosity, narrow particle size distribution, and excellent antioxidant stability. The technical solution is described in detail below with reference to specific embodiments.

[0018] In one implementation, such as Figure 1 As shown, a method for preparing wheat polar lipid nano-encapsulated powder includes the following steps: S1, wheat polar lipids and carrier are dissolved in an organic solvent to obtain a mixture.

[0019] This step primarily provides a method for preparing a mixture. Specifically, it involves adding wheat polar lipids and a carrier to an organic solvent in a certain proportion, heating and stirring to fully dissolve the solids, and then filtering and degassing to form a clear mixture. Wheat polar lipids are complex mixtures extracted from wheat germ or bran, rich in active ingredients such as ceramides, glycolipids, and phospholipids, and have broad application prospects in oral beauty foods and topical cosmetics. The carrier is a lipid carrier, which can simultaneously precipitate with wheat polar lipids in a supercritical CO2 environment and form a dense shell. The technical problem solved by this step is to provide a homogeneous mixture free of undissolved particles and bubbles, providing a stable material basis for subsequent supercritical coprecipitation.

[0020] like Figure 2 As shown in S1.1, wheat polar lipids and carrier are added to an organic solvent at a mass ratio of 1:4 to 4:1, and stirred at 200 to 600 r / min for 30 to 60 minutes at 20 to 40°C. The organic solvent is ethanol, ethyl acetate or acetone, and the carrier is a lipid carrier.

[0021] In this step, stirring ensures the complete dissolution of wheat polar lipids and the carrier. The temperature is controlled between 20 and 40°C to guarantee dissolution efficiency while preventing the decomposition of heat-sensitive components due to high temperatures. The stirring speed is 200–600 rpm to ensure uniform mixing. The mass ratio can be adjusted within the range of 1:4 to 4:1 to obtain different encapsulation efficiencies and shell thicknesses.

[0022] S1.2, the dissolved mixture is filtered through a 200-mesh sieve to remove undissolved particles, and the filtered filtrate is defoamed under a vacuum of -0.08 to -0.1 MPa for 15 to 30 minutes to obtain a mixture with a mass concentration of 1 to 20%.

[0023] Filtration removes a very small amount of undissolved large particles, preventing clogging of the atomizing device. Vacuum degassing eliminates tiny bubbles in the solution, preventing uneven nucleation caused by bubbles in the supercritical environment, which would affect the quality of the microspheres. A mass concentration of 1–20% allows for control over the particle size and yield of the final powder.

[0024] S2, pressurize the reaction vessel to supercritical pressure, then depressurize, repeat several times to create a low-oxygen environment with controlled oxygen volume concentration.

[0025] This step aims to repeatedly pressurize and depressurize the reaction vessel to displace oxygen. Since CO2 is denser than air, the pressurization and depressurization process gradually replaces the air inside the vessel with CO2, thereby reducing the oxygen concentration. The technical problem this step addresses is that existing supercritical crystallization technologies do not consider the oxidative rancidity of highly unsaturated lipids caused by the presence of oxygen during processing. By creating a low-oxygen environment with controlled oxygen volume concentration, this step inhibits the free radical oxidation chain reaction at its source.

[0026] like Figure 3 As shown in step S2, CO2 is introduced into the reaction vessel, pressurizing it from atmospheric pressure to supercritical pressure. This pressure is maintained for 1-5 minutes, then released back to atmospheric or subcritical pressure. This process is repeated 1-5 times until the oxygen concentration in the reaction vessel drops below 0.5%. The 1-5 minute pressurization period allows the CO2 to fully mix with the gas in the vessel, after which the mixture is released. The number of repetitions depends on the initial air volume and the vessel volume; typically, it needs to be repeated until the oxygen concentration drops below 0.5%, based on online or sample oxygen measurements. If a single pressurization-depressurization cycle fails to achieve the desired result, the process should be repeated.

[0027] In this embodiment, the operating temperature is strictly controlled within the low-temperature range of 35 to 42°C, which is far below the lipid oxidation temperature threshold. This effectively protects the heat-sensitive ceramides and unsaturated fatty acids in wheat polar lipids, demonstrating the characteristics of the ultra-low temperature SAS process platform for highly unsaturated polar lipids.

[0028] S3, CO2 is introduced, and the pressure and temperature are increased to the supercritical state to establish a supercritical CO2 environment. Then, the mixture is atomized and introduced into the supercritical CO2 environment. The antisolvent effect of supercritical CO2 is used to co-precipitate wheat polar lipids with the carrier to form microspheres with a core-shell structure.

[0029] This step aims to provide the core reaction conditions for supercritical antisolvent coprecipitation. Supercritical CO2 acts as the antisolvent, miscible with the organic solvent but not dissolving the polar lipids and carrier in wheat. When the mixture is atomized and introduced into supercritical CO2, the organic solvent is rapidly extracted, and the solute instantly reaches extremely high supersaturation and precipitates simultaneously. The carrier tends to accumulate on the surface to form an outer shell, while the lipids disperse inside to form core-shell microspheres. The technical problems solved by this step are: the shortcomings of traditional encapsulation techniques such as high-temperature damage to heat-sensitive components during spray drying, poor liposome stability, and low cyclodextrin loading, which are addressed by achieving efficient encapsulation under supercritical, mild conditions and with a high diffusion coefficient.

[0030] like Figure 4 As shown in step S3.1, the reaction vessel is preheated to 35–42°C, and CO2 is introduced until the pressure reaches 8–30 MPa, forming a supercritical CO2 environment. The temperature of 35–42°C is higher than the critical temperature of CO2, and the pressure of 8–30 MPa is higher than the critical pressure, ensuring that the CO2 is in a supercritical state. In this embodiment, the preferred temperature range is 35–42°C, which guarantees supercritical conditions while avoiding lipid softening and adhesion.

[0031] S3.2, the mixture is delivered and atomized at a flow rate of 1–10 mL / min, while the inlet flow rate of CO2 is adjusted to achieve a CO2 to mixture volumetric flow rate ratio of 5–50:1. The flow rate ratio affects the solvent extraction rate and particle size. Under the same conditions, a higher ratio results in faster solvent removal, more intense nucleation, and generally smaller particle size; however, high solids content or high viscosity conditions may offset this refining trend.

[0032] In one embodiment, in step S3.2, when wheat polar lipids comprise multiple components, a multi-feed method is employed, wherein the multi-feed method includes: When wheat polar lipids contain two or more components, the different components are dissolved separately in organic solvents to form multiple independent mixtures, which are then transported separately to a mixing zone before atomization for online mixing. After online mixing, the mixture is atomized and introduced into a supercritical CO2 environment. This method avoids phase separation caused by differences in solubility or precipitation rates of different components, ensuring uniform co-precipitation of all components in the complex lipid mixture.

[0033] S3.3, the atomized droplets are introduced into a supercritical CO2 environment, where the organic solvent in the droplets is rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier are simultaneously precipitated to form microspheres with a core-shell structure.

[0034] In this embodiment, by controlling the pressure, temperature, and the mass ratio of wheat polar lipids to the carrier in the supercritical CO2 environment, the nucleation and growth rates can be regulated, thereby obtaining microspheres with different shell structures. Specifically: when using higher pressure, lower temperature, and a higher mass ratio of wheat polar lipids to the carrier, the system has extremely high supersaturation, the nucleation rate dominates, the carrier rapidly accumulates on the droplet surface to form a dense shell, and the internal lipids are completely encapsulated, resulting in dense-shell microspheres. These microspheres are suitable for scenarios requiring long-term antioxidant protection. When using lower pressure, higher temperature, and a lower mass ratio of wheat polar lipids to the carrier, the supersaturation is relatively low, the nucleation growth rate is relatively enhanced, and the carrier and lipids undergo a certain degree of phase separation during precipitation, forming sponge-like microspheres with porous interiors and thinner shells. These microspheres have a large specific surface area and are suitable for scenarios requiring rapid release or high water dispersibility. By adjusting the above parameters, those skilled in the art can flexibly design the shell structure of the microspheres according to specific application requirements.

[0035] After co-precipitation in S4, a dynamic gradient depressurization method was used to depressurize the powder, thereby inhibiting microsphere aggregation and structural damage, and obtaining wheat polar lipid nano-encapsulated powder.

[0036] This step aims to protect the formed microsphere structure. Rapid depressurization causes the CO2 to expand rapidly, generating strong shear forces that damage the microsphere structure and lead to aggregation. Dynamic gradient depressurization, through staged depressurization and holding or uniform slow depressurization, allows CO2 to escape slowly, maintaining the integrity of the microspheres. The technical problem this step solves is the issue of microsphere structure destruction and aggregation caused by a single rapid depressurization step in existing technologies.

[0037] like Figure 5 As shown in step S4.1, after the mixture from step S3 has been completely introduced, stop feeding the mixture and continue circulating supercritical CO2 for 5–15 minutes to extract residual organic solvents. This step can further remove residual solvents inside the microspheres, reducing solvent residue to a safe level.

[0038] S4.2 employs a dynamic gradient depressurization method, gradually reducing the pressure. After each 1–2 MPa reduction, the pressure is held for 1–3 minutes before continuing depressurization until atmospheric pressure is reached, and the depressurized CO2 is discharged from the reaction vessel. For systems with low to medium solid content, a linear depressurization of 30 seconds is the preferred parameter; for systems with high solid content or high viscosity, staged depressurization combined with short-term pressure holding can be used to balance microsphere integrity and industrial operability.

[0039] In one embodiment, the preparation process also includes a CO2 recycling step: the discharged CO2 is sequentially recycled through a three-stage separator, the pressures of which are 8 MPa, 4 MPa, and 2 MPa, respectively. The separated CO2 is recycled, and the amount of fresh CO2 replenished is less than 5%. Through three-stage depressurization separation, CO2 can be efficiently recovered, reducing operating costs.

[0040] In one embodiment, the preparation process also includes a solvent recovery step: the organic solvent mixture discharged during the preparation process is recovered through a distillation column. By controlling the reflux ratio and the number of trays in the distillation column, the purity of the recovered solvent can reach more than 99.5%. The recovered solvent can be recycled for the preparation of the mixture. The entire process has no waste liquid discharge and meets the requirements of green environmental protection.

[0041] On the other hand, this disclosure provides a wheat polar lipid nanoparticle-encapsulated powder, prepared by the above method. The particle size D of the obtained encapsulated powder is... 90 The powder has a core-shell structure, with a particle size of ≤5μm, a polydispersity index (PDI) of ≤0.3, an encapsulation efficiency of ≥25%, and a shell porosity of ≤5%. After storage at 50℃ for 90 days, it shows no clumping or rancid odor, and retains ≥90% of the content of ceramide as a marker.

[0042] Example 1: In a 100 mL high-pressure reaction vessel, wheat polar lipids and hydrogenated lecithin were added to ethanol at a mass ratio of 2:1, controlling the total solids concentration to 10%. The mixture was stirred at 400 rpm for 45 minutes at 30 °C until the solids were completely dissolved. The dissolved mixture was filtered through a 200-mesh sieve, and the filtrate was degassed under a vacuum of -0.09 MPa for 20 minutes to obtain a clear mixture.

[0043] CO2 was introduced into the reaction vessel, pressurizing it from atmospheric pressure to 15 MPa. This pressure was maintained for 3 minutes, then released back to atmospheric pressure. This process was repeated three times until the oxygen volume concentration inside the reaction vessel decreased to 0.3%. The reaction vessel was then preheated to 38°C, and CO2 was introduced to a pressure of 18 MPa to create a supercritical CO2 environment. The mixture was then delivered and atomized at a flow rate of 5 mL / min, while the CO2 inlet flow rate was adjusted to maintain a CO2 to mixture volumetric flow rate ratio of 20:1. The atomized droplets were then introduced into the supercritical CO2 environment. The organic solvent in the droplets was rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier were simultaneously precipitated, forming dense shell-type microspheres. After the mixture was introduced, the feeding was stopped, and the supercritical CO2 was kept circulating for 10 minutes. The pressure was reduced step by step using a dynamic gradient, and the pressure was maintained for 1 minute after each 1 MPa reduction, and then the pressure was reduced again until atmospheric pressure was reached. The depressurized CO2 was discharged from the reaction vessel. After the pressure in the reaction vessel dropped to atmospheric pressure, the composite microspheres were collected. The collected composite microspheres were vacuum dried at 38°C for 2 hours to obtain wheat polar lipid nano-encapsulated powder.

[0044] Example 2: In a 100 mL high-pressure reaction vessel, wheat polar lipids and soybean lecithin were added to ethanol at a mass ratio of 1:1, controlling the total solids concentration to 15%. The mixture was stirred at 400 rpm for 45 minutes at 30 °C until the solids were completely dissolved. The dissolved mixture was filtered through a 200-mesh sieve, and the filtrate was degassed under a vacuum of -0.09 MPa for 20 minutes to obtain a clear mixture.

[0045] CO2 was introduced into the reaction vessel, pressurizing it from atmospheric pressure to 12 MPa. After maintaining the pressure for 3 minutes, the pressure was released back to atmospheric pressure. This process was repeated 3 times to reduce the oxygen volume concentration in the reaction vessel to 0.3%. The reaction vessel was then preheated to 40°C, and CO2 was introduced to a pressure of 12 MPa to create a supercritical CO2 environment. The mixture was delivered and atomized at a flow rate of 5 mL / min. Simultaneously, the CO2 inlet flow rate was adjusted to achieve a CO2 to mixture volumetric flow rate ratio of 20:1. The atomized droplets were then introduced into a supercritical CO2 environment. The organic solvent in the droplets was rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier were simultaneously precipitated to form microspheres. After the mixture was introduced, the feed was stopped, and the supercritical CO2 was kept circulating for 10 minutes. A dynamic gradient depressurization was used, gradually reducing the pressure. After each 2 MPa reduction, the pressure was maintained for 3 minutes before continuing to decrease until atmospheric pressure was reached. The depressurized CO2 was then discharged from the reaction vessel. After the pressure in the reaction vessel dropped to atmospheric pressure, the composite microspheres were collected. The collected composite microspheres were then vacuum dried at 38 °C for 3 hours to obtain wheat polar lipid nano-encapsulated powder.

[0046] Example 3: In a 100 mL high-pressure reaction vessel, wheat polar lipids and hydrogenated lecithin were added to ethanol at a mass ratio of 1:2, controlling the total solids concentration to 10%. The mixture was stirred at 400 rpm for 45 minutes at 30 °C until the solids were completely dissolved. The dissolved mixture was filtered through a 200-mesh sieve, and the filtrate was degassed under a vacuum of -0.09 MPa for 20 minutes to obtain a clear mixture.

[0047] CO2 was introduced into the reaction vessel, pressurizing it from atmospheric pressure to 10 MPa. This pressure was maintained for 3 minutes, then released back to atmospheric pressure. This process was repeated three times until the oxygen volume concentration inside the reaction vessel decreased to 0.3%. The reaction vessel was then preheated to 50°C, and CO2 was introduced to a pressure of 10 MPa to create a supercritical CO2 environment. The mixture was then delivered and atomized at a flow rate of 5 mL / min, while the CO2 inlet flow rate was adjusted to maintain a CO2 to mixture volumetric flow rate ratio of 20:1. The atomized droplets were then introduced into the supercritical CO2 environment. The organic solvent in the droplets was rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier were simultaneously precipitated, forming porous sponge-like microspheres. After the mixture was introduced, the feeding was stopped, and the supercritical CO2 was kept circulating for 10 minutes. The pressure was reduced step by step using a dynamic gradient, and the pressure was maintained for 1 minute after each 1 MPa reduction, and then the pressure was reduced again until atmospheric pressure was reached. The depressurized CO2 was discharged from the reaction vessel. After the pressure in the reaction vessel dropped to atmospheric pressure, the composite microspheres were collected. The collected composite microspheres were vacuum dried at 38°C for 4 hours to obtain wheat polar lipid nano-encapsulated powder.

[0048] Example 4: In a 100 mL high-pressure reaction vessel, wheat polar lipids and hydrogenated lecithin were added to ethanol at a mass ratio of 2:1, controlling the total solids concentration to 10%. The mixture was stirred at 400 rpm for 45 minutes at 30 °C until the solids were completely dissolved. The dissolved mixture was filtered through a 200-mesh sieve, and the filtrate was degassed under a vacuum of -0.09 MPa for 20 minutes to obtain a clear mixture.

[0049] CO2 was introduced into the reaction vessel, pressurizing it from atmospheric pressure to 15 MPa. This pressure was maintained for 3 minutes, then released back to atmospheric pressure. This process was repeated 5 times until the oxygen volume concentration inside the reaction vessel decreased to 0.1%. The reaction vessel was then preheated to 38°C, and CO2 was introduced to a pressure of 18 MPa to create a supercritical CO2 environment. The mixture was then delivered and atomized at a flow rate of 5 mL / min, while the CO2 inlet flow rate was adjusted to maintain a CO2 to mixture volumetric flow rate ratio of 20:1. The atomized droplets were then introduced into the supercritical CO2 environment. The organic solvent in the droplets was rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier were simultaneously precipitated, forming dense shell-type microspheres. After the mixture was introduced, the feeding was stopped, and the supercritical CO2 was kept circulating for 10 minutes. The pressure was reduced by a dynamic gradient, and the pressure was reduced step by step. After each 2 MPa reduction, the pressure was held for 2 minutes, and then the pressure was reduced again until atmospheric pressure was reached. The depressurized CO2 was discharged from the reaction vessel. After the pressure in the reaction vessel dropped to atmospheric pressure, the composite microspheres were collected. The collected composite microspheres were vacuum dried at 38°C for 3 hours to obtain wheat polar lipid nano-encapsulated powder.

[0050] Example 5: In a 100 mL high-pressure reaction vessel, wheat polar lipids and hydrogenated lecithin were added to ethanol at a mass ratio of 2:1, controlling the total solids concentration to 10%. The mixture was stirred at 400 rpm for 45 minutes at 30 °C until the solids were completely dissolved. The dissolved mixture was filtered through a 200-mesh sieve, and the filtrate was degassed under a vacuum of -0.09 MPa for 20 minutes to obtain a clear mixture.

[0051] CO2 was introduced into the reaction vessel, pressurizing it from atmospheric pressure to 15 MPa. This pressure was maintained for 3 minutes, then released back to atmospheric pressure. This process was repeated three times to reduce the oxygen volume concentration in the reaction vessel to 0.3%. The reaction vessel was then preheated to 38°C, and CO2 was introduced to a pressure of 18 MPa to create a supercritical CO2 environment. The mixture was then delivered and atomized at a flow rate of 5 mL / min, while the CO2 inlet flow rate was adjusted to maintain a CO2 to mixture volumetric flow rate ratio of 20:1. The atomized droplets were then introduced into the supercritical CO2 environment. The organic solvent in the droplets was rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier were simultaneously precipitated, forming microspheres. After the mixture was introduced, the feeding was stopped, and the supercritical CO2 was kept circulating for 10 minutes. The pressure was reduced step by step using a dynamic gradient, and the pressure was maintained for 1 minute after each 1 MPa reduction, and then the pressure was reduced again until atmospheric pressure was reached. The depressurized CO2 was discharged from the reaction vessel. After the pressure in the reaction vessel dropped to atmospheric pressure, the composite microspheres were collected. The collected composite microspheres were vacuum dried at 38°C for 4 hours to obtain wheat polar lipid nano-encapsulated powder.

[0052] Comparative Example 1: The difference from Example 1 is that no deoxygenation operation is performed; that is, the reaction vessel is filled with air, and CO2 is directly introduced to establish a supercritical environment. The remaining operations are the same as in Example 1.

[0053] Comparative Example 2: The difference from Example 1 is that a rapid depressurization method (reducing pressure to atmospheric pressure within 1 second) was used after co-precipitation, instead of a dynamic gradient depressurization. The rest of the operation is the same as in Example 1.

[0054] Comparative Example 3: The difference from Example 1 is that the carrier used is sodium octenyl succinate starch, a polysaccharide carrier. This carrier dissolves poorly in ethanol, resulting in a turbid mixture. After filtration, a large number of undissolved particles clog the nozzle during atomization, preventing the experiment from proceeding normally.

[0055] Comparative Example 4: The difference from Example 1 is that, after co-precipitation, supercritical CO2 circulation extraction of residual solvent is not performed; instead, the pressure is directly reduced. The remaining operations are the same as in Example 1.

[0056] Comparative Example 5: The difference from Example 1 is that the deoxygenation step only involves one pressurization-depressurization cycle, and the oxygen volume concentration in the reaction vessel is 5.2%. The remaining operations are the same as in Example 1.

[0057] Testing methods and performance evaluation: Particle size and particle size distribution: Measured using a laser particle size analyzer (wet method). The dispersion medium was deionized water with a particle refractive index of 1.45. Ultrasonic dispersion was performed for 30 seconds. The particle size distribution was measured using a laser particle size analyzer (wet method). 90 And PDI.

[0058] Encapsulation efficiency determination: The surface oil washing method was used. Accurately weigh W of the encapsulated powder. total Add n-hexane, vortex for 1 minute, centrifuge and collect the supernatant. Repeat three times, combine the supernatants, dry under nitrogen, and reconstitute. HPLC is used to determine the mass M of the free lipids. free Alternatively, total lipids were extracted from the encapsulated powder using ultrasonic extraction, and the total lipid mass (M) was determined by HPLC. total Encapsulation efficiency (%) = (W total - M free ) / W total × 100%.

[0059] Lipid loading determination: Accurately weigh W of the encapsulated powder total Total lipids were extracted by ultrasonication, and the mass (M) of wheat polar lipids was determined by HPLC. lipid Lipid load (%) = M lipid / W total × 100%. Lipid loading reflects the content level of effective ingredients in the powder.

[0060] Shell porosity: The specific surface area of ​​the powder was determined by nitrogen adsorption-desorption (BET) method, and the shell porosity was estimated by combining SEM cross-sectional image analysis.

[0061] Stability test: The powder was dispensed into sealed HDPE bottles and placed in a 50℃ constant temperature and humidity chamber. Samples were taken on days 0, 30, 60, and 90 for sensory evaluation (color, odor, clumping); ceramide content was detected by HPLC; and the content retention rate (%) was calculated as: content on day N / content on day 0 × 100%.

[0062] Table 1: Performance test results of each embodiment and comparative example.

[0063] Table 1 shows that the powders prepared in Examples 1-5 had a particle size D90 of 115-350 nm, a PDI of no more than 0.28, a lipid loading of 25.2%-29.1% (all ≥25%), an encapsulation efficiency of ≥97.9%, a shell porosity of no more than 6.5%, and a ceramide content retention rate of 88.6%-94.1% after storage at 50°C for 90 days. No clumping or rancid odor was observed in any of the samples.

[0064] Comparative Example 1, without deoxygenation, had an initial particle size of 125 nm and an encapsulation efficiency of 27.6%, similar to Example 1. However, after 90 days, the retention rate was only 62.5%, and it exhibited a severe rancid odor and clumping. Compared to Example 1, it can be seen that residual oxygen in the reaction vessel was encapsulated into the microspheres during co-precipitation or adsorbed on the powder surface, accelerating the auto-oxidation chain reaction of unsaturated fatty acids. Repeated pressurization and depressurization to replace air with CO2, reducing the oxygen concentration to below 0.5%, is a necessary condition for inhibiting oxidation at its source.

[0065] Comparative Example 2 employed rapid depressurization, increasing the particle size to 580 nm, raising the PDI to 0.45, decreasing the encapsulation efficiency to 18.3%, and increasing the porosity to 12.5%. SEM revealed microsphere rupture and adhesion. Compared to the 30-second linear depressurization of Example 1, rapid depressurization demonstrates that the rapid expansion of CO2 volume during depressurization generates shear force that disrupts the incompletely solidified microsphere structure. Dynamic gradient depressurization allows CO2 to escape slowly, maintaining pressure balance inside and outside the microspheres, which is a key operation for preserving core-shell integrity and low porosity.

[0066] Comparative Example 3 used a polysaccharide carrier, which dissolved poorly in ethanol. After filtration, the mixture still contained a large number of undissolved particles, clogging the nozzle and preventing proper atomization. This comparison demonstrates that the carrier must be compatible with the selected organic solvent. Phospholipid and synthetic polymer carriers have good solubility in solvents such as ethanol, enabling the formation of homogeneous mixtures, which is a prerequisite for subsequent atomization co-precipitation.

[0067] Comparative Example 4, omitting the co-precipitation CO2 recycling extraction, showed a residual solvent content of 850 ppm in the powder, exceeding the safety limit, and a 90-day retention rate of only 81.5%. Residual solvent may migrate to the microsphere surface during storage, compromising shell density or interacting with lipids to accelerate oxidation. While the recycling extraction step does not directly affect the encapsulation efficiency, it makes a practical contribution to product safety and long-term stability.

[0068] Comparative Example 5 underwent only one pressurization and depressurization cycle, with an oxygen concentration still at 5.2% and a retention rate of 78.6%, but exhibited a slight rancid odor and clumping. Compared to Examples 1 and 4, the number of deoxygenation cycles was negatively correlated with oxygen concentration, and the oxygen concentration needed to be reduced to below 0.5% to effectively inhibit oxidation. These results indicate that deoxygenation requires a sufficient number of repetitions, and a single pressurization and depressurization cycle is insufficient to completely replace the air inside the container.

[0069] In summary, the synergistic effect of a hypoxic environment and dynamic gradient depressurization prevents lipid oxidation during the initial stages of processing and storage, while the latter avoids damage to the microsphere structure due to rapid depressurization. Simultaneously, the solubility of the carrier in organic solvents is fundamental to achieving uniform encapsulation. This disclosed technical solution solves the problems of lipid oxidation and microsphere aggregation and breakage in existing technologies by controlling the processing atmosphere and depressurization rate, resulting in nano-encapsulated powders with uniform particle size, high encapsulation efficiency, dense shells, and excellent antioxidant stability.

[0070] To verify the particle size D of the obtained wheat polar lipid nano-encapsulated powder under process conditions of higher solid concentration (20%) and higher pressure (25 MPa), 90 The particle size can still be stably controlled within 500 nm. Meanwhile, by comparing with Example 1 (low concentration, low pressure), the influence of concentration and pressure on particle size is revealed.

[0071] Example 6: Weigh 37.5 g of wheat polar lipids and 12.5 g of hydrogenated lecithin, and place them in a 2 L glass beaker. Add 200 g of ethyl acetate to prepare a solution with a total mass of approximately 250 g and a mass concentration of approximately 20%. Stir mechanically at 500 r / min for 60 minutes in a 35℃ constant temperature water bath. During stirring, the solids were observed to completely dissolve, and the solution was a pale yellow, transparent liquid with no visible particles. The solution was then filtered through a 200-mesh stainless steel sieve (74 μm pore size) under normal pressure; no residual particles were observed on the filter. The filtrate was transferred to a 1 L suction flask and degassed under a vacuum of -0.095 MPa for 30 minutes. Large bubbles gradually disappeared, and the final solution was free of obvious bubbles.

[0072] After cleaning and drying, the 1 L high-pressure crystallization vessel was sealed. The CO2 cylinder was opened, and the CO2 was liquefied through a cooler (-5℃) and then pressurized to 20 MPa using a constant-speed, constant-pressure pump. The pressure was then introduced into the reactor at a flow rate of approximately 5 L / min, and maintained for 5 minutes. Then, the exhaust valve was opened to release the pressure to atmospheric pressure within 10 seconds. This pressurization-depressurization cycle was repeated four times. After the fourth depressurization, the oxygen concentration was measured at the reactor sampling port using a trace oxygen analyzer (GPR-1200, AII, USA). The reading was 0.22%, meeting the requirements for a low-oxygen environment (<0.5%).

[0073] Close the exhaust valve, set the reactor heating jacket temperature to 40℃, and simultaneously start the CO2 feed at a flow rate of 10 g / min. Control the pressure at 25 MPa (±0.2 MPa) using the back pressure valve. After the temperature stabilizes at 40℃ and the pressure at 25 MPa for 10 minutes, confirm that the CO2 in the reactor is in a supercritical state, with a critical temperature of 31.1℃ and a critical pressure of 7.38 MPa.

[0074] The prepared mixture was poured into a 500 mL storage tank, and the high-pressure metering pump was turned on to deliver it to the atomizing nozzle at a flow rate of 10.0 mL / min. At the same time, the auxiliary CO2 flow path was turned on, and the flow rate was adjusted so that the ratio of the total flow rate of CO2 (main path + auxiliary path) to the volumetric flow rate of the mixture was 50:1.

[0075] The atomized microdroplets enter the reactor. Due to the high miscibility of ethyl acetate in supercritical CO2 at 25 MPa and 40℃, the solvent in the droplets can be extracted in a short time. The solutes (wheat polar lipids and hydrogenated lecithin) instantly reach extremely high supersaturation, resulting in homogeneous nucleation and rapid growth. Because hydrogenated lecithin is amphiphilic, it tends to migrate to the droplet-supercritical interface to form a shell, while the relatively hydrophobic components of the wheat polar lipids are mainly enriched inside. The more polar components, together with the carrier, participate in shell construction, forming core-shell structured microspheres. The co-precipitation process lasts approximately 20 minutes.

[0076] After the mixed solution was fed, the pump was stopped, and pure supercritical CO2 was continuously circulated for extraction for 15 minutes to remove residual ethyl acetate inside the microspheres. During this process, samples were taken from the bottom sampling port of the reactor, and residual solvent was detected by gas chromatography. After 15 minutes, the residual ethyl acetate content decreased to 82 ppm. Dynamic gradient linear depressurization was then employed: the back pressure valve was set to linear depressurization mode, and the pressure was uniformly reduced from 25 MPa to atmospheric pressure within 30 seconds (depressurization rate 0.83 MPa / second). During the depressurization process, CO2 gradually vaporized and carried a small amount of dissolved solvent out of the reactor. After the depressurization was completed, the reactor was opened, and the powder on the inner wall and bottom of the reactor was collected. The powder was placed in a vacuum drying oven and dried at 40℃ and -0.09 MPa for 2 hours to obtain the final product, which weighed 35.2 g, with a yield of 88.0%.

[0077] 10 mg of powder was dispersed in 10 mL of deionized water (containing 0.1% Tween 80), sonicated for 30 seconds, and immediately measured using a laser particle size analyzer. The volume average particle size was D90 = 478 nm (three parallel measurements: 472, 481, 481 nm, RSD = 1.0%), D50 = 215 nm, and D10 = 98 nm. The polydispersity index (PDI) was 0.29 (range 0.28-0.30). The particle size distribution curve was single-peaked and left-skewed (tailing at smaller particle sizes). Scanning electron microscopy (SEM) images (×50,000) showed that the microspheres were spherical with smooth surfaces, and some microspheres showed slight adhesion but were not broken. After three repeated experiments, the encapsulation efficiencies were 90.5%, 91.2%, and 91.3%, with an average of 91.0% and an RSD of 0.5%, indicating stable processing.

[0078] Table 2: Comparative Analysis of Example 6 and Example 1 Particle size D in Examples 1 and 6 90 Independent samples t-test was performed (n=3): Example 1 mean 120 nm, standard deviation 2.5 nm; Example 6 mean 478 nm, standard deviation 4.7 nm; t=118.5, d f=2.2, p<0.001, the difference is extremely significant. This indicates that changes in process parameters have a significant impact on particle size, but the D in Example 6... 90 It still meets the requirement of ≤500 nm.

[0079] The main reasons for the increased particle size are: ① At high concentrations, the solute mass in the droplets increases, resulting in a larger mass of microspheres precipitated from each droplet; ② High solids content increases droplet viscosity and the solute mass per droplet, prolonging the solidification process and promoting particle growth; ③ Higher pressure (25 MPa) and a higher CO2 / solution volume ratio (50:1), while beneficial for enhancing antisolvent action and mass transfer, are insufficient to completely offset the increasing particle size trend caused by high solids content. Increased PDI indicates decreased particle size uniformity, possibly related to slightly uneven atomization at high concentrations. A slight increase in porosity is speculated to be due to the higher solubility of ethyl acetate in supercritical CO2 compared to ethanol, leading to more vigorous extraction and leaving more nanopores in the shell. Despite this, the retention rate still reaches 89.4%, indicating that the antioxidant barrier remains effective at a porosity of 5.8%.

[0080] Example 6 demonstrates that even under harsh conditions of high concentration and high pressure, the obtained wheat polar lipid nano-encapsulated powder exhibits D... 90 =478 nm, PDI=0.29, encapsulation efficiency=91.0%, porosity=5.8%, ceramide retention rate after 90 days=89.4%. This example verifies whether the method can improve the component distribution uniformity of microspheres, thereby improving the encapsulation efficiency and antioxidant stability.

[0081] The multi-feed system was upgraded by adding two independent high-pressure constant-speed and constant-pressure pumps (Pump A and Pump B, flow rate 0.1–20 mL / min), a micro static mixer (SS316L, inner diameter 1.6 mm, length 50 mm, mixing volume 0.1 mL), and a T-connector to the original SF-200 system. After online mixing, the mixture is directly connected to an atomizing nozzle (inner diameter 100 μm).

[0082] Dissolve 50 g of wheat polar lipids in 200 mL of chloroform:methanol (2:1), and load the solution onto a pre-equilibrated NH2 solid-phase extraction column. Load 1 g of solution onto each column, for a total of 50 columns. Elute sequentially as follows: Fraction A (moderately polar, containing ceramides and glycolipids): eluted with chloroform:isopropanol (2:1), rotary evaporation yielded 18.2 g (yield 36.4%). HPLC analysis showed: ceramides 22.5%, glycolipids 68.3%, phospholipids <0.5%, and free fatty acids 0.8%.

[0083] Fraction B (highly polar, containing phospholipids and some glycolipids): eluted with methanol:water (9:1), yielding 14.5 g (yield 29.0%). HPLC analysis revealed: phospholipids 58.2%, glycolipids 30.1%, ceramides 2.1%, and free fatty acids 5.2%. The remaining low-content fractions were recovered for later use. In this example, fractions A and B were used as a multi-feed model to verify the effect of improving component homogeneity.

[0084] Prepare mixture A and mixture B separately: Mixture A: Take 12.0 g of fraction A and 6.0 g of hydrogenated lecithin, and add anhydrous ethanol to a total mass of 180 g. Stir at 30℃ and 400 r / min for 45 minutes until completely dissolved. Filter through a 200-mesh sieve, and degas the filtrate under vacuum at -0.09 MPa for 20 minutes to obtain a clear, pale yellow mixture A with an actual concentration of 9.8%.

[0085] Mixture B: Take 12.0 g of fraction B and 6.0 g of hydrogenated lecithin, and prepare them in the same way to obtain a clear, deep yellow mixture B with an actual concentration of 9.9%.

[0086] Single-feed control group mixture: Take 24 g of ungraded wheat polar lipids and 12 g of hydrogenated lecithin, add anhydrous ethanol to a total mass of 360 g, introduce CO2 into a 1 L reactor and pressurize to 15 MPa, maintain the pressure for 3 minutes, release the pressure to atmospheric pressure, repeat 3 times, and measure the oxygen volume concentration in the reactor to be 0.28%. Heat the reactor to 38℃, introduce CO2 to a pressure of 18 MPa, and stabilize for 15 minutes.

[0087] Dual-feed parameters: Pump A (mixture A) flow rate 2.5 mL / min, Pump B (mixture B) flow rate 2.5 mL / min. The two solutions are combined in a micro static mixer with a total flow rate of 5.0 mL / min and an online mixing time of approximately 1.2 seconds. The auxiliary CO2 flow rate is adjusted to 100 mL / min, with a volume ratio of 20:1 to the total mixture.

[0088] The mixed solution is immediately atomized through an atomizing nozzle, and the atomized droplets enter the reaction vessel. Ethanol is rapidly extracted by supercritical CO2, and all components precipitate simultaneously. The feed time is 72 minutes, and each batch of mixture contains 180 mL.

[0089] Post-processing and depressurization: Pumps A and B were stopped, and supercritical CO2 circulation extraction was maintained for 10 minutes. The residual ethanol content in the powder was measured to be 45 ppm. Dynamic gradient depressurization: The pressure was linearly reduced from 18 MPa to atmospheric pressure within 30 seconds. The powder was collected and vacuum dried at 35°C for 3 hours, yielding 28.3 g of powder.

[0090] Table 3: Results of three repeated experiments between different batches.

[0091] In single-feed systems, ethanol is preferentially extracted from the droplet surface, leading to the instantaneous precipitation of surface phospholipids and the formation of a phosphorus-rich shell. The internal ethanol concentration remains high, while ceramides and glycolipids precipitate with delay, resulting in segregation. Multi-feed systems, through online mixing, force uniform distribution of components within the droplet. When the droplet enters the supercritical environment, the solvent is extracted simultaneously from both the surface and the interior, causing all components to reach supersaturation and precipitate synchronously, eliminating the time difference in fractional precipitation. Therefore, the components are uniformly distributed within the microspheres, and the shell, composed of phospholipids and ceramide / glycolipids, forms a denser physical barrier, achieving an encapsulation efficiency of 90.9%. Furthermore, the 95.9% retention rate demonstrates superior antioxidant stability and is significantly better than the 85.0% retention rate of single-feed systems.

[0092] Example 7 successfully prepared nano-encapsulated powders with highly uniform component distribution using a multi-feed technique. Compared to single-feed, the coefficient of variation for phosphorus and nitrogen distribution in the microsphere cross-section decreased from >12% to <5%, the encapsulation efficiency reached 90.9%, and the ceramide retention rate increased from 85.0% with single-feed to 95.9% after storage at 50°C for 90 days. This method is suitable for natural extracts with complex compositions and large differences in the polarity of their components, providing an effective solution to the problem of fractional precipitation in supercritical antisolvent co-precipitation.

[0093] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0094] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for preparing wheat polar lipid nano-encapsulated powder, characterized in that, Includes the following steps: S1, wheat polar lipids and carrier are dissolved in an organic solvent to obtain a mixture; S2, CO2 is introduced into the reaction vessel, pressurized to supercritical pressure, and then depressurized. This process is repeated several times to create a low-oxygen environment with controlled oxygen volume. S3, CO2 is introduced, and the pressure and temperature are increased to the supercritical state to establish a supercritical CO2 environment. Then, the mixture is atomized and introduced into the supercritical CO2 environment. The antisolvent effect of the supercritical CO2 environment is used to co-precipitate wheat polar lipids with the carrier to form composite microspheres with core-shell structure or adjustable shell structure. S4. After co-precipitation, a dynamic gradient depressurization method was used to depressurize the powder to inhibit microsphere aggregation and structural damage, thus obtaining wheat polar lipid nano-encapsulated powder.

2. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, Step S1 includes: S1.1, wheat polar lipids and carrier are added to an organic solvent at a mass ratio of 1:4-4:1, and stirred at 200-600 r / min for 30-60 minutes at 20-40℃. The organic solvent is ethanol, ethyl acetate or acetone, and the carrier is a lipid carrier. S1.2, filter through a 200-mesh sieve to remove undissolved particles, and degas the filtered liquid under a vacuum of -0.08 to -0.10 MPa for 15-30 minutes to obtain a mixed solution with a mass concentration of 1-20%.

3. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, Step S2 includes: Introduce CO2 into the reaction vessel, pressurize it from atmospheric pressure to supercritical pressure, maintain the pressure for 1-5 minutes, and then depressurize it to atmospheric pressure or subcritical pressure. Repeat the above steps 1-5 times to reduce the oxygen volume concentration in the reaction vessel to below 0.5%.

4. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, Step S3 includes: S3.1, preheat the reaction vessel to 35-60℃, and introduce CO2 until the pressure reaches 8-30MPa to form a supercritical CO2 environment; S3.2, the mixture is delivered and atomized at a flow rate of 1-10 mL / min, while the inlet flow rate of CO2 is adjusted so that the volumetric flow rate ratio of CO2 to the mixture is 5-50:

1. S3.3, the atomized droplets are introduced into a supercritical CO2 environment. The organic solvent in the droplets is rapidly extracted by the supercritical CO2, and wheat polar lipids and the carrier are simultaneously precipitated. By adjusting the pressure, temperature and mass ratio of wheat polar lipids to the carrier in the supercritical CO2 environment, composite microspheres with dense or porous shell structures are obtained.

5. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 4, characterized in that, In step S3.3, if the environmental pressure is 18 MPa, the temperature is 35~42℃, and the mass ratio of wheat polar lipids to carrier is 2:1, then dense shell-type composite microspheres are obtained; if the environmental pressure is 10 MPa, the temperature is 50℃, and the mass ratio of wheat polar lipids to carrier is 1:2, then porous shell-type composite microspheres are obtained.

6. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, In step S1, a hydrophilic modifier is added to the mixture. The hydrophilic modifier is at least one of polysorbate and poloxamer. The amount of hydrophilic modifier added is 0.5-10% of the mass of wheat polar lipids.

7. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, In step S3.2, when wheat polar lipids comprise multiple components, a multi-feed method is adopted, wherein the multi-feed method includes: When wheat polar lipids contain two or more components, the different components are dissolved in organic solvents to form multiple independent mixtures, which are then transported to the mixing area before atomization for online mixing. After online mixing, the mixture is atomized and introduced into a supercritical CO2 environment.

8. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 1, characterized in that, Step S4 includes: S4.1 After the composite microspheres are formed in step S3, stop feeding the mixture and continue to circulate supercritical CO2 for 5-15 minutes to extract the residual organic solvent. S4.2, adopt dynamic gradient depressurization, gradually reduce the pressure, hold the pressure for 1 to 3 minutes after each 1 to 2 MPa reduction, and continue to reduce the pressure until atmospheric pressure is reached, and discharge the depressurized CO2 from the reaction vessel; S4.3 After the pressure in the reaction vessel is reduced to atmospheric pressure, the composite microspheres are collected. The collected composite microspheres are then vacuum dried at 30-40℃ for 2-4 hours to obtain wheat polar lipid nano-encapsulated powder.

9. The method for preparing wheat polar lipid nano-encapsulated powder according to claim 8, characterized in that, Step S4.2 further includes recovering the discharged CO2 by passing it through a three-stage separator, wherein the pressures of the three-stage separator are 8 MPa, 4 MPa and 2 MPa respectively, and the separated CO2 is recycled, with the amount of fresh CO2 replenished being less than 5%.

10. A wheat polar lipid nano-encapsulated powder, prepared according to any one of claims 1-9, characterized in that, The particle size D of the resulting coated powder 90 ≤5μm, polydispersity index (PDI) ≤0.3, encapsulation efficiency ≥25%, shell porosity ≤5%.

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