A core-shell microcapsule loaded with egcg, and a preparation method and application thereof

Abstract

The application discloses a kind of EGCG loaded core-shell microcapsules and its preparation method and application, belong to microcapsule technical field.The preparation method of the application includes the following steps: with navel orange pectin and EGCG as core layer material, corn protein is used as shell layer material, and EGCG loaded core-shell structure microcapsule is prepared using coaxial electrospray technology.EGCG is embedded by pectin and corn protein, not only retains antioxidant, anti-inflammatory and other functional activities, but also provides a solution for its stability to be reduced by easy oxidation, easy degradation by environmental factors in high temperature, neutral and alkaline environment, increases the efficient use of EGCG.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and more specifically to a core-shell microcapsule loaded with EGCG, its preparation method, and its application. Background Technology

[0002] Tea polyphenols are the most abundant and active components of tea, accounting for approximately 15-30% of the dry weight of tea leaves. Among them, epigallocatechin gallate (EGCG) is the most abundant and active water-soluble component. EGCG molecules contain multiple phenolic hydroxyl groups, giving them good antioxidant capabilities and playing important roles in anti-inflammatory, anti-cancer, and cardiovascular disease treatment. However, their chemical structure also makes them easily degraded under high temperature, neutral, and alkaline conditions. Furthermore, the degradation rate increases with increasing temperature, pH, and oxygen concentration, resulting in poor stability and low bioavailability, thus limiting their application in the food and pharmaceutical industries. Therefore, designing different delivery systems to enhance the application value of EGCG is of great significance.

[0003] Currently, microcapsule technology, which uses natural or synthetic polymers as encapsulation materials to coat a core (solid, liquid, or gaseous) substance with a semi-permeable or sealed membrane, is widely used for delivering active substances. Microcapsule encapsulation effectively protects the encapsulated active substance (core material), preventing damage and degradation from external environmental factors; it also significantly reduces gastrointestinal side effects and improves the bioavailability of the active substance. The stability and release properties of microcapsules are highly dependent on the composition of the wall material. Using polysaccharides and proteins as wall materials to encapsulate active ingredients can effectively enhance the protection of the core material.

[0004] Electrospray ionization (ESI) is a method for rapidly preparing microcapsules using high-voltage electrostatic discharge, with broad application prospects in food, medical, and health care fields. ESI can be uniaxial or coaxial, with coaxial ESI capable of producing multilayer microcapsules in a single step. This technology is energy-efficient, operates under mild conditions, and is suitable for encapsulating heat-sensitive substances; the produced microcapsules have a high specific surface area and controllable particle size, with minimal impact on food texture.

[0005] However, polysaccharide-protein microcapsules have rarely been prepared using coaxial electrospray technology as wall materials, both domestically and internationally. Therefore, given the increasing public concern about food and drug safety, providing a novel, green, and efficient method for preparing EGCG-loaded core-shell microcapsules is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a core-shell microcapsule loaded with EGCG, its preparation method, and its application. The purpose of this invention is to overcome the defect of EGCG's easy degradation and inactivation. A novel microcapsule preparation method, namely high-voltage electrostatic spraying, is employed. Two wall materials—grapefruit peel pectin and corn protein—are selected as carrier materials. Grapefruit peel pectin and EGCG are dissolved in an aqueous solution as the core layer solution, and corn protein is dissolved in a certain proportion of ethanol solution as the shell layer solution. Core-shell microcapsules loaded with EGCG are prepared using coaxial electrostatic spraying technology. Encapsulating EGCG with corn protein and pectin effectively avoids its degradation and inactivation under high temperature, neutral, and alkaline environments, increasing its stability and bioavailability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing EGCG-loaded core-shell microcapsules includes the following steps:

[0009] (1) The raw pomelo peel was mixed with citric acid aqueous solution, heated in a water bath and then ultrasonically treated to obtain an extract. The precipitate was removed by centrifugation, the supernatant was precipitated with alcohol, and then freeze-dried to obtain pomelo peel pectin.

[0010] (2) Dissolve grapefruit peel pectin in water and stir magnetically to dissolve it completely. Then add EGCG and stir magnetically again to dissolve grapefruit peel pectin and EGCG completely to obtain the core layer spray solution.

[0011] (3) Mix corn protein with an ethanol aqueous solution and stir magnetically at room temperature to obtain the shell layer to be sprayed;

[0012] (4) Use two syringes to draw up the core layer liquid to be sprayed and the shell layer liquid to be sprayed respectively, and install the two syringes on two constant flow micro-injection pumps of the same model respectively. Connect the two syringes to the coaxial needle through the infusion tube, connect the coaxial needle to the positive terminal of the high voltage power supply, connect the receiving device covered with aluminum foil to the negative terminal of the high voltage power supply, set an appropriate voltage, select a certain receiving distance, set the parameters of the constant flow micro-injection pump, control the speed of the solution sprayed by the syringe, run for a period of time under the set process parameters, and obtain microcapsules on the aluminum foil.

[0013] Furthermore, in step (1), the concentration of the above-mentioned citric acid aqueous solution is 100-500 mg / mL; the water bath heating temperature is 50-90℃; and the ultrasonic power is 500-900 W.

[0014] The beneficial effects of adopting the above-mentioned further technical solutions are: if the citric acid aqueous solution, water bath heating temperature and ultrasonic power are too low, the extraction effect of grapefruit peel pectin will be affected; if the citric acid aqueous solution, water bath heating temperature and ultrasonic power are too high, the grapefruit peel pectin structure will be destroyed.

[0015] Furthermore, in step (1), each gram of raw grapefruit peel is mixed with 20 mL of citric acid aqueous solution.

[0016] Furthermore, in step (2), the concentration of pomelo peel pectin in the above-mentioned core layer spray solution is 40-60 mg / mL, and the concentration of EGCG is 50-250 mg / mL.

[0017] The beneficial effects of adopting the above-mentioned further technical solution are: if the pectin concentration of grapefruit peel is too low, the resulting microcapsules have different microstructure shapes and indentations; if the pectin concentration of grapefruit peel is too high, the resulting microcapsules have larger particle sizes and exhibit adhesion.

[0018] If the EGCG concentration is too low, the EGCG loading rate in the resulting microcapsules will be low; if the EGCG concentration is too high, grapefruit peel pectin and corn protein will not be able to completely cover all EGCG particles, resulting in poor encapsulation and loading effects.

[0019] Furthermore, in step (3), the concentration of the above-mentioned ethanol aqueous solution is 80 wt%, and the concentration of corn protein in the shell spray solution is 45-85 mg / mL.

[0020] The beneficial effects of adopting the above-mentioned further technical solutions are: if the corn protein concentration is too low, it fails to completely encapsulate the core particles, resulting in a low encapsulation rate; if the corn protein concentration is too high, the polymer chains become entangled and stretched during the electrospraying process, and a fibrous network is observed in the microstructure, affecting the encapsulation effect.

[0021] Furthermore, in steps (2) and (3), the stirring rate of each magnetic stirring is 800 r / min, and the stirring time is 15 to 60 min.

[0022] The beneficial effects of adopting the above-mentioned further technical solutions are: if the stirring rate is too low and the stirring time is insufficient, the particles will not be completely dissolved, and the microcapsule encapsulation effect will be poor; if the stirring rate is too high and the stirring time is too long, the particles will be highly entangled, and the resulting microcapsule particle size will be large.

[0023] Furthermore, in step (4), the inner needle of the coaxial needle is 22# and the outer needle is 17#; the voltage is set to 17-25kV; the receiving distance of the receiving device is 8-16cm; the flow rate of the liquid to be sprayed from the core layer is 0.2mL / h, the flow rate of the liquid to be sprayed from the shell layer is 0.5-0.9mL / h; and the running time is 5h.

[0024] The beneficial effects of adopting the above-mentioned further technical solution are: if the spray voltage is too low, the resulting microcapsule structure is relatively loose and has weak resistance to adverse conditions; if the spray voltage is too high, the resulting microcapsule microstructure is irregular in shape.

[0025] If the receiving distance is short, the resulting microcapsule particles will stack, affecting the stability of the microcapsule system; if the receiving distance is long, more microcapsules will be lost, resulting in fewer microcapsules being obtained.

[0026] The present invention also provides a core-shell microcapsule loaded with EGCG prepared by the above method.

[0027] The present invention also provides an application of the above-mentioned EGCG-loaded core-shell microcapsules in the food and pharmaceutical preparation fields.

[0028] The beneficial effects of this invention are:

[0029] (1) The in-field emission scanning electron microscopy results of the core-shell microcapsules loaded with EGCG provided by the present invention show that the prepared microcapsule particles are relatively uniform, basically do not stick together, are well dispersed, and are relatively uniform in size.

[0030] (2) The EGCG-loaded core-shell microcapsules prepared by this invention do not alter the chemical properties of EGCG. By physically encapsulating EGCG, they isolate it from the outside air, effectively overcoming the defects of EGCG degradation and inactivation, and improving the stability of EGCG. At the same time, they have advantages such as good safety, easy degradation, antioxidant and other functional activities, and suitability for mass production. Attached Figure Description

[0031] Figure 1 This is the standard curve of EGCG concentration in this invention.

[0032] Figure 2 This is a scanning electron microscope image of the core-shell microcapsule loaded with EGCG in Example 1 of this invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0035] Example 1

[0036] (1) After removing the pulp from fresh grapefruit, the peel is cut into pieces, dried, and ground into powder. The powder is then passed through a 60-mesh sieve to obtain grapefruit peel powder. 10g of grapefruit peel powder is weighed and mixed with 200mL of 100mg / mL citric acid aqueous solution. The mixture is heated in a 50℃ water bath for 15min and then sonicated at 500W for 15min to obtain an extract. The extract is centrifuged at 9000r / min for 15min, and the supernatant is collected. 1.5 times the volume of 95wt% ethanol aqueous solution is slowly added and mixed, while stirring continuously with a glass rod to produce a flocculent precipitate. The mixture is sealed and left to stand overnight at 4℃. The flocculent material is filtered through a 300-mesh sieve to obtain the precipitate. Another 1.5 times the volume of 95wt% ethanol aqueous solution is added for decolorization. The mixture is stirred evenly, sealed and left to stand at 4℃ for 4h, and then filtered through a 300-mesh sieve to obtain the pectin precipitate. The precipitate is then freeze-dried to obtain grapefruit peel pectin.

[0037] (2) Add grapefruit peel pectin to deionized water and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a grapefruit peel pectin solution with a grapefruit peel pectin concentration of 50 mg / mL; then dissolve EGCG in the grapefruit peel pectin solution and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain the core layer spray solution with a EGCG concentration of 150 mg / mL.

[0038] (3) Add corn protein to an 80wt% ethanol aqueous solution and stir magnetically for 30 min at room temperature at a stirring rate of 800 r / min to obtain the shell layer spray solution, so that the corn protein concentration is 45 mg / mL.

[0039] (4) Use two 10mL syringes to draw up the prepared core layer and shell layer spray solutions respectively, and install the two syringes on two constant flow micro-injection pumps of the same model. Connect the two syringes to coaxial needles through infusion tubes. The inner needle of the coaxial needle is 22# and the outer needle is 17#. Connect the coaxial needle to the positive terminal of the high voltage power supply, and connect the receiving device covered with aluminum foil to the negative terminal of the high voltage power supply. Set the voltage to 17kV, the receiving distance of the receiving device to 8cm, the flow rate of the core layer spray solution to 0.2mL / h, and the flow rate of the shell layer spray solution to 0.5mL / h. Run for 5h under the set process parameters to obtain core-shell microcapsules loaded with EGCG on the aluminum foil.

[0040] Example 2

[0041] (1) After removing the pulp from fresh grapefruit, the peel is cut into pieces, dried, and ground into powder. The powder is then passed through a 60-mesh sieve to obtain grapefruit peel powder. 10g of grapefruit peel powder is weighed and mixed with 200mL of 100mg / mL citric acid aqueous solution. The mixture is heated in a 70℃ water bath for 15min and then sonicated at 700W for 15min to obtain an extract. The extract is centrifuged at 9000r / min for 15min, and the supernatant is collected. 1.5 times the volume of 95wt% ethanol aqueous solution is slowly added and mixed, while stirring continuously with a glass rod to produce a flocculent precipitate. The mixture is sealed and left to stand overnight at 4℃. The flocculent material is filtered through a 300-mesh sieve to obtain the precipitate. Another 1.5 times the volume of 95wt% ethanol aqueous solution is added for decolorization. The mixture is stirred evenly, sealed and left to stand at 4℃ for 4h, and then filtered through a 300-mesh sieve to obtain the pectin precipitate. The precipitate is then freeze-dried to obtain grapefruit peel pectin.

[0042] (2) Add grapefruit peel pectin to deionized water and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a grapefruit peel pectin solution with a grapefruit peel pectin concentration of 55 mg / mL; then dissolve EGCG in the grapefruit peel pectin solution and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a core layer spray solution with a EGCG concentration of 150 mg / mL.

[0043] (3) Add corn protein to an 80wt% ethanol aqueous solution and stir magnetically for 15 min at room temperature at a stirring rate of 800 r / min to obtain the shell layer spray solution, so that the corn protein concentration is 65 mg / mL.

[0044] (4) Use two 10mL syringes to draw up the prepared core layer and shell layer spray solutions respectively, and install the two syringes on two constant flow micro-injection pumps of the same model. Connect the two syringes to coaxial needles through infusion tubes. The inner needle of the coaxial needle is 22# and the outer needle is 17#. Connect the coaxial needle to the positive terminal of the high voltage power supply, and connect the receiving device covered with aluminum foil to the negative terminal of the high voltage power supply. Set the voltage to 21kV, the receiving distance of the receiving device to 12cm, the flow rate of the core layer spray solution to 0.2mL / h, and the flow rate of the shell layer spray solution to 0.8mL / h. Run for 5 hours under the set process parameters to obtain core-shell microcapsules loaded with EGCG on the aluminum foil.

[0045] Example 3

[0046] (1) After removing the pulp from fresh grapefruit, the peel is cut into pieces, dried, and ground into powder. The powder is then passed through a 60-mesh sieve to obtain grapefruit peel powder. 10g of grapefruit peel powder is weighed and mixed with 200mL of 500mg / mL citric acid aqueous solution. The mixture is heated in a 90℃ water bath for 15min and then sonicated at 900W for 15min to obtain an extract. The extract is centrifuged at 9000r / min for 15min, and the supernatant is collected. 1.5 times the volume of 95wt% ethanol aqueous solution is slowly added and mixed, while stirring continuously with a glass rod to produce a flocculent precipitate. The mixture is sealed and left to stand overnight at 4℃. The flocculent material is filtered through a 300-mesh sieve to obtain the precipitate. Another 1.5 times the volume of 95wt% ethanol aqueous solution is added for decolorization. The mixture is stirred evenly, sealed and left to stand at 4℃ for 4h, and then filtered through a 300-mesh sieve to obtain the pectin precipitate. The precipitate is then freeze-dried to obtain grapefruit peel pectin.

[0047] (2) Add grapefruit peel pectin to deionized water and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain grapefruit peel pectin solution with a grapefruit peel pectin concentration of 45 mg / mL; then dissolve EGCG in grapefruit peel pectin solution and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain core layer spray solution with a EGCG concentration of 150 mg / mL.

[0048] (3) Add corn protein to an 80wt% ethanol aqueous solution and stir magnetically for 60 min at room temperature at a stirring rate of 800 r / min to obtain the shell layer spray solution, so that the corn protein concentration is 85 mg / mL.

[0049] (4) Use two 10mL syringes to draw up the prepared core layer and shell layer spray solutions respectively, and install the two syringes on two constant flow micro-injection pumps of the same model. Connect the two syringes to coaxial needles through infusion tubes. The inner needle of the coaxial needle is 22# and the outer needle is 17#. Connect the coaxial needle to the positive terminal of the high voltage power supply, and connect the receiving device covered with aluminum foil to the negative terminal of the high voltage power supply. Set the voltage to 25kV, the receiving distance of the receiving device to 16cm, the flow rate of the core layer spray solution to 0.2mL / h, and the flow rate of the shell layer spray solution to 0.9mL / h. Run for 5h under the set process parameters to obtain core-shell microcapsules loaded with EGCG on the aluminum foil.

[0050] Comparative Example 1

[0051] (1) Add the pectin obtained in step (1) of Example 1 to deionized water, and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a pectin solution with a pectin concentration of 50 mg / mL; then dissolve 1.5 g EGCG in the pectin solution and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min.

[0052] Comparative Example 2

[0053] (1) Add the pectin obtained in step (1) of Example 1 to deionized water, and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a pectin solution with a pectin concentration of 50 mg / mL; then dissolve EGCG in the pectin solution with a EGCG concentration of 150 mg / mL, and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min.

[0054] (2) Add corn protein to an 80wt% ethanol aqueous solution and stir magnetically at room temperature for 1 hour at a stirring rate of 800 r / min to obtain a corn protein solution with a corn protein concentration of 45 mg / mL.

[0055] (3) The solution obtained in step (2) is injected into the solution in step (1) using a syringe. The mixture is stirred evenly at a stirring rate of 800 r / min and then dried using a spray drying device with an inlet temperature of 165℃, an outlet temperature of 70℃, and a flow rate of 3 mL / min to prepare EGCG-loaded core-shell microcapsules.

[0056] Comparative Example 3

[0057] (1) Add the pectin obtained in step (1) of Example 1 to deionized water, and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min to obtain a pectin solution with a concentration of 50 mg / mL; then dissolve EGCG in the pectin solution to make the EGCG concentration 150 mg / mL, and stir magnetically for 1 hour at room temperature with a stirring rate of 800 r / min.

[0058] (2) Add corn protein to an 80wt% ethanol aqueous solution and stir magnetically at room temperature for 1 hour at a stirring rate of 800 r / min to obtain a corn protein solution with a concentration of 45 mg / mL.

[0059] (3) The solution obtained in step (2) is injected into the solution in step (1) using a syringe, stirred evenly at a stirring rate of 800 r / min, and dried at -80℃ for 24 h using a freeze dryer to prepare core-shell microcapsules loaded with EGCG.

[0060] Testing process

[0061] The absorbance of EGCG at 540 nm was measured using a UV spectrophotometer at concentration gradients ranging from 0.5 mg / mL to 10 mg / mL, and a standard curve for EGCG concentration was established. The encapsulation efficiency, loading rate, and retention rate of the EGCG-loaded core-shell microcapsules were calculated using the following formulas:

[0062] Encapsulation efficiency = (Total mass of EGCG in microcapsules - Mass of EGCG on the surface of microcapsules) / Total mass of EGCG in microcapsules × 100%

[0063] Loading rate = (Total mass of EGCG in microcapsules - Mass of EGCG on the surface of microcapsules) / Total mass of microcapsule powder × 100%

[0064] Retention rate = (mass of EGCG before treatment / mass of EGCG after treatment) × 100%

[0065] The total mass of EGCG in the microcapsules was calculated by substituting the absorbance of the solution obtained by dissolving the microcapsules in 60% ethanol at 540 nm into the standard curve; the mass of EGCG on the surface of the microcapsules was calculated by substituting the absorbance of the supernatant obtained by centrifugation in deionized water at 540 nm into the standard curve.

[0066] Table 1. EGCG encapsulation rate and loading rate in Examples 1-3 and Comparative Examples 1-2

[0067] Example 1 96.0±2.1％b 48.9±1.1％b Example 2 100±0.3％a 52.4±0.7％a Example 3 98.5 ± 1.5% AB 51.3±0.6%ab Comparative Example 1 -- -- Comparative Example 2 73.5±1.7％d 19.6±1.9％d Comparative Example 3 81.2±1.2％c 23.7±0.7％c

[0068] As shown in Table 1, compared with Comparative Examples 2 and 3, the EGCG encapsulation rate and loading rate in Examples 1-3 were significantly improved.

[0069] The microcapsules prepared in Examples 1-3 and Comparative Examples 1-3 were placed in ovens at 50℃, 75℃, and 100℃ for 150 min, respectively, and then in ovens at 125℃ and 150℃ for 50 min, respectively. After treatment, samples were taken to determine the EGCG content of both and the EGCG retention rate was calculated to examine the thermal stability of the microcapsules. The results are shown in Table 2 below.

[0070] Table 2 Effect of different treatment temperatures on the retention rate of EGCG microcapsules

[0071]

[0072] As shown in Table 2, the stability of EGCG microcapsules gradually decreases with increasing temperature; however, compared with free EGCG (Comparative Example 1), the stability of EGCG microcapsules in Examples 1-3 and Comparative Examples 2 and 3 is significantly improved; and the thermal stability of Examples 1-3 is higher than that of Comparative Examples 2 and 3, indicating that the thermal stability of EGCG prepared by electrospinning is better than that of spray drying and freeze drying.

[0073] The microcapsules prepared in Examples 1-3 and Comparative Examples 1-2 were placed in aqueous solutions with pH values ​​of 3.0, 5.0, 7.0, 9.0, and 11.0, respectively. After treatment for 150 min, samples were taken and the EGCG content of both was determined. The EGCG retention rate was calculated to examine the pH stability of the microcapsules.

[0074] Table 3 Effect of different pH treatments on the retention rate of EGCG microcapsules

[0075] Table 3 shows that EGCG was relatively stable in solutions with pH 3 and 5. However, as the pH gradually increased, the EGCG retention rate in Comparative Example 1 decreased sharply; after treatment in a solution with pH 11 for 150 min, 40% of the EGCG was lost. In Examples 1-3, the EGCG microcapsules maintained a EGCG retention rate greater than 91% in solutions with pH 7–11, indicating that electrospinning microencapsulation can improve the pH stability of EGCG, and the effect is better than spray drying and freeze drying.

[0076] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing core-shell microcapsules loaded with EGCG, characterized in that, Includes the following steps: (1) The raw pomelo peel was mixed with citric acid aqueous solution, heated in a water bath and then ultrasonically treated to obtain an extract. The precipitate was removed by centrifugation, the supernatant was precipitated with alcohol, and then freeze-dried to obtain pomelo peel pectin. (2) Dissolve grapefruit peel pectin in water and stir magnetically to dissolve it completely. Then add EGCG and stir magnetically again to dissolve grapefruit peel pectin and EGCG completely to obtain the core layer spray solution. (3) Mix corn protein with an ethanol aqueous solution and stir magnetically at room temperature to obtain the shell layer to be sprayed; (4) Use two syringes to draw up the core layer liquid to be sprayed and the shell layer liquid to be sprayed respectively, and install the two syringes on two constant flow micro-injection pumps of the same model respectively. Connect the two syringes to the coaxial needle through the infusion tube, connect the coaxial needle to the positive terminal of the high voltage power supply, connect the receiving device covered with aluminum foil to the negative terminal of the high voltage power supply, set an appropriate voltage, select a certain receiving distance, set the parameters of the constant flow micro-injection pump, control the speed of the solution sprayed by the syringe, run for a period of time under the set process parameters, and obtain microcapsules on the aluminum foil.

2. The method for preparing EGCG-loaded core-shell microcapsules according to claim 1, characterized in that, In step (1), the concentration of the citric acid aqueous solution is 100-500 mg / mL; the water bath heating temperature is 50-90℃; and the ultrasonic power is 500-900 W.

3. The method for preparing EGCG-loaded core-shell microcapsules according to claim 1, characterized in that, In step (2), the concentration of pectin in the core layer to be sprayed is 40-60 mg / mL, and the concentration of EGCG is 50-250 mg / mL.

4. The method for preparing EGCG-loaded core-shell microcapsules according to claim 1, characterized in that, In step (3), the concentration of the ethanol aqueous solution is 80 wt%, and the concentration of corn protein in the shell spray solution is 45-85 mg / mL.

5. The method for preparing EGCG-loaded core-shell microcapsules according to claim 1, characterized in that, In steps (2) and (3), the stirring rate of each magnetic stirring is 800 r / min, and the stirring time is 15 to 60 min.

6. The method for preparing EGCG-loaded core-shell microcapsules according to claim 1, characterized in that, In step (4), the inner needle of the coaxial needle is 22# and the outer needle is 17#; the voltage is set to 17-25kV; the receiving distance of the receiving device is 8-16cm; the flow rate of the liquid to be sprayed from the core layer is 0.2mL / h, and the flow rate of the liquid to be sprayed from the shell layer is 0.5-0.9mL / h; the running time is 5h.

7. A core-shell microcapsule loaded with EGCG prepared by the method of any one of claims 1 to 6.

8. The application of the EGCG-loaded core-shell microcapsule of claim 7 in the food and pharmaceutical preparation fields.

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