Novel microcapsule wall material with slow release function as well as preparation method and application of novel microcapsule wall material

Abstract

The invention discloses a novel microcapsule wall material with a release function, the wall material is divided into an inner-layer wall material and an outer-layer wall material, the inner-layer wall material comprises spirulina protein and natto polypeptide, and the outer-layer wall material comprises gelatin and a cross-linking agent; the invention relates to a preparation method of a novel microcapsule with a slow release function, which comprises the following steps: S1, suspending spirulina protein in a phosphate buffer solution, and stirring at 4 DEG C; then adding glucan into the buffer solution according to a certain proportion, and adjusting the pH value to 8.0 by using NaOH; glycosylated spirulina protein and natto polypeptide are adopted as inner-layer wall materials, gelatin is adopted as outer-layer wall materials, and the gelatin and the inner-layer wall materials are cross-linked through a cross-linking agent phytic acid to jointly act to form the microcapsule. The microcapsule can prolong the preservation time of the core material, has the advantages of slow release in gastric juice and avoidance of direct release so as to protect the core material, is simple and safe in process, and increases the application of the slow release function in the field of microcapsules.

Description

Technical Field

[0001] The invention relates to the technical field of microcapsules, and in particular to a novel microcapsule wall material with a slow-release function, a preparation method and an application thereof. Background Art

[0002] Bioactive ingredients play an important role in the physiological structure of the human body, such as lowering blood pressure, anti-oxidation, and anti-inflammation. However, these active ingredients are easily affected by external factors such as temperature, pH changes, and oxygen, causing them to lose their biological activity. Microencapsulation is a method to protect the core material from the effects of temperature, moisture, and microorganisms, which may otherwise have a harmful effect on the active ingredients inside. In addition, there are also microcapsules that have the property of slowly releasing at the target site in the body under specific conditions. For example, encapsulating probiotics into microcapsules can effectively prevent most probiotics from being destroyed in human gastric juice and losing their activity.

[0003] Spirulina is an algae rich in protein, vitamins, minerals and amino acids. It can be artificially cultivated and produced on a large scale. The protein extracted from Spirulina, also called phycocyanin, has good effects in anti-oxidation, anti-inflammation, anti-radiation, enhancing immunity, inhibiting tyrosinase activity and melanin production. So far, there has been little research on the application of phycocyanin in artificial modification of food. Protein glycosylation is a green modification method. It is a non-enzymatic browning reaction between the carbonyl group of reducing sugar and the amino group of protein. It can be used to modify the protein structure. The modified phycocyanin has a loose molecular structure, a high hydroxyl content and shows anionic characteristics. In addition, it can also improve the solubility, emulsification and foaming properties of protein.

[0004] Natto is a soy product made from beans fermented by Bacillus natto. It has a special and attractive flavor and is a food that is deeply loved by people. Natto contains a variety of functional ingredients such as nattokinase, Vk2, linoleic acid, isoflavones, saponins, Bacillus natto, etc. Recent studies have shown that the fermentation of food by microorganisms and their enzymes can lead to the desired biochemical changes and significant changes in flavor and texture, and improve nutritional and functional properties. Bioactive peptides as the end products of fermentation are increasingly considered to have good health prospects. It is reported that these peptides have antioxidant, antihypertensive, immunostimulatory, antimicrobial and antidiabetic effects. It has also been found in studies that multifunctional peptides from cereal proteins have cationic properties and have properties similar to those of the human multifunctional cationic peptide LL-37. Such as antibacterial, anti-inflammatory, endotoxin neutralization and wound healing activities. Therefore, it is of great significance to apply multifunctional cationic peptides in natto to food, medicine and other industries.

[0005] At present, most of the materials used in the research of microcapsule wall materials are based on traditional raw materials such as sodium alginate, gum arabic, chitosan, etc., which lack innovation; many prepared microcapsules use cross-linking agents such as glutaraldehyde, acetic anhydride, polyphosphates, etc., some of which are not only toxic but also have greatly limited conditions of use; currently, there are relatively few types of microcapsule core materials, basically only one, which limits the application of microcapsules with multiple types of core materials. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the background technology, and to propose a new type of microcapsule wall material with a slow-release function, a preparation method and an application thereof. The present invention uses glycosylated spirulina protein and natto polypeptide as inner wall materials, gelatin as outer wall materials, and gelatin and the inner wall materials are cross-linked by a cross-linking agent phytic acid to form microcapsules. The microcapsules can extend the shelf life of the core material, have the advantages of slow release in gastric juice to avoid direct release and thus protect the core material, and the process is simple and safe, which increases the application of slow-release function in the field of microcapsules.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A novel microcapsule wall material with a slow-release function, the wall material is divided into an inner wall material and an outer wall material, the inner wall material comprises spirulina protein and natto polypeptide, and the outer wall material comprises gelatin and a cross-linking agent.

[0008] Preferably, the Spirulina protein needs to be modified by glycosylation, and the cross-linking agent is phytic acid.

[0009] A method for preparing a novel microcapsule with a sustained-release function, the method comprising the following steps: S1. Suspend the Spirulina protein in phosphate buffer and stir at 4°C; Dextran was then added to the buffer at a certain ratio, and the pH was adjusted to 8.0 with NaOH; The mixture was kept at 4°C for 12 hours, then transferred to a water bath for heating, cooled in an ice bath, and then centrifuged to obtain the supernatant for freeze-drying to obtain glycosylated spirulina protein. S2, dissolving the target mass ratio of glycosylated spirulina protein and natto polypeptide in deionized water, adjusting the pH and slowly stirring to prepare a primary emulsion; S3, filtering the primary emulsion described in step S2 to collect the complex coacervate phase, then adding gelatin solution in proportion, slowly stirring and mixing to adjust the pH, cooling and adding crosslinking agent phytic acid to obtain a secondary emulsion after crosslinking, washing with distilled water and then freeze-drying to obtain the novel microcapsule with sustained release function.

[0010] Preferably, the phosphate buffer in step S1 is a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L; The mass volume ratio of the spirulina protein to the sodium phosphate buffer solution is 1:50; The stirring in step S1 is 2h; The dextran described in step S1 is dextran 20, with a molecular weight of 20,000; The ratio of dextran to buffer in step S1 is 1:1.5; The NaOH concentration in step S1 is 0.1 mol / L; The water bath described in step S1 is heated to 90°C for 30 minutes; The ice water cooling time in step S1 is 10 minutes; The centrifugal speed in step S1 is 6500 r / min and the time is 20 min.

[0011] Preferably, the target mass ratio described in step S2 is 1:5~5:1; and the adjusted pH value is 3.0~4.0.

[0012] Preferably, in step (3), the concentration of the gelatin solution added is 5% to 10% (w / v), the concentration of the cross-linking agent added is 0.1% to 0.5% (w / v), and the pH is adjusted to 8.0 to 9.0.

[0013] Preferably, the preparation method comprises the following steps: S1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 h; Dextran 20000 was then added to the buffer at a ratio of 1:1.5, and the pH was adjusted to 8.0 with 0.1 mol / L NaOH; The mixture was kept at 4°C for 12 hours, then transferred to a 90°C water bath and heated for 30 minutes, and cooled in an ice bath for 10 minutes, and then centrifuged at 6500 r / min for 20 minutes to obtain a supernatant, which was then freeze-dried to obtain glycosylated spirulina protein. S2, dissolving the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 5:1 in deionized water, adjusting the pH and slowly stirring to prepare a primary emulsion; S3. Filter the primary emulsion described in step S2 to collect the complex coacervate phase, add a 10% (w / v) gelatin solution, slowly stir and mix to adjust the pH, cool and add 0.5% (w / v) phytic acid as a cross-linking agent to obtain a secondary emulsion after cross-linking, wash with distilled water and freeze-dry to obtain the novel microcapsule with sustained release function.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses glycosylated spirulina protein and natto polypeptide as polyanions and polycations to form a complex coacervation system. Compared with the prior art, it not only changes the application of traditional wall materials such as sodium alginate, gum arabic, chitosan and other raw materials in microcapsule wall materials, but also the wall materials of the present invention are more practical than traditional wall materials, and may also carry beneficial functions such as anti-oxidation, anti-inflammatory, and immune stimulation.

[0015] 2. The present invention uses gelatin as the outer wall material, glycosylated spirulina protein and natto polypeptide as the inner wall material, and uses phytic acid as a crosslinking agent to crosslink the gelatin and the inner wall material. Phytic acid is negatively charged and can combine with positively charged gelatin through charge adsorption to enhance the stability of the microcapsule structure; and phytic acid and protein (inner wall material) can form a phytic acid protein complex, which can reduce the digestibility of pepsin, thereby delaying the release of the loaded nutrients in the stomach and achieving the function of sustained release.

[0016] 3. Most of the cross-linking agents used in the prior art are glutaraldehyde, acetic anhydride, polyphosphate, etc. The sources of these cross-linking agents are generally chemical synthesis, with many restricted conditions, and have certain toxicity, which is not suitable for food production. The phytic acid used in the present invention is extracted from plants, has applications in food and medicine, and is simple to use, with few restricted conditions, and therefore has good market prospects.

[0017] 4. Currently, many microcapsule wall materials with sustained-release function are being studied, but the glycosylated spirulina protein and natto polypeptide in the present invention have not been used in this field. Therefore, the present invention can not only enrich the application of microcapsule wall material selection, but also has important significance in the research of functional wall materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a process flow chart of microcapsules prepared according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the microcapsule embedding rate obtained in Example 1-3 and Comparative Example 1-2.

[0020] Figure 3 The results of Example 3 and Comparative Example 1 show the effects of different pH values ​​in the human gastrointestinal tract on the release of the microcapsule core material.

[0021] Figure 4 This is a scanning electron microscope image of the microcapsules in Example 3.

[0022] Figure 5 It is the infrared spectrum of the microcapsule wall material composition.

[0023] Figure 6 It is the particle size distribution diagram of microcapsules. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0025] Example 1 The preparation method of the novel microcapsule wall material with sustained release function in this embodiment comprises the following steps: 1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 hours. Then add dextran 20000 to the buffer at a ratio of 1:1.5, and adjust the pH to 8.0 with 0.1 mol / L NaOH. Keep the mixture at 4°C for 12 hours, transfer it to a 90°C water bath, heat it for 30 minutes, cool it in an ice bath for 10 minutes, and then centrifuge it at a speed of 6500r / min for 20 minutes to obtain the supernatant, and then freeze-dry it to obtain the glycosylated spirulina protein.

[0026] 2. Dissolve the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 1:5 in deionized water, adjust the pH and stir slowly to prepare a primary emulsion.

[0027] 3. Filter the primary emulsion to collect the complex coacervate phase, add a 5% (w / v) gelatin solution, slowly stir and mix to adjust the pH, cool and add 0.1% (w / v) phytic acid as a cross-linking agent to obtain a secondary emulsion after cross-linking, wash with distilled water and freeze-dry to obtain the novel microcapsules with sustained release function.

[0028] Example 2 The preparation method of the novel microcapsule wall material with sustained release function in this embodiment comprises the following steps: 1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 hours. Then add dextran 20000 to the buffer at a ratio of 1:1.5, and adjust the pH to 8.0 with 0.1 mol / L NaOH. Keep the mixture at 4°C for 12 hours, transfer it to a 90°C water bath, heat it for 30 minutes, cool it in an ice bath for 10 minutes, and then centrifuge it at a speed of 6500r / min for 20 minutes to obtain the supernatant, and then freeze-dry it to obtain the glycosylated spirulina protein.

[0029] 2. Dissolve the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 1:1 in deionized water, adjust the pH and stir slowly to prepare a primary emulsion.

[0030] 3. Filter the primary emulsion to collect the complex coacervate phase, add a gelatin solution with a concentration of 8% (w / v), slowly stir and mix to adjust the pH, cool and add phytic acid with a concentration of 0.3% (w / v) to obtain a secondary emulsion after cross-linking, wash with distilled water and freeze-dry to obtain the novel microcapsules with sustained release function.

[0031] Example 3 The preparation method of the novel microcapsule wall material with sustained release function in this embodiment comprises the following steps: 1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 hours. Then add dextran 20000 to the buffer at a ratio of 1:1.5, and adjust the pH to 8.0 with 0.1 mol / L NaOH. Keep the mixture at 4°C for 12 hours, transfer it to a 90°C water bath, heat it for 30 minutes, cool it in an ice bath for 10 minutes, and then centrifuge it at a speed of 6500r / min for 20 minutes to obtain the supernatant, and then freeze-dry it to obtain the glycosylated spirulina protein.

[0032] 2. Dissolve the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 5:1 in deionized water, adjust the pH and stir slowly to prepare a primary emulsion.

[0033] 3. Filter the primary emulsion to collect the complex coacervate phase, add a 10% (w / v) gelatin solution, slowly stir and mix to adjust the pH, cool and add 0.5% (w / v) phytic acid as a cross-linking agent to obtain a secondary emulsion after cross-linking, wash with distilled water and freeze-dry to obtain the novel microcapsules with sustained release function.

[0034] Comparative Example 1 This embodiment is set up with embodiment 3 as a control implementation method to serve as a comparative example of embodiment 3.

[0035] 1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 hours. Then add dextran 20000 to the buffer at a ratio of 1:1.5, and adjust the pH to 8.0 with 0.1 mol / L NaOH. Keep the mixture at 4°C for 12 hours, transfer it to a 90°C water bath, heat it for 30 minutes, cool it in an ice bath for 10 minutes, and then centrifuge it at a speed of 6500r / min for 20 minutes to obtain the supernatant, and then freeze-dry it to obtain the glycosylated spirulina protein.

[0036] 2. Dissolve the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 5:1 in deionized water, adjust the pH and slowly stir to obtain a primary emulsion, and then freeze-dry to obtain the microcapsules of Comparative Example 1.

[0037] Comparative Example 2 This embodiment is set up with embodiment 3 as a control implementation method to serve as a comparative example of embodiment 3.

[0038] 1. Add 0.5% (w / v) phytic acid as a cross-linking agent to a 10% (w / v) gelatin solution, adjust the pH, slowly stir and cross-link, and then freeze-dry to obtain microcapsules of Comparative Example 2.

[0039] Example 4 This example uses the embedding rate as an index experiment to evaluate the embedding rates of the microcapsules prepared in Examples 1 to 3 and Comparative Examples 1 to 2. The embedding core material is linseed oil. The specific operation steps are as follows: Determination of oil concentration on the surface of microcapsules: Accurately weigh 2 g of the dried microcapsule product, dissolve it in 20 ml of n-hexane solution, and filter it with a 0.25 μm filter membrane. The filtrate is the oil not coated on the surface. Take a part and centrifuge it at 4000 r / min for 15 min. Take 1.5 ml of the supernatant and put it in a near-infrared sample bottle. The surface oil concentration is measured by the standard curve made by the near-infrared spectrometer.

[0040] Determination of embedded oil concentration in microcapsules: Take the above-mentioned filtered residue and extract it with n-hexane ultrasonically, then use a high-speed dispersing homogenizer to fully break the microcapsules, and then centrifuge it at 4000r / min for 15min, take 1.5ml of the supernatant and put it in a near-infrared sample bottle, and measure the embedded oil concentration through the standard curve made by the near-infrared spectrometer. The embedding rate is calculated as follows: , Where: C1 is the concentration of microcapsule embedded oil; C2 is the concentration of microcapsule surface oil Figure 2 Schematic diagram of microcapsule embedding rate of Examples 1 to 3 and Comparative Examples 1 to 2. It can be seen from the figure that the microcapsule embedding rate formed by Example 3 is the highest, better than Examples 1, 2 and Comparative Examples 1, 2, while Comparative Example 2 cannot be embedded because it cannot form a capsule.

[0041] Example 5 This embodiment uses in vitro simulation of the effect of different pH in the human gastrointestinal tract on the release of microcapsule core material as an indicator experiment. Since comparative example 2 cannot be encapsulated, the sustained-release performance of the microcapsules prepared in Example 3 and comparative example 1 is evaluated. The embedded core material is linseed oil. The specific operation steps are as follows: weigh a certain mass of sample, add 15 mL of 0.1 mol / L HCL, continue for 2 hours, and take a sample every 30 min. Then add 30 mL of an aqueous solution containing 0.13 g NaOH and 0.306 g KH2PO4 to the acidic medium to increase the pH value to 7.4. Similarly, take samples every 30 min until the core material release rate remains roughly unchanged. The released core material is absorbed by n-hexane and measured by an ultraviolet spectrophotometer at a wavelength of 317 nm, and the release rate of the core material is calculated by converting the absorbance value into concentration.

[0042] Figure 3 The figure shows the effect of different pH values ​​in the simulated human gastrointestinal tract on the release of the microcapsule core material in Example 3 and Comparative Example 1. As can be seen from the figure, in the simulated gastric fluid at pH = 1.0, the release rate of the core material of the microcapsules prepared under the conditions of Example 3 is lower than that of Comparative Example 1, and the core material of the microcapsules in Comparative Example 1 is almost completely released; in the simulated intestinal tract at pH = 7.4, the core material of the microcapsules in Comparative Example 1 is basically completely released after only about 30 minutes, while the microcapsules in Example 3 are gradually released completely after 150 minutes. Therefore, it is shown that the microcapsules prepared under the conditions of Example 3 have the advantage of slow release in gastric fluid to avoid direct release and thus protect the core material.

[0043] Example 6 This example uses a scanning electron microscope to evaluate the embedding morphology of the microcapsules prepared in Example 3. The specific steps are as follows: stick the microcapsule sample powder on the SEM stage with conductive glue, spray gold on the sample surface, and after 30 minutes, place the stage in a SEM with an accelerating voltage of 20 kV to observe the image.

[0044] Figure 4 3 is a scanning electron microscope image of the microcapsules in Example 3. Figure 4 It can be seen that the microcapsules are round in appearance, dense in structure with a little adhesion, and no obvious cracks on the outside, which means that the microcapsules have a good protection and retention effect on their core materials.

[0045] Example 7 In this example, Fourier transform infrared spectrometer was used to evaluate the microcapsules prepared in Example 3 to prove that the microcapsules were formed. The specific operation steps are as follows: The chemical structure of the sample was characterized by KBr tableting method. The sample was treated with KBr, that is, 1 mg of sample was weighed, 100 mg of dried KBr powder was added to a mortar and ground into a uniform tablet, and a KBr blank tablet was used as a reference. The core material and microcapsule products were analyzed under the conditions of a detection wavelength range of 400 to 4000 cm-1, a resolution of 4 cm-1, and a number of 32 times. Figure 5 This is the infrared spectrum of the microcapsule wall material components. Figure 5 The analysis showed that the bands at 1648 cm-1 and 1396 cm-1 of glycosylated spirulina protein are asymmetric and symmetric stretching peaks assigned to carboxylate groups, and there is a weak absorption at 1515 cm-1, indicating that the -NH2 bending vibration is weakened, which may be attributed to the covalent bonding of the reducing end of the polysaccharide chain with the amino acid side chain of the protein. In addition, a strong absorption band appeared around 1070 cm-1, which is a typical -CO stretching and -OH deformation absorption. The bending of natto polypeptide at 1651 cm-1 is the amide I band, and the bending at 1577 cm-1 is the amide II band. In the spectrum of microcapsules, new bands appeared at 1242 cm-1 and 1324 cm-1 respectively due to the asymmetric and symmetric stretching of the -COO- group. Therefore, infrared spectroscopy confirms that the carboxylic acid groups of glycosylated spirulina protein and cationic groups such as amino groups of natto polypeptide can form microcapsules through electrostatic interactions.

[0046] Example 8 This example uses a laser particle size analyzer to evaluate the particle size and distribution of the microcapsules prepared in Example 3. The specific operation steps are as follows: The particle size of the microcapsules is observed using a Malvern laser particle size analyzer. The particle size of the microcapsules is measured by wet granulation.

[0047] Figure 6 is the microcapsule particle size distribution diagram. Figure 6 The analysis shows that the particle size distribution of microcapsules is mainly distributed in the regions of 4~120μm and 120~600μm. In these two regions, the distribution of microcapsules is in the form of normal distribution. There are more microcapsules in the region of 120~600μm, which may be due to insufficient stirring during the preparation of microcapsules, resulting in adhesion and agglomeration of microcapsules. After calculation, it can be seen that the average particle size of microcapsules is 97.99μm.

[0048] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A novel microcapsule wall material with sustained release function, characterized in that: The wall material is divided into an inner wall material and an outer wall material, the inner wall material comprises spirulina protein and natto polypeptide, and the outer wall material comprises gelatin and a cross-linking agent.

2. A novel microcapsule wall material with sustained release function according to claim 1, characterized in that: The spirulina protein needs to be modified by glycosylation, and the cross-linking agent is phytic acid.

3. A method for preparing a novel microcapsule with sustained release function, characterized in that: The preparation method comprises the following steps: S1. Suspend the Spirulina protein in phosphate buffer and stir at 4°C; Dextran was then added to the buffer at a certain ratio, and the pH was adjusted to 8.0 with NaOH; The mixture was kept at 4°C for 12 hours, then transferred to a water bath for heating, cooled in an ice bath, and then centrifuged to obtain the supernatant for freeze-drying to obtain glycosylated spirulina protein. S2, dissolving the target mass ratio of glycosylated spirulina protein and natto polypeptide in deionized water, adjusting the pH and slowly stirring to prepare a primary emulsion; S3, filtering the primary emulsion described in step S2 to collect the complex coacervate phase, then adding gelatin solution in proportion, slowly stirring and mixing to adjust the pH, cooling and adding crosslinking agent phytic acid to obtain a secondary emulsion after crosslinking, washing with distilled water and then freeze-drying to obtain the novel microcapsule with sustained release function.

4. The method for preparing a novel microcapsule with sustained release function according to claim 3, characterized in that: The phosphate buffer in step S1 is a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L; The mass volume ratio of the spirulina protein to the sodium phosphate buffer solution is 1:50; The stirring in step S1 is 2h; The dextran described in step S1 is dextran 20, with a molecular weight of 20,000; The ratio of dextran to buffer in step S1 is 1:1.5; The NaOH concentration in step S1 is 0.1 mol / L; The water bath described in step S1 is heated to 90°C for 30 minutes; The ice water cooling time in step S1 is 10 minutes; The centrifugal speed in step S1 is 6500 r / min and the time is 20 min.

5. The method for preparing a novel microcapsule with sustained release function according to claim 3, characterized in that: The target mass ratio described in step S2 is 1:5-5:1; the adjusted pH value is 3.0-4.

0.

6. The method for preparing a novel microcapsule with sustained release function according to claim 3, characterized in that: In the step (3), the concentration of the gelatin solution added is 5% to 10% (w / v), the concentration of the cross-linking agent added is 0.1% to 0.5% (w / v), and the pH is adjusted to 8.0 to 9.

0.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The preparation method comprises the following steps: S1. Suspend the spirulina protein in a sodium phosphate buffer solution with a pH of 8.0 and a concentration of 0.02 mol / L, and stir at 4°C for 2 h. Dextran 20000 was then added to the buffer at a ratio of 1:1.5, and the pH was adjusted to 8.0 with 0.1 mol / L NaOH; The mixture was kept at 4°C for 12 hours, then transferred to a 90°C water bath and heated for 30 minutes, and cooled in an ice bath for 10 minutes, and then centrifuged at 6500 r / min for 20 minutes to obtain a supernatant, which was then freeze-dried to obtain glycosylated spirulina protein. S2, dissolving the glycosylated spirulina protein and natto polypeptide in a target mass ratio of 5:1 in deionized water, adjusting the pH and slowly stirring to prepare a primary emulsion; S3. Filter the primary emulsion described in step S2 to collect the complex coacervate phase, add a 10% (w / v) gelatin solution, slowly stir and mix to adjust the pH, cool and add 0.5% (w / v) phytic acid as a cross-linking agent to obtain a secondary emulsion after cross-linking, wash with distilled water and freeze-dry to obtain the novel microcapsule with sustained release function.

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