High oil load essential oil microcapsule powder and method for preparing the same

Abstract

The application discloses a high-oil-content essential oil microcapsule powder and a preparation method thereof, and belongs to the technical field of microcapsules. The preparation method comprises the following steps: preparing a gelatin water solution, preparing an acacia water solution, preparing an acacia-starch water solution, preparing a chitosan-tannic acid water solution, preparing an emulsion, primary crosslinking, and secondary crosslinking. The essential oil microcapsule powder prepared by the method has high oil content, low surface oil content, excellent slow-release performance, solubility, long-term controlled-release performance and fluidity, and uniform particle size distribution.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, specifically to an essential oil microcapsule powder with high oil loading capacity and its preparation method. Background Technology

[0002] Essential oils are volatile liquid substances derived from plants, extracted through various methods including solvent extraction, distillation, supercritical fluid extraction, ultrasonic extraction, microwave extraction, and pulsed electric field-assisted extraction. Essential oils are rich in phenols, terpenes, esters, alkenes, aldehydes, and ketones, possessing unique aromas. They also exhibit strong antibacterial activity and are commonly used in food preservation and plant pest and disease control. Furthermore, essential oils possess potent pharmacological effects, such as analgesia, anti-inflammation, anti-tumor activity, and local anesthetic effects. However, the volatility of essential oils affects their long-term effectiveness. Therefore, various encapsulation techniques are often used to encapsulate essential oils to enhance their long-term efficacy, such as emulsion technology, liposome technology, and microencapsulation technology.

[0003] When using emulsion technology to encapsulate essential oils, the resulting emulsion system has relatively poor inherent stability, easily leading to flocculation and aggregation, resulting in emulsion demulsification. When using liposome technology to encapsulate essential oils, the presence of the phospholipid layer in the liposomes makes the liposome system susceptible to acid hydrolysis, high shear stress, and high temperatures, leading to liposome membrane dissociation. Microencapsulation technology, which encapsulates solids, liquids, or gases into active materials with continuous films using natural or synthetic polymers, is widely used in the food, textile, cosmetic, agricultural, printing, and pharmaceutical industries as an effective technology for protecting and improving the stability of hydrophobic active substances. Microencapsulation technology overcomes the shortcomings of emulsion and liposome technologies by converting essential oils into powdered oils (i.e., essential oil microcapsule powder), altering the state of the essential oils, thereby reducing the interference of the external environment and improving their storage stability.

[0004] In microencapsulation technology, microcapsule preparation methods can be categorized into physical methods (spray drying, freeze-drying, supercritical fluid methods, and solvent evaporation, etc.), physicochemical methods (composite coagulation and ionogel methods, etc.), and chemical methods (interfacial polymerization and molecular inclusion complexation, etc.). Among these, the composite coagulation method, a physicochemical approach, utilizes two water-soluble polymers as wall materials. Under appropriate conditions, these polymers coagulate from the solution due to charge neutralization, thus encapsulating the core material to form microcapsules. Using the composite coagulation method to prepare microcapsules not only improves the stability of essential oils and ensures slow release, but also exhibits better thermal stability compared to other microcapsule preparation methods, thus attracting considerable attention in recent years.

[0005] The specific reaction process of the composite coagulation method involves mixing the wall material solution with the core material, then adjusting the pH, temperature, and ionic strength of the system to reduce the solubility of the wall material, causing it to precipitate onto the core material. A cross-linking agent is then added for curing, followed by drying to obtain essential oil microcapsule powder. To improve the stability of the system and ensure more uniform particle size of the obtained essential oil microcapsule powder after mixing the wall material solution with the core material, an emulsifier is added. Wall materials used in the composite coagulation method can be classified according to their charge: cationic polymers (chitosan and polyvinylpyrrolidone, etc.), anionic polymers (sodium carboxymethyl cellulose, sodium alginate, and gum arabic, etc.), and amphoteric polymers (gelatin, tyrosine, and albumin, etc.). Currently, commonly used wall material combinations include gelatin-gum arabic, gelatin-sodium alginate, chitosan-sodium alginate, chitosan-sodium carboxymethyl cellulose, chitosan-gum arabic, and gelatin-chitosan. For emulsifiers used in composite coagulation methods, nonionic emulsifiers are commonly used, specifically including monoglycerides and sucrose esters. For crosslinking agents used in composite coagulation methods, commonly used crosslinking agents are chemical crosslinking agents (glutaraldehyde, glyoxal, and formaldehyde, etc.) and biological crosslinking agents (transglutaminase, tannic acid, gallic acid, and citric acid, etc.). Among these, transglutaminase and polyphenolic crosslinking agents (tannic acid and gallic acid, etc.) are non-toxic, have good biocompatibility, are widely available, and are low in cost, thus showing broad application prospects.

[0006] For essential oil microcapsule powders, high oil loading can effectively improve preparation efficiency and reduce production costs. However, currently, most essential oil microcapsule powders on the market have an oil loading of 5-35%, generally below 50%. This is mainly due to the poor emulsifying activity and stability of the wall material, which cannot completely encapsulate the essential oil, resulting in excessively high surface oil content in the prepared essential oil microcapsule powder, making it prone to oxidation and rancidity, thus affecting the stability of the essential oil microcapsule powder. In the composite coagulation method, the two water-soluble polymers in the wall material can have a synergistic effect, thereby improving the emulsifying activity and stability of the wall material, further increasing the oil loading of the prepared essential oil microcapsule powder, and reducing the surface oil content. The oil loading of essential oil microcapsule powder prepared by the composite coagulation method can reach more than 50%, and the surface oil content can be as low as below 5%. However, when preparing essential oil microcapsule powders with high oil loading (oil loading > 50%) using commonly used wall materials, emulsifiers, and bio-crosslinking agents through the composite coagulation method, the following problems exist:

[0007] Q1. The higher the oil loading capacity of essential oil microcapsule powder, the lower the wall material content, the worse the protection of the wall material in the essential oil microcapsule powder, the faster the release rate of essential oil, that is, the worse the sustained-release performance of essential oil microcapsule powder.

[0008] Q2. The higher the oil loading capacity of essential oil microcapsule powder, the stronger the hydrophobicity of the essential oil microcapsule powder and the lower the solubility;

[0009] Q3. Polyphenol crosslinking agents mainly achieve crosslinking through non-covalent interactions such as hydrogen bonding and hydrophobic interactions. However, using only glutamine transaminase or polyphenol crosslinking agents for single crosslinking results in poor long-term controlled-release performance of essential oil microcapsule powders.

[0010] To address the aforementioned issues, common solutions include adjusting the stirring speed to increase the particle size of the essential oil microcapsule powder, thereby improving its sustained-release performance; adding easily absorbent materials, such as polydextrose, to the wall material; and using different cross-linking agents for double cross-linking to improve the long-term controlled-release performance and thermal stability of the essential oil microcapsule powder. However, the stirring speed is related to the particle size and oil content of the essential oil microcapsule powder. Low stirring speeds result in unstable emulsions, while emulsions with high oil content have lower droplet density, making them more prone to floating and agglomerating into microcapsules with large particle sizes and high oil content, leading to a wider particle size distribution in the resulting essential oil microcapsule powder. Adding easily absorbent materials to the wall material increases the moisture content of the essential oil microcapsule powder, reducing its flowability. Furthermore, using different cross-linking agents can affect the solubility of the essential oil microcapsule powder. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides an essential oil microcapsule powder with high oil loading capacity and its preparation method. The prepared essential oil microcapsule powder not only has high oil loading capacity and low surface oil content, but also has excellent sustained-release performance, solubility, long-term controlled-release performance and flowability, and has a uniform particle size distribution.

[0012] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0013] A method for preparing an essential oil microcapsule powder with high oil loading capacity includes the following steps: preparing a gelatin aqueous solution, preparing a gum arabic aqueous solution, preparing a gum arabic-starch aqueous solution, preparing a chitosan-tannic acid aqueous solution, preparing an emulsion, primary crosslinking, and secondary crosslinking;

[0014] The preparation of the gelatin aqueous solution involves stirring water at 50-55°C, slowly adding gelatin to the water, stirring until the gelatin is completely dissolved, and then cooling to room temperature to obtain the gelatin aqueous solution.

[0015] In the preparation of the gelatin aqueous solution, the concentration of gelatin in the gelatin aqueous solution is 30-32g / 3000mL;

[0016] The gelatin should be added 4-5 minutes later.

[0017] To prepare the gum arabic aqueous solution, water is stirred at 45-50°C, gum arabic is slowly added to the water, and the mixture is stirred until the gum arabic is completely dissolved. The solution is then cooled to room temperature to obtain the gum arabic aqueous solution.

[0018] The preparation of the gum arabic aqueous solution involves a gum arabic concentration of 28-30 g / 3000 mL.

[0019] The gum arabic should be added 4-5 minutes later.

[0020] To prepare the gum arabic-starch aqueous solution, the water is stirred at 50-55℃. Gum arabic is added to the water and stirred until it is completely dissolved. Corn starch is added and stirred for 30-60 minutes. The mixture is then transferred to a boiling water bath for gelatinization. During gelatinization, the mixture is stirred for 40-60 minutes and then cooled to room temperature to obtain the gum arabic-starch aqueous solution.

[0021] In the preparation of the gum arabic-starch aqueous solution, the concentration of gum arabic is 1.8-2 g / 300 mL, and the concentration of corn starch is 10-11 g / 300 mL.

[0022] To prepare the chitosan-tannic acid aqueous solution, glacial acetic acid and water are mixed and stirred at room temperature for 5-10 minutes. Chitosan is then added and stirred until completely dissolved to obtain the chitosan-acetic acid aqueous solution. Tannic acid and water are mixed and stirred at room temperature until completely dissolved to obtain the tannic acid aqueous solution. The chitosan-acetic acid aqueous solution and the tannic acid aqueous solution are then mixed and stirred at room temperature for 8-10 hours to obtain the chitosan-tannic acid aqueous solution.

[0023] In the preparation of the chitosan-tannic acid aqueous solution, the ratio of glacial acetic acid, water, and chitosan in the chitosan-acetic acid aqueous solution is 25g:2500mL:12-13g.

[0024] In an aqueous solution of tannic acid, the ratio of tannic acid to water is 24-25g:2500mL.

[0025] The mass ratio of chitosan to tannic acid in the chitosan-acetic acid aqueous solution is 25:24-25.

[0026] The degree of deacetylation of the chitosan is 90%.

[0027] The preparation of the emulsion involves mixing gelatin aqueous solution, gum arabic aqueous solution and gum arabic-starch aqueous solution at 45-50℃ and stirring for 30-60 minutes. Then, essential oil and emulsifier are added and stirred for 3-4 hours. The mixture is then cooled to room temperature and homogenized under high pressure to obtain the emulsion.

[0028] In the preparation of the emulsion, the mass ratio of gelatin in the gelatin aqueous solution, gum arabic in the gum arabic aqueous solution, corn starch in the gum arabic-starch aqueous solution, essential oil, and emulsifier is 30-32:28-30:10-11:64-65:1-1.1.

[0029] The essential oil is one of rose essential oil, sandalwood essential oil, oregano essential oil, and lavender essential oil;

[0030] The essential oils were obtained through commercial channels;

[0031] The emulsifier is Tween-80;

[0032] During the high-pressure homogenization, the high-pressure homogenization pressure is 25-30 MPa, the high-pressure homogenization speed is 10000-12000 r / min, and the high-pressure homogenization time is 2-3 min.

[0033] The first-stage crosslinking involves stirring the emulsion at 40-45°C, adding an aqueous acetic acid solution to adjust the pH to 4-4.5, stirring for 30-40 minutes, cooling to 5-10°C, stirring at 5-10°C for 30-40 minutes, adding an aqueous sodium hydroxide solution to adjust the pH to 5.5-6, heating to 40-45°C, adding transglutaminase, stirring at 40-45°C for 7-8 hours, allowing to stand at 5-10°C for 10-12 hours, filtering, and collecting the filter residue to obtain single-crosslinked microcapsules.

[0034] In the primary cross-linking, the enzyme activity of the transglutaminase is 60 U / g;

[0035] The mass ratio of gelatin to transglutaminase used in the preparation of the emulsion is 30-32:7.5-8;

[0036] The mass concentration of the acetic acid aqueous solution is 10%;

[0037] The molar concentration of the sodium hydroxide aqueous solution is 5 mol / L;

[0038] The secondary crosslinking process involves mixing chitosan-tannic acid aqueous solution and monocrosslinked microcapsules at 40-45℃ and stirring for 30-40 minutes. The mixture is then cooled to 5-10℃ and stirred at 5-10℃ for 30-40 minutes. Sodium hydroxide aqueous solution is added to adjust the pH value to 5.2-5.5, and the mixture is stirred for 30-40 minutes. Tannic acid aqueous solution is added, and the mixture is stirred for 2-3 hours. The mixture is then allowed to stand at 5-10℃ for 10-12 hours, filtered, and the filter residue is freeze-dried to obtain essential oil microcapsule powder.

[0039] In the secondary crosslinking, the ratio of chitosan in the chitosan-tannic acid aqueous solution, gelatin used in the preparation of single-crosslinked microcapsules, and tannic acid aqueous solution is 12-13g:30-32g:100-110mL;

[0040] The molar concentration of the sodium hydroxide aqueous solution is 5 mol / L;

[0041] The mass concentration of the tannic acid aqueous solution is 10%;

[0042] During the freezing process, the freezing temperature is -18°C and the freezing time is 10-12 hours.

[0043] During the freeze-drying process, the freeze-drying temperature is -48℃ and the freeze-drying time is 48-50 hours.

[0044] An essential oil microcapsule powder obtained by the aforementioned preparation method.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] (1) The wall materials of microcapsules mainly include carbohydrates and proteins. Starch and chitosan belong to carbohydrates, while gelatin and gum arabic belong to proteins. Carbohydrate wall materials have good water solubility but poor emulsification ability and poor encapsulation effect. Protein wall materials have poor emulsification performance, but they will lead to poor solubility of microcapsules and high water content. Therefore, this invention uses gum arabic and starch together to prepare a gum arabic-starch aqueous solution. Gum arabic has a highly branched structure and contains carboxyl groups. In the gum arabic-starch aqueous solution, it can reduce the hydrogen bonding between starch molecules. Improving the thermal stability of starch slurry can also improve the smoothness of starch slurry film and enhance its tensile properties. In emulsification, the complex of gum arabic and starch can form a smooth wall film on the surface of emulsion droplets, which plays a certain stabilizing role in the emulsion system, thereby improving particle size uniformity. Moreover, through the complexation effect between gum arabic and starch, the compactness of the wall film of microcapsules can be improved, the permeability of the wall film can be reduced, thereby reducing the surface oil content and improving the yield, encapsulation efficiency, oil loading capacity and fluidity. Due to the strong hydrophilicity of starch, the solubility of microcapsules can also be improved.

[0047] (2) There are intermolecular forces such as hydrogen bonds between chitosan and tannic acid. Therefore, chitosan can be used for the adsorption of tannic acid. In addition, chitosan can also form complex colloidal particles with tannic acid. Therefore, this invention first utilizes the interaction between chitosan and tannic acid to mix chitosan and tannic acid. Tannic acid is adsorbed on the main chain of chitosan to obtain a complex of chitosan and tannic acid. Then, it is mixed with single cross-linked microcapsules. The complex is uniformly adsorbed on the surface of single cross-linked microcapsules through hydrogen bonds. Then, after increasing the pH value, chitosan undergoes deprotonation and hydrophobicity is enhanced, thereby forming a complex colloidal particle layer on the surface of single cross-linked microcapsules. Then, tannic acid is used to cross-link the microcapsules, thereby forming a dense protective layer on the surface of single cross-linked microcapsules to improve the sustained-release performance. At the same time, the advantages of chitosan as a carbohydrate wall material are utilized to improve the solubility of microcapsules. In addition, the interaction between chitosan and tannic acid is utilized to ensure that chitosan can be evenly distributed on the surface of the microcapsule and cross-linked in two stages to improve the cross-linking effect between chitosan and gelatin and gum arabic. At the same time, the ability of chitosan and tannic acid to self-assemble into colloidal particles at high pH values ​​is also utilized. Tannic acid has a high hydroxyl content, thereby improving the sustained-release effect and hydrophilicity of the microcapsules.

[0048] (3) The surface oil content of the essential oil microcapsule powder prepared by the present invention is 3.02-3.21%, the moisture content is 3.05-3.29%, the yield is 85.2-88.0%, the encapsulation rate is 94.1-94.3%, the oil loading is 53.1-55.3%, the sustained release performance and long-term sustained release performance are good, the solubility is 94.87-95.37%, the angle of repose is 39.3-40.7°, the average particle size is 52-57μm, and the particle size polydispersity index is 4.71-5.11. Detailed Implementation

[0049] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0050] Example 1

[0051] This embodiment provides a method for preparing essential oil microcapsule powder with high oil loading capacity, specifically including the following steps:

[0052] S1. Stir 3000mL of water magnetically at 50℃ at a speed of 400r / min. Slowly add 30g of gelatin to the water over a period of 4min. Stir magnetically until the gelatin is completely dissolved. Cool the water to room temperature to obtain a gelatin aqueous solution.

[0053] S2. Stir 3000mL of water magnetically at 45℃ at a speed of 400r / min. Slowly add 28g of gum arabic to the water over a period of 4min. Stir magnetically until the gum arabic is completely dissolved. Cool to room temperature to obtain an aqueous solution of gum arabic.

[0054] S3. At 50℃, 300mL of water was magnetically stirred at a speed of 400r / min. 1.8g of gum arabic was added to the water and magnetically stirred until the gum arabic was completely dissolved. 10g of corn starch was added and magnetically stirred for 30min. The mixture was then transferred to a boiling water bath for gelatinization. During gelatinization, the mixture was stirred at a speed of 300r / min for 40min. The mixture was then cooled to room temperature to obtain a gum arabic-starch aqueous solution.

[0055] S4. At room temperature, 25g of glacial acetic acid and 2500mL of water were mixed and magnetically stirred at a speed of 400r / min for 5min. Then, 12g of chitosan was added and magnetically stirred until completely dissolved to obtain a chitosan-acetic acid aqueous solution. At room temperature, 24g of tannic acid and 2500mL of water were mixed and magnetically stirred until completely dissolved to obtain a tannic acid aqueous solution. At room temperature, all the obtained chitosan-acetic acid aqueous solution and all the obtained tannic acid aqueous solution were mixed and magnetically stirred at a speed of 200r / min for 8h to obtain a chitosan-tannic acid aqueous solution.

[0056] The degree of deacetylation of the chitosan is 90%.

[0057] S5. At 45℃, all the gelatin aqueous solution obtained in S1, all the gum arabic aqueous solution obtained in S2, and all the gum arabic-starch aqueous solution obtained in S3 were mixed and magnetically stirred at a speed of 400 r / min for 30 min. 64 g of essential oil and 1.1 g of Tween-80 were added and magnetically stirred for 3 h. The mixture was then cooled to room temperature and homogenized under high pressure at a pressure of 25 MPa and a speed of 10000 r / min for 3 min to obtain an emulsion.

[0058] The essential oil is rose essential oil;

[0059] The essential oils were obtained through commercial channels;

[0060] S6. At 40℃, all the emulsion obtained in S5 was magnetically stirred at a speed of 450 r / min. A 10% acetic acid aqueous solution was added to adjust the pH to 4. The mixture was magnetically stirred for 30 min, cooled to 5℃, and magnetically stirred for 30 min at 5℃. A 5 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 5.5. The mixture was heated to 40℃, and 7.5 g of transglutaminase was added. The mixture was magnetically stirred at 40℃ for 7 h, allowed to stand at 5℃ for 10 h, filtered, and the residue was collected to obtain single cross-linked microcapsules.

[0061] The enzyme activity of the transglutaminase is 60 U / g;

[0062] S7. At 40℃, all the chitosan-tannic acid aqueous solution obtained in S4 and all the monocrosslinked microcapsules obtained in S6 were mixed and magnetically stirred at a speed of 450 r / min for 30 min. The mixture was then cooled to 5℃ and magnetically stirred at 5℃ for 30 min. A sodium hydroxide aqueous solution with a molar concentration of 5 mol / L was added to adjust the pH value to 5.2. The mixture was then magnetically stirred for another 30 min. 100 mL of a tannic acid aqueous solution with a mass concentration of 10% was added and stirred for 2 h. The mixture was allowed to stand at 5℃ for 10 h, filtered, and the filter residue was subjected to freeze treatment at a temperature of -18℃ for 10 h. Finally, it was freeze-dried at a temperature of -48℃ for 48 h to obtain essential oil microcapsule powder.

[0063] This embodiment also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0064] Example 2

[0065] This embodiment provides a method for preparing essential oil microcapsule powder with high oil loading capacity, specifically including the following steps:

[0066] S1. Stir 3000mL of water magnetically at 55℃ at a speed of 600r / min. Slowly add 32g of gelatin to the water over a period of 5min. Stir magnetically until the gelatin is completely dissolved. Cool to room temperature to obtain a gelatin aqueous solution.

[0067] S2. Stir 3000mL of water magnetically at 50℃ at a speed of 600r / min. Slowly add 30g of gum arabic to the water over a period of 5min. Stir magnetically until the gum arabic is completely dissolved. Cool to room temperature to obtain a gum arabic aqueous solution.

[0068] S3. At 55℃, 300mL of water was magnetically stirred at a speed of 600r / min. 2g of gum arabic was added to the water and magnetically stirred until the gum arabic was completely dissolved. 11g of corn starch was added and magnetically stirred for 60min. The mixture was then transferred to a boiling water bath for gelatinization. During gelatinization, the mixture was stirred at a speed of 400r / min for 60min. The mixture was then cooled to room temperature to obtain a gum arabic-starch aqueous solution.

[0069] S4. At room temperature, 25g of glacial acetic acid and 2500mL of water were mixed and magnetically stirred at 600r / min for 10min. Then, 13g of chitosan was added and magnetically stirred until completely dissolved to obtain a chitosan-acetic acid aqueous solution. At room temperature, 25g of tannic acid and 2500mL of water were mixed and magnetically stirred until completely dissolved to obtain a tannic acid aqueous solution. At room temperature, all the obtained chitosan-acetic acid aqueous solution and all the obtained tannic acid aqueous solution were mixed and magnetically stirred at 300r / min for 10h to obtain a chitosan-tannic acid aqueous solution.

[0070] The degree of deacetylation of the chitosan is 90%.

[0071] S5. At 50℃, all the gelatin aqueous solution obtained in S1, all the gum arabic aqueous solution obtained in S2, and all the gum arabic-starch aqueous solution obtained in S3 were mixed and magnetically stirred at a speed of 600 r / min for 60 min. 65 g of essential oil and 1 g of Tween-80 were added and magnetically stirred for 4 h. The mixture was then cooled to room temperature and homogenized under high pressure at a pressure of 30 MPa and a speed of 12000 r / min for 2 min to obtain an emulsion.

[0072] The essential oil is rose essential oil;

[0073] The essential oils were obtained through commercial channels;

[0074] S6. At 45℃, all the emulsion obtained in S5 was magnetically stirred at a speed of 500 r / min. A 10% acetic acid aqueous solution was added to adjust the pH to 4.5. The mixture was magnetically stirred for 40 min, cooled to 10℃, and magnetically stirred at 10℃ for 40 min. A 5 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 6. The mixture was heated to 45℃, 8 g of transglutaminase was added, and the mixture was magnetically stirred at 45℃ for 8 h. The mixture was then allowed to stand at 10℃ for 12 h, filtered, and the residue was collected to obtain single cross-linked microcapsules.

[0075] The enzyme activity of the transglutaminase is 60 U / g;

[0076] S7. At 45℃, all the chitosan-tannic acid aqueous solution obtained in S4 and all the monocrosslinked microcapsules obtained in S6 were mixed and magnetically stirred at a speed of 500 r / min for 40 min. The mixture was then cooled to 10℃ and magnetically stirred at 10℃ for 40 min. A sodium hydroxide aqueous solution with a molar concentration of 5 mol / L was added to adjust the pH value to 5.5. The mixture was then magnetically stirred for another 40 min. 110 mL of a tannic acid aqueous solution with a mass concentration of 10% was added and stirred for 3 h. The mixture was then allowed to stand at 10℃ for 12 h, filtered, and the filter residue was collected. The residue was then subjected to freeze treatment at a temperature of -18℃ for 12 h. Finally, it was freeze-dried at a temperature of -48℃ for 50 h to obtain essential oil microcapsule powder.

[0077] This embodiment also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0078] Example 3

[0079] This embodiment provides a method for preparing essential oil microcapsule powder with high oil loading capacity. The preparation method is basically the same as that in Example 1, except that the rose essential oil in S5 is replaced with sandalwood essential oil obtained through commercial channels.

[0080] This embodiment also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0081] Example 4

[0082] This embodiment provides a method for preparing essential oil microcapsule powder with high oil loading capacity. The preparation method is basically the same as that in Example 1, except that the rose essential oil in S5 is replaced with oregano essential oil obtained through commercial channels.

[0083] This embodiment also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0084] Example 5

[0085] This embodiment provides a method for preparing essential oil microcapsule powder with high oil loading capacity. The preparation method is basically the same as that in Example 1, except that the rose essential oil in S5 is replaced with lavender essential oil obtained through commercial channels.

[0086] This embodiment also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing essential oil microcapsule powder with high oil loading capacity, which adopts a preparation method that is basically the same as that in Example 1, except that:

[0089] 1. In S2, change 28g of gum arabic to 29.8g of gum arabic;

[0090] 2. Omit S3;

[0091] 3. In S5, the addition of gum arabic-starch aqueous solution is omitted.

[0092] This comparative example also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing essential oil microcapsule powder with high oil loading capacity, which adopts a preparation method that is basically the same as that in Example 1, except that:

[0095] 1. In step S4, omit the addition of tannic acid; specifically, change S4 to:

[0096] At room temperature, 25g of glacial acetic acid and 2500mL of water were mixed and magnetically stirred at a speed of 400r / min for 5min. Then, 12g of chitosan was added and magnetically stirred until completely dissolved to obtain a chitosan-acetic acid aqueous solution.

[0097] The degree of deacetylation of the chitosan is 90%.

[0098] 2. In S7, change "mix all the chitosan-tannic acid aqueous solution obtained in S4 and all the monocrosslinked microcapsules obtained in S6 at 40℃ and then perform magnetic stirring" to "mix all the chitosan-acetic acid aqueous solution obtained in S4 and all the monocrosslinked microcapsules obtained in S6 at 40℃ and then perform magnetic stirring".

[0099] This comparative example also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0100] Comparative Example 3

[0101] This comparative example provides a method for preparing essential oil microcapsule powder with high oil loading capacity, which adopts a preparation method that is basically the same as that in Example 1, except that:

[0102] 1. S4 is omitted;

[0103] 2. In S7, replace the chitosan-tannic acid aqueous solution with water by mass, that is, change "mix all the chitosan-tannic acid aqueous solution obtained in S4 and all the single cross-linked microcapsules obtained in S6 at 40℃ and then stir magnetically" to "mix 5000mL of water and all the single cross-linked microcapsules obtained in S6 at 40℃ and then stir magnetically".

[0104] This comparative example also provides an essential oil microcapsule powder obtained by the aforementioned preparation method.

[0105] Test case

[0106] The surface oil content, moisture content, yield, encapsulation efficiency, oil loading, sustained-release performance, long-term controlled-release performance, solubility, angle of repose, average particle size, and polydispersity index of the essential oil microcapsule powders obtained in Examples 1-5 and Comparative Examples 1-3 were tested using the following methods:

[0107] 1. The test method for surface oil content is as follows:

[0108] Weigh 0.05g of microcapsules and add them to a centrifuge tube. Add 25mL of petroleum ether, tighten the centrifuge tube cap, and sonicate for 5min. Centrifuge the supernatant after sonication at 3000r / min for 15min. Take the supernatant, filter it through a 0.22μm organic phase filter membrane, and perform liquid chromatography detection. Record the peak area and calculate the concentration according to the standard curve.

[0109] 2. The moisture content was tested using the Karl Fischer method.

[0110] 3. Yield = Total oil content of microcapsules / Added essential oil content × 100%;

[0111] The test method for the total oil quality of microcapsules is as follows:

[0112] Weigh 0.05 g of microcapsules and add them to a centrifuge tube. Add anhydrous ethanol (10 mL), anhydrous diethyl ether (10 mL), and petroleum ether (5 mL) in a 2:2:1 ratio until the total solvent volume is 25 mL. Tighten the centrifuge tube cap and sonicate for 3 h. Centrifuge the supernatant after sonication at 3000 r / min for 15 min. Take the supernatant, filter it through a 0.22 μm organic phase filter membrane, and perform liquid chromatography detection. Record the peak area and calculate the concentration according to the standard curve.

[0113] 4. Encapsulation efficiency = (Total oil content of microcapsules - Surface oil content) / Total oil content of microcapsules × 100%;

[0114] 5. Oil loading capacity = Total oil content of microcapsules / Mass of microcapsules × 100%;

[0115] 6. The test methods for sustained-release performance and long-term sustained-release performance are as follows:

[0116] Weigh 50g of microcapsules and spread them evenly on a petri dish. Place the dish open at 25℃. Take 8g samples at regular intervals (5d, 10d, 30d, 60d, 90d) to test the encapsulation efficiency.

[0117] 7. The method for testing solubility is as follows:

[0118] Weigh 5g of microcapsules and add them to a beaker. Add 38mL of water at 30℃ to dissolve them. Centrifuge for 10min and discard the supernatant. Add another 38mL of water at 30℃ and shake to suspend the precipitate. Centrifuge for another 10min and discard the supernatant. Dry the weighing dish to constant weight and take the mass of the weighing dish as W1. Wash the remaining precipitate into the weighing dish with a small amount of water. Evaporate the water and dry to constant weight. Calculate the solubility according to the formula: solubility = 1 - [(W2 - W1) × 100%] / [(1 - water content of microcapsules) × 5].

[0119] 8. The method for testing the angle of repose is as follows:

[0120] Pour the microcapsules into a funnel all at once. Place a piece of white paper on the table below the funnel, 20cm away from the funnel. As the microcapsules fall, they form a cone on the plane of the white paper. Measure and record the height and diameter of the cone, and calculate the base angle of the cone as the angle of repose.

[0121] 9. The average particle size and polydispersity index were measured by a particle size analyzer.

[0122] The test results are as follows:

[0123] 1. Surface oil content:

[0124]

[0125] 2. Moisture content:

[0126]

[0127] 3. Yield:

[0128]

[0129] 4. Encapsulation rate:

[0130]

[0131] 5. Fuel capacity:

[0132]

[0133] 6. Sustained-release performance and long-term sustained-release performance:

[0134]

[0135] 7. Solubility:

[0136]

[0137] 8. Angle of repose:

[0138]

[0139] 9. Average particle size and polydispersity index (PDI)

[0140]

[0141] The results above show that the essential oil microcapsule powder obtained in Example 1 has better comprehensive test results than Comparative Examples 1-3 in terms of surface oil content, moisture content, yield, encapsulation rate, oil loading, sustained release performance, long-term controlled release performance, solubility, angle of repose, average particle size, and particle size polydispersity index.

Claims

1. A method for preparing essential oil microcapsule powder with high oil loading capacity, characterized in that, The process includes the following steps: preparing a gelatin aqueous solution, preparing a gum arabic aqueous solution, preparing a gum arabic-starch aqueous solution, preparing a chitosan-tannic acid aqueous solution, preparing an emulsion, primary crosslinking, and secondary crosslinking; To prepare the gum arabic-starch aqueous solution, water is stirred at 50-55°C, gum arabic is added and stirred until dissolved, corn starch is added and stirred, then the mixture is transferred to a boiling water bath for gelatinization, and cooled to room temperature to obtain the gum arabic-starch aqueous solution. The preparation of the chitosan-tannic acid aqueous solution involves mixing glacial acetic acid and water at room temperature and stirring, then adding chitosan and stirring until dissolved to obtain a chitosan-acetic acid aqueous solution; mixing tannic acid and water at room temperature and stirring until dissolved to obtain a tannic acid aqueous solution; and mixing the chitosan-acetic acid aqueous solution and the tannic acid aqueous solution at room temperature and stirring to obtain a chitosan-tannic acid aqueous solution. The preparation of the emulsion involves mixing gelatin aqueous solution, gum arabic aqueous solution, and gum arabic-starch aqueous solution at 45-50℃, stirring, adding essential oil and emulsifier, stirring, cooling to room temperature, and homogenizing under high pressure to obtain the emulsion. The first-stage crosslinking involves stirring the emulsion at 40-45°C, adjusting the pH to 4-4.5, stirring, cooling to 5-10°C, stirring at 5-10°C, adjusting the pH to 5.5-6, heating to 40-45°C, adding transglutaminase, stirring at 40-45°C, allowing to stand at 5-10°C, filtering, and collecting the filter residue to obtain single-crosslinked microcapsules. The secondary crosslinking process involves mixing chitosan-tannic acid aqueous solution and monocrosslinked microcapsules at 40-45℃ and stirring, then cooling to 5-10℃ and stirring at 5-10℃. The pH value is adjusted to 5.2-5.5, and the mixture is stirred. Tannic acid aqueous solution is added, and the mixture is stirred again. The mixture is allowed to stand at 5-10℃, filtered, and the filter residue is collected. The residue is then freeze-dried to obtain essential oil microcapsule powder.

2. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, The preparation of the gelatin aqueous solution involves stirring water at 50-55°C, adding gelatin, stirring until dissolved, and then cooling to room temperature to obtain the gelatin aqueous solution. In the preparation of the gelatin aqueous solution, the concentration of gelatin in the gelatin aqueous solution is 30-32g / 3000mL; The gelatin should be added 4-5 minutes later.

3. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, To prepare the gum arabic aqueous solution, water is stirred at 45-50°C, gum arabic is added, and the mixture is stirred until dissolved. The solution is then cooled to room temperature to obtain the gum arabic aqueous solution. The preparation of the gum arabic aqueous solution involves a gum arabic concentration of 28-30 g / 3000 mL. The gum arabic should be added 4-5 minutes later.

4. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, In the preparation of the gum arabic-starch aqueous solution, the concentration of gum arabic is 1.8-2 g / 300 mL, and the concentration of corn starch is 10-11 g / 300 mL.

5. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, In the preparation of the chitosan-tannic acid aqueous solution, the ratio of glacial acetic acid, water, and chitosan in the chitosan-acetic acid aqueous solution is 25g:2500mL:12-13g. In an aqueous solution of tannic acid, the ratio of tannic acid to water is 24-25g:2500mL. The mass ratio of chitosan to tannic acid in the chitosan-acetic acid aqueous solution is 25:24-25. The degree of deacetylation of the chitosan is 90%.

6. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, In the preparation of the emulsion, the mass ratio of gelatin in the gelatin aqueous solution, gum arabic in the gum arabic aqueous solution, corn starch in the gum arabic-starch aqueous solution, essential oil, and emulsifier is 30-32:28-30:10-11:64-65:1-1.

1. The essential oil is one of rose essential oil, sandalwood essential oil, oregano essential oil, and lavender essential oil; The essential oils were obtained through commercial channels; The emulsifier is Tween-80; During the high-pressure homogenization, the high-pressure homogenization pressure is 25-30 MPa, the high-pressure homogenization speed is 10000-12000 r / min, and the high-pressure homogenization time is 2-3 min.

7. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, In the primary cross-linking, the enzyme activity of the transglutaminase is 60 U / g; The mass ratio of gelatin to transglutaminase used in the preparation of the emulsion is 30-32:7.5-8.

8. The method for preparing high oil-loading essential oil microcapsule powder according to claim 1, characterized in that, In the secondary crosslinking, the ratio of chitosan in the chitosan-tannic acid aqueous solution, gelatin used in the preparation of single-crosslinked microcapsules, and tannic acid aqueous solution is 12-13g:30-32g:100-110mL; The mass concentration of the tannic acid aqueous solution is 10%; During the freezing process, the freezing temperature is -18°C and the freezing time is 10-12 hours. During the freeze-drying process, the freeze-drying temperature is -48℃ and the freeze-drying time is 48-50 hours.

9. An essential oil microcapsule powder obtained by the preparation method according to any one of claims 1-8.

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