Method for preparing microcapsules from beta-cyclodextrin inclusion compound microcrystal stabilized sandalwood essential oil

Abstract

The invention discloses a method for preparing microcapsules from beta-cyclodextrin inclusion compound microcrystal stabilized sandalwood essential oil, and belongs to the technical field of microcapsule preparation. The method comprises the following steps: preparing sandalwood essential oil / beta-cyclodextrin inclusion compound microcrystals, emulsifying and dispersing the sandalwood essential oil by using the inclusion compound microcrystals as an emulsifier, adding resin, and carrying out a condensation reaction to prepare the microcapsule suspension. According to the preparation method, firstly, beta-cyclodextrin and essential oil are embedded to obtain clathrate microcrystals, then the clathrate microcrystals serve as an emulsifying agent, the emulsifying effect of the essential oil is improved, resin microcapsules are convenient to prepare, and the microcapsules prepared through the method are high in essential oil embedding rate and good in stability; beta-cyclodextrin inclusion compound microcrystals are selected as a Pickering emulsion stabilizer, so that the emulsifying and stabilizing effects are good, and the microcapsule emulsion is not layered.

Description

Technical Field

[0001] The invention relates to the technical field of microcapsule preparation, in particular to a method for preparing microcapsules of beta-cyclodextrin inclusion compound microcrystals stabilizing sandalwood essential oil. Background Art

[0002] Sandalwood essential oil is a small molecular weight plant-derived secondary metabolite, mainly produced in India, Australia, Indonesia and other regions. It is extracted from the roots and stems of sandalwood and is an important product of the spice industry. Sandalwood essential oil not only has bactericidal and antibacterial effects, but also can relieve stress and soothe nervous anxiety. Therefore, it is widely used in fragrance-releasing products such as cosmetics and perfumes. However, due to the volatility and poor stability of sandalwood essential oil, its application is greatly limited. Microencapsulation can effectively block the volatilization of essential oils and effectively reduce interference from the external environment.

[0003] Microencapsulation technology is to encapsulate solid, liquid or gas core materials through an outer membrane system to play a protective barrier role. The encapsulated material is called "core material", and the material that forms the protective outer membrane is called "wall material" or "encapsulant". After the essential oil is microencapsulated by this technology, the core material can be released efficiently and continuously in a targeted manner, and the essential oil can be effectively controlled to diffuse at a specific time or location. The release of plant essential oils can also be activated by changes in external environment such as temperature, humidity, pH value, pressure, etc.

[0004] As a commonly used microencapsulation method, in-situ polymerization mainly relies on the prepolymer formed by the continuous phase to undergo chemical polymerization on the surface of the core material to achieve a higher coverage and shell strength. MF resin is often used as a polymer shell material for in-situ polymerization microencapsulation of essential oils due to its controllable preparation process, low cost and good thermal stability. As a shell material, it has a very significant effect on the morphology, structure and physical and chemical properties of the microcapsules. Although MF resin wall material has excellent mechanical properties and density, its performance still needs to be further improved in some applications with more stringent conditions.

[0005] β-cyclodextrin is a stable, non-toxic or low-toxic crystalline compound. Seven glucose molecules inside the compound are interconnected in the form of a ring structure and are often used as wall materials for microcapsules.

[0006] In the prior art, CN107287033A discloses a method for preparing sandalwood essential oil microcapsules, which includes: preparing a sandalwood essential oil alcohol solution and a β-cyclodextrin solution, then adding the sandalwood essential oil alcohol solution to the β-cyclodextrin solution, maintaining 54~57℃ water bath heating and stirring during the addition process, stopping heating after the dropwise addition is completed, continuing to stir for 3-4h and standing at 3~5℃ overnight to obtain a mixed solution, filtering and recovering the precipitate, and drying in a vacuum drying oven to obtain sandalwood essential oil microcapsules. CN103394313A and CN107550980A also disclose a method for preparing microcapsules of essential oils, and the specific preparation process is similar to that of CN107287033A. Although the above method can improve the embedding rate and stability of essential oils to a certain extent, the degree of improvement needs to be further improved.

[0007] CN111481450A discloses a method for preparing plant essential oil microcapsules, wherein the plant essential oil microcapsules are prepared by spray drying with plant essential oil as the core material, cyclodextrin and chitosan as the wall material. Chitosan is coated on the outside of cyclodextrin to improve the stability of the microcapsules, but the embedding rate of the essential oil needs to be further improved.

[0008] In order to improve the embedding rate of essential oils, emulsifiers (surfactants) are usually added during the preparation process, resulting in poor biocompatibility and biodegradability of the prepared microcapsules, which is not in line with the concept of green environmental protection. To this end, CN111820057A provides a method for preparing antibacterial plant essential oil-chitosan-based micro-nano capsules, using biocompatible nanoparticles as emulsifiers, plant essential oils as core materials, and chitosan complexes as main wall materials, and constructing efficient and broad-spectrum sustained-release antibacterial plant essential oil-chitosan-based micro-nano capsules through the Pickering emulsion template method. However, the embedding rate and stability of essential oils in this method are poor. CN111117769A discloses a method for preparing a Pickering emulsion flavor, wherein β-cyclodextrin is dissolved at high temperature, and after cooling, the cyclodextrins are self-assembled to form tiny crystals, and stabilized by sodium caseinate and emulsifiers to finally obtain an oil-in-water emulsion, and the essential oil is embedded by the β-cyclodextrin remaining in the water. However, this method still adds a portion of emulsifier, and also has disadvantages such as low embedding rate, poor stability, and poor high-temperature performance. Summary of the invention

[0009] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing microcapsules of sandalwood essential oil by using beta-cyclodextrin inclusion compound microcrystals to stabilize the essential oil. The present invention firstly embeds the essential oil with beta-cyclodextrin to obtain inclusion compound microcrystals, and then uses the inclusion compound microcrystals as an emulsifier to improve the emulsification effect of the essential oil, thereby facilitating the preparation of resin microcapsules. The microcapsules prepared by the method of the present invention have high essential oil embedding rate and good stability.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0011] In one aspect, the present invention provides a method for preparing microcapsules of β-cyclodextrin inclusion compound microcrystals stabilizing sandalwood essential oil, comprising:

[0012] Step 1: Preparation of sandalwood essential oil / β-cyclodextrin inclusion compound microcrystals:

[0013] 11) Add β-cyclodextrin to water at 55-65°C, stir until completely dissolved, and then adjust the pH to 6.5-8.0 with sodium carbonate solution to obtain a β-cyclodextrin solution; the mass volume concentration of β-cyclodextrin in the β-cyclodextrin solution is 1-5%;

[0014] 12) Maintaining the temperature and stirring continuously, add the ethanol solution of sandalwood essential oil (the mass ratio of sandalwood essential oil to anhydrous ethanol in the ethanol solution of sandalwood essential oil is 1:5-1:2) to the β-cyclodextrin solution in 11) and react for 2-4 h;

[0015] The mass ratio of the β-cyclodextrin to the sandalwood essential oil is 5:1 to 10:1;

[0016] 13) Cool naturally to room temperature, let stand for more than 30 minutes, then filter and dry the suspension to obtain β-cyclodextrin inclusion compound microcrystals;

[0017] Step 2: adding the inclusion compound microcrystals prepared in step 1 into water, and ultrasonically dispersing them into a suspension, wherein the mass volume concentration of the inclusion compound microcrystals in the suspension is 1%-5%; the ultrasonic power is 100-300 W, the ultrasonic working time is 2-5 s, the interval time is 2-5 s, and the total ultrasonic working time is 5-10 min;

[0018] Step 3: adding sandalwood essential oil to the suspension prepared in step 2, adjusting the pH, adding resin, and then performing a coagulation reaction at a certain temperature to obtain a microcapsule suspension;

[0019] 31) Adding sandalwood essential oil to the suspension prepared in step 2, stirring and emulsifying and dispersing the sandalwood essential oil; the rotation speed of the emulsification and dispersion of the sandalwood essential oil is 8000-11000 rpm, and the emulsification and dispersion time is 10-30 min;

[0020] 32) then adjusting the pH to 4.0-6.0 with an acetic acid solution; the mass volume concentration of acetic acid in the acetic acid solution is 1%-10%;

[0021] 33) Then, a resin is added, wherein the mass ratio of the sandalwood essential oil to the resin is 1:1-1:3; the temperature is raised to 70-80°C, and the reaction time is 2.0-3.5 hours to obtain a microcapsule suspension; the resin is melamine formaldehyde resin (MF), melamine-urea-formaldehyde resin (MUF), urea-formaldehyde resin (UF), polyurethane (PU) or polymethyl methacrylate (PMMA), and the mass concentration of the resin is 10wt%-30wt%.

[0022] Step 4: The microcapsule suspension is filtered and dried to obtain powdered microcapsules. The filtration time is 20 to 60 minutes. The drying temperature is 60 to 80° C. and the drying time is 10 to 15 hours.

[0023] On the other hand, the present invention also provides a microcapsule prepared by the above method.

[0024] The present invention relies on the hydrophobic properties and spatial volume matching effect of the internal cavity of β-cyclodextrin (β-CD). During the stirring process, β-cyclodextrin and essential oil can first form amphiphilic nano-scale small particles through host-guest interaction, and the formed small particles further self-assemble to form lamellar micron-scale amphiphilic inclusion compound microcrystals. These amphiphilic microcrystals can aggregate at the oil-water phase interface to reduce interfacial tension, thereby forming a Pickering emulsion. Adding β-cyclodextrin inclusion compound microcrystals as an emulsifier to the essential oil solution can significantly improve the emulsification effect of the essential oil, and has very good development prospects.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The invention provides a method for preparing microcapsules of sandalwood essential oil by using beta-cyclodextrin inclusion compound microcrystals to stabilize the essential oil. The method is simple and easy to operate, has good emulsification effect, and the prepared microcapsules have regular morphology and good dispersibility. The beta-cyclodextrin inclusion compound microcrystals are selected as an emulsifier, which has good emulsification and dispersion effect, can greatly improve the embedding rate of the essential oil, and the prepared microcapsules have excellent sustained-release performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a SEM image of the microcapsules prepared in Example 1 of the present invention;

[0028] Figure 2 The TGA graph of the microcapsules and sandalwood essential oil prepared in Example 1 of the present invention;

[0029] Figure 3 This is a diagram showing the sustained release of the aroma of the microcapsules and sandalwood essential oil prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the technical problems to be solved, technical solutions and advantages of the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0031] In the present invention, the materials and reagents used can be obtained from commercial sources unless otherwise specified.

[0032] The present invention provides a method for preparing microcapsules of sandalwood essential oil by using beta-cyclodextrin inclusion compound microcrystals to stabilize the sandalwood essential oil, and the specific embodiments are as follows.

[0033] Example 1

[0034] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0035] Step 1: Stir and mix 2 g of β-cyclodextrin powder and 200 ml of deionized water, and react in a round-bottom flask with stirring. The temperature is maintained at 60 °C, the stirring speed is 400 rpm, the stirring time is 1 h, and the pH is adjusted to 7.0 with sodium carbonate solution; 0.4 g of sandalwood essential oil is dissolved in anhydrous ethanol at a mass ratio of 1:5, and then the sandalwood essential oil ethanol solution is slowly dripped into the flask for reaction. The inclusion reaction time is 3 h; naturally cool to room temperature, stand for 30 min, then filter and dry the suspension (50 °C oven drying) to obtain β-cyclodextrin inclusion compound microcrystals.

[0036] Step 2: Mix 3 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 1.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 100 W, ultrasonic working time of 2 s, ultrasonic working time interval of 2 s, and ultrasonic working time of 5 min.

[0037] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 5 g of sandalwood essential oil and emulsify and disperse for 10 min, and the emulsification homogenization speed is 8000 rpm. The pH value of the emulsion is adjusted to 5.0 with an acetic acid aqueous solution with a mass volume concentration of 10%, and then 100 g of MF resin prepolymer (mass fraction 10%) is slowly dripped in for a coagulation reaction. The reaction temperature is 75°C and the reaction time is 3.0 h, and finally a microcapsule suspension is obtained.

[0038] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 60 min and the drying time at 80°C is 10 h.

[0039] Figure 1 This is the SEM picture of the microcapsules prepared in Example 1. Figure 1It can be seen that the prepared microcapsules are regular spherical, with very smooth surfaces, uniform dispersion, and no obvious cracks on the shell surface, indicating that the microcapsule shell has good integrity and stability. In addition, the scanning electron microscope image also shows that after the two wall material microcapsules are oven dried, the capsule wall structure is stable and no obvious cracking occurs, indicating that the microcapsule shell has good stability.

[0040] The thermal degradation behaviors of sandalwood essential oil and the microcapsules prepared in Example 1 were analyzed by thermogravimetric analyzer (TGA). Figure 2 As shown. With the increase of temperature, the mass of sandalwood essential oil gradually decreases, and most of the mass loss is concentrated in the range of 70-205 ℃. The initial volatilization temperature of sandalwood essential oil is 60 ℃, and it is almost completely evaporated at 210 ℃. Since water evaporates easily at lower temperatures, the microcapsules produce thermal decomposition earlier than sandalwood essential oil. The main mass loss of microcapsules is concentrated in the range of 310-430 ℃, and the main weight loss temperature of microcapsules is about 150 ℃ higher than that of sandalwood essential oil, which significantly improves the thermal stability of sandalwood essential oil.

[0041] In order to study the changes of characteristic VOCs components of sandalwood essential oil after microencapsulation, an appropriate amount of microcapsule sample of Example 1 was weighed into a headspace bottle, the sample was shaken for 10 min, adsorbed for 30 min, desorbed at 250 °C for 3 min, and finally subjected to headspace solid phase microextraction test at 60 °C. The gas chromatography-mass spectrometry method was as follows: column DB-5MS (Agilent, J&W Scientific, 30m*0.25mm*0.25μm), injection port 250 °C, no split, carrier gas was high-purity helium, flow rate 1.00ml / min; temperature program: 40 °C for 2 min, 6 °C / min to 180 °C for 2 min, 6 °C / min to 300 °C for 2 min. Interface 300 °C, ion source 250 °C, quadrupole 150 °C, mass spectrometry acquisition m / z 20-500. The changes in the characteristic VOCs components of sandalwood essential oil are shown in Table 1.

[0042] Table 1

[0043]

[0044] As can be seen from Table 1, the microencapsulation process of sandalwood essential oil effectively retained the main characteristic VOCs components of the essential oil (β-santalol, α-santalol and bergamot alcohol). This shows that β-cyclodextrin inclusion compound microcrystals effectively stabilized the sandalwood essential oil and successfully prepared the fragrance-releasing microcapsules, so that the characteristic VOCs components of sandalwood essential oil were fully retained.

[0045] Example 2

[0046] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0047] Step 1: Mix 6 g of β-cyclodextrin powder and 200 ml of deionized water, and stir the mixture in a round-bottom flask. Maintain the temperature at 65 °C, stir at 500 rpm, and stir for 1 h. Adjust the pH to 7.0 with sodium carbonate solution. Dissolve 1.0 g of sandalwood essential oil in anhydrous ethanol at a mass ratio of 1:5, and then slowly drip the sandalwood essential oil ethanol solution into the flask for reaction. The inclusion reaction time is 3 h. Cool the mixture naturally to room temperature, let it stand for 30 min, and obtain β-cyclodextrin inclusion complex microcrystalline powder by suction filtration and drying in an oven at 60 °C to obtain β-cyclodextrin inclusion complex microcrystalline powder.

[0048] Step 2: Mix 1 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 1.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 100 W, ultrasonic working time of 2 s, ultrasonic working time interval of 2 s, and ultrasonic working time of 5 min.

[0049] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 5 g of sandalwood essential oil and emulsify and disperse for 10 min, and the emulsification homogenization speed is 8000 rpm. The pH value of the emulsion is adjusted to 4.0 with an acetic acid aqueous solution with a mass volume concentration of 10%, and then 100 g of MF resin prepolymer (mass fraction 10%) is slowly dripped in for a coagulation reaction. The reaction temperature is 80 ° C and the reaction time is 2.0 h. Finally, a microcapsule suspension is obtained.

[0050] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 60 min and the drying time at 80°C is 10 h.

[0051] Example 3

[0052] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0053] Step 1: Stir and mix 10 g of β-cyclodextrin powder and 200 ml of deionized water, and stir and react in a round-bottom flask. Maintain the temperature at 65 °C, stir at 500 rpm, stir for 1 h, and adjust the pH to 7.0 with sodium carbonate solution; dissolve 2.0 g of sandalwood essential oil in anhydrous ethanol at a mass ratio of 1:5, and then slowly drip the sandalwood essential oil ethanol solution into the flask for reaction. The inclusion reaction time is 3 h; cool naturally to room temperature, stand for 30 min, filter and dry in an oven at 60 °C to obtain β-cyclodextrin inclusion complex microcrystalline powder, and obtain β-cyclodextrin inclusion complex microcrystals.

[0054] Step 2: Mix 1 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 1.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 150 W, ultrasonic working time of 3 s, ultrasonic working time interval of 2 s, and ultrasonic working time of 6 min.

[0055] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 6 g of sandalwood essential oil and emulsify and disperse for 15 min, and the emulsification homogenization speed is 8000 rpm. The pH value of the emulsion is adjusted to 4.5 with acetic acid solution with a mass volume concentration of 5%, and then 60 g of MF resin prepolymer (mass fraction 10%) is slowly dripped in for condensation reaction. The reaction temperature is 75°C and the reaction time is 2.5 h. Finally, a microcapsule suspension is obtained.

[0056] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 30 min and the drying time is 12 h.

[0057] Example 4

[0058] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0059] Step 1: Stir and mix 8 g of β-cyclodextrin powder and 160 ml of deionized water, and stir and react in a round-bottom flask. Maintain the temperature at 65 °C, stir at 600 rpm, stir for 1 h, and adjust the pH to 7.0 with sodium carbonate solution; dissolve 1.0 g of sandalwood essential oil in anhydrous ethanol at a mass ratio of 1:5, and then slowly drip the sandalwood essential oil ethanol solution into the flask for reaction. The inclusion reaction time is 3 h; naturally cool to room temperature, stand for 40 min, filter and dry in an oven at 60 °C to obtain β-cyclodextrin inclusion compound microcrystalline powder, and obtain β-cyclodextrin inclusion compound microcrystals.

[0060] Step 2: Mix 5 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 5.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 200 W, ultrasonic working time of 5 s, ultrasonic working time interval of 3 s, and ultrasonic working time of 5 min.

[0061] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 12 g of sandalwood essential oil and emulsify and disperse for 20 min, and the emulsification homogenization speed is 10000 rpm. The pH value of the emulsion is adjusted to 5.0 with an acetic acid solution with a mass volume concentration of 10%, and then 60 g of MF resin prepolymer (mass fraction 20%) is slowly dripped in for a coagulation reaction. The reaction temperature is 80 ° C and the reaction time is 3.0 h. Finally, a microcapsule suspension is obtained.

[0062] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 30 min and the drying time is 15 h.

[0063] Example 5

[0064] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0065] Step 1: Mix 6 g of β-cyclodextrin powder and 200 ml of deionized water, and stir in a round-bottom flask for reaction. Maintain the temperature at 65 °C, stir at 500 rpm, and stir for 1 h. Adjust the pH to 7.0 with sodium carbonate solution. Dissolve 1.0 g of sandalwood essential oil in anhydrous ethanol at a mass ratio of 1:5, and then slowly drip the sandalwood essential oil ethanol solution into the flask for reaction. The inclusion reaction time is 3 h. Cool naturally to room temperature, stand for 30 min, filter, and dry in an oven at 60 °C to obtain β-cyclodextrin inclusion complex microcrystalline powder to obtain β-cyclodextrin inclusion complex microcrystals.

[0066] Step 2: Mix 1 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 1.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 100 W, ultrasonic working time of 2 s, ultrasonic working time interval of 2 s, and ultrasonic working time of 5 min.

[0067] Step 3: Pour the β-cyclodextrin inclusion compound dispersion into a beaker as the continuous phase, add 5 g of sandalwood essential oil and emulsify and disperse for 10 min, and the emulsification homogenization speed is 8000 rpm. The pH value of the emulsion is adjusted to 5.0 with an acetic acid solution with a mass volume concentration of 10%, and then 50 g of melamine-urea-formaldehyde resin (MUF) prepolymer (mass fraction 20%) is slowly dripped in for a coagulation reaction. The reaction temperature is 75 ° C and the reaction time is 3.0 h. Finally, a microcapsule suspension is obtained.

[0068] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 60 min and the drying time at 80°C is 10 h.

[0069] Example 6

[0070] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0071] Step 1: Stir and mix 10 g of β-cyclodextrin powder and 200 ml of deionized water, and stir and react in a round-bottom flask. Maintain the temperature at 65 °C, stir at 500 rpm, stir for 1 h, and adjust the pH to 7.0 with sodium carbonate solution; dissolve 2.0 g of sandalwood essential oil in anhydrous ethanol at a mass ratio of 1:5, and then slowly drip the sandalwood essential oil ethanol solution into the flask for reaction. The inclusion reaction time is 3 h; naturally cool to room temperature, stand for 30 min, filter and dry in an oven at 60 °C to obtain β-cyclodextrin inclusion complex microcrystalline powder to obtain β-cyclodextrin inclusion complex microcrystals.

[0072] Step 2: Mix 1 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a β-cyclodextrin inclusion complex suspension with a concentration of 1.0%, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 150 W, ultrasonic working time of 3 s, ultrasonic working time interval of 2 s, and ultrasonic working time of 6 min.

[0073] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 6 g of sandalwood essential oil and emulsify and disperse for 15 min, and the emulsification homogenization speed is 8000 rpm. The pH value of the emulsion is adjusted to 4.5 with an acetic acid solution with a mass volume concentration of 5%, and then 60 g of urea-formaldehyde resin (UF) prepolymer (mass fraction 10%) is slowly dripped in for a coagulation reaction. The reaction temperature is 80 ° C and the reaction time is 2.0 h. Finally, a microcapsule suspension is obtained.

[0074] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 30 min and the drying time is 12 h.

[0075] Example 7

[0076] A method for preparing microcapsules of sandalwood essential oil stabilized by β-cyclodextrin inclusion compound microcrystals, comprising:

[0077] Step 1: Mix 8 g of β-cyclodextrin powder and 200 ml of deionized water and stir, and react in a round-bottom flask with stirring. The temperature is maintained at 65 °C, the stirring speed is 500 rpm, the stirring time is 1 h, and the pH is adjusted to 7.0 with sodium carbonate solution; 1.6 g of sandalwood essential oil is dissolved in anhydrous ethanol at a mass ratio of 1:2, and then the sandalwood essential oil ethanol solution is slowly dripped into the flask for reaction. The inclusion reaction time is 3 h; naturally cool to room temperature, stand for 40 min, filter and dry in an oven at 60 °C to obtain β-cyclodextrin inclusion complex microcrystalline powder to obtain β-cyclodextrin inclusion complex microcrystals.

[0078] Step 2: Mix 3 g of β-cyclodextrin inclusion complex microcrystalline powder with 100 ml of deionized water to prepare a 3.0% β-cyclodextrin inclusion complex suspension, and disperse it using an ultrasonic crusher. The process parameters are: ultrasonic power of 100 W, ultrasonic working time of 5 s, ultrasonic working time interval of 3 s, and ultrasonic working time of 6 min.

[0079] Step 3: Pour the β-cyclodextrin inclusion compound dispersion as the continuous phase into a beaker, add 12 g of sandalwood essential oil and emulsify and disperse for 25 min, and the emulsification homogenization speed is 9000 rpm. The pH value of the emulsion is adjusted to 5.5 with an acetic acid solution with a mass volume concentration of 10%, and then 40 g of polyurethane resin (PU) monomer (mass fraction 30%) is slowly dripped in for condensation reaction. The reaction temperature is 70 ° C and the reaction time is 3.0 h. Finally, a microcapsule suspension is obtained.

[0080] Step 4: After the suspension is filtered and dried, a powdered microcapsule product is obtained. The filtration time is 40 min and the drying time is 12 h.

[0081] In order to further illustrate the beneficial effects of the present invention, the following comparative example was constructed.

[0082] Comparative Example 1

[0083] In this comparative example, steps 2-4 are omitted, and the remaining conditions are the same as those in Example 1.

[0084] Comparative Example 2

[0085] In this comparative example, step 1 is omitted, and the β-cyclodextrin inclusion compound microcrystalline powder in step 2 is replaced by an equal amount of nano-TiO2, and the other conditions are the same as those in Example 1.

[0086] Comparative Example 3

[0087] In this comparative example, step 1 is omitted, and the β-cyclodextrin inclusion compound microcrystalline powder in step 2 is replaced by an equal amount of nano-SiO2, and the other conditions are the same as those in Example 1.

[0088] Comparative Example 4

[0089] In step 1 of this comparative example, sandalwood essential oil was omitted, and the other conditions were the same as those in Example 1.

[0090] Comparative Example 5

[0091] In this comparative example, the MF resin prepolymer was replaced with chitosan of the same concentration and amount, and the other conditions were the same as those in Example 1.

[0092] Comparative Example 6

[0093] In step 3 of this comparative example, sandalwood essential oil was omitted, and the other conditions were the same as those in the embodiment.

[0094] Comparative Example 7

[0095] The specific comparison is as follows:

[0096] Step 1: Dissolve 12 g of β-cyclodextrin powder in 240 ml of deionized water, stir the deionized water, heat at 70°C, and fully dissolve under the action of an electric stirrer to obtain aqueous phase I;

[0097] Step 2: Place 5 g of sodium caseinate and 1 g of Tween-20 in aqueous phase I, heat at 50°C, and fully dissolve them under the action of an electric stirrer to obtain aqueous phase II;

[0098] Step 3: Cool the aqueous phase II to room temperature, reduce the speed, and stir evenly with an electric stirrer;

[0099] Step 4: Dissolve 5 g of sandalwood essential oil in anhydrous ethanol at a ratio of 1:5 (w / w), then drop it into the aqueous phase II and stir to mix thoroughly. After high-speed shearing, an oil-in-water emulsion is formed, which is the nano-scale Pickering emulsion essence; then the filtration time is 60 min and the drying time at 80°C is 10 h.

[0100] The inventors also used the olfactory method to visually evaluate the sustained release of aroma. Sandalwood essential oil and microcapsules prepared in Examples 1-7 and Comparative Examples 1-7 (containing equal amounts of sandalwood essential oil) were evenly dispersed in a crystallization dish and placed in a 60°C oven for forced air drying. Artificial olfactory smelling was performed regularly every day (the average of the results of multiple people's sniffing was taken), and the position was kept directly above the crystallization dish during the sniffing. The olfactory grading is shown in Table 2 below. The average of three sniffs is taken, and the results are shown in Table 3. The olfactory scoring data of Example 1 and sandalwood essential oil are shown in Table 3. Figure 3 shown.

[0101] Table 2

[0102]

[0103] Table 3

[0104]

[0105] From Table 3 and Figure 3 It can be seen that the pure sandalwood essential oil has an obvious fragrance in the early stage under the environment of 60°C, but the fragrance disappears completely after only 4 days of heating, which shows that the pure essential oil is unstable and easily volatilizes under the influence of high temperature. After the sandalwood essential oil in Example 1 is microencapsulated, the fragrance release time is significantly extended, and the overall fragrance is released quickly first and then slowly. The microcapsules prepared in Examples 2-7 also have the same sustained release effect as above. The results show that after the sandalwood essential oil is microencapsulated, the fragrance release time can be extended to 13-14 days under the high temperature environment of 60°C, indicating that the microcapsule shell has good stability and integrity.

[0106] The inclusion compound microcrystals obtained by encapsulating sandalwood essential oil with simple β-cyclodextrin (Comparative Example 1) can be exerted extremely quickly at a high temperature of 60°C; the microcapsules obtained by using conventional nanoparticles (nano TiO2 (Comparative Example 2), nano SiO2 (Comparative Example 3)) as Pickering emulsions can improve their sustained-release effect to a certain extent; the fragrance release time is extended to 9 days by replacing the MF resin prepolymer with chitosan (Comparative Example 5); the fragrance release time of the microcapsules obtained by using the prior art (Comparative Example 7) is extended to 8 days; all of which are lower than those of the method of the present invention.

[0107] The inventors also conducted thermal stability tests on the microcapsules prepared in the above Examples 1-7 and Comparative Examples 1-7. The test results are shown in Table 4.

[0108] Table 4

[0109]

[0110] It can be seen from Table 4 that the microcapsules prepared in the present invention have good thermal stability.

[0111] The inventors also tested the embedding efficiency of the microcapsules. The specific method is as follows. The embedding efficiency results are shown in Table 5.

[0112] Standard curve of sandalwood essential oil: prepare a certain concentration of sandalwood essential oil solution with anhydrous ethanol, adjust to zero with anhydrous ethanol as blank test, perform full wavelength scanning on UV spectrophotometer, and determine that the maximum absorption wavelength of sandalwood essential oil is 206nm. Determine the absorbance value of sandalwood essential oil-ethanol solution of different concentrations at its maximum absorption wavelength of 206nm, and obtain the regression equation of the standard curve: y=1.275x+0.8828, R²=0.9917.

[0113] Weigh 0.1 g of microcapsule powder, wash it with anhydrous ethanol, dissolve it in 50 ml of anhydrous ethanol, and treat it under 800W ultrasonic conditions for 20 minutes to completely break the capsule wall and dissolve all the sandalwood essential oil in anhydrous ethanol. The mass concentration of sandalwood essential oil was calculated according to the linear regression equation by measuring the absorbance at the maximum ultraviolet absorption peak wavelength in the solution, and the essential oil encapsulation efficiency (EE, %) was calculated according to the following formula: EE = m0 / m × 100%.

[0114] Wherein, EE is the embedding efficiency of microcapsules (%); m0 is the mass of essential oil contained in the microcapsules (g); and m is the mass of essential oil initially added to the system (g) (the sum of the mass of sandalwood essential oil added in steps 1 and 3).

[0115] The inventors first conducted an experiment on the factors affecting the microcapsule embedding rate. The microcapsule preparation process step 1 was the same as in Example 1, the preparation method of β-cyclodextrin inclusion compound microcrystals in step 2 was the same as in Example 1, the concentrations were shown in Table 5, and the relevant parameters in step 3 were shown in Table 5, where the core-to-wall ratio was the mass ratio of sandalwood essential oil to MF resin wall material in step 3.

[0116] Table 5 Single factor experiment of microcapsule embedding efficiency

[0117]

[0118] As shown in Table 5, the mass ratio of sandalwood essential oil to MF resin has a great influence on the embedding rate of the prepared microcapsules, and when the core-to-wall ratio is 1:2, the embedding rate of the obtained microcapsules is the highest, reaching 81.15%; the concentration of β-cyclodextrin inclusion compound microcrystals also has a relevant effect on the embedding rate of the prepared microcapsules, and with the increase of concentration, the embedding first increases and then decreases; the reaction temperature of microcapsule formation has a great influence on the embedding rate of microcapsules, and when the reaction temperature reaches 80°C, the embedding rate decreases by more than 16%; the reaction time and the pH of the solution also have a great influence on the embedding rate of the prepared microcapsules. That is, the inventors conducted different experiments on the mass ratio of sandalwood essential oil to MF resin, the concentration of β-cyclodextrin inclusion compound microcrystals, the condensation reaction temperature, the reaction time and the reaction pH, and obtained the experimental conditions with a high microcapsule embedding rate.

[0119] The embedding rates of the microcapsules prepared in Examples 1-7 and Comparative Examples 1-7 were tested, and the results are shown in Table 6.

[0120] Table 6

[0121]

[0122] It can be seen from Table 5 that the microcapsules prepared in the present invention have a higher embedding rate than those in the comparative example.

[0123] In summary, the present invention uses β-cyclodextrin inclusion compound microcrystals as an emulsifier, and the prepared microcapsules have good sustained-release effect and can greatly improve the embedding rate of sandalwood essential oil.

[0124] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing microcapsules of β-cyclodextrin inclusion compound microcrystals stabilizing sandalwood essential oil, characterized in that: include: Step 1: Preparation of sandalwood essential oil / β-cyclodextrin inclusion compound microcrystals; Step 2: adding the inclusion compound microcrystals prepared in step 1 into water and dispersing them into a suspension by ultrasonication; Step 3: adding sandalwood essential oil to the suspension prepared in step 2, adjusting the pH, adding resin, and then performing a coagulation reaction at a certain temperature to obtain a microcapsule suspension; Step 4: After the microcapsule suspension is filtered and dried, powdered microcapsules are obtained.

2. The method according to claim 1, characterized in that The step 1 is specifically as follows: 11) Add β-cyclodextrin to water at 55-65°C, stir until completely dissolved, and then adjust the pH to 6.5-8.0 with sodium carbonate solution to obtain a β-cyclodextrin solution; 12) Maintaining the temperature and stirring continuously, add the ethanol solution of sandalwood essential oil to the β-cyclodextrin solution in 11) and react for 2 to 4 hours; 13) Cool naturally to room temperature and stand for more than 30 minutes, then filter and dry the suspension to obtain β-cyclodextrin inclusion compound microcrystals.

3. The method according to claim 2, characterized in that In the above 11), the mass volume concentration of β-cyclodextrin in the β-cyclodextrin solution is 1-5%, in the above 12), the mass ratio of sandalwood essential oil to anhydrous ethanol in the sandalwood essential oil ethanol solution is 1:5-1:2, and the mass ratio of β-cyclodextrin to sandalwood essential oil is 5:1-10:1; in the above 13), the drying temperature is 50-70°C; In step 11) and step 12), the stirring speed is 400-800 rpm.

4. The method according to claim 1, characterized in that: In the step 2, the mass volume concentration of the inclusion compound microcrystals in the suspension is 1%-5%.

5. The method according to claim 4, characterized in that In step 2, the ultrasonic power is 100-300 W, the ultrasonic working time is 2-5 s, the interval time is 2-5 s, and the total ultrasonic working time is 5-10 min.

6. The method according to claim 1, characterized in that The step 3 is specifically as follows: 31) Add sandalwood essential oil to the suspension prepared in step 2, and stir to emulsify and disperse; 32) Then adjust the pH to 4.0-6.0 with acetic acid solution; 33) Then, the resin is added, the temperature is raised to 70-80 °C, and the reaction time is 2.0-3.5 h to obtain a microcapsule suspension.

7. The method according to claim 6, characterized in that In the step 32), the mass volume concentration of acetic acid in the acetic acid solution is 1% to 10%; in the step 33), the mass concentration of the resin is 10wt% to 30wt%; the mass ratio of the sandalwood essential oil to the resin is 1:1-1:3; In the above 31), the rotation speed of the sandalwood essential oil emulsification dispersion is 8000-11000 rpm, and the emulsification dispersion time is 10-30 min.

8. The method according to claim 7, characterized in that The resin is melamine formaldehyde resin (MF), melamine-urea-formaldehyde resin (MUF), urea-formaldehyde resin (UF), polyurethane (PU) or polymethyl methacrylate (PMMA).

9. The method according to claim 1, characterized in that: In the step 4, the filtration time is 20 to 60 minutes; the drying temperature is 60 to 80°C, and the drying time is 10 to 15 hours.

10. A fragrance-releasing microcapsule, characterized in that: It is prepared by the method according to any one of claims 1 to 9.

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