Preparation method of slow-release star anise essential oil microcapsule

Abstract

The invention discloses a preparation method of a slow-release star anise essential oil microcapsule, which comprises the following steps: standing star anise essential oil in a dark place, taking an upper-layer clarified phase, and carrying out ethanol-assisted emulsification, disodium hydrogen phosphate aqueous solution dispersion, high-speed shearing and ice-water bath cooling to form primary emulsion; sequentially introducing gelatin and Arabic gum to construct a composite membrane, adding modified starch to form a ternary structure, loading polylactic acid, and performing freezing-vacuum drying to form a shell; then adopting glutaraldehyde steam cross-linking to stabilize the network, dispersing with cold water, and curing with sodium carboxymethyl cellulose to obtain a stable dispersion liquid; carrying out particle size grading, ceramic membrane filtration and spray drying to obtain microcapsule powder, finally carrying out surface modification by octadecyltriethoxysilane, and adapting to a vaseline or water-based system. Through step-by-step assembly of multi-component wall materials, low-temperature induction of channel orientation and steam crosslinking, the structural stability is enhanced, surface hydrophobicity is used for regulating and controlling interface behaviors, the microcapsule is endowed with internal mass transfer regulation and control capability, and stable, uniform and long-time release of aroma is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of essential oils, in particular to a preparation method of slow-release star anise essential oil microcapsules. BACKGROUND

[0002] The star anise essential oil has distinct sweet and pungent aroma and typical biological activity, but main volatile components thereof are easy to escape at normal temperature and pressure, and are sensitive to light, heat and air contact, and chemical state is easy to change.

[0003] In the prior art, ethanol dissolution, cyclodextrin inclusion or simple wrapping of a single protein wall material is usually adopted to delay volatilization. Although the above methods can provide certain protection in the initial stage, since the wall material structure is uniform, the interface is loosely combined, and the molecular transmission path is not directionally constrained, the essential oil still gradually leaks during storage, and the aroma intensity rapidly rises and then rapidly decreases in the initial use stage, so that stable and long-lasting olfactory response cannot be maintained. SUMMARY

[0004] The application aims to provide a preparation method of slow-release star anise essential oil microcapsules, and realize stable, uniform and long-time aroma release from the beginning of use.

[0005] To achieve the above object, the technical scheme adopted by the application is as follows: a preparation method of slow-release star anise essential oil microcapsules, comprising the following steps: S1: after the star anise essential oil is placed in the dark, the upper clear phase is taken out, mixed with anhydrous ethanol, added dropwise into a sodium phosphate dibasic aqueous solution, and then subjected to high-speed shearing and ice water bath cooling to form a primary emulsion; S2: gelatin aqueous solution is added to the primary emulsion to form an adsorption film, then arabic gum aqueous solution is added, the pH value is adjusted, and standing is performed to form a composite film; S3: modified starch suspension liquid is added to the composite film primary emulsion, then the temperature is raised and then lowered to form a ternary composite film; S4: polylactic acid acetone solution is added to the ternary composite film, then freezing treatment is performed, and then vacuum drying is performed to form a shell layer, and the dried product is subjected to glutaraldehyde vapor phase crosslinking to form a crosslinked shell layer, and the crosslinked product is dispersed in cold water, and carboxymethyl cellulose sodium is added to mature to form a dispersion liquid; S5: the dispersion liquid is subjected to particle size grading, filtration and spray drying to obtain microcapsule powder, the microcapsule powder is subjected to octadecyl triethoxysilane treatment, and the final product is adapted to a vaseline or water-based system.

[0006] Preferably, in S1, the upper clear phase is transferred to a nitrogen-replaced airtight container; the dropwise adding speed is 0.8 mL per minute; the high-speed shearing is performed at 8000 rpm for 90 seconds; and the ice water bath cooling is performed to 8 DEG C for 12 minutes to reduce the essential oil molecule kinetic energy in the liquid drop interior.

[0007] Preferably, in S2, the gelatin aqueous solution has a concentration of 3.5% and a pH of 4.2; the gum arabic aqueous solution has a concentration of 4.0% and a pH of 7.0; the pH is adjusted to 3.8 using a 0.1 mol / L citric acid solution; and the mixture is allowed to stand for 18 minutes to allow the gelatin-gum arabic composite membrane to complete the molecular chain rearrangement.

[0008] Preferably, in S3, the modified starch suspension has a solid content of 2.8% and a degree of substitution of 0.32; the heating rate is 0.3℃ to 32℃ per minute and held at that temperature for 22 minutes; the cooling rate is 0.25℃ to 4℃ per minute and held at that temperature for 15 minutes; and a water-depleted region is formed inside the ternary composite membrane during the cooling process.

[0009] Preferably, in S4, the concentration of polylactic acid acetone solution is 1.2%; the amount added is 0.19 times the total mass of the colostrum; freezing at -12°C for 110 seconds causes the aqueous phase to precipitate in the form of micron-sized oriented ice crystals; vacuum drying is carried out at 5°C and 80 Pa for 4.5 hours.

[0010] Preferably, in S4, the glutaraldehyde vapor concentration is 210 ppm; the surface area to volume ratio of the open ceramic dish is 1:140; crosslinking is performed at 16°C for 2 hours; after crosslinking, ventilation is carried out for 35 minutes and high-purity nitrogen is purged for 10 minutes.

[0011] Preferably, in S4, the dispersed solids content is 3.2%; the cold water temperature is 6°C; the amount of sodium carboxymethyl cellulose added is 0.013 times the mass of the dispersion; and the sodium carboxymethyl cellulose is aged at 4°C for 48 hours to allow interfacial interpenetration between the sodium carboxymethyl cellulose brush layer and the shell surface.

[0012] Preferably, in S5, the centrifugal classification speed is 8200 rpm, the feed flow rate is 1.4 L / h, and the particle size fraction of 9.0-11.8 μm is collected; the ceramic membrane pore size is 0.42 μm; the spray drying inlet air temperature is 112℃, the outlet air temperature is 58℃, and the atomization pressure is 180 kPa.

[0013] Preferably, in S5, the concentration of the octadecyltriethoxysilane ethanol solution is 0.27%; fluidized bed treatment for 11 minutes; vacuum treatment at 45°C and 60Pa for 3 hours; freeze-thaw cycle at 85% humidity for 18 hours, freeze at -18°C for 90 minutes, and thaw at 25°C.

[0014] Preferably, in step S5, the petrolatum is mixed in a ratio of 1:4.5, mixed at 75°C for 5 minutes, and maintained at 45°C for 12 minutes; the beeswax-microcrystalline wax mixture is 0.9% of the microcapsule mass, with a beeswax:microcrystalline wax ratio of 3:2; the water-based system microcapsules are mixed with deionized water in a ratio of 1:12, and 0.15% xanthan gum is added; the fragrance block is cured at 22°C for 24 hours; and the water-based spray filler is filled with a dimethyl ether:propane propellant in a ratio of 7:3.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a microcapsule structure with intrinsic mass transfer regulation capabilities through stepwise assembly of multi-component wall materials, low-temperature induced pore orientation, enhanced network stability resulting from vapor phase crosslinking, and diffusion barriers formed by surface hydrophobic modification. As a result, essential oils are effectively confined within the core, migrating slowly to the outside only along specific directions after overcoming multiple resistances. Aroma output is no longer dependent on the intensity of external stimuli but is determined by the structure itself, thus achieving stable, uniform, and prolonged aroma release from the moment of activation. Attached Figure Description

[0016] Figure 1 This is a flowchart of the preparation method of the sustained-release star anise essential oil microcapsules of the present invention. Detailed Implementation

[0017] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0018] like Figure 1 As shown, this invention proposes a method for preparing sustained-release star anise essential oil microcapsules, comprising the following steps: S1: After the star anise essential oil is left to stand in the dark, the upper clear phase is taken and mixed with anhydrous ethanol. This mixture is then added dropwise to a sodium hydrogen phosphate aqueous solution. After high-speed shearing, the mixture is cooled in an ice-water bath to form a pre-emulsion. The upper clear phase is then transferred to a nitrogen-purged sealed container. The dropwise addition rate is 0.8 mL per minute. High-speed shearing is performed at 8000 rpm for 90 seconds. The mixture is then cooled in an ice-water bath to 8°C and maintained for 12 minutes to reduce the kinetic energy of the essential oil molecules inside the droplets.

[0019] S2: Add gelatin aqueous solution to colostrum to form an adsorption membrane, then add gum arabic aqueous solution, adjust the pH value, and let stand to form a composite membrane; gelatin aqueous solution concentration 3.5%, pH 4.2; gum arabic aqueous solution concentration 4.0%, pH 7.0; adjust the pH to 3.8 using 0.1 mol / L citric acid solution; let stand for 18 minutes to allow the gelatin-gum arabic composite membrane to complete molecular chain rearrangement.

[0020] S3: Add modified starch suspension to the composite membrane colostrum, heat up and then cool down to form a ternary composite membrane; the modified starch suspension has a solid content of 2.8% and a degree of substitution of 0.32; the heating rate is 0.3℃ per minute to 32℃ and held at that temperature for 22 minutes; the cooling rate is 0.25℃ per minute to 4℃ and held at that temperature for 15 minutes; during the cooling process, a water-depleted region is formed inside the ternary composite membrane.

[0021] S4: Add polylactic acid acetone solution to the ternary composite membrane, freeze-dry it under vacuum to form a shell, crosslink the dried product with glutaraldehyde vapor phase to form a crosslinked shell, disperse the crosslinked product in cold water, add sodium carboxymethyl cellulose to mature and form a dispersion. The concentration of polylactic acid-acetone solution was 1.2%; the amount added was 0.19 times the total mass of the colostrum; freezing at -12℃ for 110 seconds caused the aqueous phase to precipitate in the form of micron-sized oriented ice crystals; vacuum drying was carried out at 5℃ and 80Pa for 4.5 hours. The concentration of glutaraldehyde vapor was 210ppm; the surface area to volume ratio of the open ceramic dish was 1:140; crosslinking was carried out at 16℃ for 2 hours; after crosslinking, ventilation was carried out for 35 minutes and high-purity nitrogen was purged for 10 minutes. The dispersed solids content was 3.2%; the cold water temperature was 6℃; the amount of sodium carboxymethyl cellulose added was 0.013 times the mass of the dispersion; aging at 4℃ for 48 hours caused interfacial interpenetration between the sodium carboxymethyl cellulose brush layer and the shell surface.

[0022] S5: The dispersion is subjected to particle size classification, filtration and spray drying to obtain microcapsule powder. The microcapsule powder is treated with octadecyltriethoxysilane and adapted to petrolatum or water-based systems to form end products. The centrifugal classification process involved a centrifugal speed of 8200 rpm, a feed flow rate of 1.4 L / h, and the collection of particles with a diameter of 9.0–11.8 μm. The ceramic membrane had a pore size of 0.42 μm. The spray drying process included an inlet air temperature of 112℃, an outlet air temperature of 58℃, and an atomization pressure of 180 kPa. The concentration of the octadecyltriethoxysilane ethanol solution was 0.27%. The process included fluidized bed treatment for 11 minutes, vacuum treatment at 45℃ and 60 Pa for 3 hours, freeze-thaw cycles at 85% humidity for 18 hours, freezing at -18℃ for 90 minutes, and thawing at 25℃.

[0023] Specifically, the petrolatum mixture ratio is 1:4.5, mixed at 75°C for 5 minutes, and maintained at 45°C for 12 minutes; the beeswax and microcrystalline wax mixture ratio is 0.9% of the microcapsule mass, with beeswax:microcrystalline wax = 3:2; the water-based system microcapsules are mixed with deionized water at a ratio of 1:12, and 0.15% xanthan gum is added; the fragrance block is cured at 22°C for 24 hours; and the water-based spray filling agent is dimethyl ether:propane = 7:3.

[0024] The microcapsules obtained in this embodiment can maintain the physical state and olfactory activity of the essential oils inside for a long time when not in use, avoiding significant weakening of aroma due to fluctuations in environmental temperature and humidity or prolonged storage time; after activation, the aroma release begins gradually without a strong initial pungent smell, and the subsequent intensity changes evenly without sudden increases or decreases; it can maintain stable aroma release for several weeks in a solid matrix, and can also achieve continuous and perceptible evaporation output in an aerosol system; the release behavior is consistent under different terminal forms and is not affected by matrix polarity, viscosity or phase differences; it is ready to use after opening the bag, without activation or pretreatment, and the aroma performance is stable and predictable.

[0025] The following is a further explanation of the preparation method of the above-mentioned sustained-release star anise essential oil microcapsules, which includes the following steps: Step 1: Core Material Pretreatment and Dispersion System Construction Step 1.1: Place star anise essential oil in a clean, dry glass constant temperature container and let it stand for 24 hours in the dark to allow any trace amounts of moisture and high-boiling-point terpene impurities that may be present to settle and precipitate naturally under gravity, obtaining a clear and transparent upper phase enriched with volatile components. This phase is mainly composed of trans-anetane, anisaldehyde, and limonene, and has typical sweet and spicy aroma characteristics and a high vapor pressure, providing a chemically homogeneous starting material for subsequent encapsulation.

[0026] The upper clear phase is completely transferred to another sealed glass flask that has been purged with nitrogen three times to prevent it from being exposed to air for a long time and causing oxidation side reactions. At this time, the essential oil is in a physically stable state, without molecular configuration changes or double bond breakage, and still retains its original volatile activity and olfactory response intensity.

[0027] Step 1.2: Add anhydrous ethanol, accounting for 8% of the essential oil mass, to the above flask and stir at a constant temperature of 35°C for 15 minutes. This allows ethanol molecules to embed into the gaps in the hydrophobic network inside the essential oil, reducing the overall viscosity and enhancing the interfacial wetting ability of the polar microregions. During this process, ethanol does not condense or etherify with anethole, but only exists as a temporary solubilizing medium. It does not participate in the subsequent encapsulation reaction and does not change the thermodynamic activity of the essential oil.

[0028] The ethanol-essential oil mixture was slowly added dropwise to a pre-prepared 0.2 mol / L disodium hydrogen phosphate aqueous solution under continuous stirring, with the dropping rate controlled at 0.8 mL per minute. After the addition was complete, stirring was continued for 10 minutes to form a transient emulsified micro-region at the interface between the two phases. During this stage, the disodium hydrogen phosphate solution provided a weakly alkaline buffer environment, inhibiting the sudden change in local pH caused by ethanol residue, while simultaneously charging the surface of the essential oil microdroplets with a negative charge, laying an electrostatic foundation for the subsequent wall material adsorption.

[0029] Step 1.3: Transfer the above emulsion system into a high-speed shear machine and process it at 8000 rpm for 90 seconds to shrink the droplet size distribution to the range of 3-8 μm, forming an O / W type primary emulsion with a uniform appearance and no obvious flocculation or stratification; the droplet surfaces of this primary emulsion repel each other due to the negative charge, which improves stability, and the concentrated distribution of the droplet size is conducive to the formation of a continuous and uniform initial coating on its surface by the subsequent wall material.

[0030] Based on this, the colostrum was immediately transferred to an ice-water bath to cool down to 8°C and maintained at this temperature for 12 minutes. This significantly reduced the kinetic energy of the essential oil molecules inside the droplets, narrowed the amplitude of molecular thermal motion, made the droplet shape more rigid, and reduced the surface tension gradient. This reduced the risk of droplet aggregation or breakage caused by interfacial disturbances when the wall material solution was subsequently added. The colostrum at low temperature maintained fluidity but already possessed the basic structural toughness to resist external mechanical disturbances.

[0031] Step 1.4: Add gelatin aqueous solution (concentration 3.5%, prepared with deionized water, pH adjusted to 4.2) dropwise to the low-temperature colostrum. Keep the system temperature constant at 8°C during the dropwise addition process. The total amount added is 1.6 times the mass of the colostrum. After the dropwise addition is complete, continue stirring at low speed (120 rpm) at 8°C for 25 minutes. Under this pH and temperature window, the gelatin molecules are in an extended conformation. Their amino protonation degree is moderate. They generate directional electrostatic attraction with the negative charge on the surface of the colostrum droplets and spontaneously spread along the curvature of the droplets to form a monolayer protein adsorption film. The thickness of this adsorption film is about 2.3 nm. No molecular cross-linking occurs. It is anchored to the droplet interface only by van der Waals forces and hydrogen bonds, forming the first structural support for the subsequent complex coagulation reaction.

[0032] The primary emulsion system covered by a gelatin monolayer film becomes the sole precursor for the next stage of complex coagulation reaction. Its droplet integrity, film coverage, and interfacial charge density jointly determine whether the subsequent gum arabic can achieve effective docking and layering deposition. The entire system has moved beyond the category of simple emulsions and entered the preparatory state of ordered interfacial self-assembly.

[0033] Step 2: Directional Construction and Interface Locking of Complex Condensed Wall Material Layer Step 2.1: Prepare an aqueous solution of gum arabic (concentration 4.0%, pH adjusted to 7.0), remove impurities by vacuum filtration through a 0.45 μm filter membrane, and pre-cool to 8°C; slowly inject this solution into the gelatin-coated promulgation system obtained in step 1.4 using a constant flow pump, with a flow rate set at 0.6 mL / min, and the total amount added is 1.1 times the mass of the gelatin solution; under neutral to slightly alkaline conditions, the carboxyl groups of gum arabic molecules fully dissociate, carrying a strong negative charge, and form a trans-interfacial ion pair with the protonated amino groups in the gelatin adsorption layer, driving the two to undergo localized reverse charge compensation on the droplet surface, initiating the first round of molecular-scale interfacial contraction and densification.

[0034] As a result, a transition state appears on the droplet surface that is invisible to the naked eye but shows a systematic shift in the Zeta potential. The Zeta potential of the original gelatin layer gradually approaches zero from +18mV, indicating that gum arabic has substantially penetrated the aqueous diffusion boundary and undergone spatial matching electrostatic pairing with the gelatin side chains, rather than simple outer layer stacking. This process does not introduce any crosslinking agent and is driven purely by charge complementarity, so the interfacial bonding energy has a reversible temperature response characteristic.

[0035] Step 2.2: Immediately after the gum arabic is added, the pH of the system is slowly adjusted to 3.8 using 0.1 mol / L citric acid solution. The adjustment process lasts for 6 minutes, and the final pH is maintained within ±0.05. This pH transition causes the net charge of the gelatin molecules to change from positive to weakly positive or even near neutral, while the carboxyl groups of gum arabic are partially protonated, weakening their repulsive force and promoting the two to shift from electrostatic attraction to hydrophobic micro-region co-association. Nanoscale wrinkles begin to appear on the surface of the droplets, the film thickness increases from a single layer to about 8.5 nm, the refractive index increases, and the macroscopic manifestation of the system is enhanced opalescence and slightly reduced fluidity.

[0036] The pH-adjusted system was left to stand at 8°C for 18 minutes without any external stirring, relying solely on Brownian motion to maintain the suspension of the particles. During the standing process, the gelatin-gum arabic composite film under the constraint of droplet curvature completed the rearrangement of molecular chain segments, with hydrophobic residues shifting inward to the essential oil phase and hydrophilic residues extending outward to the aqueous phase, forming a bilayer structure with clear inner and outer phase segregation characteristics. This structure no longer relies on external charge balance for maintenance and is not easily disintegrated even with brief pH disturbances.

[0037] Step 2.3: Add modified starch suspension (solid content 2.8%, degree of substitution 0.32, made from hydroxypropylated potato starch, particle size) to the settled composite membrane colostrum at a mass ratio of 1:0.27 after ultrasonic dispersion for 3 minutes. The hydroxypropyl groups on the surface of starch granules impart weak lipophilicity, causing them to preferentially adsorb onto the hydrophobic microdomains on the outer side of the bilayer and connect with the free hydroxyl groups of gum arabic via hydrogen bonds. The adsorption process occurs spontaneously at 8°C without additional energy input, and a monolayer coverage is completed within 30 minutes, with a coverage rate of over 91%, forming a ternary heterogeneous interface structure.

[0038] Based on this, the ternary interface structure further reduces the surface free energy of the droplets, and the concentration of free starch particles in the aqueous phase drops below the detection limit. The absolute value of the Zeta potential of the system rises back to 12mV, indicating that the outer starch layer introduces a new steric hindrance effect, which makes up for the stability gap caused by the weakening of charge shielding after pH adjustment. At this time, the droplets have the ability to resist shear, resist dilution and have preliminary thermal resistance, providing structural redundancy for the next step of solidification.

[0039] Step 2.4: Transfer the ternary interface pre-emulsion system to a constant temperature reactor, purge with nitrogen for protection, and heat to 32°C at a rate of 0.3°C per minute. After reaching the target temperature, maintain the temperature for 22 minutes. This temperature range is below the starting point of gelatin thermal denaturation (34°C), but it is sufficient to activate the flexibility of gelatin molecular chain segments and promote the formation of more secondary hydrogen bonds and van der Waals contact points between gelatin and gum arabic and starch.

[0040] The thermotropically enhanced ternary composite membrane structure became the sole template for the subsequent cooling and solidification stage. Its network density, pore distribution, and interfacial adhesion strength directly determined the final density and stress transfer efficiency of the microcapsule shell. The entire system has completed the key leap from dynamic assembly to quasi-solid structure.

[0041] Step 3: Low-temperature induced phase separation and initial shell solidification Step 3.1: The heat-fortified ternary colostrum system obtained in Step 2.4 is cooled from 32℃ to 4℃ at a uniform rate of 0.25℃ per minute. The entire process is carried out under a nitrogen atmosphere, and the temperature is maintained at a constant temperature for 15 minutes at the end of the cooling process. The temperature drop causes the proportion of gelatin helical segments to increase, the molecular chains to shrink and pull the gum arabic and starch segments to undergo micro-conformation adjustments simultaneously. The intermolecular distance inside the ternary membrane layer decreases, the free volume decreases, the mobility of water molecules in the membrane layer gaps is restricted, and local micro-dehydration occurs.

[0042] As a result, submicron-scale water-depleted regions begin to form inside the membrane. These regions are not voids, but rather high-density nodes formed by polymer segments tightly filling the water molecules after they are forcibly squeezed out. The nodes are connected by water-containing microchannels, forming the prototype of a gradient mass transfer path that runs through the entire shell, reserving a structural basis for the subsequent directional and sustained release of essential oil molecules.

[0043] Step 3.2: At the end of the 4℃ isothermal stage, slowly add a polylactic acid (PLA) acetone solution (concentration 1.2%, acetone dried with anhydrous magnesium sulfate) to the system. The amount added is 0.19 times the total mass of the colostrum. The addition process lasts for 8 minutes. After the addition is complete, continue to stand at 4℃ for 12 minutes. Acetone, as a good solvent, rapidly diffuses into the aqueous phase, locally reducing the interfacial tension and promoting the selective adsorption of PLA molecular chain segments on the outer surface of the ternary film. Due to the strong hydrophobicity of PLA itself, its adsorption preferentially occurs in the aqueous-depleted region of the film, forming a block physical entanglement with the gelatin-gum arabic-starch network.

[0044] Acetone evaporates rapidly in the low-temperature aqueous phase (half-life of about 90 seconds). After losing solvent support, PLA molecules undergo chain segment collapse and embed themselves in the micro-depressions and wrinkles on the film surface, forming an epitaxial hydrophobic layer with a thickness of about 150-220 nm. This layer does not undergo covalent grafting, but due to its high topological fit, it forms a mechanical bond with the inner ternary film, significantly improving the overall shell's ability to block external water vapor and oxygen.

[0045] Step 3.3: The system with PLA adsorption completed is placed in a -12℃ ultra-low temperature cold trap for rapid freezing for 110 seconds, so that the system instantly passes through the ice crystal nucleation critical point. The aqueous phase precipitates in the form of micron-sized oriented ice crystals with the ice crystal growth direction perpendicular to the droplet surface. Uniform radial pressure is applied to the ternary-PLA composite film. This pressure causes the polymer chain segments of the film layer to undergo controllable sliding and reorientation along the ice crystal interface. The original microporous structure is compressed and elongated to form radially arranged slit-like channels with a channel width concentrated in the range of 8-15nm and a length extending to the full thickness of the film layer.

[0046] Based on this, the stress imprint formed by ice crystals in the film layer does not destroy the structural integrity, but instead makes the interface of each component more tightly bonded. After thawing, the ice crystals disappear, but the pore morphology is preserved by the elastic memory of the polymer network, becoming the main channel for the later release of essential oil molecules. At this time, the shell layer has a clear directional pore structure, which is different from the traditional random porous system.

[0047] Step 3.4: The frozen sample was quickly transferred into a vacuum drying oven and dried at 5°C and 80 Pa absolute pressure for 4.5 hours to remove residual acetone and free water simultaneously. During the drying process, the PLA segments further relaxed and filled the asymmetric gaps at the edges of the channels. Gelatin and gum arabic underwent slight dehydration condensation due to dehydration, while the starch hydroxypropyl side chains bridged adjacent polymer chains through hydrogen bonds. The final shell thickness stabilized at 480-530 nm. Cross-sectional electron microscopy revealed three clear interfaces: an inner gelatin-dominated layer, a middle gum arabic-starch interpenetrating layer, and an outer PLA continuous covering layer.

[0048] The dried microcapsule precursor suspension enters the next stage—crosslinking enhancement. Its shell has acquired the triple characteristics of pore orientation, component gradient, and structural memory. Any local damage will trigger stress redistribution throughout the entire layer, rather than the expansion of isolated defects.

[0049] Step 4: Glutaraldehyde vapor phase crosslinking and shell function shaping Step 4.1: The dried microcapsule suspension obtained in Step 3.4 is evenly coated on the surface of a clean polytetrafluoroethylene tray to form a thin layer with a thickness of about 0.8 mm. The tray is then placed in a sealed cross-linking chamber. An open ceramic dish containing a 25% glutaraldehyde aqueous solution is placed in the chamber beforehand. The surface area of ​​the dish is 1:140 of the chamber volume. The tray is allowed to stand for 30 minutes to allow the glutaraldehyde vapor concentration in the chamber to reach saturation (about 210 ppm). The glutaraldehyde molecules are evenly dispersed in a gaseous state, avoiding direct contact between the liquid phase and the shell, which could cause local swelling or leakage of essential oils.

[0050] Thus, glutaraldehyde vapor molecules slowly penetrate into the interface between the outer layer PLA and the middle layer starch of the shell, preferentially reacting with the ε-amino groups of lysine and hydroxyproline residues in the gelatin molecules to form imine bonds. The rate of this reaction is controllable under low-temperature and dry conditions, without triggering violent exothermic reactions or pH changes. The reaction depth is limited to within 200 nm outside the shell, and the inner essential oil phase is completely unaffected.

[0051] Step 4.2: Maintain a constant glutaraldehyde vapor concentration in the chamber and slowly raise the temperature to 16°C over 14 minutes. Then, continue crosslinking at this temperature for 2 hours. The moderate temperature increase accelerates the imine bond formation rate, but remains below the gelatin denaturation threshold, ensuring that the reaction only occurs at the molecular chain end groups and does not trigger large-scale crosslinking network collapse. After crosslinking, the Young's modulus of the shell increases by about 37%, but the elongation at break remains above 42%, indicating that the network has both rigidity and toughness.

[0052] The cross-linking reaction creates sparse but uniform covalent connections between gelatin molecular chain segments. These connections act like anchors embedded in the gum arabic-starch interpenetrating network, transforming the originally loosely stacked ternary structure into a cohesive whole. Although the outer layer of PLA does not directly participate in the reaction, its barrier performance is enhanced due to the stronger bonding with the inner layer interface, resulting in a decrease in the water molecule permeability coefficient by an order of magnitude.

[0053] Step 4.3: After cross-linking is completed, remove the tray and place it in a fume hood to allow the residual glutaraldehyde odor to dissipate naturally for 35 minutes. Then, purge the surface of the tray with high-purity nitrogen for 10 minutes to completely remove physically adsorbed glutaraldehyde molecules. After purging, scrape off the thin layer of microcapsules and transfer it into an aluminum foil sealed bag. Store it at 4°C in the dark. Under this storage condition, the shell cross-linking structure is in a thermodynamic metastable state, and the imine bond reversibility is retained, providing molecular-level adjustment space for the sustained-release kinetics under humid conditions during subsequent use.

[0054] Based on this, the microcapsule powder exhibits a free-flowing dynamic, without agglomeration, with a tap density of 0.38 g / cm³, and the particle surface is smooth without obvious cracks or protrusions.

[0055] Step 4.4: Take a portion of the preserved sample and place it in a constant humidity and temperature chamber at 65% relative humidity and 25℃ to simulate daily storage conditions. Take samples periodically for observation. After 72 hours, the shape of the microcapsules remained unchanged, and the aroma intensity remained at 98.2% of the initial value, indicating that the cross-linked shell layer had effectively inhibited the initial burst release of essential oils. At this time, the essential oil inside the shell layer was still in a highly bound state and only exuded at the molecular level through the directional slit channels formed in step 3.3. The release flux was synergistically regulated by the channel geometry parameters and the ambient humidity, rather than simply relying on the concentration gradient.

[0056] This microcapsule product has the basic physical properties for practical applications: structural integrity, environmental adaptability, aroma retention and release controllability are unified. Its release behavior no longer depends on the intensity of external stimuli, but is dominated by the intrinsic mass transfer pathway defined by its own multi-level shell structure.

[0057] Step 5: Reconstruction of the aqueous dispersion system and establishment of long-term suspension stability Step 5.1: Weigh out the microcapsule dry powder that has undergone constant humidity and temperature pre-exposure treatment in step 4.4 according to a solid content of 3.2%, and slowly sprinkle it into deionized water pre-cooled to 6°C. The sprinkling process lasts for 7 minutes. During this period, the water surface is disturbed by low-speed magnetic stirring (80 rpm) but splashing is avoided. After the powder comes into contact with cold water, the surface PLA layer shrinks instantly, forming a weak hydrophobic barrier to prevent water from quickly penetrating into the shell. The initial wetting rate is controlled to a penetration depth of no more than 120 nm per minute to ensure that the core material oil does not undergo interfacial stress mismatch due to water absorption and swelling.

[0058] Thus, the microcapsule particles gradually complete the transition from a dry state to a hydrated state in the aqueous phase, and the surface tension gradient is released layer by layer from the outside to the inside without any bursting, leakage or agglomeration. The average residence time of the particles on the liquid surface is 23 seconds, which is much higher than the 5 seconds of conventional uncrosslinked microcapsules, indicating that the shell formed by vapor phase crosslinking has the initial hydration and impact resistance.

[0059] Step 5.2: After all the powder has settled below the liquid surface, the system is transferred to a constant-temperature ultrasonic bath and subjected to intermittent ultrasonic treatment at 6°C with a frequency of 40kHz and a power density of 0.8W / cm². Each pulse lasts 0.8 seconds with an interval of 1.2 seconds, for a total duration of 14 minutes. The ultrasonic energy only acts on the micro-bubbles and micron-sized impurities adsorbed on the particle surface, without damaging the covalent network of the shell layer, nor inducing PLA remelting or gelatin decrosslinking. After treatment, more than 99.4% of the particles detach from the aggregates, returning to a monodisperse state, and the Zeta potential rises to [value missing]. 24mV indicates that the starch hydroxypropyl side chain is fully extended, providing a stable steric hindrance barrier.

[0060] The physical agglomeration disintegrated by the ultrasonic treatment is not due to electrostatic neutralization, but rather to temporary capillary bridging caused by the sluggish diffusion of water molecules at low temperatures. Once the bridging breaks, the particles rebuild an independent hydration layer based on their own surface modification layer, without the need for additional dispersing agents, and the system enters a self-stable dispersion preparatory state.

[0061] Step 5.3: Add sodium carboxymethyl cellulose (CMC-Na, degree of substitution 0.72, viscosity 350 mPa·s) to the ultrasonically treated dispersion at a mass ratio of 0.013:1. The addition method is to first dissolve it in an equal volume of pre-cooled deionized water to prepare a 2.0% mother liquor, and then inject it at a uniform rate using a peristaltic pump for 8 minutes. The CMC-Na molecular chain has high extension at low temperature. Its carboxyl groups form weak hydrogen bond anchors with the small amount of amino and hydroxyl groups remaining on the shell surface, and the main chain extends outward to form a flexible hydration brush layer with a thickness of about 35 nm. This brush layer does not change the original principal value of the Zeta potential, but significantly improves the orientation stability of the particles in the shear field.

[0062] Based on this, the hydration brush layer makes the particles insensitive to temperature fluctuations during subsequent storage: when the ambient temperature changes periodically within the range of 4-28℃, the brush layer dynamically adjusts the hydration thickness through chain segment contraction and expansion to offset the accumulation of interfacial stress caused by thermal expansion and contraction; after the dispersion is left to stand at 4℃ for 30 days, the bottom sedimentation rate is less than 0.17% and the turbidity change of the supernatant is less than 2.3 NTU, confirming that the long-term suspension capacity is endogenous in the system itself.

[0063] Step 5.4: Transfer the CMC-Na modified dispersion into a sealed stainless steel container, purge with nitrogen three times, and stir at a constant speed of 150 rpm for 2 hours. Then stop stirring and let it stand and mature in a dark room at 4°C for 48 hours. During maturation, the CMC-Na brush layer and shell layer surface undergo slow interfacial interpenetration, and some sugar units are embedded in the interstices of starch hydroxypropyl groups to form a physical entanglement network. This network does not have covalent strength, but it gives the dispersion thixotropic properties—it is in a weak gel state when standing, and it recovers its fluidity when gently shaken, without water separation or stratification.

[0064] The matured dispersion becomes the unified intermediate for all subsequent terminal adaptation processes. Its rheological behavior, particle size distribution stability, and interfacial response characteristics are all fixed and will not change qualitatively with batch operation fine-tuning. Any subsequent dilution, mixing, or drying operations shall take this matured state as the sole reference starting point.

[0065] Step Six: Particle Size Classification and Morphology Homogenization Step 6.1: Take the matured dispersion obtained in step 5.4, filter it through a 5μm stainless steel screen, and then introduce it into a centrifugal particle size classifier. Set the rotation speed to 8200rpm, the feed flow rate to 1.4L / h, and the separation time to 22 minutes. The equipment has a built-in double cone angle separation chamber. In the centrifugal force field, larger particles (>12.5μm) are dominated by inertia and settle along the outer wall, while smaller particles (<8.3μm) rise and are discharged with the inner liquid flow. The target particle size range in the middle section (9.0-11.8μm) forms a stable ring at a specific radial position and is independently discharged.

[0066] Therefore, the target particle size component accounted for 68.3% of the total original dispersion. The value decreased by 0.29 compared to before grading; this size window ensures sufficient embedding capacity and meets the penetration and spreading requirements of most matrices (such as emulsions, creams, and sprays) for dispersed phase particle size.

[0067] Step 6.2: Immediately transfer the target particle size dispersion obtained from the classification into a microporous ceramic membrane filtration system. Use a flat sheet membrane with a pore size of 0.42 μm and a porosity of 63% for dynamic filtration under the conditions of a transmembrane pressure difference of 45 kPa and a cross-flow velocity of 0.6 m / s. Collect the filtrate as the finished dispersion and return the retentate to the classifier for recycling. The ceramic membrane surface is silanized, has moderate hydrophilicity, and does not adsorb microcapsules. The filtration process only removes free CMC-Na macromolecular aggregates and trace amounts of broken shell fragments without damaging intact particles.

[0068] After filtration, the concentration of free polymers in the dispersion was reduced to below the detection limit, and the particle surface was not covered with a non-specific polymer layer. The original CMC-Na brush layer structure was completely preserved. Under an optical microscope, more than 99.8% of the particles had clear outlines and sharp edges, without tailing, haloing or film-like residues, confirming that the surface morphology was not damaged by mechanical shearing.

[0069] Step 6.3: The filtered dispersion is pumped into a static mixer at a constant flow rate, and a 0.08% phytic acid aqueous solution (pH 2.4) is injected simultaneously at a volume ratio of 100:1.3. The total residence time after mixing is 19 seconds. Phytic acid molecules contain six phosphate groups, which are partially protonated under weakly acidic conditions. They can coordinate with calcium and sodium ions remaining on the shell surface to form transient ion bridges, resulting in a weak and reversible short-range attraction between adjacent particles. This attraction is insufficient to induce aggregation, but it can suppress random collision deflection caused by Brownian motion and improve the stacking regularity of particles in the subsequent drying process.

[0070] Based on this, the existence window of the ion bridge is strictly limited to within 30 seconds after mixing. Subsequently, due to the system's buffering capacity, the bridge spontaneously dissociates. This brief regulation does not change the overall distribution of the particle zeta potential, nor does it introduce foreign metal ion contamination. It serves only as a physical guiding means to support the next step of drying morphology control.

[0071] Step 6.4: Immediately feed the dispersion guided by the ion bridge into the spray drying tower. The inlet air temperature is 112℃, the outlet air temperature is 58℃, the atomization pressure is 180kPa, and the tower is under negative pressure. 85Pa; the droplets undergo millisecond-level dehydration in the hot air, the surface PLA layer first densifies to form a rigid shell, the internal water phase slowly migrates to the surface, driving the gelatin-gum arabic-starch layer to shrink synchronously, the final particle shrinkage ratio is 1:1.82, and the surface forms uniform micro-folds without cracks, depressions or cavities.

[0072] The resulting dry microcapsule powder exhibits a free-flow dynamic with a repose angle of 32° and a compressibility of 12.4%. Scanning electron microscopy shows a sphericity >0.96, and surface wrinkles concentrated in the wavelength range of 380-450 nm with a depth of 45-62 nm. This microstructure is not randomly formed, but is determined by the directionality of water flow inside the droplets guided by the ion bridge in step 6.3 and the solvent migration path driven by the thermal gradient in step 6.4, forming another structural basis for the sustained-release behavior.

[0073] Step 7: Surface hydrophobic enhancement and environmentally responsive modification Step 7.1: Spread the spray-dried powder obtained in step 6.4 evenly in a rotating fluidized bed, and introduce compressed air dried with silica gel to make the particles uniformly suspended; then spray an octadecyltriethoxysilane (OTES) ethanol solution (concentration 0.27%) in the form of an aerosol for 11 minutes. After spraying, continue fluidized drying for 16 minutes to allow OTES molecules to undergo hydrolysis and condensation on the particle surface to generate an alkylsiloxane monolayer with a thickness of about 4.2 nm.

[0074] Thus, the OTS layer is firmly grafted by the condensation of silanol groups with the hydroxyl groups on the shell surface, and its long-chain alkyl groups are arranged vertically outward, which reduces the surface energy of the particles from 42.6 mJ / m² to 21.3 mJ / m² and increases the water contact angle to 108°. This modification does not block the directional slit channels formed in step 3.3. Because the size of OTS molecules is much smaller than the width of the channels, it only covers the edge of the channels, which reduces the surface energy of the inner wall of the channels and slows down the adsorption and retention of essential oil molecules in the channels.

[0075] Step 7.2: Transfer the OTS-modified powder into a vacuum oven and maintain it at 60 Pa and 45 °C for 3 hours to promote the complete hydrolysis of unreacted ethoxy groups and further densify the silicon-oxygen network; the heating process causes micro-rearrangement of OTS segments, increases the crystallinity of alkyl side chains, and enhances the scratch resistance of the hydrophobic layer; at this time, after the particles are soaked in an aqueous solution of pH 3-10 for 24 hours, the OTS layer detachment rate is less than 0.8%, confirming that the covalent anchoring is firm.

[0076] Step 7.3: Cool the baked powder to room temperature and place it in an environment with a relative humidity of 85% for 18 hours to allow the residual trace moisture in the shell to reach adsorption saturation; then quickly transfer it to a -18℃ freezer for deep cryogenic treatment for 90 minutes, and then allow it to naturally warm to room temperature at 25℃; this freeze-thaw cycle induces elastic deformation of the microporous structure in the shell, and the OTS layer undulates slightly with the substrate, forming nanoscale stress wrinkles. The wrinkle spacing is an integer multiple of the surface macro-wrinkles in step 6.4.

[0077] Based on this, stress wrinkles cause periodic changes in the local thickness of the OTS layer, with thicker areas exhibiting stronger hydrophobicity and thinner areas retaining moderately hydrophilic channels. This structure does not change the overall hydrophobicity level, but it changes the spreading behavior of water molecules on the shell surface from uniform wetting to island-like wetting, thereby regulating the rate of water phase propagation into the pores and providing a humidity-gated effect for aroma release.

[0078] Step 7.4: Sieve the freeze-thawed powder through a 200-mesh nylon sieve to remove any trace clumps caused by the freeze-thaw process; pack the sieved material into an aluminum-plastic composite film bag, evacuate to an absolute pressure ≤150Pa, and then heat-seal; during the sealing process, residual moisture inside the bag forms a monomolecular adsorption layer on the surface of the OTS layer. This layer remains stable during storage, inhibiting the impact of sudden changes in external moisture on the shell layer, ensuring that the microcapsules are always in a pre-hydration equilibrium state before opening the bag.

[0079] The packaged product is ready to use: it can be directly placed into various substrates after opening without pretreatment. Its release kinetic curve deviates from the measured value before packaging by less than ±3.2%, indicating that surface modification and packaging process together construct a full-cycle performance conservation mechanism from the end of production to the start of use.

[0080] Step 8: Terminal matrix adaptation and release behavior calibration Step 8.1: Take the encapsulated microcapsule powder from Step 7.4 and mix it with molten petrolatum (75°C) at a mass ratio of 1:4.5. Stir at 160 rpm for 5 minutes, then cool to 45°C and maintain for 12 minutes to allow the microcapsules to be uniformly dispersed and partially embedded in the petrolatum continuous phase. At this temperature, the petrolatum molecular chain segments have sufficient fluidity to penetrate into the micro-folds of the OTS layer on the surface of the microcapsules, forming a physical interlock, but without dissolving PLA or destroying the shell cross-linking structure.

[0081] As a result, the microcapsules are fixed in position in the oil phase, neither settling nor floating, and the shear viscosity is increased by 18%, giving the system a uniform creamy texture. Vaseline, as an inert carrier, does not participate in the release process, but only provides a diffusion resistance field, so that essential oil molecules must pass through the Vaseline layer before reaching the skin surface, thus prolonging the apparent release time.

[0082] Step 8.2: Add a beeswax-microcrystalline wax mixture (beeswax:microcrystalline wax = 3:2) to the above petrolatum dispersion system at 0.9% of the mass of the microcapsules. Stir at 45°C for 8 minutes until completely melted, then cool to 32°C at a rate of 0.4°C per minute and keep warm for 1 hour. When the wax component crystallizes, it forms a microporous network framework around the microcapsules. The pore size of this framework is concentrated in the range of 0.8-1.3μm, which matches the size of the microcapsules. This does not restrict the diffusion of essential oils, but also prevents them from being released in bursts at body temperature.

[0083] The wax skeleton and petrolatum together form a double resistance layer: the inner petrolatum provides molecular-level diffusion hindrance, and the outer wax skeleton provides micron-level path constraint; the two work together to ensure that after the essential oil molecules are released from the microcapsule channels, they need to undergo two detours of different scales, and the release flux curve shows a typical double plateau characteristic.

[0084] Step 8.3: Pour the wax-petroleum jelly composite system into the mold and cure it in a constant temperature room of 22°C for 24 hours. After demolding, you will get a solid fragrance block.

[0085] Step 8.4: Mix the same batch of microcapsule powder with deionized water at a mass ratio of 1:12, add 0.15% xanthan gum to thicken, prepare a water-based spray dispersion, fill it into a pressure tank, and fill it with propellant (dimethyl ether:propane = 7:3); the average particle size of the microcapsules in the sprayed droplets is 18.7 μm. After being deposited on the fabric surface, the OTS layer and the hydroxyl groups on the fiber surface have a weak interaction, which increases the particle adhesion rate to 92.4%. After drying, a breathable film is formed.

[0086] In summary, this invention constructs a microcapsule structure with intrinsic mass transfer regulation capabilities through stepwise assembly of multi-component wall materials, low-temperature induced channel orientation, enhanced network stability brought about by vapor phase crosslinking, and diffusion barriers formed by surface hydrophobic modification.

[0087] As a result, the essential oil is effectively confined to the core and can only migrate slowly to the outside in a specific direction after experiencing multiple resistances. The aroma output no longer depends on the intensity of external stimuli, but is determined by the structure itself, thus achieving a stable, uniform, and long-lasting aroma release from the moment it is activated.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for preparing sustained-release star anise essential oil microcapsules, characterized in that, include: S1: After star anise essential oil is left to stand in the dark, take the upper clear phase and add anhydrous ethanol to mix. Add the mixture dropwise to a sodium hydrogen phosphate aqueous solution, and then cool it in an ice water bath after high-speed shearing to form a colostrum. S2: Add gelatin aqueous solution to colostrum to form an adsorption film, then add gum arabic aqueous solution, adjust the pH value, and let stand to form a composite film; S3: Add modified starch suspension to the composite membrane colostrum, heat up and then cool down to form a ternary composite membrane; S4: Add polylactic acid acetone solution to the ternary composite membrane, freeze-dry it under vacuum to form a shell, crosslink the dried product with glutaraldehyde vapor phase to form a crosslinked shell, disperse the crosslinked product in cold water, add sodium carboxymethyl cellulose to mature and form a dispersion. S5: The dispersion is subjected to particle size classification, filtration and spray drying to obtain microcapsule powder. The microcapsule powder is then treated with octadecyltriethoxysilane and adapted to petrolatum or water-based systems to form end products.

2. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S1, the upper clear phase is transferred to a nitrogen-purged sealed container; the dropping rate is 0.8 mL per minute; high-speed shearing is performed at 8000 rpm for 90 seconds; and the liquid is cooled to 8°C in an ice-water bath and maintained for 12 minutes to reduce the kinetic energy of the essential oil molecules inside the droplets.

3. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S2, the gelatin aqueous solution concentration was 3.5% and the pH was 4.2; the gum arabic aqueous solution concentration was 4.0% and the pH was 7.0; the pH was adjusted to 3.8 using 0.1 mol / L citric acid solution; and the mixture was allowed to stand for 18 minutes to allow the gelatin-gum arabic composite membrane to complete the molecular chain rearrangement.

4. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S3, the modified starch suspension has a solid content of 2.8% and a degree of substitution of 0.32; the heating rate is 0.3℃ per minute to 32℃ and held for 22 minutes; the cooling rate is 0.25℃ per minute to 4℃ and held for 15 minutes; during the cooling process, a water-depleted region is formed inside the ternary composite membrane.

5. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S4, the concentration of polylactic acid acetone solution was 1.2%; the amount added was 0.19 times the total mass of the colostrum; freezing at -12℃ for 110 seconds caused the aqueous phase to precipitate in the form of micron-sized oriented ice crystals; vacuum drying was carried out at 5℃ and 80Pa for 4.5 hours.

6. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S4, the glutaraldehyde vapor concentration was 210 ppm; the surface area to volume ratio of the open ceramic dish was 1:140; crosslinking was performed at 16°C for 2 hours; after crosslinking, ventilation was carried out for 35 minutes and high-purity nitrogen was purged for 10 minutes.

7. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S4, the dispersed solids content is 3.2%; the cold water temperature is 6℃; the amount of sodium carboxymethyl cellulose added is 0.013 times the mass of the dispersion; and the sodium carboxymethyl cellulose is aged at 4℃ for 48 hours to allow interfacial interpenetration between the sodium carboxymethyl cellulose brush layer and the shell surface.

8. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S5, the centrifugal classification speed is 8200 rpm, the feed flow rate is 1.4 L / h, and the particle size fraction of 9.0-11.8 μm is collected; the ceramic membrane pore size is 0.42 μm; the spray drying inlet air temperature is 112℃, the outlet air temperature is 58℃, and the atomization pressure is 180 kPa.

9. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S5, the concentration of octadecyltriethoxysilane ethanol solution was 0.27%; fluidized bed treatment for 11 minutes; vacuum treatment at 45°C and 60Pa for 3 hours; freeze-thaw cycle at 85% humidity for 18 hours, freeze at -18°C for 90 minutes, and thaw at 25°C.

10. The method for preparing a sustained-release anise essential oil microcapsule according to claim 1, characterized in that, In S5, the petrolatum is mixed at a ratio of 1:4.5, mixed at 75°C for 5 minutes, and maintained at 45°C for 12 minutes; the beeswax-microcrystalline wax mixture is 0.9% of the microcapsule mass, with a beeswax:microcrystalline wax ratio of 3:2; the water-based system microcapsules are mixed with deionized water at a ratio of 1:12, and 0.15% xanthan gum is added; the fragrance block is cured at 22°C for 24 hours; and the water-based spray filler is filled with a dimethyl ether:propane propellant ratio of 7:3.

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