RS3 microcapsule sealing process

Abstract

The application discloses a microcapsule sealing process and belongs to the technical field of microcapsules. The process is used for sealing treatment of porous RS3 microspheres loaded with active substances, and the porous RS3 microspheres are prepared by using resistant starch with a melting temperature greater than or equal to 120 DEG C as a base material in a pure physical way. The sealing treatment adopts a physical coating or physical fusion mode and does not involve a chemical cross-linking reaction. The physical coating is to coat a coating material on the outer surface of the microspheres to form a sealing film; the physical fusion is to make the surface particles of the RS3 resistant starch fuse with each other to form a continuous and dense sealing film under specific temperature and humidity conditions by using the self-surface fusion characteristics of the RS3 resistant starch, and no additional coating material is needed. After the sealed microspheres are boiled in 100 DEG C boiling water for 30 minutes, the structure integrity rate is not less than 80%, and the microspheres remain in an independent and dispersed state. The application is pure physical, no chemical residues are left, and is suitable for fields such as food and medicine which have strict safety requirements.

Description

Technical Field

[0001] This invention belongs to the field of microcapsule technology, specifically relating to a process for sealing porous microspheres loaded with active substances. Background Technology Microencapsulation technology is widely used in the food, pharmaceutical, daily chemical, and agricultural fields. In a typical microcapsule preparation process, after the active substance is loaded into a carrier, the carrier usually needs to be sealed to prevent premature leakage of the active substance during subsequent processing, storage, or use. The existing sealing process has the following main problems: (1) Chemical cross-linking sealing poses safety hazards. Glutaraldehyde, sodium trimetaphosphate, and other chemical cross-linking agents are commonly used to cross-link and solidify the wall material for sealing, but the residue of these cross-linking agents poses a risk to food safety and biocompatibility. (2) Physical melt sealing has stringent material requirements. Some lipid wall materials can be sealed by hot melting and cooling, but their heat resistance is poor and they cannot withstand subsequent high-temperature processing. Ordinary starch-based wall materials have low melting temperatures and are prone to overall collapse and deformation or particle adhesion during temperature and humidity fusion treatment. (3) Coated sealing has poor compatibility with the core material. Some coating materials have weak bonding with the microsphere substrate and are prone to falling off in the processing or digestion environment. Therefore, there is an urgent need in this field for a sealing process that is purely physical, does not introduce chemical cross-linking agents, and allows the microspheres to remain independently dispersed after sealing while also possessing high temperature resistance, stomach acid resistance, and digestive resistance. Summary of the Invention This invention relates to an independent microcapsule sealing process, distinct from complete encapsulation methods that include a loading step. This invention focuses solely on the sealing process itself and is independent of the specific active substance loading method. This sealing process can be implemented independently in different scenarios and can be used as an independent process module in conjunction with various loading methods. The purpose of this invention is to provide a microcapsule sealing process for sealing porous microspheres loaded with active substances. The porous microspheres are made from resistant starch prepared purely physically, with a melting temperature (peak temperature determined by DSC) ≥120℃ as the substrate, and contain multiple micron-sized cavities. In this specification, the resistant starch refers to a known, commercially available resistant starch manufactured by purely physical means. The resistant starch has a melting point ≥120°C as determined by DSC and has been confirmed in in vitro simulated digestion experiments not to be hydrolyzed by small intestinal digestive enzymes. It is manufactured by purely physical means and contains no chemical cross-linking agents or biological enzyme residues. The sealing process provided by this invention is a physical sealing treatment that does not involve any chemical cross-linking reaction. It is achieved through one of the following methods: (a) Physical coating: Coating material is applied to the outer surface of microspheres by dip coating, spraying, or fluidized bed coating to form a sealing film. The coating material can be selected from food-grade materials such as hydroxypropyl methylcellulose (HPMC), sodium alginate, pectin, pullulan, and zein. The amount of coating material used is to increase the weight of the microsphere coating by 3%-15% after sealing, preferably 5%-10%. (b) Physical fusion: Utilizing the surface fusion characteristics of RS3 resistant starch under conditions of 60℃-80℃ and 70%-90% relative humidity, the process is carried out for 10 to 40 minutes to allow the starch particles on the surface of the microspheres to fuse together and form a continuous and dense sealing film. Physical fusion does not require the addition of additional coating material and is a preferred solution for pure physical sealing. In the physical fusion sealing process, the melting temperature of RS3 resistant starch (≥120℃) plays a crucial role. This temperature is significantly higher than the operating temperature for physical fusion, ensuring that the overall structure of the microspheres remains intact and does not collapse, while the surface particles undergo moderate softening and fusion under humid and hot conditions. In stark contrast, ordinary starch, due to its low gelatinization temperature, will gelatinize and disintegrate or experience severe interparticle adhesion under the same conditions. Therefore, the high melting point of RS3 resistant starch makes physical fusion sealing possible—it can form a dense surface sealing film while maintaining the independent dispersion of the microspheres. Those skilled in the art should understand that using hot steam to treat the surface of microspheres instantly, causing the surface starch particles to fuse rapidly to achieve sealing, is an equivalent alternative to the physical fusion sealing method of this invention and should also fall within the protection scope of this invention. After being sealed, the microspheres remained structurally intact for 30 minutes in boiling water at 100°C, with a structural integrity rate of no less than 80%. The sealed microspheres maintained an independently dispersed state, without sticking together, and the product was a free-flowing powder. Beneficial effects Compared with the prior art, the present invention has the following advantages: (1) Purely physical process. No chemical cross-linking reaction is involved, and no characteristic peaks of chemical cross-linking agents are detected in the infrared spectrum of the product, making it suitable for high safety requirements such as food and medicine. (2) Excellent sealing effect. After sealing, the microspheres can withstand boiling water at 100℃ for 30 minutes, and the structural integrity rate is not less than 80%. (3) Independent dispersion of microspheres. After physical fusion sealing, the microspheres do not stick together, and the product can flow freely, which is convenient for subsequent processing and use. (4) Simple process. Physical fusion sealing does not require additional coating materials, reducing raw material costs and process steps, and is suitable for industrial continuous production. (5) Two sealing methods are flexibly selectable. Physical coating or physical fusion can be selected according to product positioning and cost requirements, neither of which involves chemical cross-linking. Detailed Implementation The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. In the following embodiments, the porous microspheres used were all prepared by purely physical methods using resistant starch as the substrate, with a melting temperature (peak temperature determined by DSC) ≥120℃. The average particle size of the microspheres was approximately 50 μm, the average pore size of the internal cavities was 0.5 μm-20 μm, and the BET specific surface area was 25-35 m² / g. After incubation in simulated gastric juice at pH 1.2 at 37℃ for 4 hours, the solid mass retention rate of the porous microspheres was ≥90%; after incubation in simulated small intestinal digestive fluid (containing α-amylase, pH 6.8, 37℃) for 2 hours, the mass loss rate was less than 5%. The loading of the active substance was completed before sealing, and conventional methods such as immersion adsorption and vacuum-assisted impregnation could be used. Example 1 – Physical Coating Sealing (HPMC Coating): 100g of porous microspheres loaded with chicken oil (approximately 42g chicken oil loading per 100g microspheres) were placed in a fluidized bed coating machine. A 2% (w / w) HPMC aqueous solution was prepared as the coating liquid. The coating process parameters were: inlet air temperature 60℃, spray rate 5mL / min, material temperature controlled between 40℃ and 50℃, and coating weight gain controlled at 8%. After coating, the microcapsules were dried at 60℃ until the moisture content was below 13%. The product was a free-flowing powder, and the microspheres did not stick together. After boiling in water at 100℃ for 30 minutes, the chicken oil retention rate was 88.3%, and the structural integrity rate was 92.1%. Example 2 – Physical Fusion Sealing (Probiotic Microspheres) Take 50g of porous microspheres loaded with lyophilized lactic acid bacteria powder (live bacteria loading approximately 3.5 × 10¹). 0 The microspheres (CFU / g) were spread evenly in a temperature and humidity controlled chamber. They were treated at 60℃ and 80% relative humidity for 20 minutes to allow the starch granules on the surface to fuse and form a sealing film. After treatment, they were dried at 40℃ until the moisture content was below 10%. The product was a free-flowing powder, and the microspheres did not stick together. After incubation at 37℃ for 4 hours in simulated gastric juice (pH=1.2), the viable bacteria survival rate of the sealed probiotic microspheres was 82.5%; after further incubation in simulated small intestinal digestive fluid for 2 hours, the survival rate was 76.1%. Example 3 – Physical Fusion Sealing (Vitamin E Microspheres): 80g of porous microspheres loaded with vitamin E acetate (approximately 18.5g of vitamin E per 100g microspheres) were laid flat in a temperature and humidity controlled chamber. The microspheres were treated at 65°C and 85% relative humidity for 15 minutes to allow the starch granules on the surface to fuse and form a sealing film. After treatment, the microspheres were dried until the moisture content was below 12%. The product was a free-flowing powder, and the microspheres did not stick together. After boiling in water at 100°C for 30 minutes, the vitamin E retention rate was 91.7%. Comparative Example – Physical Fusion Sealing of Ordinary Corn Starch Porous Microspheres: Ordinary corn starch porous microspheres loaded with lyophilized lactic acid bacteria powder were subjected to physical fusion sealing under the same process conditions as in Example 2 (temperature 60°C, relative humidity 80%, processing time 20 minutes). The particle size and cavity structure of these ordinary corn starch porous microspheres were comparable to the RS3 microspheres used in Example 2. Results: Ordinary corn starch porous microspheres showed significant agglomeration and adhesion after treatment, with most microspheres sticking together and unable to maintain a free-flowing state. Scanning electron microscopy revealed that the surface of ordinary starch microspheres was excessively softened and deformed, with adjacent microspheres fusing and adhering together. In contrast, the RS3 microspheres of Example 2, under the same conditions, showed moderate surface fusion to form a continuous and dense sealing film, but the microspheres remained independently dispersed and did not agglomerate. The above comparison confirms that RS3 resistant starch, with a melting temperature ≥120℃, far exceeds the physical fusion operation temperature, enabling it to maintain overall structural integrity while achieving moderate surface fusion, thus preventing particle adhesion. This is a key technological advantage that ordinary starch cannot achieve, and it is also the fundamental reason for the success of the physical fusion sealing process of this invention.

Claims

1. A microcapsule sealing process, characterized in that, The process involves sealing porous microspheres loaded with active substances. The porous microspheres are made from resistant starch prepared by purely physical means, with a melting temperature (peak temperature determined by DSC) ≥120℃ as the substrate, and have multiple micron-sized cavities inside. The sealing process is a physical sealing process that does not involve chemical cross-linking reactions and is achieved through one of the following methods: (a) physical coating: coating material is applied to the outer surface of the microspheres to form a sealing film; (b) physical fusion: the microspheres loaded with active substances are treated under specific temperature and humidity conditions to fuse the starch particles on the surface of the microspheres to form a continuous and dense sealing film.

2. The sealing process according to claim 1, characterized in that, The porous microspheres retained ≥90% of their solid mass after incubation for 4 hours in simulated gastric juice at pH 1.2 and 37°C; and lost less than 5% of their mass after incubation for 2 hours in simulated small intestinal digestive fluid (containing α-amylase, pH 6.8, 37°C).

3. The sealing process according to claim 1, characterized in that, The physical coating described in method (a) is selected from at least one of dip coating, spray coating, and fluidized bed coating.

4. The sealing process according to claim 3, characterized in that, The coating material is selected from at least one of hydroxypropyl methylcellulose, sodium alginate, pectin, pullulan, and zein.

5. The sealing process according to claim 4, characterized in that, The amount of coating material used is such that the weight gain of the microsphere coating after sealing is 3%-15%.

6. The sealing process according to claim 3, characterized in that, The process parameters for fluidized bed coating are: inlet air temperature 50℃-75℃, spray rate 2-10mL / min, and material temperature controlled at 35℃-55℃.

7. The sealing process according to claim 1, characterized in that, The specific temperature and humidity conditions described in method (b) are: temperature 60℃-80℃, relative humidity 70%-90%, and processing time 10 to 40 minutes.

8. The sealing process according to claim 7, characterized in that, When the temperature is below 40℃, the starch granules do not undergo surface fusion; when the temperature is above 90℃, the microsphere structure deforms; when the relative humidity is below 50%, fusion is insufficient; when the relative humidity is above 95%, the granules stick together; when the processing time is less than 5 minutes, the sealing is incomplete; when the processing time exceeds 2 hours, the microsphere structure becomes brittle.

9. The sealing process according to claim 7, characterized in that, After the physical fusion sealing treatment, the resulting microspheres remain independently dispersed, do not stick together, and the product is a free-flowing powder.

10. The sealing process according to claim 1, characterized in that, The resistant starch has a melting temperature of ≥120℃, which allows it to maintain the integrity of the overall structure while being moderately fused on the surface under physical fusion sealing conditions, thus preventing the particles from sticking together.

11. The sealing process according to any one of claims 1 to 10, characterized in that, After being sealed, the microspheres were boiled in water at 100℃ for 30 minutes, and the structural integrity rate was no less than 80%.

12. The sealing process according to any one of claims 1 to 10, characterized in that, The active substance is selected from at least one of the following: oils, probiotics, vitamins, fragrances, natural pigments, active pharmaceutical ingredients, enzyme preparations, and essential oils.

13. A sealed microcapsule, characterized in that, It is prepared by the sealing process described in any one of claims 1 to 12.

14. The application of the sealed microcapsules according to claim 13 as active substance delivery carriers in the food, pharmaceutical, daily chemical, and agricultural fields.