Starch-based soft capsule and preparation method thereof

Abstract

The invention belongs to the technical field of soft capsules, and discloses a starch-based soft capsule material and a preparation method thereof. Comprising the following steps: mixing wheat starch with deionized water, and adding a sodium periodate solution for reaction to obtain dialdehyde starch; reacting the dialdehyde starch with glycidyl methacrylate and triethylamine to obtain grafted modified starch; mixing the grafted modified starch with the modified nano silicon dioxide, carrying out ultrasonic oscillation, and reacting to obtain nano silicon dioxide composite modified starch; mixing the composite modified starch with polyvinyl alcohol and polyvinylpyrrolidone to prepare a membrane preparation solution; and carrying out tape casting and drying on the film-making liquid, and carrying out hot press molding to finally obtain the starch-based soft capsule material. The starch is subjected to multiple hydrophobic modification, and the hydrophilic performance of the starch is reduced, so that the stability of the soft capsule is improved.

Description

Technical Field

[0001] The invention relates to the technical field of soft capsules, and in particular to a starch-based soft capsule and a preparation method thereof. Background Art

[0002] In the field of medicine and food, soft capsules play an important role as a common carrier of drugs and nutrients. Traditional soft capsules are mostly prepared with gelatin as the main raw material. However, the source of gelatin has certain limitations, such as the risk of animal diseases, and its biodegradability and environmental performance are relatively insufficient. With the growing demand for green and sustainable materials, starch-based soft capsules have emerged. Starch is widely available, low-cost, and has good biodegradability, making it one of the ideal alternative materials to gelatin.

[0003] However, starch-based soft capsules face a serious problem in practical applications, namely, starch itself has strong hydrophilicity. Hydrophilicity makes starch-based soft capsules very easy to absorb moisture during storage and use. During storage, the absorption of moisture will cause the soft capsules to soften, deform, and even stick together, greatly affecting the appearance and quality stability of the product. In the pharmaceutical field, the absorption of moisture may accelerate the degradation of drugs, reduce the efficacy, and shorten the shelf life of drugs; in the food field, the absorption of moisture will cause the oxidation and rancidity of fats and fats in food, the growth of microorganisms, and other problems, causing food deterioration and affecting the taste and nutritional value.

[0004] In addition, soft capsules need to maintain structural integrity under specific environments, such as in the gastrointestinal tract, it is necessary to ensure that they do not disintegrate prematurely in gastric juice and release the contents smoothly in intestinal juice. The high hydrophilicity of starch makes its structural stability deteriorate in a humid environment, making it difficult to meet these complex application requirements. If the hydrophobic properties of starch in starch-based soft capsules can be improved and its hydrophilicity can be reduced, the storage stability of soft capsules can be effectively improved, the shelf life of the product can be extended, its application range under different humidity conditions can be widened, and product quality and safety can be improved, which has great application value and market prospects. However, at present, how to efficiently and stably realize starch hydrophobic modification to meet the requirements of industrial production and practical application of soft capsules is still a key technical problem to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and to provide a starch-based soft capsule and a preparation method thereof. The present invention performs multiple hydrophobic modifications on starch to reduce its hydrophilic properties, thereby improving the stability of the soft capsule.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A method for preparing a starch-based soft capsule material comprises the following steps: (1) Add wheat starch to deionized water to prepare starch milk, add sodium periodate solution dropwise, stir to react, centrifuge, wash and dry to obtain dialdehyde starch; (2) Adding dialdehyde starch to deionized water to prepare starch emulsion, then adding glycidyl methacrylate and triethylamine, heating and stirring to react under nitrogen protection, washing, filtering and drying to obtain grafted modified starch; (3) adding the grafted modified starch into deionized water, stirring and dispersing to obtain a dispersion, then adding modified nano-silicon dioxide, dispersing evenly by ultrasonic oscillation, heating and stirring to react, and obtaining nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch into deionized water, then adding polyvinyl alcohol and polyvinyl pyrrolidone, heating and stirring to obtain a film-making solution; (5) The film-forming liquid is uniformly cast on a preheated polytetrafluoroethylene plate and dried to form a preliminarily formed film, and then the preliminarily formed film is transferred between two stainless steel plates for hot pressing and curing.

[0007] In the prior art, starch-based soft capsules face a serious problem in practical applications, namely, starch itself has strong hydrophilicity. Hydrophilicity makes starch-based soft capsules very easy to absorb moisture during storage and use. During storage, the absorption of moisture will cause the soft capsules to soften, deform, or even stick together, greatly affecting the appearance and quality stability of the product. In order to solve the above technical problems, the present invention improves the stability of starch soft capsule materials in a humid environment from the following three aspects: 1) Under the action of sodium periodate, the vicinal diol structure in the wheat starch molecule is oxidized to a dialdehyde structure. The formation of the dialdehyde structure changes the chemical structure and polarity of the starch molecule, reduces the number of hydrophilic groups such as hydroxyl groups in the molecule, and thus reduces the hydrophilicity of the starch; 2) Dialdehyde starch and glycidyl methacrylate are grafted and copolymerized under the catalysis of triethylamine and nitrogen protection. Glycidyl methacrylate is grafted onto the dialdehyde starch molecule, introducing hydrophobic organic groups into the starch molecule, increasing the hydrophobicity of the starch molecule; 3) By mixing food-grade nano-silica into the soft capsule material, the food-grade nano-silica and the grafted modified starch form a nano-composite structure through physical adsorption and chemical bonding. The nanostructure can fill the gaps in the starch molecules, which can hinder the penetration of water molecules into the soft capsule material, thereby further improving the stability of the starch soft capsule in a humid environment.

[0008] Preferably, in step (1), the mass ratio of sodium periodate to wheat starch is 1:10-15.

[0009] Preferably, in step (2), the mass ratio of dialdehyde starch to glycidyl methacrylate is 1:0.3-0.5.

[0010] Preferably, in step (2), the amount of triethylamine added is 0.5-3.0% of the mass of dialdehyde starch.

[0011] Preferably, in step (3), the method for preparing modified nano-silicon dioxide comprises the following steps: Add nano silicon dioxide into anhydrous ethanol, stir and disperse evenly, then add silane coupling agent hydrolyzate, heat and stir to react, then add polyvinyl alcohol, heat and stir to react, centrifuge, wash and dry to obtain modified nano silicon dioxide.

[0012] In the technical solution of the present invention, as described above, the above series of methods are used to improve the stability of starch soft capsule materials in a humid environment. However, a further problem encountered is that the flexibility of the soft capsule material decreases, causing the soft capsule material to become more brittle and prone to rupture during processing or use. After research by the present invention team, it was found that nano-silicon dioxide has a significant effect on the flexibility of the soft capsule material. This may be because nano-silicon dioxide agglomerates due to its high surface energy. The agglomerates are like rigid particles. When the material is subjected to external forces, the relative sliding of the starch molecular chain is hindered, and the flexible extension of the molecular chain is limited, thereby causing the flexibility of the soft capsule to decrease. In order to further solve this technical problem, the present invention further modifies nano-silicon dioxide, and polyvinyl alcohol is grafted to the surface of nano-silicon dioxide through a silane coupling agent. After polyvinyl alcohol is grafted to the surface of nano-silicon dioxide, the hydroxyl groups on its molecular chain can interact with the hydroxyl groups in the starch molecules through intermolecular forces such as hydrogen bonds. This interaction builds a "bridge" between nano-silicon dioxide and starch, allowing nano-silicon dioxide to be more evenly dispersed in the starch matrix, effectively improving the interfacial compatibility of the two. The uniformly dispersed nano-silica no longer becomes an agglomerate that hinders the movement of starch molecular chains, providing a more favorable environment for the flexible movement of starch molecular chains, thereby improving the flexibility of soft capsules. In addition, nano-silica grafted with polyvinyl alcohol can disperse and transmit stress more effectively due to its uniform dispersion and good interaction with starch molecules. When the material is subjected to external force, the stress can be evenly distributed throughout the system, avoiding excessive local concentration of stress, thereby reducing the brittle fracture of the material caused by stress concentration, and further improving the flexibility and deformation resistance of the soft capsule.

[0013] Preferably, the modified nano-silicon dioxide is added in an amount of 1.5-3.0% of the mass of the grafted modified starch.

[0014] Preferably, in step (4), the polyvinyl alcohol is polyvinyl alcohol 400.

[0015] Preferably, in step (4), the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol is 1:0.5-1.0.

[0016] Preferably, in step (4), the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.05-0.15.

[0017] A starch-based soft capsule material is prepared by the above method.

[0018] The present invention has the following beneficial effects: (1) The starch soft capsule material has undergone a series of modifications to significantly reduce its hydrophilicity and has excellent stability in a humid environment; (2) Starch soft capsule material has good flexibility and is not prone to rupture during processing or use. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Embodiment 1: A method for preparing a starch-based soft capsule material, comprising the following steps: (1) Wheat starch was added to deionized water at a mass volume ratio of 1 g / 10 mL to prepare starch milk, which was placed in a reaction vessel equipped with a stirrer and a thermometer. A sodium periodate solution with a mass concentration of 30% was slowly added dropwise in a 45°C water bath, and the mass ratio of sodium periodate to wheat starch was 1:14. The mixture was stirred for 5 h, and dialdehyde starch was obtained after centrifugal separation, washing and drying. (2) Add dialdehyde starch to deionized water at a mass volume ratio of 1 g / 5 mL to prepare starch emulsion, add the starch emulsion into a reactor, and then add methyl methacrylate glycidyl ether and triethylamine, the mass ratio of dialdehyde starch to methyl methacrylate glycidyl ether being 1:0.45, and the amount of triethylamine added being 2.5% of the mass of dialdehyde starch. Under nitrogen protection, heat to 60°C, stir and react for 6 hours, wash, filter and dry to obtain grafted modified starch; (3) Add the grafted modified starch into deionized water at a mass volume ratio of 1 g / 5 mL, stir and disperse to obtain a dispersion, then add modified nano-silicon dioxide, the amount of modified nano-silicon dioxide added is 2.5% of the mass of the grafted modified starch, disperse evenly by ultrasonic oscillation, heat to 70°C, stir and react for 2 h, wash, filter and dry to obtain nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch to deionized water at a mass volume ratio of 1 g / 7 mL, and then adding polyvinyl alcohol 400 and polyvinyl pyrrolidone, the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol 400 is 1:0.9, and the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.12, heating to 80° C., stirring for 3 h, and obtaining a film-making solution; (5) The film-forming liquid is uniformly cast on a polytetrafluoroethylene plate preheated to 50°C and dried to form a preliminary formed film. The preliminary formed film is then transferred between two stainless steel plates preheated to 60°C and hot-pressed at a pressure of 1.8 MPa for 5 minutes to cure and form.

[0021] The preparation method of modified nano silicon dioxide comprises the following steps: Add 50 mL of anhydrous ethanol and 5 mL of deionized water into a 250 mL three-necked flask, stir evenly, add 3 g of KH-570 silane coupling agent, and then drop glacial acetic acid to adjust the pH value to 4-5. Stir and hydrolyze in a 40 ° C water bath for 1 hour to obtain a coupling agent hydrolyzate; Take 5g of nano-silica and add it to 100mL of anhydrous ethanol, stir and disperse it for 30min to make it evenly dispersed, and obtain a nano-silica dispersion. Add the nano-silica dispersion to the coupling agent hydrolyzate, heat it to 70°C, stir and react for 3h, so that the silane coupling agent and the hydroxyl groups on the surface of the nano-silica undergo a condensation reaction to complete the surface silanization treatment of the nano-silica. Subsequently, add 5g of polyvinyl alcohol, heat it to 90°C, continue to stir and react for 5h, and obtain modified nano-silica after centrifugal separation, washing and drying.

[0022] Embodiment 2: A method for preparing a starch-based soft capsule material, comprising the following steps: (1) Wheat starch was added to deionized water at a mass volume ratio of 1 g / 10 mL to prepare starch milk, which was placed in a reaction vessel equipped with a stirrer and a thermometer. A sodium periodate solution with a mass concentration of 30% was slowly added dropwise in a 45°C water bath, and the mass ratio of sodium periodate to wheat starch was 1:11. The mixture was stirred for 5 h, and dialdehyde starch was obtained after centrifugal separation, washing and drying. (2) Add dialdehyde starch to deionized water at a mass volume ratio of 1 g / 5 mL to prepare starch emulsion, add the starch emulsion into a reactor, and then add methyl methacrylate glycidyl ether and triethylamine, the mass ratio of dialdehyde starch to methyl methacrylate glycidyl ether is 1:0.35, and the amount of triethylamine added is 1.0% of the mass of dialdehyde starch. Under nitrogen protection, heat to 60°C, stir and react for 6 hours, wash, filter and dry to obtain grafted modified starch; (3) Add the grafted modified starch into deionized water at a mass volume ratio of 1 g / 5 mL, stir and disperse to obtain a dispersion, then add modified nano-silicon dioxide, the amount of modified nano-silicon dioxide added is 2.0% of the mass of the grafted modified starch, disperse evenly by ultrasonic oscillation, heat to 70°C, stir and react for 2 h, wash, filter and dry to obtain nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch to deionized water at a mass volume ratio of 1 g / 7 mL, and then adding polyvinyl alcohol 400 and polyvinyl pyrrolidone, the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol 400 is 1:0.6, and the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.08, heating to 80 ° C, stirring for 3 h, and obtaining a film-making solution; (5) The film-forming liquid is uniformly cast on a polytetrafluoroethylene plate preheated to 50°C and dried to form a preliminary formed film. The preliminary formed film is then transferred between two stainless steel plates preheated to 60°C and hot-pressed at a pressure of 1.8 MPa for 5 minutes to cure and form.

[0023] The preparation method of modified nano silicon dioxide comprises the following steps: Add 50 mL of anhydrous ethanol and 5 mL of deionized water into a 250 mL three-necked flask, stir evenly, add 3 g of KH-570 silane coupling agent, and then drop glacial acetic acid to adjust the pH value to 4-5. Stir and hydrolyze in a 40 ° C water bath for 1 hour to obtain a coupling agent hydrolyzate; Take 5g of nano-silica and add it to 100mL of anhydrous ethanol, stir and disperse it for 30min to make it evenly dispersed, and obtain a nano-silica dispersion. Add the nano-silica dispersion to the coupling agent hydrolyzate, heat it to 70°C, stir and react for 3h, so that the silane coupling agent and the hydroxyl groups on the surface of the nano-silica undergo a condensation reaction to complete the surface silanization treatment of the nano-silica. Subsequently, add 5g of polyvinyl alcohol, heat it to 90°C, continue to stir and react for 5h, and obtain modified nano-silica after centrifugal separation, washing and drying.

[0024] Embodiment 3: A method for preparing a starch-based soft capsule material, comprising the following steps: (1) Wheat starch was added to deionized water at a mass volume ratio of 1 g / 10 mL to prepare starch milk, which was placed in a reaction vessel equipped with a stirrer and a thermometer, and a sodium periodate solution with a mass concentration of 30% was slowly added dropwise in a 45° C. water bath, with the mass ratio of sodium periodate to wheat starch being 1:12. The mixture was stirred for 5 h, and dialdehyde starch was obtained after centrifugal separation, washing and drying. (2) Add dialdehyde starch to deionized water at a mass volume ratio of 1 g / 5 mL to prepare starch emulsion, add the starch emulsion into a reactor, and then add methyl methacrylate glycidyl ether and triethylamine, the mass ratio of dialdehyde starch to methyl methacrylate glycidyl ether being 1:0.4, and the amount of triethylamine added being 1.5% of the mass of dialdehyde starch. Under nitrogen protection, heat to 60°C, stir and react for 6 hours, wash, filter and dry to obtain grafted modified starch; (3) Add the grafted modified starch into deionized water at a mass volume ratio of 1 g / 5 mL, stir and disperse to obtain a dispersion, then add modified nano-silicon dioxide, the amount of modified nano-silicon dioxide added is 2.2% of the mass of the grafted modified starch, disperse evenly by ultrasonic oscillation, heat to 70°C, stir and react for 2 h, wash, filter and dry to obtain nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch to deionized water at a mass volume ratio of 1 g / 7 mL, and then adding polyvinyl alcohol 400 and polyvinyl pyrrolidone, the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol 400 is 1:0.7, and the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.1, heating to 80° C., stirring for 3 h, and obtaining a film-making solution; (5) The film-forming liquid is uniformly cast on a polytetrafluoroethylene plate preheated to 50°C and dried to form a preliminary formed film. The preliminary formed film is then transferred between two stainless steel plates preheated to 60°C and hot-pressed at a pressure of 1.8 MPa for 5 minutes to cure and form.

[0025] The preparation method of modified nano silicon dioxide comprises the following steps: Add 50 mL of anhydrous ethanol and 5 mL of deionized water into a 250 mL three-necked flask, stir evenly, add 3 g of KH-570 silane coupling agent, and then drop glacial acetic acid to adjust the pH value to 4-5. Stir and hydrolyze in a 40 ° C water bath for 1 hour to obtain a coupling agent hydrolyzate; Take 5g of nano-silica and add it to 100mL of anhydrous ethanol, stir and disperse it for 30min to make it evenly dispersed, and obtain a nano-silica dispersion. Add the nano-silica dispersion to the coupling agent hydrolyzate, heat it to 70°C, stir and react for 3h, so that the silane coupling agent and the hydroxyl groups on the surface of the nano-silica undergo a condensation reaction to complete the surface silanization treatment of the nano-silica. Subsequently, add 5g of polyvinyl alcohol, heat it to 90°C, continue to stir and react for 5h, and obtain modified nano-silica after centrifugal separation, washing and drying.

[0026] Embodiment 4: A method for preparing a starch-based soft capsule material, comprising the following steps: (1) Wheat starch was added to deionized water at a mass volume ratio of 1 g / 10 mL to prepare starch milk, which was placed in a reaction vessel equipped with a stirrer and a thermometer. A sodium periodate solution with a mass concentration of 30% was slowly added dropwise in a 45°C water bath, and the mass ratio of sodium periodate to wheat starch was 1:15. The mixture was stirred for 5 h, and dialdehyde starch was obtained after centrifugal separation, washing and drying. (2) Add dialdehyde starch to deionized water at a mass volume ratio of 1 g / 5 mL to prepare starch emulsion, add the starch emulsion into a reactor, and then add methyl methacrylate glycidyl ether and triethylamine, the mass ratio of dialdehyde starch to methyl methacrylate glycidyl ether being 1:0.5, and the amount of triethylamine added being 3.0% of the mass of dialdehyde starch. Under nitrogen protection, heat to 60°C, stir and react for 6 hours, wash, filter and dry to obtain grafted modified starch; (3) Add the grafted modified starch into deionized water at a mass volume ratio of 1 g / 5 mL, stir and disperse to obtain a dispersion, then add modified nano-silicon dioxide, the amount of modified nano-silicon dioxide added is 3.0% of the mass of the grafted modified starch, disperse evenly by ultrasonic oscillation, heat to 70°C, stir and react for 2 h, wash, filter and dry to obtain nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch to deionized water at a mass volume ratio of 1 g / 7 mL, and then adding polyvinyl alcohol 400 and polyvinyl pyrrolidone, the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol 400 is 1:1.0, and the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.15, heating to 80° C., stirring for 3 h, and obtaining a film-making solution; (5) The film-forming liquid is uniformly cast on a polytetrafluoroethylene plate preheated to 50°C and dried to form a preliminary formed film. The preliminary formed film is then transferred between two stainless steel plates preheated to 60°C and hot-pressed at a pressure of 1.8 MPa for 5 minutes to cure and form.

[0027] The preparation method of modified nano silicon dioxide comprises the following steps: Add 50 mL of anhydrous ethanol and 5 mL of deionized water into a 250 mL three-necked flask, stir evenly, add 3 g of KH-570 silane coupling agent, and then drop glacial acetic acid to adjust the pH value to 4-5. Stir and hydrolyze in a 40 ° C water bath for 1 hour to obtain a coupling agent hydrolyzate; Take 5g of nano-silica and add it to 100mL of anhydrous ethanol, stir and disperse it for 30min to make it evenly dispersed, and obtain a nano-silica dispersion. Add the nano-silica dispersion to the coupling agent hydrolyzate, heat it to 70°C, stir and react for 3h, so that the silane coupling agent and the hydroxyl groups on the surface of the nano-silica undergo a condensation reaction to complete the surface silanization treatment of the nano-silica. Subsequently, add 5g of polyvinyl alcohol, heat it to 90°C, continue to stir and react for 5h, and obtain modified nano-silica after centrifugal separation, washing and drying.

[0028] Embodiment 5: A method for preparing a starch-based soft capsule material, comprising the following steps: (1) Wheat starch was added to deionized water at a mass volume ratio of 1 g / 10 mL to prepare starch milk, which was placed in a reaction vessel equipped with a stirrer and a thermometer, and a sodium periodate solution with a mass concentration of 30% was slowly added dropwise in a 45° C. water bath, with the mass ratio of sodium periodate to wheat starch being 1:10. The mixture was stirred for 5 h, and dialdehyde starch was obtained after centrifugal separation, washing and drying. (2) Add dialdehyde starch to deionized water at a mass volume ratio of 1 g / 5 mL to prepare starch emulsion, add the starch emulsion into a reactor, and then add methyl methacrylate glycidyl ether and triethylamine, the mass ratio of dialdehyde starch to methyl methacrylate glycidyl ether being 1:0.3, and the amount of triethylamine added being 0.5% of the mass of dialdehyde starch. Under nitrogen protection, heat to 60°C, stir and react for 6 hours, wash, filter and dry to obtain grafted modified starch; (3) Add the grafted modified starch into deionized water at a mass volume ratio of 1 g / 5 mL, stir and disperse to obtain a dispersion, then add modified nano-silicon dioxide, the amount of modified nano-silicon dioxide added is 1.5% of the mass of the grafted modified starch, disperse evenly by ultrasonic oscillation, heat to 70°C, stir and react for 2 h, wash, filter and dry to obtain nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch to deionized water at a mass volume ratio of 1 g / 7 mL, and then adding polyvinyl alcohol 400 and polyvinyl pyrrolidone, the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol 400 is 1:0.5, and the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.05, heating to 80° C., stirring for 3 h, and obtaining a film-making solution; (5) The film-forming liquid is uniformly cast on a polytetrafluoroethylene plate preheated to 50°C and dried to form a preliminary formed film. The preliminary formed film is then transferred between two stainless steel plates preheated to 60°C and hot-pressed at a pressure of 1.8 MPa for 5 minutes to cure and form.

[0029] The preparation method of modified nano silicon dioxide comprises the following steps: Add 50 mL of anhydrous ethanol and 5 mL of deionized water into a 250 mL three-necked flask, stir evenly, add 3 g of KH-570 silane coupling agent, and then drop glacial acetic acid to adjust the pH value to 4-5. Stir and hydrolyze in a 40 ° C water bath for 1 hour to obtain a coupling agent hydrolyzate; Take 5g of nano-silica and add it to 100mL of anhydrous ethanol, stir and disperse it for 30min to make it evenly dispersed, and obtain a nano-silica dispersion. Add the nano-silica dispersion to the coupling agent hydrolyzate, heat it to 70°C, stir and react for 3h, so that the silane coupling agent and the hydroxyl groups on the surface of the nano-silica undergo a condensation reaction to complete the surface silanization treatment of the nano-silica. Subsequently, add 5g of polyvinyl alcohol, heat it to 90°C, continue to stir and react for 5h, and obtain modified nano-silica after centrifugal separation, washing and drying.

[0030] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is: Steps (1) and (2) are omitted in the preparation process of starch-based soft capsule materials; The remaining steps are the same as those in Example 1.

[0031] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is: Step (3) is omitted in the preparation process of starch-based soft capsule materials; The remaining steps are the same as those in Example 1.

[0032] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that: The modified nano-silica in step (3) is replaced by ordinary nano-silica; The remaining steps are the same as those in Example 1.

[0033] Control The control sample was prepared from ordinary wheat starch as soft capsule material.

[0034] Performance Testing Soft capsule material stability test: The medium-quality soft capsule materials of the examples and comparative examples were placed in a constant temperature and humidity chamber, taken out after 10 days, and the moisture content thereof was determined using the toluene method. The humidity was controlled at 5%, 20%, 40%, 60% and 80% respectively, and then the moisture content (%) of the soft capsule materials after 10 days was tested.

[0035]

[0036] Soft capsule material flexibility test: Place the starch capsule shell sample on the operating table, manually fold it in half several times, and observe whether there are cracks, breaks, etc. on the surface of the sample. If the sample shows obvious cracks or breaks after a certain number of folds, it means that its flexibility is good; if cracks or breaks appear after a few folds, the flexibility is poor. Use a magnifying glass to observe the microstructural changes at the fold to assist in judging the flexibility.

[0037]

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a starch-based soft capsule material, characterized in that: The following steps are involved: (1) Add wheat starch to deionized water to prepare starch milk, add sodium periodate solution dropwise, stir to react, centrifuge, wash and dry to obtain dialdehyde starch; (2) Adding dialdehyde starch to deionized water to prepare starch emulsion, then adding glycidyl methacrylate and triethylamine, heating and stirring to react under nitrogen protection, washing, filtering and drying to obtain grafted modified starch; (3) adding the grafted modified starch into deionized water, stirring and dispersing to obtain a dispersion, then adding modified nano-silicon dioxide, dispersing evenly by ultrasonic oscillation, heating and stirring to react, and obtaining nano-silicon dioxide composite modified starch; (4) adding nano-silicon dioxide composite modified starch into deionized water, then adding polyvinyl alcohol and polyvinyl pyrrolidone, heating and stirring to obtain a film-making solution; (5) The film-forming liquid is uniformly cast on a preheated polytetrafluoroethylene plate and dried to form a preliminarily formed film, and then the preliminarily formed film is transferred between two stainless steel plates for hot pressing and curing.

2. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (1), the mass ratio of sodium periodate to wheat starch is 1:10-15.

3. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (2), the mass ratio of dialdehyde starch to glycidyl methacrylate is 1:0.3-0.

5.

4. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (2), the amount of triethylamine added is 0.5-3.0% of the mass of the dialdehyde starch.

5. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (3), the preparation method of modified nano-silicon dioxide comprises the following steps: Add nano silicon dioxide into anhydrous ethanol, stir and disperse evenly, then add silane coupling agent hydrolyzate, heat and stir to react, then add polyvinyl alcohol, heat and stir to react, centrifuge, wash and dry to obtain modified nano silicon dioxide.

6. The method for preparing a starch-based soft capsule material according to claim 5, characterized in that: The added amount of the modified nano silicon dioxide is 1.5-3.0% of the mass of the grafted modified starch.

7. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (4), the polyvinyl alcohol is polyvinyl alcohol 400.

8. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (4), the mass ratio of nano-silicon dioxide composite modified starch to polyvinyl alcohol is 1:0.5-1.

0.

9. The method for preparing a starch-based soft capsule material according to claim 1, characterized in that: In the step (4), the mass ratio of the nano-silicon dioxide composite modified starch to polyvinyl pyrrolidone is 1:0.05-0.

15.

10. A starch-based soft capsule material, characterized in that: The method is prepared by any one of claims 1 to 9.

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