Fibroin gel preservative film and preparation method thereof

Abstract

The invention discloses a silk protein gel preservative film and a preparation method thereof, and relates to the technical field of preservative film preparation. The silk protein gel preservative film is prepared from the following raw materials in parts by mass: 25 to 35 parts of silk protein, 3 to 6 parts of carbon fiber, 8 to 12 parts of silica sol, 6 to 10 parts of glycerol, 0.3 to 0.7 part of thrombin, 4 to 6 parts of nano-xanthine, 0.2 to 0.5 part of silver nanoparticles, 8 to 12 parts of sodium alginate cross-linking agent, 1 to 3 parts of graphene oxide and 0.8 to 1.5 parts of beta-glucan. The mechanical property and antibacterial property of the film can be effectively improved by utilizing various functional materials such as fibroin, nano silver particles and graphene oxide, the fibroin serving as a natural material not only has good biodegradability, but also can form a stable composite structure with other materials, higher film body strength and ductility are provided, and the mechanical property and antibacterial property of the film are improved. Therefore, the food freshness can be kept, and the packaging box is suitable for packaging various foods.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preservative film preparation, in particular to a silk protein gel preservative film and a preparation method thereof. BACKGROUND

[0002] Preservative film is a common plastic packaging product, usually made of ethylene as the basic raw material through polymerization reaction, and is widely used in microwave heating, refrigerator storage, fresh food and cooked food packaging. It plays an important role in the fields of family, supermarket, catering and food industry. According to the different materials and plasticizers used, there are many types of preservative films to meet different use requirements. However, traditional plastic preservative films have problems of environmental pollution and difficult degradation. Therefore, the development of new natural and biodegradable materials has become a research hotspot. Among them, the gel preservative film based on silk protein not only has good biocompatibility and film forming property, but also has excellent preservative performance and environmental protection characteristics, showing broad application prospects.

[0003] However, in the prior art, petrochemical materials such as polyethylene or polyvinyl chloride are often used as the basis. Although they have certain packaging and barrier properties, their mechanical properties are limited, they are easy to tear and have poor ductility, and most of them do not have natural antibacterial function, which can easily breed bacteria and cause food spoilage. In addition, they have poor biodegradability, and may cause plasticizer migration during use, which poses a food safety hazard and is also not conducive to environmental protection.

[0004] At present, there is no effective solution to the problems in the related art. SUMMARY

[0005] In view of the problems in the related art, the present application provides a silk protein gel preservative film and a preparation method thereof to overcome the above technical problems existing in the prior art.

[0006] To this end, the specific technical solutions adopted by the present application are as follows:

[0007] According to one aspect of the present application, a silk protein gel preservative film is provided, which is composed of the following raw materials in mass fraction:

[0008] 25-35 parts of silk protein, 3-6 parts of carbon fiber, 8-12 parts of silica sol, 6-10 parts of glycerol, 0.3-0.7 parts of thrombin, 4-6 parts of nano xanthophyll, 0.2-0.5 parts of silver nanoparticles, 8-12 parts of sodium alginate crosslinking agent, 1-3 parts of graphene oxide and 0.8-1.5 parts of beta-glucan.

[0009] Further, the thrombin is composed of the following raw materials in mass fraction:

[0010] 0.1-0.2 parts thrombin powder, 0.1-0.3 parts gelatin, and 0.1-0.2 parts physiological saline.

[0011] Furthermore, the nano-flavonoids are composed of the following raw materials in parts by mass:

[0012] 2-2.5 parts modified xanthan gum, 1-2 parts polylactic acid microparticles and 1-1.5 parts mannan oligosaccharide.

[0013] Furthermore, the silver nanoparticles are composed of the following raw materials in parts by mass:

[0014] The ingredients are: 0.12-0.3 parts of nano silver powder, 0.05-0.12 parts of sodium citrate, and 0.03-0.08 parts of reducing agent.

[0015] Furthermore, the sodium alginate crosslinking agent is composed of the following raw materials in parts by weight:

[0016] 5-7 parts sodium alginate, 2-3 parts calcium chloride, and 1-2 parts sodium lactate.

[0017] Furthermore, graphene oxide is composed of the following raw materials in parts by mass:

[0018] 0.4-1 parts graphite powder, 0.2-0.5 parts potassium permanganate, 0.2-1 parts hydrogen peroxide, 0.1-0.2 parts sulfuric acid solution, and 0.1-0.3 parts water.

[0019] Furthermore, the reducing agent includes at least two of ascorbic acid, sodium phytate, glucose, chitosan oligosaccharide, tartaric acid, or potassium citrate.

[0020] Furthermore, β-glucan includes at least two of yeast β-glucan, oat β-glucan, wheat β-glucan, cassava β-glucan, or malt β-glucan.

[0021] According to another aspect of the present invention, a method for preparing a silk fibroin gel preservation film is also provided, the method comprising the following steps:

[0022] S1. Using a stirring device, add silk protein to water according to the preset mass ratio, and stir continuously at 42-48℃ for 20-30 minutes until a uniform and transparent silk protein solution is formed, and then let it cool naturally to 20-25℃ for later use.

[0023] S2. Add thrombin powder, gelatin and physiological saline to a mixing container in the preset mass proportions, and stir for 10-15 minutes in a 35-38℃ water bath until completely dissolved. After obtaining the thrombin complex solution, let it cool naturally to room temperature for later use.

[0024] S3. Add the modified xanthan gum, polylactic acid microparticles and mannan oligosaccharide to the mixing container according to the preset mass proportions, and stir with a magnetic stirrer at 25-30℃ for 30-45 minutes to obtain a uniform nano-xanthan dispersion for later use.

[0025] S4. Add nano silver powder, sodium citrate and reducing agent to a mixing container according to the preset mass parts, and add water according to the preset mass parts and stir well. Use an ultrasonic dispersion device to treat for 15-20 minutes at a frequency of 40-50kHz and a power of 300-500W to obtain a silver nanoparticle dispersion for later use.

[0026] S5. Add graphite powder, potassium permanganate, hydrogen peroxide and sulfuric acid solution to the reaction vessel in the preset mass proportions, control the temperature at 3-5℃, stir the reaction, add water in the preset mass proportions for dilution, and disperse evenly using an ultrasonic dispersion device to obtain graphene oxide solution for later use.

[0027] S6. Add sodium alginate, calcium chloride and sodium lactate to a mixing container according to the preset mass parts, add water according to the preset mass parts and stir for 25-30 minutes to obtain a uniform sodium alginate crosslinking agent solution for later use.

[0028] S7. Add β-glucan to water according to the preset mass fraction and stir to dissolve, so as to obtain a uniform solution for later use.

[0029] S8. Add the solutions obtained from S1 to S7 to the main mixing container in the preset mass proportions, stir with a high-speed mixer at 800-1000 r / min for 30-45 minutes to form a composite gel precursor, and let it stand at room temperature of 20-25℃ for 50-60 minutes to complete the initial cross-linking.

[0030] S9. Pour the composite gel precursor into a glass or polytetrafluoroethylene mold, use a film scraper to scrape and coat it to form a gel layer of uniform thickness, and place it in a ventilated and dark place to stand for 24 hours to form a preliminary film.

[0031] S10. Place the formed preliminary film in a vacuum drying oven and dry it at 40-45℃ for 6-8 hours. After cooling to 20-25℃, slowly remove the film to obtain the finished silk protein gel preservation film.

[0032] Furthermore, according to the preset mass proportions, nano-silver powder, sodium citrate, and reducing agent are added to a mixing container, and water is added in the preset mass proportions. After stirring and mixing, the mixture is treated with an ultrasonic dispersion device for 20 minutes to obtain a silver nanoparticle dispersion for later use. The process includes the following steps:

[0033] S41. Using a stirrer, add the preset mass proportions of nano silver powder, sodium citrate, and reducing agent to the preset mass proportions of water, and stir for 15-20 minutes to form a uniform premixed suspension.

[0034] S42. Transfer the pre-mixed suspension to an ultrasonic dispersion device and ultrasonically treat it for 10-15 minutes at a frequency of 40-50kHz and a power of 300-500W to promote uniform dispersion of the silver nanoparticles and form a stable silver nanoparticle dispersion.

[0035] S43. Let the silver nanoparticle dispersion stand for 10-15 minutes to remove large particle precipitates, and then centrifuge at 3000-3500 r / min for 5-10 minutes. Collect the supernatant for later use.

[0036] S44. The collected supernatant is used as the final silver nanoparticle dispersion and stored in the dark at 5-10℃ to prevent oxidation and performance degradation of the silver nanoparticles for subsequent mixing and use.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. This invention utilizes various functional materials such as silk fibroin, silver nanoparticles, and graphene oxide to effectively improve the mechanical and antibacterial properties of the membrane. As a natural material, silk fibroin not only has good biodegradability but also can form a stable composite structure with other materials, providing stronger membrane strength and extensibility. At the same time, the addition of silver nanoparticles and graphene oxide significantly improves the antibacterial properties of the membrane, which has a significant effect on food preservation, helps to extend the shelf life of food, reduces bacterial contamination, and also has high air permeability, thereby maintaining the freshness of food. It is suitable for various food packaging.

[0039] 2. This invention improves the overall performance of the film by using components such as carbon fiber, silica sol and glycerin. Carbon fiber enhances the tensile strength and structural stability of the film, silica sol improves the barrier properties and thermal stability of the film, and glycerin gives the film good softness and extensibility. The synergistic effect of multiple functional components makes the food preservation film have good mechanical properties, film-forming properties and food adaptability, making it suitable for packaging and storing various types of food. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1This is a flowchart of a method for preparing a silk protein gel preservation film according to an embodiment of the present invention. Detailed Implementation

[0042] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention.

[0043] According to embodiments of the present invention, a silk fibroin gel preservation film and its preparation method are provided.

[0044] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. According to an embodiment of the present invention, the silk protein gel preservation film is composed of the following raw materials in parts by weight:

[0045] The ingredients are: 25-35 parts silk fibroin, 3-6 parts carbon fiber, 8-12 parts silica sol, 6-10 parts glycerol, 0.3-0.7 parts thrombin, 4-6 parts nanoflavin, 0.2-0.5 parts silver nanoparticles, 8-12 parts sodium alginate crosslinking agent, 1-3 parts graphene oxide, and 0.8-1.5 parts β-glucan.

[0046] It should be explained that in the preparation of silk protein gel food preservation film, silk protein, as a natural polymer, has good film-forming properties, biocompatibility, and air permeability, providing a basic supporting framework for the food preservation film; carbon fiber has excellent mechanical properties, improving the tensile strength and structural stability of the film; silica sol, as an inorganic component, enhances the thermal stability and barrier properties of the film; glycerol, a hydrophilic small molecule, can soften the film, increase its flexibility, and prevent cracking; thrombin guides cross-linking between biomolecules, stabilizing the colloidal structure; and nano-flavin modifies yellow... The synergistic effect of the original gum and polylactic acid microparticles regulates the rheological properties of the system, improving its dispersibility and uniformity. Silver nanoparticles impart significant antibacterial activity to the membrane, extending the shelf life of food. Sodium alginate crosslinking agent assists in constructing a three-dimensional gel network during membrane formation, enhancing structural density and water retention. Graphene oxide, through its two-dimensional layered structure, enhances the membrane's toughness and barrier effect, helping to inhibit the permeation of oxygen and water vapor. β-glucan, as a natural polysaccharide, possesses strong moisturizing properties, further enhancing the membrane's flexibility and skin-friendliness, and improving its compatibility with food surfaces. The synergistic effect of these components gives the gel membrane excellent film-forming properties, mechanical strength, barrier properties, antibacterial properties, and biocompatibility, making it suitable for packaging and storing various foods.

[0047] In this optional embodiment, the thrombin is composed of the following parts by weight of raw materials:

[0048] 0.1-0.2 parts thrombin powder, 0.1-0.3 parts gelatin, and 0.1-0.2 parts physiological saline.

[0049] It should be explained that in the preparation of silk protein gel preservation film, thrombin powder acts as a biological cross-linking initiator, which can react with specific sites in protein molecules to promote the formation of network structure; gelatin, as a natural gelling agent, has good hydration and adhesion properties, which helps to improve the formability and flexibility of the film; physiological saline, as a solvent, not only improves the reactivity, but also maintains the osmotic balance of the solution, thus promoting the stable cross-linking and uniform molecular distribution of the gel system as a whole.

[0050] In this optional embodiment, the nanoflavonoid is composed of the following parts by weight of raw materials:

[0051] 2-2.5 parts modified xanthan gum, 1-2 parts polylactic acid microparticles and 1-1.5 parts mannan oligosaccharide.

[0052] It should be explained that, in the preparation of silk protein gel preservation film, modified xanthan gum, as the main gum base material, possesses strong rheological regulation and film-forming properties, providing the membrane with good viscoelastic properties; polylactic acid microparticles impart a certain biodegradable microparticle structure to the system, improving the mechanical strength and elongation at break of the membrane; mannooligosaccharides, as small molecule polysaccharides, can enhance the dispersibility and moisturizing ability of the system, while regulating the hydrophilicity of the membrane surface, achieving a balanced improvement in performance. The combined effect of these three components enables nano-xanthanin to possess a composite function of flow regulation, reinforcement, and moisture retention stability within the membrane structure.

[0053] In this optional embodiment, the silver nanoparticles are composed of the following parts by mass of raw materials:

[0054] The ingredients are: 0.12-0.3 parts of nano silver powder, 0.05-0.12 parts of sodium citrate, and 0.03-0.08 parts of reducing agent.

[0055] It should be explained that in the preparation of silk protein gel preservation film, nano silver powder is the main functional component, which has broad-spectrum antibacterial activity and can effectively inhibit a variety of food spoilage bacteria; sodium citrate, as a stabilizer, can prevent nano silver from agglomerating during dispersion and maintain particle size uniformity; reducing agents (such as ascorbic acid) are used to reduce silver ions into nanoparticles, control their generation rate, and ensure the formation of a silver nanoparticle system with high dispersibility and high activity, thereby significantly enhancing the antibacterial ability and stability of the film.

[0056] In this optional embodiment, the sodium alginate crosslinking agent is composed of the following raw materials in parts by weight:

[0057] 5-7 parts sodium alginate, 2-3 parts calcium chloride, and 1-2 parts sodium lactate.

[0058] It should be explained that sodium alginate, an anionic natural polysaccharide, is used in the preparation of silk protein gel preservation film. (The last part, "Ca2," appears to be an unrelated fragment and is omitted from the translation.) + A stable gel network structure can be formed in its presence; calcium chloride provides the Ca2+ required for cross-linking. + Ions promote physical cross-linking between sodium alginate molecular chains, improving the density and strength of the membrane; sodium lactate, as a co-crosslinking agent and regulator, can alleviate Ca2+ ions. + The release rate makes the crosslinking reaction more mild and controllable, which is conducive to the uniform formation of the membrane structure and the continuous release of stable properties.

[0059] In this optional embodiment, the graphene oxide is composed of the following parts by mass of raw materials:

[0060] 0.4-1 parts graphite powder, 0.2-0.5 parts potassium permanganate, 0.2-1 parts hydrogen peroxide, 0.1-0.2 parts sulfuric acid solution, and 0.1-0.3 parts water.

[0061] It should be explained that in the preparation of silk protein gel preservation film, graphite powder is used as a precursor, and a layered structure is prepared through oxidation modification; potassium permanganate and sulfuric acid form a strong oxidizing system, which promotes the introduction of oxygen-containing groups such as carboxyl and hydroxyl groups between graphite layers; hydrogen peroxide further terminates the reaction and assists in exfoliation; the resulting graphene oxide has good hydrophilicity and mechanical strengthening effect, which can effectively improve the tensile strength and barrier properties of the film, while endowing the film with certain antioxidant capacity and structural functionality.

[0062] In this alternative embodiment, the reducing agent includes at least two of ascorbic acid, sodium phytate, glucose, chitosan oligosaccharide, tartaric acid, or potassium citrate.

[0063] It should be noted that the reducing agents used in the preparation of the silk protein gel preservation film are all environmentally friendly small-molecule compounds with good reducing power and biocompatibility. Among them, ascorbic acid and glucose possess strong electron-donating properties, rapidly reducing silver ions to silver nanoparticles; chitosan oligosaccharides and sodium phytate provide a stable dispersion environment during reduction, preventing particle size growth and aggregation; potassium citrate and tartaric acid have good pH buffering capacity, helping to regulate the stability of the reaction system. The combined application of multiple reducing agents can synergistically control the formation rate and particle size distribution of silver nanoparticles, ensuring product dispersibility and activity.

[0064] In this optional embodiment, the β-glucan includes at least two of yeast β-glucan, oat β-glucan, wheat β-glucan, cassava β-glucan, or malt β-glucan.

[0065] It should be explained that β-glucans from different sources have unique characteristics in terms of structure and molecular weight during the preparation of silk protein gel preservation films. Yeast-derived β-glucans are predominantly branched, enhancing film flexibility and immune activity; while cereal-derived β-glucans, such as oats, wheat, and cassava, are predominantly linear or have few branched chains, providing moisturizing, antioxidant, and structural support functions. The combined use of multiple β-glucans not only improves the moisturizing and skin-friendly properties of the preservation film but also optimizes its overall uniformity and user comfort, further enhancing the film's stability and functional versatility in food contact applications.

[0066] According to another embodiment of the invention, such as Figure 1 As shown, a method for preparing a silk fibroin gel preservation film is also provided, which includes the following steps:

[0067] S1. Using a stirring device, add silk protein to water according to the preset mass ratio, and stir continuously at 42-48℃ for 20-30 minutes until a uniform and transparent silk protein solution is formed, and then let it cool naturally to 20-25℃ for later use.

[0068] S2. Add thrombin powder, gelatin and physiological saline to a mixing container in the preset mass proportions, and stir for 10-15 minutes in a 35-38℃ water bath until completely dissolved. After obtaining the thrombin complex solution, let it cool naturally to room temperature for later use.

[0069] S3. Add the modified xanthan gum, polylactic acid microparticles and mannan oligosaccharide to the mixing container according to the preset mass proportions, and stir with a magnetic stirrer at 25-30℃ for 30-45 minutes to obtain a uniform nano-xanthan dispersion for later use.

[0070] S4. Add nano silver powder, sodium citrate and reducing agent to a mixing container according to the preset mass parts, and add water according to the preset mass parts and stir well. Use an ultrasonic dispersion device to treat for 15-20 minutes at a frequency of 40-50kHz and a power of 300-500W to obtain a silver nanoparticle dispersion for later use.

[0071] S5. Add graphite powder, potassium permanganate, hydrogen peroxide and sulfuric acid solution to the reaction vessel in the preset mass proportions, control the temperature at 3-5℃, stir the reaction, add water in the preset mass proportions for dilution, and disperse evenly using an ultrasonic dispersion device to obtain graphene oxide solution for later use.

[0072] S6. Add sodium alginate, calcium chloride and sodium lactate to a mixing container according to the preset mass parts, add water according to the preset mass parts and stir for 25-30 minutes to obtain a uniform sodium alginate crosslinking agent solution for later use.

[0073] S7. Add β-glucan to water according to the preset mass fraction and stir to dissolve, so as to obtain a uniform solution for later use.

[0074] S8. Add the solutions obtained from S1 to S7 to the main mixing container in the preset mass proportions, stir with a high-speed mixer at 800-1000 r / min for 30-45 minutes to form a composite gel precursor, and let it stand at room temperature of 20-25℃ for 50-60 minutes to complete the initial cross-linking.

[0075] S9. Pour the composite gel precursor into a glass or polytetrafluoroethylene mold, use a film scraper to scrape and coat it to form a gel layer of uniform thickness, and place it in a ventilated and dark place to stand for 24 hours to form a preliminary film.

[0076] S10. Place the formed preliminary film in a vacuum drying oven and dry it at 40-45℃ for 6-8 hours. After cooling to 20-25℃, slowly remove the film to obtain the finished silk protein gel preservation film.

[0077] In this optional embodiment, nano-silver powder, sodium citrate, and reducing agent are added to a mixing container according to preset mass proportions, and water is added according to preset mass proportions. After stirring and mixing, the mixture is treated with an ultrasonic dispersion device for 20 minutes to obtain a silver nanoparticle dispersion for later use. The process includes the following steps:

[0078] S41. Using a stirrer, add the preset mass proportions of nano silver powder, sodium citrate, and reducing agent to the preset mass proportions of water, and stir for 15-20 minutes to form a uniform premixed suspension.

[0079] S42. Transfer the pre-mixed suspension to an ultrasonic dispersion device and ultrasonically treat it for 10-15 minutes at a frequency of 40-50kHz and a power of 300-500W to promote uniform dispersion of the silver nanoparticles and form a stable silver nanoparticle dispersion.

[0080] S43. Let the silver nanoparticle dispersion stand for 10-15 minutes to remove large particle precipitates, and then centrifuge at 3000-3500 r / min for 5-10 minutes. Collect the supernatant for later use.

[0081] S44. The collected supernatant is used as the final silver nanoparticle dispersion and stored in the dark at 5-10℃ to prevent oxidation and performance degradation of the silver nanoparticles for subsequent mixing and use.

[0082] In summary, by means of the above-described technical solution of the present invention, through

[0083] The specific embodiments of the present invention will be further described below with reference to examples and comparative examples:

[0084] Example 1

[0085] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 25g silk protein, 3g carbon fiber, 8g silica sol, 6g glycerin, 0.3g thrombin, 4g nano-xanthanin, 0.2g silver nanoparticles, 8g sodium alginate crosslinking agent, 1g graphene oxide, 0.8g β-glucan, 0.1g thrombin enzyme powder, 0.1g gelatin, 0.1g physiological saline, 2g modified xanthan gum, 1g polylactic acid microparticles, 1g mannan oligosaccharide, 0.12g nano silver powder, 0.05g sodium citrate, 0.03g reducing agent, 5g sodium alginate, 2g calcium chloride, 1g sodium lactate, 0.4g graphite powder, 0.2g potassium permanganate, 0.2g hydrogen peroxide, 0.1g sulfuric acid solution, and 0.1g water.

[0086] Example 2

[0087] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 35g silk protein, 6g carbon fiber, 12g silica sol, 10g glycerin, 0.7g thrombin, 6g nano-xanthanin, 0.5g silver nanoparticles, 12g sodium alginate crosslinking agent, 3g graphene oxide, 1.5g β-glucan, 0.2g thrombin enzyme powder, 0.3g gelatin, 0.2g physiological saline, 2.5g modified xanthan gum, 2g polylactic acid microparticles, 1.5g mannan oligosaccharide, 0.3g nano silver powder, 0.12g sodium citrate, 0.08g reducing agent, 7g sodium alginate, 3g calcium chloride, 2g sodium lactate, 1g graphite powder, 0.5g potassium permanganate, 1g hydrogen peroxide, 0.2g sulfuric acid solution, and 0.3g water.

[0088] Example 3

[0089] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 30g silk protein, 4.5g carbon fiber, 10g silica sol, 8g glycerin, 0.5g thrombin, 5g nano-xanthanin, 0.35g silver nanoparticles, 10g sodium alginate crosslinking agent, 2g graphene oxide, 1.15g β-glucan, 0.15g thrombin enzyme powder, 0.2g gelatin, 0.15g physiological saline, 2.25g modified xanthan gum, 1.5g polylactic acid microparticles, 1.25g mannan oligosaccharide, 0.21g nano silver powder, 0.085g sodium citrate, 0.055g reducing agent, 6g sodium alginate, 2.5g calcium chloride, 1.5g sodium lactate, 0.7g graphite powder, 0.35g potassium permanganate, 0.6g hydrogen peroxide, 0.15g sulfuric acid solution, and 0.2g water.

[0090] Comparative Example 1

[0091] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 25g silk protein, 3g carbon fiber, 8g silica sol, 6g glycerin, 8g sodium alginate crosslinking agent, 1g graphene oxide, 0.8g β-glucan, 5g sodium alginate, 2g calcium chloride, 1g sodium lactate, 0.4g graphite powder, 0.2g potassium permanganate, 0.2g hydrogen peroxide, 0.1g sulfuric acid solution, and 0.1g water.

[0092] Comparative Example 2

[0093] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 35g silk protein, 6g carbon fiber, 12g silica sol, 10g glycerin, 12g sodium alginate crosslinking agent, 3g graphene oxide, 1.5g β-glucan, 7g sodium alginate, 3g calcium chloride, 2g sodium lactate, 1g graphite powder, 0.5g potassium permanganate, 1g hydrogen peroxide, 0.2g sulfuric acid solution, and 0.3g water.

[0094] Comparative Example 3

[0095] The silk protein gel preservation film is composed of the following raw materials in parts by weight: 30g silk protein, 4.5g carbon fiber, 10g silica sol, 8g glycerin, 10g sodium alginate crosslinking agent, 2g graphene oxide, 1.15g β-glucan, 6g sodium alginate, 2.5g calcium chloride, 1.5g sodium lactate, 0.7g graphite powder, 0.35g potassium permanganate, 0.6g hydrogen peroxide, 0.15g sulfuric acid solution, and 0.2g water.

[0096] I. Experimental Objective:

[0097] By comparing the performance of silk protein gel preservation films of Examples 1, 2, and 3 with those of Comparative Examples 1, 2, and 3, the superiority of the present invention in terms of antibacterial properties, mechanical properties, and preservation effect is verified. The focus is on judging the improvement effect of each functional component (such as silver nanoparticles, nano-flavin, graphene oxide, etc.) on the overall performance.

[0098] II. Experimental Methods:

[0099] 1) Antibacterial performance test: The membrane samples were co-cultured with Escherichia coli and Staphylococcus aureus, respectively, and the diameter of the inhibition zone was measured after 24 hours.

[0100] 2) Mechanical property testing: The maximum tensile strength (MPa) and elongation at break (%) of the membrane were determined using a universal testing instrument.

[0101] 3) Preservation effect test: Wrap fresh strawberries in a film and place them in an environment of 25℃ for 7 days, and record the spoilage rate and water loss rate.

[0102] III. Experimental Procedure:

[0103] 1) Antibacterial performance test: Cut the membrane into circular pieces with a diameter of about 3 cm and place them on a bacterial culture medium. After 24 hours of incubation, measure the diameter of the inhibition zone.

[0104] 2) Mechanical property testing: Cut the film sample into rectangular specimens of 10mm × 50mm. Set the tensile speed to 50mm / min and record the tensile strength and elongation at break.

[0105] 3) Preservation effect test: Take equal weight of strawberries from each group, wrap them in film and preserve them. After 7 days, observe the amount of fruit decay, weigh the changes in mass, and calculate the water loss rate.

[0106] IV. Experimental Results:

[0107] 1) Antibacterial performance test (diameter of inhibition zone), as shown in Table 1:

[0108] Table 1. Antibacterial Performance Test

[0109]

[0110]

[0111] 2) Mechanical property tests, as shown in Table 2:

[0112] Table 2. Mechanical Property Tests

[0113] Experimental group Tensile strength (MPa) Elongation at break (%) Example 1 18.2 56 Comparative example 1 11.1 40 Example 2 20.5 63 Comparative example 2 11.6 42 Example 3 19.3 60 Comparative example 3 11.4 41

[0114] 3) Preservation effect test, as shown in Table 3:

[0115] Table 3. Preservation effect test

[0116] Experimental group Spoilage rate (7 days) Loss of water rate (7 days) Example 1 12％ 8％ Comparative example 1 24％ 15％ Example 2 9％ 6％ Comparative example 2 26％ 17％ Example 3 10％ 7％ Comparative example 3 25％ 16％

[0117] V. Comparison of experimental data between each embodiment and the comparative example is shown in Table 4:

[0118] Table 4. Comparison of experimental data between each embodiment and the comparative example.

[0119]

[0120]

[0121] VI. Experimental Conclusions:

[0122] As can be seen from Table 4, Examples 1, 2, and 3 all exhibited significant performance improvements in their corresponding Comparative Examples 1, 2, and 3. The specific conclusions are as follows:

[0123] 1) Antibacterial properties: The antibacterial properties in the examples were significantly higher than those in the comparative examples. In particular, in Example 2, the diameter of the inhibition zone of Escherichia coli and Staphylococcus aureus was significantly increased, which verified the synergistic antibacterial effect of the compound components such as silver nanoparticles, nanoflavin and graphene oxide.

[0124] 2) Mechanical properties: By adding carbon fiber, silica sol and crosslinking agent, the tensile strength and elongation at break of the membrane in the examples were significantly improved. In particular, in Example 2, the tensile strength and ductility of the membrane were significantly enhanced, providing excellent mechanical properties.

[0125] 3) Regarding preservation effect: By reducing the spoilage rate and water loss rate, the preservation effect of the embodiment is significantly better than that of the corresponding embodiment, especially the preservation effect in embodiment 2 is the most significant, indicating that the water resistance and antibacterial properties of the membrane material work together to delay the spoilage and moisture loss of food.

[0126] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A silk protein gel preservation film, characterized in that, This silk protein gel food preservation film is composed of the following raw materials in parts by weight: The ingredients are: 25-35 parts silk fibroin, 3-6 parts carbon fiber, 8-12 parts silica sol, 6-10 parts glycerol, 0.3-0.7 parts thrombin, 4-6 parts nanoflavin, 0.2-0.5 parts silver nanoparticles, 8-12 parts sodium alginate crosslinking agent, 1-3 parts graphene oxide, and 0.8-1.5 parts β-glucan.

2. The silk protein gel preservation film according to claim 1, characterized in that, The thrombin is composed of the following raw materials in parts by weight: 0.1-0.2 parts thrombin powder, 0.1-0.3 parts gelatin, and 0.1-0.2 parts physiological saline.

3. The silk protein gel preservation film according to claim 2, characterized in that, The nanoflavin is composed of the following raw materials in parts by weight: 2-2.5 parts modified xanthan gum, 1-2 parts polylactic acid microparticles and 1-1.5 parts mannan oligosaccharide.

4. The silk protein gel preservation film according to claim 3, characterized in that, The silver nanoparticles are composed of the following raw materials in parts by weight: The ingredients are: 0.12-0.3 parts of nano silver powder, 0.05-0.12 parts of sodium citrate, and 0.03-0.08 parts of reducing agent.

5. The silk protein gel preservation film according to claim 4, characterized in that, The sodium alginate crosslinking agent is composed of the following raw materials in parts by weight: 5-7 parts sodium alginate, 2-3 parts calcium chloride, and 1-2 parts sodium lactate.

6. The silk protein gel preservation film according to claim 5, characterized in that, The graphene oxide is composed of the following raw materials in parts by mass: 0.4-1 parts graphite powder, 0.2-0.5 parts potassium permanganate, 0.2-1 parts hydrogen peroxide, 0.1-0.2 parts sulfuric acid solution, and 0.1-0.3 parts water.

7. The silk protein gel preservation film according to claim 6, characterized in that, The reducing agent includes at least two of ascorbic acid, sodium phytate, glucose, chitosan oligosaccharide, tartaric acid, or potassium citrate.

8. The silk protein gel preservation film according to claim 7, characterized in that, The β-glucan includes at least two of yeast β-glucan, oat β-glucan, wheat β-glucan, cassava β-glucan, or malt β-glucan.

9. A method for preparing a silk fibroin gel preservation film, used to achieve the preparation of the silk fibroin gel preservation film as described in claim 8, characterized in that, The preparation method of this silk protein gel preservation film includes the following steps: S1. Using a stirring device, add silk protein to water according to the preset mass ratio, and stir continuously at 42-48℃ for 20-30 minutes until a uniform and transparent silk protein solution is formed, and then let it cool naturally to 20-25℃ for later use. S2. Add thrombin powder, gelatin and physiological saline to a mixing container in the preset mass proportions, and stir for 10-15 minutes in a 35-38℃ water bath until completely dissolved. After obtaining the thrombin complex solution, let it cool naturally to room temperature for later use. S3. Add the modified xanthan gum, polylactic acid microparticles and mannan oligosaccharide to the mixing container according to the preset mass proportions, and stir with a magnetic stirrer at 25-30℃ for 30-45 minutes to obtain a uniform nano-xanthan dispersion for later use. S4. Add nano silver powder, sodium citrate and reducing agent to a mixing container according to the preset mass parts, and add water according to the preset mass parts and stir well. Use an ultrasonic dispersion device to treat for 15-20 minutes at a frequency of 40-50kHz and a power of 300-500W to obtain a silver nanoparticle dispersion for later use. S5. Add graphite powder, potassium permanganate, hydrogen peroxide and sulfuric acid solution to the reaction vessel in the preset mass proportions, control the temperature at 3-5℃, stir the reaction, add water in the preset mass proportions for dilution, and disperse evenly using an ultrasonic dispersion device to obtain graphene oxide solution for later use. S6. Add sodium alginate, calcium chloride and sodium lactate to a mixing container according to the preset mass parts, add water according to the preset mass parts and stir for 25-30 minutes to obtain a uniform sodium alginate crosslinking agent solution for later use. S7. Add β-glucan to water according to the preset mass fraction and stir to dissolve, so as to obtain a uniform solution for later use. S8. Add the solutions obtained from S1 to S7 to the main mixing container in the preset mass proportions, stir with a high-speed mixer at 800-1000 r / min for 30-45 minutes to form a composite gel precursor, and let it stand at room temperature of 20-25℃ for 50-60 minutes to complete the initial cross-linking. S9. Pour the composite gel precursor into a glass or polytetrafluoroethylene mold, use a film scraper to scrape and coat it to form a gel layer of uniform thickness, and place it in a ventilated and dark place to stand for 24 hours to form a preliminary film. S10. Place the formed preliminary film in a vacuum drying oven and dry it at 40-45℃ for 6-8 hours. After cooling to 20-25℃, slowly remove the film to obtain the finished silk protein gel preservation film.

10. The method for preparing a silk fibroin gel preservation film according to claim 9, characterized in that, The process of adding nano-silver powder, sodium citrate, and reducing agent to a mixing container according to preset mass proportions, adding water according to preset mass proportions, stirring and mixing, and then treating with an ultrasonic dispersion device for 20 minutes to obtain a silver nanoparticle dispersion for later use includes the following steps: S41. Using a stirrer, add the preset mass proportions of nano silver powder, sodium citrate, and reducing agent to the preset mass proportions of water, and stir for 15-20 minutes to form a uniform premixed suspension. S42. Transfer the pre-mixed suspension to an ultrasonic dispersion device and ultrasonically treat it for 10-15 minutes at a frequency of 40-50kHz and a power of 300-500W to promote uniform dispersion of the silver nanoparticles and form a stable silver nanoparticle dispersion. S43. Let the silver nanoparticle dispersion stand for 10-15 minutes to remove large particle precipitates, and then centrifuge at 3000-3500 r / min for 5-10 minutes. Collect the supernatant for later use. S44. The collected supernatant is used as the final silver nanoparticle dispersion and stored in the dark at 5-10℃ to prevent oxidation and performance degradation of the silver nanoparticles for subsequent mixing and use.

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