A cellulose-based antibacterial hydrogel film loaded with ampelopsis extract and its preparation method and application

Abstract

This invention belongs to the field of food packaging materials technology, specifically relating to a cellulose-based antibacterial hydrogel film loaded with vine tea extract, its preparation method, and its applications. This invention addresses the problems of poor stability and lack of long-lasting antibacterial function in existing cellulose packaging materials under humid conditions, as well as the easy oxidation and loss of vine tea extract and its difficulty in slow release. First, vine tea extract is prepared using a microwave-ultrasound combined process. Then, cellulose is dissolved in a sodium hydroxide-urea low-temperature dissolution system, cross-linked with epichlorohydrin, loaded with vine tea extract, cast, washed, and dried to obtain a composite film. In this film, the vine tea extract forms hydrogen bonds with cellulose, resulting in a dense structure. It possesses both excellent barrier properties and broad-spectrum antibacterial activity, enabling stable and slow release of active ingredients. It achieves a synergistic effect of passive barrier and active antibacterial activity in food packaging and fruit and vegetable preservation. The material is biodegradable, and the preparation process is mild and easily scalable.

Description

Technical Field

[0001] This invention belongs to the field of food packaging materials technology, specifically relating to a cellulose-based antibacterial hydrogel film loaded with vine tea extract, its preparation method, and its application. Background Technology

[0002] Food packaging is a crucial component of the food industry, playing an irreplaceable role in ensuring food safety, extending shelf life, and enhancing product added value. For a long time, petroleum-based plastics such as polyethylene, polypropylene, and polystyrene have held a dominant position in the global food packaging sector due to their excellent mechanical, barrier, and processing properties. However, with the deepening of global green and sustainable development concepts, the inherent defects of these petroleum-based plastics have become increasingly prominent: they are difficult to completely degrade in the natural environment, resulting in severe "white pollution" from large amounts of waste plastic; their functions are limited, only providing basic physical barrier effects and failing to actively inhibit the growth and reproduction of microorganisms on food surfaces; and they pose a potential risk of harmful substance migration, which may threaten food safety. Therefore, developing new food packaging materials that are renewable, environmentally friendly, and functional has become a critical technical problem urgently needing to be solved in this field.

[0003] Biodegradable materials are widely recognized as ideal alternatives to traditional petroleum-based plastics due to their wide availability, good biocompatibility, and environmentally friendly degradation products. Cellulose, as the most abundant natural polymer in the world, boasts advantages such as low cost, excellent film-forming properties, and ease of chemical modification, showing broad application prospects in the food packaging materials field. Cellulose hydrogels, through chemical cross-linking or physical entanglement, form a three-dimensional polymer network structure capable of absorbing and retaining large amounts of moisture, while also possessing good biocompatibility and complete degradability, making them a high-quality substrate for preparing active food packaging. However, pure cellulose hydrogels have significant limitations: their strong hydrophilicity leads to poor mechanical stability in humid food packaging environments, making them prone to swelling, deformation, and even breakage; furthermore, they lack antibacterial properties, failing to effectively inhibit the growth of foodborne pathogens and thus failing to meet the preservation requirements of perishable foods. Although there are existing reports on the application of cellulose materials in food packaging, how to maintain the inherent degradability of the material while effectively improving its structural stability in humid environments and endowing it with efficient and durable antibacterial properties remains a long-standing technical challenge in this field.

[0004] To endow packaging materials with active antibacterial properties, researchers have explored adding various types of antibacterial agents to the substrate. Among these, plant-derived antibacterial agents have attracted widespread attention in the field due to their advantages such as natural origin, high biosafety, and environmental friendliness. The extract of young stems and leaves of *Tea japonica* contains various flavonoids with dihydromyricetin as the main active ingredient, exhibiting broad-spectrum inhibitory effects against a variety of common foodborne pathogens such as *Staphylococcus aureus* and *Escherichia coli*, making it a natural antibacterial agent with great development potential. However, when *Tea japonica* extract is directly compounded into packaging materials, it suffers from poor stability, susceptibility to environmental factors, and difficulty in achieving controlled and sustained release of active ingredients, resulting in insufficient and prolonged antibacterial effects and severely limiting its practical application in the food packaging field. Therefore, how to achieve stable loading and precise controlled release of *Tea japonica* extract through reasonable carrier material design, thereby maintaining its bioactivity throughout the entire life cycle of the packaging material, is another core technical problem that urgently needs to be solved in this field.

[0005] In summary, existing technologies have not yet provided a solution that can simultaneously address the insufficient structural stability of cellulose-based packaging materials and the difficulty in controlling the release of natural antibacterial agents, thus failing to meet the urgent demand in the food packaging industry for green, safe, and long-lasting antibacterial packaging materials. Summary of the Invention

[0006] The present invention aims to provide a cellulose-based antibacterial hydrogel film loaded with vine tea extract, its preparation method and application. The film has good biocompatibility and is non-irritating, meeting the safety requirements for use in the food packaging field. In food packaging and fruit and vegetable preservation applications, it can achieve a synergistic preservation effect of passive barrier and active antibacterial, effectively inhibiting the growth of microorganisms on the surface of packaged food, delaying fruit weight loss and mold growth, and extending the shelf life of food.

[0007] The objective of this invention is achieved through the following technical solution: This invention provides a cellulose-based antibacterial hydrogel film loaded with vine tea extract. The film uses regenerated cellulose hydrogel as the matrix, and the vine tea extract is dispersed in the three-dimensional network structure of the regenerated cellulose hydrogel. The vine tea extract interacts with the cellulose molecules through hydrogen bonds, which densifies the film structure. The film has a broad-spectrum inhibitory effect on Escherichia coli and Staphylococcus aureus.

[0008] Furthermore, the loading of vine tea extract in the composite film is 0.05 to 0.5 wt% of the cellulose mass.

[0009] Furthermore, the film is prepared by drying a film-forming solution with a thickness of 0.4 to 1 mm applied by wet film scraping.

[0010] The present invention also provides a method for preparing the cellulose-based antibacterial hydrogel film loaded with vine tea extract, comprising the following steps: (A) Preparation of vine tea extract: Dried vine tea was mixed with distilled water, and the pH was adjusted to 7.0-7.5 with acetic acid. After soaking at room temperature, microwave radiation and ultrasonic extraction were performed in sequence. After multi-stage filtration, the filtrate was concentrated, freeze-dried and ground into powder to obtain vine tea extract. (B) Preparation of composite film: Sodium hydroxide, urea and deionized water are mixed to form a solvent system. After pre-cooling, cellulose is added and stirred until completely dissolved. Epichlorohydrin is then added to initiate a cross-linking reaction. Subsequently, the vine tea extract obtained in step (A) is added and stirring is continued. The mixture is cast into a mold, washed and dried to obtain a cellulose-based antibacterial hydrogel film loaded with vine tea extract. Step (B) is performed after step (A) is completed.

[0011] Further, in step (A), the dried vine tea is pulverized to 20-60 mesh, and the ratio of dried vine tea to distilled water is 20-50 mL of distilled water per gram; the soaking time at room temperature is 30-60 min; the microwave radiation power is 150-250 W for 20-40 min; the ultrasonic extraction power is 100-200 W for 0.5-2 h; the multi-stage filtration is carried out sequentially by filtration through 100-200 mesh nylon cloth and vacuum filtration; the concentration is carried out under reduced pressure at 50-70℃; and the freeze-drying is carried out at -40 to -20℃ and a vacuum of 10-30 Pa for 12-24 h.

[0012] Furthermore, in step (B), the mass ratio of sodium hydroxide, urea, and deionized water is 7:12:77; the pre-cooling temperature is below -12℃, and the cellulose dissolution, cross-linking reaction, and vine tea extract mixing process are all carried out in an ice-water bath at 0–4℃.

[0013] Furthermore, in step (B), the mass ratio of cellulose to epichlorohydrin is 10:1 to 5:1; after the epichlorohydrin is added, the mixture is stirred in an ice bath for 20 to 60 minutes to initiate the cross-linking reaction; after the vine tea extract is added, the mixture is stirred for another 60 to 120 minutes until it is evenly mixed.

[0014] Furthermore, in step (B), the washing process involves washing 2-3 times with 0.1-0.3 mol / L acetic acid, followed by rinsing with purified water until neutral; the drying process involves drying at 35-45°C with forced air until constant weight.

[0015] The present invention also provides an application of the cellulose-based antibacterial hydrogel film loaded with vine tea extract, wherein the film is used to prepare food packaging materials, and through the three-dimensional network structure, the stable loading and slow release of vine tea extract are achieved, thereby realizing the synergistic preservation effect of passive barrier and active antibacterial in food packaging or fruit and vegetable preservation.

[0016] Furthermore, the food packaging material is a fruit and vegetable preservation film, which can be used for the room temperature preservation of strawberries.

[0017] The beneficial effects of this invention are as follows: This invention addresses the technical challenge of existing food packaging materials in achieving both environmental friendliness and long-lasting antibacterial properties. Using cellulose, the most abundant, renewable, and inexpensive natural resource, as a base material, and compounded with vine tea extract from natural plants, an antibacterial hydrogel film is prepared. This film replaces traditional petroleum-based plastic packaging materials, avoiding the problems of petroleum-based materials being difficult to degrade naturally, having limited functionality, and potentially causing the migration of harmful substances. The resulting product is completely biodegradable, and the degradation products are harmless, meeting the current requirements for green and sustainable development.

[0018] This invention uniformly disperses vine tea extract within a three-dimensional network structure of regenerated cellulose hydrogel. Hydrogen bonds form between the vine tea extract and cellulose molecules, resulting in a denser and more continuous film structure. This not only overcomes the inherent defects of pure cellulose hydrogels, such as high hydrophilicity and poor mechanical stability in humid environments, but also significantly reduces the water vapor and oxygen permeability of the film, greatly enhancing its barrier properties and providing effective passive protection for packaged foods. Within the preferred loading range of 0.05–0.5 wt%, the synergistic effect between the vine tea extract and the cellulose matrix is ​​optimal, and excessive loading of active ingredients does not lead to a decrease in the mechanical properties of the film.

[0019] This invention utilizes the three-dimensional network structure of cellulose hydrogel to achieve stable loading of vine tea extract, effectively solving the technical problems of poor stability, susceptibility to environmental factors, easy loss, and difficulty in achieving sustained release when vine tea extract is directly applied to packaging materials. It can maintain the bioactivity of flavonoid active ingredients such as dihydromyricetin in vine tea extract, and achieve the slow release of active ingredients. In this way, the film has a highly efficient and long-lasting broad-spectrum inhibitory effect on common foodborne pathogens such as Escherichia coli and Staphylococcus aureus, giving the packaging material an active antibacterial function.

[0020] This invention utilizes a sodium hydroxide-urea low-temperature dissolution system to dissolve cellulose, preserving its molecular structure. The entire preparation process is simple, with mild reaction conditions, requiring no complex equipment or harsh reaction environments, and each step is easily scalable for large-scale production. The preparation process includes a neutralization and washing step with acetic acid followed by rinsing with purified water until neutral. This thoroughly removes unreacted reagents such as residual alkali, urea, and epichlorohydrin, preventing residual substances from interfering with the antibacterial activity of the film, affecting its structural stability, or migrating into the packaged food. The low-temperature drying step at 35–45°C effectively removes internal moisture from the film, ensuring a stable state for use, and prevents oxidation or degradation of the heat-sensitive flavonoids in the vine tea extract, thus guaranteeing the complete preservation of the film's biocompatibility and antibacterial activity.

[0021] The cellulose-based antibacterial hydrogel film loaded with vine tea extract obtained by this invention exhibits good biocompatibility and non-irritating properties, meeting the safety requirements for use in the food packaging field. In food packaging and fruit and vegetable preservation applications, it achieves a synergistic preservation effect of passive barrier and active antibacterial action, effectively inhibiting microbial growth on the surface of packaged food, delaying fruit weight loss and mold growth, and extending the shelf life of food. For example, in strawberry preservation under normal temperature storage conditions of 25℃, this composite film can significantly reduce fruit weight loss and significantly delay the onset of mold compared to pure cellulose hydrogel film and the unpackaged group, demonstrating good industrial application value and market prospects. Attached Figure Description

[0022] 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.

[0023] Figure 1 The images show the physical images of the vine tea extract prepared in this invention and the scanning electron microscope (SEM) morphology images of the composite film. Among them, a is a physical image of the vine tea extract; b is a microscopic morphology image of the pure cellulose hydrogel film (CH); c is a microscopic morphology comparison image of the composite film loaded with 0.1 wt% vine tea extract (CH@0.1% VTE), with a scale bar of 100 nm. Figure 2 The figures show a comparison of the chemical structure and barrier properties of the thin films of each sample in this invention. In the figure, a is a Fourier transform infrared spectrum (FT-IR); b is a comparison of the oxygen transmittance of each sample; and c is a comparison of the water vapor transmittance of each sample. Figure 3 The graph shows the test results of the antibacterial properties of the films of each sample in Example 1 of the present invention against Escherichia coli and Staphylococcus aureus. Figure 4 The images show the preservation effect of the films of each sample on fresh strawberries in Example 1 of this invention. Among them, a is a comparison of the appearance of strawberries in the unpackaged blank group, the pure CH film group and the CH@0.1%VTE composite film group at different storage time points from 0d to 7d under constant temperature storage at 25℃; b is a comparison curve of the weight loss rate of each group of strawberries stored to the 8th day under storage at 25℃. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] Example 1: Preparation of a cellulose-based antibacterial hydrogel film (CH@0.1% VTE) loaded with vine tea extract In this embodiment, the target composite film is prepared according to the following steps, and all process parameters are within the optimal range defined by this invention: (A) Preparation of vine tea extract The dried vine tea was pulverized to 40 mesh (particle size range 20-60 mesh, facilitating the dissolution of active ingredients). 10g was weighed and mixed with 200mL of distilled water (material-to-liquid ratio 1:20, corresponding to 20-50mL of distilled water per gram of dried vine tea). The pH was adjusted to 7.3 with acetic acid (pH range 7.0-7.5). The mixture was soaked at room temperature for 40 minutes (soaking time range 30-60 minutes, ensuring the dried vine tea fully swells and improving subsequent extraction efficiency). The mixture was then placed in a microwave irradiation instrument and treated at 200W for 30 minutes (microwave power range 150-250W, time range 20-40 minutes, utilizing the thermal and non-thermal effects of microwaves to disrupt the cell walls of the vine tea and promote the release of active ingredients). After completion, the mixture was transferred to an ultrasonic extractor and ultrasonically extracted at 150W for 1 hour (ultrasonic power range 100W). The extraction process involves using ultrasonic cavitation at 0–200 W for 0.5–2 hours to further improve the extraction rate of active ingredients. After extraction, the product is first filtered through 150-mesh nylon cloth to remove insoluble residues (filtration mesh range 100–200 mesh), followed by vacuum filtration to obtain a clear filtrate, thus avoiding impurities from affecting subsequent compounding effects. The filtrate is then concentrated under reduced pressure in a 60°C rotary evaporator to a paste-like consistency (concentration temperature range 50–70°C; low-temperature concentration reduces the oxidative degradation of active ingredients in plant extracts). Subsequently, the product is freeze-dried at -30°C and 20 Pa for 20 hours (freeze-drying conditions range: -40–-20°C, vacuum 10–30 Pa, time 12–24 hours, ensuring the dryness of the extract without damaging the active ingredients). The dried product is then ground into powder to obtain the vine tea extract, which is then sealed for later use.

[0030] (B) Preparation of composite films Sodium hydroxide, urea, and deionized water were mixed in a mass ratio of 7:12:77 and stirred until completely dissolved to form a low-temperature cellulose dissolution system. This system can dissolve cellulose at low temperatures without damaging its molecular structure. The system was pre-cooled to -5°C (the pre-cooling temperature should be below -12°C; this condition was used for verification in this example) and maintained in a 0°C ice-water bath (subsequent cellulose dissolution and cross-linking reactions were carried out in an ice-water bath at 0–4°C to ensure the low-temperature dissolution effect of cellulose and prevent cellulose degradation due to increased system temperature). 2g of cellulose was added and stirred vigorously until completely dissolved. The cellulose and epichlorohydrin were then added... Epichlorohydrin was added at a ratio of 1:10 (the mass ratio of cellulose to epichlorohydrin ranges from 10:1 to 5:1), and the mixture was stirred in an ice bath for 30 minutes to initiate the crosslinking reaction (stirring time ranges from 20 to 60 minutes). Epichlorohydrin, as a crosslinking agent, enables the formation of crosslinked structures between cellulose molecules, improving the mechanical properties and water resistance of the film. Subsequently, vine tea extract powder was added at a loading of 0.1 wt% of the cellulose mass (loading ranges from 0.05 to 0.5 wt%, at which ratio the vine tea extract and cellulose matrix exhibit the best synergistic effect, and excessive loading will not lead to a decrease in the mechanical properties of the film). Continue stirring for 30 minutes until homogeneous (stirring time range: 60–120 minutes, to ensure thorough integration of the vine tea extract and cellulose system) to obtain the film-forming solution. Cast the film-forming solution into a glass mold and scrape out a 0.8 mm thick wet film (wet film thickness range: 0.4–1 mm) using a spatula. Allow it to stand at room temperature to solidify, obtaining a hydrogel film. Wash the film three times with a 0.2 mol / L acetic acid solution (acetic acid concentration range: 0.1–0.3 mol / L, washing 2–3 times) to remove residual alkali. Then rinse with purified water until neutral to remove salts formed after neutralization and unreacted urea. Residual reagents such as epichlorohydrin were removed to prevent these residues from interfering with the antibacterial activity of the film, affecting its structural stability, or migrating into the packaged food during use. Finally, the film was dried in a 40°C forced-air drying oven to constant weight (drying temperature range of 35-45°C, which can effectively remove moisture from the film to achieve a stable state for use, and can also prevent the oxidation or degradation of heat-sensitive flavonoid active ingredients (such as dihydromyricetin) in the vine tea extract due to excessive temperature, thereby ensuring the preservation of antibacterial activity). The cellulose-based antibacterial hydrogel film loaded with vine tea extract was obtained and denoted as CH@0.1% VTE.

[0031] Comparative Example 1: Preparation of pure cellulose hydrogel film (CH) This comparative example did not add vine tea extract, and all other preparation steps and process parameters were exactly the same as in Example 1, resulting in a pure cellulose hydrogel film, denoted as CH.

[0032] Comparative Example 2: Preparation of a low-loaded vine tea extract composite film (CH@0.03% VTE) In this comparative example, the loading of vine tea extract was 0.03 wt% of the cellulose mass. The remaining preparation steps and process parameters were exactly the same as in Example 1, and a low-loading composite film was obtained, denoted as CH@0.03% VTE.

[0033] Preparation of a critical loading composite film of vine tea extract (CH@0.05% VTE) in Comparative Example 3 In this comparative example, the loading of vine tea extract was 0.05 wt% of cellulose mass. The remaining preparation steps and process parameters were exactly the same as in Example 1, and a critical loading composite film was obtained, denoted as CH@0.05% VTE.

[0034] Preparation of composite films (CH@0.08% VTE) with loading of vine tea extract in Comparative Example 4 In this comparative example, the loading of vine tea extract was 0.08 wt% of cellulose mass. The remaining preparation steps and process parameters were exactly the same as in Example 1, and a medium-loading composite film was obtained, denoted as CH@0.08% VTE.

[0035] Performance characterization and application effect testing of composite thin films in experimental examples To verify the structural properties, antibacterial properties, and preservation effects of the cellulose-based antibacterial hydrogel film loaded with vine tea extract prepared in this invention, systematic tests were conducted on the films prepared in Example 1 and each comparative example, while an unpackaged blank group was set up as a control.

[0036] 1. Microscopic morphological characterization The microstructure of each group of films was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown. Figure 1 As shown, the pure cellulose hydrogel film (Comparative Example 1, CH) exhibits a typical three-dimensional network structure with clearly visible pores distributed between the networks; the composite film loaded with vine tea extract (VTE) (Example 1, CH@0.1% VTE) shows uniformly distributed fine particles on its surface, with a more compact and continuous structure, indicating that the introduction of VTE enhances the intermolecular interactions within the film and improves its structural integrity. Figure 1 The image also shows a physical picture of the vine tea extract prepared in this embodiment, which is a brownish-yellow powder.

[0037] 2. Chemical structure characterization The chemical structures of each group of thin films were analyzed using Fourier transform infrared spectroscopy (FT-IR), and the results are as follows: Figure 2 As shown in a. (As indicated by...) Figure 2 As shown in Figure a, after loading VTE, some characteristic absorption peaks of the film show a significant shift: among them, the 2897 cm⁻¹ peak... -1The characteristic peak of cellulose at 1660 cm⁻¹ shows a red shift. -1 The increased intensity and slight shift of the characteristic flavonoid peaks in the vicinity indicate the presence of intermolecular hydrogen bonding between VTE and the cellulose matrix. This interaction enables the vine tea extract to be stably dispersed in the three-dimensional network structure of the regenerated cellulose hydrogel, while simultaneously densifying the film structure.

[0038] 3. Barrier performance test The oxygen permeability and water vapor permeability of each group of films were determined according to the national standard method, and the results are as follows: Figure 2 b、 Figure 2 As shown in c. Figure 2 b、 Figure 2 As shown in Figure c, the pure CH film (Comparative Example 1) exhibits the highest oxygen and water vapor permeability values, indicating a relatively loose molecular network. After loading with VTE, the oxygen and water vapor permeability of the composite film significantly decrease, showing a gradual decreasing trend with increasing VTE loading. These results demonstrate that the introduction of VTE fills the pores of the cellulose network through hydrogen bonding, improving the film's density and effectively inhibiting the diffusion of oxygen and water vapor, thus enhancing the material's passive barrier properties.

[0039] 4. Antibacterial performance test Using OD 600 Bacterial growth inhibition assays and gradient dilution plate counting methods were used to systematically evaluate the antibacterial properties of the films against *Escherichia coli* and *Staphylococcus aureus*. Gradient dilution plate counting results showed that the unpackaged blank group had the highest colony count on agar plates, while the colony count of the films containing VTE decreased significantly with increasing VTE concentration. 600 Test results as follows Figure 3 As shown, compared with Comparative Example 1 (CH group), the films containing VTE significantly inhibited the proliferation of Escherichia coli and Staphylococcus aureus (p<0.05), and the antibacterial effect increased with increasing VTE loading. The quantitative antibacterial effects of each group of films against the two pathogenic bacteria are shown in Table 1 below: Table 1. Quantitative antibacterial effects of each group of films against the two pathogenic bacteria.

[0040] The above results indicate that the composite film prepared in this invention has a broad-spectrum and highly efficient inhibitory effect on common foodborne pathogens such as Escherichia coli and Staphylococcus aureus, and can achieve a long-lasting antibacterial effect by stably loading and sustaining the release of vine tea extract through the three-dimensional network structure of cellulose hydrogel.

[0041] 5. Test on the application effect of strawberry preservation The films were applied to the packaging and preservation experiments of fresh strawberries. Fresh strawberries of uniform size, without mechanical damage or pests were selected and packaged using the films prepared in Example 1 and Comparative Example 1, respectively. A blank control group without packaging was also included. The strawberries were stored at 25°C, and their appearance and weight loss rate were observed periodically. The results are as follows: Figure 4 As shown. The results of the visual observation are as follows. Figure 4 As shown, with prolonged storage, the strawberries in each group exhibited varying degrees of quality deterioration: the unpackaged blank control group showed obvious mold and rot on the 3rd day; the Comparative Example 1 (pure CH film) packaged group began to soften on the 4th day and showed obvious mold spots on the 5th day; while the Example 1 (CH@0.1% VTE) composite film packaged group only showed visible mold on the 6th day. The weight loss rate determination results are as follows... Figure 4 As shown, after 8 days of storage, the unpackaged control group had the highest weight loss rate, followed by the packaged group in Comparative Example 1, while the composite film packaged group in Example 1 had the lowest weight loss rate, at only 46%. These results indicate that the composite film prepared in this invention, through the synergistic effect of passive barrier (reducing oxygen and water vapor permeability) and active antibacterial action (slow-release vine tea extract inhibiting microbial growth), can effectively reduce water loss in strawberries, delay fruit softening and mold growth, and significantly extend the shelf life of strawberries, making it suitable for food packaging and fruit and vegetable preservation.

[0042] The cellulose-based antibacterial hydrogel film loaded with vine tea extract prepared by this invention uses renewable and degradable cellulose as the substrate and combines it with natural plant-derived active substances. The preparation process is simple, the reaction conditions are mild, each step is easy to scale up, and the raw materials are widely available and inexpensive. The resulting composite film has excellent antibacterial, barrier, and mechanical properties, good biocompatibility, is non-irritating, and is completely biodegradable, meeting the safety requirements of the food packaging field. It can be widely used in food packaging, fruit and vegetable preservation, and other fields, and has good industrial application value and market prospects.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A cellulose-based antibacterial hydrogel film loaded with vine tea extract, characterized in that, The film uses regenerated cellulose hydrogel as a matrix, with vine tea extract dispersed in the three-dimensional network structure of the regenerated cellulose hydrogel. The extract interacts with cellulose molecules through hydrogen bonds, making the film structure denser. The film has a broad-spectrum inhibitory effect on Escherichia coli and Staphylococcus aureus.

2. The cellulose-based antibacterial hydrogel film loaded with vine tea extract according to claim 1, characterized in that, The loading of vine tea extract in the composite film is 0.05 to 0.5 wt% of the cellulose mass.

3. The cellulose-based antibacterial hydrogel film loaded with vine tea extract according to claim 1, characterized in that, The film is prepared by drying a film-forming solution with a thickness of 0.4 to 1 mm applied by wet film scraping.

4. A method for preparing a cellulose-based antibacterial hydrogel film loaded with vine tea extract as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (A) Preparation of vine tea extract: Dried vine tea was mixed with distilled water, and the pH was adjusted to 7.0-7.5 with acetic acid. After soaking at room temperature, microwave radiation and ultrasonic extraction were performed in sequence. After multi-stage filtration, the filtrate was concentrated, freeze-dried and ground into powder to obtain vine tea extract. (B) Preparation of composite film: Sodium hydroxide, urea and deionized water are mixed to form a solvent system. After pre-cooling, cellulose is added and stirred until completely dissolved. Epichlorohydrin is then added to initiate a cross-linking reaction. Subsequently, the vine tea extract obtained in step (A) is added and stirring is continued. The mixture is cast into a mold, washed and dried to obtain a cellulose-based antibacterial hydrogel film loaded with vine tea extract. Step (B) is performed after step (A) is completed.

5. The preparation method according to claim 4, characterized in that, In step (A), the dried vine tea is pulverized to 20-60 mesh, and the ratio of dried vine tea to distilled water is 20-50 mL of distilled water per gram; the soaking time at room temperature is 30-60 min; the microwave radiation power is 150-250 W for 20-40 min; the ultrasonic extraction power is 100-200 W for 0.5-2 h; the multi-stage filtration is carried out by filtration through 100-200 mesh nylon cloth and vacuum filtration; the concentration is carried out under reduced pressure at 50-70℃; and the freeze-drying is carried out at -40 to -20℃ and a vacuum of 10-30 Pa for 12-24 h.

6. The preparation method according to claim 4, characterized in that, In step (B), the mass ratio of sodium hydroxide, urea, and deionized water is 7:12:77; the pre-cooling temperature is below -12℃, and the cellulose dissolution, cross-linking reaction, and vine tea extract mixing process are all carried out in an ice-water bath at 0-4℃.

7. The preparation method according to claim 4, characterized in that, In step (B), the mass ratio of cellulose to epichlorohydrin is 10:1 to 5:1; after adding epichlorohydrin, stir in an ice bath for 20 to 60 minutes to initiate the cross-linking reaction; after adding vine tea extract, continue stirring for 60 to 120 minutes until the mixture is homogeneous.

8. The preparation method according to claim 4, characterized in that, In step (B), the washing process involves washing the product 2 to 3 times with 0.1 to 0.3 mol / L acetic acid, followed by rinsing with purified water until neutral. The drying process involves drying the product at 35 to 45°C with a forced air dryer until constant weight is achieved.

9. The application of a cellulose-based antibacterial hydrogel film loaded with vine tea extract as described in any one of claims 1 to 3, characterized in that, The film is used to prepare food packaging materials. Through the stable loading and slow release of vine tea extract by the three-dimensional network structure, the synergistic preservation effect of passive barrier and active antibacterial in food packaging or fruit and vegetable preservation is achieved.

10. The application according to claim 9, characterized in that, The food packaging material is a fruit and vegetable preservation film, which can be used to preserve strawberries at room temperature.

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