A CMC zein@MOF aloe self-regulating antibacterial preservative film, method and application thereof

Abstract

This invention discloses a CMC zein@MOF aloe vera self-regulating antibacterial preservation film, its method, and its application, belonging to the technical field of food packaging, self-regulating, and antibacterial preservation films. This composite preservation film uses CMC and zein as the core matrix (mass ratio 4:1), and HKUST-1 nanoparticles (0.2% of the total mass of the core matrix) and aloe vera gel (6% of the total mass of the core matrix) as functional components. Through the synergistic effect of multiple components, it achieves triple preservation effects of physical barrier, active antibacterial activity, and ultraviolet shielding. Its preparation method includes HKUST-1 nanoparticle preparation, aloe vera gel extraction, core matrix solution preparation, film-forming solution preparation, and film drying. The process is simple, cost-controllable, and suitable for large-scale production. The composite film prepared by this invention has a tensile strength of 68.59 MPa, an antibacterial rate of nearly 100% against Escherichia coli and Staphylococcus aureus, a carbon dioxide / oxygen selective permeability of 8.04 g·kg·mmol / (m²·h), excellent biocompatibility, and a soil degradation rate of 54.38% after 60 days. It is mainly used for the preservation of high-moisture fruits such as strawberries, and can extend the shelf life of strawberries to more than 6 days at room temperature of 20-25℃. It effectively solves the problems of existing bio-based films having single function, poor preservation effect, and environmental non-environmental impact, and provides a green and efficient alternative to food preservation packaging, with broad prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the technical field of food packaging, self-regulating, and antibacterial preservation films. Specifically, this invention relates to a self-regulating CMC zein@MOF aloe vera preservation film, its preparation method, and its application in strawberries. Background Technology

[0002] Fresh fruit spoils after harvest due to uncontrolled respiratory metabolism, microbial contamination, and transpiration, resulting in significant economic losses. Traditional commercial food preservation films are mostly petroleum-based, and long-term use not only leads to health problems such as chemical migration and microplastic accumulation but also causes serious environmental pollution due to their non-degradability. Pure natural bio-based films, due to their biodegradability and green safety, have become an important alternative to petroleum-based packaging materials. However, they generally suffer from inherent defects such as insufficient mechanical strength, poor gas and moisture barrier performance, and a lack of antibacterial and antioxidant functions, limiting their practical application in fruit preservation.

[0003] In the existing technology, most studies only focus on single function optimization, lacking synergistic design for multi-dimensional performance improvement. Furthermore, there is a lack of systematic research on the dispersion stability, interfacial interaction, and functional synergistic effect between functional fillers and natural bioactive substances in bio-based matrices, which hinders the industrial application of high-performance bio-based preservation films.

[0004] To address the aforementioned defects and shortcomings in existing technologies, this invention aims to provide a green, safe, highly effective, stable, and easy-to-prepare CMC zein@MOF aloe vera self-regulating antibacterial preservation film. This solves the problems of existing bio-based films having limited functionality, poor structural stability, and inadequate preservation effects, thus meeting the practical application needs of long-term preservation of fresh fruits, environmentally friendly packaging, and large-scale production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this paper provides a CMC zein@MOF aloe vera self-regulating antibacterial preservation film, its method, and its application. This film solves the problems of insufficient mechanical strength, poor gas selectivity, limited antibacterial and antioxidant properties, short preservation period, unstable dispersion of functional components, and complex preparation process of existing bio-based preservation films. The goal is to achieve efficient and long-lasting preservation of fruits, green and biodegradable packaging materials, and large-scale preparation process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A CMC zein@MOF aloe vera self-regulating antibacterial preservation film, its method, and its application, characterized in that it is composed of the following components: The core matrix (CMC and zein), and functional entities (HKUST-1 MOF nanoparticles and aloe vera gel); the mass ratio of each component is: CMC:zein = 4:1, the amount of HKUST-1 nanoparticles added is 0.2% of the total mass of the core matrix, and the amount of aloe vera gel added is 6% of the total mass of the core matrix; Preferably, the HKUST-1 nanoparticles are nanoscale and are prepared by reacting triformic acid with copper nitrate trihydrate. They have selective gas permeability and antibacterial properties, and have characteristic diffraction peaks at 2θ angles of approximately 11.9°, 13.5° and 19.0°, ensuring their structural integrity and functional stability. Preferably, in the core matrix, the viscosity of CMC is 600-3000 mPa·s, and zein is dissolved in a binary solvent system of ethanol and deionized water (volume ratio 3:2). The two are cross-linked by hydrogen bonds to form a composite matrix, which has good film-forming properties, biodegradability and biocompatibility. Preferably, the aloe vera gel is prepared by extracting, homogenizing, filtering, and pasteurizing fresh aloe vera leaves. It is rich in phenolic compounds and polysaccharides, has both antioxidant and antibacterial activities, and contains no toxic or harmful components, thus meeting the safety requirements for food contact materials.

[0007] The preparation method and application of a CMC zein@MOF aloe vera self-regulating antibacterial preservation film as described above are characterized by the following steps: S1: Preparation of HKUST-1 nanoparticles: 1.81 g of copper nitrate trihydrate and 0.86 g of triformic acid were dissolved in 50 mL of anhydrous ethanol. The copper nitrate trihydrate solution was slowly added dropwise to the triformic acid solution. The mixture was stirred at room temperature for 4 hours to form a blue suspension. The mixture was centrifuged at 8000 rpm for 10 minutes, and the precipitate was washed with anhydrous ethanol. Then, it was dried under vacuum at 80 °C for 24 hours to obtain HKUST-1 nanoparticles. Preferably, in step S1, the centrifugation speed is controlled at 8000 rpm for 10 minutes, the washing is performed 2-3 times, and the drying temperature is 80℃ for 24 hours to ensure that the HKUST-1 nanoparticles have high purity, good dispersibility, and retain their inherent structure and antibacterial properties. S2: Preparation of aloe vera gel: Select mature aloe vera leaves, wash them and remove the base, top and thorny edges, immerse them vertically in deionized water for 30 minutes to remove aloin; cut the leaves and remove the green epidermis, take the colorless gel matrix, homogenize it and filter it through 400 mesh nylon cloth, pasteurize it and store it at -18℃ for later use. S3: Preparation of core matrix solution: Dissolve 0.96g CMC in 47mL deionized water and stir in a 75℃ water bath for 30 minutes until completely dissolved; separately dissolve 0.24g zein in a binary solvent system of 12mL ethanol and deionized water (volume ratio 3:2), homogenize, add to the CMC solution, and stir at room temperature for 20 minutes to promote cross-linking of the two to obtain the core matrix solution; S4: Preparation of film-forming solution: Add 0.2% (relative to the total mass of the core matrix) of HKUST-1 nanoparticles and 6% (relative to the total mass of the core matrix) of aloe vera gel to the core matrix solution, mix evenly, and then sonicate for 1 hour to remove air bubbles to obtain the film-forming solution. S5: Preparation of composite film: The film-forming solution is injected into a 10cm×10cm polytetrafluoroethylene mold and dried in a 40℃ oven to form a film, thus obtaining the CMC zein@MOF aloe self-regulating antibacterial and food preservation film.

[0008] Preferably, in step S4, the ultrasonic treatment time is 1 hour to ensure that HKUST-1 nanoparticles and aloe vera gel are uniformly dispersed in the core matrix solution and to avoid agglomeration; in step S5, the drying temperature is controlled at 40°C to ensure that the film is smooth and uniform and does not damage the functional activity of each component.

[0009] The above-mentioned CMC zein@MOF aloe vera self-regulating antibacterial preservation film, method and application are characterized in that the composite preservation film is used for the preservation of high-moisture fruits, specifically for the preservation of strawberries, and can effectively inhibit the growth of microorganisms, delay the browning and softening of strawberries, reduce moisture loss and extend the shelf life of strawberries.

[0010] Preferably, in the application, the composite preservation film is used to seal the opening of the container for storing strawberries. When the strawberries are placed at room temperature of 20–25°C, the shelf life of the strawberries can be extended to more than 6 days, and the strawberries still maintain a good appearance, firmness and flavor, with a weight loss rate of only 10.36%.

[0011] Performance Advantages: The CMZHA composite film prepared by this invention exhibits excellent comprehensive properties, with a tensile strength of 68.59 MPa and an elongation at break of 21.13%, far exceeding the minimum requirements for food packaging materials. It demonstrates nearly 100% inhibition rate against Escherichia coli and Staphylococcus aureus, and an inhibition zone diameter of 26.4 mm against mold, exhibiting significant antibacterial and antifungal effects. The selective permeability of carbon dioxide / oxygen reaches 8.04 g·kg·mmol / (m²). 2With an oxygen permeability as low as 6.22 mmol / kg, it can self-regulate to create a low-oxygen, high-carbon dioxide microenvironment, inhibiting the respiration and metabolism of fruits. At the same time, it has excellent ultraviolet blocking performance and thermal stability, solving the pain points of existing bio-based films with single function and insufficient performance, and realizing the triple synergistic preservation of physical barrier, active antibacterial and ultraviolet shielding.

[0012] Green and safe advantages: This invention uses natural biodegradable materials such as CMC, zein, and aloe vera. The HKUST-1 nanoparticle preparation process is free of toxic solvents and introduces no harmful components, thus avoiding food contamination and environmental hazards at the source. The composite film has good biocompatibility and is non-cytotoxic to GES-1 cells (cell survival rate ≥98.78%). Acute toxicity tests show that it does not cause pathological damage to mouse organs, meeting the safety standards for food contact materials. At the same time, the film degrades by 54.38% in soil after 60 days, effectively reducing white pollution and aligning with the development trend of green and environmentally friendly industries.

[0013] Process advantages: The preparation method of this invention is simple and easy to implement, requiring no complex equipment. All steps are carried out at room temperature or medium and low temperature, with low operation threshold and controllable cost. The components are uniformly dispersed without obvious agglomeration. The preparation process can be scaled up, solving the problem that the existing high-performance bio-based thin film preparation process is complex and difficult to industrialize.

[0014] Application Advantages: The composite film of this invention is mainly used for the preservation of high-moisture fruits such as strawberries. It has a clear application scenario and strong practicality. At room temperature of 20-25℃, it can extend the shelf life of strawberries to more than 6 days. Compared with the blank control group, the weight loss rate is reduced by 22.09% and the decrease in hardness is reduced by 24.6%, which can effectively reduce post-harvest fruit loss. At the same time, the amount of aloe vera gel added to the film can be adjusted according to actual needs to adapt to the preservation requirements of different fruits, and it has broad market promotion prospects. Attached Figure Description

[0015] Figure 1 Cross-sectional SEM images of four types of thin films: CMC, CMZ, CMZH, and CMZHA.

[0016] Figure 2 XRD patterns of HKUST-1, CMZH, and CMZHA thin films.

[0017] Figure 3 This is a comparison of the antibacterial properties of CMZHA film and the control group (including inhibition zones and colony count results).

[0018] Figure 4 Tensile stress-strain curves for four types of films (showing tensile strength and elongation at break).

[0019] Figure 5 Comparison of appearance changes between CMZHA film and control group used for strawberry preservation (6 days of storage).

[0020] Figure 6 The curves show the changes in weight loss rate, firmness, TSS, and pH value of strawberries during storage.

[0021] Figure 7 The graph shows the soil degradation rate curve and cytotoxicity test results of the CMZHA film. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the following description, in conjunction with the accompanying drawings and embodiments, will provide a more detailed explanation of the invention, but does not limit the scope of protection of this invention. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0023] Example 1: The preparation method for HKUST-1 nanoparticles includes the following steps: (1) Dissolve 1.81g of copper nitrate trihydrate Cu(NO3)2·3H2O and 0.86g of triformic acid in 50mL of anhydrous ethanol and stir until completely dissolved to obtain copper nitrate trihydrate ethanol solution and triformic acid ethanol solution. (2) The copper nitrate trihydrate ethanol solution was slowly added dropwise to the triformic acid ethanol solution, and stirred continuously at room temperature for 4 hours to form a blue suspension; (3) Place the blue suspension in a centrifuge and centrifuge at 8000 rpm for 10 minutes to collect the precipitate; wash the precipitate twice with anhydrous ethanol to remove unreacted raw materials; (4) Place the washed precipitate in an 80℃ vacuum oven and dry for 24 hours to obtain nano-sized HKUST-1 particles for later use.

[0024] Example 2: The preparation method for aloe vera gel includes the following steps: (1) Select mature aloe vera leaves that are consistent in size, color and freshness. First, wash them thoroughly with tap water, and then use deionized water to remove surface dirt. (2) Cut off about 3cm from the base of the leaf, 5-10cm from the top, and the thorny edge. Immerse the trimmed leaf vertically in deionized water for 30 minutes to remove the aloin. (3) Cut the soaked leaves into sections, remove the double green epidermis to obtain a colorless gel matrix, and drain excess water. (4) Homogenize the gel matrix into a particle-free substance using a homogenizer, filter it through a 400-mesh nylon cloth to remove residual impurities, and obtain a transparent aloe vera gel. (5) Pasteurize the aloe vera gel and store it at -18°C for later use.

[0025] Example 3: The preparation method of CMZHA composite food preservation film includes the following steps: (1) Preparation of core matrix solution: Dissolve 0.96g CMC (viscosity 600-3000 mPa·s) in 47mL deionized water and stir continuously in a 75℃ water bath for 30 minutes until completely dissolved to obtain CMC solution; Take another 0.24g zein and dissolve it in a binary solvent system of 12mL ethanol and deionized water (volume ratio 3:2). After stirring and homogenizing, immediately add it to the CMC solution and stir at room temperature for 20 minutes to promote cross-linking of CMC and zein to obtain core matrix solution; (2) Preparation of film-forming solution: 0.0024 g (0.2% of the total mass of the core matrix) of HKUST-1 nanoparticles prepared in Example 1 and 0.072 g (6% of the total mass of the core matrix) of aloe vera gel prepared in Example 2 were added to the core matrix solution. After mixing evenly, the solution was ultrasonically treated for 1 hour to remove air bubbles and obtain film-forming solution. (3) Preparation of composite film: The film-forming liquid is slowly injected into a 10cm×10cm polytetrafluoroethylene mold to ensure that the film-forming liquid is spread evenly; the mold is placed in a 40℃ oven and dried for 12 hours. After taking it out, the mold is peeled off to obtain CMC zein@MOF aloe self-regulating antibacterial preservation film (CMZHA film).

[0026] Example 4: Preparation of composite films with different aloe vera content: The difference between this example and Example 3 is that the amount of aloe vera gel added is 2%, 4%, 8%, and 10% of the total mass of the core matrix, respectively. The remaining steps are exactly the same as in Example 3. CMZHA composite films with different aloe vera contents are prepared to compare the effect of different aloe vera additions on film performance.

[0027] Comparative Example 1: Preparation of blank control group film (CM film): The difference between this comparative example and Example 3 is that only CMC single matrix film is prepared, without adding zein, HKUST-1 nanoparticles and aloe vera gel. The remaining steps are exactly the same as in Example 3 to obtain CM film, which is used to compare the performance advantages of the composite film of the present invention.

[0028] Comparative Example 2: Preparation of CMC zein composite film (CMZ film): The difference between this comparative example and Example 3 is that HKUST-1 nanoparticles and aloe vera gel are not added. Only CMC zein composite film is prepared. The remaining steps are exactly the same as in Example 3 to obtain CMZ film, which is used to compare the synergistic effect of HKUST-1 and aloe vera.

[0029] Comparative Example 3: Preparation of CMC zein@MOF aloe self-regulating antibacterial preservation film (CMZH film): The difference between this comparative example and Example 3 is that aloe vera gel is not added. Only CMC zein@MOF aloe vera self-regulating antibacterial preservation film is prepared. The remaining steps are exactly the same as in Example 3 to obtain CMZH film, which is used to compare the effect of aloe vera gel.

[0030] Comparative Example 4: Conventional PE film (existing technology control group): This comparative example uses commercially available conventional polyethylene (PE) film as an existing technology control group to compare the preservation effect and environmental performance of the composite film of the present invention.

[0031] The products obtained in Examples 1-4 and Comparative Examples 1-4 were subjected to performance tests, and the morphological characterization test methods and results are as follows:

[0032] Mechanical property testing: The morphology and structure of the product were characterized using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 1-2 As shown. By Figure 1 It can be seen that the CM film has a relatively smooth and uniform cross-section; the CMZ film exhibits phase separation and voids due to the thermodynamic incompatibility between CMC and zein; the CMZH film has some void filling, but still has a small number of uneven areas; while the CMZHA film prepared in Example 3 has the best void and depression filling effect in its cross-section, a more dense and regular microstructure, and uniform dispersion of HKUST-1 nanoparticles and aloe vera gel without obvious agglomeration. Figure 2 It was found that HKUST-1 exhibited characteristic diffraction peaks at approximately 11.9°, 13.5°, and 19.0° at 2θ, and these peaks appeared in both the CMZH and CMZHA films, confirming the successful incorporation of HKUST-1 into the matrix. The XRD pattern of the CMZHA film showed superposition of characteristic peaks from each component, indicating a good interfacial interaction between CMC, zein, HKUST-1, and aloe vera. XPS analysis results showed that Cu in the CMZHA film... ²+ and Cu +The binding energy was significantly lower than that of HKUST-1, confirming that the copper ions in HKUST-1 formed coordination bonds with the active functional groups in the CMC zein matrix and aloe vera, thus enhancing the structural stability of the film.

[0033] Antibacterial and antifungal performance tests: Antibacterial performance was tested using the plate count method, with *Escherichia coli* and *Staphylococcus aureus* as model organisms; antifungal performance was tested using the inhibition zone method, with *Penicillium digitatum* as the test strain. Results are as follows: Figure 3 As shown in the figure, the films of Comparative Examples 1 and 2 showed no significant antibacterial activity; the CMZH film of Comparative Example 3 had inhibition rates of 79.25% and 77.78% against Escherichia coli and Staphylococcus aureus, respectively, with no significant antifungal effect; the CMZHA film of Example 3 had inhibition rates of nearly 100% against both Escherichia coli and Staphylococcus aureus, and the inhibition zone diameter against mold reached 26.4 mm, demonstrating significant antibacterial and antifungal effects; in Example 4, the higher the amount of aloe vera added, the better the antibacterial effect, but there was no significant difference between 8% and 10% additions and 6%, proving that 6% aloe vera addition can achieve the best balance between therapeutic effect and material utilization.

[0034] Gas permeability test: Oxygen permeability (OP) was determined by titration according to Chinese National Standard GB 5009.227-2016, and carbon dioxide permeability (CDP) was determined by gravimetric method. The results showed that the carbon dioxide / oxygen selective permeability of the CMZHA membrane in Example 3 reached 8.04 g·kg·mmol / (m³). ² The OP value was 6.22 mmol / kg, and the CDP value was 50.97 g / (m³). ² ·h); Compared with Comparative Example 1 (CMC film: selectivity=5.08, OP=9.11, CDP=49.47), the selectivity increased by 58.3% and the OP decreased by 31.7%, indicating that the CMZHA film can self-regulate to create a low-oxygen, high-carbon dioxide microenvironment and inhibit the respiration and metabolism of fruits.

[0035] Biocompatibility and degradation tests: Cytotoxicity was assessed using the CCK-8 assay, and the results are as follows: Figure 7 As shown, the CMZHA film of Example 3 has no obvious toxicity to GES-1 cells. When the concentration reaches 200 mg / L, the cell survival rate is still 98.78%, which meets the safety standards for food contact materials. The degradation rate was tested by the soil burial method. The results showed that the degradation rate of the CMZHA film in the soil reached 54.38% after 60 days, while the PE film of Comparative Example 4 showed no obvious degradation. This proves that the film of the present invention has good degradability and is green and environmentally friendly.

[0036] Application performance testing Strawberries with intact skin, uniform ripeness, and no mechanical damage were selected and randomly divided into 5 groups: blank control group (CK, no packaging), comparative example 1 (CMC film group), comparative example 3 (CMZH film group), comparative example 4 (PE film group), and example 3 (CMZHA film group). Each group had the same number of strawberries. All strawberries were stored at room temperature (20–25℃). The appearance, weight loss rate, firmness, total soluble solids (TSS), and pH value of the strawberries were observed and recorded periodically. The results are as follows: Figure 5-6 As shown.

[0037] Depend on Figure 5 It can be seen that after 6 days of storage, the strawberries in the CK and CMC film groups were completely rotten, the strawberries in the CMZH film group were severely rotten, the strawberries in the PE film group showed partial rot, while the strawberries in the CMZHA film group only showed slight skin shrinkage, and most of them still maintained marketable freshness; Figure 6 The results showed that after 6 days of storage, the weight loss rate of strawberries in the CMZHA film group was only 10.36%, a decrease of 22.09% compared to the CK group (32.45%); the hardness was 0.87 N, an increase of 61.1% compared to the CK group (0.54 N); the TSS decreased the least, 7.62% higher than the CK group and 6.33% higher than the PE group; and the pH value changed the most gradually, maintaining the original flavor of the strawberries. The experiment demonstrated that the CMZHA film can effectively delay strawberry spoilage, extending the shelf life of strawberries to more than 6 days, with a significantly better preservation effect than the existing technology control group.

[0038] In summary, this invention successfully prepared a CMZHA composite preservation film by constructing a synergistic composite system of "CMC zein core matrix and MOF aloe functional guest". This film, through hydrogen bonding and coordination between multiple components, solves the problems of single function, poor structural stability, and inadequate preservation effect of existing bio-based films, while also possessing excellent mechanical properties, antibacterial and antifungal properties, gas regulation properties, biocompatibility, and biodegradability. The preparation method of this invention is simple, cost-effective, and can be mass-produced. The prepared composite film has significant advantages in the preservation of high-moisture fruits such as strawberries, effectively reducing post-harvest fruit losses and providing a green alternative to petroleum-based packaging materials, with broad application prospects.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A CMC zein@MOF aloe vera self-regulating antibacterial preservation film, its method, and its application, characterized in that, It is composed of the following components: CMC, zein, MOF and natural aloe vera gel; the natural aloe vera gel is obtained by filtration and drying from aloe vera leaves using a slicing method.

2. The CMC zein@MOF aloe vera self-regulating antibacterial preservation film, method, and application as described in claim 1, characterized in that, Carboxymethyl cellulose (CMC) and zein were selected as the basic framework, with a mass ratio of 4:

1.

3. The CMC zein@MOF aloe vera self-regulating antibacterial preservation film, method, and application according to claim 1, characterized in that, The MOF is nanoscale and the addition amount is 0-0.2%.

4. The CMC zein@MOF aloe vera self-regulating antibacterial preservation film, method, and application according to claim 1, characterized in that, The amount of aloe vera gel added is 0-10%.

5. A method and application for preparing a CMC zein@MOF aloe vera self-regulating antibacterial preservative film as described in any one of claims 1-4, characterized in that, Including the following steps: a. Preparation of CMC solution: Dissolve 0.96 g of CMC in 47 mL of deionized water and stir in a 75°C water bath for 30 minutes; b. Preparation of zein solution: 0.24 g of zein was dissolved in a binary solvent system of ethanol and water (total volume 12 mL, volume ratio 3:2); c. MOF Preparation: 1.81 g of Cu(NO3)2·3H2O and 0.86 g of triformic acid were dissolved separately in 50 mL of anhydrous ethanol. The Cu(NO3)2 solution was then slowly added dropwise to the triformic acid solution, and the mixture was stirred at room temperature for 4 hours to ensure complete reaction, forming a blue suspension. The suspension was centrifuged at 8000 rpm for 10 minutes and then washed with anhydrous ethanol. The suspension was dried under vacuum at 80 ºC for 24 hours to obtain nanoscale MOFs. d. Aloe vera gel preparation: Select mature aloe vera leaves, wash and trim them, and soak them in deionized water for 30 minutes to obtain a colorless gel matrix. Filter the water, homogenize the gel using a homogenizer to obtain a transparent aloe vera gel, and then dry it. e. Add the zein solution to the CMC solution and stir at room temperature for 20 minutes. Then, add MOF and aloe vera gel (0-10% by mass) sequentially to the CMC-zein mixture. After thorough mixing, sonicate for 1 hour, inject into a PTFE mold, and heat in a 40°C oven to form a smooth and homogeneous film. As controls, films containing only CMC (excluding HKUST-1 and zein) (CM) and films containing CMC-zein (excluding HKUST-1) (CMZ) were prepared.

6. The CMC zein@MOF aloe vera self-regulating antibacterial preservation film, method, and application as described in any one of claims 1-4, characterized in that, The CMC zein@MOF natural aloe vera gel has a fruit preservation effect.

7. The application according to claim 6, characterized in that, The fruit mentioned is strawberry, which has a shelf life of 6 days.

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