An edible antibacterial packaging film suitable for cold chain storage and transportation, its preparation method and application

Abstract

This invention relates to an edible antibacterial packaging film suitable for cold chain storage and transportation, its preparation method, and its application, belonging to the field of food preservation technology. This invention provides an edible antibacterial packaging film suitable for cold chain storage and transportation, comprising a continuous phase matrix and a cyclodextrin metal-organic framework dispersed therein; the continuous phase matrix is ​​a biodegradable polymer, and the cyclodextrin metal-organic framework is loaded with carvacrol and Fe. 3+ Utilizing the humidity-responsive characteristics of cyclodextrin metal-organic framework pores and Fe... 3+ The photoresponsive properties of the carvacrol complex enable intelligent regulation of the release of antibacterial substances and the antibacterial effect, thereby achieving controllable, efficient, and precise antibacterial action in food under complex storage conditions.

Description

Technical Field

[0001] This invention belongs to the field of food preservation technology, and in particular relates to an edible antibacterial packaging film suitable for cold chain storage and transportation, its preparation method and application. Background Technology

[0002] Foodborne microbial contamination, widespread in the food supply chain, is a significant threat to public health and food safety. Fresh foods (such as fruits, vegetables, meat, and seafood) are highly susceptible to microbial adhesion and contamination during storage, transportation, and sales, leading to spoilage, significant economic losses, and resource waste. While traditional plastic packaging materials offer some physical barrier function, their non-degradability and release of endocrine disruptors are increasingly drawing public attention. Existing antimicrobial packaging faces the prominent problem of limited effective ingredient release behavior, difficulty in sensing environmental changes and releasing antimicrobial agents on demand, and inability to adapt to the complex temperature and humidity fluctuations during the storage and transportation of fresh products.

[0003] In actual cold chain storage and transportation scenarios, fresh food often faces dual environmental changes: on the one hand, temperature fluctuations (such as refrigeration chain breaks) can lead to accelerated microbial growth; on the other hand, tissue fluid seepage or condensation during refrigeration can significantly increase the humidity of the microenvironment inside the packaging. However, most traditional active packaging materials rely on only a single response mechanism (such as responding only to temperature or only to humidity), making it difficult to achieve synergistic antibacterial action under multiple environmental stimuli of "light and humidity". Although photodynamic antibacterial technology has the advantage of broad-spectrum antibacterial activity, its light response efficiency is limited by light conditions, making it difficult to maintain effective antibacterial activity in the absence of light or in low light environments; while humidity-responsive materials can accelerate the release of antibacterial agents in high humidity environments, they lack sufficient basic antibacterial capabilities.

[0004] Carvacrol (CAR), a natural phenolic monoterpene compound, has been recognized by the US FDA as a GRAS-grade food additive. It possesses broad-spectrum antibacterial activity and good safety, making it an ideal antimicrobial active ingredient for developing active food packaging. However, using carvacrol alone has inherent drawbacks such as low photodynamic efficiency, high volatility, and poor stability, making it difficult to meet practical application requirements.

[0005] Therefore, there is an urgent need to develop a novel active packaging material that combines photodynamic antibacterial activity with humidity-responsive controlled release function, good biosafety, and biodegradability to solve the problem of microbial risk control in cold chain fresh food. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an edible packaging antibacterial film suitable for cold chain storage and transportation and its application. The antibacterial film, through the synergistic effect of a carrier and antibacterial substances, can provide basic antibacterial activity in the absence of light, and exhibit stronger antibacterial activity under light conditions. Simultaneously, it can release antibacterial substances when humidity increases, achieving precise release of antibacterial substances at the food interface. Through a dual synergistic mechanism of "photoresponsive sterilization" and "humidity-responsive release," it achieves all-weather, controllable, and highly efficient inhibition of microorganisms on the surface of cold chain fresh food.

[0007] Another object of the present invention is to provide a method for preparing the antibacterial film and its application.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an edible packaging antibacterial film suitable for cold chain storage and transportation, comprising a continuous phase matrix and a cyclodextrin metal-organic framework dispersed therein; the continuous phase matrix is ​​a biodegradable polymer, and the cyclodextrin metal-organic framework is loaded with carvacrol and Fe. 3+ .

[0009] Preferably, the carvacrol and Fe 3+ The mass ratio is 1:(1~5), and the mass ratio of carvacrol to cyclodextrin metal-organic framework is 1:(0.5~2).

[0010] Preferably, the degradable polymer comprises a blend of polyvinyl alcohol and chitosan, and the cyclodextrin metal-organic framework is composed of γ-cyclodextrin and K+. + Formed through self-assembly.

[0011] Preferably, it is loaded with carvacrol and Fe 3+ The mass-to-volume ratio of the cyclodextrin metal-organic framework blend with polyvinyl alcohol and chitosan is (0.5~5) g:100mL; the blend of polyvinyl alcohol and chitosan is obtained by mixing polyvinyl alcohol solution and chitosan solution at a volume ratio of (5:5)~(9:1); the concentration of the polyvinyl alcohol solution is 4~6g / 100mL, and the concentration of the chitosan solution is 2~4g / 100mL.

[0012] The present invention also provides a method for preparing the antibacterial film, comprising the following steps: Carvacrol, cyclodextrin metal-organic framework and Fe 3+ The mixture was blended in anhydrous ethanol, the reaction was shaken, the precipitate was collected and dried to obtain CAR-Fe. 3+ @CD-MOF inclusion compound; CAR-Fe 3+ @CD-MOF inclusion complexes are dispersed in a biodegradable polymer, defoamed, cast, and dried to form a film.

[0013] Preferably, the preparation method of the cyclodextrin metal-organic framework is the methanol vapor diffusion method.

[0014] Preferably, the oscillation reaction is carried out at a temperature of 45-55°C, a rotation speed of 150-250 rpm, and a time of 20-28 h; during the film drying process, the drying temperature is 35-50°C and the drying time is 8-24 h.

[0015] The present invention also provides the application of the antibacterial film or the preparation method in the preparation of food preservation products.

[0016] The present invention also provides the application of the antibacterial film or the antibacterial film prepared by the preparation method in combination with light in food preservation. The light source is 405nm blue light or 400~500nm visible light, the light intensity is 5~50W, the light exposure time is 0.5~2h, and the ambient temperature of the light exposure operation is 0~8℃.

[0017] Preferably, the food includes fresh food and / or ready-to-eat products; the fresh food includes livestock and poultry meat and / or seafood; the food also includes food stored and transported under cold chain conditions.

[0018] The beneficial effects of this invention are: This invention uses a cyclodextrin metal-organic framework (CD-MOF) as a carrier to load the natural antibacterial agent carvacrol (CAR), and introduces Fe... 3+ As a photodynamic synergist, it achieves the sustained release of carvacrol and Fe... 3+ The photodynamic synergistic antibacterial effect significantly enhances the yield of reactive oxygen species and the antibacterial effect. Compared with materials that rely solely on carvacrol volatilization for antibacterial activity, it exhibits superior antibacterial activity, especially showing a significant advantage against the difficult-to-inhibit Pseudomonas spp. It demonstrates even more significant antibacterial activity under 405nm blue light excitation.

[0019] This invention achieves long-term release of CAR through a sustained-release system, exhibiting excellent inhibitory effects against eight common bacteria. In the preservation applications of pork and salmon, the shelf life of pork and salmon was extended to 8 days and 4 days respectively, far exceeding that of the control group and traditional polyethylene film packaging. It also inhibits the growth of spoilage bacteria and protein decomposition, maintaining the good freshness and quality of fresh food during complex storage and transportation processes such as cold chain low-temperature and variable-temperature storage.

[0020] The substrates selected in this invention, namely "degradable polymers and cyclodextrins", are both green, non-toxic, and edible materials with good biocompatibility and safety. They meet the hygiene standards for food contact materials, reduce plastic pollution, ensure food safety, and are in line with the current development trend of green packaging materials. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the technical solution of the present invention.

[0022] Figure 2 For Experiment 2, different concentrations of Fe 3+ The effects of 405 nm light and darkness on the growth of three Pseudomonas species were investigated; A was *Pseudomonas chicorifolia*, B was *Pseudomonas putida*, and C was *Pseudomonas aeruginosa*.

[0023] Figure 3 In Experiment 3, carvacrol was reacted with different concentrations of Fe. 3+ The effects of compound treatments on the growth and inhibition rate of *Pseudomonas chicory* under 405nm light and darkness were investigated; among them, the Light and Dark groups showed better results. This indicates that P < 0.05. ns indicates P < 0.001, and ns indicates P > 0.05; any two groups sharing the same lowercase letter indicate P > 0.05, and any two groups not sharing the same lowercase letter indicate P < 0.05.

[0024] Figure 4 In Experiment 3, carvacrol was reacted with different concentrations of Fe. 3+ The effects of compound treatments on the growth and inhibition rate of *Pseudomonas putida* under 405nm light and darkness were investigated; among them, the Light and Dark groups showed the best results. This indicates that P < 0.01. ns indicates P < 0.001, and ns indicates P > 0.05; any two groups sharing the same lowercase letter indicate P > 0.05, and any two groups not sharing the same lowercase letter indicate P < 0.05.

[0025] Figure 5 In Experiment 3, carvacrol was reacted with different concentrations of Fe. 3+ The effects of the combined treatment on the growth and inhibition rate of *Pseudomonas aeruginosa* under 405nm light and darkness were investigated; among them, the Light and Dark groups showed the best results. This indicates that P < 0.05. This indicates that P < 0.01. ns indicates P < 0.001, and ns indicates P > 0.05; any two groups sharing the same lowercase letter indicate P > 0.05, and any two groups not sharing the same lowercase letter indicate P < 0.05.

[0026] Figure 6 For example 4, carvacrol-Fe was loaded. 3+Scanning electron microscope (SEM) images of CD-MOF before and after processing; where A is the actual CD-MOF image, B is the CD-MOF SEM image, and C is the CAR-Fe... 3+ @Image of the CD-MOF inclusion complex, where D stands for CAR-Fe 3+ Scanning electron microscope image of the CD-MOF inclusion complex.

[0027] Figure 7 The images show physical images (first layer) and scanning electron microscope (SEM) images (second and third layers) of the antibacterial films with different concentrations in Experiment Example 4; in the second and third layers, A represents 0% CAR-Fe. 3+ @CD-MOF / PVA-CS antibacterial film (Comparative Example 1), B is 0.75% CAR-Fe 3+ @CD-MOF / PVA-CS antibacterial film (Example 1), C is 1.5% CAR-Fe 3+ @CD-MOF / PVA-CS antibacterial film (Example 2), D is 3% CAR-Fe 3+ @CD-MOF / PVA-CS antibacterial film (Example 3).

[0028] Figure 8 For CAR-Fe in Experimental Example 4 3+ Infrared spectra of the CD-MOF / PVA-CS antibacterial film and its components.

[0029] Figure 9 For CAR-Fe in Experimental Example 4 3+ X-ray diffraction patterns of the CD-MOF / PVA-CS antibacterial film and its components.

[0030] Figure 10 For CAR-Fe in Experimental Example 4 3+ Thermogravimetric analysis of the CD-MOF / PVA-CS antibacterial film and its components.

[0031] Figure 11 The transmittance of the antibacterial films with different contents in Experiment Example 4 is shown.

[0032] Figure 12 The water contact angle of the antibacterial films with different contents in Experiment Example 6.

[0033] Figure 13 P represents the water vapor transmission rate of antibacterial films with different contents in Experiment Example 6; where any two groups have the same lowercase letter, P > 0.05, and no two groups have the same lowercase letter, P < 0.05.

[0034] Figure 14 It is the release rate of carvacrol in the antibacterial film under different relative humidity conditions in Experiment Example 7.

[0035] Figure 15 The results in Experiment 8 show the antibacterial effects of different amounts of antibacterial film on Escherichia coli and Staphylococcus aureus before and after blue light irradiation. Figure 16 This refers to the effect of the antibacterial film on the low-temperature preservation of pork in Experiment Example 9.

[0036] Figure 17 This refers to the effect of the antibacterial film on the low-temperature preservation of salmon in Experiment Example 9.

[0037] Figure 18 This refers to the effect of the antibacterial film on the temperature-dependent preservation of pork in Experiment Example 10.

[0038] Figure 19 This shows the changes in various indicators of pork after temperature treatment in Experiment Example 10; from left to right and top to bottom, they are L... Value, a Value, b Value, weight loss rate, pH value, total bacterial count, and volatile basic nitrogen content.

[0039] Figure 20 This is an analysis of the species composition of the surface microbial community of pork under different storage conditions in Experiment Example 11; where A represents the phylum level and B represents the genus level. Detailed Implementation

[0040] This invention provides an edible packaging antibacterial film suitable for cold chain storage and transportation (also known as "an edible packaging antibacterial film with a light / humidity synergistic response suitable for cold chain storage and transportation"), comprising a continuous phase matrix and a cyclodextrin metal-organic framework dispersed therein; the continuous phase matrix is ​​a biodegradable polymer, and the cyclodextrin metal-organic framework is loaded with carvacrol and Fe. 3+ .

[0041] In this invention, the biodegradable polymer preferably comprises a blend of polyvinyl alcohol and chitosan, wherein the blend of polyvinyl alcohol and chitosan is obtained by mixing a polyvinyl alcohol solution and a chitosan solution at a volume ratio of (5:5) to (9:1), and the volume ratio is more preferably 5:5, 8:5, 7:3, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1; the concentration of the polyvinyl alcohol solution before mixing is preferably 4 to 6 g / 100 mL, more preferably 4 g / 100 mL, 5 g / 100 mL or 6 g / 100 mL, and the concentration of the chitosan solution is preferably 2 to 4 g / 100 mL, more preferably 2 g / 100 mL, 3 g / 100 mL or 4 g / 100 mL.

[0042] In this invention, the cyclodextrin metal-organic framework is preferably composed of γ-cyclodextrin and K+. + Self-assembly formed, the K +The preferred source is potassium hydroxide. The γ-cyclodextrin and K... + The preferred molar ratio is 1:(6~10), more preferably 1:6, 1:8 or 1:10.

[0043] Loaded with carvacrol and Fe 3+ The preferred mass-to-volume ratio of the blend of cyclodextrin metal-organic framework with polyvinyl alcohol and chitosan is (0.5~5) g:100 mL, more preferably 0.5 g:100 mL, 0.75 g:100 mL, 1 g:100 mL, 1.5 g:100 mL, 2 g:100 mL, 2.5 g:100 mL, 3 g:100 mL, 4 g:100 mL or 5 g:100 mL.

[0044] In this invention, the carvacrol and Fe 3+ The preferred mass ratio is 1:(1~5), more preferably 1:1, 1:2, 1:3, 1:4 or 1:5, and the preferred mass ratio of carvacrol to cyclodextrin metal-organic framework is 1:(0.5~2), more preferably 1:0.5, 1:1, 1:1.5 or 1:2.

[0045] In this invention, the cyclodextrin metal-organic framework (CD-MOF) is anchored in the continuous phase matrix through hydrogen bonding and coordination. The CD-MOF has a three-dimensional porous structure, and the natural antibacterial agents carvacrol and Fe are co-loaded within its pores through host-guest inclusion interactions. 3+ Ions form a ternary composite structure of "carrier-coordinating ion-antibacterial agent"; among which, Fe 3+ Coordination with the phenolic hydroxyl groups of carvacrol confines carvacrol within the hydrophobic cavity of CD-MOF, forming an integrated "loading-confinement-stability" unit. Under cold chain low-temperature and variable-temperature storage conditions, the antibacterial film exhibits the following dual-response model: (a) Humidity-responsive release model: When the relative humidity of the cold chain environment rises above 75%, the CD-MOF pores undergo hydrophilic expansion, and the pore structure changes from a compact state to a loose state, triggering the directional release and diffusion of carvacrol from within the pores to the film surface and food interface, significantly accelerating the release rate; when the relative humidity is below 43%, carvacrol release is inhibited, achieving long-term preservation under low-humidity cold chain conditions. (b) Photodynamic synergistic sterilization model: Under external light irradiation, Fe... 3+ / Carvacrol complexes enhance light absorption through ligand-metal charge transfer (LMCT) effect, mediating the generation of reactive oxygen species (ROS) through a Type I photodynamic pathway cascade, achieving photoexcitation-electron transfer-multi-target synergistic bactericidal action.

[0046] The present invention also provides a method for preparing the antibacterial film, comprising the following steps: Carvacrol, cyclodextrin metal-organic framework and Fe 3+The mixture was blended in anhydrous ethanol, the reaction was shaken, the precipitate was collected and dried to obtain CAR-Fe. 3+ @CD-MOF inclusion compound; CAR-Fe 3+ @CD-MOF inclusion complexes are dispersed in a biodegradable polymer, defoamed, cast, and dried to form a film.

[0047] In this invention, the inclusion complex is preferably prepared by solution blending, in which carvacrol, cyclodextrin metal-organic framework and Fe are combined. 3+ In anhydrous ethanol, carvacrol, cyclodextrin metal-organic framework and Fe 3+ The preferred total solids mass to anhydrous ethanol volume ratio is 1 g:(8~12) mL, more preferably 1 g:8 mL, 1 g:10 mL, or 1 g:12 mL. After blending, ultrasonic treatment is preferably performed to promote the dissolution of each raw material. The present invention does not specifically limit the ultrasonic treatment parameters; any ultrasonic parameters that promote the dissolution of each substance can be used. In some embodiments, the ultrasonic time can be selected as 30 min. After the substances are dissolved, an oscillation reaction is performed to promote the formation of inclusion complexes. The preferred temperature of the oscillation reaction is 45~55℃, more preferably 45℃, 50℃, or 55℃; the preferred rotation speed is 150~250 rpm, more preferably 150 rpm, 200 rpm, or 250 rpm; and the preferred time is 20~28 h, more preferably 20 h, 22 h, 24 h, 26 h, or 28 h. After the shaking reaction, the precipitate is collected. This invention does not specifically limit the method of collecting the precipitate. In some embodiments, centrifugation to remove the supernatant can be used to collect the precipitate. This invention does not specifically limit the centrifugation parameters; conventional centrifugation parameters in the art are acceptable. In some embodiments, centrifugation at 8000 rpm for 5 minutes at 20°C can be used. After obtaining the precipitate, it is preferably washed three times with anhydrous ethanol to remove unbound carvacrol, and then dried. The drying is preferably performed under vacuum at 35-45°C (e.g., 35°C, 40°C, or 45°C) for 3.5-4.5 hours (3.5 hours, 4 hours, or 4.5 hours). After drying, CAR-Fe is obtained. 3+ @CD-MOF inclusion complex powder. The carvacrol, cyclodextrin metal-organic framework, and Fe... 3+ The dosage ratio is the same as above.

[0048] Then, an antibacterial film was prepared using a solvent casting method, incorporating CAR-Fe 3+ @CD-MOF inclusion complexes are dispersed in a biodegradable polymer, preferably prior to dispersion, CAR-Fe 3+ The CD-MOF inclusion complex is soluble in anhydrous ethanol. This invention does not have a specific limitation on the amount of anhydrous ethanol used; however, it employs an amount capable of dissolving CAR-Fe. 3+The amount of the @CD-MOF inclusion complex is sufficient. After dissolving, it is added to the biodegradable polymer, preferably in a liquid state. After addition, stirring is preferred. Stirring is preferably performed at 400 rpm magnetically for 30 minutes at room temperature to obtain the antibacterial film solution. Then, the antibacterial film solution is defoamed. This invention does not have a specific limitation on the defoaming method; conventional defoaming methods in the art are acceptable. In some embodiments, ultrasonic defoaming can be selected. Defoaming is preferably performed for 30 minutes. Then, casting is performed, pouring the antibacterial film solution onto a petri dish, and then drying to form a film. The drying temperature is preferably 35~50℃, more preferably 35℃, 40℃, 45℃, or 50℃, and the drying time is preferably 8~24h, more preferably 8h, 12h, 16h, 20h, or 24h. After drying, the film is peeled off to obtain the antibacterial film. The CAR-Fe 3+ The ratio of @CD-MOF inclusion complex to biodegradable polymer is the same as above, with carvacrol and Fe2+ added. 3+ Cyclodextrin metal-organic framework (CAR-Fe) 3+ The mass-volume ratio of the @CD-MOF inclusion complex to the blend of polyvinyl alcohol and chitosan (a biodegradable polymer).

[0049] The present invention relates to the Fe 3+ The source of carvacrol is not particularly limited; any commercially available product in the field is acceptable. The Fe described in this invention... 3+ The compound can be derived from ferric chloride hexahydrate (FeCl3·6H2O, CAS No.: 10025-77-1, molecular weight: 270.30).

[0050] The preferred method for preparing the cyclodextrin metal-organic framework is the methanol vapor diffusion method. This invention does not specifically limit the specific steps of the methanol vapor diffusion method; conventional steps in the art can be used. In some embodiments, γ-cyclodextrin and potassium hydroxide can be dissolved in deionized water at a molar ratio of 1:(6~10) (e.g., 1:6, 1:8, or 1:10) to achieve a final concentration of γ-cyclodextrin of 1.5~3.5 mmol / 100 mL (e.g., 1.5 mmol / 100 mL, 2.5 mmol / 100 mL, or 3.5 mmol / 100 mL). The mixed solution is ultrasonically treated, filtered through a 0.45 μm membrane (e.g., a polytetrafluoroethylene membrane), and the filtrate is mixed with methanol at a volume ratio of 5:3. The mixture is heated in a 60°C constant-temperature water bath until the turbid liquid becomes clear. The surfactant cetyltrimethylammonium bromide (CTAB) is added to achieve a final concentration of 8 mg / mL. The mixture is crystallized overnight at room temperature. The resulting precipitate is washed three times each with isopropanol, methanol, and ethanol. The precipitate is collected by centrifugation and dried to obtain nano-sized CD-MOFs. After obtaining CD-MOF, in order to remove the residual high-boiling-point solvent and moisture in the CD-MOF crystal channels, it is preferable to soak the crystals in dichloromethane solution, place them on a shaker and shake for three days, changing the solution every 24 hours. Collect the crystals by centrifugation, dry them in a vacuum oven at 60°C for 4 hours, and grind them.

[0051] The blend of polyvinyl alcohol (PVA) and chitosan is preferably obtained by dissolving PVA and chitosan separately and then mixing them. PVA is preferably dissolved in deionized water, and chitosan is preferably dissolved in 2% v / v glacial acetic acid. This invention does not specifically limit the dissolution and mixing steps; conventional dissolution and mixing steps in the art are acceptable. The concentrations and mixing ratios of the PVA and chitosan solutions obtained after dissolving PVA and chitosan are the same as above.

[0052] In this invention, the room temperature is preferably any temperature between 25 and 35°C. Since the room temperature is not constant, it is acceptable as long as it is within the above temperature range.

[0053] The present invention also provides the application of the antibacterial film or the preparation method in the preparation of food preservation products.

[0054] This invention utilizes the humidity-responsive characteristics of cyclodextrin metal-organic framework pores and Fe 3+ The photoresponsive properties of the carvacrol complex enable the release of antibacterial substances at high humidity and their inhibition at low humidity. At the same time, the antibacterial effect is enhanced under light, realizing intelligent regulation of the release and antibacterial effect of antibacterial substances. This allows for controllable, efficient, and precise antibacterial action on food, especially fresh food, under complex storage conditions.

[0055] This invention also provides the application of the antibacterial film or the antibacterial film prepared by the preparation method in combination with light irradiation in food preservation. The light source is 405nm blue light or 400-500nm visible light, preferably with a wavelength of 400nm, 450nm, or 500nm; the light intensity is 5-50W, preferably 5W, 10W, 20W, 30W, 40W, or 50W; the irradiation time is 0.5-2h, preferably 0.5h, 1h, 1.5h, or 2h; the ambient temperature for the light irradiation operation is 0-8℃, preferably 0℃, 2℃, 4℃, 6℃, or 8℃. The light irradiation excites Fe in the antibacterial film. 3+ The photodynamic effect of carvacrol complexes can achieve controllable, efficient, and synergistic inhibition of foodborne pathogens.

[0056] In this invention, the food preferably includes fresh food and / or ready-to-eat products; the fresh food preferably includes livestock and poultry meat and / or seafood, the livestock and poultry meat preferably includes pork, beef, mutton and / or chicken, the seafood preferably includes fish (such as salmon), shrimp and / or crab; the food preferably also includes food stored and transported under cold chain.

[0057] The preferred cold chain low-temperature and variable-temperature storage conditions for the antibacterial film application of this invention include: a storage temperature of -2℃ to 10℃ and a relative humidity of 40% to 98%. These storage conditions also include temperature and humidity fluctuations caused by cold chain opening, defrosting cycles, or the seepage of tissue fluids from fresh food. More preferably, the storage temperature is refrigerated (0-8℃) and / or ice-temperature storage (-2℃ to 0℃).

[0058] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0059] Unless otherwise specified, the following embodiments are all conventional methods.

[0060] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0061] Example 1 An edible packaging antibacterial film (CAR-Fe) with a light / humidity synergistic response suitable for cold chain storage and transportation. 3+ The CD-MOF / PVA-CS antibacterial membrane was prepared using the following steps: (1) Preparation of cyclodextrin metal-organic frameworks (CD-MOF): γ-cyclodextrin (3.2428 g, 2.5 mmol) and potassium hydroxide (1.1222 g, 20 mmol) were dissolved in deionized water (100 mL) at a molar ratio of 1:8. The mixed solution was sonicated for 30 min until homogeneous. The solution was filtered through a polytetrafluoroethylene membrane (0.45 μm) into a clean beaker (200 mL) to remove larger MOFs. The filtered solution was mixed with methanol (60 mL) and heated in a constant temperature water bath at 60 °C for 1 h until the turbid liquid became clear. The surfactant CTAB (8 mg / mL) was added to the clear solution, and crystallization was carried out overnight at room temperature. The resulting precipitate was washed three times each with isopropanol (to remove excess CTAB crystals), methanol, and ethanol. The precipitate was collected by centrifugation (8000 rpm, 10 min, 20 °C) and dried to obtain nano-sized CD-MOFs. To remove residual high-boiling-point solvents and moisture from the pores of CD-MOF crystals, the crystals were soaked in dichloromethane liquid (analytical grade, ≥99.5%) and shaken on a shaker for three days, with the solution changed every 24 hours. The crystals were collected by centrifugation (8000 rpm, 10 min, 20℃) and dried in a vacuum oven at 60℃ for 4 hours. The dried sample was then ground for later use.

[0062] (2) CAR-Fe 3+ Preparation of @CD-MOF inclusion complex (CFC): Carvacrol, CD-MOF, Fe 3+ (Ferric chloride hexahydrate was provided) Anhydrous ethanol was added at a mass ratio of 1:1:3 and a total solids mass to anhydrous ethanol volume ratio of 1:10. The mixture was sonicated for 30 min to ensure complete dissolution. After shaking at 50°C and 200 rpm for 24 h, the mixture was centrifuged (8000 rpm, 5 min, 20°C). The supernatant was removed, and the mixture was washed three times with anhydrous ethanol to remove unbound carvacrol. The resulting solid was collected and vacuum dried at 40°C for 4 h to obtain CAR-Fe. 3+ @CD-MOF inclusion compound powder.

[0063] (3) Preparation of PVA-CS (PS) biodegradable polymer: Weigh polyvinyl alcohol (PVA) powder and add it to deionized water, then stir and disperse at room temperature. Heat to 95℃ and magnetically stir at 300 rpm for 1.5 h until completely dissolved. After the solution becomes clear and transparent, cool to room temperature to obtain a 5% w / v polyvinyl alcohol solution. Weigh chitosan powder and slowly add it to 2% v / v glacial acetic acid, stirring at room temperature and 300 rpm for 2 h until completely dissolved to obtain a 3% w / v chitosan solution. Mix the two solutions at a volume ratio of 7:3 and stir at room temperature and 300 rpm for 30 min until completely dissolved to obtain the biodegradable polymer (film-forming solution).

[0064] (4) CAR-Fe 3+Preparation of @CD-MOF / PVA-CS antibacterial film (CFC / PS for short): The CAR-Fe obtained in step (2) 3+ @CD-MOF inclusion complex was dissolved in anhydrous ethanol and then added to the film-forming solution in step (3) at a mass-volume fraction of 0.75% (mass of inclusion complex (g) / volume of film-forming solution (100 mL)). CAR-Fe was obtained by magnetic stirring at 400 rpm for 30 min at room temperature. 3+ @CD-MOF / PVA-CS antibacterial film solution. After ultrasonic defoaming of the above antibacterial film solution for 30 minutes, it is poured into a petri dish and dried in a 45℃ forced-air oven for 12 hours. After removing the film, the composite film (antibacterial film) can be obtained.

[0065] Example 2 The only difference from Example 1 is that the mass volume fraction of step (4) is replaced with 1.5% instead of 0.75%. All other aspects are the same as in Example 1.

[0066] Example 3 The only difference from Example 1 is that the mass volume fraction of step (4) is replaced with 3% instead of 0.75%. All other aspects are the same as in Example 1.

[0067] Example 4 An edible packaging antibacterial film with a light / humidity synergistic response suitable for cold chain storage and transportation is prepared by the following steps: (1) The only difference from the steps in Example 1 is that the amount of γ-cyclodextrin is replaced with 1.5 mmol and the amount of potassium hydroxide is replaced with 9 mmol. The rest is the same as the steps in Example 1 (1).

[0068] (2) CAR-Fe 3+ Preparation of CD-MOF inclusion complex: Carvacrol, CD-MOF, Fe... 3+ (Ferric chloride hexahydrate was provided) Anhydrous ethanol was added at a mass ratio of 1:0.5:1 and a total solids to anhydrous ethanol volume ratio of 1:8. The mixture was sonicated for 30 min to ensure complete dissolution. After shaking at 45°C and 150 rpm for 20 h, the mixture was centrifuged (8000 rpm, 5 min, 20°C). The supernatant was removed, and the mixture was washed three times with anhydrous ethanol to remove unbound carvacrol. The resulting solid was collected and vacuum dried at 35°C for 3.5 h to obtain CAR-Fe. 3+ @CD-MOF inclusion compound powder.

[0069] (3) The only difference from step (3) of Example 1 is that the concentrations of polyvinyl alcohol solution and chitosan solution are replaced with 4% w / v and 2% w / v respectively, and the two solutions are mixed at a volume ratio of 5:5. The rest is the same as step (3) of Example 1.

[0070] (4) CAR-Fe3+ Preparation of CD-MOF / PVA-CS antibacterial film: The CAR-Fe obtained in step (2) 3+ @CD-MOF inclusion complex was dissolved in anhydrous ethanol and added to the film-forming solution in step (3) at a mass-volume fraction of 0.5%. The mixture was then magnetically stirred at 400 rpm for 30 min at room temperature to obtain CAR-Fe. 3+ @CD-MOF / PVA-CS antibacterial film solution. After ultrasonic defoaming of the above antibacterial film solution for 30 minutes, it is poured into a petri dish and dried in a 35°C forced-air oven for 8 hours. After removing the film, the composite film (antibacterial film) can be obtained.

[0071] Example 5 An edible packaging antibacterial film with a light / humidity synergistic response suitable for cold chain storage and transportation is prepared by the following steps: (1) The only difference from the steps in Example 1 is that the amount of γ-cyclodextrin is replaced with 3.5 mmol and the amount of potassium hydroxide is replaced with 35 mmol. The rest is the same as the steps in Example 1 (1).

[0072] (2) CAR-Fe 3+ Preparation of CD-MOF inclusion complex: Carvacrol, CD-MOF, Fe... 3+ (Ferric chloride hexahydrate was provided) Anhydrous ethanol was added at a mass ratio of 1:2:5 and a total solids to anhydrous ethanol volume ratio of 1:12. The mixture was sonicated for 30 min to ensure complete dissolution. After shaking at 55°C and 250 rpm for 28 h, the mixture was centrifuged (8000 rpm, 5 min, 20°C). The supernatant was removed, and the mixture was washed three times with anhydrous ethanol to remove unbound carvacrol. The resulting solid was collected and vacuum dried at 45°C for 4.5 h to obtain CAR-Fe. 3+ @CD-MOF inclusion compound powder.

[0073] (3) The only difference from step (3) of Example 1 is that the concentrations of polyvinyl alcohol solution and chitosan solution are replaced with 6% w / v and 4% w / v respectively, and the two solutions are mixed at a volume ratio of 9:1. The rest is the same as step (3) of Example 1.

[0074] (4) CAR-Fe 3+ Preparation of CD-MOF / PVA-CS antibacterial film: The CAR-Fe obtained in step (2) 3+ @CD-MOF inclusion complex was dissolved in anhydrous ethanol and added to the film-forming solution in step (3) at a mass-volume fraction of 5%. The mixture was magnetically stirred at 400 rpm for 30 min at room temperature to obtain CAR-Fe. 3+@CD-MOF / PVA-CS antibacterial film solution. After ultrasonic defoaming of the above antibacterial film solution for 30 minutes, it is poured into a petri dish and dried in a 50℃ forced-air oven for 24 hours. After removing the film, the composite film (antibacterial film) can be obtained.

[0075] Comparative Example 1 The only difference from Example 1 is that the mass fraction of step (4) is replaced with 0% instead of 0%. All other aspects are the same as in Example 1.

[0076] Experimental Example 1 Antibacterial effects of carvacrol alone and in combination with photodynamic therapy on different bacteria The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of carvacrol against eight bacteria (Escherichia coli, Staphylococcus aureus, Serratia marcescens, Pantotheca acuminata, Klebsiella pneumoniae, Pseudomonas chicorifolia, Pseudomonas putida, and Pseudomonas aeruginosa) were determined using the broth dilution method. The photodynamic treatment group was irradiated with a 405nm LED blue light (20W) for 1 hour after the addition of carvacrol, while the carvacrol-only treatment group was placed in the dark for 1 hour after the addition of carvacrol, followed by incubation at 37℃ for 24 hours. The results are shown in Table 1.

[0077] Table 1. MIC and MBC of carvacrol against eight bacteria after treatment alone and in combination with photodynamic therapy.

[0078] Table 1 shows that carvacrol alone exhibited concentration-dependent antibacterial activity against all eight bacteria, with *Escherichia coli* being the most sensitive (MIC = 0.5 mg / mL), while *Pseudomonas putida* and *Pseudomonas aeruginosa* showed the strongest tolerance (MIC = 4 mg / mL). The sensitivity ranking of the eight bacteria was: *Escherichia coli* > *Staphylococcus aureus* / *Pantotheca cum Caulis* > *Serratia marcescens* / *Klebsiella pneumoniae* / *Pseudomonas chicory* > *Pseudomonas putida* / *Pseudomonas aeruginosa*. Under 405 nm blue light irradiation, the photodynamic antibacterial activity of carvacrol was enhanced to varying degrees. The MIC or MBC of *Staphylococcus aureus*, *Serratia marcescens*, *Pantotheca cum Caulis*, and *Klebsiella pneumoniae* decreased by 50%, significantly improving the antibacterial effect. However, the MIC and MBC of the three Pseudomonas species (*Pseudomonas chicory*, *Pseudomonas putida*, and *Pseudomonas aeruginosa*) did not change after photodynamic treatment, showing significant tolerance.

[0079] Experimental Example 2 Fe 3+ Inhibitory effects of single treatment versus combined photodynamic treatment on three Pseudomonas species The bacterial suspensions of *Pseudomonas chicorifolia*, *Pseudomonas putida*, and *Pseudomonas aeruginosa* were adjusted to a McFarland turbidity of 0.5. Different concentrations of Fe were then added.3+ Solutions (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 4, 6, 8 mg / mL), Light group with added Fe 3+ After the solution was dissolved, it was irradiated with a 405nm LED blue light lamp (20W) for 1 hour. The dark group was treated with Fe. 3+ After the solution was dissolved and placed in the dark for 1 hour, it was then incubated at 37°C for 24 hours to observe the results. The inhibitory effect was as follows: Figure 2 As shown. At low concentrations of Fe... 3+ Within the range of 0.25–1.0 mg / mL, the inhibition rates of all three strains showed no significant change compared to the control group, indicating that low concentrations of Fe... 3+ It does not possess actual antibacterial ability. When Fe 3+ The inhibitory effect against *Pseudomonas chicory* only becomes significant when the concentration is increased to 2 mg / mL or higher. 3+ The inhibitory effect against *Pseudomonas aeruginosa* only became apparent at concentrations of 4 mg / mL and above, and continued to increase with increasing concentration. At 8 mg / mL, the strongest inhibitory effect was observed against all three *Pseudomonas* species (due to the higher concentration). Figure 2 (The results for the most resistant Pseudomonas aeruginosa are used as an example only). The above results indicate that Fe... 3+ Although it possesses some antibacterial activity, it exhibits a significant high-concentration dependence, with limited antibacterial value at low concentrations. Therefore, in practical applications, Fe... 3+ It is not suitable for use alone as an antibacterial agent, but is more suitable for compounding with other antibacterial substances or as an auxiliary synergistic ingredient.

[0080] Experimental Example 3 carvacrol and Fe 3+ The inhibitory effect of the compound formulation combined with photodynamic treatment on three types of Pseudomonas bacteria. Carvacrol (2 mg / mL) was mixed with different concentrations of Fe 3+ A mixture of (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 4, 6, 8 mg / mL) was added to suspensions of three Pseudomonas species. The light group was irradiated with a 405nm LED blue light (20W) for 1 hour (at a distance of 30cm), while the dark group was kept in the dark for 1 hour. Afterwards, the mixtures were incubated at 37℃ for 24 hours, and the inhibition rates of each treatment group were measured. The results are as follows: Figures 3-5 As shown.

[0081] The results showed that: (1) it had an effect on *Pseudomonas chicorifolia* ( Figure 3 (2 mg / mL carvacrol alone showed antibacterial rates of 11.46% and 17.17% under dark and light conditions, respectively. Adding Fe...) 3+The inhibition rate was significantly improved after treatment. Under 2CAR+1.25Fe light conditions, the inhibition rate reached 93.22%, and under 2CAR+2Fe light conditions, it reached 99.99%, achieving near-complete eradication. (2) For Pseudomonas putida ( Figure 4 The antibacterial rates of 2 mg / mL carvacrol alone were 13.86% and 25.77% under dark and light conditions, respectively. Adding 0.5 mg / mL Fe... 3+ Afterwards, the antibacterial rate reached 98.10% under light conditions; with the addition of 1 mg / mL Fe... 3+ The kill rate reached 99.99%, achieving complete eradication. (3) For Pseudomonas aeruginosa ( Figure 5 The antibacterial rates of 2 mg / mL carvacrol alone were 13.21% and 26.02% under dark and light conditions, respectively. Adding 2 mg / mL Fe... 3+ Afterwards, the antibacterial rate increased to 82.97% under light conditions, a net increase of 56.95 percentage points; with the addition of 8 mg / mL Fe 3+ The kill rate reached 99.99%, achieving complete eradication. Three types of Pseudomonas bacteria showed resistance to carvacrol-Fe... 3+ The sensitivity ranking of the system is as follows: *Pseudomonas putida* (0.5 mg / mL Fe...). 3+ > *Pseudomonas chicorifolia* (1.25-1.5 mg / mL Fe) 3+ Pseudomonas aeruginosa (4-6 mg / mL Fe) 3+ The above results indicate that Fe 3+ It does not possess significant antibacterial activity on its own; its main function lies in synergistically enhancing photodynamic antibacterial properties through coordination with carvacrol. (Fe) 3+ Coordination modification can significantly enhance the photodynamic antibacterial effect of carvacrol against Pseudomonas aeruginosa, with the optimal ratio being carvacrol:Fe 3+ =1∶3-1∶4.

[0082] Test Example 4 The CAR-Fe prepared in Examples 1-3 and Comparative Example 1 3+ Characterization of the CD-MOF / PVA-CS antibacterial film The results show that the present invention successfully constructed CAR-Fe 3+ The CD-MOF composite system was uniformly dispersed in a PVA-CS matrix. SEM ( Figures 6-7 ) Confirmed CAR-Fe 3+ Successfully loaded onto CD-MOF and uniformly distributed; FTIR ( Figure 8 ) and XRD ( Figure 9 This indicates that Fe 3+ The complex coordinates with the phenolic hydroxyl groups of CAR and binds to CD-MOF via hydrogen bonds, maintaining the original nanostructure of CFCs in the antibacterial film; TGA ( Figure 10The results showed a significant improvement in the thermal stability of CFCs, and transmittance analysis ( Figure 11 This indicates that the CFC / PS membrane possesses excellent UV blocking properties. Together, they demonstrate the superior UV blocking performance of CAR-Fe... 3+ The successful preparation of @CD-MOF / PVA-CS antibacterial membrane and its structural basis in photodynamic antibacterial and intelligent controlled release.

[0083] Experimental Example 5 CAR-Fe prepared in Examples 1-3 and Comparative Example 1 3+ Mechanical properties of @CD-MOF / PVA-CS antibacterial film The thickness of the antibacterial films prepared in Examples 1 (0.75% CFC / PS), 2 (1.5% CFC / PS), 3 (3% CFC / PS), and Comparative Example 1 (0% CFC / PS) was determined using a digital micrometer (accuracy 0.001 mm). The films were cut into 30 mm × 30 mm square samples, and the thickness was measured at five randomly selected points at the four corners and the center, with the average value taken. Each sample was measured in triplicate. The antibacterial films were then cut into 50 mm × 20 mm rectangular strips and subjected to tensile testing using a physical property analyzer. The initial clamp spacing was set to 20 mm, the termination distance to 90 mm, the trigger force to 5 g, and the test rate to 0.5 mm / s. Each sample was measured in triplicate, and the tensile strength and elongation at break were calculated.

[0084] Table 2. Thickness, tensile strength, and elongation at break of packaging films with different contents.

[0085] Note: Different lowercase letters indicate significant differences between different groups under the same indicator, P < 0.05.

[0086] As shown in Table 2, the thickness of the antibacterial film increased significantly after adding CFC compared to the pure PVA-CS film, and the thickness increased progressively with increasing CFC content, indicating that the introduction of CFC increased the solid content of the film. Regarding mechanical properties, the tensile strength at a low addition level (0.75%) was comparable to that of the pure film, maintaining good mechanical properties. However, as the addition level increased further to 3%, the tensile strength decreased significantly, possibly due to the aggregation of CFC particles in the matrix at high concentrations, leading to stress concentration. The elongation at break reached its maximum at an addition level of 1.5%, indicating that an appropriate amount of CFC can enhance the flexibility of the film, while excessively high or low addition levels are detrimental to improving flexibility.

[0087] Experimental Example 6 CAR-Fe prepared in Examples 1-3 and Comparative Example 1 3+ Barrier properties of @CD-MOF / PVA-CS antibacterial film The water contact angle of each antibacterial film was measured using an optical contact angle meter. The water contact angle of the antibacterial film at 0, 10, 30, and 60 s was measured using the seated drop method, with each sample measured five times. The water vapor transmission rate of the film was determined using the cup weight gain method, continuously measured for 7 days at 38±0.6℃ and 90±2% relative humidity. The water vapor transmission rate (WVP) was calculated according to formula (1), with each group of samples measured three times in parallel. The water contact angle test results are as follows: Figure 12 As shown, the initial water contact angle of the pure PVA-CS membrane was 98.34°, exhibiting hydrophobic properties. With the addition of CFCs, the contact angle gradually decreased, dropping to 73.58° at a 3% addition level, indicating enhanced hydrophilicity. Meanwhile, the WVP test results are as follows... Figure 13 As shown, WVP increases from 11.2 × 10⁻⁶ with increasing CFC addition. -4 Reduced to 5.8×10 -4 g·mm / m 2 • h·kPa, improved moisture barrier performance. The introduction of CFC enhances the hydrophilicity of the antibacterial film (which is beneficial for the release of antibacterial agents) and improves the water vapor barrier (which is beneficial for reducing moisture loss from food), thus achieving synergistic optimization of the antibacterial substance release performance and the preservation function.

[0088] Formula (1) Experimental Example 7 CAR-Fe prepared in Example 3 3+ The sustained-release properties of @CD-MOF / PVA-CS antibacterial film 3% CAR-Fe 3+ The CD-MOF / PVA-CS antibacterial membrane was dissolved in 5 mL of ethanol, sonicated for 30 min, and centrifuged at 10000 rpm for 10 min. The absorbance of CAR was measured at 275 nm using a UV-Vis spectrophotometer, and the content was calculated. The release kinetics of CAR from the antibacterial membrane were tested by adjusting the relative humidity with three saturated salt solutions: potassium bicarbonate (K₂CO₃, 43.0±0.3%), sodium chloride (NaCl, 75.0±0.3%), and potassium sulfate (K₂SO₄, 98.0±1.0%). The results are as follows. Figure 14 As shown, at a humidity of 43%, only about 20% of carvacrol was released on day 7. At a humidity of 75%, about 60% of carvacrol was released on day 7. At a humidity of 98%, carvacrol was almost completely released on day 7. Therefore, the release results indicate that the release of carvacrol from the antibacterial film can be triggered by high humidity, and the antibacterial film can be stored at low humidity.

[0089] This antibacterial film exhibits a humidity-responsive characteristic of "slow release in low humidity and rapid release in high humidity," enabling the on-demand release of carvacrol. In other words, it remains stable in dry environments, reducing ineffective losses, while accelerating release in high-humidity environments (such as food tissue fluid seepage or condensation during refrigeration), effectively addressing the risk of microbial proliferation.

[0090] Experimental Example 8 CAR-Fe prepared in Examples 1-3 and Comparative Example 1 3+ Antibacterial properties of @CD-MOF / PVA-CS antibacterial film Gram-negative *Escherichia coli* (E. coli) and Gram-positive *Staphylococcus aureus* (S. aureus) were selected as model bacteria. The antibacterial activity of different contents of antibacterial films before and after blue light irradiation was evaluated based on the filter paper disc method. The bacterial culture concentration was adjusted to 0.5 McFarland turbidity, and 100 μL was spread until the culture medium was completely absorbed by LB solid medium. 6 mm diameter circular filter paper discs were immersed in PVA-CS antibacterial film solutions with different loadings (0% (Comparative Example 1), 0.75% (Example 1), 1.5% (Example 2), 3% (Example 3)). The light group was irradiated with a 405 nm LED blue light lamp (20 W) for 1 h (distance 30 cm), and the dark group was placed in the dark for 1 h. After that, the culture dishes were placed at 37 °C for 24 h, and the results were observed.

[0091] The results are as follows Figure 15 As shown, with CAR-Fe 3+ As the @CD-MOF loading increased from 0.75% to 3%, the inhibition zone area significantly increased. After 1 hour of irradiation with 405nm blue light, the inhibition zone area of ​​each loading of the antibacterial film was significantly larger than that of the corresponding dark control group. Among them, the 3% loading antibacterial film showed the best antibacterial effect against Escherichia coli and Staphylococcus aureus under light conditions, confirming that blue light excitation can effectively enhance the photodynamic antibacterial activity of the antibacterial film. This antibacterial film showed good inhibitory effects against both Gram-negative and Gram-positive bacteria, exhibiting broad-spectrum antibacterial properties.

[0092] Experimental Example 9 CAR-Fe prepared in Example 3 3+ The effect of @CD-MOF / PVA-CS antibacterial film on low-temperature preservation of pork and salmon.

[0093] Sample Preparation: Pork - Fresh pork tenderloin was purchased from a local supermarket in Beijing. The cutting board was cleaned and disinfected with 75% ethanol. Fat and fascia were removed from the surface of the pork using a sterile scalpel. The pork was cut into small pieces of 4×4×2cm, each weighing approximately 10g, and placed in a food storage container. Salmon - Salmon was purchased from a local supermarket in Beijing and aseptically cut to ensure each sample was 1.0-1.5cm thick, with each piece weighing approximately 10g, and placed in a food storage container. The pre-treated samples were placed in sterile petri dishes with a diameter of 6cm, with one piece of raw meat in each dish. Three replicates were set up for each condition. Commercially available PE film (positive control, polyethylene cling film) and CAR-Fe were used for the petri dishes, respectively. 3+ @CD-MOF / PVA-CS antibacterial film (dark group, CFC / PS+Dark) and CAR-Fe 3+ After covering the culture dish with a CD-MOF / PVA-CS antibacterial film (light group, CFC / PS+Light), the dish was covered. The blank control group was left untreated. For pork (0-8 days) and salmon (0-6 days), before daily storage, the light group was irradiated for 1 hour at 4℃ using a 405nm LED lamp (20W power, 30cm distance). The dark group, positive control group, and blank control group were all placed in darkness. The four groups of samples were stored in a 4℃ refrigerator for 8 days (pork) or 6 days (salmon). Samples were taken out on days 0, 2, 4, 6, and 8 for various tests.

[0094] Changes in the appearance of pork ( Figure 16 Fresh pork samples were bright red in color, elastic in texture, and had a normal odor. On day 6 of storage, the pork in the blank control group and the positive control group packaged in PE film gradually lost its luster, turned yellowish-green, produced a viscous exudate, and developed a putrid odor; these phenomena gradually worsened with storage time. In contrast, the light and dark groups maintained good surface morphology throughout the 8-day storage period, and no obvious bacterial colonies or exudate appeared during the entire shelf life, indicating that the antibacterial film of this invention has a good pork preservation effect.

[0095] Changes in the appearance of salmon ( Figure 17Fresh salmon samples exhibited an orange-red color, clear texture, firm and elastic flesh, and a fresh aroma. On the 4th day of storage, the salmon in the blank control group and the positive control group packaged in PE film gradually lost their color, showing a grayish-brown discoloration, softened flesh, developed mucus, and had a noticeable fishy odor. With prolonged storage, the spoilage worsened. In contrast, the light and dark groups maintained a good appearance throughout the 6-day storage period, with bright color, firm flesh, a dry surface without mucus, and no obvious odor. No obvious signs of spoilage were observed throughout the entire shelf life, indicating that the antibacterial film of this invention has a good salmon preservation effect.

[0096] Experimental Example 10 CAR-Fe prepared in Example 3 3+ The preservation effect of @CD-MOF / PVA-CS antibacterial film on pork under cold chain temperature fluctuation conditions.

[0097] Experimental treatment: Fresh pork samples were randomly divided into three groups for storage experiments under different conditions. PE group (Polyethylene cling film-4): Samples were wrapped in commercially available polyethylene cling film and stored continuously at a constant temperature of 4℃ for 8 days (0-8d); CFC / PS-4 group: Samples were stored using CAR-Fe... 3+ After being wrapped with CD-MOF / PVA-CS antibacterial film, the samples were stored continuously at a constant temperature of 4℃ for 8 days (0-8d); CFC / PS-4-10 group: the samples were treated with CAR-Fe 3+ After being wrapped with @CD-MOF / PVA-CS antibacterial film, the samples were stored at a constant temperature of 4℃ until day 2. The ambient temperature was then abruptly increased from 4℃ to 10℃ and left at this temperature for 5 hours (simulating temperature fluctuations / chain breakage during cold chain transportation or sales). Afterward, the samples were quickly returned to 4℃ and stored until day 8. All samples were taken on days 0, 2, 4, 6, and 8 during storage, and the following quality indicators were measured: appearance (photographed), color difference value (L...). a b The study measured the following parameters: weight loss, pH value, total bacterial count, and volatile basic nitrogen content. Three replicates were performed for each group at each time point, and results are expressed as mean ± standard deviation. The changes in various quality indicators of the PE group (normal packaging control), CFC / PS-4 group (temperature-controlled antibacterial film packaging), and CFC / PS-4-10 group (temperature-controlled antibacterial film packaging) were compared to evaluate CAR-Fe. 3+ The preservation effect of @CD-MOF / PVA-CS antibacterial film on pork under cold chain temperature fluctuation conditions and the stability of light / humidity synergistic antibacterial performance.

[0098] Changes in various indicators of pork, such as Figure 18 and Figure 19 As shown, variable temperature treatment significantly accelerated the deterioration process of pork quality. Regarding color difference, temperature fluctuations led to L... The value first increases and then decreases, a The value is decreasing rapidly, b The pH value rose rapidly, and the color deteriorated significantly. The weight loss rate was higher than that of the constant temperature group at all time points, indicating that temperature fluctuations exacerbated moisture evaporation and juice seepage. The decrease and increase of pH value were more dramatic, and the turning point was significantly earlier. The total bacterial count increased significantly faster than that of the constant temperature antibacterial film group, indicating that temperature fluctuations provided a growth window for microorganisms. The accumulation rate of volatile basic nitrogen was accelerated, and protein decomposition was more severe. Overall, temperature fluctuations reduced the preservation performance of the CFC / PS antibacterial film compared to the constant temperature condition, but all indicators were still better than those of the PE packaging group, proving that the antibacterial film has a certain resistance to temperature fluctuations and can partially alleviate the negative impact of cold chain disruptions on pork quality.

[0099] Experimental Example 11 CAR-Fe prepared under temperature fluctuation conditions in Example 3 3+ Microbial community analysis of pork packaged with @CD-MOF / PVA-CS antibacterial film.

[0100] Fresh pork samples were randomly divided into three groups for storage experiments under different conditions. Group AP: Samples were wrapped in commercially available polyethylene plastic wrap and stored at a constant temperature of 4℃ for 6 consecutive days. Group AC: Samples were wrapped in CFC / PS antibacterial film and stored at a constant temperature of 4℃ for 6 consecutive days. Group BC: Samples were wrapped in CFC / PS antibacterial film and stored at a constant temperature of 4℃ until day 2, then the ambient temperature was abruptly increased from 4℃ to 10℃ and left at this temperature for 5 hours, before being quickly returned to 4℃ and stored until day 6. Fresh pork samples from day 0 served as the control group (Group A0). Six biological replicates were set up for each group. Total DNA was extracted from the surface tissue of each sample, and PCR amplification was performed using 16S rRNA gene V3-V4 region-specific primers (338F and 806R). The amplified products were then used for library construction and high-throughput sequencing on the Illumina NovaSeq platform. After quality control, noise reduction, and chimera removal using QIIME2 software, sequencing data were clustered according to 100% similarity to obtain ASV characteristic sequences, and species annotation was performed using the SILVA database. Differences in microbial community structure among the samples were compared through species composition analysis.

[0101] The results are as follows Figure 20As shown in the figure, at the phylum level, in group A0, Actinobacteria (21.6%-36.1%), Firmicutes (11.9%-16.8%), Proteobacteria (6.1%-13.0%), and Bacteroidetes (8.5%-26.5%) all accounted for a relatively high proportion. After 6 days of storage, the proportions of Actinobacteria and Bacteroidetes dropped sharply to below 0.1%, while Proteobacteria became the absolutely dominant phylum, reaching 74.8%-95.2% in group AP, 74.0%-89.3% in group AC, and 50.3%-71.9% in group BC; Firmicutes remained at a relatively high level, reaching 20.5%-49.5% in group BC. At the genus level, group A0 exhibited rich microbial diversity, with Bifidobacterium, Escherichia coli, and Collins bacteria all showing high abundance. After 6 days of storage, *Pseudomonas* became the dominant genus, exhibiting the highest abundance in groups AP, AC, and BC. *Aeromonas thermophila* abundance significantly increased, becoming the second most dominant genus. In group BC (temperature fluctuation group), the abundance of Proteobacteria (50.3%-71.9%) was significantly lower than that in group AC (74.0%-89.3%), while the abundance of Firmicutes increased accordingly. The abundance of *Aeromonas thermophila* was significantly higher than that in groups AC and AP, while the abundance of *Pseudomonas* was lower than that in group AC. These results indicate that the CFC / PS antibacterial film of this invention can achieve intelligent controlled release through a humidity-responsive mechanism under temperature fluctuation conditions, effectively inhibiting the proliferation of putrefactive bacteria such as *Pseudomonas*.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An edible antibacterial packaging film suitable for cold chain storage and transportation, characterized in that, It includes a continuous phase matrix and a cyclodextrin metal-organic framework dispersed therein; The continuous phase matrix is ​​a biodegradable polymer, and the cyclodextrin metal-organic framework is loaded with carvacrol and Fe. 3+ .

2. The antibacterial film according to claim 1, characterized in that, The carvacrol and Fe 3+ The mass ratio is 1:(1~5), and the mass ratio of carvacrol to cyclodextrin metal-organic framework is 1:(0.5~2).

3. The antibacterial film according to claim 1, characterized in that, The biodegradable polymer comprises a blend of polyvinyl alcohol and chitosan, and the cyclodextrin metal-organic framework is composed of γ-cyclodextrin and K+. + Formed through self-assembly.

4. The antibacterial film according to claim 3, characterized in that, Loaded with carvacrol and Fe 3+ The mass-to-volume ratio of the cyclodextrin metal-organic framework blend with polyvinyl alcohol and chitosan is (0.5~5) g:100mL; the blend of polyvinyl alcohol and chitosan is obtained by mixing polyvinyl alcohol solution and chitosan solution at a volume ratio of (5:5)~(9:1); the concentration of the polyvinyl alcohol solution is 4~6g / 100mL, and the concentration of the chitosan solution is 2~4g / 100mL.

5. The method for preparing the antibacterial film according to any one of claims 1 to 4, characterized in that, Includes the following steps: Carvacrol, cyclodextrin metal-organic framework and Fe 3+ The mixture was blended in anhydrous ethanol, the reaction was shaken, the precipitate was collected and dried to obtain CAR-Fe. 3+ @CD-MOF inclusion compound; CAR-Fe 3+ @CD-MOF inclusion complexes are dispersed in a biodegradable polymer, defoamed, cast, and dried to form a film.

6. The preparation method according to claim 5, characterized in that, The cyclodextrin metal-organic framework is prepared by methanol vapor diffusion.

7. The preparation method according to claim 5, characterized in that, The oscillation reaction is carried out at a temperature of 45-55°C, a rotation speed of 150-250 rpm, and a time of 20-28 h; the drying film formation is carried out at a temperature of 35-50°C and a time of 8-24 h.

8. The application of the antibacterial film according to any one of claims 1 to 4 or the preparation method according to any one of claims 5 to 7 in the preparation of food preservation products.

9. The application of the antibacterial film according to any one of claims 1 to 4 or the antibacterial film prepared by the preparation method according to any one of claims 5 to 7, in combination with light irradiation, in food preservation, characterized in that... The light source is 405nm blue light or 400~500nm visible light, the light intensity is 5~50W, the light duration is 0.5~2h, and the ambient temperature for the light operation is 0~8℃.

10. The application according to claim 8 or 9, characterized in that, The food includes fresh food and / or ready-to-eat products; the fresh food includes livestock and poultry meat and / or seafood; the food also includes food stored and transported under cold chain conditions.

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