Biodegradable antibacterial slow-release fresh-keeping film as well as preparation method and application thereof
By loading cinnamaldehyde onto Ag-MOF nanoparticles and mixing it with carboxymethyl cellulose, Ag-MOF-CIN nanoparticles were prepared, which enhanced the mechanical properties of the film, solved the problem of easy swelling of carboxymethyl cellulose film in high humidity environment, and achieved antibacterial and sustained-release effects.
Patent Information
- Application Number
- CN202511880294.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-13
- Publication Date
- 2026-01-27
AI Technical Summary
In the prior art, carboxymethyl cellulose films are prone to swelling in high humidity environments, and their mechanical properties, such as tensile strength and elongation at break, are insufficient, making it difficult to meet the physical property requirements of composite films.
Cinnamaldehyde was loaded onto Ag-MOF nanoparticles and mixed with carboxymethyl cellulose to form Ag-MOF-CIN nanoparticles, which were then added to the film-forming matrix to prepare a biodegradable antibacterial slow-release preservation film.
It significantly improves the tensile strength and elongation at break of the film, enhances the mechanical properties of the film, and also has antibacterial and sustained-release properties.
Smart Images
Figure CN121405992A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of polymers, in particular to a biodegradable antibacterial slow-release fresh-keeping film and a preparation method and application thereof. BACKGROUND
[0002] Sodium carboxymethyl cellulose (CMC) is a water-soluble cellulose derivative with excellent film-forming property, biocompatibility and biodegradability, which has attracted much attention in the field of degradable packaging materials in recent years. The carboxymethyl group in its molecular structure endows the material with good water solubility and chemical modification potential, and at the same time meets the demand of green packaging materials in the environmental protection policy.
[0003] Metal-organic frameworks (MOFs) are a kind of porous crystalline materials formed by metal ions or clusters and organic ligands through coordination bonds, which have high specific surface area, adjustable pore structure and rich active sites. These characteristics make them an ideal substrate for functional composites. MOFs have several advantages; first, due to their adjustable structure, MOFs can have different morphology, size, composition and chemical properties, which provide them with multifunctionality; second, MOFs have large surface area and high porosity, so they have high loading capacity.
[0004] The prior art CN 118027466 A discloses a torreya grandis essential oil-MOFs modified carboxymethyl cellulose nanofilm, which mixes torreya grandis essential oil with anhydrous methanol, adds acetic acid and DMF, then adds ZrCl4 and BDC-NH2 to the mixture, centrifuges to synthesize MOFs containing torreya grandis essential oil, and then uses a solution casting method to prepare a torreya grandis essential oil-MOFs modified carboxymethyl cellulose nanofilm; it can be seen from further observation of the scheme that the composite film prepared has further improved antibacterial and antioxidant properties, but because the CMC film is easy to crack and has strong hydrophilicity, it is easy to swell in a high humidity environment, and the physical properties of the film have not been well improved.
[0005] Therefore, the technical problem solved by the present application is how to prepare a composite film with better mechanical properties such as tensile strength and elongation at break. SUMMARY
[0006] The purpose of the present application is to provide a preparation method of a biodegradable antibacterial slow-release fresh-keeping film, which loads cinnamaldehyde on Ag-MOFs nanoparticles, and then mixes with the film-forming substrate carboxymethyl cellulose, so that the mechanical properties of the obtained film can be further improved.
[0007] At the same time, the present application also discloses the biodegradable antibacterial slow-release fresh-keeping film prepared by the preparation method and the application thereof.
[0008] To achieve the above-mentioned purpose, the present application provides the following technical scheme:
[0009] The application discloses a preparation method of a biodegradable antibacterial slow-release fresh-keeping film.
[0010] Step 1: AgNO3 and terephthalic acid are mixed, N, N-dimethylformamide is added, and oil bath reaction is carried out in the dark to obtain Ag-MOFs nanoparticles;
[0011] Step 2: Cinnamaldehyde and Ag-MOFs nanoparticles obtained in step 1 are mixed, and an organic volatile solvent is added to react, and Ag-MOFs-CIN nanoparticles are obtained after the organic volatile solvent is completely volatilized;
[0012] Step 3: Carboxymethyl cellulose is dissolved in deionized water to obtain a CMC homogeneous solution, glycerol is added, Ag-MOFs-CIN nanoparticles prepared in step 2 are mixed with the CMC solution, stirring is uniformly carried out to obtain a film-forming liquid, and the film-forming liquid is dried to obtain the biodegradable antibacterial slow-release fresh-keeping film.
[0013] Preferably, the molar ratio of AgNO3 to terephthalic acid in step 1 is 1-5:1-5.
[0014] Preferably, the temperature of the oil bath in step 1 is 100-150 DEG C, the time is 20-28 h, and the atmosphere is a nitrogen atmosphere.
[0015] Preferably, the mass ratio of cinnamaldehyde to Ag-MOFs nanoparticles in step 2 is 2:1.
[0016] Preferably, the organic volatile solvent in step 2 is dichloromethane.
[0017] Preferably, the mass ratio of carboxymethyl cellulose to deionized water in step 3 is 1-3:100-300; the glycerol is added in an amount of 30wt%-60wt% of the carboxymethyl cellulose; and the Ag-MOFs-CIN nanoparticles are added in an amount of 0.5wt%-6wt% of the carboxymethyl cellulose.
[0018] Preferably, the Ag-MOFs-CIN nanoparticles are added in an amount of 0.5wt%-1.5wt% of the carboxymethyl cellulose.
[0019] Preferably, the Ag-MOFs-CIN nanoparticles are added in an amount of 2wt%-6wt% of the carboxymethyl cellulose.
[0020] Preferably, the temperature of the stirring in step 3 is 25 DEG C, the time is 8-14 hours, the temperature of the drying is 25-40 DEG C, the relative humidity is 35-60%, and the time is 8-16 h.
[0021] Preferably, the more specific preparation method is as shown below:
[0022] Step 1: AgNO3 and terephthalic acid are mixed, 80-100 mL of N, N-dimethylformamide is added for light-shielded dispersion for 10-12 h, then oil bath reaction is carried out under a nitrogen atmosphere in the dark, after the reaction is completed, natural cooling to 25 DEG C is carried out, filtration is carried out, the filter residue is washed with ethanol, and finally the filter residue is dried at 60-90 DEG C to obtain Ag-MOFs nanoparticles;
[0023] Step 2: cinnamaldehyde and the Ag-MOFs nanoparticles obtained in step 1 are mixed to obtain a blend, dichloromethane is added to the blend for stirring, after stirring until the dichloromethane is completely volatilized, dichloromethane is continuously added for centrifugal rinsing 1-5 times, after the dichloromethane is completely volatilized, Ag-MOFs-CIN nanoparticles are obtained;
[0024] Step 3: carboxymethyl cellulose is added to deionized water, a CMC homogeneous solution is prepared by stirring at 60-90 DEG C, then glycerol is added to the CMC solution for homogenization; the Ag-MOFs-CIN nanoparticles prepared in step 2 are mixed with the CMC solution, uniform stirring is carried out at 25 DEG C for 8-14 h to obtain a film-forming solution; then the film-forming solution is ultrasonically treated for 20-30 min, and after drying, the biodegradable antibacterial slow-release preservative film is obtained.
[0025] In addition, the application discloses a biodegradable antibacterial slow-release preservative film prepared by the preparation method.
[0026] Finally, the application further discloses application of the biodegradable antibacterial slow-release preservative film in fruit and vegetable preservation.
[0027] The application has the following beneficial effects:
[0028] The biodegradable antibacterial slow-release preservative film prepared by the application can load cinnamaldehyde into Ag-MOFs to form Ag-MOFs-CIN nanoparticles, and the nanoparticles can be added to a base film to synergistically improve the mechanical properties of the film, so that the film has good tensile strength and elongation at break. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 It is an SEM graph of Example 1;
[0030] Figure 2 It is an SEM graph of Example 2;
[0031] Figure 3 It is an SEM graph of Example 3;
[0032] Figure 4 It is an SEM graph of Comparative Example 1;
[0033] Figure 5 This is the SEM image of Comparative Example 2;
[0034] Figure 6 This is the SEM image of Comparative Example 3;
[0035] Figure 7 This is the SEM image of Comparative Example 4;
[0036] Figure 8 The relative abundance of *Lactobacillus oryzae* at the bacterial genus level during 12 days of refrigeration at 4°C.
[0037] Figure 9 The relative abundance of fungal genera of *Lactobacillus* during 12 days of refrigeration at 4°C. Detailed Implementation
[0038] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0039] Raw material source information
[0040] Cinnamaldehyde: purchased from Maclean, C822622-500g, CAS: 104-55-2;
[0041] Carboxymethyl cellulose: purchased from Aladdin, C104986-500g, CAS: 9004-32-4;
[0042] Silver nitrate (AgNO3), terephthalic acid (TPA), tributyl acetyl citrate (ATBC), and N,N-dimethylformamide (DMF, 99%) were all purchased from Sigma.
[0043] Example 1
[0044] A biodegradable antibacterial slow-release preservation film is prepared as follows:
[0045] Step 1: AgNO3 and terephthalic acid were mixed in a molar ratio of 2:1, and 100 mL of N,N-dimethylformamide was added for dispersion in the dark for 11 h. Then, under a nitrogen atmosphere, the mixture was kept warm with insulating cotton and reacted in an oil bath at 120 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to 25 °C, filtered, and the filter residue was washed with ethanol. Finally, the filter residue was dried at 85 °C to obtain Ag-MOF nanoparticles.
[0046] Step 2: Mix 10g of cinnamaldehyde and 5g of Ag-MOF nanoparticles obtained in Step 1 to obtain a blend. Add 15mL of dichloromethane to the blend and stir until the dichloromethane is completely evaporated. Continue to add 15mL of dichloromethane and centrifuge and wash 4 times. After the dichloromethane is completely evaporated, Ag-MOFs-CIN nanoparticles are obtained.
[0047] Step 3: Add 2g of carboxymethyl cellulose to 110g of deionized water and stir at 85℃ to obtain a homogenized CMC solution. Then add glycerol to the CMC solution and homogenize. Mix the Ag-MOFs-CIN nanoparticles obtained in Step 2 with the CMC solution and stir uniformly at 25℃ for 9h to obtain a film-forming solution. Then sonicate the film-forming solution for 25min and dry it at 35℃ and 50% relative humidity for 9h to obtain the biodegradable antibacterial slow-release preservation film.
[0048] The amount of glycerol added is 40 wt% of carboxymethyl cellulose; the amount of Ag-MOFs-CIN nanoparticles added is 1 wt% of carboxymethyl cellulose.
[0049] Example 2
[0050] It is largely the same as Example 1, except that the amount of Ag-MOFs-CIN nanoparticles added is 0.5 wt% of carboxymethyl cellulose.
[0051] Example 3
[0052] It is largely the same as Example 1, except that the amount of Ag-MOFs-CIN nanoparticles added is 1.5 wt% of carboxymethyl cellulose.
[0053] Example 4
[0054] It is largely the same as Example 1, except that the amount of Ag-MOFs-CIN nanoparticles added is 2 wt% of carboxymethyl cellulose.
[0055] Example 5
[0056] It is largely the same as Example 1, except that the amount of Ag-MOFs-CIN nanoparticles added is 4 wt% of carboxymethyl cellulose.
[0057] Example 6
[0058] It is largely the same as Example 1, except that the amount of Ag-MOFs-CIN nanoparticles added is 6 wt% of carboxymethyl cellulose.
[0059] Comparative Example 1
[0060] A type of plastic wrap, prepared by the following method:
[0061] 2g of carboxymethyl cellulose (CMC) was added to 100g of deionized water and stirred at 85℃ to obtain a homogenized CMC solution. Glycerin was then added to the CMC solution and homogenized to obtain a film-forming solution. Finally, the film-forming solution was ultrasonically treated for 25 minutes and dried at 35℃ and 50% relative humidity for 9 hours to obtain a cling film. The amount of glycerin added was 40wt% of the CMC content.
[0062] Comparative Example 2
[0063] A type of plastic wrap, the specific preparation method of which is shown below:
[0064] Step 1: AgNO3 and terephthalic acid were mixed in a molar ratio of 2:1, and 100 mL of N,N-dimethylformamide was added for dispersion in the dark for 11 h. Then, under a nitrogen atmosphere, the mixture was kept warm with insulating cotton and reacted in an oil bath at 120 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to 25 °C, filtered, and the filter residue was washed with ethanol. Finally, the filter residue was dried at 85 °C to obtain Ag-MOF nanoparticles.
[0065] Step 2: Add 2g of carboxymethyl cellulose to 110g of deionized water and stir at 85℃ to obtain a homogenized CMC solution. Then add glycerol to the CMC solution and homogenize. Mix the Ag-MOF nanoparticles obtained in Step 1 with the CMC solution and stir uniformly at 25℃ for 9h to obtain a film-forming solution. Then sonicate the film-forming solution for 25min and dry it at 35℃ and 50% relative humidity for 9h to obtain the biodegradable antibacterial slow-release preservation film.
[0066] The amount of glycerol added is 40 wt% of carboxymethyl cellulose; the amount of Ag-MOF nanoparticles added is 1 wt% of carboxymethyl cellulose.
[0067] Comparative Example 3
[0068] A type of plastic wrap, the specific preparation method of which is shown below:
[0069] 2g of carboxymethyl cellulose was added to 110g of deionized water and stirred at 85℃ to obtain a homogenized CMC solution. Then, glycerol was added to the CMC solution and homogenized. Cinnamaldehyde was mixed with the CMC solution and stirred uniformly at 25℃ for 9h to obtain a film-forming solution. The film-forming solution was then ultrasonically treated for 25min and dried at 35℃ and 50% relative humidity for 9h to obtain the biodegradable antibacterial slow-release preservation film.
[0070] The amount of glycerol added is 40 wt% of carboxymethyl cellulose; the amount of cinnamaldehyde added is 1 wt% of carboxymethyl cellulose.
[0071] Comparative Example 4
[0072] A type of plastic wrap, the specific preparation method of which is shown below:
[0073] Step 1: AgNO3 and terephthalic acid were mixed in a molar ratio of 2:1, and 100 mL of N,N-dimethylformamide was added for dispersion in the dark for 11 h. Then, under a nitrogen atmosphere, the mixture was kept warm with insulating cotton and reacted in an oil bath at 120 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to 25 °C, filtered, and the filter residue was washed with ethanol. Finally, the filter residue was dried at 85 °C to obtain Ag-MOF nanoparticles.
[0074] Step 2: Add 2g of carboxymethyl cellulose to 110g of deionized water and stir at 85℃ to obtain a homogenized CMC solution. Then add glycerol to the CMC solution and homogenize. Mix cinnamaldehyde, Ag-MOF nano-ions obtained in Step 1, and CMC solution and stir evenly at 25℃ for 9h to obtain a film-forming solution. Then sonicate the film-forming solution for 25min and dry it at 35℃ and 50% relative humidity for 9h to obtain the biodegradable antibacterial slow-release preservation film.
[0075] The amount of glycerol added is 40 wt% of carboxymethyl cellulose; the amount of Ag-MOFs-CIN nanoparticles added is 1 wt% of carboxymethyl cellulose. The total amount of Ag-MOFs nanoparticles and cinnamaldehyde added is 4 wt% of carboxymethyl cellulose, with a mass ratio of cinnamaldehyde to Ag-MOFs nanoparticles of 2:1.
[0076] Part 1 Performance Testing
[0077] The following tests were performed on Examples 1-3 and Comparative Examples 1-6.
[0078] Thickness and mechanical property determination: The samples were cut into 1cm × 8cm millimeter dimensions, and the tensile strength (TS) and elongation at break (EB) of the samples were determined using a universal testing machine (CMT of 4104 MTS Systems Ltd.). The value of each parameter is the average of three measurements; the thickness was measured using a micrometer with an accuracy of 0.001mm at three different locations on the composite film.
[0079] Scanning electron microscopy (SEM): The microstructure of the sample was imaged using a field emission scanning electron microscope (NOVA NANOSEM-450, feiinc., USA). Gold sputtering was performed before image capture.
[0080] Composite membrane cytotoxicity assay: Cytotoxicity of samples was assessed using the CCK-8 assay. Human umbilical vein endothelial cells (HUVECs) were cultured in DMEM medium containing 1% penicillin and streptomycin and 10% fetal bovine serum at 37°C and 5% carbon dioxide. HUVECs were cultured at a density of 4 × 10⁶ cells per well. 4 Cells were seeded at a density of 1,000 cells per well in 24-well cell culture plates and incubated overnight. Then, the culture medium for each group was removed, and each UV-sterilized film sample group (6.9 mm in diameter) was placed into the well of the culture plate. Serum-free culture medium was added to each group, and incubation continued for 24 hours. Subsequently, the film and culture medium were removed, and culture medium containing 10% CCK-8 was added and incubated for 45 minutes. The absorbance was then measured at 450 nm, and cell viability was calculated according to Formula I.
[0081] Formula I: .
[0082] Experimental group: Examples 1-3, Comparative Examples 2-4;
[0083] Control group: Comparative example 1.
[0084] Antibacterial performance determination: The antibacterial properties of different films against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli were determined using the perforation method. Staphylococcus aureus and Escherichia coli were activated by shake-flask culture at 37°C for 16 h, followed by serial dilutions on a sterile operating table. 200 µL of the bacterial suspension was evenly spread onto the surface of LB agar medium. The medium was then perforated using a sterile perforator, and freshly prepared film-forming solution was injected into the wells. The plates were incubated at 37°C for 24 h, and the growth of bacterial colonies was observed, with the diameter of the inhibition zone measured. Each sample was measured in triplicate.
[0085] Test Results
[0086] Scanning electron microscopy (SEM) results are as follows Figures 1~7 As shown.
[0087] The results of the antibacterial performance test are shown in Table 1.
[0088] Table 1 Antibacterial Performance Data
[0089] As can be seen from the data in Table 1, compared with Comparative Example 1 and Comparative Example 2, the diameter of the inhibition zone for Staphylococcus aureus and Escherichia coli in Example 1 is significantly increased, indicating that the film of Example 1 has a better antibacterial effect.
[0090] Cell viability data are shown in Table 2.
[0091] Table 2 Cell viability
[0092] Cell survival rate (%) Example 1 98.21 Example 2 98.89 Example 3 97.57 Comparative Example 1 99.51 Comparative Example 2 98.17 Comparative Example 3 99.48 Comparative Example 4 98.25
[0093] As shown in Table 2, the films of each embodiment and comparative example are safe and non-irritating to cells.
[0094] The results of thickness and mechanical property tests are shown in Table 3.
[0095] Table 3 Mechanical property data of composite films
[0096] Thickness (um) Tensile strength (MPa) Elongation at break (%) Example 1 50.6 33.79 13.63 Example 2 49.5 33.71 13.13 Example 3 54.0 33.82 14.15 Comparative Example 1 49.7 29.95 6.51 Comparative Example 2 50.5 31.52 11.51 Comparative Example 3 49.9 30.45 6.86 Comparative Example 4 50.7 30.99 10.17
[0097] As can be seen from the data in Table 3, the films of Examples 1-3 have significantly improved tensile strength and elongation at break compared to the film of Comparative Example 1, and these values increase with the increase of Ag-MOFs-CIN nanoparticles.
[0098] Comparative Examples 2 and 3 show that using Ag-MOF nanoparticles or cinnamaldehyde alone has little effect on improving the mechanical properties of the base film. In Comparative Example 4, Ag-MOF nanoparticles and cinnamaldehyde were added separately, which further improved the tensile strength and elongation at break of the film, but the improvement was still limited. In contrast, in Example 1, cinnamaldehyde was loaded into Ag-MOFs to form Ag-MOFs-CIN nanoparticles, which were then added to the base film. The resulting composite film significantly improved the tensile strength and elongation at break of the film compared to Comparative Examples 1-4.
[0099] In summary, the biodegradable antibacterial slow-release preservation film prepared by the present invention loads cinnamaldehyde into Ag-MOFs to form Ag-MOFs-CIN nanoparticles, which are then added to the base film, and can synergistically improve the tensile strength and elongation at break of the film.
[0100] Part Two Tests
[0101] The antibacterial performance test results in Part 1 show that the biodegradable antibacterial sustained-release preservative film prepared in Example 1 of the present invention has a certain antibacterial effect. To further verify the antibacterial performance of the biodegradable antibacterial sustained-release preservative film of the present invention, the amount of Ag-MOFs-CIN nanoparticles added was increased from 1 wt% of carboxymethyl cellulose to 2 wt%, 4 wt%, and 6 wt%, i.e., Examples 4-6. The following tests were performed on Examples 4-6. The test groups are shown in Table 4.
[0102] Table 4 Test Groups
[0103] CON Control group Unpackaged C2MC CMC / 2Ag-MOFs-CIN film Example 4 C4MC CMC / 4Ag-MOFs-CIN film Example 5 C6MC CMC / 6Ag-MOFs-CIN film Example 6 CMC CMC film Comparative Example 1
[0104] Each group of milk vetch was packaged with a thin film, and the packaged milk vetch was refrigerated at 4°C for 12 days. After the refrigeration period, the milk vetch was tested, specifically:
[0105] DNA extraction: DNA extraction is performed according to the sample type.
[0106] Primers for PCR product acquisition correspond to the following regions: 16SV4 region primers (515F and 806R): for identifying bacterial diversity. 18SV4 region primers (528F and 706R): for identifying eukaryotic microbial diversity. ITS1 region primers (ITS5-1737F and ITS2-2043R): for identifying fungal diversity. Additionally, amplified regions include 16SV3-V4, 16SV4-V5, 16SV5-V7; archaea 16SV4-V5, archaea 16SV8; 18SV9, and ITS2. All PCR mixtures were added to 15 µL of Phusion High-FidelityPCR Master Mix, 0.2 µM primers, and 10 ng of genomic DNA template. The mixture was first denatured at 98 °C for 1 minute, then cycled 30 times at 98 °C (10 s), 50 °C (30 s), and 72 °C (30 s), and finally held at 72 °C for 5 minutes.
[0107] Mixing and purification of PCR products: PCR products are purified using magnetic beads. Equal volumes of PCR products are mixed according to their concentrations, thoroughly mixed, and then the PCR products are detected and the target band is recovered. The amplified PCR products are then subjected to PCR product detection.
[0108] Test results are as follows Figure 8 and Figure 9 As shown;
[0109] Figure 8 The changes in bacterial genera during the storage of *Cyperus difformis* were demonstrated. Detected genera included *Pseudomonas*, *Burkholderia*-*Cabarrion*-*Parabuchar*, *Dystridium*, *Chlorella*, *Serratia*, *Comamonella*, *Plasmodium*, *Yersinia*, *Acidophilus*, and *Mycobacterium*. *Pseudomonas* is one of the pathogens causing disease in edible fungi. In the unpackaged group, the relative abundance of *Pseudomonas* continuously increased, exceeding 75% after 12 days of storage. The CMC film group also showed a similar upward trend, but the final proportion remained low, at only 20.6%. In contrast, the CMC / Ag-MOFs-CIN composite film group showed superior inhibition, especially the CMC / 6Ag-MOFs-CIN group (Example 6), whose relative abundance of *Pseudomonas* remained below 5% throughout the storage period. This further demonstrates the controlled-release effect of the composite film on CIN, continuously inhibiting the growth and reproduction of *Pseudomonas* by maintaining a sufficiently high CIN concentration.
[0110] During the storage of edible fungi, the growth and metabolic activities of microorganisms and external disturbances can lead to changes in the microbial community structure, ultimately causing spoilage and decay. For example... Figure 9 The changes in the microbial community of *Dactylogyrus latifoliata* were shown under different packaging conditions and stored at 4°C for 12 days. Figure 9 The distribution differences of fungal genera in *Lactobacillus* samples from different packaging were shown. The results indicated that the fungal community mainly consisted of *Lactobacillus*, *Cryptococcus*, *Warstrobin*, *Penicillium*, *Rinne*, *Corynebacterium*, *Motierella*, *Podilla*, and *Kurtmania* genera. During storage, *Lactobacillus* was the dominant genus, and its presence was primarily attributed to *Lactobacillus*. With prolonged storage, the growth and reproduction of other microorganisms (especially the putrefactive fungus *Penicillium*) gradually eroded *Lactobacillus*, leading to a decrease in the relative abundance of the *Lactobacillus* genus. In the unpackaged group and the CMC group, *Penicillium* appeared on day 9 and day 12 of storage, respectively, while *Penicillium* was not detected in the CMC / Ag-MOFs-CIN composite film group. This finding suggests that the CMC / Ag-MOFs-CIN composite film effectively mitigated the harmful effects of *Penicillium* on *Lactobacillus*.
[0111] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A method for preparing a biodegradable antibacterial slow-release preservative film, characterized in that, Specifically, the following steps are included: Step 1: Mix AgNO3 and terephthalic acid, add N,N-dimethylformamide and react in a light-shielded oil bath to obtain Ag-MOF nanoparticles; Step 2: Mix cinnamaldehyde and Ag-MOF nanoparticles obtained in Step 1, add an organic volatile solvent to react, and obtain Ag-MOF-CIN nanoparticles after the organic volatile solvent has completely evaporated. Step 3: Dissolve carboxymethyl cellulose in deionized water to obtain a homogeneous CMC solution and add glycerol. Then mix the Ag-MOFs-CIN nanoparticles obtained in Step 2 with the CMC solution and stir evenly to obtain a film-forming solution. Then dry the film-forming solution to obtain the biodegradable antibacterial slow-release preservation film.
2. The preparation method according to claim 1, characterized in that, The molar ratio of AgNO3 to terephthalic acid mentioned in step 1 is 1~5:1~5.
3. The preparation method according to claim 1, characterized in that, The oil bath in step 1 is heated to 100℃~150℃ for 20~28 hours in a nitrogen atmosphere.
4. The preparation method according to claim 1, characterized in that, The mass ratio of cinnamaldehyde to Ag-MOF nanoparticles in step 2 is 2:
1.
5. The preparation method according to claim 1, characterized in that, The organic volatile solvent mentioned in step 2 is dichloromethane.
6. The preparation method according to claim 1, characterized in that, In step 3, the mass ratio of carboxymethyl cellulose to deionized water is 1~3:100~300; the amount of glycerol added is 30wt%~60wt% of carboxymethyl cellulose; and the amount of Ag-MOFs-CIN nanoparticles added is 0.5wt%~6wt% of carboxymethyl cellulose.
7. The preparation method according to claim 1, characterized in that, The stirring temperature in step 3 is 25°C, and the time is 8-14 hours. The drying temperature is 25-40°C, the relative humidity is 35-60%, and the time is 8-16 hours.
8. The preparation method according to claim 1, characterized in that, The more specific preparation method is shown below: Step 1: Mix AgNO3 and terephthalic acid, add 80-100 mL of N,N-dimethylformamide and disperse in the dark for 10-12 h. Then, carry out the oil bath reaction in the dark under a nitrogen atmosphere. After the reaction is completed, cool naturally to 25°C, filter, wash the filter residue with ethanol, and finally dry the filter residue at 60-90°C to obtain Ag-MOF nanoparticles. Step 2: Mix cinnamaldehyde and Ag-MOF nanoparticles obtained in Step 1 to obtain a blend. Add dichloromethane to the blend and stir until the dichloromethane is completely evaporated. Continue to add dichloromethane and centrifuge and wash 1 to 5 times. After the dichloromethane is completely evaporated, Ag-MOFs-CIN nanoparticles are obtained. Step 3: Add carboxymethyl cellulose to deionized water and stir at 60-90℃ to obtain a homogenized CMC solution. Then add glycerol to the CMC solution and homogenize. Mix the Ag-MOFs-CIN nanoparticles obtained in Step 2 with the CMC solution and stir uniformly at 25℃ for 8-14 hours to obtain a film-forming solution. Then sonicate the film-forming solution for 20-30 minutes and dry it to obtain the biodegradable antibacterial slow-release preservation film.
9. A biodegradable antibacterial slow-release preservative film, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.
10. The application of the biodegradable antibacterial slow-release preservation film as described in claim 9 in the preservation of fruits and vegetables.