Preparation method and application of origanum vulgare essential oil-MOF modified alcohol-soluble protein preservative film

Abstract

The invention relates to the field of food packaging, and provides a preparation method and application of an origanum vulgare essential oil-MOF modified alcohol-soluble protein preservative film. The preparation method comprises the following steps: mixing gamma-CD-MOF and origanum vulgare essential oil, reacting under a high-pressure reaction condition, centrifuging, washing and drying to obtain an origanum vulgare essential oil loaded MOF material; adding a plasticizer into the zein solution to prepare a membrane solution; and adding the MOF material loaded with the origanum vulgare essential oil into the film liquid, fully mixing, forming and drying to finally obtain the MOF-based food packaging film. According to the nano composite film disclosed by the invention, the water vapor barrier property, the ultraviolet barrier property and the oxidation resistance are remarkably improved. The nano composite film is applied to fresh-keeping experiments of strawberries and blueberries, so that the loss of nutritional ingredients is remarkably reduced, the shelf life of fruits is effectively prolonged, and an excellent fresh-keeping effect is shown. Compared with a traditional packaging material, the composite film provided by the invention not only is comprehensively optimized in performance, but also can provide more possibilities for a food fresh-keeping technology.

Description

Technical Field

[0001] The invention relates to the field of food packaging technology and food preservation, and in particular to a preparation method and application of an oregano essential oil-MOF modified zein fresh-keeping film. Background Art

[0002] Fresh fruits are prone to spoilage and quality deterioration after harvest due to their high moisture content, rich nutrients and strong physiological activity, which poses a major challenge to preservation and storage. Food packaging plays a vital role in ensuring food quality and safety by preventing contamination and damage caused by biological, chemical and physical factors, stabilizing food quality and extending its shelf life, while providing effective protection during production, transportation and storage. Currently, petroleum-based plastics are widely used in the field of food preservation due to their excellent flexibility, durability and low cost. However, their non-degradability and the environmental problems they cause have led to a growing demand for sustainable and environmentally friendly alternatives. Therefore, degradable polymer materials, such as polysaccharides, proteins and lipids, have attracted much attention in recent years as potential alternatives to traditional plastics.

[0003] Among many degradable polymers, protein-based films have shown significant environmental sustainability and gas barrier properties due to their excellent plasticity, biodegradability, biocompatibility and hydrophobicity, and have become one of the hot topics in the research of food preservation materials. Zein film (Zein), as a natural protein-based food preservation material, has good mechanical properties and environmental friendliness, which can effectively extend the shelf life of food and reduce dependence on traditional petroleum-based plastics. However, zein film still faces some problems in practical applications, such as low mechanical strength, poor water vapor barrier properties and insufficient antioxidant properties, which limit its wide application in food preservation. Therefore, developing composite modified materials or introducing functional active ingredients to improve their performance has become an important research direction.

[0004] Oregano essential oil (OEO) has shown significant advantages in the field of food preservation due to its natural antibacterial and antioxidant properties. It can effectively inhibit the growth of microorganisms and delay food oxidation, and as a natural extract, its safety and environmental protection are highly recognized. However, the high volatility and poor stability of oregano essential oil limit its widespread use in practical applications. MOF can be combined with active ingredients to form functional composite materials due to its unique high specific surface area, controllable porous structure and good stability. Loading oregano essential oil (OEO) into MOF can not only significantly improve the stability of oregano essential oil, but also further enhance the antioxidant properties of the film by compounding it into zein film. In addition, the introduction of MOF can also improve the mechanical strength and gas barrier properties of zein film, thereby comprehensively optimizing its preservation effect.

[0005] The MOF-loaded corn protein cling film is a food packaging material that combines high antibacterial efficiency, excellent water barrier properties, and environmental friendliness. By integrating the multifunctional properties of MOF and the biodegradability of corn protein, it not only solves the original performance deficiencies of corn protein film, but also shows significant advantages in extending the shelf life of food and reducing food waste. The development of this composite film provides a new direction for efficient and sustainable food preservation technology, and is of great significance in reducing dependence on petroleum-based plastics and environmental pollution. Summary of the invention

[0006] The first objective of the present invention is to address the above-mentioned problems and provide a preparation method and application of an oregano essential oil-MOF modified alcohol-soluble protein cling film, wherein the prepared composite film has good ultraviolet barrier properties and good antioxidant activity.

[0007] To achieve the above object, according to the technical solution of the present invention, a preparation method and application of oregano essential oil-MOF modified zein cling film is provided, and the steps are as follows:

[0008] Step 1, preparation of MOF inclusion complex loaded with oregano essential oil:

[0009] γ-CD-MOF and oregano essential oil reacted in a high-temperature and high-pressure reactor. The reaction product was centrifuged, washed and dried to successfully prepare OEO@CD-MOF.

[0010] Step 2, preparation of oregano essential oil-MOF modified zein plastic wrap:

[0011] After dissolving zein in an ethanol solution and stirring evenly, add the plasticizer glycerol, continue stirring and mixing, and then add OEO@CD-MOF to disperse evenly. Finally, the prepared film-forming solution is cast into a film, and after drying, an OEO@CD-MOF-modified zein cling film is obtained.

[0012] The oregano essential oil in this application is a plant extract with antibacterial, antioxidant and anti-inflammatory functions, but it has the disadvantages of being volatile, unstable and easily oxidized in practical applications. γ-CD-MOF is a porous metal organic framework material constructed by cyclodextrin and potassium ions. Its unique porous structure and high specific surface area significantly improve the encapsulation efficiency of oregano essential oil, enhance its stability and reduce volatility loss. At the same time, the preservative film prepared by adding OEO@CD-MOF nanoparticles to the zein solution can effectively extend the shelf life of food.

[0013] Furthermore, in step 1, γ-CD-MOF and oregano essential oil (OEO) were mixed in a mass ratio of 4:1 (w / w).

[0014] Furthermore, in step 1, the mixture is heated in a high pressure reactor at 120° C. for 60 minutes.

[0015] Furthermore, in step 1, the sample is centrifuged and washed 2-3 times (5000 rpm, 10 min) using anhydrous ethanol to remove the oregano essential oil that is not loaded.

[0016] Furthermore, in step 1, the sample was dried in a vacuum drying oven at 50° C. for 5 h.

[0017] Furthermore, in step 2, the concentration of the ethanol solution was 80% (v / v), 1 g of Zein was added for every 10 mL of ethanol solution, and the stirring time was 30 min.

[0018] Furthermore, in step 2, 0.15 mL of glycerol was added per 1 g of Zein, and stirring was continued at 50° C. for 60 min.

[0019] Further, in step 2, the addition amount of OEO@CD-MOF is 0, 1, 3, 5, 7 wt% (based on Zein mass), preferably 5 wt%.

[0020] Furthermore, the film solution in step 2 was dried at 60°C for 4 h to obtain the zein preservative film loaded with OEO@CD-MOF.

[0021] The second object of the present invention is to provide an oregano essential oil-MOF modified zein fresh-keeping film, which is prepared by the above method.

[0022] The third object of the present invention is to provide the use of the above film as an antioxidant material.

[0023] A fourth object of the present invention is to provide the use of the above film as a high-moisture fruit preservative film.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The present invention selects OEO@CD-MOF nanoparticles and mixes them with zein, and uses a casting method to prepare a Zein-OEO@CD-MOF composite film. OEO@CD-MOF as a nanofiller can significantly improve the tensile strength, UV barrier properties and water barrier properties of the Zein-OEO@CD-MOF composite film.

[0026] 2. The addition of OEO@CD-MOF nanoparticles significantly improved the antioxidant properties of the composite film.

[0027] 3. Zein-OEO@CD-MOF composite membrane was used to preserve fresh strawberries and blueberries, and stored at room temperature for 6 days and 12 days respectively. The results showed that the Zein-OEO@CD-MOF-5% composite membrane treatment group showed the best preservation effect in terms of strawberry appearance, weight loss, hardness, soluble solids content and titratable acid content; at the same time, it also showed good preservation performance in terms of blueberry appearance, weight loss and titratable acid content. This provides feasibility verification and theoretical basis support for the further application of Zein-OEO@CD-MOF composite membrane in the field of preservation of high-moisture fruit and other foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Scanning electron microscope images of γ-CD-MOF and OEO@CD-MOF.

[0029] Figure 2 Nitrogen adsorption-desorption isotherms before and after γ-CD-MOF encapsulation of essential oil.

[0030] Figure 3 SEM images of the membrane surface prepared with different OEO@CD-MOF addition amounts.

[0031] Figure 4 The thickness of the composite film with different OEO@CD-MOF addition amounts.

[0032] Figure 5 Tensile strength and elongation at break of composite films with different OEO@CD-MOF addition amounts

[0033] Figure 6 UV-visible light transmittance of composite films with different OEO@CD-MOF addition amounts.

[0034] Figure 7 Water vapor permeability of composite films with different OEO@CD-MOF addition amounts.

[0035] Figure 8 DPPH radical scavenging rate of composite membranes with different OEO@CD-MOF addition amounts.

[0036] Fig. 9 (a) Visual changes, (b) weight loss, (c) firmness, (d) soluble solids, and (e) titratable acid content of strawberries under different treatments during 0, 2, 4, and 6 days of storage.

[0037] Fig.10 (a) Visual changes, (b) weight loss, and (c) titratable acid content of blueberries under different treatments during 0, 4, 8, and 12 days of storage. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0039] Example 1

[0040] Preparation of OEO@CD-MOF nanoparticles

[0041] Step 1, synthesis of γ-CD-MOF: γ-CD (1296 mg, 1 mmol), potassium hydroxide (448 mg, 8 mmol) and deionized water (40 mL) were mixed at room temperature and filtered through a 0.45 μm membrane. The filtrate was then mixed with methanol (24 mL) to form a milky white solution, which was heated in a water bath at 60 ° C for 10 minutes until clear. The solution was treated with ultrasound at 480 W for 10 minutes, and PEG-8000 was added at the beginning of ultrasound. After the ultrasound treatment step, the mixture was allowed to stand for 1 hour. The resulting precipitate was collected by centrifugation, washed several times with methanol, redispersed, and dried in vacuo at 50 ° C for 12 hours.

[0042] Step 2: Synthesis of OEO@CD-MOF nanoparticles: γ-CD-MOF and oregano essential oil were mixed at a mass ratio of 4:1 (w / w) and heated in a high-pressure reactor at 120°C for 60 minutes. After cooling, the sample was washed three times with anhydrous ethanol to remove unloaded OEO, and then dried under vacuum conditions at 50°C for 12 hours.

[0043] Experimental results:

[0044] SEM images ( Figure 1 ) shows that the crystal structure of γ-CD-MOF is blocky and polyhedral, with clear crystal edges. The crystal morphology has high regularity, the surface is relatively smooth, and no obvious surface coverage or deformation is observed. The crystal morphology of OEO@CD-MOF is basically similar to that of γ-CD-MOF, but there is slight roughening or particle attachment on the crystal surface, which may be OEO. The crystal shape still maintains a good polyhedral structure, indicating that the framework structure of γ-CD-MOF is not destroyed during the encapsulation process.

[0045] Determination of N2 adsorption-desorption of γ-CD-MOF and OEO@CD-MOF

[0046] The nitrogen adsorption and desorption isotherms of the samples were measured using a dual-station physical adsorption analyzer to characterize the specific surface area of ​​the material. In the experiment, the γ-CD-MOF crystals were first soaked in dichloromethane for 3 days to fully remove impurities and unreacted substances remaining on the surface, thereby ensuring the cleanliness and integrity of the crystal pores. Subsequently, the samples were pre-activated and dried under vacuum conditions to remove solvent molecules, further improving the accuracy of the test. Finally, the samples were degassed at 100°C for 12 hours to completely remove the adsorbed gas and water molecules in the pores to ensure reliable adsorption isotherm data.

[0047] Experimental results:

[0048] Figure 2 Figure 2 shows the nitrogen adsorption-desorption isotherms before and after encapsulation of essential oils by γ-CD-MOF. Before encapsulation, γ-CD-MOF exhibited typical microporous adsorption behavior, characterized by a rapid increase in nitrogen absorption at lower relative pressures, indicating its considerable micropore volume and high specific surface area. However, after encapsulation, the maximum nitrogen adsorption capacity decreased significantly from 148.97 cm 3 / gSTP to 6.742 cm 3 / gSTP, while the specific surface area increased from 449.7216 m 2 / g is reduced to 3.2546m 2 These findings confirm that the essential oil molecules successfully occupied the pore structure of the MOF, thereby filling the accessible channels, hindering the adsorption of nitrogen, and significantly reducing the pore effectiveness and surface area of ​​the material.

[0049] Preparation of OEO@CD-MOF modified zein film

[0050] Zein (5 g) was added to 50 mL of 80% ethanol solution (v / v) and magnetically stirred for 30 minutes until completely dissolved. Glycerol (0.15 mL / g) was then introduced into the film-forming solution and stirred continuously for 60 min at 50 °C. After the film solution was cooled to room temperature, different masses of OEO@CD-MOF (0, 1, 3, 5, 7 wt%) were added to the zein solution and stirred continuously for 30 min. Finally, the film-forming solution was slowly poured into a polypropylene mold and dried at 60 °C for 4 h to obtain a zein preservative film loaded with OEO@CD-MOF.

[0051] Experimental results:

[0052] The surface SEM images of the obtained membrane are shown in Figure 3As shown. The SEM images intuitively show the morphological changes of the composite membranes at different OEO@CD-MOF concentrations. The surface of the pure zein membrane is smooth, uniform and has no obvious defects, indicating that it has good film-forming properties. However, with the gradual increase in the amount of OEO@CD-MOF added (1-5%), the surface morphology of the composite membrane changed significantly, and a granular structure appeared. These particles were evenly dispersed on the surface and in the matrix of the composite membrane, and no obvious agglomeration phenomenon occurred, indicating that OEO@CD-MOF has good dispersion in the zein matrix. However, when the OEO@CD-MOF content increased to 7%, the surface roughness was significantly enhanced, and obvious particle aggregation occurred. This aggregation may be caused by incomplete dispersion or local clustering within the zein matrix due to excessive OEO@CD-MOF.

[0053] Thickness and mechanical properties of Zein-OEO@CD-MOF composite films

[0054] The thickness of the composite film was measured in micrometers with the unit of millimeters. The film samples were cut into 60 mm × 20 mm rectangles with an initial measurement length of 30 mm and a tensile speed of 36 mm / min. The tensile strength (TS) and elongation at break (EB) of the film were measured using a physical properties analyzer.

[0055]

[0056] Where FN is the maximum stress on the film (N), A is the cross-sectional area of ​​the film (mm2); L1 is the length of the film before it breaks (mm), and L0 is the initial length of the film (mm).

[0057] Experimental results:

[0058] The thickness of the film mainly depends on its solid content. The thickness of the composite film with different OEO@CD-MOF addition amounts is shown in Figure 2. Figure 4 As shown in Figure 3, with the increase of the addition amount, the thickness of the composite film gradually increases.

[0059] like Figure 5As shown in the figure, the introduction of OEO@CD-MOF significantly improves the mechanical properties of pure zein film. With the increase of OEO@CD-MOF content, the tensile strength of zein film increases from 10.958MPa to 13.89MPa. When the OEO@CD-MOF content reaches 5%, the elongation at break of the composite film increases from 3.883% to 6.959%. This performance improvement may be attributed to the uniform dispersion of low-concentration OEO@CD-MOF in the film and its good compatibility with zein, which enhances the mechanical connection of the internal network structure of the membrane. However, when the content of OEO@CD-MOF increases to 7%, the elongation at break decreases to 6.564%. This decrease may be due to the aggregation of high-concentration OEO@CD-MOF, which reduces the free volume of the composite film and increases its crystallinity. Therefore, the enhanced rigidity leads to a decrease in the flexibility of the film.

[0060] UV-Visible light transmittance of composite films

[0061] The composite film was cut into pieces with a size of 1×4 cm 2 The rectangular sheet was attached to the transparent side of the colorimetric tube. The transmittance of the composite film to UV-visible light was evaluated by scanning in the wavelength range of 300-800nm ​​using a UV-visible spectrophotometer.

[0062] Experimental results:

[0063] like Figure 6 As shown in the figure, the composite film exhibits low UV transmittance, which is attributed to the benzene ring structure of aromatic amino acids in zein, which gives it excellent UV blocking properties. Compared with pure zein film, the UV transmittance of the composite film further decreases with the increase of OEO@CD-MOF content, while maintaining an acceptable visible light transmittance. This phenomenon may be related to the introduction of OEO@CD-MOF, which may increase the thickness of the composite film. Specifically, with the increase of OEO@CD-MOF concentration (1%, 3%, 5% and 7%), the UV transmittance, especially in the region below 400nm, decreases significantly. Therefore, the zein-OEO@CD-MOF composite film can effectively block UV radiation and delay the deterioration of fruits, showing good potential for practical applications.

[0064] Water vapor transmission rate (WVP) of composite films

[0065] The composite film was used to seal 50 mL centrifuge tubes containing a fixed amount of anhydrous CaCl2, and the initial weight of each sealed tube was recorded. Subsequently, these centrifuge tubes were placed in a constant temperature and humidity chamber at 25°C and 75% relative humidity for 72 hours. After this time, the weight of each centrifuge tube was measured again.

[0066] Experimental results:

[0067] like Figure 7 As shown in the figure, the WVP of the composite film decreases with the increase of OEO@CD-MOF content, indicating that its water resistance is improved. This improvement may be attributed to the role of OEO@CD-MOF as a filler, which increases the density of the film, reduces the transmission path of water vapor, or forms intermolecular hydrogen bonds with the film, thereby reducing water interaction and reducing water permeability. Lower WVP helps maintain the moisture balance of food, prevent quality deterioration and extend shelf life.

[0068] Oxidation resistance of composite films

[0069] An equal amount of the composite film sample was dissolved in 10 mL of DPPH ethanol solution. The solution was allowed to stand at 25°C for 30 minutes, and its absorbance was measured at 517 nm to calculate its scavenging activity.

[0070]

[0071] Experimental results:

[0072] like Figure 8 As shown in the figure, pure zein film exhibits a certain degree of antioxidant capacity. The addition of OEO@CD-MOF significantly improves the antioxidant properties of the composite film, and the scavenging activity increases with the increase of the added concentration. The improvement of the DPPH radical scavenging activity of the composite film can be attributed to the phenolic hydroxyl groups in oregano essential oil, which act as hydrogen donors during the oxidation process and inhibit the lipid peroxidation chain reaction. This shows that the OEO@CD-MOF composite film has great potential for antioxidant applications in food packaging.

[0073] Application of Zein-OEO@CD-MOF composite membrane in the preservation of strawberries and blueberries

[0074] In the preservation experiment of strawberries and blueberries, in order to ensure the reliability and consistency of the results, the selected samples were consistent in variety, maturity, size and shape, and individuals with defects, mechanical damage or microbial contamination were excluded. During the experiment, the samples were kept fresh at room temperature for 6 and 12 days, respectively. Photos were taken regularly during the experiment to visually evaluate the preservation effect. In addition, the following multiple freshness indices were measured to evaluate the quality of strawberries. The changes in fruit weight and hardness were weighed regularly, and the soluble solid content of the samples was determined using a handheld Abbe refractometer, and the titratable acid content in the samples was determined by acid-base titration. Each experiment contained four treatment groups: control group (CK), polyethylene film group (PE), zein film group (Zein), and composite film treatment group (Zein-OEO@CD-MOF-5%).

[0075] Experimental results:

[0076] like Fig. 9 As shown in the figure, the strawberries in different treatment groups showed significant differences in appearance, weight loss, fruit hardness, and TSS and TA contents during the 6-day storage period. The strawberries in the CK group darkened in color after 2 days, mold and softening appeared on the 4th day, and most of them rotted on the 6th day. The weight loss and hardness decreased the fastest, and the TSS and TA contents also changed significantly. The strawberries in the PE film group softened slightly on the second day, but still had mold spots and rot after 4 days, and TSS and TA decreased rapidly. The strawberries in the Zein film treatment group remained basically intact at 4 days, but mold and rot appeared partially on the 6th day. In contrast, the Zein-OEO@CD-MOF-5% treatment group performed best. The strawberries remained fresh in the first 4 days of storage, only slightly softened and discolored on the 6th day, had the lowest weight loss rate, the slowest hardness decrease, and the smallest decrease in TSS and TA content, showing excellent preservation effect. The Zein-OEO@CD-MOF-5% composite film treatment group showed the best preservation effect in terms of strawberry appearance, weight, hardness, and TSS and TA content.

[0077] Changes in appearance, weight loss and titratable acid content of blueberries during storage Fig.10 shown. Fig.10 a shows that as the storage time increased, the blueberries in the CK group showed obvious dehydration and shrinkage in the later stage, while the other treatment groups only shrank slightly. Fig.10 b shows that the weight loss rate of blueberries increased over time, but the PE group and Zein group significantly slowed down the growth of the weight loss rate and better maintained the moisture of blueberries. Fig.10 c shows that the titratable acid content gradually decreased, among which the Zein-OEO@CD-MOF-5% group decreased the slowest, effectively maintaining the flavor and quality of blueberries, reflecting its advantage in slowing down quality deterioration.

[0078] In summary, the present invention uses an ultrasound-assisted method to efficiently synthesize γ-CD-MOF, successfully prepares OEO@CD-MOF, and develops a zein-based composite film containing OEO@CD-MOF. Adding 5% OEO@CD-MOF to the zein-based film improves the mechanical properties, UV protection, water vapor permeability and antioxidant properties of the composite film. Finally, the Zein-OEO@CD-MOF composite film was applied to the preservation of strawberries and blueberries. The experimental results show that the composite film effectively reduces the nutrient loss of these fruits, thereby extending their shelf life. Therefore, the Zein-OEO@CD-MOF composite film is a sustainable and efficient active packaging material with good application potential.

[0079] The above embodiments are provided only to clearly illustrate the technical content of the present invention, with the purpose of helping to understand the present invention, and do not impose any limitation on the specific embodiments of the present invention. Those of ordinary skill in the art can make various modifications, changes, improvements or substitutions within the spirit and substance of the present invention, and these changes all belong to the protection scope of the present invention. Obviously, it is impossible to exhaustively describe all embodiments of the present invention, but any reasonable adjustment or extension made on the basis of the present invention should be regarded as a part of the present invention and protected by it.

Claims

1. A preparation method and application of oregano essential oil-MOF modified alcohol-soluble protein cling film, characterized in that: The following steps are included: Step 1, preparation of MOF inclusion complex loaded with oregano essential oil: γ-CD-MOF and oregano essential oil reacted in a high-temperature and high-pressure reactor. The reaction product was centrifuged, washed and dried to successfully prepare OEO@CD-MOF. Step 2, preparation of oregano essential oil-MOF modified zein plastic wrap: After dissolving zein in an ethanol solution and stirring evenly, add the plasticizer glycerol, continue stirring and mixing, and then add OEO@CD-MOF to disperse evenly. Finally, the prepared film-forming solution is cast into a film, and after drying, an OEO@CD-MOF-modified zein cling film is obtained.

2. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In the step 1, γ-CD-MOF and oregano essential oil (OEO) are mixed in a mass ratio of 4:1 (w / w).

3. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In step 1, the mixture is heated in a high pressure reactor at 120° C. for 60 minutes.

4. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In step 1, the sample is centrifuged and washed 2-3 times (5000 rpm, 10 min) using anhydrous ethanol to remove the oregano essential oil that is not loaded.

5. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In step 1, the sample is dried in a vacuum drying oven at 50° C. for 5 h.

6. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: The concentration of the ethanol solution in step 2 is 80% (v / v), 1 g of Zein is added to every 10 mL of ethanol solution, and the stirring time is 30 min.

7. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In step 2, 0.15 mL of glycerol was added for every 1 g of Zein, and the mixture was stirred continuously at 50° C. for 60 min.

8. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In the step 2, the addition amount of OEO@CD-MOF is 0, 1, 3, 5, and 7 wt% (based on Zein mass), and stirring is continued for 30 min.

9. The method for preparing a MOF-based food packaging film according to claim 1, characterized in that: In the step 2, the film solution is dried at 60° C. for 4 h to obtain a zein preservative film loaded with OEO@CD-MOF.

10. An oregano essential oil-MOF modified zein film, characterized in that: The method is prepared by any one of claims 1 to 9.

11. Use of the oregano essential oil-MOF modified zein film according to claim 10 as an antioxidant material.

12. Use of the oregano essential oil-MOF modified zein film according to claim 10 as a new food preservative film.

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