Preparation method for food nanofiber film having sustained-release antibacterial activity, and use thereof

Abstract

A preparation method for a food nanofiber film having sustained-release antibacterial activity, and a use thereof, belonging to the technical field of food packaging films. A metal-organic framework material MIL-101(Fe) is used to encapsulate natural plant essential oils, while polylactic acid and polycaprolactone are used as film-forming substrates, to prepare a food nanofiber film capable of exerting a long-term and efficient antibacterial effect; by means of encapsulating highly volatile natural plant essential oils with MIL-101(Fe), the residence time of antibacterial substances in the top space of the packaging film can be extended, increasing the utilization of the essential oils and achieving long-lasting antibacterial effects. Moreover, MIL-101(Fe) has a specific surface area of 2865 m2 / g, which can greatly improve the encapsulation rate and sustained-release effect of the plant essential oils. At the same time, the film, prepared by electrospinning, has a high specific surface area, which is conducive to increasing the encapsulation rate of the plant essential oils. This preparation method is safe, environmentally friendly, simple to operate, and easy to promote and apply.

Description

A method for preparing a food nanofiber membrane with sustained-release antibacterial activity and its application. Technical Field

[0001] This invention belongs to the field of food packaging film technology, specifically relating to a method for preparing a food nanofiber film with sustained-release antibacterial activity and its application. Background Technology

[0002] With rapid globalization and urbanization, food safety issues have increased dramatically. People are paying more and more attention to food safety and high quality, leading to significant changes in the food packaging industry. Functional packaging technology has become a new research hotspot, with preservation, environmental protection, and convenience emerging as new development directions for food packaging. Food contamination can occur at multiple stages, including production, sales, packaging, and storage. Animal-derived foods are rich in protein and various essential amino acids, but are susceptible to chemical spoilage and microbial decay, resulting in economic losses and threatening consumer health. Antimicrobial packaging is designed primarily to prevent food from being affected by microorganisms such as bacteria and fungi, as well as environmental factors, during processing. By releasing antimicrobial substances into the surrounding environment, it aims to extend shelf life or improve food quality.

[0003] Biodegradable active food packaging materials have great development potential, not only reducing the resource and environmental problems caused by petroleum-based packaging, but also extending the shelf life of food through their antibacterial and antioxidant activities. Among various biodegradable polymers, polylactic acid (PLA), made from sustainable and renewable materials (starch, corn, etc.), has been widely used in the food industry. Its blending with polycaprolactone can further improve the mechanical and barrier properties of films. Electrospinning technology is a simple, environmentally friendly, and cost-effective method for manufacturing various nanofibers from different viscoelastic polymer solutions, and electrospun fibers have a large specific surface area and high load-bearing capacity.

[0004] Natural plant essential oils are aromatic compounds extracted from plants, often possessing strong antibacterial effects. However, due to their high volatility, direct use may produce a strong, irritating odor. Encapsulating plant essential oils in nanocarriers can prolong the release of these compounds, enhancing their antibacterial effect by extending the time these volatile antibacterial agents remain in the headspace. As a type of hybrid porous inorganic material, metal-organic framework (MOF) nanoparticles, constructed from metal ions and organic ligands, have attracted widespread attention in gas adsorption, electrochemical sensing, and antibacterial applications due to their ease of synthesis, long-term stability, and tunable functionality. MIL-101(Fe) is a typical porous organic-inorganic hybrid material that enhances affinity with polymer matrices, demonstrating excellent performance as a nanofiller in the construction of high-performance nanocomposites.

[0005] A search revealed a Chinese invention patent with publication number CN116019141A, which discloses a method for preparing a nanocellulose aerogel antibacterial essential oil sustained-release system. The essential oil molecules are released through the aerogel pores in a diffuse manner into the packaging environment or the surface of fruits and vegetables, thus exerting a strong antibacterial effect. However, this method requires large-scale equipment such as a supercritical carbon dioxide device, placing high demands on the equipment. The preparation process of the nanocellulose aerogel is also quite cumbersome and time-consuming, hindering its industrial application.

[0006] Chinese invention patent application CN103725017A discloses a fish collagen antibacterial film with sustained-release effect and its preparation method. The film is made by mixing fish collagen with glycerin and cinnamon essential oil and drying it. The invention still needs to be further improved in terms of the encapsulation rate of essential oil and the sustained-release effect of essential oil.

[0007] In addition, Chinese invention patent application publication number CN108752610A discloses an edible antibacterial film for slow-release essential oils and its preparation method. Antibacterial essential oils, plasticizers and emulsifiers are added to a film storage liquid composed of viscous and gelatin to obtain an edible film for slow-release essential oils. The preparation method of this film is simple and inexpensive, but the encapsulation rate of essential oils is not high.

[0008] Existing methods have low encapsulation rates for essential oils. Therefore, it is of great significance to develop a film with high encapsulation rate and long-lasting antibacterial properties to better apply plant essential oils to food preservation. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention aims to solve the problems of excessive addition of antibacterial substances in existing food packaging and the mismatch between the release pattern of antibacterial substances and the need to inhibit food spoilage. It proposes a method to encapsulate natural plant essential oils using a metal-organic framework material MIL-101(Fe) and using polylactic acid (PLA) and polycaprolactone (PCL) as film-forming substrates to prepare a food nanofiber membrane capable of long-term and efficient antibacterial activity, achieving highly efficient antibacterial and long-lasting preservation effects.

[0010] To achieve the above technical objectives, the present invention adopts the following solution:

[0011] A method for preparing a food nanofiber membrane with sustained-release antibacterial activity, comprising the following specific steps:

[0012] Step 1: Preparation of MIL-101(Fe);

[0013] (1) Dissolve FeCl3·6H2O in N,N-dimethylformamide (DMF), add acetic acid, and then add terephthalic acid (H2BDC). After ultrasonic treatment, a mixed solution is obtained. The solution is then transferred to a high-pressure reactor lined with polytetrafluoroethylene for reaction. After the reaction, a brick-red suspension is obtained.

[0014] (2) Centrifuge the brick-red suspension obtained in step (1) to obtain a brick-red precipitate; then wash with DMF and methanol respectively (to remove unreacted raw materials and DMF respectively), centrifuge the collected precipitate again after washing, and finally dry it to obtain the product MIL-101(Fe).

[0015] Step 2: Preparation of MIL-101(Fe) nanocrystals loaded with natural plant essential oils;

[0016] (1) First, natural plant essential oils are added to dichloromethane (DCM) to form a mixed solution; then, the MIL-101(Fe) obtained in step one is immersed in the mixed solution and placed in a sealed glass bottle and stirred overnight (stirring causes the plant essential oils to embed into the pores of MIL-101(Fe)) to obtain a MIL-101(Fe) solution loaded with natural plant essential oils.

[0017] (2) After centrifuging the MIL-101(Fe) solution loaded with natural plant essential oil obtained in step (1), collect the precipitate, disperse it in DCM for centrifugation and washing, repeat the washing several times, collect the washed precipitate and evaporate it overnight in a fume hood to obtain MIL-101(Fe) nanocrystals loaded with natural plant essential oil.

[0018] Step 3: Preparation of electrospinning solution

[0019] PLA and PCL were added sequentially to a mixed solvent of DCM and DMF, and stirred evenly at room temperature to obtain a mixed solution; then the MIL-101(Fe) nanocrystals loaded with natural plant essential oils prepared in step two were added, and the mixture was stirred for a period of time to obtain an electrospinning solution.

[0020] Step 4: Preparation of sustained-release antibacterial nanofiber packaging film by electrospinning;

[0021] The spinning solution prepared in step three is spun using electrospinning technology (the spinning solution is ultrasonically degassed for 10 minutes before use). First, the spinning solution is injected into a syringe, then the corresponding parameters are set for spinning. Tin foil is used as the receiving substrate and collected by a rotating drum. Finally, the fiber membrane on the aluminum foil is peeled off and vacuum dried to obtain a food nanofiber membrane.

[0022] Preferably, in step (1), the ratio of FeCl3·6H2O, N,N-dimethylformamide solution, acetic acid, and terephthalic acid is 2.703g:60mL:1mL:0.830g, wherein the molar ratio of FeCl3·6H2O and H2BDC is 2:1.

[0023] Preferably, the ultrasonic treatment time in step (1) is 30 min; the reaction temperature in the high-pressure reactor is 120 °C and the time is 24 h.

[0024] Preferably, the centrifugation conditions in step (2) are: centrifugation at 8000 rpm for 10 min; the drying treatment temperature is 100-120℃ and the time is 10-12 h.

[0025] Preferably, in step two (1), the natural plant essential oil includes one or more of the following: mustard oil, oregano oil, cinnamon oil, clove oil, garlic oil, thyme oil, lemongrass oil, bergamot oil, lemon oil, tea tree oil, rosemary oil, peppermint oil, chamomile oil, lime oil, lemongrass oil, citronella oil, artemisia oil, and rose oil; the concentration of the natural plant essential oil in the mixed solution is 100 mg / mL.

[0026] Preferably, in step (2), the centrifugation conditions are: centrifugation at 8000 rpm for 10 min.

[0027] Preferably, in step three, the mass ratio of PLA to PCL is 3:7; the volume ratio of DCM to DMF is 5:1; and in the obtained electrospinning solution, the total amount of PLA and PCL is 8wt%, the total amount of DCM and DMF is 89wt%, and the amount of MIL-101(Fe) nanocrystals loaded with natural plant essential oils is 3wt%.

[0028] Preferably, the spinning parameters in step four are as follows: the voltage of the electrospinning machine is set to 15-22kV, the solution feed rate is 0.3mL / h, the receiving distance is 10cm, the temperature is 25℃, and the relative humidity is 50%.

[0029] Preferably, the vacuum drying temperature in step four is 35°C and the time is 24 hours.

[0030] The food nanofiber membrane prepared based on this invention is used for antibacterial and preservation purposes of food.

[0031] The present invention has the following beneficial effects:

[0032] (1) By encapsulating volatile natural plant essential oils with metal-organic framework material MIL-101(Fe), compared with traditional films, the residence time of antibacterial substances in the top space of the packaging film is extended, the utilization rate of essential oils is improved, and a long-lasting antibacterial effect can be achieved.

[0033] (2) The specific surface area of ​​the MIL-101(Fe) metal-organic framework material used in this invention is 2865 m². 2 / g, which can greatly improve the encapsulation rate and sustained-release effect of plant essential oils. Moreover, compared with the casting method, the film prepared by the electrospinning method used in this invention has a larger specific surface area, which is beneficial to improving the encapsulation rate of plant essential oils.

[0034] (3) The sustained-release long-acting antibacterial film prepared by the present invention has good mechanical strength, transparency, barrier properties and degradability, is green and safe, and has a simple preparation method, is easy to promote and apply, and has a very broad application prospect. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the electrospinning technology device used in the method of the present invention.

[0036] Figure 2 is a scanning electron microscope image of the antibacterial nanofiber membrane in the method of the present invention.

[0037] Figure 3 shows the release curve of cinnamon essential oil in the antibacterial fiber membrane prepared by the method of the present invention.

[0038] Figure 4 shows the determination of pH (a), total bacterial count (b), and TVB-N (c) of pork by antibacterial fiber membranes with different OEO@MIL-101(Fe) addition amounts in the method of the present invention. Detailed Implementation

[0039] In the preparation method of the food nanofiber membrane with sustained-release antibacterial activity of the present invention, the metal-organic framework material is MIL-101(Fe) loaded with natural plant essential oils. The natural plant essential oils are one or more of the following: mustard oil, oregano oil, cinnamon oil, clove oil, garlic oil, thyme oil, lemongrass oil, bergamot oil, lemon oil, tea tree oil, rosemary oil, peppermint oil, chamomile oil, lime oil, lemongrass oil, wormwood oil, artemisia oil, and rose oil. The film-forming substrate is selected from polylactic acid (PLA) and polycaprolactone (PCL).

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0043] The specification and embodiments of this invention are merely exemplary.

[0044] pH determination of meat: GB / T 9695.5-2008 pH determination of meat and meat products.

[0045] Example 1:

[0046] Step 1: Preparation of MIL-101(Fe);

[0047] (1) Dissolve 2.703 g FeCl3·6H2O (10 mmol) in 60 mL of N,N-dimethylformamide (DMF) solution, add 1 mL of acetic acid, and then dissolve 0.830 g terephthalic acid (H2BDC, 5 mmol) in the above mixed solution. Sonicate for 30 min. Transfer the solution to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and heat continuously at 130 °C for 24 h to obtain a brick-red suspension.

[0048] (2) The sample was separated by centrifugation at 8000 rpm for 10 min to obtain a brick-red precipitate. It was then washed three times with DMF and methanol respectively to remove unreacted raw materials and DMF. Finally, the obtained solid was dried in an oven at 120℃ overnight to obtain MIL-101(Fe);

[0049] Analysis shows that the specific surface area of ​​the MIL-101(Fe) metal-organic framework material used in this invention is 2865 m². 2 / g, analysis method reference: Gecgel et al. (Gecgel C, Simsek BU, Gozmen B, et al. Comparison of MIL-101(Fe) and amine-functionalized MIL-101(Fe) as photocatalysts for the removal of imidacloprid in aqueous solution [J]. Journal of the Iranian Chemical Society, 2019, 16(8)).

[0050] Step 2: Preparation of MIL-101(Fe) nanocrystals loaded with cinnamon essential oil (OEO);

[0051] Weigh 5g of MIL-101(Fe) crystals and immerse them in a dichloromethane (DCM) solution containing 100mg / mL cinnamon essential oil. Place the solution in a sealed glass bottle and stir overnight. Stirring will embed the cinnamon essential oil into the pores of MIL-101(Fe) to obtain a MIL-101(Fe) solution loaded with cinnamon essential oil.

[0052] The obtained MIL-101(Fe) solution loaded with cinnamon essential oil was then centrifuged at 8000 rpm for 10 min. The centrifuged precipitate was collected and added to DCM, and centrifuged at 8000 rpm for 10 min. This washing process was repeated 3 times. The remaining solvent was evaporated overnight in a fume hood to obtain MIL-101(Fe) nanocrystals loaded with cinnamon essential oil, denoted as OEO@MIL-101(Fe) nanocrystals.

[0053] Comparison: The operation is the same as in step two, except that 5g of MIL-101(Fe) nanocrystals are immersed in a dichloromethane solution that does not contain cinnamon essential oil; the final product is denoted as MIL-101(Fe) nanocrystals.

[0054] Step 3: Preparation of electrospinning solution

[0055] PLA and PCL were added sequentially to a mixed solvent of DCM and DMF, and stirred evenly at room temperature to obtain a mixed solution; wherein the mass ratio of PLA to PCL was 3:7; the volume ratio of DCM to DMF was 5:1; then the MIL-101(Fe) nanocrystals loaded with natural plant essential oils prepared in step two were added, and stirring was continued for 24 hours to obtain an electrospinning solution (degassed ultrasonically for 10 minutes before use), denoted as PLA-PCL-3; in the obtained electrospinning solution, the total amount of PLA and PCL was 8wt%, the total amount of DCM and DMF was 89wt%, and the amount of MIL-101(Fe) nanocrystals loaded with natural plant essential oils was 3wt%.

[0056] Following the same procedure as in step three, adjust the ratio of DCM to DMF to 91 wt% and the ratio of OEO@MIL-101(Fe) nanocrystals to 1 wt%. The resulting electrospinning solution is denoted as PLA-PCL-1.

[0057] Following the same procedure as in step three, adjust the ratio of DCM to DMF to 87wt% and the ratio of OEO@MIL-101(Fe) nanocrystals to 5wt%. The resulting electrospinning solution is denoted as PLA-PCL-5.

[0058] The operation is the same as in step three, except that OEO@MIL-101(Fe) nanocrystals are replaced with MIL-101(Fe) nanocrystals. The corresponding electrospinning solution is denoted as PLA-PCL-m.

[0059] Step 4: Preparation of food-grade nanofiber membranes by electrospinning;

[0060] The electrospinning machine was set to 16kV, with a solution feed rate of 0.3mL / h and a receiving distance of 10cm. A layer of tin foil was placed on a metal plate as a collection substrate, and the solution was collected via a rotating drum at a temperature of 25℃ and a relative humidity of 50%. The machine was allowed to run stably for 12 hours. The fiber membrane was then peeled off from the aluminum foil and vacuum-dried at 35℃ for 24 hours to obtain a food-grade nanofiber membrane.

[0061] First, take 100 μL of pure cinnamon essential oil solution and dilute it to 10 mL with 10% citric acid ethanol solution. Then, take another 100 μL of the diluted solution and dilute it to 10 mL. Repeat this process with 100, 200, 400, 600, 800, and 1000 μL of the diluted solution, respectively, to 10 mL. Use a UV spectrophotometer to scan the concentration gradient solutions across the entire wavelength range. The maximum absorption wavelength was found to be λ = 278 nm. Record the corresponding maximum absorbance values ​​and plot a standard curve for the cinnamon essential oil content in the 10% citric acid ethanol solution. Based on the OEO standard curve (Y = 0.0132X + 0.0787, R...),... 2=0.9992), it was found that the MIL-101(Fe) prepared in step two of the example encapsulated 58.91% OEO.

[0062] The prepared food nanofiber membrane was placed in a dry iodine flask, and the cinnamon essential oil content in the sample was determined every 1, 2, 3, 4, 5, 6, and 7 days according to the above method. The release rate was calculated using the formula [Release Rate % = (1 - Total amount of cinnamon essential oil measured at each interval (g) / Original measured cinnamon essential oil content (g)) × 100%], and the average value was taken after three repetitions. Finally, a cinnamon essential oil release curve was plotted.

[0063] The results are shown in Figure 3. The comparative analysis of the results shows that the cinnamon essential oil in the PLA-PCL-5 composite membrane was completely released by day 6, while PLA-PCL-1 and PLA-PCL-3 were completely released by day 7, exhibiting a longer-lasting release effect. Among them, PLA-PCL-3 had a higher essential oil release rate in the later stage of composite membrane storage. In summary, the PLA-PCL-3 composite membrane can efficiently control the release of cinnamon essential oil, improve the utilization rate of essential oil, and extend the antibacterial preservation time.

[0064] Experiments on the use of food-grade nanofiber membranes for pork preservation:

[0065] Under sterile conditions, after removing excess fat, select fresh pork with uniform appearance and excellent texture, and evenly divide it into small pieces of approximately 40g each. One 40g piece of fresh pork is placed in a food-grade polyethylene (PE) resealable bag as the control group. Another 40g piece of pork is wrapped in a 1.0g film and placed in a PE resealable bag as the experimental group. The treated pork is refrigerated at 4℃. Every other day from day 0 to 10, the pork samples are taken out and their pH value, total bacterial count, and TVB-N and other physicochemical indicators are measured.

[0066] Figure 4 shows the determination of pH value (a), total bacterial count (b), and TVB-N (c) of meat by the prepared food nanofiber membrane.

[0067] As shown in Figure 4(a), the initial pH value of fresh pork was 5.73±0.08. After one week of storage in a refrigerator at 4℃, the pH values ​​of the PLA-PCL-m fiber membrane were 7.33±0.03, the PLA-PCL-1 fiber membrane was 7.06±0.05, the PLA-PCL-3 fiber membrane was 6.53±0.04, and the PLA-PCL-5 fiber membrane was 7.03±0.06.

[0068] As shown in Figure 4(b), the initial bacterial count of fresh pork was 5.31±0.10. After one week of storage in a refrigerator at 4℃, the bacterial count of PLA-PCL-m fiber membrane was 8.68±0.12, the bacterial count of PLA-PCL-1 antibacterial fiber membrane was 7.33±0.15, the bacterial count of PLA-PCL-3 antibacterial fiber membrane was 6.94±0.07, and the bacterial count of PLA-PCL-5 antibacterial fiber membrane was 7.016±0.19.

[0069] As shown in Figure 4(c), the initial TVB-N value of fresh pork was 7.08±0.13. After one week of storage at 4℃, the TVB-N value of PLA-PCL-m fiber membrane reached 19.03±0.20 on the 4th day, the TVB-N value of PLA-PCL-1 fiber membrane was 16.63±0.13 on the 5th day, the TVB-N value of PLA-PCL-3 fiber membrane reached 18.71±0.25 on the 7th day, and the TVB-N value of PLA-PCL-5 fiber membrane reached 18.09±0.15 on the 6th day (according to national standards, when the TVB-N value of meat products reaches 15mg / 100g, it indicates that the meat has spoiled).

[0070] In summary, it is evident that, compared with the control group PLA-PCL-m, the nanofiber membrane loaded with OEO@MIL-101(Fe) exhibits stronger antibacterial activity, and the fiber membrane loaded with 3wt% OEO@MIL-101(Fe) (PLA-PCL-3) has a longer-lasting preservation performance, significantly improving the storage period of pork.

[0071] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a food nanofiber membrane, characterized in that, Includes the following steps: Step 1: Preparation of MIL-101(Fe); (1) Dissolve FeCl3·6H2O in N,N-dimethylformamide, add acetic acid, and then add terephthalic acid. After ultrasonic treatment, a mixed solution is obtained. The solution is then transferred to a high-pressure reactor lined with polytetrafluoroethylene for reaction. After the reaction, a brick-red suspension is obtained. (2) Centrifuge the brick-red suspension obtained in step (1) to obtain a brick-red precipitate; then wash with DMF and methanol respectively, centrifuge the collected precipitate again after washing, and finally dry it to obtain the product MIL-101(Fe). Step 2: Preparation of MIL-101(Fe) nanocrystals loaded with natural plant essential oils; (1) First, add natural plant essential oils to dichloromethane to form a mixed solution; then immerse the MIL-101(Fe) obtained in step one into the mixed solution and place it in a sealed glass bottle and stir overnight to obtain a MIL-101(Fe) solution loaded with natural plant essential oils. (2) After centrifuging the MIL-101(Fe) solution loaded with natural plant essential oil obtained in step (1), collect the precipitate, disperse it in DCM for centrifugation and washing, repeat the washing several times, collect the washed precipitate and evaporate it overnight in a fume hood to obtain MIL-101(Fe) nanocrystals loaded with natural plant essential oil. Step 3: Preparation of electrospinning solution PLA and PCL were added sequentially to a mixed solvent of DCM and DMF, and stirred evenly at room temperature to obtain a mixed solution; then the MIL-101(Fe) nanocrystals loaded with natural plant essential oils prepared in step two were added, and the mixture was stirred for a period of time to obtain an electrospinning solution. Step 4: Preparation of sustained-release antibacterial nanofiber packaging film by electrospinning; The electrospinning solution prepared in step three is spun using electrospinning technology. First, the above-mentioned spinning solution is injected into a syringe. Then, the corresponding parameters are set for spinning. Tin foil is used as the receiving substrate and collected by a rotating drum. Finally, the fiber membrane on the aluminum foil is peeled off and dried under vacuum to obtain a food nanofiber membrane.

2. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step one (1), the ratio of FeCl3·6H2O, N,N-dimethylformamide, acetic acid and terephthalic acid is 2.703g:60mL:1mL:0.830g, wherein the molar ratio of FeCl3·6H2O to terephthalic acid is 2:

1.

3. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, The ultrasonic treatment time in step (1) is 30 min; the reaction temperature in the high-pressure reactor is 120℃ and the time is 24 h.

4. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, The centrifugation conditions in step (2) are: centrifugation at 8000 rpm for 10 min; the drying treatment temperature is 100-120℃ and the time is 10-12 h.

5. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step two (1), the natural plant essential oils include one or more of the following: mustard oil, oregano oil, cinnamon oil, clove oil, garlic oil, thyme oil, lemongrass oil, bergamot oil, lemon oil, tea tree oil, rosemary oil, peppermint oil, chamomile oil, lime oil, lemongrass oil, citronella oil, bulrush oil, and rose oil; the concentration of the natural plant essential oils in the mixed solution is 100 mg / mL.

6. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step two (2), the centrifugation conditions are: centrifugation at 8000 rpm for 10 min.

7. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step three, the mass ratio of PLA to PCL is 3:7; the volume ratio of DCM to DMF is 5:1; in the obtained electrospinning solution, the total amount of PLA and PCL is 8wt%, the total amount of DCM and DMF is 89wt%, and the amount of MIL-101(Fe) nanocrystals loaded with natural plant essential oils is 3wt%.

8. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step four, the spinning solution is ultrasonically degassed for 10 minutes before spinning. The spinning parameters are as follows: the voltage of the electrospinning machine is set to 15-22kV, the solution feed rate is 0.3mL / h, the receiving distance is 10cm, the temperature is 25℃, and the relative humidity is 50%.

9. The method for preparing a food nanofiber membrane according to claim 1, characterized in that, In step four, the vacuum drying temperature is 35℃ and the time is 24 hours.

10. The food nanofiber membrane prepared by any one of claims 1-9 is used for antibacterial and preservation purposes of food.

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