Fruit and vegetable postharvest storage and transportation fresh-keeping method based on nano bacteriostatic agent

Abstract

The invention relates to the technical field of fresh keeping, and particularly discloses a fruit and vegetable postharvest storage and transportation fresh keeping method based on a nano bacteriostatic agent, which comprises the following steps: cleaning and bacteria reducing: cleaning and bacteria reducing fruits and vegetables by adopting the nano bacteriostatic agent, then airing in an environment of 10-15 DEG C, and packaging the fruits and vegetables by adopting a modified atmosphere bag, then refrigerating and applying an external magnetic field in the process; a'biological + physical fresh-keeping 'technology of'nano bacteriostasis + modified atmosphere packaging + magnetic field' after fruit and vegetable picking is established, a nano bacteriostatic agent is used for modifying soybean protein, and a metal organic framework with high porosity and nanoscale and plant essential oil are fused in the nano bacteriostatic agent, so that the fruit and vegetable fresh-keeping agent has the advantages of no residue, long fresh-keeping time and the like; the method is high in preservation performance and capable of adsorbing pesticide residues, and has a wide application prospect in the field of fruit and vegetable preservation.

Description

Technical Field

[0001] The invention relates to the technical field of fresh-keeping, and in particular to a method for storing and preserving fruits and vegetables after harvest based on a nano-antibacterial agent. Background Art

[0002] Fruits and vegetables are rich in vitamins and dietary fiber, and are an important food source for promoting human health.

[0003] After harvesting, fruits and vegetables have physiological problems such as respiration, ethylene release, water evaporation, changes in nutrients, and pathological problems such as fungal diseases, bacterial diseases, and physiological disorders. In order to extend the storage life of fruits and vegetables and maintain their quality, it is necessary to take corresponding measures to prevent and control these problems. Therefore, the storage and preservation of fruits and vegetables after harvest is a systematic project that requires the use of multiple technologies to achieve the best results.

[0004] Chemical fungicides such as prochloraz and carbendazim are currently the most common methods for post-harvest pathology prevention and control of fruits and vegetables. They are effective and low-cost, but there are food safety issues such as drug residues and drug resistance. The development and application of new, green antibacterial agents has huge product demand, and plant essential oils are one of the research hotspots. However, the shortcomings of chemical instability, odor, low solubility, and direct use have a negative impact on food sensory organs, which limits its industrial application. How to solve the problem of poor dispersibility of plant essential oils and achieve the effect of antibacterial enhancement and realize the potential of replacing chemical fungicides is an existing technical problem.

[0005] Spontaneous modified atmosphere packaging is a fresh-keeping packaging technology that uses the respiration of fruits and vegetables and the selective permeability of packaging films to achieve gas exchange, ultimately forming a low O2 and high CO2 controlled atmosphere equilibrium concentration in the package, thereby reducing the respiration of fruits and vegetables and reducing water loss. In industrial applications, it is necessary to select packaging films that match the physiological characteristics of the packaged fruits and vegetables to avoid the side effects of too low O2 and too high CO2 on fruits and vegetables.

[0006] Magnetic field is a new type of physical preservation technology. It generates magnetic field biological effects by applying an external magnetic field under refrigeration conditions to compensate for the deterioration of food quality after low-temperature storage. Compared with single refrigeration technology, magnetic field can further inhibit or increase enzyme activity, reduce the number of microorganisms, and reduce the rate of biochemical reactions inside food, thereby delaying food spoilage. However, in actual applications, single magnetic field preservation is difficult to control the occurrence of post-harvest decay of fruits and vegetables, and needs to be used in conjunction with other technologies. Summary of the invention

[0007] In view of the above problems, the object of the present invention is to provide a method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent.

[0008] The technical contents of the present invention are as follows:

[0009] The present invention provides a method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent, comprising the following steps:

[0010] Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize fruits and vegetables, and then dry them in an environment of 10-15℃;

[0011] The cleaning and sterilization technology comprises the following steps:

[0012] S1: Soak fruits and vegetables in pre-cooled nano antibacterial agent for 3-6 minutes;

[0013] S2: Dry the soaked fruits and vegetables in an environment of 10-15℃;

[0014] The preparation method of the nano antibacterial agent comprises the following steps: mixing a metal organic framework and a fibrous modified soybean protein solution at a mass ratio of 0.5-3:100 to obtain a mixed solution, performing a fusion treatment, and then mixing with plant essential oils, and performing a high pressure homogenization treatment and a reduced pressure distillation to remove ethanol to obtain the mixed solution; the metal organic framework comprises one of Uio-66 and MIL-100;

[0015] The plant essential oil is one of cinnamaldehyde and thymol, and the added amount is 10-50:100 in mass ratio with soybean protein;

[0016] The soy protein fiberization modification method comprises dispersing 0.5-5wt% of soy protein in a modifier, heating at 85°C for 10-20h, and cooling to room temperature after reaction to obtain;

[0017] The modifier is a phosphate buffer solution with a mass concentration of 50 mM and dopamine containing 20-30 wt% of protein and 60 vol% ethanol solution;

[0018] The hydrophilic group content of the polypeptide chain of the modified soybean protein after fiberization is increased and has antibacterial properties, which improves water solubility. The fatty amino acids contained in the modified soybean protein can be complexed with pesticides for removal;

[0019] The high pressure homogenization treatment is carried out at a pressure of 200-400 MPa for 8-14 min;

[0020] The fusion treatment is to subject the mixed solution to ultrasonic short-cutting by subjecting it to ultrasonic treatment at a frequency of 25 to 100 kHz for 6 to 20 minutes;

[0021] The fusion treatment can promote the uniform modification of the metal organic framework to the modified soybean protein, and increase the spatial sites by regulating the condensation state through physical and energy, thereby increasing the load stability performance;

[0022] Step 2): Fresh-keeping packaging: Pack the fruits and vegetables in step 1) in a self-regulating atmosphere bag;

[0023] The fresh-keeping packaging selects spontaneous atmosphere bags with different gas permeability ranges according to fruits and vegetables with different respiration intensities; for fruits and vegetables with high respiration intensities such as Chinese cabbage, banana, passion fruit, and lychee, a packaging film with a higher gas permeability should be selected; for fruits and vegetables with medium respiration intensities such as macaroni, Shanghai green, and winter jujube, a packaging film with a moderate gas permeability should be selected; for fruits and vegetables with low respiration intensities such as apples, citrus, and root vegetables, a packaging film with a lower gas permeability should be selected;

[0024] The gas permeability range of the spontaneous atmosphere fresh-keeping bag is such that the higher gas permeability refers to the O2 permeability of 8000-10000cm 3 / m 2 ·24h·0.1Mpa, CO2 permeability is 4000~5000cm3 / m 2 ·24h·0.1Mpa; Moderate gas permeability means that the O2 permeability is 5000~8000cm 3 / m 2 ·24h·0.1Mpa, CO2 permeability is 2500~4000cm 3 / m 2 ·24h·0.1Mpa; Low gas permeability means O2 permeability is less than 5000cm 3 / m 2 ·24h·0.1Mpa, CO2 permeability is <2500cm 3 / m 2 24h 0.1Mpa;

[0025] 10-15 mL of 0.1-2.0 wt% sodium hydroxymethyl cellulose aqueous solution is sprayed into the fresh-keeping package and dried; it can absorb the moisture produced by the respiration of fruits and vegetables, and has an antibacterial effect, thereby increasing the fresh-keeping and antibacterial properties of the modified atmosphere fresh-keeping bag;

[0026] Step 3): Magnetic field refrigeration: refrigerate the fruits and vegetables in step 2), and apply an external magnetic field during the refrigeration process;

[0027] The external magnetic field refrigeration refers to installing electromagnetic field equipment in the cold storage, first using a magnetic field with an intensity of 0.1-0.5mT for 3-6h, and then using a treatment with an intensity of 2-10mT;

[0028] The refrigerated temperature is 0-15°C;

[0029] The magnetic field refrigeration first uses a low-intensity magnetic field for treatment to reduce the degradation of chlorophyll and inhibit molecular diffusion, enrich charged ions in cells, and increase phenolic substances. It then uses a high-intensity magnetic field for treatment to further inhibit cell metabolic activities and improve antioxidant capacity, which can effectively prevent browning and corruption and reduce freezing damage.

[0030] Beneficial effects: (1) The present invention constructs a type of nano-biostatic agent through food processing technology, modifies soybean protein and integrates a highly porous, nano-scale metal organic framework into it. The nano-size is uniform and highly dispersible. It is applied to the post-harvest cleaning of fruits and vegetables, which can replace traditional chemical fungicides and achieve the dual effects of reducing bacteria, preserving freshness and removing pesticide residues, and has the advantages of being green and safe.

[0031] (2) The present invention establishes a post-harvest "biological + physical preservation" technology for fruits and vegetables of "nano-antibacterial + modified atmosphere packaging + magnetic field". The technology involves multiple aspects such as pathological prevention and control, physiological regulation, and quality maintenance. It has the advantages of no residue and long preservation period, and has broad application prospects in the field of fruit and vegetable preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the "nano-antibacterial + modified atmosphere packaging + magnetic field" preservation technology;

[0033] Figure 2 This is the effect of "nano-antibacterial + modified atmosphere packaging + magnetic field" on the preservation of litchi after 20 days. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below through specific implementation cases. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0035] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0036] Example 1

[0037] A method for preserving fruits and vegetables after harvest based on nano-antibacterial agents, the working process is as follows Figure 1 As shown, the following steps are included:

[0038] Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize litchi, and then dry it in an environment of 13°C;

[0039] The cleaning and sterilization technology comprises the following steps:

[0040] S1: litchi is soaked in pre-cooled nano antibacterial agent for 5 minutes;

[0041] S2: After soaking, the litchi was dried in an environment of 13°C;

[0042] The preparation method of the nano antibacterial agent is as follows: Uio-66 and a fibrous modified soybean protein solution are mixed at a mass ratio of 2:100 to obtain a mixed solution, ultrasonic short-cutting is performed for fusion treatment using a 65kHz frequency ultrasonic wave treatment for 12 minutes, and then cinnamaldehyde is added in an amount with a mass ratio of 30:100 to soybean protein, and ethanol is removed by vacuum distillation after high-pressure homogenization treatment at a pressure of 300MPa for 12 minutes to obtain the mixed solution;

[0043] The soy protein fiber modification method comprises dispersing 1 wt% soy protein in a 50 mM phosphate buffer solution containing 25 wt% dopamine and heating at 85° C. for 15 h, and cooling to room temperature after the reaction to obtain the soy protein fiber.

[0044] Step 2): Fresh-keeping packaging: The lychees from step 1) are packaged in a spontaneous atmosphere bag with a relatively high air permeability, wherein 13 mL of a 0.5 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0045] Step 3): Magnetic field refrigeration: Refrigerate the fruits and vegetables in step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field. First, use a magnetic field with an intensity of 0.3mT for 5h, then use a treatment with an intensity of 6mT, and the refrigeration temperature is 4°C; the effect after storage for 20 days after the preservation treatment is as shown in the figure Figure 2 As shown, it can be seen that the "nano-antibacterial + modified atmosphere packaging + magnetic field" of the present invention has a lower browning degree of litchi than that of the litchi without fresh-keeping treatment, and has a significant fresh-keeping effect.

[0046] Example 2

[0047] A method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent comprises the following steps:

[0048] Step 1): Cleaning and sterilizing: Use nano antibacterial agent to clean and sterilize the winter jujube, and then dry it in an environment of 10°C;

[0049] The cleaning and sterilization technology comprises the following steps:

[0050] S1: Soak winter jujube in pre-cooled nano antibacterial agent for 3 minutes;

[0051] S2: After soaking, the winter jujubes are dried in an environment of 10°C;

[0052] The preparation method of the nano antibacterial agent comprises the following steps: mixing MIL-100 and a fibrous modified soybean protein solution at a mass ratio of 0.5:100 to obtain a mixed solution, performing ultrasonic short-cut fusion treatment using a 25kHz frequency ultrasonic wave treatment for 6 minutes, and then mixing and adding thymol at a mass ratio of 10:100 to soybean protein, performing high-pressure homogenization treatment at a pressure of 200MPa for 8 minutes, and then performing reduced pressure distillation to remove ethanol to obtain the nano antibacterial agent;

[0053] The soy protein fiber modification method comprises dispersing 0.5 wt% soy protein in a phosphate buffer solution with a mass concentration of 50 mM and dopamine with a mass concentration of 20 wt% protein + 60 vol% ethanol solution, heating at 85° C. for 10 h, and cooling to room temperature after the reaction to obtain;

[0054] Step 2): Fresh-keeping packaging: The winter jujubes from step 1) are packaged in a spontaneous atmosphere bag with a medium air permeability, wherein 10 mL of a 0.3 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0055] Step 3): Magnetic field refrigeration: Refrigerate the winter jujubes in step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field. First, use a magnetic field with an intensity of 0.1mT for 3h, and then use a magnetic field with an intensity of 2mT. The refrigeration temperature is 2°C.

[0056] Example 3

[0057] A method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent comprises the following steps:

[0058] Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize apples, and then dry them in an environment of 15°C;

[0059] The cleaning and sterilization technology comprises the following steps:

[0060] S1: Apples were soaked in pre-cooled nano-antibacterial agent for 6 minutes;

[0061] S2: After soaking, the apples were dried in an environment of 15°C;

[0062] The preparation method of the nano antibacterial agent comprises the following steps: mixing MIL-100 and a fibrous modified soybean protein solution at a mass ratio of 3:100 to obtain a mixed solution, performing ultrasonic short-cut fusion treatment by using a sound wave treatment at a frequency of 100 kHz for 20 minutes, and then mixing and adding cinnamaldehyde at a mass ratio of 50:100 to soybean protein, performing high-pressure homogenization treatment at a pressure of 400 MPa for 14 minutes, and then performing reduced pressure distillation to remove ethanol to obtain the nano antibacterial agent;

[0063] The soy protein fiber modification method comprises dispersing 5 wt% soy protein in a 50 mM phosphate buffer solution containing 30 wt% dopamine and heating at 85° C. for 20 h, and cooling to room temperature after the reaction to obtain the soy protein fiber.

[0064] Step 2): Fresh-keeping packaging: The apples from step 1) are packaged in a self-regulating atmosphere bag with a relatively low air permeability, wherein 15 mL of a 1.0 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0065] Step 3): Magnetic field refrigeration: Refrigerate the apples from step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field. First, use a magnetic field with an intensity of 0.5 mT for 6 hours, and then use a magnetic field with an intensity of 10 mT. The refrigeration temperature is 0°C.

[0066] Example 4

[0067] A method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent comprises the following steps:

[0068] Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize the citrus, and then dry it in an environment of 11°C;

[0069] The cleaning and sterilization technology comprises the following steps:

[0070] S1: Citrus fruits are soaked in pre-cooled nano-antibacterial agent for 4 minutes;

[0071] S2: After soaking, the citrus fruits were dried in an environment of 11°C;

[0072] The preparation method of the nano antibacterial agent is as follows: Uio-66 and a fibrous modified soybean protein solution are mixed at a mass ratio of 1:100 to obtain a mixed solution, ultrasonic short-cutting is performed for fusion treatment using an 80kHz frequency ultrasonic wave treatment for 10 minutes, and then cinnamaldehyde is added in an amount of 20:100 of soybean protein in a mass ratio, and ethanol is removed by vacuum distillation after high-pressure homogenization treatment at a pressure of 250MPa for 9 minutes to obtain a mixed solution;

[0073] The soy protein fiber modification method comprises dispersing 2 wt% soy protein in a 50 mM phosphate buffer solution containing 22 wt% dopamine and 60 vol% ethanol solution, heating at 85° C. for 12 h, and cooling to room temperature after reaction to obtain the soy protein fiber.

[0074] Step 2): Fresh-keeping packaging: The citrus fruits of step 1) are packaged in a self-regulating atmosphere bag with a relatively low air permeability, wherein 11 mL of a 2.0 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0075] Step 3): Magnetic field refrigeration: Refrigerate the citrus in step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field. First, use a magnetic field with an intensity of 0.2mT for 4h, and then use a magnetic field with an intensity of 4mT. The refrigeration temperature is 4°C.

[0076] Example 5

[0077] A method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent comprises the following steps:

[0078] Step 1): Cleaning and sterilizing: Use nano-antibacterial agent to clean and sterilize the passion fruit, and then dry it in an environment of 12°C;

[0079] The cleaning and sterilization technology comprises the following steps:

[0080] S1: passion fruit was soaked in pre-cooled nano antibacterial agent for 3 min;

[0081] S2: After soaking, the passion fruit was dried in an environment of 12°C;

[0082] The preparation method of the nano antibacterial agent comprises the following steps: mixing MIL-100 and a fibrous modified soybean protein solution at a mass ratio of 0.5:100 to obtain a mixed solution, performing ultrasonic short-cut fusion treatment using a 90kHz frequency ultrasonic wave treatment for 15 minutes, and then mixing and adding thymol at a mass ratio of 20:100 to soybean protein, and performing high-pressure homogenization treatment at a pressure of 250MPa for 13 minutes, and then performing reduced pressure distillation to remove ethanol to obtain the nano antibacterial agent;

[0083] The soy protein fiber modification method comprises dispersing 5 wt% soy protein in a 50 mM phosphate buffer solution containing 25 wt% dopamine and heating at 85° C. for 20 h, and cooling to room temperature after the reaction to obtain the soy protein fiber.

[0084] Step 2): Fresh-keeping packaging: The passion fruit of step 1) is packaged in a spontaneous atmosphere bag with a relatively high air permeability, wherein 14 mL of a 1.5 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0085] Step 3): Magnetic field refrigeration: Refrigerate the fruits and vegetables in step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field. First, use a magnetic field with an intensity of 0.4 mT for 5 hours, and then use a magnetic field with an intensity of 8 mT. The refrigeration temperature is 10°C.

[0086] Example 6

[0087] A method for post-harvest storage and preservation of fruits and vegetables based on a nano-antibacterial agent comprises the following steps:

[0088] Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize bananas, and then dry them in an environment of 15°C;

[0089] The cleaning and sterilization technology comprises the following steps:

[0090] S1: Bananas are soaked in pre-cooled nano-antibacterial agent for 5 minutes;

[0091] S2: After soaking, the bananas were dried in an environment of 15°C;

[0092] The preparation method of the nano antibacterial agent is as follows: Uio-66 and a fibrous modified soybean protein solution are mixed at a mass ratio of 2.5:100 to obtain a mixed solution, ultrasonic short-cutting is performed for fusion treatment using a 40kHz frequency ultrasonic wave treatment for 10 minutes, and then cinnamaldehyde is added in an amount of 30:100 to soybean protein by mass ratio, and cinnamaldehyde is added at a high pressure homogenization treatment at a pressure of 200MPa for 10 minutes, and then ethanol is removed by reduced pressure distillation to obtain the nano antibacterial agent;

[0093] The soy protein fiber modification method comprises dispersing soy protein with a mass concentration of 4 wt% in a phosphate buffer solution with a mass concentration of 50 mM and dopamine with a mass concentration of 30 wt% of protein + 60 vol% ethanol solution, heating at 85° C. for 10 h, and cooling to room temperature after the reaction to obtain;

[0094] Step 2): Fresh-keeping packaging: The bananas from step 1) are packaged in a spontaneous atmosphere bag with a relatively high permeability, wherein 15 mL of a 0.8 wt % sodium hydroxymethylcellulose aqueous solution is sprayed and dried;

[0095] Step 3): Magnetic field refrigeration: Refrigerate the bananas from step 2), and add an electromagnetic field during the refrigeration process to apply an external magnetic field, first use a magnetic field with an intensity of 0.1 mT for 6 hours, then use a magnetic field with an intensity of 5 mT, and the refrigeration temperature is 15°C.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is that the soybean protein is not modified in Comparative Example 1, and the other properties remain unchanged.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 1 is that the nano antibacterial agent of Comparative Example 2 is prepared by mixing equal amounts of Uio-66, fiberized modified soybean protein solution and plant essential oil, and then high-pressure homogenization treatment is performed at a pressure of 300 MPa for 12 minutes and then reduced pressure distillation is performed to remove ethanol; the rest remains unchanged.

[0100] Comparative Example 3

[0101] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not use an external magnetic field for treatment, and the other conditions remain unchanged.

[0102] In order to detect the removal effect of nano-antibacterial agents on common pesticides, a small amount of pesticides such as prochloraz, chlorpyrifos, carbendazim, etc. were sprayed on litchi fruits, and then treated according to the embodiments and comparative examples. After refrigeration for 15 days, the content of pesticide residues on the surface of litchi was detected according to standard methods (GB / T 20769, GB23200.8, NY / T1456, NY / T1453, etc.). The test results are shown in Table 1.

[0103] Table 1 Pesticide residues on litchi surface (mg / kg)

[0104]

[0105]

[0106] As can be seen from Table 1, the post-harvest storage and preservation method for fruits and vegetables of the present invention has low pesticide residues in the fruits and vegetables after treatment, which meets the ideal pesticide residue removal standard.

[0107] The preservation methods of the embodiment and the comparative example were applied to the storage and preservation of litchi. The physical and chemical indicators of the litchi were tested after 30 days of storage. The results are shown in Table 2.

[0108] Table 2 Weight loss rate and decay rate of litchi

[0109]

[0110] As can be seen from Table 2, the post-harvest storage and transportation preservation method of fruits and vegetables of the present invention has a good preservation effect.

[0111] In summary, the fruits and vegetables of the present invention adopt the "nano antibacterial + modified atmosphere packaging + magnetic field" post-harvest storage and preservation method, which can preserve freshness through multiple functions such as antibacterial, respiration inhibition and enzyme activity regulation. Among them, the water solubility, antibacterial property and adsorption property can be increased by fusing the modified soybean protein with the metal organic framework and then mixing with the nano plant essential oil. The ultrasonic fusion technology is used to promote the uniform formation of nano channels in the microstructure, thereby improving the loading efficiency and release efficiency of the antibacterial components. The physiological activity level of fruit and vegetable cells is regulated under the external magnetic field to further maintain the freshness of the fruits and vegetables.

Claims

1. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents, characterized in that: The following steps are involved: Step 1): Cleaning and sterilization: Use nano-antibacterial agent to clean and sterilize fruits and vegetables, and then dry them in an environment of 10-15℃; Step 2): Fresh-keeping packaging: Pack the fruits and vegetables in step 1) in a self-regulating atmosphere bag; Step 3): Magnetic field refrigeration: Refrigerate the fruits and vegetables in step 2), and apply an external magnetic field during the refrigeration process.

2. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 1, characterized in that: Step 1) The cleaning and sterilization technology comprises the following steps: S1: Soak fruits and vegetables in pre-cooled nano antibacterial agent for 3-6 minutes; S2: After soaking, dry the fruits and vegetables in an environment of 10-15℃.

3. The method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 1, characterized in that: The preparation method of the nano antibacterial agent comprises the following steps: mixing a metal organic framework and a fiberized modified soybean protein solution at a mass ratio of 0.5-3:100 to obtain a mixed solution, performing a fusion treatment, and then mixing plant essential oil, and performing a high-pressure homogenization treatment and a reduced-pressure distillation to remove ethanol to obtain the mixed solution; the plant essential oil is one of cinnamaldehyde and thymol, and the addition amount is 10-50:100 with respect to the soybean protein; the metal organic framework comprises one of Uio-66 and MIL-100.

4. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 3, characterized in that: The soybean protein fiber modification method comprises dispersing soybean protein with a mass concentration of 0.5-5wt% in a modifier, heating at 85°C for 10-20h, and cooling to room temperature after reaction to obtain the soybean protein.

5. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 4, characterized in that: The modifier is a phosphate buffer solution with a mass concentration of 50 mM and containing 20-30 wt% of protein and dopamine + 60 vol% ethanol solution.

6. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 3, characterized in that: The high pressure homogenization treatment is carried out at a pressure of 200-400 MPa for 8-14 min.

7. A method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 3, characterized in that: The fusion treatment is to subject the mixed solution to ultrasonic short-cutting by subjecting it to ultrasonic treatment at a frequency of 25 to 100 kHz for 6 to 20 minutes.

8. The method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 1, characterized in that: Step 3) The magnetic field refrigeration refers to installing electromagnetic field equipment in the cold storage, first using a magnetic field treatment with an intensity of 0.1-0.5mT for 3-6h, then using a treatment with an intensity of 2-10mT, and the refrigeration temperature is 0-15°C.

9. The method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 1, characterized in that: Step 2) Spray 10-15 mL of 0.1-2.0 wt % sodium hydroxymethyl cellulose aqueous solution into the fresh-keeping package and dry it.

10. The method for post-harvest storage and preservation of fruits and vegetables based on nano-antibacterial agents according to claim 1, characterized in that: Step 2) The fresh-keeping packaging is performed by selecting spontaneous atmosphere bags with different gas permeability ranges according to the fruits and vegetables with different respiration intensities.

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