Bacteriostatic agent as well as preparation method and application thereof

Abstract

The invention provides a bacteriostatic agent as well as a preparation method and application thereof, and relates to the technical field of bacteriostasis and preservation. The preparation method comprises the following steps: 1) adding chitosan into an acetic acid aqueous solution, and stirring to obtain a chitosan solution; 2) adding glycerol into the chitosan solution, and uniformly stirring to obtain a mixed solution A; 3) dissolving borneol essential oil in ethanol to obtain a borneol essential oil alcoholic solution; (4) dropwise adding the borneol essential oil alcoholic solution into the mixed solution A, and stirring to obtain a mixed solution B, and (5) adding tween-80 and clathrate 1-methylcyclopropene into the mixed solution B, and uniformly mixing to obtain the bacteriostatic agent. The bacteriostatic agent prepared by the preparation method has the characteristics of low cost, environmental protection, efficient bacteriostasis and the like, and can be used for fresh keeping of vegetables and fruits.

Description

Technical Field

[0001] The invention belongs to the technical field of antibacterial and fresh-keeping, and specifically relates to an antibacterial agent and a preparation method and application thereof. Background Art

[0002] Fresh fruits and vegetables are rich in vitamins, amino acids, cellulose, carbohydrates and other nutrients, and are an important part of a balanced and healthy diet. After picking, fruits and vegetables lose water, soften and lose nutrients due to enhanced respiration, vigorous metabolism and increased ethylene release. Fruits and vegetables have poor protective tissues and are easily damaged by mechanical damage and microbial infection. The water and nutrients in fruits and vegetables provide a suitable living environment for microorganisms such as pathogens and molds. The large-scale growth and reproduction of microorganisms causes fruits and vegetables to rot and deteriorate.

[0003] Traditional antibacterial preservation technology has the disadvantages of high material cost, great environmental pollution, and serious chemical residues. For example: 1) Low temperature preservation, which slows down the physiological and biochemical reactions of fruits and vegetables and the growth rate of microorganisms through low temperature, is the most widely used preservation technology, but it has high requirements for temperature control equipment and is still not applicable for long-distance transportation due to the constraints of cold chain transportation costs; 2) Controlled atmosphere preservation, which inhibits respiration and metabolism by regulating the gas components in the storage and transportation packaging, but this technology has high requirements for packaging materials; 3) Irradiation preservation, which interferes with the basic metabolism of fruits and vegetables through ionizing radiation and kills pathogens, and needs to be combined with other storage technologies for long-term preservation; 4) Chemical preservation, which extends the storage and transportation period through disinfectants, but its chemical drug residues will endanger human health. Therefore, the development of low-cost, safe and effective antibacterial preservation technology is an urgent problem to be solved in the storage and transportation process of fruits and vegetables.

[0004] Chinese invention patent CN106561799B discloses a method for preparing a special moisturizing and efficient biological preservative for fruit and vegetable shelves, including the preparation of moisturizing agent A and the preparation of preservative B. One bag of moisturizing agent A and one bag of preservative B are vacuum-packed in polyethylene packaging bags to obtain the moisturizing biological preservative. The packaging design of using two bags to separate moisture and freshness has the disadvantages of high material cost and great environmental pollution; China Invention Patent Publication No. CN105211274A discloses a fruit and vegetable antibacterial preservative and its preparation method, which includes the following raw materials by weight of the preservative: 20-30 parts of chitosan, 10-15 parts of medical stone, 3-5 parts of glutamic acid, 20-30 parts of acetic acid solution, 25-30 parts of β-cyclodextrin, 8-10 parts of clove oil, 5-10 parts of phosphate ester, 3-8 parts of glycerol, 15-20 parts of citric acid, 8-15 parts of ethylene absorbent, 3-8 parts of deer hoof grass extract, 5-10 parts of honeysuckle extract, 3-5 parts of rhubarb extract, 2-4 parts of astragalus extract, 10-15 parts of galangal extract, and 30-50 parts of sterile water. However, the antibacterial preservative has complex ingredients and its effect needs to be further improved.

[0005] There is an urgent need to develop a method for preparing an antibacterial agent that is low-cost, green, environmentally friendly, naturally safe, and highly effective in inhibiting bacteria. Summary of the invention

[0006] In view of the shortcomings of the above-mentioned traditional technologies, the present invention provides an antibacterial agent and a preparation method and application thereof. The preparation method of the antibacterial agent provided by the present invention combines the storage and transportation characteristics of fruits and vegetables and the planting advantages of borneol camphor in Jiaxing City, takes borneol essential oil and chitosan as the main active ingredients, can provide an antibacterial environment, inhibit the growth of microorganisms and spoilage bacteria, and achieve an antibacterial and fresh-keeping effect. The borneol essential oil can be extracted from the leaves, fruits and branches of borneol camphor, which is simple and easy to obtain.

[0007] The first aspect of the present invention relates to a method for preparing an efficient and safe antibacterial agent, the preparation method comprising the following steps: 1) Add chitosan to an acetic acid aqueous solution and stir to obtain a chitosan solution; 2) Add glycerol to the chitosan solution and stir evenly to obtain a mixed solution A; 3) dissolving borneol essential oil in ethanol to obtain borneol essential oil alcohol solution; 4) adding the borneol essential oil alcohol solution dropwise to the mixed solution A and stirring to obtain a mixed solution B; 5) Add Tween-80 and the included 1-methylcyclopropene to the mixed solution B, mix well, and obtain an antibacterial agent.

[0008] Preferably, the volume concentration of the acetic acid aqueous solution in step 1) is 2%.

[0009] Preferably, the usage ratio of the acetic acid aqueous solution, chitosan, glycerol, borneol essential oil, ethanol, Tween 80, and inclusion 1-methylcyclopropene is 1000 mL: 7-18 g: 2.3 g: 6-15 g: 15 mL: 10 mL: 1 g.

[0010] Preferably, the weight ratio of chitosan to borneol essential oil is 0.5-3.

[0011] Further preferably, the weight ratio of chitosan to borneol essential oil is 0.6-2.6, preferably 1.5.

[0012] Preferably, the chitosan has a deacetylation degree of ≥90% and a molecular weight of 300,000-600,000.

[0013] Preferably, the carrier of the included 1-methylcyclopropene is cyclodextrin, and the content of 1-methylcyclopropene in the inclusion complex is ≥4%.

[0014] The second aspect of the present invention relates to an antibacterial agent, which is prepared according to the above preparation method.

[0015] The third aspect of the present invention relates to the antibacterial agent prepared by the above preparation method or the use of the above antibacterial agent in the preparation of a product containing an antibacterial preservative for fruits and vegetables.

[0016] Preferably, the fruits and vegetables include cucumbers, tomatoes, dates, bananas or apples.

[0017] Preferably, the product containing the antibacterial preservative for fruits and vegetables includes plastic wrap, fresh-keeping bags, and packaging bags.

[0018] Preferably, the specific operation steps of the antibacterial agent in preparing the product containing the antibacterial preservative for fruits and vegetables are: coating the antibacterial agent in a polyethylene packaging bag, drying it, putting fruits and vegetables in the bag, and sealing and storing it.

[0019] The main components of borneol essential oil are monoterpenes and sesquiterpenes such as borneol, camphor, limonene, and pinene, which have antibacterial, insect repellent, and antioxidant activities. Chitosan is a natural active substance containing nitrogen-containing polysaccharides. Its specific functional groups give it good film-forming properties, allowing the antibacterial components to be evenly distributed on the surface of fruit and vegetable packaging. It is a potential application material in the field of fruit and vegetable preservation.

[0020] Compared with the prior art, the antibacterial agent prepared by the present invention uses natural borneol essential oil as the antibacterial active ingredient, is low-toxic and environmentally friendly, has simple and easily available main raw materials, can effectively inhibit various pathogens and microbial infections, and reduce the decay rate of fruits and vegetables. In addition, when using, it is not necessary to soak fruits and vegetables, avoiding direct contact between the antibacterial agent and fruits and vegetables, and improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : The finished product picture of the antibacterial agent; Figure 2 : The appearance of the antibacterial agent after being coated on the polyethylene film and dried, where the left side is the blank control polyethylene film; Figure 3 : The inhibition zone results of antibacterial agent and borneol essential oil against Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa; Figure 4 : In vitro antibacterial effects of antibacterial agents and borneol essential oil on Candida albicans; Figure 5 : In vitro antibacterial effects of antibacterial agents and borneol essential oil on Staphylococcus aureus; Figure 6 : In vitro antibacterial effects of antibacterial agents and borneol essential oil on Escherichia coli; Figure 7 : In vitro antibacterial effects of antibacterial agents and borneol essential oil on Pseudomonas aeruginosa; Figure 8:In vitro antibacterial effects of antibacterial agents and borneol essential oil on Botrytis cinerea; Fig. 9 : The antibacterial and fresh-keeping screening experiment of the blank group and preparations 1 to 3 on tomatoes in Example 3; Fig.10 : Antibacterial and fresh-keeping screening experiment of preparations 4 to 7 in Example 3 on tomatoes; Fig.11 :The effect diagram of the application of antibacterial agent in cucumber storage; Fig.12 :The effect diagram of the application of antibacterial agent in tomato storage; Fig.13 :The effect diagram of the application of antibacterial agent in banana storage; Fig.14 :The effect diagram of the application of antibacterial agent in apple storage; Fig.15 :The effect diagram of the application of antibacterial agents in the storage of jujube. DETAILED DESCRIPTION

[0022] Example 1 The chemical components of borneol essential oil were qualitatively analyzed by GC-MS. The model of the instrument and the analysis method used are shown in Table 1, and the analysis results are shown in Table 2.

[0023] Table 1: GC-MS analysis methods

[0024] Table 2: GC-MS qualitative analysis results of borneol essential oil

[0025] GC-MS detection shows that the main components of the borneol essential oil used are monoterpenes and sesquiterpenes such as borneol, D-camphor, eucalyptol, borneol acetate, limonene, and pinene.

[0026] This example also prepares a highly effective and safe antibacterial agent, specifically: S1. Add 15.0 g of chitosan to 1.0 L of 2% acetic acid aqueous solution, stir, and obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 10.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, and mix well to obtain an antibacterial agent.

[0027] The appearance of the antibacterial agent prepared in this example is shown in Figure 1 .

[0028] The appearance of the antibacterial agent prepared in this example after being coated on a polyethylene film and dried is shown in Figure 2 .

[0029] Example 2 In this example, an efficient and safe antibacterial agent was prepared, and the preparation method was the same as that of Example 1. The antibacterial effect of the antibacterial agent on Escherichia coli, Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa and tomato gray mold pathogens was tested.

[0030] Experimental reagents: Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 43300, Candida albicans Y167, Pseudomonas aeruginosa ATCC 10104, and Botrytis cinerea were purchased from China Industrial Microbiological Culture Collection Center.

[0031] Nutrient broth (NB) medium (Hangzhou Microbiological Reagent Co., Ltd.), LB liquid medium (Hangzhou Best Biotechnology Co., Ltd.), agar (Beijing Solebold Technology Co., Ltd.), Sabouraud dextrose agar (SDA) medium (Hangzhou Best Biotechnology Co., Ltd.), potato dextrose agar (PDA) medium (Qingdao Risui Biotechnology Co., Ltd.), dimethyl sulfoxide (DMSO, Sinopharm Chemical Preparation Co., Ltd.).

[0032] Experimental equipment: SW-CJ-2FD clean bench (Suzhou Purification Equipment Co., Ltd.); THZ-82 water bath constant temperature oscillator (Shanghai Lichen Instrument Technology Co., Ltd.), constant temperature incubator (Shanghai Jinghong Experimental Equipment Co., Ltd.), TC-15 sleeve thermostat (Haining Xinhua Medical Equipment Co., Ltd.), high pressure sterilizer (Shanghai Shen'an Medical Equipment Factory), visible light spectrophotometer (Shanghai Yuanxi Instrument Co., Ltd.).

[0033] 1) In vitro antibacterial experiments on Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa Preparation of bacterial liquid: The liquid culture medium was sterilized by ultraviolet in a clean bench for 15 min. The inoculation loop was soaked in alcohol and dried with the outer flame of an alcohol lamp. After cooling, the strains of Staphylococcus aureus, Escherichia coli, Candida albicans and Pseudomonas aeruginosa, which had been taken out of a 4 ℃ refrigerator in advance, were scraped from the inclined surface of the test tube and placed in nutrient broth liquid culture medium, LB liquid culture medium and Sabouraud dextrose agar liquid culture medium, respectively, and cultured overnight in a shaking incubator.

[0034] Determination of inhibition zone: adjust the overnight bacterial suspension to a starting bacterial solution of OD600=0.03, and wait until it grows to OD600≈0.15 (equivalent to 0.5 standard McFarland units of absorbance) for use.

[0035] The drug-sensitive paper method was used to determine the effects of borneol essential oil and antibacterial agents on the growth of Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa in vitro. The bacterial solution was evenly spread on the solid culture medium, 20 μL per portion, and repeated three times. Use sterile tweezers to place drug-sensitive paper pieces with a diameter of 6 mm on each culture medium. One of the pieces was left untreated, one piece was dripped with 10 μL of borneol essential oil sample, and one piece was dripped with 10 μL of preparation sample. After the operation is completed, the culture medium plate is placed in an incubator and cultured at a constant temperature of 37°C for 16-20 h. The entire experimental process was repeated three times, and the diameter of the inhibition zone was accurately measured using a vernier caliper. The experimental results are shown in the figure. Figure 3 shown.

[0036] The drug sensitivity paper method showed that the diameter of the inhibition zone of borneol essential oil against Escherichia coli was 14.4 mm, the diameter of the inhibition zone against Staphylococcus aureus was 13.9 mm, and the diameter of the inhibition zone against Candida albicans was 13.3 mm. The diameter of the inhibition zone of the antibacterial agent against Escherichia coli was 9.7 mm, the diameter of the inhibition zone against Staphylococcus aureus was 7.4 mm, and the diameter of the inhibition zone against Candida albicans was 8.0 mm. The antibacterial effect of borneol essential oil on Pseudomonas aeruginosa was poor, and the antibacterial agent had a certain antibacterial effect on Pseudomonas aeruginosa, with an inhibition zone diameter of about 12.1 mm. The diameter of the inhibition zone of the blank control group was 6 mm.

[0037] Determination of in vitro growth inhibition: The constant broth dilution method was used to determine the in vitro inhibition rate of borneol essential oil and antibacterial agents against Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa.

[0038] Dissolve borneol essential oil and antibacterial agent in dimethyl sulfoxide (DMSO) at a ratio of 1:1 to prepare test solutions. Take the test solutions of borneol essential oil and antibacterial agent and add them to the bacterial solutions of Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa with OD600=0.03 at different concentrations. Incubate the mixed bacterial solution on a shaker (37°C, 120 rpm) for 4 h. After incubation, dilute the bacterial solution to 10-3 times the original on a sterile 96-well plate, take 5μL of the diluted bacterial solution and evenly spread it on the surface of the solid culture medium, place the culture medium plate in a 37°C constant temperature incubator and continue to culture for 16-20 h, and observe the growth of the colonies. The experimental results are as follows Figure 4 , Figure 5 , Figure 6 , Figure 7 shown.

[0039] 2) Antibacterial experiment on tomato gray mold pathogen The mycelial growth rate method was used to determine the in vitro antibacterial effects of borneol essential oil and antibacterial agents on tomato gray mold pathogens.

[0040] Prepare the PDA medium into a solution, boil it, sterilize it at 121℃ for 15 min, and put it in an oven for use. Mix the borneol essential oil solution and the antibacterial agent solution with the hot PDA medium evenly, so that the borneol essential oil concentration is 1 μL / mL, and the preparation concentrations are 5μL / mL, 10 μL / mL, and 20 μL / mL, respectively. Beat the normally growing colonies into a cake with a diameter of 3 mm, transfer it to the center of the solidified drug-containing culture medium, and culture it at a constant temperature of 27℃. When the mycelium in the control group fills the culture medium, measure the mycelium diameter of the experimental group, and calculate the inhibition rate (I%) according to the following formula: I (%)=[(CK-PT) / (CK-3)]×100% Among them, CK and PT represent the mycelial diameters of the blank control group and the experimental group, respectively, in mm. The experimental results are shown in Table 3 and Figure 8 shown.

[0041] Table 3: Inhibition rate of borneol essential oil and antibacterial agents on the in vitro growth of tomato gray mold pathogens

[0042] Embodiment 3: In this example, 7 groups of preparations were prepared, and the preparation steps were as follows: The method for preparing the essential oil-free preparation (Preparation 1) comprises the following steps: S1, adding 25.0 g chitosan to 1.0 L 2% acetic acid aqueous solution, stirring to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3. Add 15.0 mL of ethanol, 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S2, and mix well to obtain an essential oil-free preparation.

[0043] The preparation method of the chitosan-free preparation (Preparation 2) comprises the following steps: S1, take 1.0 L of 2% acetic acid aqueous solution; S2, add 2.3 g glycerol to the S1 solution and stir evenly; S3, dissolving 25.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, and mix well to obtain a chitosan-free preparation.

[0044] The preparation method of the chitosan / essential oil (20 / 5) preparation (Preparation 3) comprises the following steps: S1, adding 20.0 g chitosan to 1.0 L 2% acetic acid aqueous solution, stirring to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 5.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, mix well to obtain an antibacterial agent with an increased dosage ratio.

[0045] The preparation method of the chitosan / essential oil (18 / 7) preparation (Preparation 4) comprises the following steps: S1, adding 18.0 g chitosan to 1.0 L 2% acetic acid aqueous solution, stirring to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 7.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, mix well to obtain an antibacterial agent with a reduced dosage ratio.

[0046] The preparation method of the chitosan / essential oil (15 / 10) preparation (Preparation 5) comprises the following steps: S1, adding 15.0 g chitosan to 1.0 L 2% acetic acid aqueous solution, stirring to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 10.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, mix well to obtain an antibacterial agent with a reduced dosage ratio.

[0047] The preparation method of the chitosan / essential oil (10 / 15) preparation (Preparation 6) comprises the following steps: S1. Add 10.0 g chitosan to 1.0 L 2% acetic acid aqueous solution and stir to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 15.0 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, mix well to obtain an antibacterial agent with a reduced dosage ratio.

[0048] The preparation method of the chitosan / essential oil (5 / 20) preparation (Preparation 7) comprises the following steps: S1. Add 5 g of chitosan to 1.0 L of 2% acetic acid aqueous solution and stir to obtain a chitosan solution; S2, add 2.3 g glycerol to the chitosan solution obtained in S1 and stir evenly; S3, dissolving 20 g of borneol essential oil in 15.0 mL of ethanol to obtain an alcohol solution of borneol essential oil; S4, adding the borneol essential oil alcohol solution obtained in S3 dropwise to the mixed solution obtained in S2, and stirring evenly; S5. Add 10 mL of Tween-80 and 1 g of encapsulated 1-MCP (the carrier is cyclodextrin) to the mixed solution obtained in S4, mix well to obtain an antibacterial agent with a reduced dosage ratio.

[0049] To explore the effects of 7 preparations on tomato preservation, the test methods are as follows: S1. Wash fresh tomatoes of similar size and color with sterile water, wipe off the surface moisture, and obtain clean tomatoes.

[0050] S2. Take 5 PE packaging bags, coat the corresponding preparations in the PE bags of the experimental group, and let them dry. The PE bags of the blank control group remain unchanged.

[0051] S3. Put fresh tomatoes of similar size and color into PE bags in the experimental group and the control group and seal them.

[0052] S4. Store at room temperature, observe the appearance and color changes of the two groups of tomatoes, and take photos to record the results. Fig. 9 , Fig.10 (Note: The antibacterial and fresh-keeping effect experiments of 7 groups of preparations were carried out simultaneously. Putting the results of all groups in one figure will seriously affect the resolution. Therefore, in order to meet the requirements of clear drawings, the experimental results of 8 groups of 7 preparations and a blank group are divided into two figures for expression).

[0053] Conclusion: Figure 9-10 It can be seen that the tomatoes in the blank control group had serious fungus growth and rot on the 6th and 12th days; the tomatoes in the preparation 1 group without essential oil also had serious fungus growth and rot on the 6th day (Day6) and the 12th day (Day12), and the severity of fungus growth and rot was slightly better than that of the blank control group; the tomatoes in the preparation 2 group without chitosan also had obvious fungus growth on Day12, which may be due to the lack of film-forming properties of chitosan in the preparation, the failure to evenly disperse the borneol essential oil on the surface of the bag, and the failure to control the volatilization of the essential oil; when the amount of chitosan in the preparation 3 group was increased to 20g and the amount of borneol essential oil was decreased to 5g, that is, the mass ratio of the two was 4, the tomatoes also had obvious fungus growth on Day12; when the amount of chitosan in the preparation 7 was decreased to 5g and the amount of borneol essential oil was increased to 20g, that is, the mass ratio of the two was 0.25, the tomatoes also had obvious fungus growth on Day12. Preparations 4 to 6 have better antibacterial and fresh-keeping effects. Therefore, preparations composed of chitosan and borneol essential oil at the same time and in specific dosages have better antibacterial and fresh-keeping effects.

[0054] Example 4 This example prepares an efficient and safe antibacterial agent, and the preparation method is the same as that of Example 1. The antibacterial and fresh-keeping effect of the antibacterial agent during the storage of cucumbers is tested as follows: S1. Wash fresh cucumbers of similar size and color with sterile water, wipe off the surface moisture, and obtain clean cucumbers.

[0055] S2. Take two cartons of the same size and put them into polyethylene (PE) packaging bags, which are divided into an experimental group and a control group. The PE bags of the experimental group are coated with an antibacterial agent and dried, while the control group is not treated in any way.

[0056] S3. Place fresh cucumbers of similar size and color into PE bags in the experimental and control groups and seal them.

[0057] S4. Store the cucumbers at room temperature, observe the appearance and color changes of the two groups of cucumbers, and take photos to record the results. Fig.11 .

[0058] Conclusion: Fig.11 It can be seen that after Day 6 (storage for 6 days), most of the cucumbers in the control group have turned yellow compared to Day 0 (the day the experiment was carried out), and some cucumbers have rotted and deteriorated. After Day 12 (storage for 12 days), the cucumbers in the control group have turned yellow, and some cucumbers have seriously rotted and deteriorated. On the contrary, the color of the cucumbers in the antibacterial agent group was green after Day 6, with no obvious change compared to Day 0, and only slight yellowing after Day 12. The antibacterial agent has a significant fresh-keeping and antibacterial effect on the storage of cucumbers.

[0059] Example 5 This example prepares an efficient and safe antibacterial agent, and the preparation method is the same as that of Example 1. The antibacterial and fresh-keeping effect of the antibacterial agent during tomato storage is tested as follows: S1. Wash fresh tomatoes of similar size and color with sterile water, wipe off the surface moisture, and obtain clean tomatoes.

[0060] S2. Take two cartons of the same size and put them into PE packaging bags, which are divided into an experimental group and a control group. The PE bags of the experimental group are coated with an antibacterial agent and dried, while the control group is not treated in any way.

[0061] S3. Put fresh tomatoes of similar size and color into PE bags in the experimental group and the control group and seal them.

[0062] S4. Store at room temperature, observe the appearance and color changes of the two groups of tomatoes, and take photos to record the results. Fig.12 .

[0063] Conclusion: Fig.12It can be seen that after Day 6, some tomatoes in the control group had mold spots and began to rot compared to Day 0. After Day 12, the control group tomatoes had large mold spots and were seriously deteriorated, dehydrated and smelly. On the contrary, after Day 6, the tomatoes in the antibacterial agent group had no obvious changes compared to Day 0, and after Day 12, only some tomatoes had a small amount of mold spots. The antibacterial agent has a significant fresh-keeping and antibacterial effect on tomato storage.

[0064] Example 6 This example prepares an efficient and safe antibacterial agent, and the preparation method is the same as that of Example 1. The antibacterial and fresh-keeping effect of the antibacterial agent during the storage of bananas is tested as follows: S1. Wash fresh bananas of similar size and color with sterile water, wipe off the surface moisture, and obtain clean bananas.

[0065] S2. Take two cartons of the same size and put them into PE packaging bags, which are divided into an experimental group and a control group. The PE bags of the experimental group are coated with an antibacterial agent and dried, while the control group is not treated in any way.

[0066] S3. Put fresh bananas of similar size and color into PE bags in the experimental group and the control group and seal them.

[0067] S4. Store at room temperature, observe the appearance and color changes of the two groups of bananas, and take photos to record the results. Fig.13 .

[0068] Conclusion: Fig.13 It can be seen that after Day 6, the surface of the bananas in the control group turned black compared with Day 0. When gently pressed, the bananas softened significantly. After peeling the skin, it was found that the flesh had become soft and transparent. After Day 6, the skin of the bananas in the antibacterial agent group also turned black, but when pressed by hand, the bananas did not soften. After peeling the skin, the flesh was white to slightly yellow, bright in color, and no mold spots were observed. The antibacterial agent has a fresh-keeping and antibacterial effect on the storage of bananas.

[0069] Example 7 This example prepares an efficient and safe antibacterial agent, and the preparation method is the same as that of Example 1. The antibacterial and fresh-keeping effect of the antibacterial agent during the storage of apples is tested as follows: S1. Wash fresh apples of similar size and color with sterile water, wipe off the surface moisture, and obtain clean apples.

[0070] S2. Take two PE packaging boxes of the same size and divide them into an experimental group and a control group; the PE boxes in the experimental group are coated with an antibacterial agent and dried, while the control group does not receive any treatment.

[0071] S3. Place fresh apples of similar size and color into the PE boxes in the experimental and control groups and seal them.

[0072] S4. Store the apples at room temperature, observe the appearance and color changes of the two groups of apples, and take photos to record the results. Fig.14 .

[0073] Conclusion: Fig.14 It can be seen that the color of the apples in the control group turned yellow after Day 6 compared with Day 0. After Day 12, the color of the apples in the control group turned yellow more obviously, and the skin became dry and wrinkled. After Day 6, the color of the apples in the antibacterial agent group turned slightly yellow compared with Day 0. After Day 12, the apples were green-yellow, and the skin did not become dry and wrinkled. The antibacterial agent has the effect of preserving and delaying the ripening of apples.

[0074] Example 8 This example prepares an efficient and safe antibacterial agent, and the preparation method is the same as that of Example 1. The antibacterial and fresh-keeping effect of the antibacterial agent during the storage of jujube is tested as follows: S1. Wash fresh jujubes of similar size and color with sterile water, wipe off the surface moisture, and obtain clean jujubes.

[0075] S2. Take two cartons of the same size and put them into PE packaging bags, which are divided into an experimental group and a control group. The PE bags of the experimental group are coated with an antibacterial agent and dried, while the control group is not treated in any way.

[0076] S3. Put fresh jujubes of similar size and color into the PE bags in the experimental group and the control group and seal them.

[0077] S4. Store at room temperature, observe the appearance and color changes of the two groups of jujubes, and take photos to record the results. Fig.15 .

[0078] Conclusion: Fig.15 It can be seen that after Day 6, the jujubes in the control group showed signs of turning yellow and red compared with Day 0. Some jujubes had already developed mold spots. After Day 12, the jujubes in the control group had all turned yellow, dried and wrinkled, and some jujubes had turned red with obvious mold spots. On the contrary, after Day 6, the jujubes in the antibacterial agent group had no obvious changes compared with Day 0. After Day 12, only some jujubes turned yellow and some turned red, but no mold appeared. The antibacterial agent has a significant fresh-keeping and antibacterial effect on the storage of jujubes.

Claims

1. A method for preparing an antibacterial agent, characterized in that: The preparation method comprises the following steps: 1) Add chitosan to an acetic acid aqueous solution and stir to obtain a chitosan solution; 2) Add glycerol to the chitosan solution and stir evenly to obtain a mixed solution A; 3) dissolving borneol essential oil in ethanol to obtain borneol essential oil alcohol solution; 4) adding the borneol essential oil alcohol solution dropwise to the mixed solution A and stirring to obtain a mixed solution B; 5) Add Tween-80 and the included 1-methylcyclopropene to the mixed solution B and mix well to obtain an antibacterial agent.

2. The preparation method according to claim 1, wherein The volume concentration of the acetic acid aqueous solution is 2%, and the usage ratio of the acetic acid aqueous solution, chitosan, glycerol, borneol essential oil, ethanol, Tween 80, and inclusion 1-methylcyclopropene is 1000 mL: 7-18 g: 2.3 g: 6-15 g: 15 mL: 10 mL: 1 g.

3. The preparation method according to claim 1, wherein The weight ratio of the chitosan to the borneol essential oil is 0.5-3.

4. The preparation method according to any one of claims 1 to 3, wherein The chitosan has a deacetylation degree of ≥90% and a molecular weight of 300,000-600,000.

5. The preparation method according to any one of claims 1 to 3, wherein The carrier of the inclusion 1-methylcyclopropene is cyclodextrin, and the content of 1-methylcyclopropene in the inclusion complex is ≥4%.

6. An antibacterial agent, characterized in that The antibacterial agent is prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the antibacterial agent prepared by the preparation method according to any one of claims 1 to 5 or the antibacterial agent according to claim 6 in the preparation of a product containing an antibacterial preservative for fruits and vegetables.

8. The use according to claim 7, characterized in that The fruits and vegetables include cucumbers, tomatoes, jujubes, bananas or apples.

9. The use according to claim 7, characterized in that The products include fresh-keeping film, fresh-keeping bags and packaging bags.

10. The use according to claim 7, characterized in that The specific operation steps of preparing the product containing the antibacterial agent for fruits and vegetables are as follows: coating the antibacterial agent in a polyethylene packaging bag and drying it in the air.

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