Coating preservation material as well as preparation method and application thereof

Abstract

The invention provides a coating preservation material as well as a preparation method and application thereof, and belongs to the technical field of chemical modification of biomass organic polymer materials. The structural formula of the chitosan / polyphenol / quaternary phosphonium salt derivative disclosed by the invention is as shown in # imgabs0 #. The preparation method comprises the following steps: modifying chitosan by using natural phenolic acid and quaternary phosphonium salt to prepare an amphiphilic chitosan derivative; then preparing a plant essential oil microcapsule by taking the amphiphilic chitosan derivative as a wall material and plant essential oil as a core material; and finally, compounding the plant essential oil microcapsules with a film-forming material to construct a film-coating fresh-keeping material, and applying the film-coating fresh-keeping material to fresh keeping of fruits and vegetables.

Description

Technical Field

[0001] The invention relates to the technical field of chemical modification of biomass organic polymer materials, and in particular to a coating fresh-keeping material and a preparation method and application thereof. Background Art

[0002] my country ranks first in the world in the production of fruits and vegetables, but the losses from picking, packaging, transportation, storage to sales are large due to mechanical damage, physiological aging and pathogens. The rot loss rate of fruits is as high as 25% to 40%, and the rot loss rate of vegetables is as high as 20% to 30%. In some developed countries, the post-harvest loss rate of fruits and vegetables is less than 5%. At present, the common methods of fruit and vegetable preservation include temperature control, gas control, wax coating and plastic packaging, deoxygenation preservation and the use of preservatives. These physical or chemical preservation technologies are costly, cumbersome to operate and difficult to control. Film preservation is to form a barrier film on the surface of fruits and vegetables to regulate the respiration of fruits and vegetables, block harmful microorganisms, and improve the preservation effect.

[0003] In recent years, people have been committed to developing and extracting natural, safe, non-toxic, and highly active coating preservative materials from plant or animal sources for the preparation of new and efficient fruit and vegetable coating preservatives. Chitosan extracted from shrimp and crab shells is a natural, environmentally friendly, non-toxic and harmless food preservative material with good biodegradability, film-forming and antibacterial properties. After being treated with chitosan coating, a colorless and transparent semi-permeable membrane will be formed on the surface of the fruit, which can not only prevent the loss of water in the fruit and reduce the water loss rate of the fruit, but also effectively prevent the invasion of microorganisms, reduce the respiration intensity of the fruit, and reduce the decay of the fruit to a certain extent, thereby extending the storage time of the fruit. Studies have shown that fruits treated with chitosan can significantly reduce the incidence of post-harvest diseases and inhibit the growth of pathogens.

[0004] Plant polyphenols are a class of secondary metabolites with polyphenolic structures that are widely present in plants. They have the advantages of high efficiency, non-toxicity, high selectivity and low resistance to drugs. They are recognized as highly efficient and pollution-free natural disinfectants and preservatives. Studies have shown that fruits treated with chitosan / plant polyphenols can significantly reduce the incidence of post-harvest diseases, inhibit the growth of pathogens, reduce fruit decay, and extend the storage time of fruits. In recent years, they have become a hot topic in the research of new coating preservation materials. However, plant oil polyphenols have poor stability and cannot be stored for a long time. Chitosan and polyphenols can form copolymers through the action of covalent bonds. Quaternary phosphonium salts are a new generation of highly efficient, broad-spectrum, low-toxic fungicides. The P element of quaternary phosphonium salts belongs to the same group as the N element of quaternary ammonium salts, and they have similar molecular structures and chemical properties to quaternary ammonium salts, but they have better heat resistance, less foam, and a wide range of pH values. Studies have shown that quaternary phosphonium salts have a stronger ability to adsorb electrons to bacteria or fungi and a better antibacterial effect because the electronegativity of the P element is greater than that of the N element of quaternary ammonium salts. Plant essential oils are a type of plant-derived secondary metabolites with broad-spectrum and high-efficiency antibacterial activity. They are recognized as pollution-free natural preservatives that can not only effectively improve the antiseptic and antibacterial effects of coating materials, but also improve the mechanical properties of the coating, thereby improving the preservation effect.

[0005] In the prior art, the Chinese invention patent with application number CN201810639168.5 discloses a chitosan / gelatin composite coating preservative and its preparation method. The invention composites chitosan, glycerol, gelatin, deionized water and glacial acetic acid solution to study the preservation effect on Nanguo pear. The results show that the chitosan / gelatin composite coating liquid can reduce the weight loss rate of the fruit, slow down the rate of hardness decline, maintain the content of soluble solids and vitamin C, and has a significant preservation effect. The Chinese patent application CN201910810682.5 discloses a technology for preserving grapes with a tea polyphenol composite preservative. The invention patent uses tea polyphenol solution, chitosan solution and sodium nitroprusside solution as preservatives, and soaks the grapes separately for preservation. The results show that the preservation technology of the invention is green and environmentally friendly, low cost, and has good grape preservation effect at room temperature. The Chinese patent application number CN201710750157.X discloses a plant essential oil composite chitosan citrus coating preservative and its preparation. The invention patent mixes compound plant essential oil, chitosan, Chinese toon-water chestnut peel composite extract, natamycin, and CaCl2 to obtain an essential oil chitosan composite coating agent, which has a good preservation effect on citrus.

[0006] Although the above patents all obtain coating preservation materials by means of composite matching, they have the problems of single coating components, poor mechanical properties and stability of the coating, and single chitosan has poor antibacterial properties and a narrow antibacterial spectrum, which in turn affects the final effect. Moreover, the composite film constructed by simply mixing polyphenols and chitosan may lack stability. In addition, due to the poor compatibility between hydrophobic essential oils and hydrophilic chitosan solutions, the coating liquid has poor mechanical properties after film formation, and the film is easy to break. In addition, the essential oil has no sustained-release function, and the antibacterial and preservation effect time is short. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a coating fresh-keeping material and a preparation method and application thereof. The present invention utilizes natural phenolic acid and quaternary phosphonium salt to modify chitosan to prepare amphiphilic chitosan derivatives; then uses the amphiphilic chitosan derivatives as wall materials and plant essential oils as core materials to prepare plant essential oil microcapsules; finally, the plant essential oil microcapsules are compounded with film-forming materials to construct a coating fresh-keeping material, and the coating fresh-keeping material is applied to the preservation of fruits and vegetables.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention is a chitosan / polyphenol / quaternary phosphonium salt derivative, the structural formula of which is shown in Formula I:

[0010]

[0011] In formula I, m, n, and t are all natural numbers greater than or equal to 1 and less than or equal to 1000, s=0 or 1, X is one of F, Cl, Br, I, HSO3, HCO3, H2PO4, NO3, CH3CH2COO, CH3COO, and HCOO, and R1 is -CH=CH- or R2, R3, R4, R5, and R6 are each independently selected from -H, -OH or -O-CH3, and R7, R8, and R9 are each independently selected from an aromatic hydrocarbon group or an aromatic hydrocarbon derivative group.

[0012] The second technical solution of the present invention is a method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative, comprising the following steps:

[0013] The chitosan and polyphenol are subjected to amidation reaction to obtain a chitosan-polyphenol copolymer;

[0014] The chitosan-polyphenol copolymer is subjected to an amidation reaction with a carboxyl quaternary phosphonium salt to obtain the chitosan / polyphenol / quaternary phosphonium salt derivative.

[0015] The third technical solution of the present invention is an amphiphilic chitosan / plant essential oil microcapsule, wherein the wall material of the amphiphilic chitosan / plant essential oil microcapsule is the above-mentioned chitosan / polyphenol / quaternary phosphonium salt derivative, and the core material is plant essential oil; the mass ratio of the wall material to the core material is (1-3):1.

[0016] The fourth technical solution of the present invention is a coating preservative material, which includes the following components by mass: 1 to 10 parts of a film-forming substance, 10 to 70 parts of a dispersant, 0.1 to 10 parts of the above-mentioned amphiphilic chitosan / plant essential oil microcapsules, 1 to 5 parts of a plasticizer, 0.1 to 10 parts of nano-reinforced particles and 0.1 to 5 parts of a binder.

[0017] A fifth technical solution of the present invention is an application of the above-mentioned coating fresh-keeping material in the preservation of fruits and vegetables.

[0018] The present invention discloses the following technical effects:

[0019] The amphiphilic chitosan constructed by the present invention not only introduces polyphenols with antioxidant function, but also introduces quaternary phosphonium salts with antibacterial function. In addition, the micro-nano encapsulation technology is adopted, which not only improves the stability of essential oils and prolongs the antibacterial effect time of essential oils, but also helps to improve the sustained-controlled release and long-term antibacterial property of essential oils, and the plant essential oils and chitosan / polyphenols / quaternary phosphonium salt wall materials have a synergistic effect.

[0020] The coating preservation material constructed by the present invention can improve the mechanical properties of the film layer by adding nano-reinforced particles into the film liquid, thereby ensuring that the coating material has good stability, so as to better ensure the durability of the antibacterial preservation effect of the coating.

[0021] The present invention combines microcapsule embedding technology with polymer film-forming technology to prepare a coating preservation material, which effectively improves the quality of fruits and vegetables through synergistic effects, and can be applied to fruits and vegetables through convenient spraying or coating methods. The operation is simple and easy to use, and the application efficiency can be significantly improved, and the damage to fruits and vegetables can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 The infrared spectra (A) and ultraviolet spectra (B) of different substances in Example 1;

[0024] Figure 2The scanning electron microscope image and particle size distribution diagram of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules prepared in Example 1, wherein (a) is a scanning electron microscope image; (b) is a particle size distribution diagram;

[0025] Figure 3 is a sustained release curve diagram of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules of Example 1;

[0026] Figure 4 The mechanical properties diagram of the composite coating of Example 1 and Comparative Examples 1-3;

[0027] Figure 5 The figure shows the changes in the appearance of mangoes before and after storage using the preservatives of Example 1 and Comparative Examples 1-3;

[0028] Figure 6 The figure shows the changes in appearance of yellow peel before and after storage using the preservatives of Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] Room temperature herein means a temperature of 20-30°C.

[0035] The present invention provides a chitosan / polyphenol / quaternary phosphonium salt derivative, the structural formula of which is shown in Formula I:

[0036]

[0037] In formula I, m, n, and t are all natural numbers greater than or equal to 1 and less than or equal to 1000, s=0 or 1, X is one of F, Cl, Br, I, HSO3, HCO3, H2PO4, NO3, CH3CH2COO, CH3COO, and HCOO, and R1 is -CH=CH- or R2, R3, R4, R5, and R6 are each independently selected from -H, -OH or -O-CH3, and R7, R8, and R9 are each independently selected from an aromatic hydrocarbon group or an aromatic hydrocarbon derivative group.

[0038] In some embodiments of the present invention, the chitosan / polyphenol / quaternary phosphonium salt derivative has the structural formula:

[0039]

[0040] The present invention also provides a method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative, comprising the following steps:

[0041] The chitosan and polyphenol are subjected to amidation reaction to obtain a chitosan-polyphenol copolymer;

[0042] The chitosan-polyphenol copolymer is subjected to an amidation reaction with a carboxyl quaternary phosphonium salt to obtain the chitosan / polyphenol / quaternary phosphonium salt derivative.

[0043] In some embodiments of the present invention, the amidation reaction of chitosan and polyphenol is specifically as follows: polyphenol and condensation agent I are added to solution I containing chitosan and activator, and the reaction is carried out at room temperature for 24 to 36 hours.

[0044] In some embodiments of the present invention, the viscosity average molecular weight of chitosan is 1.2×10 3 ~2.5×10 5 , Deacetylation degree ≥ 80%;

[0045] If the viscosity average molecular weight of chitosan is too large, it will be difficult to dissolve and reduce the solubility in acetic acid aqueous solution, which is not conducive to the subsequent experiments; if the deacetylation degree is too large, it will also cause the above results. If the viscosity average molecular weight of chitosan is too low, the mechanical properties of the film will be poor; if the deacetylation degree is too small, it will also cause the above results. In order to ensure the mechanical properties after film formation, the present invention preferably uses the above parameter range.

[0046] The activator is at least one of 1-hydroxy-benzotriazole (HOBT), benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), and O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU);

[0047] The polyphenol is at least one of chlorogenic acid, ferulic acid, gentisic acid, vanillic acid, cinnamic acid, syringic acid, sinapic acid, p-coumaric acid, caffeic acid, protocatechuic acid and gallic acid;

[0048] The condensing agent I is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide (DIC);

[0049] The mass ratio of the activator to chitosan is 0.5:1-5:1; the mass ratio of the condensing agent to chitosan is 0.5:1-5:1; the mass ratio of the polyphenol to chitosan is 0.5:1-5:1; and the concentration of chitosan in the solution I is 2-50 mg / mL.

[0050] In some embodiments of the present invention, the solvent for dissolving the chitosan and the activator is one or more of water, methanol, ethanol, isopropanol, chloroform, ethyl acetate, tetrahydrofuran and N,N-dimethylformamide.

[0051] In some embodiments of the present invention, the chitosan-polyphenol copolymer is subjected to an amidation reaction with a carboxyl quaternary phosphonium salt by uniformly mixing the chitosan / polyphenol derivative with an activator, adding a carboxyl quaternary phosphonium salt and a condensing agent II, mixing uniformly, and reacting at room temperature for 24 to 36 hours.

[0052] In some embodiments of the present invention, the activator is the same as the activator described in the above technical solution;

[0053] The carboxyl quaternary phosphonium salt is one or more of 5-carboxypentyl-triphenylphosphonium bromide, 4-carboxybutyl-tritylphosphonium bromide and 3-carboxypropyl-tritylphosphonium iodide;

[0054] The condensation agent II is one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), dicyclohexylcarbodiimide hydrochloride (DCC·HCl) and diisopropylcarbodiimide hydrochloride (DIC·HCl);

[0055] The mass ratio of the chitosan / polyphenol derivative to the carboxyl quaternary phosphonium salt is 1:(0.5-5); the molar ratio of the activator to the carboxyl quaternary phosphonium salt is (1-2):1; and the molar ratio of the condensation agent II to the carboxyl quaternary phosphonium salt is (1-2):1.

[0056] In some embodiments of the present invention, after the amidation reaction is completed, the step of dialyzing the obtained reaction product with water for 3 to 5 days is also included.

[0057] The present invention grafts polyphenol and quaternary phosphonium salt into chitosan, so that the chitosan has both antioxidant activity and antibacterial property, wherein the higher the grafting rate of polyphenol, the better the antioxidant activity of the product; the higher the grafting rate of quaternary phosphonium salt, the better the antibacterial effect of the product. The present invention controls the amount of reactants by comprehensively considering the influence of grafting of polyphenol and quaternary phosphonium salt on chitosan, so that the grafting rate of polyphenol is between 5.3% and 20.8%, and the grafting rate of quaternary phosphonium salt is between 8.7% and 25.6%; the product in this grafting range not only has good antioxidant activity, but also has strong antibacterial property.

[0058] The present invention introduces plant polyphenols and quaternary phosphonium salts into the molecular structure of chitosan to prepare chitosan / polyphenol / quaternary phosphonium salt derivatives, which are then compounded with plant essential oils. The chitosan derivatives, as preservatives or effective ingredients of preservatives, play a good preservation role in preserving fruits and vegetables. The chitosan derivatives in the composite coating film have dual active functional groups of plant polyphenols and quaternary phosphonium salts, and plant essential oils with antibacterial active ingredients are added. Compared with pure chitosan films, the composite coating film has superior antibacterial and antioxidant activities in terms of being used for preparing coating films for preservation, and also has good mechanical properties and physical barrier properties.

[0059] The present invention also provides an amphiphilic chitosan / plant essential oil microcapsule, wherein the wall material of the amphiphilic chitosan / plant essential oil microcapsule is the chitosan / polyphenol / quaternary phosphonium salt derivative, and the core material is the plant essential oil; the mass ratio of the wall material to the core material is (1-3):1.

[0060] In some embodiments of the present invention, the particle size of the amphiphilic chitosan / plant essential oil microcapsules is 2 to 4 μm.

[0061] In some embodiments of the present invention, the plant essential oil is at least one of thyme essential oil, galangal essential oil, tea tree essential oil, lemon essential oil, citronella essential oil, grapefruit peel essential oil, mustard essential oil, peppermint essential oil, cinnamon essential oil, clove essential oil, garlic essential oil, almond essential oil, eucalyptus essential oil, ylang-ylang essential oil and lavender essential oil.

[0062] In some embodiments of the present invention, the preparation method of the amphiphilic chitosan / plant essential oil microcapsules is:

[0063] The chitosan / polyphenol / quaternary phosphonium salt derivative is dissolved in solvent A to obtain solution A, and the plant essential oil and organic solvent B are mixed evenly to obtain solution B;

[0064] The solution B is added to the solution A, followed by stirring, dialysis, ultrasound, and freeze drying to obtain the amphiphilic chitosan / plant essential oil microcapsules.

[0065] In some embodiments of the present invention, the solvent A is water; the organic solvent B is methanol or ethanol; the concentration of chitosan / polyphenol / quaternary phosphonium salt derivative in the solution A is 1.0-30.0 mg / mL; the concentration of plant essential oil in the solution B is 2-20 mg / mL; the stirring is at a rate of 100-800 r / min for 1.5-4 h; the dialysis time is 24-48 h; the power of the ultrasonic treatment is 150-600 W, the ultrasonic time is 5-10 min, and the number of ultrasonic times is 2-4 times.

[0066] The present invention also provides a coating preservative material, which comprises the following components by mass: 1 to 10 parts of a film-forming substance, 10 to 70 parts of a dispersant, 0.1 to 10 parts of the above-mentioned amphiphilic chitosan / plant essential oil microcapsules, 1 to 5 parts of a plasticizer, 0.1 to 10 parts of nano-reinforced particles and 0.1 to 5 parts of a binder.

[0067] In some embodiments of the present invention, the film-forming substance is at least one of starch, cellulose, polyvinyl alcohol, zein, chitosan, cyclodextrin, and gelatin;

[0068] The dispersant is at least one of water, methanol, ethanol, isopropanol, chloroform and ethyl acetate;

[0069] The plasticizer is at least one of ethylene glycol, glycerol, sorbitol, polyethylene glycol with a molecular weight less than 5000, ethylenediamine, and triethanolamine;

[0070] The binder is at least one of gellan gum, carrageenan, oxidized starch, cationic starch, etherified starch, esterified starch, wheat protein, corn protein, and gelatin;

[0071] The nano-enhancing ion is at least one of nano-cellulose, nano-TiO2, nano-SiO2, nano-CaCO3, nano-ZnO, nano-MgO, nano-Au, and nano-Ag.

[0072] In some embodiments of the present invention, the method for preparing the coating preservative material comprises the following steps:

[0073] (1) dispersing the film-forming substance in a dispersant and stirring to obtain a solution or gel;

[0074] (2) dispersing the amphiphilic chitosan / plant essential oil microcapsules, plasticizer, nano-reinforced particles, and binder in a dispersant, stirring, and obtaining a dispersion;

[0075] (3) The solution or gel obtained in step (1) and the dispersion obtained in step (2) are mixed and stirred to obtain the composite coating preservative.

[0076] In some embodiments of the present invention, in steps (1), (2) and (3), the stirring time is 0.5 to 12 hours and the temperature is 20 to 90°C.

[0077] The present invention also provides the application of the coating fresh-keeping material in the preservation of fruits and vegetables; the fruits and vegetables are at least one of yellow peel, mango, pineapple, banana, pitaya, lychee, longan, eggplant, cucumber, green pepper, tomato, and potato. The present invention dilutes the coating fresh-keeping material by 200 to 800 times, sprays or coats it on the fruits and vegetables, and air-dries it, so as to achieve the technical effect of preserving fruits and vegetables.

[0078] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0079] Unless otherwise specified, the raw materials and reagents used in the examples can be obtained through commercial channels.

[0080] Example 1

[0081] (1) Weigh 0.20 g chitosan (viscosity average molecular weight 1.2 × 10 3, deacetylation degree ≥ 80%) was dissolved in 100 mL of 1% (v / v) acetic acid aqueous solution to prepare a chitosan aqueous solution with a concentration of 2.0 mg / mL. Then 0.1 g of 1-hydroxybenzotriazole (HOBT) was added to the chitosan aqueous solution and stirred until completely dissolved. 0.10 g of caffeic acid (CA) and 0.1 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) were dissolved in 10 mL of ethanol, then added dropwise to the chitosan aqueous solution, reacted at 25°C for 24 h, dialyzed with deionized water for 3 days (dialysis bag molecular equivalent is 3500), and freeze-dried for 24 h to obtain chitosan / polyphenol copolymer.

[0082] (2) Weigh 0.0914 g of chitosan-polyphenol copolymer obtained in step (1) and 0.0135 g (0.1 mmol) of activator 1-hydroxy-benzotriazole (HOBT) in 100 mL of deionized water and mix them evenly, then add 0.0457 g (0.1 mmol) of 5-carboxypentyl-triphenylphosphonium bromide and 0.0192 g (0.1 mmol) of condensation agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) to the above solution (wherein n(HOBT):n(quaternary phosphonium salt)=1:1, n(EDC·HCl):n(quaternary phosphonium salt)=1:1), and react at room temperature for 36 hours. The obtained reaction product is dialyzed with water for 3 days and freeze-dried to obtain a chitosan / polyphenol / quaternary phosphonium salt derivative. The grafting rate of caffeic acid (CA) is 5.3%, while the grafting rate of 5-carboxypentyl-triphenylphosphonium bromide is 8.7%.

[0083] (3) Take 0.3 g of the chitosan / polyphenol / quaternary phosphonium salt derivative obtained in step (2), add 10 mL of deionized water, stir until completely dissolved, and then ultrasonicate for 10 min with an ultrasonicator, and repeat the treatment twice to obtain a transparent aqueous solution.

[0084] (4) 5.0 mL of a 20 mg / mL methanol solution of mustard essential oil was added to the solution of step (3), stirred at 100 r / min for 4.0 h, and dialyzed with deionized water for 48 h to remove methanol. The dialyzed retained solution was subjected to ultrasonic treatment for 5 min, and the treatment was repeated 3 times, followed by freeze drying to obtain chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules.

[0085] (5) Dissolve 1 g of polyvinyl alcohol in 70 mL of water, stir at 90 °C for 0.5 h to obtain a uniform and stable viscous solution, and then leave it to stand at room temperature.

[0086] (6) 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules obtained in step (4) were dissolved in 10 mL of deionized water, and then 1 g of glycerol, 0.1 g of nano-TiO2, and 0.1 g of gellan gum were dispersed in 10 mL of deionized water, and stirred at 20° C. for 1.0 h to obtain a uniform and stable dispersion.

[0087] (7) The viscous solution obtained in step (5) and the dispersion obtained in step (6) were mixed, and stirred at 20° C. for 2.0 h to obtain a coating preservative material.

[0088] Example 2

[0089] (1) Weigh 2.0 g chitosan (viscosity average molecular weight 2.4 × 10 4 , deacetylation degree ≥ 80%) was dissolved in 100 mL of 1% (v / v) acetic acid aqueous solution to prepare a chitosan aqueous solution with a concentration of 20 mg / mL. Then 1.0 g of 1-hydroxybenzotriazole (HOBT) was added to the chitosan aqueous solution and stirred until completely dissolved. 2.0 g of gallic acid (GA) and 1.0 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) were dissolved in 20 mL of ethanol, then added dropwise to the chitosan aqueous solution, reacted at 25°C for 24 h, dialyzed with deionized water for 3 days (dialysis bag molecular equivalent is 7000), and freeze-dried for 48 h to obtain chitosan / polyphenol copolymer.

[0090] (2) Weigh 0.457 g of chitosan-polyphenol copolymer obtained in step (1) and 0.0135 g (0.1 mmol) of activator 1-hydroxy-benzotriazole (HOBT) in 100 mL of deionized water and mix them evenly, then add 0.457 g (1.0 mmol) of 5-carboxypentyl-triphenylphosphonium bromide and 0.192 g (1.0 mmol) of condensation agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) to the above solution (wherein n(HOBT):n(quaternary phosphonium salt)=1:1, n(EDC·HCl):n(quaternary phosphonium salt)=1:1), and react at room temperature for 48 h. The obtained reaction product is dialyzed with water for 3 days and freeze-dried to obtain a chitosan / polyphenol / quaternary phosphonium salt derivative. The grafting rate of gallic acid (GA) is 20.8%, while the grafting rate of 5-carboxypentyl-triphenylphosphonium bromide is 25.6%.

[0091] (3) Take 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt derivative obtained in step (2), add 10 mL of deionized water, stir until completely dissolved, and then ultrasonicate for 5 min with an ultrasonicator, and repeat the treatment twice to obtain a transparent aqueous solution.

[0092] (4) 10.0 mL of an ethanol solution of thyme essential oil at a concentration of 10.0 mg / mL was added to the solution of step (3), stirred at 800 r / min for 1.5 h, and dialyzed with deionized water for 48 h to remove methanol. The dialyzed retained solution was subjected to ultrasonic treatment for 10 min, and the treatment was repeated twice, followed by freeze drying to obtain chitosan / polyphenol / quaternary phosphonium salt / thyme essential oil microcapsules.

[0093] (5) 3 g of polyvinyl alcohol and 3 g of starch were dissolved in 70 mL of water, stirred at 90 °C for 1.0 h to obtain a uniform and stable viscous solution, which was then allowed to stand at room temperature.

[0094] (6) 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt / thyme essential oil microcapsules obtained in step (4) were dissolved in 10 mL of deionized water, and then 5 g of sorbitol, 2 g of nano-SiO2, and 1.0 g of cationic starch were added and dispersed in 20 mL of deionized water, and stirred at 30° C. for 2.0 h to obtain a uniform and stable dispersion.

[0095] (7) The viscous solution obtained in step (5) and the dispersion obtained in step (6) are mixed, and stirred at 30° C. for 6 h to obtain a coating preservative material.

[0096] Example 3

[0097] (1) Weigh 1.0 g chitosan (viscosity average molecular weight 2.5 × 10 5 , deacetylation degree ≥ 80%) was dissolved in 100 mL of 1% (v / v) acetic acid aqueous solution to prepare a chitosan aqueous solution with a concentration of 10 mg / mL. Then 1.0 g of 1-hydroxybenzotriazole (HOBT) was added to the chitosan aqueous solution and stirred until completely dissolved. 2.0 g of p-coumaric acid (p-CA) and 1.0 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) were dissolved in 20 mL of ethanol, then added dropwise to the chitosan aqueous solution, reacted at 25°C for 24 hours, dialyzed with deionized water for 3 days (dialysis bag molecular equivalent is 7000), and freeze-dried for 48 hours to obtain chitosan / polyphenol copolymer.

[0098] (2) Weigh 0.457 g of chitosan-polyphenol copolymer obtained in step (1) and 0.0135 g (0.1 mmol) of activator 1-hydroxy-benzotriazole (HOBT) and mix them evenly in 100 mL of deionized water, then add 0.457 g (1.0 mmol) of 5-carboxypentyl-triphenylphosphonium bromide and 0.192 g (1.0 mmol) of condensation agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) to the above solution (wherein n(HOBT):n(quaternary phosphonium salt)=1:1, n(EDC·HCl):n(quaternary phosphonium salt)=1:1), and react at room temperature for 48 h. The obtained reaction product is dialyzed with water for 3 days and freeze-dried to obtain a chitosan / polyphenol / quaternary phosphonium salt derivative. The grafting rate of p-coumaric acid (p-CA) is 10.1%, while the grafting rate of 5-carboxypentyl-triphenylphosphonium bromide is 15.8%.

[0099] (3) Take 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt derivative obtained in step (2), add 10 mL of deionized water, stir until completely dissolved, and then ultrasonicate for 5 min with an ultrasonicator, and repeat the treatment twice to obtain a transparent aqueous solution.

[0100] (4) 10.0 mL of a methanol solution of tea tree essential oil at a concentration of 10.0 mg / mL was added to the solution of step (3), stirred at 800 r / min for 1.5 h, and dialyzed with deionized water for 48 h to remove methanol. The dialyzed retained solution was ultrasonically treated for 10 min, and the treatment was repeated twice, followed by freeze-drying to obtain chitosan / polyphenol / quaternary phosphonium salt / tea tree essential oil microcapsules.

[0101] (5) 2 g of polyvinyl alcohol and 2 g of cellulose were dissolved in 60 mL of water and stirred at 80 °C for 5 h to obtain a uniform and stable viscous solution, which was then allowed to stand at room temperature.

[0102] (6) 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt / tea tree essential oil microcapsules obtained in step (4) were dissolved in 10 mL of deionized water, and then 3 g of ethylene glycol, 3 g of nano ZnO, and 5.0 g of carrageenan were dispersed in 20 mL of deionized water, and stirred at 28° C. for 5 h to obtain a uniform and stable dispersion.

[0103] (7) The viscous solution obtained in step (5) and the dispersion obtained in step (6) were mixed, and stirred at 28° C. for 12 h to obtain a coating preservative material.

[0104] Comparative Example 1

[0105] (1) Dissolve 1 g of polyvinyl alcohol in 70 mL of water, stir at 90°C for 0.5 h to obtain a uniform and stable viscous solution, and then leave it to stand at room temperature.

[0106] (2) 0.1 g of the chitosan prepared in Example 1 was dissolved in 10 mL of acetic acid aqueous solution (v / v 1%), and then 1 g of glycerol, 0.1 g of nano-TiO2, and 0.1 g of gellan gum were added and dispersed in 10 mL of deionized water, and stirred at 20° C. for 1.0 h to obtain a uniform and stable dispersion.

[0107] (3) The viscous solution obtained in step (1) and the dispersion obtained in step (2) were mixed, and stirred at 20° C. for 2.0 h to obtain a coating preservative material.

[0108] Comparative Example 2

[0109] (1) Dissolve 1 g of polyvinyl alcohol in 70 mL of water, stir at 90°C for 0.5 h to obtain a uniform and stable viscous solution, and then leave it to stand at room temperature.

[0110] (2) 0.1 g of the chitosan / polyphenol copolymer in Example 1 was dissolved in 10 mL of aqueous solution, and then 1 g of glycerol, 0.1 g of nano-TiO2, and 0.1 g of gellan gum were added and dispersed in 10 mL of deionized water, and stirred at 20° C. for 1.0 h to obtain a uniform and stable dispersion.

[0111] (3) The viscous solution obtained in step (1) and the dispersion obtained in step (2) were mixed, and stirred at 20° C. for 2.0 h to obtain a coating preservative material.

[0112] Comparative Example 3

[0113] (1) Dissolve 1 g of polyvinyl alcohol in 70 mL of water, stir at 90°C for 0.5 h to obtain a uniform and stable viscous solution, and then leave it to stand at room temperature.

[0114] (2) 0.1 g of the chitosan / polyphenol / quaternary phosphonium salt derivative in Example 1 was dissolved in 10 mL of aqueous solution, and then 1 g of glycerol, 0.1 g of nano-TiO2, and 0.1 g of gellan gum were added and dispersed in 10 mL of deionized water, and stirred at 20° C. for 1.0 h to obtain a uniform and stable dispersion.

[0115] (3) The viscous solution obtained in step (1) and the dispersion obtained in step (2) were mixed, and stirred at 20° C. for 2.0 h to obtain a coating preservative material.

[0116] The test results of Example 1 are as follows:

[0117] 1. The structural functional groups of chitosan, chitosan / polyphenol copolymer, and chitosan / polyphenol / quaternary phosphonium salt derivatives of Example 1 were analyzed using a German Tensor27 infrared spectrometer (FT-IR) at a wave number of 500 to 4000 cm -1The UV-visible spectra of chitosan, chitosan / polyphenol copolymer, and chitosan / polyphenol / quaternary phosphonium salt derivative of Example 1 were measured using a UV-2550 UV-visible spectrophotometer from Shimadzu Corporation of Japan, with a scanning range of 190 to 400 nm and a deionized water solution as a reference solution.

[0118] Figure 1 (A) is the infrared spectra of different substances in Example 1. In the figure, curve (a) is chitosan; curve (b) is chitosan / caffeic acid copolymer; curve (c) is chitosan / caffeic acid / quaternary phosphonium salt derivative. In the infrared spectrum of chitosan (a), the characteristic peaks of the spectrum are as follows: 3260cm -1 The OH and NH stretching vibration absorption peaks in its structure are 2834 and 2879 cm -1 The absorption peaks are the asymmetric stretching vibration peak and symmetric stretching vibration peak of the methylene CH bond, 1668, 1595 and 1301 cm -1 The 1058 cm-1 and 1060 cm-2 correspond to the C=O stretching vibration (amide I), NH bending vibration (amide II), and CN stretching vibration (amide III) of the remaining N-acetyl groups, indicating that chitosan is not completely deacetylated. -1 is the COC stretching vibration absorption peak in chitosan. Compared with the infrared spectrum of chitosan (a), the chitosan / caffeic acid copolymer (b) has a peak at 3263 cm -1 The vibration absorption peaks of OH at 2834 and 2879 cm -1 The characteristic absorption peaks of methylene CH2 are enhanced at 1612, 1524 and 1380 cm -1 The characteristic peaks of benzene rings appeared, indicating that chitosan and caffeic acid were successfully grafted. Compared with the infrared spectrum of chitosan / polyphenol copolymer (b), the chitosan / caffeic acid / quaternary phosphonium salt derivative (c) showed a peak at 2834 cm -1 and 2879cm -1 The characteristic absorption peak of methylene CH2 becomes sharper and stronger at 1632cm -1 、1525cm -1 and 1376cm -1 Stronger characteristic peaks of benzene rings appeared, indicating that chitosan / caffeic acid copolymer was successfully grafted with quaternary phosphonium salt.

[0119] Figure 1(B) is the ultraviolet spectrogram of different substances in Example 1, in which curve (a) is chitosan; curve (b) is chitosan / caffeic acid copolymer; curve (c) is chitosan / caffeic acid / quaternary phosphonium salt derivative. It can be seen that chitosan (a) does not show an absorption peak within the range of 200-400nm, while chitosan / caffeic acid copolymer (b) has an obvious absorption peak at 301nm, which belongs to the π-system of the benzene ring; in the ultraviolet spectrogram (c) of chitosan / caffeic acid / quaternary phosphonium salt derivative, at 282nm and 256nm, obvious absorption peaks appear, which belong to the π-π conjugated system of the benzene ring. As can be seen from the figure, as polyphenols and quaternary phosphonium salts are grafted onto the structure of chitosan, the ultraviolet characteristic peaks of the copolymers have blue shifts, which is due to the hydrogen bonding between the benzene rings of the polymer and the -OH and -NH2 in the chitosan structure, resulting in changes in the characteristic peaks.

[0120] The chitosan / polyphenol / quaternary phosphonium salt derivatives prepared in Example 2 and Example 3 were subjected to infrared spectroscopy and ultraviolet spectroscopy analysis (analysis method is the same as that in Example 1). The results showed that polyphenols (gallic acid, p-coumaric acid), quaternary phosphonium salts were successfully grafted onto chitosan.

[0121] 2. The microscopic morphology of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules prepared in Example 1 was analyzed using a Hitachi S4800 field emission scanning electron microscope. The particle size distribution of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules prepared in Example 1 was analyzed using a Zeta potential-particle size analyzer (ZSP) from Malvern, UK.

[0122] Figure 2 The scanning electron microscope image and particle size distribution diagram of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules prepared in Example 1, wherein (a) is a scanning electron microscope image; (b) is a particle size distribution diagram. Figure 2 As can be seen in (a), the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules are regular spherical with a core-shell structure. The plant essential oil is embedded inside and distributed relatively evenly without obvious aggregation. Figure 2 It can be seen in (b) that the particle size of the microcapsules presents a normal distribution, mainly concentrated between 4.0 μm and 6.0 μm, and the average particle size is about 4.72 μm.

[0123] 3. Sustained release properties of chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules prepared in Example 1

[0124] 10.0 mL of chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules (concentration of 0.1 g / mL) were placed in a dialysis bag (molecular weight cutoff of 7000) and dialyzed in a phosphate buffered saline solution (pH = 7.8). 1 mL of the dialysate was taken out at different times, and the release of plant essential oil was measured using an ultraviolet spectrophotometer. The dialysate was replaced with 1 mL of fresh phosphate buffered saline solution, and then the relationship between the release time and the cumulative release amount was plotted.

[0125] Figure 3 The sustained release curve of the chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules of Example 1 is shown in FIG. Figure 3 As shown in the figure, in the first 8 hours of release, the burst release of plant essential oil in the microcapsule reached 22.23%. The burst release is due to the intermolecular force of chitosan / polyphenol / quaternary phosphonium salt derivatives, which makes a small amount of plant essential oil adsorbed in the microcapsule shell in a free state and released in advance; and as time accumulates, the plant essential oil embedded in the microcapsule is gradually released. It can be seen from the figure that the cumulative release of plant essential oil in chitosan / polyphenol / quaternary phosphonium salt / mustard essential oil microcapsules reached 72% at 144 hours, greatly extending the antibacterial effect time.

[0126] 4. Mechanical properties and barrier properties of the composite coating preservative prepared in Example 1

[0127] The physical and mechanical properties of the composite coating materials prepared in Comparative Examples 1-3 and Example 1 were measured using the UTM5000 electronic universal testing machine produced by Shenzhen Sansi Technology Co., Ltd. Figure 4 , wherein curve (a) is the composite coating of comparative example 1, curve (b) is the composite coating of comparative example 2, curve (c) is the composite coating of comparative example 3, and curve (d) is the composite coating of embodiment 1.

[0128] from Figure 4 It can be seen that the tensile strength and elongation at break of the chitosan composite film (4-a) of Comparative Example 1 are 1.34MPa and 86.7%, respectively, the tensile strength and elongation at break of the chitosan / polyphenol copolymer composite film (4-b) of Comparative Example 2 are 2.21MPa and 97.6%, respectively, the tensile strength and elongation at break of the chitosan / polyphenol / quaternary phosphonium salt derivative composite film (4-c) of Comparative Example 3 are 2.40MPa and 103.6%, respectively, and the tensile strength and elongation at break of the chitosan / polyphenol / quaternary phosphonium salt / plant essential oil microcapsule composite film of Example 1 are 3.35MPa and 111.2%, respectively, which are all higher than the performance of the comparative coating. This is because the microcapsules of the film-forming components in the chitosan / polyphenol / quaternary phosphonium salt / plant essential oil microcapsule composite film fill the gaps in the coating, and at the same time, due to the interaction between the components, the film is more tightly combined, thereby improving its mechanical properties.

[0129] 5. The application effect of the composite coating preservative prepared in Example 1, 4 groups of experiments AE were set up, and the specific treatment method of each group was:

[0130] Group (a): blank group, no treatment was taken, and the fruit surface was coated with deionized water;

[0131] Group (b): The coating preservation material obtained in Comparative Example 1 was diluted 500 times and coated on the surface of the fruit;

[0132] Group (c): The coating preservation material obtained in Comparative Example 2 was diluted 500 times and coated on the surface of the fruit;

[0133] Group (d): The coating preservation material obtained in Comparative Example 3 was diluted 500 times and coated on the surface of the fruit;

[0134] Group (e): The composite coating preservative obtained in Example 1 was diluted 500 times and coated on the surface of the fruit;

[0135] Figure 5 The following are the appearance changes of mangoes before and after storage in the blank group (a), comparative example 1 (b), comparative example 2 (c), comparative example 3 (d), and embodiment 1 (e). As can be seen from the figure, the blank group (a) is the most severely rotten, with obvious shrinkage on the 10th day and obvious black spots on the 15th day; the shrinkage of the fruit skin in comparative example 1 (b) is alleviated, but black spots appear on the 15th day, and large black spots appear on the surface of the fruit skin on the 20th day; the fruits of comparative examples 2 (c) and comparative example 3 (d) have a few black spots on the 20th day, but the surface of the fruit skin also shrinks to varying degrees; the mangoes treated in embodiment 1 (e) have the least degree of rot after 20 days of storage, the surface of the fruit is smooth, there is no obvious black spot phenomenon, and the fruit itself still maintains a certain degree of green. The above experimental results can prove that the chitosan / polyphenol / quaternary phosphonium salt derivative composite coating material has a fresh-keeping effect on mangoes, which not only delays the rot of the fruit, but also slows down the appearance of mango lesions.

[0136] Figure 6The appearance changes of the yellow peels before and after storage of the blank group (a), comparative example 1 (b), comparative example 2 (c), comparative example 3 (d), and embodiment 1 (e) are shown in the figure. As can be seen from the figure, the blank group (a) is the most severely rotten, with obvious browning of the fruit on the 2nd day, and cracked fruit and mildew on the 4th day; the browning of the fruit skin of comparative example 1 (b) is alleviated, but the browning of the fruit surface is obvious on the 4th day; the fruits of comparative examples 2 (c) and comparative example 3 (d) show a little browning on the 4th day, and cracked fruit appear on part of the fruit skin surface of comparative example 2 (c); the yellow peel treated in embodiment 1 (e) has the least degree of rot after 6 days of storage, with slight browning on the fruit surface, no cracking, and the fruit itself still maintains a certain degree of yellow-brown. The above experimental results can prove that the chitosan / polyphenol / quaternary phosphonium salt derivative composite coating material has a fresh-keeping effect, which not only delays the rot of the fruit, but also slows down the appearance of yellow peel browning and cracking.

[0137] As the test results of Examples 2 to 3 have the same conclusions as those of the test results of Example 1, they will not be described in detail due to space constraints.

[0138] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A chitosan / polyphenol / quaternary phosphonium salt derivative, characterized in that: The structural formula is shown in Formula I: In formula I, m, n, and t are all natural numbers greater than or equal to 1 and less than or equal to 1000, s=0 or 1, X is one of F, Cl, Br, I, HSO3, HCO3, H2PO4, NO3, CH3CH2COO, CH3COO, and HCOO, and R1 is -CH=CH- or R2, R3, R4, R5, and R6 are each independently selected from -H, -OH or -O-CH3, and R7, R8, and R9 are each independently selected from an aromatic hydrocarbon group or an aromatic hydrocarbon derivative group.

2. A method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative according to claim 1, characterized in that: The following steps are involved: The chitosan and polyphenol are subjected to an amidation reaction to obtain a chitosan-polyphenol copolymer; The chitosan-polyphenol copolymer is subjected to an amidation reaction with a carboxyl quaternary phosphonium salt to obtain the chitosan / polyphenol / quaternary phosphonium salt derivative.

3. The method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative according to claim 2, characterized in that: The specific steps of the amidation reaction of chitosan and polyphenol are as follows: polyphenol and condensation agent I are added to solution I containing chitosan and activator, and the reaction is carried out at room temperature for 24 to 36 hours.

4. The method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative according to claim 3, characterized in that: The viscosity average molecular weight of the chitosan is 1.2×10 3 ~2.5×10 5 , Deacetylation degree ≥ 80%; The activator is at least one of 1-hydroxy-benzotriazole, benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate, and O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate; The polyphenol is at least one of chlorogenic acid, ferulic acid, gentisic acid, vanillic acid, cinnamic acid, syringic acid, sinapic acid, p-coumaric acid, caffeic acid, protocatechuic acid and gallic acid; The condensing agent I is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, dicyclohexylcarbodiimide and diisopropylcarbodiimide; The mass ratio of the activator to chitosan is 0.5:1-5:1; the mass ratio of the condensing agent I to chitosan is 0.5:1-5:1; the mass ratio of the polyphenol to chitosan is 0.5:1-5:1; and the concentration of chitosan in the solution I is 2-50 mg / mL.

5. The method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative according to claim 2, characterized in that: The chitosan-polyphenol copolymer and carboxyl quaternary phosphonium salt are subjected to an amidation reaction specifically as follows: the chitosan / polyphenol derivative and the activator are uniformly mixed, and then the carboxyl quaternary phosphonium salt and the condensation agent II are added and mixed uniformly, and the mixture is reacted at room temperature for 24 to 36 hours.

6. The method for preparing the chitosan / polyphenol / quaternary phosphonium salt derivative according to claim 5, characterized in that: The activator is the same as the activator described in claim 4; The carboxyl quaternary phosphonium salt is one or more of 5-carboxypentyl-triphenylphosphonium bromide, 4-carboxybutyl-tritylphosphonium bromide and 3-carboxypropyl-tritylphosphonium iodide; The condensing agent II is one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, dicyclohexylcarbodiimide hydrochloride and diisopropylcarbodiimide hydrochloride; The mass ratio of the chitosan / polyphenol derivative to the carboxyl quaternary phosphonium salt is 1:(0.5-5); the molar ratio of the activator to the carboxyl quaternary phosphonium salt is (1-2):1; and the molar ratio of the condensation agent II to the carboxyl quaternary phosphonium salt is (1-2):

1.

7. An amphiphilic chitosan / plant essential oil microcapsule, characterized in that: The wall material of the amphiphilic chitosan / plant essential oil microcapsule is the chitosan / polyphenol / quaternary phosphonium salt derivative described in claim 1, and the core material is plant essential oil; the mass ratio of the wall material to the core material is (1-3):

1.

8. A coating preservative material, characterized in that: The composition comprises the following components by weight: 1 to 10 parts of film-forming substance, 10 to 70 parts of dispersant, 0.1 to 10 parts of the amphiphilic chitosan / plant essential oil microcapsules according to claim 7, 1 to 5 parts of plasticizer, 0.1 to 10 parts of nano-enhanced particles and 0.1 to 5 parts of binder.

9. The coating preservative material according to claim 8, characterized in that: The film-forming substance is at least one of starch, cellulose, polyvinyl alcohol, zein, chitosan, cyclodextrin and gelatin; The dispersant is at least one of water, methanol, ethanol, isopropanol, chloroform and ethyl acetate; The plasticizer is at least one of ethylene glycol, glycerol, sorbitol, polyethylene glycol with a molecular weight less than 5000, ethylenediamine, and triethanolamine; The binder is at least one of gellan gum, carrageenan, oxidized starch, cationic starch, etherified starch, esterified starch, wheat protein, corn protein, and gelatin; The nano-enhancing ion is at least one of nano-cellulose, TiO2, nano-SiO2, nano-CaCO3, nano-ZnO, nano-MgO, nano-Au, and nano-Ag.

10. Use of the coating fresh-keeping material according to claim 9 in the preservation of fruits and vegetables.

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