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CN-122011473-A - Polyvinyl chitosan tannic acid composite active membrane, preparation method and application thereof

CN122011473ACN 122011473 ACN122011473 ACN 122011473ACN-122011473-A

Abstract

The invention discloses a polyethylene chitosan tannic acid composite active membrane, a preparation method and application thereof, belonging to the technical field of food packaging materials, wherein the polyethylene membrane is sequentially subjected to oxygen plasma treatment and chemical grafting dual modification of a silane coupling agent to construct an amino-containing chemical anchoring layer; dissolving chitosan in citric acid aqueous solution, adding tannic acid to form ternary crosslinking coating liquid, and preparing the composite active film by adopting a double-layer gradient coating process. The obtained composite film has the tensile strength of 26.8MPa, the ultraviolet blocking rate of more than 99 percent, and the clearance rates of DPPH and ABTS free radicals of 95.8 percent and 99.2 percent respectively, has antibacterial activity, and can obviously prolong the shelf life when being used for fresh-keeping of the small cucumbers.

Inventors

  • DONG TIANYI
  • ZHANG LIJUN

Assignees

  • 安徽农业大学

Dates

Publication Date
20260512
Application Date
20260415

Claims (10)

  1. 1. A polyethylene chitosan tannic acid composite active membrane is characterized by sequentially comprising a polyethylene basal layer, a silane coupling agent chemical anchoring layer, a chitosan-citric acid primer layer and a chitosan-tannic acid-citric acid functional coating from bottom to top, wherein the silane coupling agent chemical anchoring layer is a polysiloxane thin layer formed by bonding gamma-aminopropyl triethoxysilane on the surface of the polyethylene membrane subjected to oxygen plasma treatment through Si-O-C covalent bonds, free amino groups are exposed on the surface of the thin layer, the chitosan-citric acid primer layer is a thin layer obtained by dissolving chitosan in citric acid aqueous solution and then drying to form a membrane, the thickness is 3-5 mu m, the chitosan-tannic acid-citric acid functional coating is a ternary crosslinked network thin layer formed by dissolving chitosan, tannic acid and citric acid under heating conditions through hydrogen bonds, schiff base covalent bonds and esterification crosslinking, the thickness is 8-12 mu m, and the addition amount of tannic acid is 2-6wt% of the mass of the chitosan.
  2. 2. The composite active film according to claim 1, wherein the polyethylene substrate layer is made of low-density polyethylene and has a thickness of 10-20 μm.
  3. 3. The composite active film according to claim 1, wherein the tannic acid is added in an amount of 4wt% based on the mass of chitosan.
  4. 4. The composite active membrane of claim 1, wherein the chitosan has a degree of deacetylation of 80-95% and a viscosity average molecular weight of 200-500 kda.
  5. 5. A method for preparing the polyvinyl chitosan tannic acid composite active film according to any one of claims 1 to 4, which is characterized by comprising the following steps: The surface of the polyethylene film is doubly modified, namely the polyethylene film is subjected to plasma treatment under the conditions of power of 30-50W and time of 20-60 s by taking oxygen as working gas, after the treatment is finished, the polyethylene film is immersed into an ethanol-water mixed solution of gamma-aminopropyl triethoxysilane with the concentration of 1-3 wt%, the polyethylene film is immersed for 20-40 min at room temperature, taken out, cleaned and dried for 20-40 min at 70-90 ℃ to enable silane to complete condensation reaction; Step two, preparing a chitosan-citric acid primer, namely adding chitosan into a citric acid aqueous solution with the concentration of 1.0-2.0wt%, stirring for 3-5 hours at 50-70 ℃ until the chitosan is completely dissolved, and adding a plasticizer; preparing a chitosan-citric acid solution according to the method of the second step, dissolving tannic acid in deionized water, adding the deionized water into the chitosan-citric acid solution, stirring at 50-70 ℃ for 0.5-1.5 h, and adding a plasticizer; and step four, double-layer gradient coating, namely coating the primer coating liquid in the step two on the surface of the modified polyethylene film in the step one, drying and pre-curing, and coating the functional coating liquid in the step three on the surface of the primer coating, and drying and curing.
  6. 6. The method according to claim 5, wherein the volume ratio of the ethanol-water mixed solution in the first step is (8-9.5) 1, and the pH of the solution is adjusted to 4.0-5.5 with acetic acid.
  7. 7. The preparation method according to claim 5, wherein the primer coating liquid in the fourth step has a coating thickness of 0.3-0.8 mm, a coating speed of 60-100 mm/min, a coating thickness of 0.8-1.5 mm, a coating speed of 80-120 mm/min, and a drying temperature of 50-70 ℃.
  8. 8. The preparation method according to claim 5, wherein the plasticizer in the second and third steps is glycerin, and the addition amount is 0.3-1.0% of the volume of the chitosan-citric acid solution.
  9. 9. Use of the polyvinyl chitosan tannic acid composite active film according to any one of claims 1-4 in food preservation packaging.
  10. 10. The use according to claim 9, wherein the food product is fresh fruit and vegetable having a moisture content of more than 90%.

Description

Polyvinyl chitosan tannic acid composite active membrane, preparation method and application thereof Technical Field The invention belongs to the technical field of food packaging materials, and particularly relates to a polyvinyl chitosan tannic acid composite active film, a preparation method thereof and application thereof in fresh fruit and vegetable preservation. Background Polyethylene films have long been widely used as food packaging materials due to their excellent mechanical strength, good heat sealability and low production cost. Wong et al (FoodChemistry, 2020, 329:126989) report a tilapia preservative film with a chitosan/gallic acid coating on a plasma-treated polyethylene film as a substrate, wherein the plasma treatment improves the surface wettability of the polyethylene film, but the study only adopts single plasma treatment as a surface modification means, a chemical bonding layer is not introduced, and the adhesive force stability of the coating in long-term storage is not fully verified. The traditional polyethylene film has a plurality of inherent defects that the oxygen transmittance is high, the oxidation corrosion of external oxygen to food is difficult to effectively block, the ultraviolet radiation has almost no blocking capability to ultraviolet rays, the ultraviolet radiation can directly penetrate through a film layer to irradiate the surface of the food, chlorophyll decomposition and lipid oxidation are accelerated, the film does not have any antibacterial and antioxidant activity, and the propagation of microorganisms in the food storage process can not be inhibited. These drawbacks make it difficult to meet the stringent demands of fresh fruits and vegetables on a high quality fresh-keeping environment by relying only on polyethylene films. Chitosan is natural cationic polysaccharide obtained by deacetylation treatment of chitin, and has good film forming property, biocompatibility and biodegradability. The protonated amino group on the chitosan molecular chain can generate electrostatic interaction with the phospholipid bilayer of the microbial cell membrane, thereby showing certain antibacterial activity. Cheng Long et al (Chinese plastics, 2021,35 (4): 35-41) studied the effect of chitosan on the properties of corn starch edible films, and the results indicate that the tensile strength of a single chitosan film is lower and the mechanical properties can not meet the actual packaging requirements. The chitosan/corn starch crosslinked film prepared by Vaseline et al (China plastics, 2024,38 (7): 38-42) has limited antioxidant capacity although the mechanical properties are improved. Tannic acid is a natural polyphenol compound, contains a large number of phenolic hydroxyl groups in the molecule, has excellent free radical scavenging capability and ultraviolet absorption property, and can form a crosslinked network with amino groups of chitosan through hydrogen bonds and covalent bonds. Lee et al (FoodHydrololoids, 2023, 136:108249) report that chitosan/tannic acid composite films were prepared by neutralization under different pH conditions, and the resulting composite films had excellent UV resistance, oxidation resistance and antibacterial properties, confirming the feasibility of tannic acid cross-linking with chitosan. However, the composite film is independently formed into a film by a solution casting method, and the mechanical strength is insufficient to meet the requirement of actual package on the tensile strength of the film. Shalma et al (InternationalJournalofBiologicalMacromolecules, 2024, 260:129317) report that crosslinking a chitosan-guar composite film with tannic acid further demonstrates that tannic acid crosslinking can improve mechanical properties, but the film is also a stand-alone film forming system, lacking compositing with commercial polyethylene substrates. In the prior art, the report that chitosan or coating liquid containing polyphenol substances is directly coated on the surface of a polyethylene film is that the polyethylene surface treatment mode is single corona discharge or plasma treatment. The oxygen-containing polar groups introduced by the single surface treatment are extremely easy to age and attenuate in air, and the bonding strength between the coating and the polyethylene substrate is obviously reduced along with the extension of the storage time. In addition, qiao et al (LWT, 2021, 135:109984) studied the effect of different acid solvents on the properties of chitosan films, and as a result showed that both the mechanical properties and barrier properties of chitosan films were limited when acetic acid was used as a solvent, whereas polyacid solvents such as citric acid were expected to improve the coating properties by participating in the crosslinking reaction, but the study was limited to independent chitosan film systems and did not involve compounding with polyethylene substrates. Therefore, how to improve the long-term inte