High-barrier-property food packaging film material based on natural polysaccharide and preparation process of high-barrier-property food packaging film material

Abstract

The invention discloses a high-barrier-property food packaging film material based on natural polysaccharide and a preparation process thereof, belongs to the technical field of food packaging materials, and aims to solve the technical problem that the barrier property, the mechanical property and the antibacterial property of a food packaging film in the prior art need to be further improved. The preparation method comprises the following steps: uniformly mixing a guar gum aqueous solution and a polyglycerol fatty acid ester ethanol solution, then respectively adding a cellulose acetate acetone solution, a suspension colloid and a membrane casting solution, uniformly mixing again, finally adding carboxylated cellulose nanofibers, stirring, defoaming, coating into a mold by using a coating method, drying, and stripping to obtain the membrane. According to the high-barrier-property food packaging film and the preparation method thereof, the barrier property, the mechanical property and the antibacterial property of the prepared high-barrier-property food packaging film are further improved through the prepared modified chitosan, the prepared suspended colloid and the prepared film casting solution.

Description

Technical Field

[0001] This invention relates to the field of food packaging materials technology, specifically to high-barrier food packaging film materials based on natural polysaccharides and their preparation process. Background Technology

[0002] Food packaging film is a key material in the food industry. Its barrier properties, mechanical properties, and antibacterial properties directly affect the storage quality and shelf life of food. Traditional food packaging films are mostly made of petroleum-based synthetic polymer materials. Although these materials have certain barrier properties and mechanical strength, they are difficult to degrade and easily cause environmental pollution, which is not in line with the current trend of green and environmentally friendly development.

[0003] To address these issues, researchers have begun focusing on the development of natural polysaccharide-based food packaging films. Natural polysaccharides are widely available, biocompatible, and completely biodegradable. However, pure natural polysaccharide films have significant drawbacks. Their molecular chains have weak intermolecular forces, resulting in poor mechanical properties and brittleness. Furthermore, polysaccharide films contain numerous pores and hydrophilic groups, leading to poor water vapor and gas barrier properties, making them unsuitable for packaging high-moisture and easily oxidized foods. In addition, natural polysaccharide-based packaging films typically lack antibacterial activity, failing to inhibit microbial growth during food storage and limiting their application in fresh and ready-to-eat foods.

[0004] Therefore, developing a natural polysaccharide-based food packaging film that combines excellent mechanical strength, high barrier properties, and long-lasting antibacterial properties has become a pressing technical challenge in the food packaging industry. To address this, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a high-barrier food packaging film material based on natural polysaccharides and its preparation process, in order to solve the technical problem that the barrier properties, mechanical properties and antibacterial properties of food packaging films in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a preparation process for a high-barrier food packaging film material based on natural polysaccharides, comprising the following steps:

[0007] S1. Add guar gum aqueous solution and polyglycerol fatty acid ester ethanol solution to the reaction vessel, stir at 20-30℃ for 10-20 min, then add cellulose acetate acetone solution, stir for 2-3 h, then add suspension colloid and casting solution respectively, stir for 30-50 min to obtain initial mixed composite film forming solution.

[0008] S2. Add carboxylated cellulose nanofibers to the initial mixed film-forming solution, stir for 1-2 hours, degas, and coat it onto a polymethyl methacrylate mold using a coating method, controlling the thickness to be 20-40 μm. After drying for 2-4 hours, peel it off to obtain a high-barrier food packaging film.

[0009] Furthermore, in step S1, the mass fraction of the guar gum aqueous solution is 2%, the mass fraction of the cellulose acetate acetone solution is 3%, the mass fraction of the polyglycerol fatty acid ester ethanol solution is 1%, and the volume ratio of the guar gum aqueous solution, polyglycerol fatty acid ester ethanol solution, cellulose acetate acetone solution, suspension colloid, and casting solution is 50mL:1mL:24-28mL:55-65mL:35-45mL.

[0010] Furthermore, in step S2, the ratio of the initial mixed composite film-forming solution to carboxylated cellulose nanofibers is 100mL:0.16-0.2g. The degassing operation is as follows: the film-forming solution is placed in a vacuum drying oven and degassed for 15-20 minutes at 0.08-0.1MPa. The drying operation is as follows: drying is carried out in a ventilated environment with a relative humidity of 40-60% and a temperature of 20-30℃ using a parallel laminar flow velocity of 1.5-2.5m / s.

[0011] Furthermore, the method for preparing the suspended colloid is as follows: modified chitosan is added to a reaction vessel containing an aqueous acetic acid solution, and stirred at 20-30°C until the modified chitosan is completely dissolved. Then, an aqueous polyvinyl alcohol solution is added, and stirring is continued for 10-12 hours. After the reaction is completed, the suspended colloid is obtained.

[0012] Furthermore, the acetic acid aqueous solution has a mass fraction of 2%, the polyvinyl alcohol aqueous solution has a mass fraction of 2.5%, and the ratio of the modified chitosan, acetic acid aqueous solution, and polyvinyl alcohol aqueous solution is 1g:60-70mL:30-34mL.

[0013] Furthermore, the modified chitosan is prepared by the following steps:

[0014] A1. Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to a reaction vessel containing 2-morpholinoethanesulfonic acid buffer solution, stir for 2-3 min, then add phenolic acid ethanol solution, continue stirring for 5-8 min, then add N-hydroxysuccinimide, and stir for 40-60 min under ice bath conditions at 0-4℃ to obtain a mixed solution;

[0015] A2. Add chitosan to a reaction vessel containing acetic acid solution. Stir at 20-30℃ until the chitosan is completely dissolved. Slowly add the mixed solution dropwise. After the addition is complete, react at 20-30℃ in the dark for 10-12 hours. After the reaction is complete, transfer the mixture to a dialysis bag with a molecular weight cutoff of 14 kDa. Dialyze with distilled water for 72 hours. Centrifuge at 8000-10000 x g for 20-30 minutes at 4℃. Collect the supernatant and freeze-dry at -40℃ for 24 hours to obtain modified chitosan.

[0016] Further, in step A1, the ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 2-morpholine ethanesulfonic acid buffer, phenolic acid ethanol solution, and N-hydroxysuccinimide is 1.4g:20mL:5mL:0.8-0.9g, the phenolic acid ethanol solution has a mass fraction of 5%, and the concentration of 2-morpholine ethanesulfonic acid buffer is 0.1mol / L.

[0017] Furthermore, in step A2, the ratio of chitosan, acetic acid solution, and mixed solution is 1g:20mL:28-32mL, and the mass fraction of the acetic acid solution is 0.5%.

[0018] Furthermore, the preparation method of the casting solution is as follows: add κ-carrageenan aqueous solution and konjac glucomannan aqueous solution to a reaction vessel, stir at 20-30℃ for 20-30 min, then add nano-silica, stir at 20-30℃ for 30-50 min to obtain the casting solution; the mass fraction of the κ-carrageenan aqueous solution is 2%, the mass fraction of the konjac glucomannan aqueous solution is 2%, and the ratio of the amount of κ-carrageenan aqueous solution, konjac glucomannan aqueous solution and nano-silica is 50mL:50mL:0.06-0.1g.

[0019] Furthermore, the high-barrier food packaging film material is prepared using the aforementioned preparation process for high-barrier food packaging film materials based on natural polysaccharides.

[0020] The present invention has the following beneficial effects:

[0021] 1. The modified chitosan of this invention, after phenolic acid grafting modification, introduces a large number of polar groups such as phenolic hydroxyl groups and carboxyl groups into the molecular chain. These groups form strong hydrogen bonds with the hydroxyl groups of polyvinyl alcohol in the suspension colloid, constructing a stable three-dimensional network molecular complex system. κ-carrageenan and konjac glucomannan in the casting solution form a polysaccharide interpenetrating network. Nano-silica fills the gaps in the network in the form of nanoparticles, playing a physical reinforcing role. When the three are mixed in the film-forming solution, the hydrogen bond network of modified chitosan-polyvinyl alcohol and the polysaccharide interpenetrating network become entangled. The hydrogen bond adsorption between nano-silica and each component further strengthens the interfacial bonding force. Combined with the doping of carboxylated cellulose nanofibers, a dense network structure with inorganic-organic synergy is finally formed, significantly improving the tensile strength of the film.

[0022] 2. The hydrogen bond network formed by the polar groups on the modified chitosan molecular chain and the hydroxyl groups of polyvinyl alcohol in the suspended colloid of this invention can reduce the porosity and defects inside the film. The polysaccharide interpenetrating network in the casting solution can increase the permeation path of water vapor and gas molecules through the tight arrangement of molecular chains. The physical filling effect of nano-silica further blocks the molecular permeation channels. When the three work together, the hydrogen bond network of modified chitosan-polyvinyl alcohol and the polysaccharide interpenetrating network intertwine, greatly improving the compactness of the film structure. At the same time, the combination of nano-silica with each component can effectively hinder the transport of water vapor and gas molecules, thereby reducing the water vapor permeability and gas permeability of the film and achieving excellent barrier performance.

[0023] 3. The phenolic acid groups grafted onto the modified chitosan of this invention have natural antibacterial activity. The amino groups of the chitosan molecules themselves can also exert antibacterial effects by disrupting the cell membranes of microorganisms. The three-dimensional network structure of the suspension colloid can load and fix the modified chitosan, preventing the loss of antibacterial components and prolonging the antibacterial effect. The polysaccharide interpenetrating network formed by the casting solution can serve as a carrier for antibacterial components, allowing antibacterial sites to be evenly distributed inside and on the surface of the film. When the three work synergistically, the dual antibacterial sites provided by the modified chitosan, after being dispersed and fixed by the suspension colloid and the casting solution, can act evenly on microorganisms. This synergistic effect greatly enhances the inhibitory effect of the film on Staphylococcus aureus and Escherichia coli, giving the film excellent and long-lasting antibacterial properties. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In this application, cellulose acetate was selected from Wuhan Kemike Biomedical Technology Co., Ltd., CAS No. 9035-69-2, with a purity of 99%;

[0026] In this application, the polyvinyl alcohol is selected from Wen'an County Juke Technology Co., Ltd., with a degree of alcoholysis of 88%;

[0027] In this application, the carboxylated cellulose nanofibers are selected from Shenzhen Qihong New Materials Co., Ltd., CAS No. 9004-34-6, model CNF-CP99;

[0028] In this application, chitosan is selected from Shaanxi Chenming Biotechnology Co., Ltd., CAS No. 9012-76-4;

[0029] In this application, κ-carrageenan is selected from Shandong Siyang Biotechnology Co., Ltd., CAS No. 11114-20-8;

[0030] In this application, the konjac glucomannan is selected from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., CAS No. 37220-17-0, and has a content of 95%.

[0031] In this application, the nano-silica is selected from Lingshou County Zhengxu Mineral Products Processing Plant, CAS No. 10279-57-9, with a mesh size of 20,000.

[0032] Example 1

[0033] This embodiment provides a preparation process for a high-barrier food packaging film material based on natural polysaccharides, including the following steps:

[0034] S1. Preparation of modified chitosan

[0035] Weigh 14g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and add it to a reaction vessel containing 200mL of 0.1mol / L 2-morpholinoethanesulfonic acid buffer. After stirring for 2min, add 50mL of 5wt% phenolic acid ethanol solution and continue stirring for 5min. Then add 8g of N-hydroxysuccinimide and stir for 40min under ice bath conditions at 0℃ to obtain a mixed solution.

[0036] Weigh 10g of chitosan and add it to a reaction vessel containing 200mL of 0.5wt% acetic acid solution. Stir at 20℃ until the chitosan is completely dissolved. Then, slowly add 280mL of the mixed solution dropwise. After the addition is complete, react at 20℃ in the dark for 10h. After the reaction is complete, transfer the solution to a dialysis bag with a molecular weight cutoff of 14kDa. Dialyze with distilled water for 72h. Centrifuge at 8000xg for 20min at 4℃. Collect the supernatant and freeze-dry at -40℃ for 24h to obtain modified chitosan.

[0037] During the reaction, under the stable environment of 2-morpholine ethanesulfonic acid buffer, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride first activates the carboxyl group of phenolic acid to form an unstable intermediate, which is then stabilized by N-hydroxysuccinimide to generate N-hydroxysuccinimide-phenolic acid activated ester, achieving efficient activation of the phenolic acid carboxyl group. Then, under the mediation of acetic acid solution, chitosan is fully dissolved and protonated. The slowly added activated ester undergoes a nucleophilic substitution reaction with the amino groups on the chitosan molecular chain, and the phenolic acid is covalently grafted onto the chitosan molecular chain through amide bonds. The grafting is completed under light-proof and constant temperature conditions, and finally modified chitosan is obtained.

[0038] S2. Preparation of suspension colloids

[0039] Weigh 5g of modified chitosan and add it to a reaction vessel containing 300mL of 2wt% acetic acid aqueous solution. Stir at 20℃ until the modified chitosan is completely dissolved. Then add 150mL of 2.5wt% polyvinyl alcohol aqueous solution and continue stirring for 10h. After the reaction is completed, a suspension colloid is obtained.

[0040] During the reaction, the modified chitosan is uniformly dispersed and dissolved in the acetic acid aqueous solution due to the electrostatic repulsion of the amino protonation and the hydrogen bonding between the polar groups and water molecules. Polyvinyl alcohol is fully swollen and dispersed in its aqueous solution through hydrogen bonding between the hydroxyl groups and water molecules. After mixing the two and stirring thoroughly, the hydroxyl, carboxyl, and amino groups of the modified chitosan and the hydroxyl groups of polyvinyl alcohol form intermolecular hydrogen bonds. Combined with electrostatic attraction and physical entanglement of the two polymer chains, a three-dimensional network molecular complex system is formed, ultimately constructing a uniform and stable modified chitosan-polyvinyl alcohol composite aqueous suspension colloid.

[0041] S3. Preparation of casting solution

[0042] Weigh out 500 mL of 2 wt% κ-carrageenan aqueous solution and 500 mL of 2 wt% konjac glucomannan aqueous solution and add them to the reaction vessel. Stir at 20°C for 20 min. Then add 0.6 g of nano-silica and stir at 20°C for 30 min to obtain the casting solution.

[0043] During the reaction, when the κ-carrageenan aqueous solution and an equal volume of konjac glucomannan aqueous solution are mixed and stirred, the anionic sulfate groups and hydroxyl groups of the κ-carrageenan form intermolecular hydrogen bonds with the hydroxyl groups on the konjac glucomannan molecular chains. At the same time, the linear anionic polysaccharide chains of carrageenan and the long glucomannan chains of konjac glucomannan intertwine to form a stable polysaccharide interpenetrating network structure. Then, when nano-silica is added to the homogeneous polysaccharide solution, a large number of hydroxyl groups on the surface of the nano-silica further form hydrogen bonds with the hydroxyl groups in the polysaccharide network. The nano-silica is dispersed in the continuous polysaccharide phase in the form of nano-sized particles and is embedded in the gaps between the polysaccharide molecular chains through physical filling, thus obtaining the casting solution.

[0044] S4. Preparation of initial mixed composite film-forming solution

[0045] Weigh out 50 mL of 2 wt% guar gum aqueous solution and 1 mL of 1 wt% polyglycerol fatty acid ester ethanol solution and add them to the reaction vessel. Stir at 20°C for 10 min, then add 24 mL of 3 wt% cellulose acetate acetone solution and stir for 2 h. Then add 55 mL of suspension colloid and 35 mL of casting solution and stir for 30 min to obtain the initial mixed composite film forming solution.

[0046] During the reaction, the emulsifying effect of polyglycerol fatty acid esters and the miscibility of ethanol and water are first utilized to form a hydrophilic-alcoholic homogeneous phase between guar gum aqueous solution and polyglycerol fatty acid ester ethanol solution. Then, the interfacial association of the emulsifier achieves three-phase uniform emulsification and dispersion with the cellulose acetate acetone organic phase. Finally, two types of hydrophilic systems, suspension colloid and casting solution, are added. Through intermolecular hydrogen bonds, electrostatic attraction, and physical entanglement between various natural polysaccharides and polymeric auxiliaries, as well as the hydrogen bond adsorption between nano-silica and polymers, a three-dimensional network molecular framework is constructed, achieving molecular-level uniform dispersion of all components and stable existence of nanofillers, ultimately forming a homogeneous and stable initial mixed composite film-forming solution.

[0047] S5. Preparation of high-barrier food packaging film

[0048] Weigh 1000 mL of initial mixed composite film-forming solution and add 1.6 g of carboxylated cellulose nanofibers. After stirring for 1 h, place the film-forming solution in a vacuum drying oven and degas for 15 min at 0.08 MPa. Coat the solution onto a polymethyl methacrylate mold using a coating method, controlling the thickness to 20 μm. After 2 h of operation in a ventilated environment with a relative humidity of 40% and a temperature of 20℃, peel off the film to obtain a high-barrier food packaging film.

[0049] During the reaction, the introduction of carboxylated cellulose nanofibers allows them to form hydrogen bonds and electrostatic interactions with the components in the film-forming solution, constructing a multi-level dense network structure with nano-silica in an inorganic-organic nanosynergy. After vacuum degassing to eliminate defects such as bubbles and micropores in the system, a liquid film of uniform thickness is formed by coating. Then, the solvent is evaporated by drying, which further strengthens the non-covalent interactions between molecules during the gradual shaping process of the film, completing the structural densification. Finally, a high-barrier food packaging film is obtained by peeling.

[0050] Example 2

[0051] This embodiment provides a preparation process for a high-barrier food packaging film material based on natural polysaccharides, including the following steps:

[0052] S1. Preparation of modified chitosan

[0053] Weigh 14g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and add it to a reaction vessel containing 200mL of 0.1mol / L 2-morpholinoethanesulfonic acid buffer. After stirring for 2min, add 50mL of 5wt% phenolic acid ethanol solution and continue stirring for 6min. Then add 8.5g of N-hydroxysuccinimide and stir for 50min in an ice bath at 2℃ to obtain a mixed solution.

[0054] Weigh 10g of chitosan and add it to a reaction vessel containing 200mL of 0.5wt% acetic acid solution. Stir at 25℃ until the chitosan is completely dissolved. Then, slowly add 300mL of the mixed solution dropwise. After the addition is complete, react at 25℃ in the dark for 11h. After the reaction is complete, transfer the solution to a dialysis bag with a molecular weight cutoff of 14kDa. Dialyze with distilled water for 72h. Centrifuge at 9000xg for 25min at 4℃. Collect the supernatant and freeze-dry at -40℃ for 24h to obtain modified chitosan.

[0055] S2. Preparation of suspension colloids

[0056] Weigh 5g of modified chitosan and add it to a reaction vessel containing 320mL of 2wt% acetic acid aqueous solution. Stir at 25℃ until the modified chitosan is completely dissolved. Then add 160mL of 2.5wt% polyvinyl alcohol aqueous solution and continue stirring for 11h. After the reaction is completed, a suspension colloid is obtained.

[0057] S3. Preparation of casting solution

[0058] Weigh out 500 mL of 2 wt% κ-carrageenan aqueous solution and 500 mL of 2 wt% konjac glucomannan aqueous solution and add them to the reaction vessel. Stir at 25 °C for 25 min. Then add 0.8 g of nano silica and stir at 25 °C for 40 min to obtain the casting solution.

[0059] S4. Preparation of initial mixed composite film-forming solution

[0060] Weigh out 50 mL of 2 wt% guar gum aqueous solution and 1 mL of 1 wt% polyglycerol fatty acid ester ethanol solution and add them to the reaction vessel. Stir at 25°C for 15 min, then add 26 mL of 3 wt% cellulose acetate acetone solution and stir for 2.5 h. Then add 60 mL of suspension colloid and 40 mL of casting solution and stir for 40 min to obtain the initial mixed composite film forming solution.

[0061] S5. Preparation of high-barrier food packaging film

[0062] Weigh 1000 mL of initial mixed composite film-forming solution and add 1.8 g of carboxylated cellulose nanofibers. Stir for 1.5 h and place the film-forming solution in a vacuum drying oven. Degas at 0.09 MPa for 18 min and coat it onto a polymethyl methacrylate mold using a coating method. Control the thickness to 30 μm. In a ventilated environment with a relative humidity of 50% and a temperature of 25℃, peel it off after 3 h using a parallel laminar flow velocity of 2 m / s to obtain a high-barrier food packaging film.

[0063] Example 3

[0064] This embodiment provides a preparation process for a high-barrier food packaging film material based on natural polysaccharides, including the following steps:

[0065] S1. Preparation of modified chitosan

[0066] Weigh 14g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and add it to a reaction vessel containing 200mL of 0.1mol / L 2-morpholinoethanesulfonic acid buffer. After stirring for 3min, add 50mL of 5wt% phenolic acid ethanol solution and continue stirring for 8min. Then add 9g of N-hydroxysuccinimide and stir for 60min in an ice bath at 4℃ to obtain a mixed solution.

[0067] Weigh 10g of chitosan and add it to a reaction vessel containing 200mL of 0.5wt% acetic acid solution. Stir at 30℃ until the chitosan is completely dissolved. Then, slowly add 320mL of the mixed solution dropwise. After the addition is complete, react at 30℃ in the dark for 12h. After the reaction is complete, transfer the solution to a dialysis bag with a molecular weight cutoff of 14kDa. Dialyze with distilled water for 72h. Centrifuge at 10000xg for 30min at 4℃. Collect the supernatant and freeze-dry at -40℃ for 24h to obtain modified chitosan.

[0068] S2. Preparation of suspension colloids

[0069] Weigh 5g of modified chitosan and add it to a reaction vessel containing 350mL of 2wt% acetic acid aqueous solution. Stir at 30℃ until the modified chitosan is completely dissolved. Then add 170mL of 2.5wt% polyvinyl alcohol aqueous solution and continue stirring for 12h. After the reaction is completed, a suspension colloid is obtained.

[0070] S3. Preparation of casting solution

[0071] Weigh out 500 mL of 2 wt% κ-carrageenan aqueous solution and 500 mL of 2 wt% konjac glucomannan aqueous solution and add them to the reaction vessel. Stir at 30°C for 30 min. Then add 1 g of nano-silica and stir at 30°C for 50 min to obtain the casting solution.

[0072] S4. Preparation of initial mixed composite film-forming solution

[0073] Weigh out 50 mL of 2 wt% guar gum aqueous solution and 1 mL of 1 wt% polyglycerol fatty acid ester ethanol solution and add them to the reaction vessel. Stir at 30°C for 20 min, then add 28 mL of 3 wt% cellulose acetate acetone solution and stir for 3 h. Then add 65 mL of suspension colloid and 45 mL of casting solution and stir for 50 min to obtain the initial mixed composite film forming solution.

[0074] S5. Preparation of high-barrier food packaging film

[0075] Weigh 1000 mL of initial mixed composite film-forming solution and add 2 g of carboxylated cellulose nanofibers. Place the film-forming solution in a vacuum drying oven and degas at 0.1 MPa for 20 min. Coat the solution onto a polymethyl methacrylate mold using a coating method, controlling the thickness to 40 μm. After 4 h in a ventilated environment with a relative humidity of 60% and a temperature of 30℃, peel off the film using a parallel laminar flow velocity of 2.5 m / s to obtain a high-barrier food packaging film.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 3 is that step S1 is omitted, and the chitosan in step S1 is used instead of the modified chitosan in step S2.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 3 is that steps S1 and S2 are omitted, and the chitosan in step S1 is used to replace the suspension colloid in step S4.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 3 is that step S3 is omitted, and the casting solution in step S4 is replaced with nano-silica from step S3.

[0082] Performance testing:

[0083] The tensile strength of the high-barrier food packaging films prepared in Examples 1-3 and Comparative Examples 1-3 was determined in accordance with the standard GB / T 1040.1-2018 "Determination of tensile properties of plastics - Part 1: General".

[0084] The water vapor transmission rate of the high-barrier food packaging films prepared in Examples 1-3 and Comparative Examples 1-3 was determined according to the standard GB / T 1037-2021 "Determination of Water Vapor Transmission Performance of Plastic Films and Sheets - Cup Weight Gain and Weight Loss Method".

[0085] The gas permeability of the high-barrier food packaging films prepared in Examples 1-3 and Comparative Examples 1-3 was determined in accordance with the standard GB / T 1038.1-2022 "Test methods for gas permeability of plastic films and sheets - Part 1: Differential pressure method".

[0086] The antibacterial rates of the high-barrier food packaging films prepared in Examples 1-3 and Comparative Examples 1-3 were determined according to standard GB / T 31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials". The specific test results are shown in Table 1 below:

[0087] Data Analysis:

[0088] Comparative analysis of the data in Table 1 above shows that the high-barrier food packaging film prepared by this invention has a tensile strength of 15.95 MPa and a water vapor transmission rate of 12.44 g / (m²). 2 (24h), gas permeability is 2.55×10 5 (cm) 3 / (m 2 (·d·Pa), the anti-Staphylococcus aureus rate was 96.64%, and the anti-Escherichia coli rate was 95.22%;

[0089] Comparative Example 1 used unmodified chitosan to prepare a suspension colloid. Unmodified chitosan lacked the polar groups introduced by phenolic acid grafting, significantly weakening the hydrogen bonding with polyvinyl alcohol. This reduced the stability of the three-dimensional network molecular complex system, resulting in a decrease in its tensile strength to 11.72 MPa. Simultaneously, the film structure lacked density, with increased porosity and defects, leading to an increase in water vapor permeability to 13.56 g / (m²). 2 (24h), the gas permeability also increased to 2.77×10 5 (cm) 3 / (m 2Furthermore, unmodified chitosan relies solely on its own amino groups to exert its antibacterial effect, lacking the synergistic antibacterial effect of phenolic acid groups. Ultimately, the anti-Staphylococcus aureus rate decreased to 89.34%, and the anti-Escherichia coli rate decreased to 87.80%.

[0090] Comparative Example 2 used unmodified chitosan to replace the suspension colloid. This resulted in the loss of the supporting effect of the modified chitosan-polyvinyl alcohol hydrogen bond network on the film structure. A stable three-dimensional network framework could not be formed inside the film, leading to a significant reduction in the compatibility and binding force between the components. This resulted in a decrease in tensile strength to 10.45 MPa. Numerous pores and defects formed inside the film, significantly reducing the resistance to water vapor and gas molecule permeation, thus increasing the water vapor permeation rate to 14.75 g / (m³). 2 (24h), gas permeability increased to 3.03×10 5 (cm) 3 / (m 2 Meanwhile, the antibacterial components could not be evenly dispersed and fixed, the number of antibacterial sites decreased and the effect weakened, ultimately reducing the anti-Staphylococcus aureus rate to 79.69% and the anti-Escherichia coli rate to 78.29%.

[0091] Comparative Example 3, where nano-silica directly replaced the casting solution, lost the polysaccharide interpenetrating network formed by κ-carrageenan and konjac glucomannan. The nano-silica could not be uniformly dispersed in the system; instead, it agglomerated, creating localized defects and failing to provide effective physical filling and reinforcement. This resulted in a decrease in tensile strength to 11.13 MPa. Furthermore, the lack of the polysaccharide interpenetrating network's effect on extending molecular permeation pathways meant that the agglomerated nano-silica could not effectively block permeation channels, leading to an increase in water vapor permeation to 14.13 g / (m³). 2 (24h), gas permeability increased to 2.90×10 5 (cm) 3 / (m 2 The lack of casting solution led to a reduction in the carrier of antibacterial components and a decrease in the uniformity of antibacterial site distribution, ultimately reducing the anti-Staphylococcus aureus rate to 83.96% and the anti-Escherichia coli rate to 82.22%.

[0092] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A preparation process for high-barrier food packaging film materials based on natural polysaccharides, characterized in that, Includes the following steps: S1. Add guar gum aqueous solution and polyglycerol fatty acid ester ethanol solution to the reaction vessel, stir at 20-30℃ for 10-20 min, then add cellulose acetate acetone solution, stir for 2-3 h, then add suspension colloid and casting solution respectively, stir for 30-50 min to obtain initial mixed composite film forming solution. S2. Add carboxylated cellulose nanofibers to the initial mixed film-forming solution, stir for 1-2 hours, degas, and coat it onto a polymethyl methacrylate mold using a coating method, controlling the thickness to be 20-40 μm. After drying for 2-4 hours, peel it off to obtain a high-barrier food packaging film.

2. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 1, characterized in that, In step S1, the mass fraction of the guar gum aqueous solution is 2%, the mass fraction of the cellulose acetate acetone solution is 3%, the mass fraction of the polyglycerol fatty acid ester ethanol solution is 1%, and the volume ratio of the guar gum aqueous solution, polyglycerol fatty acid ester ethanol solution, cellulose acetate acetone solution, suspension colloid, and casting solution is 50mL:1mL:24-28mL:55-65mL:35-45mL.

3. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 1, characterized in that, In step S2, the ratio of the initial mixed composite film-forming solution to carboxylated cellulose nanofibers is 100mL:0.16-0.2g. The degassing operation is as follows: the film-forming solution is placed in a vacuum drying oven and degassed for 15-20 minutes at 0.08-0.1MPa. The drying operation is as follows: in a ventilated environment with a relative humidity of 40-60% and a temperature of 20-30℃, drying is carried out using a parallel laminar flow velocity of 1.5-2.5m / s.

4. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 1, characterized in that, The method for preparing the suspended colloid is as follows: Modified chitosan is added to a reaction vessel containing an aqueous acetic acid solution, and stirred at 20-30°C until the modified chitosan is completely dissolved. Then, an aqueous polyvinyl alcohol solution is added, and stirring is continued for 10-12 hours. After the reaction is completed, the suspended colloid is obtained.

5. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 4, characterized in that, The acetic acid aqueous solution has a mass fraction of 2%, the polyvinyl alcohol aqueous solution has a mass fraction of 2.5%, and the ratio of the modified chitosan, acetic acid aqueous solution, and polyvinyl alcohol aqueous solution is 1g:60-70mL:30-34mL.

6. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 4, characterized in that, The modified chitosan was prepared by the following steps: A1. Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to a reaction vessel containing 2-morpholinoethanesulfonic acid buffer solution, stir for 2-3 min, then add phenolic acid ethanol solution, continue stirring for 5-8 min, then add N-hydroxysuccinimide, and stir for 40-60 min under ice bath conditions at 0-4℃ to obtain a mixed solution; A2. Add chitosan to a reaction vessel containing acetic acid solution, stir at 20-30℃ until the chitosan is completely dissolved, then slowly add the mixed solution dropwise. After the addition is complete, react at 20-30℃ in the dark for 10-12 hours, and then perform post-treatment to obtain modified chitosan.

7. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 6, characterized in that, In step A1, the ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 2-morpholine ethanesulfonic acid buffer, phenolic acid ethanol solution, and N-hydroxysuccinimide is 1.4g:20mL:5mL:0.8-0.9g, the phenolic acid ethanol solution has a mass fraction of 5%, and the 2-morpholine ethanesulfonic acid buffer solution has a concentration of 0.1mol / L.

8. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 6, characterized in that, In step A2, the ratio of chitosan, acetic acid solution, and mixed solution is 1g:20mL:28-32mL, and the mass fraction of the acetic acid solution is 0.5%.

9. The preparation process of the high-barrier food packaging film material based on natural polysaccharides according to claim 1, characterized in that, The casting solution is prepared as follows: κ-carrageenan aqueous solution and konjac glucomannan aqueous solution are added to a reaction vessel and stirred at 20-30℃ for 20-30 min. Then, nano-silica is added and stirred at 20-30℃ for 30-50 min to obtain the casting solution. The mass fraction of the κ-carrageenan aqueous solution is 2%, and the mass fraction of the konjac glucomannan aqueous solution is 2%. The ratio of the amount of κ-carrageenan aqueous solution, konjac glucomannan aqueous solution, and nano-silica is 50 mL:50 mL:0.06-0.1 g.

10. A high-barrier food packaging film material based on natural polysaccharides, characterized in that, The high-barrier food packaging film material based on natural polysaccharides is prepared using the preparation process of the high-barrier food packaging film material based on natural polysaccharides as described in any one of claims 1-9.

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