Responsive bacteriostatic / modified atmosphere double preservative paper and preparation process thereof

Abstract

The invention discloses response type bacteriostatic / controlled atmosphere double preservative paper, and aims to solve the problems that an existing preservative material is poor in bacteriostatic effect and insufficient in controlled atmosphere function. The preservative paper is prepared from a paper base material, Pickering emulsion, nano chitin and polyethylene glycol. The nanometer chitin is prepared through a specific technology, and the preservative paper is endowed with proper barrier performance and antibacterial performance. The Pickering emulsion realizes response to environmental humidity change by controlling release of an oil phase, so that gas permeability of the preservative paper and long-acting release of a bacteriostatic agent are adjusted. The preparation method comprises the following steps: preparing the nano chitin, preparing the Pickering emulsion, and sequentially coating the surface of the paper base material with the barrier layer coating liquid and the Pickering emulsion. The preservative paper prepared by the preparation method disclosed by the invention has dual functions of bacteriostasis and air conditioning, can effectively prolong the preservation period of food, and is environment-friendly. The preservative paper can be widely applied to the field of food packaging and has a good market prospect.

Description

Technical Field

[0001] The invention provides a responsive antibacterial / modified atmosphere dual fresh-keeping paper and a preparation process thereof, belonging to the technical field of packaging materials. Background Art

[0002] With the continuous advancement of food preservation technologies, consumers are placing higher demands on food quality and safety. Traditional preservation methods, such as the use of chemical preservatives and artificial additives, while able to extend food's shelf life to a certain extent, often pose potential risks to consumer health. Furthermore, these methods fail to meet the modern consumer demand for natural and healthy consumption. Therefore, the development of innovative, environmentally friendly food preservation technologies is of great practical significance.

[0003] Responsive antibacterial / modified atmosphere (MA) preservation technology is a novel food preservation technique based on the intersection of materials science and biotechnology. It aims to effectively inhibit bacteria and fungi by adjusting and optimizing the properties of preservative materials, while also providing a suitable modified atmosphere for food. These preservative materials are typically made from natural or synthetic polymers and exhibit excellent biocompatibility and low toxicity.

[0004] Nanochitoin, a novel biomaterial, has attracted widespread attention due to its excellent biocompatibility, antibacterial, and barrier properties. Nanochitoin, a chitosan derivative, can effectively support the application of fresh-keeping technologies in food packaging. Through rational preparation processes, its dispersibility can be optimized, and its barrier and antibacterial properties can be enhanced, thereby enhancing food preservation.

[0005] Furthermore, Pickering emulsion and polyethylene glycol, as key functional ingredients, offer excellent moisture retention and stability, significantly enhancing the overall performance of packaging materials. The former helps enhance the antibacterial properties of the coating, while polyethylene glycol improves the coating's softness, ductility, and gas permselectivity, adapting to diverse food needs.

[0006] Therefore, the development of a dual-purpose fresh-keeping paper that can effectively inhibit bacteria while maintaining a controlled atmosphere is an inevitable trend in the development of modern food preservation technology. This technology not only meets consumers' higher expectations for food safety and quality, but also promotes the sustainable development of the food industry. Summary of the Invention

[0007] The present invention relates to a responsive antibacterial / modified atmosphere dual-keeping paper, which is primarily composed of paper, Pickering emulsion, nano-chitin, and polyethylene glycol. The paper exhibits excellent antibacterial properties and a modified atmosphere preservation effect, making it suitable for packaging various foods, effectively extending their shelf life and maintaining their freshness and safety.

[0008] To achieve the purpose of the invention, the technical solution adopted by the present invention is: according to a responsive antibacterial / modified atmosphere dual fresh-keeping paper, the responsive antibacterial / modified atmosphere dual fresh-keeping paper is composed of: paper, Pickering emulsion, nano-chitin, polyethylene glycol;

[0009] The preparation process of the nano-chitosan comprises the following steps:

[0010] S1: Soaking chitosan powder in a 20-50 wt% NaOH solution, stirring mechanically at 600-800 rpm at 60-120° C., and fully reacting for 2-8 hours to ensure partial deacetylation; separating the solid and liquid phases of the reaction mixture through a vacuum filter, retaining the solid phase, and washing the solid phase with deionized water 5-10 times until the pH value of the washing solution reaches 7-7.5;

[0011] S2 disperses solid chitosan in distilled water, adds acetic acid solution to the chitosan dispersion by titration at a controlled drop rate of 0.5-0.8 mL / s, and adjusts the pH value of the mixture to 2.5-4.0 to prevent chitosan from agglomerating;

[0012] S3: placing the pH-adjusted chitosan suspension into a high-pressure homogenizer, setting the homogenization pressure to 200-400 MPa, and circulating the process 15-30 times. During the homogenization process, the temperature is maintained at 15-50° C. to avoid damage to the chitosan structure. After the homogenization process, the chitosan suspension is assisted by an ultrasonic processor, with the power set to 100-200 W and the frequency set to 40-60 kHz. The ultrasonic process is performed for 10-20 minutes to further disperse the chitosan particles.

[0013] S4 uses a rotary evaporator to concentrate the nano-chitosan suspension to a final solid content of 3 to 5 wt % to obtain nano-chitosan;

[0014] The preparation process of the Pickering emulsion comprises the following steps:

[0015] S5: dispersing the nano-chitosan suspension in deionized water, adding acetic acid to adjust the pH value of the solution to 3-5, stirring at 300-400 rpm for 30-60 minutes at 25-35° C.; ultrasonically treating the suspension at a power of 100-200 W for 10-20 minutes to form a uniformly dispersed nano-chitosan solution;

[0016] S6: Dissolve polyethylene glycol in deionized water, maintain the temperature at 50-60°C in a constant temperature water bath, and stir at 500-600 rpm for 40-60 minutes to ensure complete dissolution and avoid polyethylene glycol crystallization;

[0017] S7: mixing the treated nano-chitosan suspension with a polyethylene glycol solution, adding 0.1-0.3 wt% of an antioxidant, using a magnetic stirrer, controlling the stirring speed to 400-600 rpm, maintaining the temperature at 50-60° C., and stirring for 60-80 minutes; ultrasonically treating the mixed solution to promote molecular interface interaction, with a treatment power of 100-300 W and a treatment time of 15-30 minutes;

[0018] S8: placing the mixed liquid into a high-pressure homogenizer, controlling the pressure at 100-200 MPa, performing high-pressure homogenization treatment, and circulating the treatment for 15-30 times, while using a water bath for cooling to maintain the temperature at 20-30° C.; using a 0.35-0.45 μm filter membrane to filter impurities from the treated aqueous phase emulsion to ensure that the emulsion aqueous phase has no particle precipitation and is uniform and stable; obtaining the aqueous phase of the Pickering emulsion;

[0019] S9: adding the water phase and the oil phase of the Pickering emulsion into the emulsification reactor, and emulsifying for 30s to 600s at a temperature of 4 to 30°C and an emulsification speed of 3000 to 30000 rpm to obtain the Pickering emulsion.

[0020] According to a responsive antibacterial / modified atmosphere dual fresh-keeping paper, the polyethylene glycol is a combination of one or more of polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 10000, and polyethylene glycol 20000.

[0021] According to a responsive antibacterial / modified atmosphere dual fresh-keeping paper, the antioxidant described in S7 is a combination of one or more of vitamin C, 3,4,5-trihydroxybenzoic acid, tocopherol, and glutathione.

[0022] According to a responsive antibacterial / modified atmosphere dual fresh-keeping paper, the oil phase described in S9 is a combination of one or more plant essential oils such as rose essential oil, cinnamon essential oil, lemon essential oil, tea tree essential oil, peppermint essential oil, oregano essential oil, etc.

[0023] According to a preparation method of a responsive antibacterial / modified atmosphere dual fresh-keeping paper, the preparation method comprises the following steps:

[0024] S10: dissolving 50 to 1000 parts by weight of nano-chitin in deionized water to obtain a crude coating solution; defoaming the crude coating solution by ultrasonication, standing or centrifugation to obtain a barrier layer coating solution;

[0025] S11 uses a coating machine to apply the barrier layer coating liquid on the surface of the base paper, the thickness of the coating liquid is 0.1 to 5 mm, and then the base paper coated with the barrier layer coating liquid is dried at a drying temperature of 20 to 60°C; then the Pickering emulsion is applied again, the thickness of the coating liquid is 0.1 to 3 mm, and then the base paper coated with the Pickering emulsion coating liquid is dried at a drying temperature of 20 to 60°C to obtain a responsive antibacterial / modified atmosphere dual preservation paper.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) Dual preservation effect: This responsive antibacterial / modified atmosphere dual preservation paper combines antibacterial and modified atmosphere preservation technologies. It can reduce the growth of microorganisms while regulating the internal atmosphere of the package, extending the shelf life of food and effectively maintaining the freshness and flavor of food.

[0028] (2) Use of natural materials: The main ingredients used in this patent, such as nano-chitin, are all of natural origin, have high biocompatibility, strong safety, meet the health and environmental protection needs of modern consumers, and reduce dependence on synthetic chemical preservatives.

[0029] (3) Excellent antibacterial properties: Nanochitosan and essential oils exhibit good antibacterial effects, which can effectively inhibit the growth of various pathogenic microorganisms, reduce the risk of food spoilage, and thus improve food safety.

[0030] (4) Good barrier properties: The fresh-keeping paper can effectively block the transfer of moisture and gas, protect the food inside from the influence of the external environment, maintain its quality and taste, and delay oxidation reactions.

[0031] (5) Environmentally friendly: The use of natural and biodegradable materials reduces the burden on the environment, promotes the development and use of sustainable packaging materials, and helps to realize the concept of green production.

[0032] Figures in the specification

[0033] Figure 1 This is a rendering of the excellent antifungal properties of cling paper. DETAILED DESCRIPTION

[0034] Example 1

[0035] The chitosan powder was immersed in a 20 wt% NaOH solution and mechanically stirred at 600 rpm at 60°C for 2 hours to ensure deacetylation. The reaction mixture was separated into solid and liquid by vacuum filter, and the solid phase was retained. The solid phase was washed with deionized water 5 times until the pH value of the washing solution reached 7. The solid chitosan was dispersed in distilled water, and acetic acid solution was added to the chitosan dispersion by titration at a controlled drop rate of 0.5 mL / s. The pH value of the mixture was adjusted to 2.5 to avoid chitosan agglomeration. The chitosan suspension after pH adjustment was placed in a high-pressure homogenizer, the homogenization pressure was set to 200 MPa, and the process was circulated 15 times. The temperature was maintained at 15°C during the homogenization process to avoid damage to the chitosan structure. After the homogenization, the chitosan suspension was assisted by an ultrasonic processor with a power of 100 W and a frequency of 40 kHz. The ultrasonic treatment was performed for 10 minutes to further disperse the chitosan particles. The nano-chitosan suspension was concentrated using a rotary evaporator to a final solid content of 3 wt% to obtain nano-chitosan.

[0036] Example 2

[0037] The chitosan powder was immersed in a 35 wt% NaOH solution and mechanically stirred at 700 rpm at 100°C for 5 hours to ensure deacetylation. The reaction mixture was separated into solid and liquid by vacuum filtration, and the solid phase was retained. The solid phase was washed with deionized water 8 times until the pH value of the washing solution reached 7.2. The solid chitosan was dispersed in distilled water, and acetic acid solution was added to the chitosan dispersion by titration at a controlled drop rate of 0.6 mL / s. The pH value of the mixture was adjusted to 3 to prevent chitosan agglomeration. The chitosan suspension after pH adjustment was placed in a high-pressure homogenizer, the homogenization pressure was set to 300 MPa, and the process was circulated 25 times. The temperature was maintained at 30°C during the homogenization process to avoid damage to the chitosan structure. After the homogenization, the chitosan suspension was assisted by an ultrasonic processor with a power of 150 W and a frequency of 50 kHz. The ultrasonic treatment was performed for 15 minutes to further disperse the chitosan particles. The nano-chitosan suspension was concentrated using a rotary evaporator to a final solid content of 4 wt% to obtain nano-chitosan.

[0038] Example 3

[0039] Chitosan powder was immersed in a 50 wt% NaOH solution, mechanically stirred at 800 rpm at 120 ° C, and fully reacted for 8 hours to ensure deacetylation; the reaction mixture was separated into solid and liquid by vacuum filter, the solid phase was retained, and the solid phase was washed with deionized water 10 times until the pH value of the washing liquid reached 7.5; solid chitosan was dispersed in distilled water, and acetic acid solution was added to the chitosan dispersion by titration at a controlled drop rate of 0.8 mL / s to adjust the pH value of the mixture to 4.0 to avoid chitosan agglomeration; placing the pH-adjusted chitosan suspension in a high-pressure homogenizer, setting the homogenization pressure to 400 MPa, and circulating the treatment 30 times. During the homogenization process, the temperature was maintained at 50°C to avoid damage to the chitosan structure; after the homogenization, the chitosan suspension was assisted by an ultrasonic processor, with the power set to 200 W and the frequency set to 60 kHz, and the ultrasonic treatment was performed for 20 minutes to further disperse the chitosan particles; using a rotary evaporator, the nanochitosan suspension was concentrated to a final solid content of 5 wt% to obtain nanochitosan;

[0040] Example 4

[0041] The nano-chitosan suspension obtained in Example 1 was dispersed in deionized water, acetic acid was added to adjust the pH value of the solution to 3, and the mixture was stirred at 300 rpm for 30 minutes at 25°C; the suspension was ultrasonically treated at a power of 100 W for 10 minutes to form a uniformly dispersed nano-chitosan solution; polyethylene glycol was dissolved in deionized water, and the temperature was maintained at 50°C using a constant temperature water bath method, while stirring at 500 rpm for 40 minutes to ensure complete dissolution and avoid polyethylene glycol crystallization; the treated nano-chitosan suspension was mixed with the polyethylene glycol solution, and 0.1 wt% of an antioxidant was added, and the stirring speed was controlled at 400 rpm using a magnetic stirrer. rpm, and the temperature was maintained at 50°C for 60 minutes; the mixed solution was treated with ultrasound to promote molecular interface interaction, the processing power was 100W, and the processing time was 15 minutes; the mixed solution was placed in a high-pressure homogenizer, the pressure was controlled at 100MPa, and high-pressure homogenization treatment was carried out, and the treatment was circulated 15 times, and a water bath was used for cooling to keep the temperature at 20°C; the treated aqueous emulsion was filtered for impurities using a 0.35μm filter membrane to ensure that the aqueous phase of the emulsion had no particle precipitation and was uniform and stable; the aqueous phase of the Pickering emulsion was obtained; the aqueous phase and oil phase of the Pickering emulsion were added to the emulsification reactor, and emulsified for 30s at a temperature of 4°C and an emulsification speed of 3000rpm to obtain the Pickering emulsion.

[0042] Example 5

[0043] The nano-chitosan suspension obtained in Example 2 was dispersed in deionized water, acetic acid was added to adjust the pH value of the solution to 4, and the mixture was stirred at 350 rpm for 45 minutes at 30°C. The suspension was ultrasonically treated at a power of 150 W for 15 minutes to form a uniformly dispersed nano-chitosan solution. Polyethylene glycol was dissolved in deionized water, and the temperature was maintained at 55°C using a constant temperature water bath method. The mixture was stirred at 550 rpm for 50 minutes to ensure complete dissolution and avoid crystallization of polyethylene glycol. The treated nano-chitosan suspension was mixed with the polyethylene glycol solution, and 0.2 wt% of an antioxidant was added. The mixture was stirred at a speed of 500 rpm using a magnetic stirrer. pm, the temperature is maintained at 55°C and stirred for 70 minutes; the mixed solution is treated with ultrasound to promote molecular interface interaction, the processing power is 200w, and the processing time is 20 minutes; the mixed solution is placed in a high-pressure homogenizer, the pressure is controlled at 150MPa, and high-pressure homogenization treatment is carried out, and the treatment is circulated 20 times, and a water bath is used for cooling to keep the temperature at 25°C; the treated aqueous emulsion is filtered for impurities using a 0.40μm filter membrane to ensure that the aqueous phase of the emulsion has no particle precipitation and is uniform and stable; the aqueous phase of the Pickering emulsion is obtained; the aqueous phase and oil phase of the Pickering emulsion are added to the emulsification reactor, and emulsified for 300s at a temperature of 15°C and an emulsification speed of 15000rpm to obtain the Pickering emulsion.

[0044] Example 6

[0045] The nano-chitosan suspension obtained in Example 3 was dispersed in deionized water, acetic acid was added to adjust the pH value of the solution to 5, and the mixture was stirred at 400 rpm at 35°C for 60 minutes; the suspension was ultrasonically treated at a power of 200 W for 20 minutes to form a uniformly dispersed nano-chitosan solution; polyethylene glycol was dissolved in deionized water, and the temperature was maintained at 60°C using a constant temperature water bath method, while stirring at 600 rpm for 60 minutes to ensure complete dissolution and avoid polyethylene glycol crystallization; the treated nano-chitosan suspension was mixed with the polyethylene glycol solution, and 0.3 wt% of an antioxidant was added, and a magnetic stirrer was used to control the stirring speed to 600 rpm. pm, the temperature is maintained at 60°C and stirred for 80 minutes; the mixed solution is treated with ultrasound to promote molecular interface interaction, the processing power is 300w, and the processing time is 30 minutes; the mixed solution is placed in a high-pressure homogenizer, the pressure is controlled at 200MPa, and high-pressure homogenization treatment is carried out, and the treatment is circulated 30 times, and a water bath is used for cooling to keep the temperature at 30°C; the treated aqueous emulsion is filtered for impurities using a 0.45μm filter membrane to ensure that the aqueous phase of the emulsion has no particle precipitation and is uniform and stable; the aqueous phase of the Pickering emulsion is obtained; the aqueous phase and oil phase of the Pickering emulsion are added to the emulsification reactor, and emulsified for 600s at a temperature of 30°C and an emulsification speed of 30000rpm to obtain the Pickering emulsion.

[0046] Example 7

[0047] 50 parts by weight of the nano-chitosan suspension prepared in Example 1 were dissolved in deionized water to obtain a crude coating liquid; the crude coating liquid was defoamed by ultrasound, standing or centrifugation to obtain a barrier layer coating liquid; the barrier layer coating liquid was coated on the surface of the base paper by a coating machine, the thickness of the coating liquid was 0.1 mm, and then the base paper coated with the barrier layer coating liquid was dried at a drying temperature of 20°C; then the Pickering emulsion prepared in Example 4 was coated again, the thickness of the coating liquid was 0.1 mm, and then the base paper coated with the Pickering emulsion coating liquid was dried at a drying temperature of 20°C to obtain a responsive antibacterial / modified atmosphere dual preservation paper.

[0048] Example 8

[0049] 500 parts by weight of the nano-chitosan suspension prepared in Example 2 were dissolved in deionized water to obtain a crude coating liquid; the crude coating liquid was defoamed by ultrasound, standing or centrifugation to obtain a barrier layer coating liquid; the barrier layer coating liquid was coated on the surface of the base paper by a coating machine, the thickness of the coating liquid was 3 mm, and then the base paper coated with the barrier layer coating liquid was dried at a drying temperature of 40°C; then the Pickering emulsion prepared in Example 5 was coated again, the thickness of the coating liquid was 1.5 mm, and then the base paper coated with the Pickering emulsion coating liquid was dried at a drying temperature of 40°C to obtain a responsive antibacterial / modified atmosphere dual preservation paper.

[0050] Embodiment 9

[0051] 1000 parts by weight of the nano-chitosan suspension prepared in Example 3 were dissolved in deionized water to obtain a crude coating liquid; the crude coating liquid was defoamed by ultrasound, standing or centrifugation to obtain a barrier layer coating liquid; the barrier layer coating liquid was coated on the surface of the base paper by a coating machine, the thickness of the coating liquid was 5 mm, and then the base paper coated with the barrier layer coating liquid was dried at a drying temperature of 60°C; then the Pickering emulsion prepared in Example 6 was coated again, the thickness of the coating liquid was 3 mm, and then the base paper coated with the Pickering emulsion coating liquid was dried at a drying temperature of 60°C to obtain a responsive antibacterial / modified atmosphere dual preservation paper.

[0052] Example 10

[0053] In this example, the antibacterial test of the fresh-keeping paper prepared in Example 9 was conducted to evaluate the antibacterial effect of the fresh-keeping paper. The prepared fresh-keeping paper was placed on a potato dextrose agar plate inoculated with Penicillium and cultured at 25°C and 90% RH for 5 days. No mold grew, indicating that the fresh-keeping paper has excellent antifungal properties. Figure 1 shown.

[0054] Example 11

[0055] In this example, a systematic experimental test will be conducted on the preservation performance of the responsive antibacterial / modified atmosphere dual preservation paper to evaluate its ability to maintain the freshness and quality of food under different storage conditions.

[0056] Rinse the purchased fresh strawberries, cherry tomatoes and cucumbers thoroughly with running water to remove surface dust and impurities. Use food-grade disinfectant (such as 84 disinfectant) to disinfect cutting tools and containers to ensure hygiene. Divide the strawberries and cucumbers into two groups, 200 grams each. One group is packaged with responsive antibacterial / modified atmosphere double-wrapped paper, and the other group is packaged with ordinary packaging materials (such as polyethylene bags) as a control group.

[0057] The packaged samples were placed in three different storage environments: room temperature storage (25°C), refrigerated storage (4°C), and frozen storage (-18°C).

[0058] During storage, the food should be monitored regularly by observing and recording the following parameters: sensory evaluation (color, smell, texture, appearance); pH changes, measured using a pH meter; total microbial count, using standard culture media for bacterial detection.

[0059] Scores are given based on color, smell, texture and other criteria (1-5 points), with 1 being very poor and 5 being very good.

[0060] Samples were taken every 3 days, cultured for 24-48 hours, and the total bacterial count (expressed as CFU / g) was counted.

[0061]

[0062]

[0063]

[0064]

[0065] Under normal temperature storage conditions, fruit packaged in responsive antibacterial / modified atmosphere wrapping significantly outperformed fruit packaged in polyethylene bags in terms of freshness preservation, especially after 3 and 7 days. The score of the responsive wrapping group declined slowly, while the score of the polyethylene bag group deteriorated rapidly.

[0066] The responsive fresh-keeping paper maintained a relatively stable pH value under refrigeration and freezing conditions, demonstrating good fresh-keeping performance. In contrast, the pH value of the polyethylene bag group increased more significantly, indicating increased microbial activity.

[0067] Under both room temperature and refrigerated storage conditions, the responsive fresh-keeping paper significantly reduced the number of microorganisms, especially in the comparison between 3 days and 7 days, when the number of microorganisms was much lower. However, the number of microorganisms in the polyethylene bag continued to increase, indicating that its preservation effect was poor.

[0068] The above experimental results show that the responsive antibacterial / modified atmosphere dual-purpose fresh-keeping paper significantly outperforms traditional polyethylene bags in terms of freshness preservation performance. Especially under both room temperature and refrigerated conditions, it exhibits excellent antibacterial effects, effectively reducing the growth of food microorganisms and maintaining the sensory properties and freshness of food, providing a superior solution for long-term food storage.

[0069] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A responsive antibacterial / modified atmosphere dual fresh-keeping paper, characterized in that: The responsive antibacterial / modified atmosphere dual fresh-keeping paper comprises: paper, Pickering emulsion, nano-chitin, and polyethylene glycol; The preparation process of the nano-chitosan comprises the following steps: S1: Soak chitosan powder in a 20-50 wt% NaOH solution, stir mechanically at 600-800 rpm at 60-120°C, and allow to react for 2-8 hours to ensure partial deacetylation; separate the solid and liquid phases of the reaction mixture through a vacuum filter, retain the solid phase, and wash the solid phase with deionized water 5-10 times until the pH value of the washing solution reaches 7-7.5; S2 disperses solid chitosan in distilled water, adds acetic acid solution to the chitosan dispersion by titration at a controlled drop rate of 0.5-0.8 mL / s, and adjusts the pH value of the mixture to 2.5-4.0 to prevent chitosan from agglomerating. S3: placing the pH-adjusted chitosan suspension into a high-pressure homogenizer, setting the homogenization pressure to 200-400 MPa, and circulating the process 15-30 times. During the homogenization process, the temperature is maintained at 15-50°C to avoid damage to the chitosan structure. After the homogenization process, the chitosan suspension is assisted by an ultrasonic processor, with the power set to 100-200 W and the frequency set to 40-60 kHz. The ultrasonic process is performed for 10-20 minutes to further disperse the chitosan particles. S4 uses a rotary evaporator to concentrate the nano-chitosan suspension to a final solid content of 3-5 wt %, thereby obtaining nano-chitosan; The preparation process of the Pickering emulsion comprises the following steps: S5: dispersing the nano-chitosan suspension in deionized water, adding acetic acid to adjust the pH value of the solution to 3-5, stirring at 300-400 rpm for 30-60 minutes at 25-35° C.; ultrasonically treating the suspension at a power of 100-200 W for 10-20 minutes to form a uniformly dispersed nano-chitosan solution; S6: Dissolve polyethylene glycol in deionized water, maintain the temperature at 50-60°C in a constant temperature water bath, and stir at 500-600 rpm for 40-60 minutes to ensure complete dissolution and avoid polyethylene glycol crystallization. S7: mixing the treated nano-chitosan suspension with a polyethylene glycol solution, adding 0.1-0.3 wt% of an antioxidant, using a magnetic stirrer, controlling the stirring speed to 400-600 rpm, maintaining the temperature at 50-60° C. and stirring for 60-80 minutes; ultrasonically treating the mixed solution to promote molecular interface interaction, with a processing power of 100-300 W and a processing time of 15-30 minutes; S8: placing the mixed liquid into a high-pressure homogenizer, controlling the pressure at 100-200 MPa, performing high-pressure homogenization treatment, and circulating the treatment 15-30 times, while using a water bath for cooling to maintain the temperature at 20-30°C; using a 0.35-0.45 μm filter membrane to filter impurities from the treated aqueous phase emulsion to ensure that the emulsion aqueous phase has no particle precipitation and is uniform and stable; obtaining the aqueous phase of the Pickering emulsion; S9 adds the water phase and the oil phase of the Pickering emulsion into the emulsification reactor, and emulsifies for 30s to 600s at a temperature of 4 to 30°C and an emulsification speed of 3000 to 30000 rpm to obtain the Pickering emulsion.

2. The responsive antibacterial / modified atmosphere dual fresh-keeping paper as claimed in claim 1, characterized in that: The polyethylene glycol is a combination of one or more of polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 10000, and polyethylene glycol 20000.

3. The responsive antibacterial / modified atmosphere dual fresh-keeping paper as claimed in claim 1, characterized in that: The antioxidant described in S7 is a combination of one or more of vitamin C, 3,4,5-trihydroxybenzoic acid, tocopherol, and glutathione.

4. The responsive antibacterial / modified atmosphere dual fresh-keeping paper as claimed in claim 1, characterized in that: The oil phase described in S9 is one or more combinations of plant essential oils such as rose essential oil, cinnamon essential oil, lemon essential oil, tea tree essential oil, peppermint essential oil, oregano essential oil, etc.

5. The method for preparing the responsive antibacterial / modified atmosphere dual fresh-keeping paper according to claims 1 to 4, characterized in that: The preparation method comprises the following steps: S10: dissolving 50 to 1000 parts by weight of the nano-chitosan suspension in deionized water to obtain a crude coating solution; defoaming the crude coating solution by ultrasonication, standing, or centrifugation to obtain a barrier layer coating solution; S11 uses a coating machine to apply the barrier layer coating liquid on the surface of the base paper, the thickness of the coating liquid is 0.1~5 mm, and then the base paper coated with the barrier layer coating liquid is dried at a drying temperature of 20~60℃; then the Pickering emulsion is applied again, the thickness of the coating liquid is 0.1~3 mm, and then the base paper coated with the Pickering emulsion coating liquid is dried at a drying temperature of 20~60℃ to obtain a responsive antibacterial / modified atmosphere dual preservation paper.

Images