A method for surface antibacterial treatment of cardboard boxes for fruit preservation

Abstract

This invention relates to a surface antibacterial method for cardboard boxes used for fruit preservation, belonging to the field of cardboard coating technology. The method involves preparing a base solution, curing and modifying capsules, and treating with a treatment solution to obtain a coating liquid. This coating liquid is then applied to the surface of the cardboard box to obtain a cardboard box with surface antibacterial properties for fruit preservation. Through intermolecular interactions, the connection between the coating and the cardboard box surface is innovatively strengthened, as well as the connection between the antibacterial components and the porous capsules, achieving long-lasting antibacterial effects and resulting in excellent fruit preservation.

Description

Technical Field

[0001] This invention belongs to the field of cardboard coating technology and relates to a method for surface antibacterial treatment of cardboard boxes used for fruit preservation. Background Technology

[0002] In modern agricultural logistics systems, the transportation, storage, and sales of fruits place high demands on preservation technology and microbial control. Although existing fruit preservation packaging has improved in some aspects, it still has limitations in terms of antibacterial performance. First, traditional cardboard boxes are insufficiently moisture-proof; once damp, the physical structure of the box softens rapidly, losing its original protective function, making the fruit susceptible to mechanical damage and external contamination. Second, these cardboard boxes lack antibacterial properties and cannot effectively inhibit the growth of microorganisms, making the fruit prone to spoilage during storage and transportation. In addition, the ethylene gas naturally released by fruits during ripening accelerates the decay process, further exacerbating spoilage and thus accelerating bacterial growth.

[0003] Given that fruit is an important part of people's daily diet, its freshness and safety are crucial to consumers' health. However, the demand for fruit boxes is large, and directly improving the manufacturing process of these boxes is labor-intensive and costly. Therefore, improving the antibacterial properties of existing cardboard boxes through modification techniques to achieve better fruit preservation has become an important research direction. Summary of the Invention

[0004] The purpose of this invention is to provide a surface antibacterial method for fruit preservation cartons. By innovatively strengthening the connection between the coating and the carton surface, as well as the connection between the antibacterial components and the porous capsules through intermolecular interactions, a long-lasting antibacterial effect is achieved, resulting in a good fruit preservation effect.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for inhibiting bacterial growth on the surface of a cardboard box used for fruit preservation, the method comprising the following steps:

[0007] (1) Mix starch, sodium carboxymethyl cellulose and deionized water, add citric acid to adjust the pH, stir and heat to 50-70℃, keep the temperature constant and continue stirring for 10-20 minutes to obtain modified starch solution;

[0008] (2) Add PVP K30 to the modified starch solution and stir until homogeneous to obtain the base solution;

[0009] (3) Mix activated carbon, ethylenediaminetetraacetic acid and ethyl acetate, and stir for 20-30 min to obtain the oil phase;

[0010] (4) Pour the oil phase into the base solution and stir for 30-40 minutes to obtain an emulsion. Place the emulsion under UV light for 4-6 minutes to obtain the solidified capsule.

[0011] (5) Soak the cured capsules in an acrylic acid solution, irradiate them under UV light for 4-6 minutes, centrifuge, filter, wash with deionized water and air dry to obtain the modified capsules.

[0012] (6) Immerse the modified capsules in the treatment solution and sonicate for 15-35 minutes to obtain the coating solution;

[0013] (7) Apply the coating liquid evenly to the surface of the cardboard box, place it at room temperature for 20-40 minutes after coating, and then cure it in an oven at 60℃ for 20-40 minutes to obtain a cardboard box for surface antibacterial preservation of fruit.

[0014] Further, in step (1), the mass ratio of starch, sodium carboxymethyl cellulose and deionized water is 1.52-1.74:0.21-0.37:20-30; the concentration of citric acid in step (1) is 0.08-0.12 mol / L; the pH in step (1) is adjusted to 4.2-4.8; and the stirring speed in step (1) is 200-400 rpm.

[0015] Furthermore, in step (2), the mass of PVP K30 accounts for 1-3% of the modified starch solution; the stirring speed in step (2) is 480-520 rpm.

[0016] Further, in step (3), the mass ratio of activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate is 8.1-9.7:3.6-4.5:20-30; and the stirring speed in step (3) is 450-550 rpm.

[0017] Further, the concentration of the acrylic acid solution in step (5) is 0.14-0.2 mol / L; the parameters of the centrifugation step in step (5) are: at room temperature, the centrifugation speed is 800-1200 rpm, and the centrifugation time is 5-10 min; the pore size of the filter membrane used in the filtration step in step (5) is 0.45 μm.

[0018] Further, the treatment solution in step (6) is composed of 2-6 wt% nano-copper, 1-3 wt% polyvinyl alcohol, 0.5-1 wt% organosilane and the balance deionized water; the nano-copper has a particle size of 20-40 nm; the organosilane is composed of trimethoxysilane and vinyltriethoxysilane in a mass ratio of 4.43-4.79:3.68-4.02; the ultrasonic treatment parameters in step (6) are: ultrasonic temperature of 30-40℃ and ultrasonic frequency of 400-500W.

[0019] Furthermore, the coating parameters in step (7) are: two layers are coated, and the thickness of each layer is controlled at 40-60 μm.

[0020] Furthermore, the parameters for the UV light treatment are as follows: UV light wavelength is 365nm, and UV light intensity is 40-60mW / cm². 2 .

[0021] The beneficial effects of this invention are:

[0022] This invention, by combining sodium carboxymethyl cellulose and starch, significantly enhances the intermolecular forces of the coating, forming a reinforced moisture barrier that effectively resists the penetration of external humidity, thereby reducing the possibility of microbial proliferation in humid environments. PVP K30, as the main material of the capsule wall, can cross-link under UV light to form a porous yet stable capsule wall structure, improving the flexibility and elasticity of the coating, making the coating more uniform on the cardboard surface, reducing the possibility of cracks and peeling. Its porous nature restricts the passage of macromolecules such as microorganisms and ethylene, exerting an antibacterial effect externally and slowing down bacterial growth caused by fruit spoilage internally. During the ripening and storage process, fruits produce reactive oxygen species and release ethylene gas. Activated carbon, encapsulated inside the capsule, has an adsorption function, adsorbing the ethylene gas released by the fruit and slowing down the ripening process. Meanwhile, ethylenediaminetetraacetic acid, as an antioxidant, can slow down the oxidation reaction during fruit ripening, synergistically and indirectly inhibiting microbial growth and reducing spoilage, resulting in a better antibacterial and preservation effect.

[0023] This invention utilizes acrylic acid grafting modification to introduce carboxyl groups on the capsule surface, which interact with the active sites on the surface of nano-copper, enhancing the fixation of nano-copper in the capsule wall and improving the dispersibility and stability of antibacterial components. The organosilanes in the treatment solution, namely a mixture of trimethoxysilane and vinyltriethoxysilane, interact with the hydroxyl groups in the cellulose molecules on the cardboard surface through silanol groups, forming stable silicon-oxygen bonds, which improves the adhesion and water resistance of the coating, enhances the mechanical strength and resistance to chemical media erosion of the coating, and ensures the durability of the coating during transportation and handling. In conjunction with the broad-spectrum antibacterial effect of nano-copper, it combines with polyvinyl alcohol to form a uniform, stable surface coating with antibacterial function, effectively inhibiting the growth of bacteria and fungi on the cardboard surface.

[0024] This invention innovatively strengthens the connection between the coating and the cardboard surface, as well as the connection between the antibacterial components and the porous capsules, through intermolecular interactions, thereby achieving long-lasting antibacterial effects and good fruit preservation. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] Example 1

[0027] A method for surface antibacterial treatment of cardboard boxes for fruit preservation, the method of this embodiment includes the following steps:

[0028] (1) Mix starch, sodium carboxymethyl cellulose and deionized water, add citric acid to adjust the pH, stir and heat to 50°C, keep the temperature constant and continue stirring for 10 min to obtain modified starch solution;

[0029] (2) Add PVP K30 to the modified starch solution and stir until homogeneous to obtain the base solution;

[0030] (3) Mix activated carbon, ethylenediaminetetraacetic acid and ethyl acetate, and stir for 20 min to obtain the oil phase;

[0031] (4) Pour the oil phase into the base solution. The mass ratio of the oil phase to the base solution is 2.9:8.3. Stir for 30 min to obtain an emulsion. Place the emulsion under UV light for 4 min to obtain the solidified capsule.

[0032] (5) The cured capsules were immersed in an acrylic acid solution with a mass ratio of 1.25:7.4. They were then irradiated under UV light for 4 minutes, centrifuged, filtered, washed with deionized water, and air-dried to obtain the modified capsules.

[0033] (6) Immerse the modified capsules in the treatment solution and sonicate for 15 minutes to obtain the coating solution;

[0034] (7) Apply the coating liquid evenly to the surface of the cardboard box, place it at room temperature for 20 minutes after coating, and then cure it in an oven at 60℃ for 20 minutes to obtain a cardboard box for surface antibacterial preservation of fruit.

[0035] In step (1) of this embodiment, the mass ratio of starch, sodium carboxymethyl cellulose and deionized water is 1.52:0.21:20; the concentration of citric acid in step (1) of this embodiment is 0.08 mol / L; the pH in step (1) of this embodiment is adjusted to 4.2; and the stirring speed in step (1) of this embodiment is 200 rpm.

[0036] In step (2) of this embodiment, the mass of PVP K30 accounts for 1% of the modified starch solution; the stirring speed in step (2) of this embodiment is 480 rpm.

[0037] In step (3) of this embodiment, the mass ratio of activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate is 8.1:3.6:20; the stirring speed in step (3) of this embodiment is 450 rpm.

[0038] The concentration of the acrylic acid solution in step (5) of this embodiment is 0.14 mol / L; the parameters of the centrifugation step in step (5) of this embodiment are: at room temperature, the centrifugation speed is 800 rpm and the centrifugation time is 5 min; the pore size of the filter membrane used in the filtration step in step (5) of this embodiment is 0.45 μm.

[0039] The treatment solution in step (6) of this embodiment consists of 2 wt% nano copper, 1 wt% polyvinyl alcohol, 0.5 wt% organosilane and the balance deionized water; the nano copper in this embodiment has a particle size of 20 nm; the organosilane in this embodiment consists of trimethoxysilane and vinyltriethoxysilane in a mass ratio of 4.43:3.68; the ultrasonic treatment parameters in step (6) of this embodiment are: ultrasonic temperature of 30°C and ultrasonic frequency of 400 W.

[0040] The coating parameters in step (7) of this embodiment are: two layers are coated, and the thickness of each layer is controlled at 40 μm.

[0041] The parameters for UV light processing in this embodiment are as follows: UV light wavelength is 365nm, UV light intensity is 40mW / cm². 2 .

[0042] Example 2

[0043] A method for surface antibacterial treatment of cardboard boxes for fruit preservation, the method of this embodiment includes the following steps:

[0044] (1) Mix starch, sodium carboxymethyl cellulose and deionized water, add citric acid to adjust the pH, stir and heat to 70°C, keep the temperature constant and continue stirring for 20 min to obtain modified starch solution;

[0045] (2) Add PVP K30 to the modified starch solution and stir until homogeneous to obtain the base solution;

[0046] (3) Mix activated carbon, ethylenediaminetetraacetic acid and ethyl acetate, and stir for 30 min to obtain the oil phase;

[0047] (4) Pour the oil phase into the base solution. The mass ratio of the oil phase to the base solution is 2.9:8.3. Stir for 40 min to obtain an emulsion. Place the emulsion under UV light for 6 min to obtain the solidified capsule.

[0048] (5) The cured capsules were immersed in an acrylic acid solution with a mass ratio of 1.25:7.4. They were then irradiated under UV light for 6 minutes, centrifuged, filtered, washed with deionized water, and air-dried to obtain the modified capsules.

[0049] (6) Immerse the modified capsules in the treatment solution and sonicate for 35 minutes to obtain the coating solution;

[0050] (7) Apply the coating liquid evenly to the surface of the cardboard box, place it at room temperature for 40 minutes after coating, and then cure it in an oven at 60℃ for 40 minutes to obtain a cardboard box for surface antibacterial preservation of fruit.

[0051] In step (1) of this embodiment, the mass ratio of starch, sodium carboxymethyl cellulose and deionized water is 1.74:0.37:30; the concentration of citric acid in step (1) of this embodiment is 0.12 mol / L; the pH in step (1) of this embodiment is adjusted to 4.8; and the stirring speed in step (1) of this embodiment is 400 rpm.

[0052] In step (2) of this embodiment, the mass of PVP K30 accounts for 3% of the modified starch solution; the stirring speed in step (2) of this embodiment is 520 rpm.

[0053] In step (3) of this embodiment, the mass ratio of activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate is 9.7:4.5:30; and the stirring speed in step (3) of this embodiment is 550 rpm.

[0054] The concentration of the acrylic acid solution in step (5) of this embodiment is 0.2 mol / L; the parameters of the centrifugation step in step (5) of this embodiment are: at room temperature, the centrifugation speed is 1200 rpm and the centrifugation time is 10 min; the pore size of the filter membrane used in the filtration step in step (5) of this embodiment is 0.45 μm.

[0055] The treatment solution in step (6) of this embodiment consists of 6 wt% nano copper, 3 wt% polyvinyl alcohol, 1 wt% organosilane and the balance deionized water; the nano copper in this embodiment has a particle size of 40 nm; the organosilane in this embodiment consists of trimethoxysilane and vinyltriethoxysilane in a mass ratio of 4.79:4.02; the ultrasonic treatment parameters in step (6) of this embodiment are: ultrasonic temperature of 40°C and ultrasonic frequency of 500 W.

[0056] The coating parameters in step (7) of this embodiment are: two layers are coated, and the thickness of each layer is controlled at 60μm.

[0057] The parameters for UV light processing in this embodiment are as follows: UV light wavelength is 365nm, UV light intensity is 60mW / cm². 2 .

[0058] Example 3

[0059] A method for surface antibacterial treatment of cardboard boxes for fruit preservation, the method of this embodiment includes the following steps:

[0060] (1) Mix starch, sodium carboxymethyl cellulose and deionized water, add citric acid to adjust the pH, stir and heat to 60°C, keep the temperature constant and continue stirring for 15 min to obtain modified starch solution;

[0061] (2) Add PVP K30 to the modified starch solution and stir until homogeneous to obtain the base solution;

[0062] (3) Mix activated carbon, ethylenediaminetetraacetic acid and ethyl acetate, and stir for 25 min to obtain the oil phase;

[0063] (4) Pour the oil phase into the base solution. The mass ratio of the oil phase to the base solution is 2.9:8.3. Stir for 35 minutes to obtain an emulsion. Place the emulsion under UV light for 5 minutes to obtain the solidified capsule.

[0064] (5) The cured capsules were immersed in an acrylic acid solution with a mass ratio of 1.25:7.4. They were then irradiated under UV light for 5 minutes, centrifuged, filtered, washed with deionized water, and air-dried to obtain the modified capsules.

[0065] (6) Immerse the modified capsules in the treatment solution and sonicate for 25 minutes to obtain the coating solution;

[0066] (7) Apply the coating liquid evenly to the surface of the cardboard box, place it at room temperature for 30 minutes after coating, and then cure it in an oven at 60℃ for 30 minutes to obtain a cardboard box for surface antibacterial preservation of fruit.

[0067] In step (1) of this embodiment, the mass ratio of starch, sodium carboxymethyl cellulose and deionized water is 1.63:0.29:25; the concentration of citric acid in step (1) of this embodiment is 0.1 mol / L; the pH in step (1) of this embodiment is adjusted to 4.5; and the stirring speed in step (1) of this embodiment is 300 rpm.

[0068] In step (2) of this embodiment, the mass of PVP K30 accounts for 2% of the modified starch solution; the stirring speed in step (2) of this embodiment is 500 rpm.

[0069] In step (3) of this embodiment, the mass ratio of activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate is 8.9:4.05:25; the stirring speed in step (3) of this embodiment is 500 rpm.

[0070] The concentration of the acrylic acid solution in step (5) of this embodiment is 0.17 mol / L; the parameters of the centrifugation step in step (5) of this embodiment are: at room temperature, the centrifugation speed is 1000 rpm and the centrifugation time is 7.5 min; the filter membrane used in the filtration step in step (5) of this embodiment has a pore size of 0.45 μm.

[0071] The treatment solution in step (6) of this embodiment consists of 4 wt% nano copper, 2 wt% polyvinyl alcohol, 0.75 wt% organosilane and the balance deionized water; the nano copper in this embodiment has a particle size of 30 nm; the organosilane in this embodiment consists of trimethoxysilane and vinyltriethoxysilane in a mass ratio of 4.61:3.85; the ultrasonic treatment parameters in step (6) of this embodiment are: ultrasonic temperature of 35°C and ultrasonic frequency of 450 W.

[0072] The coating parameters in step (7) of this embodiment are: two layers are coated, and the thickness of each layer is controlled at 50 μm.

[0073] The parameters for UV light processing in this embodiment are as follows: UV light wavelength is 365nm, UV light intensity is 50mW / cm². 2 .

[0074] Comparative Example 1

[0075] Based on Example 3, PVP K30 was removed and replaced with an equal weight of gelatin, while other conditions remained the same as in Example 3.

[0076] Comparative Example 2

[0077] Based on Example 3, ethylenediaminetetraacetic acid was removed and replaced with an equal weight of activated carbon, while other conditions remained the same as in Example 3.

[0078] Comparative Example 3

[0079] Based on Example 3, the preparation methods of (1)-(6) were modified as follows: after mixing the modified starch, sodium carboxymethyl cellulose, PVP K30, activated carbon, ethylenediaminetetraacetic acid, deionized water and treatment solution evenly, the mixture was ultrasonically treated for 25 minutes to obtain the coating. Other conditions were the same as in Example 3.

[0080] Comparative Example 4

[0081] Based on Example 3, step (5) is removed, while other conditions remain the same as in Example 3.

[0082] Comparative Example 5

[0083] Based on Example 3, vinyltriethoxysilane was removed from the organosilane and replaced with an equal weight of trimethoxysilane, while other conditions remained the same as in Example 3.

[0084] Comparative Example 6

[0085] Based on Example 3, the polyvinyl alcohol in the treatment solution was removed and replaced with an equal weight of deionized water, while other conditions remained the same as in Example 3.

[0086] The cardboard boxes treated according to the methods of Examples 1-3 and Comparative Examples 1-6 were punched with a hole punch to obtain circular pieces with a diameter of 6 mm, and then subjected to ultraviolet sterilization for 2 hours. Then, 1 mL of a 10% concentration was taken from each piece. 5 CFU / mL of Escherichia coli and Staphylococcus aureus were dropped onto their respective culture media, spread evenly, and allowed to stand for 10 minutes to allow complete bacterial diffusion. Disc samples were then placed in the center of petri dishes and incubated at 37°C and 60% RH. A ripe apple was also placed in the incubator. Ethylene concentrations were measured using an ethylene gas detector at 24h and 48h. The specific growth was observed, and the diameter of the inhibition zone was measured. The initial ethylene concentration was 0 ppm. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As shown in Table 1, when the ambient humidity is 60%, the cardboard boxes treated by the method of the present invention have a better antibacterial effect. Moreover, the antibacterial effect of the cardboard boxes treated by the method used in Examples 1-3 is significantly better than that of the method used in Comparative Examples 1-6. In addition, this method can adsorb ethylene gas released by fruits, synergistically inhibit the growth of microorganisms, reduce spoilage, and achieve a better antibacterial and preservation effect.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for surface antibacterial treatment of cardboard boxes for fruit preservation, characterized in that, The method includes the following steps: (1) Mix starch, sodium carboxymethyl cellulose and deionized water, add citric acid to adjust the pH, stir and heat to 50-70℃, keep the temperature constant and continue stirring for 10-20 minutes to obtain modified starch solution; (2) Add PVP K30 to the modified starch solution and stir until homogeneous to obtain the base solution; (3) Mix activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate, and stir for 20-30 min to obtain the oil phase; (4) Pour the oil phase into the base solution and stir for 30-40 min to obtain an emulsion. Place the emulsion under UV light for 4-6 min to obtain the solidified capsule. (5) Soak the cured capsules in an acrylic acid solution, irradiate them under UV light for 4-6 minutes, centrifuge, filter, wash with deionized water and air dry to obtain the modified capsules; (6) Immerse the modified capsules in the treatment solution and sonicate for 15-35 min to obtain the coating solution; (7) Apply the coating liquid evenly to the surface of the cardboard box, place it at room temperature for 20-40 minutes after coating, and then cure it in an oven at 60℃ for 20-40 minutes to obtain a cardboard box for surface antibacterial preservation of fruit. The mass ratio of starch, sodium carboxymethyl cellulose, and deionized water in step (1) is 1.52-1.74:0.21-0.37:20-30; In step (2), the mass of PVP K30 accounts for 1-3% of the modified starch solution; The mass ratio of activated carbon, ethylenediaminetetraacetic acid, and ethyl acetate in step (3) is 8.1-9.7:3.6-4.5:20-30; The concentration of the acrylic acid solution in step (5) is 0.14-0.2 mol / L; The treatment solution in step (6) consists of 2-6 wt% nano-copper, 1-3 wt% polyvinyl alcohol, 0.5-1 wt% organosilane and the balance deionized water; the nano-copper has a particle size of 20-40 nm; the organosilane is composed of trimethoxysilane and vinyltriethoxysilane in a mass ratio of 4.43-4.79:3.68-4.

02.

2. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The concentration of citric acid in step (1) is 0.08-0.12 mol / L; the pH in step (1) is adjusted to 4.2-4.8; and the stirring speed in step (1) is 200-400 rpm.

3. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The stirring speed in step (2) is 480-520 rpm.

4. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The stirring speed in step (3) is 450-550 rpm.

5. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The parameters for the centrifugation step in step (5) are: at room temperature, the centrifugation speed is 800-1200 rpm and the centrifugation time is 5-10 min; the filter membrane used in the filtration step in step (5) has a pore size of 0.45 μm.

6. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The parameters for ultrasonic treatment in step (6) are: ultrasonic temperature of 30-40℃ and ultrasonic frequency of 400-500W.

7. The method for surface antibacterial treatment of a cardboard box for fruit preservation according to claim 1, characterized in that, The coating parameters in step (7) are: two layers are coated, and the thickness of each layer is controlled at 40-60μm.

8. A method for surface antibacterial treatment of cardboard boxes for fruit preservation according to claim 1, characterized in that, The parameters for the UV light processing are as follows: UV light wavelength is 365nm, and UV light intensity is 40-60mW / cm2.

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