Lignin supported cinnamaldehyde nanoparticles, antibacterial wrapping paper and preparation method and application thereof

Abstract

This invention discloses lignin-loaded cinnamaldehyde nanoparticles, antibacterial packaging paper, and their preparation methods and applications, belonging to the field of functional packaging materials technology. Using alkali lignin as raw material, this invention prepares lignin-loaded cinnamaldehyde nanoparticles (Lig-CIN NPs) via an antisolvent precipitation method, achieving a cinnamaldehyde encapsulation rate of over 96%. These nanoparticles achieve stable bonding through hydrogen bonding and hydrophobic interactions between lignin and cinnamaldehyde, significantly improving the thermal stability of cinnamaldehyde. The antibacterial packaging paper prepared by combining Lig-CIN NPs with a film-forming agent and then applying the coating process exhibits excellent barrier properties, mechanical properties, dual temperature and pH response release characteristics, and gas-phase antibacterial properties. It shows gas-phase inhibition rates of 96% and 92% against *Escherichia coli* and *Staphylococcus aureus*, respectively, and demonstrates significant preservation effects in strawberry preservation experiments. This invention realizes the high-value utilization of industrial lignin and the long-term controllable release of cinnamaldehyde, showing broad application prospects in the field of fruit and vegetable preservation packaging.

Description

Technical Field

[0001] This invention belongs to the field of functional packaging materials technology, specifically relating to lignin-loaded cinnamaldehyde nanoparticles, antibacterial packaging paper, and their preparation methods and applications. Background Technology

[0002] Postharvest spoilage of fruits and vegetables is a serious challenge facing the global food supply chain. Microbial contamination is a key factor inducing spoilage, while mechanical damage during postharvest transportation and handling further exacerbates the problem. Globally, direct economic losses due to fruit and vegetable spoilage approach hundreds of billions of US dollars annually, with approximately 30% of food being lost or wasted in the supply chain, of which fruits and vegetables account for over 40%.

[0003] Cinnamaldehyde is a naturally occurring aldehyde compound, primarily derived from extracts of the bark, leaves, and roots of the cinnamon tree. It possesses broad-spectrum and highly effective antibacterial activity. Its antibacterial mechanism mainly involves disrupting the cell membrane structure of microorganisms, leading to the outflow of cell contents and ultimately bacterial death. However, cinnamaldehyde's inherent volatility, poor water solubility, and poor chemical stability severely limit its long-term application in food packaging.

[0004] In existing technologies, researchers have attempted to encapsulate cinnamaldehyde using carrier systems such as liposomes, nanoemulsions, and Pickering emulsions to improve its stability. However, these systems still face inherent limitations: liposomes suffer from phospholipid oxidation and reduced encapsulation efficiency, nanoemulsions typically require the synthesis of large amounts of surfactants, and the large-scale preparation of Pickering emulsions still presents technical challenges.

[0005] Some studies have attempted to add cinnamaldehyde directly to paper to prepare antibacterial packaging paper, but there are the following shortcomings: (1) When cinnamaldehyde is directly loaded onto paper, it is easy to volatilize and be lost due to lack of effective protection, resulting in poor antibacterial durability; (2) Cinnamaldehyde has weak binding force with fiber and is easy to be released quickly in humid environments, making it difficult to achieve long-term sustained release; (3) There is a lack of precise control over the release behavior, making it impossible to adjust the release rate according to actual preservation needs.

[0006] Lignin is the second most abundant biomass resource in the plant kingdom after cellulose. Its three-dimensional aromatic network structure and abundant functional groups such as phenolic hydroxyl and methoxy groups can stably bind with hydrophobic molecules through non-covalent interactions such as hydrophobic interactions, π-π stacking, and hydrogen bonding. However, currently, about 95% of industrial lignin is disposed of through direct incineration, resulting in resource waste and environmental pollution. Therefore, developing high-value utilization pathways for lignin has significant economic and environmental implications.

[0007] Existing patents, such as CN115926206A, disclose a method for preparing single-component lignin nanoparticles and demonstrate their antibacterial properties. However, this method only addresses the antibacterial properties of lignin itself, and does not address issues such as how to load and control the release of unstable plant essential oils, or how to prepare paper-based packaging materials based on gas-phase antibacterial properties. Current lignin antibacterial materials mostly employ composite materials, which involve complex and costly preparation processes, and do not provide reasonable guidance on how to improve the antibacterial properties of lignin itself. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide lignin-loaded cinnamaldehyde nanoparticles to address the shortcomings of the prior art.

[0009] Another technical problem to be solved by the present invention is to provide a method for preparing lignin-loaded cinnamaldehyde nanoparticles.

[0010] Another technical problem to be solved by the present invention is to provide an application of lignin-loaded cinnamaldehyde nanoparticles in the preparation of antibacterial packaging paper.

[0011] Another technical problem that this invention aims to solve is to provide an antibacterial packaging paper.

[0012] Another technical problem that this invention aims to solve is to provide a method for preparing antibacterial packaging paper.

[0013] The final technical problem to be solved by this invention is to provide an application of antibacterial packaging paper in the preservation of fruits and vegetables.

[0014] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0015] The first aspect of the present invention provides lignin-loaded cinnamaldehyde nanoparticles, wherein the lignin-loaded cinnamaldehyde nanoparticles are self-assembled by a nano-framework formed by lignin self-assembly and cinnamaldehyde through a synergistic effect of hydrogen bonding and hydrophobic interaction; the cinnamaldehyde is encapsulated by the nano-framework formed by the lignin self-assembly.

[0016] The mass ratio of cinnamaldehyde to lignin is 1:(0.25~4).

[0017] The lignin-loaded cinnamaldehyde nanoparticles have a particle size of 20 to 400 nm.

[0018] In some embodiments, the mass ratio of cinnamaldehyde to lignin is 1:(1~4).

[0019] In some embodiments, the mass ratio of cinnamaldehyde to lignin is 1:(1~2).

[0020] A second aspect of this invention provides a method for preparing the lignin-loaded cinnamaldehyde nanoparticles, comprising the following steps:

[0021] Step 1: Add alkali lignin to acetone, mix well, separate solid and liquid, collect the liquid, remove acetone, and obtain graded lignin.

[0022] Step 2: Cinnamaldehyde and the graded lignin obtained in Step 1 are dissolved in acetone to obtain a second mixture. The second mixture is added dropwise to water to obtain a third mixture. The acetone is removed to obtain a lignin-loaded cinnamaldehyde nanoparticle suspension.

[0023] In step 1, the solid-liquid ratio of the alkali lignin to the acetone is (40 ~ 60) mg : 1 mL; the mixing method is to stir for 6 ~ 12 h at 20 ~ 30℃ and 300 ~ 500 r / min; the removal of acetone is to remove it by rotary evaporation at 50 ~ 70℃.

[0024] In some embodiments, in step 1, the solid-liquid separation is performed by vacuum filtration using a Buchner funnel.

[0025] In step 2, the mass ratio of cinnamaldehyde to graded lignin is 1:(0.25~4); the concentration of graded lignin in the second mixture is 5~40 mg / mL; the dropwise addition is performed at a flow rate of 1~8 mL / min; the second mixture is added dropwise to water at a temperature of 20~30℃ and a stirring speed of 200~600 r / min; the volume ratio of the second mixture to water is 1:(1~3); and the removal of acetone is performed by rotary evaporation at 50~70℃.

[0026] In some embodiments, in step 2, the mass ratio of cinnamaldehyde to graded lignin is 1:(1~4).

[0027] In some embodiments, in step 2, the mass ratio of cinnamaldehyde to graded lignin is 1:(1~2).

[0028] In some embodiments, in step 2, the concentration of graded lignin in the second mixture is 20 mg / mL; the dripping is performed at a flow rate of 2 mL / min; the second mixture is added to water at a temperature of 20-30°C and a stirring speed of 400 r / min; the volume ratio of the second mixture to the water is 1:1.

[0029] In some embodiments, in step 2, after the droplet addition is completed, stirring continues for 30 minutes at a temperature of 20-30°C and a stirring speed of 200-600 r / min.

[0030] A third aspect of the present invention provides the application of the lignin-loaded cinnamaldehyde nanoparticles in the preparation of antibacterial packaging paper.

[0031] A fourth aspect of the present invention provides an antibacterial packaging paper, comprising a paper matrix and an antibacterial coating loaded on at least one surface of the paper matrix; the antibacterial coating comprises lignin-loaded cinnamaldehyde nanoparticles; the paper matrix is ​​made from bleached softwood pulp; and the mass of the paper matrix per square meter is 50-70 g.

[0032] The antibacterial packaging paper has a water vapor permeability coefficient of 1.10 × 10⁻⁶. -10 ~ 1.88×10 -10 g / m·s·Pa, oxygen permeability coefficient is 9.3×10 -13 ~ 9.95×10 -13 cm 3 ·cm / cm 2 Tear strength (·s·Pa), tear index is 16.7 ~ 19.5 mN·m 2 The tensile index is 33.8 ~ 59.3 N·m / g, and the bursting index is 3.48 ~ 5.23 kPa·m. 2 / g, with a gas phase inhibition rate of not less than 90% against Escherichia coli and not less than 85% against Staphylococcus aureus.

[0033] In some embodiments, the antibacterial packaging paper exhibits vapor-phase inhibition rates of 96% and 92% against Escherichia coli and Staphylococcus aureus, respectively.

[0034] The fifth aspect of this invention provides a method for preparing the aforementioned antibacterial packaging paper, comprising the following steps:

[0035] The lignin-loaded cinnamaldehyde nanoparticles are added to a mixture of film-forming agent and water, mixed well to obtain a coating solution, and the coating solution is uniformly coated on at least one surface of the paper substrate and dried to obtain the final product.

[0036] The film-forming agent is any one or a combination of starch, carboxymethyl cellulose, and polyvinyl alcohol; the content of the film-forming agent in the mixture of the film-forming agent and water is 5-15 wt%; the amount of lignin-loaded cinnamaldehyde nanoparticles added is 0.5-5% of the mass of the film-forming agent; and the coating amount of the coating solution is 2-8 g / m³. 2 Paper substrate.

[0037] In some embodiments, when the film-forming agent is starch, the mixture of starch and water needs to be gelatinized at 95°C for 30 min and cooled to room temperature before adding the lignin-loaded cinnamaldehyde nanoparticles to the mixture of starch and water.

[0038] In some embodiments, the drying is performed under the following conditions: equilibration for 24 hours under constant temperature and humidity conditions of 23°C and 50% relative humidity.

[0039] In some embodiments, the film-forming agent is tapioca starch.

[0040] In some embodiments, the amount of lignin-loaded cinnamaldehyde nanoparticles added is 2 to 4% of the mass of the film-forming agent.

[0041] In some embodiments, the amount of lignin-loaded cinnamaldehyde nanoparticles added is 4% of the mass of the film-forming agent.

[0042] In some embodiments, the coating amount of the coating liquid is 4~8 g / m². 2 Paper substrate.

[0043] In some embodiments, the coating amount of the coating liquid is 6~8 g / m². 2 Paper substrate.

[0044] In some embodiments, the coating amount of the coating liquid is 8 g / m². 2 Paper substrate.

[0045] The preparation method of the paper matrix includes the following steps: bleached softwood pulp is loosened and beaten to 30-40°SR; the pulp concentration is adjusted to 0.2-0.5 wt%; sizing agent, wet strength agent, and retention aid are added and stirred evenly to obtain paper stock. The paper stock is formed using conventional papermaking methods, and after pressing and drying, the paper matrix is ​​obtained. It should be noted that the specific operations of papermaking, pressing, and drying are all common knowledge in the art. For example, laboratory-scale papermaking can be carried out according to the conventional steps disclosed in national standard GB / T 24326-2009 "Preparation of Laboratory Paper for Physical Testing of Pulp - Rapid Kaiser Method" or TAPPI T-205 standard; industrial-scale continuous production can also use papermaking equipment and processes well known in the art.

[0046] In some embodiments, the bleached softwood pulp is decomposed and then beaten to 35°SR, and the concentration of the pulp obtained after beating is adjusted to 0.3 wt%.

[0047] In some embodiments, the sizing agent is an alkyl ketene dimer emulsion, the wet strength agent is a polyamide epichlorohydrin resin, and the retention aid is cationic polyacrylamide.

[0048] In some embodiments, the amounts of the sizing agent, wet strength agent, and retention aid added are 0.3 wt%, 0.5 wt%, and 0.03 wt% of the mass of the pulp obtained after beating, respectively.

[0049] In some embodiments, water is used to adjust the concentration of the pulp obtained after beating.

[0050] The preparation process of the antibacterial packaging paper described in this invention is as follows: Figure 1 As shown.

[0051] The sixth aspect of this invention provides the application of the aforementioned antibacterial packaging paper in the preservation of fruits and vegetables.

[0052] The fruits and vegetables mentioned are any one or a combination of common fruits and vegetables such as strawberries, blueberries, cherries, or tomatoes.

[0053] Beneficial effects:

[0054] Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

[0055] (1) Significantly improved thermal stability and long-lasting effect of cinnamaldehyde: This invention utilizes the three-dimensional aromatic network structure of lignin to achieve efficient encapsulation of cinnamaldehyde through hydrogen bonding and hydrophobic interactions. Thermogravimetric analysis shows that the maximum degradation temperature of cinnamaldehyde in lignin-loaded cinnamaldehyde nanoparticles is increased from 190℃ in the free state to 364℃, significantly overcoming the technical bottleneck of cinnamaldehyde's volatility. Storage stability experiments demonstrate that the nanoparticles maintain good dispersibility and morphological stability within 15 days at 25℃.

[0056] (2) Controllable sustained release in response to both temperature and pH: This invention systematically reveals the release mechanism of cinnamaldehyde from lignin nanoparticles, and the release behavior conforms to a first-order kinetic model. Studies have shown that the sustained release behavior of cinnamaldehyde is mainly regulated by hydrophobic interactions and hydrogen bonds between the hydrophobic cavities of lignin and cinnamaldehyde molecules. At 37℃, the cumulative release rate of cinnamaldehyde reaches 98% after 8 days; while at a low temperature of 4℃, the release rate significantly decreases to 67%, showing obvious temperature responsiveness. An acidic environment can induce lignin network contraction and enhance hydrophobic interactions, thereby delaying the release of cinnamaldehyde and forming a novel deceleration response mechanism different from conventional stimulation-accelerated release. This characteristic enables the packaging paper to automatically adjust the antibacterial agent release rate according to the physiological state of the food, achieving precise release on demand.

[0057] (3) Fully leveraging the synergistic antibacterial effect of lignin and cinnamaldehyde: In vitro antibacterial experiments showed that lignin-loaded cinnamaldehyde nanoparticles achieved inhibition rates of 98% and 100% against Escherichia coli and Staphylococcus aureus, respectively, significantly superior to single lignin nanoparticles or free cinnamaldehyde. Antibacterial mechanism studies revealed that lignin-loaded cinnamaldehyde nanoparticles exert their antibacterial effect by disrupting the bacterial cell membrane structure, leading to leakage of contents. The synergistic antibacterial effect of lignin and cinnamaldehyde makes the antibacterial effect of the composite system far exceed that of a single component.

[0058] (4) Imparting excellent gas-phase antibacterial properties to paper: This invention uses a surface coating process to load lignin-loaded cinnamaldehyde nanoparticles onto paper. The resulting antibacterial packaging paper exhibits gas-phase inhibition rates of up to 96% and 92% against Escherichia coli and Staphylococcus aureus, respectively. The gas-phase antibacterial method does not rely on direct contact between the material and microorganisms, but rather constructs a dynamic gas-phase antibacterial environment within the packaging system through the autonomous volatilization of cinnamaldehyde. This method is particularly suitable for the preservation of fruits and vegetables with irregular surfaces that are prone to contact cross-contamination.

[0059] (5) Maintaining and enhancing the physical properties of paper: By controlling the coating amount and the amount of lignin-loaded cinnamaldehyde nanoparticles added, this invention significantly improves the mechanical and barrier properties of paper while imparting antibacterial function. Studies have shown that the composite of lignin nanoparticles and starch matrix can effectively improve the barrier properties and mechanical strength of the film. Compared with the paper matrix, the coating treatment reduces the water vapor transmission coefficient and oxygen transmission coefficient of antibacterial packaging paper by 81.66% and 47.13%, respectively, and increases the tear index, tensile index, and bursting index to 19.5 mN·m. 2 / g, 58.3 N·m / g and 5.23 kPa·m 2 / g provides sufficient physical strength assurance for the basic application of packaging materials.

[0060] (6) Achieving high-value utilization of industrial lignin: This invention uses alkali lignin, an industrial by-product, as raw material. It achieves high-value utilization of lignin through graded processing and nanotechnology, solving the problems of resource waste and low-value utilization caused by the dispersion and structural heterogeneity of lignin, which is in line with the concept of green chemistry and sustainable development.

[0061] (7) Significant preservation effect: Strawberry preservation experiments show that the antibacterial packaging paper of the present invention can effectively inhibit the growth of microorganisms, delay fruit rot, softening and nutrient loss, and significantly extend shelf life. Attached Figure Description

[0062] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0063] Figure 1 This is a schematic diagram of the preparation process of the antibacterial packaging paper of the present invention.

[0064] Figure 2 This is a comparison chart of the antibacterial activity and inhibition rate of lignin nanoparticles, cinnamaldehyde, and Lig-CIN NPs prepared under different cinnamaldehyde-lignin ratios in Example 5 against Staphylococcus aureus and Escherichia coli.

[0065] Figure 3 Scanning electron microscope (SEM) images of the surface morphology of antibacterial packaging papers with different coating amounts prepared in Example 9; wherein, image a is the base paper; image b is the paper with a coating amount of 2 g / m 2 Antibacterial packaging paper prepared under the specified conditions; Figure c shows the coating liquid with a coating amount of 4 g / m². 2 Antibacterial packaging paper prepared under the specified conditions; Figure d shows the coating amount of the coating solution at 6 g / m². 2 Antibacterial packaging paper prepared under the specified conditions; Figure e shows the coating amount of the coating solution at 8 g / m². 2 Antibacterial packaging paper prepared under certain conditions.

[0066] Figure 4 This is a comparison chart of the antibacterial activity and inhibition rate of antibacterial packaging paper prepared with different coating amounts against Staphylococcus aureus and Escherichia coli in Example 10.

[0067] Figure 5 This is a comparison chart of the antibacterial activity and inhibition rate of antibacterial packaging paper prepared with different amounts of Lig-CIN NPs added in Example 11 against Staphylococcus aureus and Escherichia coli.

[0068] Figure 6 The images show the polydispersity index (PDI), particle size, zeta potential, and transmission electron microscopy (TEM) images of the Lig-CIN NPs suspension in Example 12 during a 15-day storage period.

[0069] Figure 7 The curves showing the cumulative release rate of cinnamaldehyde from Lig-CIN NPs under different temperature conditions in Example 13 are shown.

[0070] Figure 8 The curves showing the cumulative release rate of cinnamaldehyde from the antibacterial packaging paper in Example 14 under different temperature conditions are shown.

[0071] Figure 9 The curve showing the cumulative release rate of cinnamaldehyde from the antibacterial packaging paper in Example 14 under acidic atmosphere conditions.

[0072] Figure 10 This is a comparison of the strawberry preservation effects under different packaging papers during strawberry storage in Example 15.

[0073] Figure 11This is a comparison chart of strawberry hardness, weight loss, brightness, rot index, relative conductivity, soluble solids content, and DPPH free radical scavenging rate under different packaging paper coverings during strawberry storage in Example 15. Detailed Implementation

[0074] The present invention will be further described below with reference to the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0075] The alkyl ketene dimer emulsion used in the following examples was purchased from Yulin Longyuan Chemical Plant Co., Ltd. in Yanjin County. The product model is LY_WA401, with a solid content of 12.5% ​​± 0.5%, a viscosity of 42 mPa·s, a pH value of 4, and is cationic. The polyamide epichlorohydrin resin was purchased from Weifang Huapu Chemical Co., Ltd., and is an emulsion with a solid content of 15%. The cationic polyacrylamide was purchased from Yika (Suzhou) Chemicals Co., Ltd., with a molecular weight of 7 million.

[0076] Example 1

[0077] The preparation process of lignin-loaded cinnamaldehyde nanoparticles specifically includes the following steps:

[0078] (1) Lignin classification: Weigh 5 g of alkali lignin and add it to 100 mL of acetone. Stir magnetically for 8 h at 25℃ and 400 r / min. Then filter under vacuum using a Buchner funnel. The filtrate is the fractionated lignin solution. Remove acetone by rotary evaporation at 60℃ to obtain fractionated lignin solid.

[0079] (2) Cinnamaldehyde loading: Weigh 0.4 g of graded lignin obtained in step (1) and 0.2 g of cinnamaldehyde (CIN) and dissolve them together in 20 mL of acetone (the mass ratio of cinnamaldehyde to lignin is 1:2) to obtain a mixed solution. Under stirring conditions of 25℃ and 400 r / min, the mixed solution is added dropwise to 20 mL of deionized water at a rate of 2 mL / min using a peristaltic pump (the volume ratio of lignin acetone solution to deionized water is 1:1). After the addition is completed, continue stirring for 30 min to obtain a suspension containing lignin-loaded cinnamaldehyde nanoparticles. Then, the suspension is rotary evaporated at 60℃ for 30 min to remove the acetone in the suspension, and a lignin-loaded cinnamaldehyde nanoparticle suspension is obtained, which is named Lig-CIN NPs.

[0080] The cinnamaldehyde encapsulation rate of the lignin-loaded cinnamaldehyde nanoparticles obtained in this embodiment was determined to be 96%.

[0081] Example 2

[0082] The preparation method of lignin-loaded cinnamaldehyde nanoparticles in this embodiment differs from that in Example 1 only in that the mass ratio of cinnamaldehyde to lignin used in the preparation of lignin-loaded cinnamaldehyde nanoparticles in this embodiment is 1:5, that is, 0.1 g of cinnamaldehyde and 0.5 g of graded lignin were used.

[0083] Example 3

[0084] The preparation method of lignin-loaded cinnamaldehyde nanoparticles in this embodiment differs from that in Example 1 only in that the mass ratio of cinnamaldehyde to lignin used in the preparation of lignin-loaded cinnamaldehyde nanoparticles in this embodiment is 1:4, that is, 0.12 g of cinnamaldehyde and 0.48 g of graded lignin were used.

[0085] Example 4

[0086] The preparation method of lignin-loaded cinnamaldehyde nanoparticles in this embodiment differs from that in Example 1 only in that the mass ratio of cinnamaldehyde to lignin used in the preparation of lignin-loaded cinnamaldehyde nanoparticles in this embodiment is 1:1, that is, 0.3 g of cinnamaldehyde and 0.3 g of graded lignin are used.

[0087] Comparative Example 1

[0088] The comparative example of lignin nanoparticle preparation is as follows: 0.4 g of the graded lignin obtained in step (1) of Example 1 was weighed and dissolved in 20 mL of acetone to prepare a lignin-acetone solution with a concentration of 10 mg / mL. Under stirring conditions of 25℃ and 400 r / min, the solution was added dropwise to 20 mL of deionized water at a rate of 2 mL / min using a peristaltic pump (the volume ratio of lignin-acetone solution to deionized water was 1:1). After the addition was complete, stirring was continued for 30 min to obtain a suspension containing lignin nanoparticles. Subsequently, the suspension was rotary evaporated at 60℃ for 30 min to remove the acetone, yielding the lignin nanoparticles.

[0089] The lignin nanoparticles prepared in this comparative example were measured to have an average particle size of 161 nm, a polydispersity index of 0.257, and an absolute value of zeta potential greater than 30 mV, indicating that the nanoparticles have excellent dispersion stability.

[0090] Example 5

[0091] In this embodiment, the antibacterial activity of lignin-loaded cinnamaldehyde nanoparticles (Lig-CIN NPs) prepared in Examples 1 to 4, lignin nanoparticles (LNPs) prepared in Comparative Example 1, and free cinnamaldehyde (CIN) was studied using the plate colony counting method.

[0092] Escherichia coli and Staphylococcus aureus were cultured in LB liquid medium at 37°C and 200 r / min for 18 h with shaking. Then, the activated bacterial suspension was diluted with LB liquid medium to a bacterial concentration of (1 ~ 3) × 10⁻⁶. 8 CFU / mL. Subsequently, the bacterial suspension was serially diluted 10 times. 4 The mixture was thoroughly mixed with a dispersion of Lig-CIN NPs (0.9% physiological saline as the dispersant) (Lig-CIN NPs concentration in the mixture was 1.5 mg / mL), and 100 μL of the mixture was evenly spread on LB agar medium and incubated at 37°C for 24 h. Finally, colonies were counted, the inhibition rate was calculated, and photos were taken to record the antibacterial effect of Lig-CIN NPs. The antibacterial activity of lignin nanoparticles and free cinnamaldehyde was evaluated using the same method as controls. A blank control group was also set up, using physiological saline instead of the Lig-CIN NPs dispersion.

[0093]

[0094] Experimental results are as follows Figure 2 As shown, compared with the blank control, lignin nanoparticles, Lig-CIN NPs, and free cinnamaldehyde all exhibited certain inhibitory effects on Escherichia coli and Staphylococcus aureus, with Lig-CIN NPs showing the most significant antibacterial effect. Further colony counting led to the conclusion that... Figure 2 As shown in b and 2c, at a Lig-CIN NPs concentration of 1.5 mg / mL, the antibacterial rates of lignin nanoparticles and free cinnamaldehyde against *Escherichia coli* were 18% and 25%, respectively, and against *Staphylococcus aureus*, respectively, were 30% and 46%. With increasing cinnamaldehyde to lignin ratio in Lig-CIN NPs, the antibacterial activity of Lig-CIN NPs against *Escherichia coli* and *Staphylococcus aureus* gradually increased. When CIN : LNPs = 1 : 2, the antibacterial rates of Lig-CIN NPs against *Escherichia coli* and *Staphylococcus aureus* reached 83% and 90%, respectively. Compared to other natural antibacterial agents (cinnamaldehyde or lignin), Lig-CIN NPs exhibited particularly superior antibacterial effects against *Escherichia coli* and *Staphylococcus aureus*. Based on the experiment on the effect of the ratio of cinnamaldehyde to lignin on the encapsulation efficiency of cinnamaldehyde, and in order to avoid waste of experimental materials, Lig-CIN NPs prepared with CIN : LNPs = 1 : 2 were finally selected for subsequent research.

[0095] Lig-CIN NPs exhibit better antibacterial effects against *Escherichia coli* and *Staphylococcus aureus* than lignin nanoparticles and free cinnamaldehyde. This is due to the inherent antibacterial properties of lignin and the release of cinnamaldehyde from Lig-CIN NPs, which enhances their antibacterial efficacy. Their superior antibacterial effect against *Staphylococcus aureus* compared to *Escherichia coli* may be attributed to structural differences in bacterial outer membranes. Gram-negative bacteria possess a thick lipopolysaccharide outer membrane covering their cell walls, providing a stronger barrier that effectively prevents Lig-CIN NPs from penetrating and reducing their antibacterial efficacy. Gram-positive bacteria, on the other hand, only have a peptidoglycan layer, allowing Lig-CIN NPs to more easily penetrate the cell wall and reach the cell membrane to exert their effects.

[0096] Example 6

[0097] A method for preparing lignin-loaded cinnamaldehyde nanoparticle antibacterial packaging paper, specifically including the following steps:

[0098] (1) Preparation of coating solution: Cassava starch and deionized water were mixed to prepare a mixture with a starch content of 10 wt%. The mixture was gelatinized in a water bath at 95°C for 30 min and then cooled to room temperature. The lignin-loaded cinnamaldehyde nanoparticles prepared in Example 1, accounting for 2 wt% of the dry weight of the starch, were added to the gelatinized starch and stirred evenly to obtain the coating solution.

[0099] (2) Preparation of base paper: After bleached softwood pulp was decomposed using a fiber standard dissociation machine, it was beaten to 35°SR using a Schubert freeness tester. The pulp concentration was diluted with water to 0.3 wt%, and 0.3 wt% of alkyl ketene dimer emulsion by weight of pulp was added to the pulp. The mixture was stirred for 30 s, then 0.5 wt% of polyamide epichlorohydrin resin by weight of pulp was added and stirred for 15 min. Finally, 0.03 wt% of cationic polyacrylamide by weight of pulp was added and stirred for 1 min. The paper was then formed using a PTI paper machine (PTI RK-2A, Austria) to a basis weight of 60 g / m³. 2 The base paper.

[0100] (3) Coating: Using a wire bar and doctor blade integrated coating tester, the coating liquid was applied at a concentration of 2 g / m³. 2 4 g / m 2 6 g / m 2 and 8 g / m 2 The coating amount is evenly applied to one surface of the base paper. After coating, the sample is placed in a constant temperature and humidity room at 23℃ and 50% relative humidity for 24 hours to equilibrate, thus obtaining antibacterial packaging paper.

[0101] Measurements showed that the coating amount of the coating liquid in this embodiment was 8 g / m². 2 The water vapor transmission coefficient of the antibacterial packaging paper prepared under the specified conditions was 1.23 × 10⁻⁶.-10 g / m·s·Pa, oxygen permeability coefficient is 9.48×10 -13 cm 3 ·cm / cm 2 The tear index is 19.12 mN·m·s·Pa. 2 / g, tensile index is 34.90 N·m / g, burst index is 3.78 kPa·m 2 / g. The gas-phase inhibition rate against Escherichia coli is 80%, and the gas-phase inhibition rate against Staphylococcus aureus is 52%.

[0102] Example 7

[0103] The difference between the preparation method of the antibacterial packaging paper in this embodiment and that in embodiment 6 is only that: in step (1) when preparing the coating liquid, the amount of lignin-loaded cinnamaldehyde nanoparticles added is 1 wt% of the dry weight of starch.

[0104] Example 8

[0105] The difference between the preparation method of the antibacterial packaging paper in this embodiment and that in embodiment 6 is only that: in step (1) when preparing the coating liquid, the amount of lignin-loaded cinnamaldehyde nanoparticles added is 3 wt% of the dry weight of starch.

[0106] Example 9

[0107] The difference between the preparation method of the antibacterial packaging paper in this embodiment and that in embodiment 6 is only that: in step (1) when preparing the coating liquid, the amount of lignin-loaded cinnamaldehyde nanoparticles added is 4 wt% of the dry weight of starch.

[0108] Measurements showed that the coating amount of the coating liquid in this embodiment was 8 g / m². 2 The water vapor transmission coefficient of the antibacterial packaging paper prepared under the specified conditions was 1.15 × 10⁻⁶. -10 g / m·s·Pa, oxygen permeability coefficient is 9.31×10 -13 cm 3 ·cm / cm 2 The tear index is 19.45 mN·m·s·Pa. 2 / g, tensile index is 37.62 N·m / g, burst index is 4.06 kPa·m 2 / g. The gas-phase inhibition rate against Escherichia coli is 96%, and the gas-phase inhibition rate against Staphylococcus aureus is 92%.

[0109] Scanning electron microscope (SEM) images of the surface morphology of antibacterial packaging papers with different coating amounts prepared in this embodiment are shown below. Figure 3 As shown.

[0110] Comparative Example 2

[0111] The difference between the preparation method of the antibacterial packaging paper in this comparative example and that in Example 9 is that lignin-loaded cinnamaldehyde nanoparticles are not added when preparing the coating liquid in step (1).

[0112] Example 10

[0113] Studying the effect of coating amount on the vapor-phase antimicrobial properties of paper has significant theoretical and practical value. Vapor-phase antimicrobial treatment does not rely on direct contact between the material and microorganisms; instead, it achieves a comprehensive antimicrobial effect by releasing active antimicrobial molecules into the surrounding space. For the preservation of fruits and vegetables such as strawberries, vapor-phase antimicrobial treatment has unique advantages. It can effectively act on all surfaces inside the packaging, including the spaces between fruits and between fruits and packaging. These areas are often blind spots for microbial growth and areas that are difficult to effectively cover with direct contact antimicrobial agents. This characteristic makes vapor-phase antimicrobial treatment particularly suitable for solving the problem of cross-contamination caused by irregular fruit and vegetable surfaces and fruit contact.

[0114] This embodiment uses the plate colony counting method to test Example 9, where the coating liquid coating amount is 2 g / m². 2 4 g / m 2 6 g / m 2 and 8 g / m 2 The gas-phase antibacterial activity of antibacterial packaging paper prepared under the specified conditions was determined. Activated *Escherichia coli* and *Staphylococcus aureus* were diluted to 1 ~ 3 × 10⁻⁶. 8 CFU / mL, take 100 μL and spread it evenly on LB agar medium. Cut each antibacterial packaging paper into 1 cm × 1 cm squares, place them inside the lid of the petri dish, and incubate at 37℃ for 24 h. Count the colonies, calculate the inhibition rate, and record the data by taking photos with a mobile phone to observe the antibacterial effect of each antibacterial packaging paper.

[0115] The results are as follows Figure 4As shown, with increasing coating weight, the gas-phase antibacterial effect of the paper against *Escherichia coli* and *Staphylococcus aureus* is significantly enhanced. This phenomenon is mainly due to the fact that increased coating weight means an increase in the total amount of Lig-CIN NPs loaded per unit area of ​​paper, which directly increases the number of cinnamaldehyde molecules available for volatilization. Within the sealed packaging space, these continuously released cinnamaldehyde molecules can form a higher gas-phase concentration, thereby enhancing its inhibitory effect on the two tested bacterial species. Notably, this gas-phase antibacterial system exhibits better inhibitory effects against *E. coli* than against *Staphylococcus aureus*. The core reason lies in the fundamental change in the mode of action of cinnamaldehyde, shifting from direct contact to gas-phase diffusion. When cinnamaldehyde acts in the gas phase, its hydrophobic molecules can directly act on the bacterial cell membrane. For *E. coli*, its outer membrane is rich in lipopolysaccharides; this lipid barrier is an obstacle in direct contact, but becomes the primary target in the gas phase environment. Volatilized cinnamaldehyde molecules can efficiently dissolve, insert into, and destroy this outer membrane, rapidly undermining its barrier function and leading to bacterial death. Conversely, Staphylococcus aureus has a thick cell wall with a dense peptidoglycan structure, strong hydrophilicity, and low lipid content. This structural characteristic results in poor initial adsorption capacity of the bacteria for gaseous cinnamaldehyde molecules. Although this thick wall cannot completely block the entry of cinnamaldehyde, it significantly delays its penetration into the bacterial interior, reducing its effective concentration at the site of action, thus exhibiting a relatively low antibacterial rate.

[0116] In summary, adjusting the coating amount can effectively enhance the gas-phase antibacterial properties of paper, and its inhibitory effect on different bacterial species varies significantly. This finding provides important guidance for the design of strawberry preservation packaging. In practical applications, the characteristics of the target pathogens should be fully considered, and the breadth and intensity of the antibacterial effect should be balanced by optimizing the coating amount.

[0117] Example 11

[0118] Compared to traditional antimicrobial methods limited to direct contact between materials and microorganisms, in-depth research on the regulation of the effect of Lig-CIN NPs dosage on the vapor-phase diffusion antimicrobial properties of paper has significant theoretical and applied value. Direct contact antimicrobial methods are limited in effectiveness within the complex spatial structure of packaging, making it difficult to ensure effective contact between the active surface and all contamination sites, especially the recesses or interfaces of strawberry fruits. Vapor-phase antimicrobial methods, on the other hand, rely on the autonomous volatilization and spatial diffusion of active ingredients, creating a dynamic vapor-phase antimicrobial environment throughout the packaging system, achieving non-contact, full-coverage protection of the target area. This provides a novel solution to addressing the problem of microenvironmental dead zones caused by dense stacking of delicate fruits and vegetables such as strawberries, as well as contact cross-contamination caused by bacteria. Therefore, this embodiment systematically explores the influence of Lig-CIN NPs dosage on the vapor-phase antimicrobial properties of paper.

[0119] This embodiment uses the plate colony counting method to test Examples 6-9 and Comparative Example 2 at a coating liquid coating amount of 8 g / m². 2 The gas-phase antibacterial activity of antibacterial packaging paper prepared under the specified conditions was determined. Activated *Escherichia coli* and *Staphylococcus aureus* were diluted to 1 ~ 3 × 10⁻⁶. 8 CFU / mL, take 100 μL and spread it evenly on LB agar medium. Cut each antibacterial packaging paper into 1cm×1cm squares, place them inside the lid of the petri dish, and incubate at 37℃ for 24 h. Count the colonies, calculate the inhibition rate, and record the data by taking photos with a mobile phone to observe the antibacterial effect of each antibacterial packaging paper.

[0120] The results are as follows Figure 5 As shown, with the increase of Lig-CIN NPs addition, the gas-phase antibacterial effect of the paper against Escherichia coli and Staphylococcus aureus was significantly enhanced. This is mainly because the increase in addition directly increases the effective loading of cinnamaldehyde per unit area of ​​paper, thus providing a more sufficient reserve for its volatilization and establishing a higher concentration of gas-phase antibacterial molecules in a confined space.

[0121] However, this gas-phase antibacterial system consistently showed better inhibitory effects against *Escherichia coli* than against *Staphylococcus aureus*. This phenomenon is closely related to the differences in the cell wall structures of the two bacteria. Cinnamaldehyde molecules primarily target the lipid structure of bacteria. The outer membrane of *E. coli* is rich in lipopolysaccharides, which provides hydrophobic cinnamaldehyde molecules with preferential binding sites, allowing them to more effectively disrupt membrane integrity. Conversely, *Staphylococcus aureus* possesses a thick and dense peptidoglycan layer, which, while not directly a primary target of cinnamaldehyde, can to some extent hinder gas-phase molecules from reaching the cell membrane, thus exhibiting relatively lower sensitivity. Notably, the gas-phase antibacterial rate of coated paper was lower than that of the same mass of directly used free Lig-CIN NPs. This is mainly attributed to the fact that Lig-CIN NPs in the paper are bound within the fibers and coating matrix, and their cinnamaldehyde release is limited by the diffusion of the polymer network; simultaneously, gas-phase molecules must undergo long-range diffusion from the coating to the air and then to the bacterial cells, and losses along the way lead to a decrease in the effective concentration ultimately acting on the bacterial cells.

[0122] Crucially, this study found that the amount of Lig-CIN NPs added plays a more decisive role than the coating amount in determining the effectiveness of gas-phase antibacterial treatment. While increasing the coating amount will thicken the coating, if the proportion of Lig-CIN NPs in the coating is not increased simultaneously, it is equivalent to only diluting the concentration of cinnamaldehyde. The essence of gas-phase antibacterial treatment is the volatilization of cinnamaldehyde molecules, and its driving force directly depends on the local concentration gradient of cinnamaldehyde in the coating. Therefore, directly increasing the amount of Lig-CIN NPs added has a more direct and significant impact on increasing the gas-phase concentration. Furthermore, the coating amount mainly blocks microorganisms by forming a thicker and denser coating, which is a physical barrier mechanism, while the degree of gas-phase antibacterial effect is directly determined by the amount of Lig-CIN NPs added. For gas-phase antibacterial treatment, the amount of Lig-CIN NPs added is more critical than the coating amount. This discovery provides key guidance for designing active packaging for strawberry preservation. While ensuring complete coating adhesion, the addition of Lig-CIN NPs should be maximized rather than simply increasing the coating thickness. This will efficiently build a strong gas-phase antimicrobial protection system and maximize the preservation effect of strawberries.

[0123] Example 12

[0124] Storage stability analysis of Lig-CIN NPs.

[0125] The fresh Lig-CIN NPs suspension prepared in Example 1 was stored at 25°C for 15 days. During this period, samples were taken and diluted to a concentration of 0.01 wt%. The polydispersity index (PDI), particle size, and zeta potential were measured using a nanolaser particle size analyzer to evaluate the storage stability of Lig-CIN NPs at room temperature. The results are as follows: Figure 6 As shown.

[0126] The results showed that Lig-CIN NPs exhibited good stability during storage. Specifically, the PDI value remained around 0.3, indicating a narrow particle size distribution and excellent dispersibility. Furthermore, the particle size initially decreased and then increased, with the initial decrease possibly related to the enhanced interaction between cinnamaldehyde and lignin nanoparticles, leading to a denser particle structure. Zeta potential, a key parameter characterizing the surface charge properties of particles, reflects the strength of electrostatic repulsion or attraction between particles and is a crucial factor affecting the stability of the dispersion system. Generally, an absolute value of zeta potential exceeding 30 mV indicates excellent stability of the nanoparticles. Experiments revealed that the zeta potential of Lig-CIN NPs initially decreased and then increased during storage; the initial decrease in potential indicates strong electrostatic repulsion between particles, effectively suppressing aggregation. Figure 6As shown in Figure d, the transmission electron microscopy image clearly demonstrates that the nanoparticles maintained a good dispersion and spherical morphology after 15 days of storage, with no significant aggregation, fusion, or morphological changes observed. This confirms the excellent storage stability of Lig-CIN NPs. In summary, Lig-CIN NPs exhibit good stability after 15 days of storage at 25°C, providing important evidence for their practical application.

[0127] Example 13

[0128] The lignin-loaded cinnamaldehyde nanoparticle dispersion obtained in Example 1 was added to water and placed in shaking incubators (200 r / min) at 4℃, 25℃ and 37℃ respectively. The supernatant was taken as a sample at 0 h, 4 h, 8 h, 12 h, 24 h, 48 h, 96 h, 144 h and 192 h respectively. The absorbance of the supernatant was measured at 288 nm using a UV spectrophotometer, and the cumulative release rate of cinnamaldehyde was calculated.

[0129] The results are as follows Figure 7 As shown, lignin-loaded cinnamaldehyde nanoparticles exhibited sustained-release characteristics for up to 8 days under three temperature conditions. The cumulative release rate after 8 days was 98% at 37℃, 95% at 25℃, and 67% at 4℃. Release kinetic fitting indicated that the release behavior conformed to a first-order kinetic model, and the release mechanism varied with temperature: at 37℃, Fick diffusion was dominant (n < 0.45), while at 4℃ and 25℃, diffusion and carrier skeleton dissolution were synergistic (n < 0.45). <n<0.89)。

[0130] Example 14

[0131] Example 9 was applied with a coating amount of 8 g / m² in the coating liquid. 2 The antibacterial packaging paper prepared under the specified conditions was cut into 1 cm × 1 cm squares and placed at 4℃, 25℃, and 37℃. Samples were taken at 0 h, 4 h, 8 h, 12 h, 24 h, 48 h, 96 h, 144 h, and 192 h. The samples were fully dispersed in water, and the supernatant was used as the sample. The absorbance of the supernatant was measured at 288 nm using a UV spectrophotometer, and the cumulative release rate of cinnamaldehyde was calculated. The results are as follows. Figure 8 As shown.

[0132] The results showed that the release of cinnamaldehyde from paper was also temperature-dependent, and due to the adsorption and diffusion limitations of the paper fiber network, the release rate was slower than that of lignin-loaded cinnamaldehyde nanoparticles, which is beneficial for achieving long-lasting antibacterial effects.

[0133] Further release tests were conducted under acidic atmospheric conditions (simulating the acid-producing microenvironment of fruits and vegetables after harvesting), specifically, the coating amount of Example 9 in the coating solution was 8 g / m². 2 The antibacterial packaging paper prepared under the specified conditions was placed in an acidic atmosphere at 25°C. Samples were taken at 0 h, 4 h, 8 h, 12 h, 24 h, 48 h, 96 h, 144 h, and 192 h. The samples were fully dispersed in water, and the supernatant was used as the final sample. The absorbance of the supernatant was measured at 288 nm using a UV spectrophotometer, and the cumulative release rate of cinnamaldehyde was calculated. The results are as follows. Figure 9 As shown.

[0134] The results showed that the release rate of cinnamaldehyde was significantly lower than that under neutral conditions, indicating that the acidic environment caused the lignin carrier structure to shrink and densify, enhancing the hydrophobic interaction between the carrier and cinnamaldehyde molecules, thus increasing diffusion resistance. This property allows the packaging paper to automatically adjust the release rate in response to changes in the physiological state of the fruit.

[0135] Example 15

[0136] Strawberries of uniform size and without mechanical damage were randomly divided into three groups: a blank control group (no covering), a base paper group (no coated base paper covering), and an antibacterial paper group (Example 9: the coating amount of the coating liquid was 8 g / m²). 2 Antibacterial packaging paper prepared under the specified conditions was used to cover the strawberries (with the coated side facing the strawberries). All samples were stored at room temperature for 7 days, and the strawberry firmness, weight loss, brightness, decay index, relative conductivity, soluble solids content, and DPPH free radical scavenging rate were measured daily. The experimental results are as follows: Figure 10 and Figure 11 As shown.

[0137] The results showed that after 7 days of storage, the strawberries in the blank control group exhibited severe dehydration and mold, with a decay index of 3.0; the raw paper group showed obvious mold and softening, with a decay index of 2.0; and the antibacterial paper group showed no mold contamination, maintained good color, and had a decay index of only 1.0. The weight loss rate of the antibacterial paper group was only 5%, significantly lower than that of the blank control group (15.6%) and the raw paper group (11.2%). Indicators such as hardness, soluble solids content, and DPPH free radical scavenging rate all indicated that the strawberries in the antibacterial paper group maintained the best quality.

[0138] The above results demonstrate that the lignin-loaded cinnamaldehyde nanoparticle antibacterial packaging paper prepared by this invention has excellent preservation effect and can significantly extend the shelf life of strawberries.

[0139] The method for preparing lignin-loaded cinnamaldehyde nanoparticle antibacterial packaging paper provided by this invention is simple, environmentally friendly, and uses widely available and inexpensive raw materials, making it suitable for industrial production. This invention uses only lignin as the main antibacterial carrier, achieving high-value utilization through graded processing and nanotechnology. This avoids the complex processes of adding multiple components such as metal ions required in existing technologies, resulting in low production costs and environmental friendliness. The resulting antibacterial packaging paper can be widely used in active packaging for fruits, vegetables, and food products, demonstrating promising market prospects and application value.

[0140] This invention provides a concept and method for lignin-loaded cinnamaldehyde nanoparticles, antibacterial packaging paper, and their preparation and application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A lignin-loaded cinnamaldehyde nanoparticle, characterized in that, The lignin-loaded cinnamaldehyde nanoparticles are formed by the synergistic effect of the lignin self-assembly nanoframework and cinnamaldehyde through hydrogen bonding and hydrophobic interactions; the cinnamaldehyde is encapsulated by the lignin self-assembly nanoframework.

2. The lignin-supported cinnamaldehyde nanoparticles according to claim 1, characterized in that, The mass ratio of cinnamaldehyde to lignin is 1:(0.25~4); the particle size of the lignin-loaded cinnamaldehyde nanoparticles is 20~400nm.

3. The method for preparing lignin-loaded cinnamaldehyde nanoparticles according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Add alkali lignin to acetone, mix well, separate solid and liquid, collect the liquid, remove acetone, and obtain graded lignin. Step 2: Cinnamaldehyde and the graded lignin obtained in Step 1 are dissolved in acetone to obtain a second mixture. The second mixture is added dropwise to water to obtain a third mixture. The acetone is removed to obtain a lignin-loaded cinnamaldehyde nanoparticle suspension.

4. The preparation method according to claim 3, characterized in that, In step 1, the solid-liquid ratio of the alkali lignin to the acetone is (40 ~ 60) mg : 1 mL; the mixing method is to stir at 20 ~ 30℃ and 300 ~ 500 r / min for 6 ~ 12 h; the removal of acetone is to remove it by rotary evaporation at 50 ~ 70℃. And / or, In step 2, the mass ratio of cinnamaldehyde to graded lignin is 1:(0.25~4); the concentration of graded lignin in the second mixture is 5~40 mg / mL; the dropwise addition is performed at a flow rate of 1~8 mL / min; the second mixture is added to water at a temperature of 20~30℃ and a stirring speed of 200~600 r / min; the volume ratio of the second mixture to water is 1:(1~3); and the removal of acetone is performed by rotary evaporation at 50~70℃.

5. The application of the lignin-loaded cinnamaldehyde nanoparticles according to claim 1 or 2 in the preparation of antibacterial packaging paper.

6. An antibacterial packaging paper, characterized in that, It includes a paper substrate and an antimicrobial coating loaded on at least one surface of the paper substrate; the antimicrobial coating comprises lignin-loaded cinnamaldehyde nanoparticles as described in claim 1 or 2.

7. The antibacterial packaging paper according to claim 6, characterized in that, The paper matrix is ​​made from bleached softwood pulp; the mass of the paper matrix is ​​50-70 g per square meter; the antibacterial packaging paper has a water vapor transmission coefficient of 1.10 × 10⁻⁶. -10 ~ 1.88×10 -10 g / m·s·Pa, oxygen permeability coefficient is 9.3×10 -13 ~ 9.95×10 -13 cm 3 ·cm / cm 2 • Pa, tear index is 16.7 ~ 19.5 mN·m 2 The tensile index is 33.8 ~ 59.3 N·m / g, and the bursting index is 3.48 ~ 5.23 kPa·m. 2 / g, with a gas phase inhibition rate of not less than 90% against Escherichia coli and not less than 85% against Staphylococcus aureus.

8. The method for preparing antibacterial packaging paper according to claim 6 or 7, characterized in that, Includes the following steps: The lignin-loaded cinnamaldehyde nanoparticles are added to a mixture of film-forming agent and water, mixed well to obtain a coating solution, and the coating solution is uniformly coated on at least one surface of the paper substrate and dried to obtain the final product.

9. The preparation method according to claim 8, characterized in that, The film-forming agent is any one or a combination of starch, carboxymethyl cellulose, and polyvinyl alcohol; the content of the film-forming agent in the mixture of the film-forming agent and water is 5-15 wt%; the amount of lignin-loaded cinnamaldehyde nanoparticles added is 0.5-5% of the mass of the film-forming agent; the coating amount of the coating solution is 2-8 g / m³. 2 Paper matrix; And / or, The preparation method of the paper matrix includes the following steps: bleached softwood pulp is loosened and beaten to 30-40°SR, the pulp concentration obtained after beating is adjusted to 0.2-0.5 wt%, sizing agent, wet strength agent and retention aid are added, stirred evenly to obtain paper stock, papermaking, pressing and drying, and the paper is obtained.

10. The application of the antibacterial packaging paper according to claim 6 or 7 in the preservation of fruits and vegetables.

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