Antibacterial aerogel based on buckwheat hull holocellulose nanofiber emulsion and preparation and application thereof

Abstract

The invention belongs to the technical field of aerogel preparation and relates to antibacterial aerogel based on buckwheat hull holocellulose nanofiber emulsion as well as preparation and application of the antibacterial aerogel. The preparation method comprises the following steps: S1, adding crushed buckwheat hulls into peracetic acid for pretreatment, and then performing washing, dispersion and high-pressure homogenization to obtain a colloidal solution of CNF; s2, taking the colloidal solution of CNF and citral, and performing dispersion mixing and high-pressure homogenization to obtain an antibacterial emulsion; s3, taking the colloidal solution of CNF and sodium periodate, mixing, oxidizing and modifying to obtain a colloidal solution of DNF; s4, mixing the colloidal solution of the DNF with gelatin; and adding the antibacterial emulsion to obtain the antibacterial aerogel. The citral-loaded antibacterial emulsion is loaded on the aerogel matrix, so that the problem of poor matrix compatibility caused by direct addition of citral can be avoided, the defect of low slow release efficiency of hydrophobic components is overcome, the performance of the antibacterial aerogel is improved, and the antibacterial activity of citral is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogel preparation, and relates to an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion, and the preparation and application of the aerogel. Background Art

[0002] During the storage and transportation of fresh food, moisture accumulation due to respiration or environmental changes can trigger microbial spoilage and accelerate the decay of fresh food. Furthermore, external impact can cause quality degradation and economic losses. Therefore, absorbent pads are often used in fresh food storage and transportation to alleviate these problems. However, since absorbent pads lack antimicrobial properties and are difficult to degrade, new antimicrobial products are needed to meet practical needs.

[0003] Citral (3,7-dimethyl-2,6-octadienal), as the main active ingredient in plant essential oils such as lemongrass and Litsea cubeba, has broad-spectrum antibacterial properties and safety, and is widely used in the fields of food preservation and antibacterial. However, citral is easy to volatilize and oxidatively degrade, resulting in poor storage stability of citral; and in order to improve its stability, citral is loaded on a biological matrix material to achieve encapsulation and stabilization of citral. In the disclosed technologies, commonly used biological matrix materials include polysaccharides, proteins, etc.; compared with proteins, polysaccharides have the advantages of safety, non-toxicity, hydrophilicity, stability, low price, and easy degradation, so that polysaccharides can interact with citral, which has more advantages in stabilizing citral. Methods for using polysaccharides to encapsulate and stabilize citral include emulsion systems, self-assembly, and hydrogels, which directly encapsulate free citral. Although these existing methods have improved the stability of citral, there are the following problems with direct encapsulation of citral:

[0004] (1) Citral essential oil is mostly a hydrophobic organic compound, while traditional matrices are often based on hydrophilic materials (such as polysaccharides and proteins). When directly mixed and encapsulated, the hydrophobic-hydrophilic polarity difference between the two phases causes compatibility problems, leading to phase separation (similar to oil-water stratification), destroying the matrix homogeneity and reducing the mechanical strength and stability of the material.

[0005] (2) Citral essential oil contains volatile active ingredients. When directly mixed and encapsulated, the volatilization process is uncontrolled, which not only leads to the rapid loss of antibacterial components and low efficiency of sustained release of hydrophobic components; it also forms a cavity structure inside the matrix, causing material embrittlement or abnormal porosity.

[0006] In summary, directly adding citral essential oil into the system has defects in matrix compatibility and low sustained-release efficiency of hydrophobic components, which leads to decreased performance of the encapsulated material and poor antibacterial activity of citral essential oil. Summary of the Invention

[0007] In view of the above background, the existing method of directly adding citral essential oil into the system has defects in matrix compatibility and low sustained-release efficiency, which leads to decreased material performance after encapsulation and poor antibacterial activity. The present invention provides an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion and its preparation and application.

[0008] This invention uses buckwheat hulls as raw materials, utilizes peracetic acid oxidation in conjunction with high-pressure homogenization to produce a colloidal solution of CNF, then encapsulates citral to produce an antibacterial emulsion. The CNF colloidal solution is further oxidatively modified with sodium periodate to produce a colloidal solution of DNF. Finally, the DNF colloidal solution, gelatin, and the antibacterial emulsion are cross-linked to form an antibacterial aerogel. The invention loads the citral-loaded antibacterial emulsion onto an aerogel matrix, avoiding the poor matrix compatibility associated with direct citral addition while overcoming the low sustained-release efficiency of hydrophobic components. This improves the performance of the antibacterial aerogel, thereby enhancing the antibacterial activity of citral.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion comprises the following steps:

[0011] S1. Preparation of CNF colloidal solution

[0012] The crushed buckwheat hulls are added to peracetic acid and adjusted to a pH of 4.8 to 5.0 for pretreatment, and then washed, dispersed and high-pressure homogenized to obtain a CNF colloidal solution;

[0013] S2. Preparation of antibacterial emulsion

[0014] The CNF colloidal solution and citral in step S1 are dispersed, mixed, and homogenized under high pressure to obtain an antibacterial emulsion; the mass proportion of CNF in the antibacterial emulsion is 0.25% to 0.35%;

[0015] S3. Preparation of DNF colloidal solution

[0016] The CNF colloidal solution in step S1 was mixed with sodium periodate; the pH value was adjusted to 4±0.2, and the mixture was reacted in the dark, followed by dialysis to obtain a DNF colloidal solution; the mass ratio of CNF to sodium periodate was 1:(2.25-2.50)

[0017] S4, antibacterial aerogel

[0018] The DNF colloidal solution and gelatin are mixed in a volume ratio of 1:(1.5-4.5) and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and continued to be stirred, wherein the volume of the antibacterial emulsion is 10%-30% of the total volume of the DNF colloidal solution, gelatin and antibacterial emulsion; then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

[0019] It is further defined that in step S1, the particle size of the crushed buckwheat hulls is 1 mm to 1.25 mm; and the mass ratio of the buckwheat hulls to peracetic acid is 1:(0.35 to 0.40).

[0020] It is further defined that in step S1, the pretreatment conditions are: temperature 80°C to 85°C, time 45min to 50min; dispersion is mechanical defibrillation at a speed of 15000r / min to 16000r / min for 15min to 18min; high-pressure homogenization is performed at a pressure of 300bar to 1000bar for a total of 10 mechanical cycles.

[0021] It is further defined that in step S2, the dispersion mixing is performed at a rotation speed of 15000 r / min to 16000 r / min for 2 to 3 minutes; and the high-pressure homogenization is performed at a pressure of 400 bar to 450 bar for 3 to 4 cycles of homogenization.

[0022] It is further defined that in step S3, the reaction is carried out at a temperature of 50° C. to 55° C. in the dark for 12 to 13 hours; and then dialyzed for 24 to 26 hours to obtain a colloidal solution of DNF.

[0023] It is further defined that in step S4, the stirring conditions are: temperature 60℃~65℃, time 15min~30min; the placement is first placed at a temperature of 60℃~65℃ for 30min~35min, and then placed at 3℃~4℃ for 20min~30min; the pre-freezing temperature is -80℃~-85℃, and the pre-freezing time is 2.5h~3h; the freeze-drying time is 24h~26h.

[0024] The antibacterial aerogel is prepared by utilizing the method for preparing the antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion.

[0025] The antibacterial aerogel is used to improve the antibacterial performance against Staphylococcus aureus, Escherichia coli or Botrytis cinerea.

[0026] The antibacterial aerogel is used as a fresh-keeping pad in food packaging.

[0027] The antibacterial aerogel is used as a fresh-keeping pad in fruit preservation.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses buckwheat hulls as raw materials, utilizes peracetic acid oxidation and high-pressure homogenization to obtain a CNF colloidal solution, then uses the CNF colloidal solution to encapsulate citral to obtain an antibacterial emulsion; further, sodium periodate is used to oxidatively modify the CNF colloidal solution to obtain a DNF colloidal solution; finally, the DNF colloidal solution, gelatin, and antibacterial emulsion are cross-linked to form an antibacterial aerogel. The present invention loads the antibacterial emulsion encapsulating citral onto an aerogel matrix material, which can avoid the poor matrix compatibility problem caused by direct addition of citral essential oil and overcome the low sustained-release efficiency of traditional hydrophobic components; thereby improving the performance of the antibacterial aerogel and enhancing the antibacterial activity of citral.

[0030] 2. In the preparation of antibacterial aerogel, the present invention first utilizes a colloidal solution of DNF and gelatin to form a precursor solution, i.e., an aerogel matrix (denoted as DNF / GE aerogel matrix), and then the antibacterial emulsion encapsulating citral is loaded on the aerogel matrix. The antibacterial aerogel finally formed has high compressive strength, elastic recovery ability, water absorption capacity and oil absorption capacity, and the aldehyde group of DNF and the amino group of GE form a hydrophobic Schiff base bond, which enhances the stability of the structure. When the antibacterial emulsion of citral is loaded on the aerogel matrix, the performance of the antibacterial aerogel is improved, thereby maximizing the antibacterial activity of citral essential oil.

[0031] 3. The present invention has found through research that the antibacterial aerogel has a significant inhibitory effect on Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Botrytis cinerea (B. cinerea).

[0032] 4. Through research, the present invention found that the antibacterial aerogel has excellent antibacterial activity, good biodegradability, and is green and environmentally friendly, and has great potential in food packaging.

[0033] 5. Through research, the present invention found that the sustained release of citral in the antibacterial aerogel inhibits the growth of microorganisms, can effectively delay metabolism, and reduce the decay of fruits; and the encapsulated citral has an inhibitory effect on the activity of pectinase, thereby having the advantage of long-term preservation of fruits.

[0034] 6. The present invention uses buckwheat husk as raw material to prepare full-cellulose nanofiber. Buckwheat husk is widely available and low in cost. It not only realizes the high-value utilization of agricultural waste and conforms to the concept of sustainable development, but also provides a reference for the high-value utilization of biomass resources and the sustainable development of the food industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The stress-strain curves of aerogels in different examples;

[0036] Figure 2 Hardness and elasticity of aerogels in different examples;

[0037] Figure 3 The stability of different examples of aerogels immersed in water / oil;

[0038] Figure 4 The water absorption capacity of aerogels of different examples (the inset is the corresponding side view);

[0039] Figure 5 The oil absorption capacity of aerogels in different examples (the inset is the corresponding side view);

[0040] Figure 6 Fourier transform infrared spectra of different examples of aerogels;

[0041] Figure 7 The following are scanning electron microscope images of aerogels from different examples (Examples 5 to 8).

[0042] Figure 8 is the hardness and elasticity of the loaded emulsion aerogel;

[0043] Figure 9 is the compression behavior of C2 aerogel;

[0044] Figure 10 The antibacterial ability of different examples of aerogels against Staphylococcus aureus, Escherichia coli, and Botrytis cinerea;

[0045] Figure 11 The biodegradability of aerogels from different examples in a natural soil environment at a depth of 10 cm (Control is a commercially available fresh-keeping mat, and C2 aerogel is Example 7);

[0046] Figure 12 Changes in the appearance of strawberries during storage at room temperature;

[0047] Figure 13 The brightness of strawberries during storage at room temperature;

[0048] Figure 14 is the total color difference of strawberries during storage at room temperature;

[0049] Figure 15 is the weight loss of strawberries during storage at room temperature;

[0050] Figure 16 is the firmness of strawberries during storage at room temperature;

[0051] Figure 17 The change in total viable bacterial count during storage of strawberries at room temperature;

[0052] Figure 18A photograph of a plate of strawberries during storage at room temperature. DETAILED DESCRIPTION

[0053] The present invention will be described in further detail below with reference to the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto. Other methods for preparing the compounds of the present invention are considered to be within the scope of the present invention by making some conventional modifications to the reaction conditions of the present invention.

[0054] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0055] Technologies, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies, methods, and equipment should be considered part of the specification.

[0056] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention / invention.

[0057] The technical idea of ​​the present invention is: using buckwheat hull as raw material, using peracetic acid oxidation and high-pressure homogenization technology to prepare a colloidal solution of CNF, CNF refers to buckwheat hull full cellulose nanofiber; then using the colloidal solution of CNF to encapsulate citral to obtain an antibacterial emulsion (also known as Pickering emulsion); further using sodium periodate to oxidatively modify buckwheat hull full cellulose nanofiber (CNF) to obtain a colloidal solution of DNF, DNF refers to buckwheat hull dialdehyde full cellulose nanofiber; finally, the colloidal solution of DNF and gelatin form a precursor solution (also known as DNF / GE aerogel matrix), and cross-linked with the antibacterial emulsion, the antibacterial emulsion is loaded on the DNF / GE aerogel matrix to form an antibacterial aerogel. The present invention encapsulates citral essential oil in the colloidal solution of CNF in the form of a Pickering emulsion, and further loads it on the DNF / GE aerogel matrix material, which can simultaneously achieve moisture adsorption, physical buffering and long-term antibacterial properties, so that the antibacterial performance of citral essential oil is improved. This can not only avoid the matrix compatibility problems caused by the direct addition of citral essential oil, but also overcome the defect of low sustained-release efficiency of traditional hydrophobic ingredients, providing innovative ideas for the preservation of fresh food.

[0058] The present invention provides a method for preparing an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion, comprising the following steps:

[0059] S1. Preparation of CNF colloidal solution

[0060] The crushed buckwheat hulls are added to peracetic acid and adjusted to a pH of 4.8-5.0 for pretreatment, and then washed, dispersed and high-pressure homogenized to obtain a CNF colloidal solution.

[0061] In step S1 of the present invention, the particle size of the crushed buckwheat hulls is 1 mm to 1.25 mm; and the mass ratio of buckwheat hulls to peracetic acid is 1:(0.35 to 0.40).

[0062] In step S1 of the present invention, the pretreatment conditions are: temperature 80°C to 85°C, time 45min to 50min; dispersion is mechanical defibrillation at a speed of 15000r / min to 16000r / min for 15min to 18min; high-pressure homogenization is performed at a pressure of 300bar to 1000bar for a total of 10 mechanical cycles.

[0063] S2. Preparation of antibacterial emulsion

[0064] The CNF colloidal solution and citral in step S1 are dispersed, mixed and homogenized under high pressure to obtain an antibacterial emulsion.

[0065] In the present invention, the mass percentage of CNF in the antibacterial emulsion is 0.25% to 0.35%. Therefore, in the examples, the mass of the CNF colloidal solution and citral added is calculated based on the mass percentage of CNF in the final antibacterial emulsion. Exemplarily, the mass percentage of CNF in the antibacterial emulsion is 0.25%, 0.28%, 0.30%, 0.32%, or 0.35%.

[0066] In step S2 of the present invention, the dispersion mixing is performed at a rotation speed of 15000 r / min to 16000 r / min for 2 to 3 minutes; and the high-pressure homogenization is performed at a pressure of 400 bar to 450 bar for 3 to 4 cycles of homogenization.

[0067] S3. Preparation of DNF colloidal solution

[0068] The CNF colloidal solution in step S1 is mixed with sodium periodate; the pH value is adjusted to 4±0.2, and the mixture is reacted in the dark, followed by dialysis to obtain a DNF colloidal solution.

[0069] In the present invention, when the CNF colloidal solution and sodium periodate are mixed, the amount of CNF colloidal solution added is calculated based on the amount of CNF contained therein, i.e., the amount of buckwheat hull holocellulose nanofibers. Preferably, the mass ratio of CNF to sodium periodate is 1:(2.25-2.50). Exemplarily, the mass ratio of CNF to sodium periodate is 1:2.25, 1:2.30, 1:2.35, 1:2.40, 1:2.45, or 1:2.50.

[0070] In step S3 of the present invention, the reaction is carried out at a temperature of 50° C. to 55° C. in the dark for 12 to 13 hours; and then dialyzed for 24 to 26 hours to obtain a colloidal solution of DNF.

[0071] S4, antibacterial aerogel

[0072] The DNF colloidal solution and gelatin are mixed in a volume ratio of 1:(1.5-4.5) and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and continued to be stirred, wherein the volume of the antibacterial emulsion is 10%-30% of the total volume of the DNF colloidal solution, gelatin and antibacterial emulsion; then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

[0073] Illustratively, the colloidal solution of DNF and gelatin have a volume ratio of 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, 1:4.0 or 1:4.5.

[0074] In step S4 of the present invention, the stirring conditions are: temperature 60°C to 65°C, time 15min to 30min; the placing is first placing at a temperature of 60°C to 65°C for 30min to 35min, and then placing at 3°C ​​to 4°C for 20min to 30min; the pre-freezing temperature is -80°C to -85°C, and the pre-freezing time is 2.5h to 3h; and the freeze-drying time is 24h to 26h.

[0075] The present invention also provides an antibacterial aerogel prepared by the above-mentioned method for preparing an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion, which can improve the antibacterial performance against Staphylococcus aureus, Escherichia coli or Botrytis cinerea; has biodegradable properties and can be used as a fresh-keeping pad in food packaging; it can also be used as a fresh-keeping pad in fruit preservation.

[0076] The technical solution provided by the present invention is described in detail below, and the performance of the prepared aerogel is studied through testing.

[0077] It should be noted that, in the following examples, unless otherwise specified, the chemicals and reagents used are all conventional commercial products in the art.

[0078] It should be noted that in the following examples, unless otherwise specified, the operations used are all conventional operations; for example, the operating temperature is room temperature unless otherwise specified. The test methods are all standard test methods available in the art unless otherwise specified.

[0079] In the present invention, the antibacterial emulsion (Pickering emulsion) is loaded on the bio-based aerogel material (i.e., DNF / GE aerogel matrix). Therefore, the properties of the bio-based aerogel material have a great influence on the performance and antibacterial effect of the antibacterial aerogel. Therefore, the ratio of the bio-based aerogel material is optimized through experiments.

[0080] Step 1: Preparation of buckwheat hull cellulose nanofibers (CNF)

[0081] First, the buckwheat hulls were washed and dried, then crushed and passed through a 16-mesh sieve to obtain buckwheat hull powder with a particle size of 1.25 mm.

[0082] Next, buckwheat hull powder was added to peracetic acid at a ratio of 0.35 g peracetic acid per 1 g of buckwheat hull. Preferably, the solute content in the peracetic acid was 4% (w / v). The pH was then adjusted to 4.8 with 2 mol / L sodium hydroxide and pretreated at 85°C for 45 minutes. This pretreatment step was repeated three times until the yellow-brown color faded. The solution was initially rinsed with 0.01 mol / L sodium hydroxide and then thoroughly rinsed with deionized water to remove residual chemicals. The solution was then mechanically defibrillated at 16,000 rpm for 15 minutes and diluted with deionized water to 1% (w / v). A high-pressure homogenizer was then used to homogenize the solution at 300 bar (three times), 600 bar (three times), 900 bar (three times), and 1000 bar (one time) to produce a colloidal solution of CNF.

[0083] Step 2: Preparation of buckwheat hull dialdehyde cellulose nanofibers (DNF)

[0084] A colloidal solution of CNF and sodium periodate was mixed at a mass ratio of 1:2.25 to ensure a solid content of 13% (w / v). The pH was adjusted to 4 and the mixture was reacted at 50°C in the dark for 12 hours. The mixture was then dialyzed for 24 hours to produce a colloidal solution of DNF.

[0085] Step 3: Preparation of composite aerogel

[0086] First, the concentrations of the DNF colloidal solution and gelatin (GE) were adjusted to 1% (w / v) and 2% (w / v), respectively.

[0087] Secondly, the colloidal solution of DNF and gelatin were mixed in a certain volume ratio and stirred at 60°C for 30 minutes. The resulting mixture was poured into a mold, first placed at 60°C for 30 minutes and then at 4°C for 30 minutes to promote cross-linking. Finally, it was pre-frozen at -80°C for 3 hours and freeze-dried for 24 hours to obtain the DNF / GE aerogel matrix, i.e., the composite aerogel.

[0088] At the same time, in this step, the CNF colloidal solution prepared in the first step was used as a control, that is, the CNF colloidal solution was directly mixed with gelatin according to a certain volume ratio to prepare a composite aerogel.

[0089] In this step, the colloidal solution of DNF (or the colloidal solution of CNF) and gelatin are set in the following groups according to a certain volume ratio:

[0090] Group 1: The volume ratio of DNF colloidal solution (or CNF colloidal solution) to gelatin is 1:1.5; the prepared composite aerogel is named D1:1.5 (or C1:1.5).

[0091] Group 2: The volume ratio of DNF colloidal solution (or CNF colloidal solution) to gelatin is 1:3.0; the prepared composite aerogel is named D1:3.0 (or C1:3.0).

[0092] Group 3: The volume ratio of the DNF colloidal solution (or CNF colloidal solution) to gelatin was 1:4.5; the prepared composite aerogel was named D1:4.5 (or C1:4.5).

[0093] Group 4: The volume ratio of DNF colloidal solution (or CNF colloidal solution) to gelatin is 1:0; the prepared aerogel is named DNF (or CNF)

[0094] Group 5: The volume ratio of DNF colloidal solution (or CNF colloidal solution) to gelatin was 0:1; the prepared aerogel was named GE.

[0095] The properties of the composite aerogels (or aerogels) prepared under the above different volume ratios were studied.

[0096] Figure 1 is the stress-strain curve of composite aerogel (or aerogel) at different volume ratios; Figure 2 The hardness and elasticity change curves of composite aerogels (or aerogels) at different volume ratios.

[0097] Figure 1 In the figure, the stress-strain curve of the aerogel when the compressive strain is loaded to 65% shows the deformation behavior of the composite aerogel. When the volume ratio of CNF:GE and DNF:GE is 1:1.5, the composite aerogel has a stress of 1.58MPa and 0.61MPa respectively at the compressive strength of 65% strain, and the stress increases with the increase of gelatin (GE) proportion. Figure 2As can be seen, due to differences in chemical composition and structure, aerogels formed from pure CNF or pure DNF exhibit very low hardness and are virtually unable to withstand external pressure. However, the addition of gelatin in varying proportions to pure CNF or pure DNF significantly enhances the compressive resistance of the composite aerogels, demonstrating that the GE chains act as reinforcing agents, partially absorbing the external pressure exerted on the composite aerogels. Aerogels formed from pure CNF are soft and fluffy, exhibiting some shape recovery. However, the addition of GE hinders the flexibility of the CNF chains, resulting in a slight decrease in the elasticity of the composite aerogels. However, compared to pure DNF, the elasticity of the D1:1.5 and D1:3 aerogels is significantly enhanced, due to the formation of a covalent crosslinked network formed by the reaction of GE and DNF. However, an excessive GE content in the system results in insufficient imine and hydrogen bonds, resulting in a decrease in the elasticity of the D1:4.5 composite aerogel.

[0098] Figure 3 Figure 3 shows the stability of composite aerogels (or aerogels) immersed in water / oil at different volume ratios. Pure DNF and pure CNF disintegrate immediately upon contact with water and after 2 hours, respectively. Pure GE and C1:1.5 composite aerogels exhibit incomplete dispersion after 12 hours. C1:3 and C1:4.5 composite aerogels continuously swell with water, maintaining a cylindrical structure but with a significant increase in diameter. Polar water molecules form hydrogen bonds with the hydrophilic groups of the aerogels, weakening the forces between polymer chains and causing the structure to swell or even disintegrate. In contrast, composite aerogels formed from a colloidal solution of DNF and gelatin maintain their original structure after 24 hours of immersion in water. This is because the aldehyde groups of DNF and the amino groups of GE form hydrophobic Schiff base bonds, enhancing structural stability. Furthermore, all composite aerogels are more stable in oil than in water, indicating that non-polar solvents do not disrupt van der Waals forces or hydrophobic interactions between polymer chains, thus preventing swelling or dispersion.

[0099] Figure 4 is the water absorption capacity of the composite aerogel (or aerogel) at different volume ratios; Figure 5 The oil absorption capacity of composite aerogel (or aerogel) at different volume ratios; the illustrations are all corresponding side views. Figure 4 and Figure 5It can be seen that the composite aerogel has a higher water absorption capacity than its oil absorption capacity, which is related to the fact that hydroxyl and amino groups are naturally hydrophilic groups. D1:1.5 exhibits slight collapse after absorbing water (as shown in the side view). This is because the pore wall structure of the composite aerogel at this volume ratio is not strong enough to withstand the pressure of excessive water. Therefore, although the composite aerogel formed with a D1:1.5 ratio has improved structurally, it still has fewer Schiff base bonds, resulting in a weaker pore wall structure. In contrast, D1:3 and D1:4.5 maintain their original structure, exhibiting only slight expansion. The D1:3 aerogel has a water and oil absorption capacity of 32.61 g / g and 28.45 g / g, respectively, which is superior to previously reported aerogel properties. Meanwhile, D1:4.5 exhibits slightly weaker adsorption performance, which is due to the excessive proportion of gelatin GE, which reduces crosslinking and weakens hydrogen bonding.

[0100] Taking into account the above preferred experiments: when the colloidal solution of DNF (or the colloidal solution of CNF) is mixed with gelatin at a volume ratio of 1:3.0, the obtained composite aerogel has better performance.

[0101] Furthermore, the composite aerogel (D1:3) and aerogel (DNF, CNF and GE) were tested for their Fourier transform infrared spectra, as shown in Figure 2. Figure 6 As shown in the DNF spectrum, 1727cm -1 and 880cm -1 The characteristic peaks at 3342 cm represent the carbonyl group and the hemiacetal bond, respectively. The relative intensity increase indicates that the aldehyde group is formed after periodate oxidation. In addition, the peak representing the OH stretching vibration increases from 3342 cm -1 The peak shifted to higher wavenumbers and decreased in intensity, which was attributed to the reduction of hydrogen bonds and the oxidation of some hydroxyl groups to aldehyde groups. -1 、1528cm -1 and 1237cm -1 The characteristic peaks at 1727 cm are attributed to C=O stretching vibration (amide I), NH bending vibration (amide II) and NH stretching (amide III). However, after GE is cross-linked with DNF, the peaks at 1727 cm -1 The intensity of the characteristic peak at 1634 cm -1 The peak intensity near 1540 cm -1 The peak intensity near the α-H phase increases, which is related to the C=N stretching vibration of the Schiff base.

[0102] After further optimization tests, the following examples were set up, in which a composite aerogel prepared by a colloidal solution of DNF (or a colloidal solution of CNF) and gelatin with a volume ratio of 1:3.0 was used as a bio-based aerogel material, and cross-linked with antibacterial emulsions of different volumes to prepare antibacterial aerogels; and its performance was studied.

[0103] Example 1

[0104] This embodiment provides a method for preparing an antibacterial aerogel based on buckwheat hull cellulose nanofiber emulsion, comprising the following steps:

[0105] S1. Preparation of CNF colloidal solution

[0106] The crushed buckwheat hulls were added to peracetic acid and adjusted to a pH of 4.8 for pretreatment, and then washed, dispersed and pretreated by high-pressure homogenization to obtain a colloidal solution of CNF.

[0107] The specific steps of pre-treating buckwheat hulls to obtain CNF colloidal solution are as follows:

[0108] First, the buckwheat hulls were washed and dried, then crushed and passed through a 16-mesh sieve to obtain a particle size of 1.25 mm.

[0109] Next, crushed buckwheat hulls were added to peracetic acid at a ratio of 0.35g peracetic acid per 1g of buckwheat hulls, preferably with a solute content of 4% (w / v). The pH was then adjusted to 4.8 with 2mol / L sodium hydroxide and pretreated at 85°C for 45 minutes. This pretreatment step was repeated three times until the yellow-brown color faded. The hulls were initially rinsed with 0.01mol / L sodium hydroxide and then thoroughly rinsed with deionized water to remove residual chemicals. The hulls were then mechanically defibrillated at 16,000 rpm for 15 minutes and diluted with deionized water to 1% (w / v). A high-pressure homogenizer was then used to homogenize the hulls at 300 bar (three times), 600 bar (three times), 900 bar (three times), and 1000 bar (one time) to produce a colloidal solution of CNF.

[0110] S2. Preparation of antibacterial emulsion

[0111] The CNF colloidal solution and citral in step S1 are dispersed, mixed, and homogenized under high pressure to obtain an antibacterial emulsion; the mass proportion of CNF in the antibacterial emulsion is 0.35%.

[0112] In this step, the specific process of preparing the antibacterial emulsion is:

[0113] Citral was used as the oil phase and the colloidal solution of CNF was used as the aqueous phase. According to the calculation that the final concentration of CNF in the final antibacterial emulsion was 0.35% (w / v), the colloidal solution of CNF was added to citral, and a high-speed disperser was used to disperse and mix at a speed of 16000 r / min for 2 minutes to obtain a coarse emulsion. Then, a high-pressure homogenizer was used to circulate 3 times at a pressure of 450 bar to obtain a fine emulsion, which was the antibacterial emulsion.

[0114] S3. Preparation of DNF colloidal solution

[0115] The CNF colloidal solution in step S1 was mixed with sodium periodate; the pH value was adjusted to 4, and the mixture was reacted in the dark, followed by dialysis to obtain a DNF colloidal solution; the mass ratio of CNF to sodium periodate was 1:2.25.

[0116] Specifically, a colloidal solution of CNF and sodium periodate were mixed at a mass ratio of 1:2.25. The pH value was adjusted to 4, and the mixture was reacted at 50°C in the dark for 12 hours. The mixture was then dialyzed for 24 hours to obtain a colloidal solution of DNF.

[0117] S4. Preparation of antibacterial aerogel

[0118] The DNF colloidal solution and gelatin are mixed according to a volume ratio and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and stirred continuously; and then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

[0119] In this step, the specific process of preparing antibacterial aerogel is:

[0120] First, the concentrations of the DNF colloidal solution and gelatin were adjusted to 1% (w / v) and 2% (w / v), respectively.

[0121] Secondly, the colloidal solution of DNF and gelatin were mixed in a volume ratio of 1:3 and stirred at 60°C for 30 minutes to form a precursor solution; then, an antibacterial emulsion accounting for 10% of the total volume was added and stirred at 60°C for 15 minutes; the resulting mixture was poured into a mold, first placed at 60°C for 30 minutes and then at 4°C for 30 minutes to promote cross-linking; finally, it was pre-frozen at -80°C for 3 hours and freeze-dried for 24 hours to obtain an antibacterial aerogel named C1.

[0122] Example 2

[0123] This embodiment provides a method for preparing an antibacterial aerogel based on buckwheat hull cellulose nanofiber emulsion, comprising the following steps:

[0124] S1. Preparation of CNF colloidal solution

[0125] The crushed buckwheat hulls were added to peracetic acid and adjusted to a pH of 4.8 for pretreatment, and then washed, dispersed, and pretreated by high-pressure homogenization to obtain a colloidal solution of CNF. The specific steps of this step are the same as those in Example 1.

[0126] S2. Preparation of antibacterial emulsion

[0127] The CNF colloidal solution and citral in step S1 are dispersed, mixed, and homogenized under high pressure to obtain an antibacterial emulsion. In this step, the specific process for preparing the antibacterial emulsion is the same as that in Example 1.

[0128] S3. Preparation of DNF colloidal solution

[0129] The CNF colloidal solution in step S1 is mixed with sodium periodate; the pH value is adjusted to 4, and the mixture is reacted in the dark, followed by dialysis to obtain a DNF colloidal solution; the specific steps of this step are the same as those in Example 1.

[0130] S4. Preparation of antibacterial aerogel

[0131] The DNF colloidal solution and gelatin are mixed according to a volume ratio and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and stirred continuously; and then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

[0132] In this step, the specific process of preparing the antibacterial aerogel refers to Example 1, except that an antibacterial emulsion accounting for 20% of the total volume is added; the antibacterial aerogel finally obtained is named C2.

[0133] Example 3

[0134] This embodiment provides a method for preparing an antibacterial aerogel based on buckwheat hull cellulose nanofiber emulsion, comprising the following steps:

[0135] S1. Preparation of CNF colloidal solution

[0136] The crushed buckwheat hulls were added to peracetic acid and adjusted to a pH of 4.8 for pretreatment, and then washed, dispersed, and pretreated by high-pressure homogenization to obtain a colloidal solution of CNF. The specific steps of this step are the same as those in Example 1.

[0137] S2. Preparation of antibacterial emulsion

[0138] The CNF colloidal solution and citral in step S1 are dispersed, mixed, and homogenized under high pressure to obtain an antibacterial emulsion. In this step, the specific process for preparing the antibacterial emulsion is the same as that in Example 1.

[0139] S3. Preparation of DNF colloidal solution

[0140] The CNF colloidal solution in step S1 is mixed with sodium periodate; the pH value is adjusted to 4, and the mixture is reacted in the dark, followed by dialysis to obtain a DNF colloidal solution; the specific steps of this step are the same as those in Example 1.

[0141] S4. Preparation of antibacterial aerogel

[0142] The DNF colloidal solution and gelatin are mixed according to a volume ratio and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and stirred continuously; and then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

[0143] In this step, the specific process of preparing the antibacterial aerogel is referred to Example 1, except that an antibacterial emulsion accounting for 30% of the total volume is added; the antibacterial aerogel finally obtained is named C3.

[0144] The performance of the antibacterial aerogels prepared in Examples 1 to 3 above was further tested. In order to demonstrate the advantages of the technical solution of the present invention, the following comparative examples were designed.

[0145] Comparative Example 1

[0146] This comparative example provides a method for preparing a composite aerogel, comprising the following steps:

[0147] S1. Preparation of buckwheat hull cellulose nanofibers (CNF)

[0148] The crushed buckwheat hulls were added to peracetic acid and adjusted to a pH of 4.8 for pretreatment, and then washed, dispersed, and pretreated by high-pressure homogenization to obtain colloidal CNF. The specific steps of this step are the same as those in Example 1.

[0149] S2. Preparation of dialdehyde cellulose nanofibers (DNF) from buckwheat hulls

[0150] The colloidal solution of CNF was mixed with sodium periodate at a mass ratio of 1:2.25. The pH was adjusted to 4 and the mixture was allowed to react at 50°C in the dark for 12 hours. The mixture was then dialyzed for 24 hours to obtain colloidal DNF.

[0151] S3. Preparation of composite aerogel

[0152] The concentrations of the DNF colloidal solution and GE solution were adjusted to 1% (w / v) and 2% (w / v), respectively; then, they were stirred at 60°C for 30 min at a volume ratio of 1:3.0; the resulting mixture was poured into a mold, first placed at 60°C for 30 min, and then at 4°C for 30 min to promote cross-linking; finally, it was pre-frozen at -80°C for 3 h and freeze-dried for 24 h to obtain a composite aerogel, named A.

[0153] Comparative Example 2

[0154] This comparative example provides a method for preparing an antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion, comprising the following steps:

[0155] S1. Preparation of CNF colloidal solution

[0156] The crushed buckwheat hulls were added to peracetic acid and adjusted to a pH of 4.8 for pretreatment, and washed, dispersed, and pretreated by high-pressure homogenization to obtain a colloidal solution of CNF.

[0157] S2. Preparation of antibacterial emulsion

[0158] Free citral was used as the oil phase and distilled water was used as the aqueous phase; referring to the volume ratio of Example 1, water was added to citral, and a high-speed disperser was used to mix at a speed of 16000 r / min for 2 minutes to obtain a coarse emulsion, and then a high-pressure homogenizer was used to circulate 3 times at a pressure of 450 bar to obtain a fine emulsion, which was an antibacterial emulsion.

[0159] S3. Preparation of DNF colloidal solution

[0160] Specifically, a colloidal solution of CNF and sodium periodate were mixed at a mass ratio of 1:2.25, the pH value was adjusted to 4, and the mixture was reacted at 50°C in the dark for 12 hours, followed by dialysis for 24 hours to obtain a colloidal solution of DNF.

[0161] S4. Preparation of antibacterial aerogel

[0162] The DNF colloidal solution and gelatin in step S3 are mixed in a volumetric ratio and stirred to form a precursor solution. The antibacterial emulsion from step S2 is then added and stirred continuously. The solution is then allowed to stand, pre-frozen, and freeze-dried to produce an antibacterial aerogel. The specific process for preparing the antibacterial aerogel in this step is similar to that in Example 1, resulting in an antibacterial aerogel designated B.

[0163] The performance tests of the antibacterial aerogels (C1-C3) prepared in Examples 1-3 and the antibacterial aerogels (A and B) prepared in Comparative Examples 1-2 are as follows.

[0164] Test 1

[0165] The antibacterial aerogels (C1-C3) prepared in Examples 1-3, the composite aerogel prepared in Comparative Example 1 (named A), and the antibacterial aerogel (B) prepared in Comparative Example 2 were used as test samples, and scanning electron microscope images were obtained, as shown in FIG. Figure 7 shown.

[0166] See also Figure 7In the comparative example 1, the composite aerogel (A) exhibited a well-defined three-dimensional porous structure and morphology. Antibacterial aerogel (B) prepared by directly adding citral essential oil to an aqueous solution exhibited an irregular structure with some network lamellae broken. This was due to the hydrophobic nature of the essential oil affecting the compatibility of the precursor solution, and its rapid volatilization in a free state destroyed the final aerogel network. In contrast, a stable emulsion of citral essential oil encapsulated with CNF was prepared and then added to a matrix to form an aerogel. Because CNF provides an insulating and protective barrier for citral, and the hydroxyl groups on the CNF surface increase the degree of crosslinking, the resulting aerogel framework remained ordered (as shown in C1). As the amount of emulsion added increased, the total solids content per unit volume increased, resulting in denser aerogel pore walls (as shown in C2 and C3). As can be seen, the large amount of citral essential oil successfully loaded onto the aerogel matrix formed clearly visible large pores after volatilization, yet the aerogel network structure remained robust. This demonstrates that emulsion encapsulation using CNF is an effective method for preparing citral essential oil antibacterial aerogels.

[0167] Test 2

[0168] The antibacterial aerogels (C1-C3) prepared in Examples 1-3, the composite aerogel (A) prepared in Comparative Example 1, and the antibacterial aerogel (B) prepared in Comparative Example 2 were used as test samples to investigate the hardness, elasticity, and compression behavior of the test samples. Figure 8 and Figure 9 shown; Figure 8 for hardness and elasticity; Figure 9 Compression behavior of the antibacterial aerogel prepared in Example 2.

[0169] See also Figure 8 Directly adding citral essential oil to water damages the internal structure of the composite aerogel, resulting in a decrease in its compressive strength. Compared to composite aerogel (A), the compressive strength of the antibacterial emulsion-loaded aerogels (Examples 1-3) improved. This is because, on the one hand, the increased total solids content per unit volume makes the pore walls of the antibacterial aerogels denser, making them more resistant to damage. On the other hand, due to hydrogen bonds formed between the hydroxyl groups of CNF and the amino / hydroxyl groups of GE / DNF, the CNF, while encapsulating the citral essential oil, acts as a crosslinker, enhancing the mechanical properties of the antibacterial aerogel.

[0170] See also Figure 9During the loading of the antimicrobial emulsion into the aerogel matrix, the antimicrobial emulsion restricted the free rotation and extension of the aerogel molecular chains. Furthermore, the pores formed by the volatilization of citral altered the stress distribution within the aerogel, preventing the aerogel from deforming uniformly and smoothly under pressure. However, during compression testing, the elasticity and recoverability of the antimicrobial aerogel prepared in Example 2 remained clearly visible. Therefore, DNF / GE-based aerogels loaded with citral emulsion can play a supporting and protective role in food packaging applications.

[0171] Test 3

[0172] The antibacterial aerogels (C1-C3) prepared in Examples 1-3, the composite aerogel (A) prepared in Comparative Example 1, and the antibacterial aerogel (B) prepared in Comparative Example 2 were used as test samples to investigate their antibacterial abilities against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Botrytis cinerea (B. cinerea). Figure 10 shown.

[0173] See also Figure 10 , no antibacterial effect was observed for the composite aerogel (A) prepared in comparative example 1; the antibacterial effect of the antibacterial aerogel (B) prepared in comparative example 2 was relatively small; the antibacterial aerogels prepared in Examples 1 to 3 all showed clear inhibition zones, indicating that antibacterial emulsion encapsulation can more effectively prevent the rapid volatilization of essential oils. When the antibacterial emulsion addition amount was 10%, the antibacterial zone diameters of the antibacterial aerogel (C1) against S. aureus and E. coli were 29.24±0.95mm and 19.84±0.93mm, respectively; as the amount of antibacterial emulsion added increased, the inhibition zone expanded accordingly. For the volatile antibacterial test, the antibacterial aerogels prepared in Examples 2 and 3 were able to completely inactivate nearly 5 logarithms of S. aureus. The results showed that the antibacterial property of the antibacterial aerogel came from citral essential oil, and its effect on Gram-positive bacteria was better. Since Botrytis cinerea is the most common fungus causing strawberry losses, the volatile antifungal properties of the antimicrobial aerogels were evaluated. Compared to the composite aerogels prepared in Comparative Example 1, the antimicrobial aerogels prepared in Comparative Example 2 and Example 1 inhibited bacterial colony growth, while the antimicrobial aerogels prepared in Examples 2 and 3 completely inactivated mold spores. This demonstrates that the antimicrobial aerogels prepared in this example also exhibit significant antifungal activity, and this inhibitory effect increases with increasing citral content.

[0174] Test 4

[0175] The antibacterial aerogel (C2) prepared in Example 2 was used as a test sample to investigate its biodegradability in a natural soil environment at a depth of 10 cm. During the entire experiment, the soil temperature was between -7°C and 10°C, and the humidity was between 50% and 70%. A commercially available fresh-keeping mat was used as a control. Figure 11 shown.

[0176] See also Figure 11 After 20 days, the control group (commercially available fresh-keeping mat) showed no significant degradation, maintaining its original structure. However, the antimicrobial aerogel (C2) prepared in Example 2 showed almost no residue, as soil moisture and microorganisms accelerated its decomposition. These results demonstrate that the antimicrobial aerogels formed from gelatin and DNF exhibit excellent biodegradability, are environmentally friendly, and hold great potential for food packaging.

[0177] Test 5

[0178] The antibacterial aerogel (C2) prepared in Example 2, the composite aerogel (A) prepared in Comparative Example 1, and the antibacterial aerogel (B) prepared in Comparative Example 2 were used as test samples. The test samples were used as fresh-keeping pads to preserve strawberries, thereby investigating the effects of the test samples on the performance of perishable fruits.

[0179] Experimental group design: no fresh-keeping pad (Blank group), commercially available fresh-keeping pad (Control group), composite aerogel prepared in comparative example 1 (Group A), antibacterial aerogel prepared in comparative example 2 (Group B), and antibacterial aerogel prepared in Example 2 (Group C2) were selected.

[0180] Experimental process: Fresh strawberries were picked from the greenhouse. The picking criteria were uniformity of size (about 20g), maturity (about 75% red surface coloration) and absence of any visible defects. The picked fresh strawberries were packed in foam boxes with independent compartments and immediately transported to the laboratory within 2 hours. The fresh strawberries were first gently washed with 1% chlorine dioxide solution and distilled water and dried. Afterwards, the strawberries were randomly divided into 5 groups and placed in containers covered with the five different fresh-keeping mats mentioned above and stored at 20±1℃ and 50±3%RH for 5 days. Random samples were taken every day for the determination of various quality indicators; each group was repeated 3 times.

[0181] The various quality indicators were measured by weighing the strawberries, recording the color at three fixed positions of each sample using a spectrophotometer, and calculating the total color difference (ΔE*). The firmness of the strawberries was measured using a texture analyzer and a P / 2 probe, with the speeds before, during, and after the measurement being 1, 1, and 10 mm / s, respectively. The total viable count (TVC) of the strawberries was tested using a plate count method. The results are as follows: Figures 12-18 shown.

[0182] Figure 12 、 Figure 13 and Figure 14 The appearance changes, brightness and total color difference of strawberries during storage at room temperature can be intuitively displayed from the appearance images and color parameters. It can be seen that the strawberries in the untreated group (Blank) began to lose their luster and showed signs of decay on the second day of storage. On the third day, the strawberries of the commercially available fresh-keeping pad (Control) and Group A (composite aerogel prepared in Comparative Example 1) also began to show obvious mold spots. However, due to the excellent antibacterial properties of citral, the strawberries in Groups B and C2 were still plump and bright in color on the third day. However, after continuous storage for up to the fifth day, only the strawberries in Group C2 still maintained their intact structure and had no obvious quality deterioration, which was due to the sustained release effect of citral. In addition, as the storage period prolonged, the brightness values ​​(L*) of the strawberries in all groups tended to darken. Moreover, compared with Group C2, the total color difference values ​​(ΔE * ) is larger, which is related to fruit aging and the action of fungi that cause tissue darkening. The results show that the antibacterial aerogel mat can effectively delay metabolism and reduce strawberry rot.

[0183] Figure 15 and Figure 16 The figures represent the weight loss and firmness of strawberries during room temperature storage. Weight loss and softening of fresh fruit are normal phenomena during storage, primarily due to inherent transpiration and respiration, as well as microbial consumption. Initially, the weight loss of strawberries in the Blank group was slightly lower than that of the Control and Treatment groups due to water absorption by the commercially available and aerogel mats. This reversed after one day, with the Blank group experiencing a weight loss rate of 10.02 ± 0.66% after five days. Firmness is also a key consideration for consumers. Over time, the firmness of strawberries in all groups decreased. At the end of storage, strawberries in Group C2 showed less weight loss and softening than the other groups. This may be due to the sustained release of citral, which inhibited microbial growth and reduced microbial consumption of nutrients in the strawberries. Strawberries not severely infested by microorganisms retained relatively intact tissue, thereby reducing pathological water loss. Furthermore, citral's inhibitory effect on pectinase activity may have effectively maintained the firmness and weight of the strawberries.

[0184] Figure 17 and Figure 18The figures show the change in total viable bacterial count (TVC) during storage of strawberries at room temperature and a photograph of the plate. The total viable bacterial count (TVC) can visually demonstrate the antibacterial properties of the different treatments during storage. It can be seen that the TVC of strawberries in all groups increased over time. Strawberries in the untreated Blank group were susceptible to microbial growth, with a TVC of 10^(3.17±0.09) CFU / g on day 1, which increased by two orders of magnitude on day 5. Because citral effectively protects strawberries from external microbial attack while inhibiting the growth of internal microorganisms, groups B and C2 exhibited significant antibacterial effects. Although the TVC of group B was lower than that of group C2 at the beginning of storage, this relationship reversed after two days, which is related to the burst release and long-term sustained release of citral from both aerogels. Ultimately, after five days of storage at room temperature, the TVC of the strawberries was 10^(3.26±0.03) CFU / g, significantly lower than that of the other groups. These results demonstrate that the antibacterial aerogel mats formed by encapsulating citral in an emulsion and loading it onto a DNF / GE aerogel matrix exhibit the advantage of long-term freshness preservation.

[0185] The above are several relatively preferred implementation methods of the preparation method of the present invention, but they cannot be used as limitations on the technical solutions protected by the present invention. Any replacement solutions obtained by ordinary technicians in this field without making creative work based on the technical ideas of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing antibacterial aerogel based on buckwheat hull cellulose nanofiber emulsion, characterized in that: The following steps are involved: S1. Preparation of CNF colloidal solution The crushed buckwheat hulls are added to peracetic acid and adjusted to a pH of 4.8 to 5.0 for pretreatment, and then washed, dispersed and high-pressure homogenized to obtain a CNF colloidal solution; S2. Preparation of antibacterial emulsion The CNF colloidal solution and citral in step S1 are dispersed, mixed, and homogenized under high pressure to obtain an antibacterial emulsion; the mass proportion of CNF in the antibacterial emulsion is 0.25% to 0.35%; S3. Preparation of DNF colloidal solution The CNF colloidal solution in step S1 is mixed with sodium periodate; the pH value is adjusted to 4±0.2, the mixture is reacted in the dark, and then dialyzed to obtain a DNF colloidal solution; the mass ratio of CNF to sodium periodate is 1:(2.25-2.50); S4, antibacterial aerogel The DNF colloidal solution and gelatin are mixed in a volume ratio of 1:(1.5-4.5) and stirred to form a precursor solution; then the antibacterial emulsion of step S2 is added and continued to be stirred, wherein the volume of the antibacterial emulsion is 10%-30% of the total volume of the DNF colloidal solution, gelatin and antibacterial emulsion; then the solution is placed, pre-frozen and freeze-dried in sequence to obtain the antibacterial aerogel.

2. The method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1, characterized in that: In the step S1, the particle size of the crushed buckwheat hulls is 1 mm to 1.25 mm; and the mass ratio of buckwheat hulls to peracetic acid is 1:(0.35 to 0.40).

3. The method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1, characterized in that: In step S1, the pretreatment conditions are: temperature 80°C to 85°C, time 45min to 50min; dispersion is mechanical defibrillation at a speed of 15000r / min to 16000r / min for 15min to 18min; high-pressure homogenization is performed at a pressure of 300bar to 1000bar for a total of 10 mechanical cycles.

4. The method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1, characterized in that: In the step S2, the dispersion mixing is performed at a rotation speed of 15000 r / min to 16000 r / min for 2 to 3 minutes; and the high-pressure homogenization is performed at a pressure of 400 bar to 450 bar for 3 to 4 cycles of homogenization.

5. The method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1, characterized in that: In step S3, the reaction is carried out at a temperature of 50° C. to 55° C. in the dark for 12 to 13 hours; and then dialyzed for 24 to 26 hours to obtain a colloidal solution of DNF.

6. The method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1, characterized in that: In step S4, the stirring conditions are: temperature 60°C to 65°C, time 15min to 30min; the placing is first placing at a temperature of 60°C to 65°C for 30min to 35min, then placing at 3 and then 4 for 20min to 30min; the pre-freezing temperature is -80°C to -85°C, and the pre-freezing time is 2.5h to 3h; the freeze-drying time is 24h to 26h.

7. Antibacterial aerogel prepared by the method for preparing antibacterial aerogel based on buckwheat hull full cellulose nanofiber emulsion according to claim 1.

8. Use of the antibacterial aerogel according to claim 7 in improving the antibacterial performance against Staphylococcus aureus, Escherichia coli or Botrytis cinerea.

9. Use of the antibacterial aerogel according to claim 7 as a fresh-keeping pad in food packaging.

10. Use of the antibacterial aerogel according to claim 7 as a fresh-keeping pad in fruit preservation.

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