Bamboo shoot shell cellulose-based antibacterial aerogel as well as preparation method and application thereof

Abstract

The invention discloses bamboo shoot shell cellulose-based antibacterial aerogel as well as a preparation method and application thereof. The preparation method of the bamboo shoot shell cellulose-based antibacterial aerogel comprises the following steps: S1, preparing a chitosan solution; s2, the bamboo shoot shell cellulose wet powder and a chitosan solution are mixed and homogenized, and a first mixed solution is obtained; s3, pouring the first mixed solution into a mold, and freezing the mold in a refrigerator at-20 to-196 DEG C for 1-12 hours to obtain an aerogel precursor; and S4, soaking the aerogel precursor in a cinnamyl aldehyde ethanol solution for 12 hours, cleaning, and drying to obtain the bamboo shoot shell cellulose-based antibacterial aerogel. The cinnamyl aldehyde in the bamboo shoot shell cellulose-based antibacterial aerogel prepared by the preparation method disclosed by the invention can be continuously released for 168 hours, so that the purpose of long-acting bacteriostasis is achieved; when the aerogel is applied to preservation of chilled fresh meat, the shelf life of the chilled fresh meat can be prolonged to 12 days, and the aerogel has the characteristics of high biological safety and degradation after 12 weeks in a soil environment, and meets the requirements of greenness and environmental protection.

Description

Technical Field

[0001] The present invention relates to the fields of composite material synthesis and food technology, and more specifically, to bamboo shoot shell cellulose-based antibacterial aerogel and a preparation method and application thereof. Background Art

[0002] Biomass-based functional packaging materials have become a research hotspot, with aerogels showing significant potential due to their high porosity, strong liquid absorption capacity, and tunable structure. However, existing aerogel preparation often relies on high-pressure freeze-drying or chemical cross-linking agents, which poses challenges such as complex processes, high costs, and the introduction of toxic residues. Furthermore, while natural antimicrobial agents possess broad-spectrum antibacterial properties, their volatility results in a short duration of action, making it difficult to achieve long-term sustained release in aerogel materials.

[0003] While existing chitosan and cellulose composite systems offer some antibacterial and biodegradability, they lack mechanical properties and rely on chemical crosslinkers (such as glutaraldehyde), which can pose a risk of biotoxicity. The Schiff base reaction offers a new approach for constructing reversibly crosslinked networks, but its integration with porous structure design and controlled release of active ingredients in aerogel preparation remains to be explored. Therefore, developing a bio-based aerogel material that is green, can be prepared at ambient pressure, and exhibits both high antibacterial efficacy and controlled release properties has become a key challenge in the field of intelligent food packaging. Summary of the Invention

[0004] The purpose of the present invention is to provide a bamboo shoot shell cellulose-based antibacterial aerogel and a preparation method and application thereof.

[0005] According to one aspect of the present invention, a method for preparing bamboo shoot shell cellulose-based antibacterial aerogel is provided, which is characterized by comprising the following steps: S1. The chitosan powder was dissolved in an aqueous citric acid solution to prepare a chitosan solution; S2. Take a certain amount of bamboo shoot shell cellulose wet powder and chitosan solution mixed, using a high-speed shearing machine homogenized until the mixture is uniform to obtain a first mixed solution; S3. Pour the first mixed solution into a plastic mold, seal it with plastic wrap, and freeze it in a -20~-196℃ refrigerator for 1-12 h to obtain an aerogel precursor; S4. The aerogel precursor was immersed in an ethanol solution containing aldehyde compounds for 12 h. After the immersion, the aldehyde compounds remaining on the surface were cleaned with anhydrous ethanol, and then dried at 60 °C for 2 h to obtain the bamboo shoot shell cellulose-based antibacterial aerogel.

[0006] In some embodiments, the concentration of the citric acid aqueous solution is 2-4.5 wt %, and the concentration of the chitosan solution is 2-4.5 wt %.

[0007] In some embodiments, the solid content of bamboo shoot shell cellulose in the bamboo shoot shell cellulose wet powder is 8%, the addition amount of bamboo shoot shell cellulose wet powder is 2.5-10 g, and the mass ratio of bamboo shoot shell cellulose wet powder to chitosan solution is 1:2-2:1.

[0008] In some embodiments, the aldehyde compound in the ethanol solution containing the aldehyde compound is selected from any one of cinnamaldehyde, citral, anisaldehyde, vanillin, and salicylaldehyde, and the concentration of the ethanol solution containing the aldehyde compound is 1-4 wt%.

[0009] In some embodiments, the concentration of the citric acid aqueous solution is 4 wt %, and the concentration of the chitosan solution is 4 wt %.

[0010] In some embodiments, the added amount of the wet bamboo shoot shell cellulose powder is 5 g, and the mass ratio of the wet bamboo shoot shell cellulose powder to the chitosan solution is 1:1.

[0011] In some embodiments, the ethanol solution containing an aldehyde compound is a cinnamaldehyde ethanol solution, and the concentration of the cinnamaldehyde ethanol solution is 3 wt %.

[0012] In some embodiments, the freezing temperature of the refrigerator in step S3 is -80°C and the freezing time is 2 hours.

[0013] According to another aspect of the present invention, a bamboo shoot shell cellulose-based antibacterial aerogel is provided, which is prepared using the above-mentioned preparation method.

[0014] According to another aspect of the present invention, there is provided an application of bamboo shoot shell cellulose-based antibacterial aerogel in preserving cold fresh meat.

[0015] The beneficial effects of the present invention are as follows: (1) The bamboo shoot shell cellulose-based antibacterial aerogel prepared by the present invention forms a three-dimensional through-pore structure with a porosity of 82.95 ± 0.14%, a water absorption rate of 866.25 ± 11.19%, and a compressive strength of 521.95 kPa. FTIR analysis shows that Cin and CS in the aerogel form an imine bond (C=N, 1634 cm⁻¹); (2) The present invention is based on the ice template-solvent replacement method with BSC and CS as the base material. Through multiple cross-linking mechanisms (such as electrostatic attraction and hydrogen bonding), an ice-crystalline bamboo shoot shell cellulose-based aerogel precursor is successfully constructed. Without vacuum freeze-drying, the ice-crystalline aerogel precursor is directly loaded with aldehyde compounds through the CS@Cin dynamic Schiff base reaction, and then dried at normal pressure to obtain the bamboo shoot shell cellulose-based antibacterial aerogel. During the preparation process, no high pressure is required in a vacuum environment, and the preparation time is shortened to 17 h, thereby improving the preparation efficiency of the aerogel and greatly reducing the production cost of the bio-based antibacterial aerogel. (3) The release time of cinnamaldehyde in the bamboo shoot shell cellulose-based antibacterial aerogel prepared by the present invention can last up to 168 hours, achieving the purpose of long-term antibacterial effect; when the aerogel is specifically used to preserve fresh cold meat, the shelf life of the fresh cold meat can be extended to 12 days. It also has the characteristics of high biosafety and degradation in the soil environment after 12 weeks, meeting the requirements of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The cross-sectional SEM images of the BSC5 / CS@Cin aerogels with different CS contents in Examples 1 and 2 of the present invention are shown in Figure 1, where a is BSC5 / CS2@Cin3 and b is BSC5 / CS 2.5 @Cin3, c is BSC5 / CS3@Cin3, d is BSC5 / CS 3.5 @Cin3, e is BSC5 / CS4@Cin3, f is BSC5 / CS 4.5 @Cin3.

[0017] Figure 2 FTIR spectra of Cin, BSC, CS and BSC5 / CS4@Cin3 aerogels of Example 1 of the present invention.

[0018] Figure 3 This is a graph showing the density and porosity results of BSC5 / CS@Cin aerogels with different CS contents in Example 2 of the present invention.

[0019] Figure 4 This is a stress-strain curve of BSC5 / CS@Cin aerogels with different CS contents in Example 2 of the present invention.

[0020] Figure 5 This is a comparison chart of the swelling ratio and solubility of BSC5 / CS@Cin aerogels with different CS contents in Example 2 of the present invention.

[0021] Figure 6 The cross-sectional SEM images of the BSC / CS4@Cin aerogels with different BSC contents in Example 3 of the present invention are shown in FIG. 1 , where a represents BSC content. 2.5 / CS4@Cin, b is BSC5 / CS4@Cin, c is BSC 7.5 / CS4@Cin, d is BSC 10 / CS4@Cin.

[0022] Figure 7 This is a graph showing the density and porosity results of BSC / CS4@Cin aerogels with different BSC contents in Example 3 of the present invention.

[0023] Figure 8This is a stress-strain curve of BSC / CS4@Cin aerogels with different BSC contents in Example 3 of the present invention.

[0024] Figure 9 This is a comparison chart of the swelling ratio and solubility of BSC / CS4@Cin aerogels with different BSC contents in Example 3 of the present invention.

[0025] Figure 10 This is a graph showing the release kinetics of cinnamaldehyde from bamboo shoot shell cellulose-based antibacterial aerogels with different cinnamaldehyde loading amounts according to Example 4 of the present invention.

[0026] Figure 11 This is a diagram of the long-term antibacterial performance of the BSC5 / CS4@Cin3 aerogel in direct contact mode according to Example 4 of the present invention, where a is the inhibition zone diagram and b is the inhibition zone diameter diagram.

[0027] Figure 12 This is a diagram of the long-term antibacterial performance of the BSC5 / CS4@Cin4 aerogel in direct contact mode according to Example 4 of the present invention, where a is the inhibition zone diagram and b is the inhibition zone diameter diagram.

[0028] Figure 13 This is a diagram of the long-term antibacterial performance of the BSC5 / CS4@Cin3 aerogel in Example 4 of the present invention in the headspace mode, where a is the inhibition zone diagram and b is the inhibition zone diameter diagram.

[0029] Figure 14 This is a diagram of the long-term antibacterial performance of the BSC5 / CS4@Cin4 aerogel in Example 4 of the present invention in the headspace mode, where a is the inhibition zone diagram and b is the inhibition zone diameter diagram.

[0030] Figure 15 This is the fingerprint spectrum of the electronic nose sensor response value in the bamboo shoot shell cellulose-based antibacterial aerogel with different cinnamaldehyde loading amounts according to Example 4 of the present invention, wherein a is the electronic nose sensor response value and b is the fingerprint spectrum.

[0031] Figure 16 This is a stress-strain curve of BSC5 / CS4@Cin3 aerogel at different freezing temperatures in Example 5 of the present invention.

[0032] Figure 17 This is a comparison chart of the swelling rate and solubility of BSC5 / CS4@Cin3 aerogel at different freezing temperatures in Example 5 of the present invention.

[0033] Figure 18 This is a stress-strain curve of BSC5 / CS4@Cin3 aerogel at different freezing times in Example 6 of the present invention.

[0034] Figure 19This is a comparison chart of the swelling rate and solubility of BSC5 / CS4@Cin3 aerogel at different freezing times in Example 6 of the present invention.

[0035] Figure 20 This is a graph showing the degradation of BSC5 / CS4@Cin3 aerogel in soil at different times in Example 7 of the present invention.

[0036] Figure 21 This is a graph showing the cell viability of the BSC5 / CS4@Cin3 aerogel in Example 8 of the present invention.

[0037] Figure 22 This is a curve diagram of the change of volatile basic nitrogen content in the fresh meat during storage under different preservation methods according to Example 9 of the present invention.

[0038] Figure 23 This is a curve diagram of the change in the total bacterial count of fresh meat during storage using different preservation methods according to Example 9 of the present invention.

[0039] Figure 24 Graphs showing changes in the appearance of fresh meat during storage using different preservation methods according to Example 9 of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail through specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention by those skilled in the art are all within the scope of the appended claims. Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents available on the conventional market.

[0041] Example 1 Preparation and performance analysis of bamboo shoot shell cellulose-based antibacterial aerogel 1.1 The preparation method of bamboo shoot shell cellulose-based antibacterial aerogel comprises the following steps: S1. The chitosan powder was dissolved in a 4 wt% aqueous solution of citric acid to prepare a 4 wt% chitosan solution; S2. Take 5 g of bamboo shoot shell cellulose wet powder and 5 g of 4 wt% chitosan solution and mix them using a high-speed shearing machine until the mixture is uniform to obtain a first mixed solution; S3. The first mixed solution was poured into a plastic mold, sealed with plastic wrap, and placed in a -80 ° C refrigerator for 2 h to obtain an aerogel precursor; S4. The aerogel precursor was soaked in a 3 wt% cinnamaldehyde ethanol solution for 12 h. After soaking, the residual cinnamaldehyde on the surface was cleaned with anhydrous ethanol, and then dried at 60°C for 2 h to obtain BSC5 / CS4@Cin3 aerogel, i.e., bamboo shoot shell cellulose-based antibacterial aerogel.

[0042] 1.2 Surface morphology analysis, density and porosity determination of bamboo shoot shell cellulose-based antibacterial aerogel (BSC5 / CS4@Cin3) Cut the cross section of the BSC5 / CS4@Cin3 aerogel prepared in 1.1 and fix it on the conductive glue of the sample stage. Vacuum gold spraying was performed on the BSC5 / CS4@Cin3 aerogel and the cross-sectional structure of the BSC5 / CS4@Cin3 aerogel was observed using a scanning electron microscope. Figure 1 e.

[0043] The porosity of BSC5 / CS4@Cin3 aerogels was determined using the liquid displacement method. BSC5 / CS4@Cin3 aerogel samples were dried in an oven and then soaked in anhydrous ethanol for 24 hours. The saturated samples were then removed and weighed. The porosity of the aerogels was calculated using the formula:

[0044] , Where W1 and W2 are the mass of aerogel before and after immersion, respectively; ρ is the density of anhydrous ethanol, 0.7893 g / cm³; V is the volume of aerogel sample, cm 3 .

[0045] Depend on Figure 1 As can be seen from the results, the BSC5 / CS4@Cin3 aerogel prepared by the ice template-solvent replacement method exhibits a three-dimensional disordered porous structure. The pore formation mechanism stems from the competitive effect between ice crystal growth and polymer network construction during the freezing process. Ice crystal growth squeezes the cellulose (BSC) and chitosan (CS) molecular chains to aggregate, forming an interpenetrating network skeleton after drying. The CS molecules on the pore wall form a wrinkled coating on the surface of the BSC fibers, and the pore wall exhibits a honeycomb structure with a porosity of 82.95%. The aerogel density was measured to be 0.115 g / cm 3 , CS molecular chains penetrate into the gaps between BSC fibers, enhancing the density of the skeleton; CS and Cin form a stable covalent network through Schiff base reaction (C=N bond), and the hydrophilicity of CS makes it enriched at the ice crystal interface, effectively inhibiting the longitudinal growth of ice crystals and optimizing the pore uniformity.

[0046] 1.3 FTIR spectroscopic determination of bamboo shoot shell cellulose-based antibacterial aerogel (BSC5 / CS4@Cin3) The chemical structure and interaction between components of the BSC5 / CS4@Cin3 aerogel prepared in 1.1 of this example were characterized by FTIR spectroscopy. Figure 2 shown.

[0047] Depend on Figure 2It can be seen that in the BSC5 / CS4@Cin3 aerogel, the -OH stretching vibration peak of BSC shifts from 3375 cm -1 to 3450 cm -1 , indicating that hydrogen bonds (O-H···N-H or O-H···O) are formed between BSC and CS. The C=O stretching vibration peak (1680 cm -1 ) of Cin disappears in the aerogel, while the intensity of the amide II band (N-H bending vibration, 1600 cm -1 ) of CS decreases, and a new C=N stretching vibration peak appears at 1634 cm -1 , indicating that the amino group (-NH2) of CS and the aldehyde group (-CHO) of Cin undergo condensation reaction to form an imine bond (-N=C-), i.e., Schiff base crosslinking. In addition, the characteristic peaks of 1161 cm -1 (C-O-C antisymmetric stretching), 1040 cm -1 and 896 cm -1 (β-1,4-glycosidic bond) are clearly visible in the aerogel, confirming that the cellulose skeleton of BSC remains intact during crosslinking. FTIR analysis shows that BSC5 / CS4@Cin3 aerogel realizes the retention of cellulose skeleton, stable combination between components and functional adjustability through the synergistic effect of hydrogen bonding and Schiff base crosslinking, providing a structural optimization basis for bamboo shoot shell cellulose-based antibacterial aerogel.

[0048] Example 2 Effect of Different Chitosan Addition Amounts on the Properties of Bamboo Shoot Shell Cellulose-Based Antibacterial Aerogel 2.1 Effect of Different Chitosan Addition Amounts on the Surface Morphology of Bamboo Shoot Shell Cellulose-Based Antibacterial Aerogel Referring to the preparation method of 1.1 in Example 1, BSC5 / CS@Cin3 aerogels with different CS contents were prepared by adding 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, and 4.5wt% of chitosan (CS), and the surface morphology, density, and porosity of the above-mentioned BSC5 / CS@Cin3 aerogels with different CS contents were determined by referring to the method of 1.2 in Example 1. The specific results are shown in Figure 1 , Figure 3 .

[0049] As shown in Figure 1 and Figure 3 , when the CS addition amount is 2wt%, the SEM shows that the aerogel has an open porous skeleton with a porosity of 99.73% and a density of 0.063 g / cm³. The CS molecules are protonated by amino groups (-NH3 +) forms an electrostatic complex with the BSC hydroxyl group (-OH), which initially inhibits the coarsening of ice crystals, but the crosslinking density is low. When the CS addition amount increases from 2.5 wt% to 4 wt%, the CS molecules form a wrinkled wrapping layer on the surface of the BSC fiber, and the pore wall presents a honeycomb structure. The porosity decreases from 97.82% to 82.95%, and the density decreases from 0.088 g / cm 3 Increased to 0.115 g / cm 3 CS molecular chains penetrate into the gaps between BSC fibers, enhancing the density of the skeleton. CS and Cin form a stable covalent network through a Schiff base reaction (C=N bond). The hydrophilicity of CS causes it to accumulate at the ice crystal interface, effectively inhibiting the longitudinal growth of ice crystals and optimizing pore uniformity. When the CS addition amount is 4.5 wt%, the high CS addition leads to excessive cross-linking of the structure. SEM observations show a closed-cell structure and local collapse, and the density increases to 0.164 g / cm 3 , the porosity dropped to 77.25%. Therefore, the present invention uses 4wt% chitosan solution as the optimal chitosan addition amount, and adjusts the CS content to control the synergistic effect of physical entanglement and chemical cross-linking, achieving precise optimization of the aerogel pore structure and mechanical properties.

[0050] 2.2 Effects of different chitosan addition amounts on the mechanical properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method described in step 1.1 of Example 1, BSC5 / CS@Cin aerogels with different CS contents were prepared with chitosan (CS) addition amounts of 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, and 4.5 wt%. The compression performance of the BSC5 / CS@Cin aerogels was tested using an electronic universal testing machine. The test samples were cylindrical aerogels with a diameter of 25 to 27 mm and a height of 12 to 15 mm. The test conditions were room temperature, a compression rate of 2 mm / min, and a maximum compressive strain of 80%. See the specific results for details. Figure 4 .

[0051] Depend on Figure 4 When the CS addition level is 4 wt%, the aerogel's stress reaches 521.95 kPa, a sixfold increase compared to the 84.54 kPa stress at 2 wt% CS. The strengthening mechanism is as follows: CS amino groups form reversible hydrogen bonds with BSC hydroxyl groups, dissipating mechanical energy; CS@Cin Schiff base reactions (C=N bonds) create a stable covalent network; and the honeycomb pore wall structure reduces stress inhomogeneity. The synergistic effect of these three factors significantly improves the mechanical properties of the BSC5 / CS4@Cin aerogel.

[0052] The BSC5 / CS4@Cin aerogel of this invention exhibits significant advantages: a high compressive strength of 521.95 kPa, a more streamlined component system, and a synergistic combination of high porosity and mechanical strength, meeting the dual requirements of food lining materials for cushioning and breathability. By adjusting the ratio of BSC (5 g) and CS (4 wt%), this invention achieves a cellulose-based antimicrobial aerogel from bamboo shoot shells that combines high porosity (82.95%) with excellent mechanical strength (compressive strength of 521.95 kPa), providing a solution for its application in food preservation packaging, cushioning, and other fields.

[0053] 2.3 Effect of different chitosan addition amounts on the swelling properties of bamboo shoot shell cellulose-based antibacterial aerogels The BSC5 / CS@Cin aerogels with different CS contents prepared in 2.1 were immersed in 100 mL of distilled water for 24 h. After removal, the surface moisture was wiped off with filter paper and weighed. Then, the samples were dried to constant weight. The swelling ratio (S1) and solubility (S2) of the aerogels were calculated according to the following formulas. The specific results are shown in Figure 5 .

[0054] , , Wherein, m1 is the mass of the aerogel sample before absorbing water, g; m2 is the weight of the sample after absorbing moisture, g; and m3 is the weight of the sample after drying to a constant weight after absorbing moisture, g.

[0055] Depend on Figure 5 It can be seen that when the BSC content in the BSC5 / CS@Cin aerogel is fixed at 5 g and the CS addition is 4 wt%, the solubility is the lowest, at 1.16%. When the CS addition is less than 4 wt%, the CS and Cin form dynamic covalent crosslinks through a Schiff base reaction, resulting in synergistic physical entanglement that enhances network stability and inhibits swelling. At 4.5 wt%, excessive crosslinking triggers a steric effect, weakening intermolecular forces, leading to localized loosening of the network and promoting swelling. Therefore, in this example, the optimal CS addition is determined to be 4 wt%. The resulting aerogel has a solubility of 1.16% and a water absorption rate of 866.25%. This achieves a synergistic balance between aerogel swelling rate and solubility, meeting the multiple requirements of food packaging for juice absorption, microbial growth inhibition, structural integrity, and long-term stability.

[0056] Example 3 Effects of different amounts of bamboo shoot shell cellulose wet powder added on the properties of bamboo shoot shell cellulose-based antibacterial aerogel 3.1 Effects of different bamboo shoot shell cellulose wet powder addition amounts on the surface morphology of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method in 1.1 of Example 1, the addition amount of bamboo shoot shell cellulose wet powder (BSC) was 2.5g, 5g, 7.5g, and 10g to prepare BSC / CS4@Cin aerogels with different BSC contents. The surface morphology, density, and porosity of the BSC / CS4@Cin aerogels with different BSC contents were measured according to the method in 1.2 of Example 1. The specific results are shown in Figure 6 、 Figure 7 .

[0057] Depend on Figure 6 and Figure 7 It can be seen that when the amount of BSC added is 5 g, the density of BSC5 / CS4@Cin aerogel is 0.115 g / cm 3 The porosity is 82.95%. The SEM image shows that the aerogel has an open porous structure with uniform pore distribution and interconnected pores. Combined with the compression performance and water absorption and swelling performance data, the aerogel with high compressive strength, high water absorption capacity and low solubility is selected. BSC5 / CS4@Cin aerogel has great advantages in performance. The SEM graph also observes that it has a relatively uniform pore structure. Therefore, 5g of bamboo shoot shell cellulose wet powder (BSC) is added as the optimal addition amount.

[0058] 3.2 Effects of different bamboo shoot shell cellulose wet powder addition amounts on the mechanical properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the test method in 2.2, the compression performance test of the BSC / CS4@Cin aerogels with different BSC contents prepared in Example 3.1 was carried out using an electronic universal testing machine. Figure 8 .

[0059] Depend on Figure 8 As shown, when the BSC addition amount increased from 2.5 g to 10 g, the aerogel stress increased from 383.09 kPa to 666.06 kPa, an increase of approximately 73.87%. The fiber packing density increased, the porosity decreased, and the load-bearing capacity of the skeleton was enhanced. However, when the BSC addition amount was 10 g, the aerogel had a high solubility in water. Scanning electron microscopy revealed that excessive cellulose content resulted in a dense internal structure of the aerogel, which was not conducive to the loading and release of the antimicrobial agent. Therefore, to balance the various performance advantages, the optimal addition amount of bamboo shoot shell cellulose (BSC) was selected as 5 g.

[0060] 3.3 Effects of different bamboo shoot shell cellulose wet powder addition amounts on the swelling properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the swelling performance test method in 2.3, the swelling rate and solubility of the BSC / CS4@Cin aerogels with different BSC contents prepared in 3.1 of this Example were tested. Figure 9 .

[0061] Depend on Figure 9 It can be seen that when the BSC content is 5 g, the water absorption rate of BSC5 / CS4@Cin aerogel is 844.63%, which is lower than that of BSC. 2.5 / CS4@Cin aerogel and BSC 10 / CS4@Cin aerogel, and BSC 7.5 The water absorption values ​​of the BSC / CS4@Cin aerogels are similar. This is attributed to the enhanced hydrogen bond crosslinking density between BSC molecular chains (the porosity decreased from 79.87% to 73.96%), and the dense network structure effectively inhibited water penetration.

[0062] The water solubility of aerogel is closely related to the network integrity. When the BSC content is 5 g, the solubility of BSC5 / CS4@Cin aerogel is 1.24%, which is significantly lower than that of aerogels with other BCS contents. This is due to the physical cross-linking network dominated by hydrogen bonds that enhances the stability of the material. When the BSC content is 10 g, the solubility of BSC5 / CS4@Cin aerogel is 1.24%, which is significantly lower than that of aerogels with other BCS contents. 10 The solubility of / CS4@Cin aerogel is 4.74%. Excessive BSC causes local network collapse and accelerates water penetration.

[0063] The solubility of the BSC5 / CS4@Cin aerogel prepared in this example was significantly reduced, demonstrating its superior water stability as a food liner material. Bioactive aerogels with high water absorption properties have important applications in food packaging. They can extend the shelf life of food by absorbing exudate from packaging, regulating humidity, and inhibiting microbial growth.

[0064] Example 4 Effects of different cinnamaldehyde addition amounts on the properties of bamboo shoot shell cellulose-based antibacterial aerogels 4.1 Effect of different cinnamaldehyde addition amounts on the release properties of cinnamaldehyde from bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method of 1.1 in Example 1, BSC5 / CS4@Cin aerogels with different cinnamaldehyde addition amounts (i.e., BSC5 / CS4@Cin1, BSC5 / CS4@Cin2, BSC5 / CS4@Cin3, and BSC5 / CS4@Cin4) were prepared as samples using cinnamaldehyde ethanol solution concentrations of 1 wt%, 2 wt%, 3 wt%, and 4 wt%. 95% ethanol solution (v / v) was selected as the release solvent, representing a food simulant of fatty food. The BSC5 / CS4@Cin aerogel samples (3 cm×3 cm) with different cinnamaldehyde addition amounts were immersed in 100 mL of release solvent and placed on a shaker at 50 rpm in a dark environment at 4°C. 1 mL of release liquid was taken from the release solvent every 30 minutes and 1 mL of release solvent was added to keep the volume constant. After the release liquid was appropriately diluted with anhydrous ethanol, the absorbance at the maximum absorption peak was measured using Nanodrop, and the Cin concentration was calculated. Substituting it into the following formula, the Cin release curves in BSC5 / CS4@Cin aerogels with different cinnamaldehyde addition amounts can be obtained. See for details. Figure 10 .

[0065] The cumulative release rate formula of Cin is: , Among them, C t is the amount of Cin released at time t, and M represents the amount of Cin released when it reaches equilibrium.

[0066] Depend on Figure 10 The release behavior of the aerogels exhibited a distinct two-stage pattern: a high release rate in the initial stage (0–24 h), with cumulative release rates reaching 38.02%, 45.80%, 54.92%, and 62.50% for BSC5 / CS4@Cin1, BSC5 / CS4@Cin4, and BSC5 / CS4@Cin4, respectively. The release rate slowed and stabilized in the subsequent stage (24–168 h). With increasing Cin loading in the aerogels, the release rate and release amount showed a positive correlation, suggesting that the release process may be driven by the cinnamaldehyde concentration gradient. The cumulative release rates of cinnamaldehyde from the aerogels were high at 3 wt% and 4 wt% ethanolic cinnamaldehyde solutions. Therefore, in the subsequent examples, 3 wt% and 4 wt% ethanolic cinnamaldehyde solutions were used for further analysis.

[0067] 4.2 Effect of different cinnamaldehyde addition amounts on the long-term antibacterial effect of bamboo shoot shell cellulose-based antibacterial aerogel The BSC5 / CS4@Cin3 and BSC5 / CS4@Cin4 aerogels prepared in Example 4.1 were cut into discs with a diameter of approximately 10.0 ± 0.2 mm and a thickness of 2.0 ± 0.2 mm. These discs were sterilized under UV for 30 minutes and used as samples. These samples were tested for their long-term antibacterial properties against Staphylococcus aureus and Escherichia coli using both direct contact and headspace diffusion methods.

[0068] Direct contact mode: 100 μL bacterial suspension (concentration 1×10 8 CFU / mL) was evenly spread on the surface of the solid culture medium and allowed to stand for 10 minutes. The aerogel sample disc was gently pressed onto the agar surface and stored at 25°C and 60% relative humidity for 0, 7, 14, and 21 days. The diameter of the inhibition zone was measured. Headspace diffusion mode: The bacterial suspension coating operation is the same as the direct contact mode. The aerogel sample disc is fixed to the center of the inner side of the culture dish lid (avoiding contact with the agar surface). After inverting the culture dish, store at 25°C and 60% relative humidity for 0, 7, 14, and 21 days. The diameter of the inhibition zone is then measured.

[0069] The effects of drug loading concentration and storage time on antibacterial performance were analyzed based on the test results. Figure 11-14 .

[0070] Depend on Figure 11-14 It can be seen that, regardless of the headspace mode or direct contact mode, the effective antibacterial effect of BSC5 / CS4@Cin3 aerogel and BSC5 / CS4@Cin3 aerogel on Staphylococcus aureus and Escherichia coli lasted for 21 days. S. aureus The diameter of the inhibition zone was 22.03±0.31 mm, which was significantly higher than that of the BSC5 / CS4@Cin4 aerogel group (18.53±0.35 mm).

[0071] 4.3 Optimization analysis of cinnamaldehyde addition based on electronic nose fingerprint The BSC5 / CS4@Cin aerogels with different cinnamaldehyde addition amounts prepared in Example 4.1 were used as samples, and electronic nose fingerprint detection was performed on them to measure the response peak intensity of the samples. The specific results are shown in Figure 15 .

[0072] like Figure 15As shown in Figure 1, the electronic nose fingerprints of BSC5 / CS4@Cin aerogels with different Cin additions exhibit characteristic differences, and their response peak intensities are closely correlated with Cin release behavior. Combined with the sensor specificity analysis in Table 1, sensors S2 (alkanes), S6 (aromatic compounds), and S8 (alcohols / aldehydes and ketones) contribute most significantly to the identification of volatile components from BSC5 / CS4@Cin aerogels. When the concentration of cinnamaldehyde in ethanol solution increases from 3 wt% to 4 wt%, the response intensity (ΔR / R0) of the S8 sensor increases from 6.99 to 9.09 (a 30.1% increase), indicating a significant increase in the release of volatile aldehydes and ketones in the high-concentration system.

[0073] Table 1 The types of compounds represented by different sensor numbers

[0074] The uncontrollable release behavior was verified in the long-term antibacterial performance test: although BSC5 / CS4@Cin4 S. aureus The inhibition zone diameter of BSC5 / CS4@Cin4 was 48.72±2.93 mm, which was not significantly different from the 49.00±1.41 mm of BSC5 / CS4@Cin3. However, within a 21-day storage period, the antibacterial performance of BSC5 / CS4@Cin4 decreased by 62.2%, significantly higher than the 54.8% of BSC5 / CS4@Cin3. Further analysis showed that the early excessive release of volatile active ingredients in the high-concentration group significantly weakened the material's long-term antibacterial ability. Therefore, based on a comprehensive evaluation of long-term antibacterial performance, the optimal concentration of cinnamaldehyde ethanol solution for preparing bamboo shoot shell cellulose-based antibacterial aerogels was determined to be 3 wt%, and subsequent experiments were conducted using BSC5 / CS4@Cin3 aerogels.

[0075] Example 5 Effects of different freezing temperatures on the properties of bamboo shoot shell cellulose-based antibacterial aerogels 5.1 Effects of different freezing temperatures on the mechanical properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method of 1.1 in Example 1, BSC5 / CS4@Cin3 aerogels with different freezing temperatures were prepared at -20°C, -80°C, and -196°C as samples, and the stress changes of the above samples were measured according to the method of 2.2 in Example 2. The specific results are shown in Figure 16 .

[0076] Depend on Figure 16As can be seen, the mechanical properties of the aerogels increase with decreasing freezing temperature. The stresses of BSC5 / CS4@Cin3 aerogels at 80% strain were 311 kPa, 521 kPa, and 451 kPa, respectively, at -20°C, -80°C, and liquid nitrogen freezing. This is because the aerogel network becomes denser as the freezing temperature decreases, resulting in higher compressive stress under the same strain conditions. While the small-pore structures formed by liquid nitrogen freezing exhibit excellent mechanical properties, if the material's backbone is insufficiently cross-linked or brittle, it may not be able to withstand the shrinkage stress, resulting in rupture, especially in the central region. Therefore, choosing -80°C as the freezing temperature for aerogel preparation is beneficial for improving the mechanical properties of the aerogels.

[0077] 5.2 Effects of different freezing temperatures on the swelling properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method of 1.1 in Example 1, BSC5 / CS4@Cin3 aerogels with different freezing temperatures were prepared at -20°C, -80°C, and -196°C as samples. The water absorption and solubility of the above samples were measured according to the method of 2.3 in Example 2. The specific results are shown in Figure 17 .

[0078] Depend on Figure 17 As can be seen, water absorption generally shows a significant downward trend with decreasing pre-freezing temperature. This may be because water freezes faster at lower freezing temperatures, resulting in a denser network structure after freeze-drying of the CNC aerogel, making it difficult for water to enter the aerogel interior, leading to reduced water absorption. Water solubility generally shows a significant upward trend with decreasing freezing temperature. At -196°C, the water solubility of the aerogel approaches 6.5%. This may be because the aerogel's toughness is reduced after freezing at lower temperatures, making it more susceptible to flocculent deposition in water. Based on the water absorption and solubility of BSC5 / CS4@Cin3 aerogel at different freezing temperatures, -80°C was selected as the optimal freezing temperature.

[0079] Example 6 Effects of different freezing times on the properties of bamboo shoot shell cellulose-based antibacterial aerogels 6.1 Effects of different freezing times on the mechanical properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method of 1.1 in Example 1, BSC5 / CS4@Cin3 aerogels with different freezing times were prepared at -80°C for 1 h, 2 h, 3 h, 6 h, and 12 h as samples. The stress changes of the above samples were measured according to the method of 2.2 in Example 2. The specific results are shown in Figure 18 .

[0080] Depend on Figure 18It can be seen that the purpose of pre-freezing is to completely crystallize the solvent at low temperatures, forming a uniform ice crystal template. Freezing time directly affects the nucleation and growth of ice crystals. Peak performance occurs between 2 and 3 hours, when ice crystals are smallest and evenly distributed, with continuous and dense pore walls and the highest compressive strength. If the solvent is not completely frozen (e.g., the freezing time is too short), the unfrozen liquid phase will cause pore structure collapse due to surface tension during drying, reducing mechanical strength. Excessive freezing time, on the other hand, provides no additional benefits and instead increases energy consumption. Furthermore, with prolonged freezing, small ice crystals gradually dissolve due to their higher surface energy, while larger ice crystals continue to grow through mass migration (similar to the sintering process), ultimately forming coarse pores that may weaken the skeleton continuity. Therefore, 2 hours is considered the optimal freezing time.

[0081] 6.2 Effects of different freezing times on the swelling properties of bamboo shoot shell cellulose-based antibacterial aerogels Referring to the preparation method of 1.1 in Example 1, BSC5 / CS4@Cin3 aerogels with different freezing times were prepared at -80°C for 1 h, 2 h, 3 h, 6 h, and 12 h as samples. The water absorption and solubility of the above samples were measured according to the method of 2.3 in Example 2. The specific results are shown in Figure 19 .

[0082] Depend on Figure 19 It can be seen that the effect of pre-freezing time on water absorption and swelling rate shows an initial increase followed by a decrease, with 2–3 hours generally being the optimal range. A freezing time that is too short results in insufficient porosity and water absorption capacity; a freezing time that is too long tends to form large pores, weakening capillary forces, leading to reduced water absorption and localized collapse of the swelling rate due to structural inhomogeneity, resulting in poor swelling stability. Therefore, a freezing time of 2 hours is optimal, maximizing porosity and capillary forces, achieving high water absorption and low solubility.

[0083] Example 7 Analysis of the Degradability of Bamboo Shoot Shell Cellulose-Based Antibacterial Aerogel Using the BSC5 / CS4@Cin3 aerogel prepared in 1.1 of Example 1 as a sample, 200 g of soil was taken, followed by 1.00 g of the above sample, cut into small pieces, and evenly buried in the soil at the same depth. During the experiment, the soil moisture was maintained at (60 ± 5)%, and the samples were placed in an environment with sufficient light and oxygen. Samples were removed every 7 days, and their volume and shape changes were visually inspected and photographed. Figure 20 .

[0084] Depend on Figure 20It can be seen that the BSC5 / CS4@Cin3 aerogel realizes high-efficiency biodegradation characteristics through the synergy of natural components (biomass skeleton material BSC and CS) and the design of porous structure. The degradation mechanism and environmental friendliness analysis is as follows: BSC and CS molecules contain hydrophilic amino and carboxyl groups, which provide specific sites for microbial adsorption; the high porosity and three-dimensional through channels of the aerogel significantly increase the contact area with water / microorganisms, promoting the directional hydrolysis of CS by extracellular enzymes β -1,4-glycosidic bonds and cellulose chains, and is completely degraded within 12 weeks, meeting the requirements of degradable packaging materials, and the degradation end products are CO2, H2O and oligosaccharides, which can be metabolized by soil microorganisms, avoiding white pollution.

[0085] Example 8 Cell compatibility analysis of bamboo shoot shell cellulose-based antibacterial aerogel To evaluate the biological safety of the BSC5 / CS4@Cin3 aerogel, cell compatibility determination was performed by Cell Counting Kit-8 (CCK-8) method. The BSC5 / CS4@Cin3 aerogel prepared in 1.1 of Example 1 was used as the sample, and HepG2 cells were inoculated in DMEM medium containing 10% fetal bovine serum (FBS) and 1% penicillin-streptomycin in a 37°C, 5% CO2 incubator until the cells were in good condition. The BSC5 / CS4@Cin3 aerogel was washed with sterile PBS buffer for 3 times to remove surface residues. Then, the BSC5 / CS4@Cin3 aerogel was soaked in the culture medium at 4°C for 24 h, and the soaking liquid was filtered through a 0.22 μm filter membrane to obtain the sample extract stock solution. A certain volume of sample extract stock solution was gradiently diluted to prepare gradient sample extract solutions with concentrations of 30 mg / mL, 20 mg / mL, 10 mg / mL, 5 mg / mL, 2.5 mg / mL, and 0.5 mg / mL.

[0086] HepG2 cells were inoculated in a 96-well plate at a density of 5×10 3 cells per well, and placed in the incubator for 24 h to ensure that the cells were fully adherent. Then, the culture medium was aspirated, and the gradient sample extract solutions with different concentrations described above were added, with 3 replicate wells for each group to improve the reliability of the data. A blank control group (containing only the culture medium) and a negative control group (containing the culture medium and untreated cells) were also set. After 24 h of treatment, the culture medium was aspirated, and 100 μL of culture medium containing 10% CCK-8 reagent was added to each well, and incubated for another 2 h. The absorbance (OD value) of each well was measured at 450 nm wavelength using a microplate reader. The cell survival rate was calculated according to the following formula, and the specific results are shown in Figure 21 .

[0087] , Depend on Figure 21 It can be seen that the cell viability of the sample extract group with a concentration of 0.5 mg / mL was 106.78% (>85%), indicating that the BSC5 / CS4@Cin3 aerogel material prepared in 1.1 of Example 1 had no cell inhibitory effect; the cell viability of the sample extract groups with concentrations of 20 mg / mL and 30 mg / mL were 86.10% and 73.32%, respectively, both higher than the cytotoxicity threshold (70%) specified in ISO 10993-5; as the sample extract concentration increased from 0.5 mg / mL to 30 mg / mL, the cell viability decreased from 106.78% to 75.32%, but always remained within the biosafety range.

[0088] These data confirm that BSC5 / CS4@Cin3 aerogel exhibits no cytotoxicity risk within the food contact concentration range (≤30 mg / mL), meeting the biosafety requirements for food packaging materials. Its sustained-release properties further reduce the risk of acute exposure to active ingredients, providing safety assurance for practical preservation applications.

[0089] Example 9 Analysis of the preservation effect of bamboo shoot shell cellulose-based antibacterial aerogel on chilled meat 9.1 Effect of bamboo shoot shell cellulose-based antibacterial aerogel on the volatile basic nitrogen content of fresh meat during storage The BSC5 / CS4@Cin3 aerogel prepared in 1.1 of Example 1 was used as the fresh-keeping liner in the treatment group. A blank group and a commercial group were set up. The blank group did not use a fresh-keeping liner, while the commercial group used a commercially available fresh-keeping liner. According to the method of "GB 5009.228-2016 Determination of Volatile Basic Nitrogen in Food", the volatile basic nitrogen (TVB-N) content of the treatment group (BSC5 / CS4@Cin3 aerogel), the blank group, and the commercial group during the storage of fresh meat was tested. Specific results are shown in [ 1 ]. Figure 22 .

[0090] TVB-N is the core evaluation index of meat freshness. Its content increase is mainly due to the decomposition of protein by microorganisms and endogenous enzymes, which produces alkaline nitrogen metabolites such as dimethylamine and trimethylamine. Figure 22As can be seen, the TVB-N values ​​of all groups gradually increased with extended storage time. On the eighth day, the TVB-N content in the blank group was 19.65 mg / 100 g, and in the commercial group was 17.87 mg / 100 g, both exceeding the national standard (GB 2707-2016) limit for first-grade fresh meat (15 mg / 100 g). This indicates that the commercial group had lost its ability to preserve fresh meat after the eighth day. However, the TVB-N value of the treated group (BSC5 / CS4@Cin3 aerogel) remained within the limit on the 12th day, demonstrating that the BSC5 / CS4@Cin3 aerogel prepared in this invention maintains fresh meat for up to 12 days.

[0091] 9.2 Effect of bamboo shoot shell cellulose-based antibacterial aerogel on the total bacterial count during storage of chilled meat The BSC5 / CS4@Cin3 aerogel prepared in 1.1 of Example 1 was used as the liner for the treatment group. A blank group and a commercial group were set up. The blank group did not use a fresh-keeping liner, while the commercial group used a commercially available fresh-keeping liner. The total bacterial count (TVC) of fresh meat during storage was tested in accordance with the Chinese national standard "GB4789.2-2022 Food Microbiology Test - Determination of Total Colony Count". Specific results are shown in Figure 23 .

[0092] Depend on Figure 23 On day 8, the TVC values ​​of the blank and commercial groups reached 7.39 log CFU / g and 7.28 log CFU / g, respectively, both exceeding the acceptable threshold of 6.70 log CFU / g. On day 12, the TVC value of the treated group (BSC5 / CS4@Cin3 aerogel) was 5.81 log CFU / g, still below the acceptable threshold of 6.00 log CFU / g, demonstrating its long-lasting antibacterial properties.

[0093] 9.3 Effect of Bamboo Shoot Shell Cellulose-Based Antibacterial Aerogel on the Appearance and Color Change of Fresh Meat During Storage The BSC5 / CS4@Cin3 aerogel prepared in 1.1 of Example 1 was used as the liner for the treatment group. A blank group and a commercial group were set up. The blank group did not use a fresh-keeping liner, while the commercial group used a commercially available fresh-keeping liner. Fresh pork was stored at 4°C. The appearance of the pork samples was photographed on days 0, 2, 4, 6, 8, 10, 12, 14, and 16, and the color change of the meat was measured using a colorimeter. The average values ​​of L*, a*, and b* were calculated, and the total color difference value ΔE was calculated according to the following formula. The specific results are shown in Figure 2. Figure 24 :

[0094] Where L represents the brightness trend, a represents the change trend from green to red, b represents the change trend from blue to yellow, L0, a0, b0 are blank control values, and L*, a*, b* are sample measurement values.

[0095] Depend on Figure 24 It can be seen that with the extension of storage time, on the 4th to 6th day, the surface of the meat samples in the blank group and the commercial group showed obvious browning, accompanied by increased mucus; after 6 days of storage, a white corrupt biofilm formed on the surface of the meat samples in the blank group, with an obvious spoiled odor, while the meat samples in the treated group (BSC5 / CS4@Cin3 aerogel) showed little change in appearance after 12 days of storage, and the surface still maintained good color and texture, indicating that its preservation effect is significant, and the shelf life of fresh meat is 12 days.

[0096] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method for preparing bamboo shoot shell cellulose-based antibacterial aerogel, characterized in that: The following steps are involved: S1. The chitosan powder was dissolved in an aqueous citric acid solution to prepare a chitosan solution; S2. Take a certain amount of bamboo shoot shell cellulose wet powder and mix it with the chitosan solution, and homogenize it using a high-speed shearing machine until the mixture is uniform to obtain a first mixed solution; S3. The first mixed solution is poured into a plastic mold, sealed with plastic wrap, and placed in a -20~-196 ℃ refrigerator for 1-12 h to obtain an aerogel precursor; S4. The aerogel precursor was immersed in an ethanol solution containing aldehyde compounds for 12 h. After the immersion, the aldehyde compounds remaining on the surface were cleaned with anhydrous ethanol, and then dried at 60°C for 2 h to obtain bamboo shoot shell cellulose-based antibacterial aerogel.

2. The method for preparing the bamboo shoot shell cellulose-based antibacterial aerogel according to claim 1, characterized in that: The concentration of the citric acid aqueous solution is 2-4.5 wt %, and the concentration of the chitosan solution is 2-4.5 wt %.

3. The method for preparing the bamboo shoot shell cellulose-based antibacterial aerogel according to claim 1, characterized in that: The solid content of the bamboo shoot shell cellulose in the bamboo shoot shell cellulose wet powder is 8%, the addition amount of the bamboo shoot shell cellulose wet powder is 2.5-10g, and the mass ratio of the bamboo shoot shell cellulose wet powder to the chitosan solution is 1:2-2:

1.

4. The method for producing bamboo shoot shell cellulose-based antibacterial aerogel according to claim 1, characterized in that: The aldehyde compound in the ethanol solution containing the aldehyde compound is selected from any one of cinnamaldehyde, citral, anisaldehyde, vanillin, and salicylaldehyde, and the concentration of the ethanol solution containing the aldehyde compound is 1-4 wt %.

5. The method for producing bamboo shoot shell cellulose-based antibacterial aerogel according to claim 2, characterized in that: The concentration of the citric acid aqueous solution is 4 wt %, and the concentration of the chitosan solution is 4 wt %.

6. The method for producing bamboo shoot shell cellulose-based antibacterial aerogel according to claim 3, characterized in that: The added amount of the wet bamboo shoot shell cellulose powder is 5 g, and the mass ratio of the wet bamboo shoot shell cellulose powder to the chitosan solution is 1:

1.

7. The method for producing bamboo shoot shell cellulose-based antibacterial aerogel according to claim 4, characterized in that: The ethanol solution containing aldehyde compounds is a cinnamaldehyde ethanol solution, and the concentration of the cinnamaldehyde ethanol solution is 3 wt %.

8. The method for producing bamboo shoot shell cellulose-based antibacterial aerogel according to claim 1, characterized in that: In step S3, the freezing temperature of the refrigerator is -80°C and the freezing time is 2 hours.

9. Bamboo shoot shell cellulose-based antibacterial aerogel, characterized in that: The bamboo shoot shell cellulose-based antibacterial aerogel is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the bamboo shoot shell cellulose-based antibacterial aerogel according to claim 9 in the preservation of fresh cold meat.

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