Broad-spectrum antibacterial food preservative film and preparation method thereof

Abstract

The application belongs to the technical field of food intelligent packaging, and discloses a broad-spectrum antibacterial food preservative film and a preparation method thereof, wherein the preparation method comprises the following steps: dissolving an AIE characteristic electron donor in N,N-dimethylformamide, adding phosphorus oxychloride to react, and then performing second post-treatment to obtain a triformal crosslinking agent; dissolving an aminated berberine in anhydrous ethanol, adding the triformal crosslinking agent, and then adding a first chitosan dissolved in a first acidic aqueous solution to obtain a composite antibacterial active substance; dissolving the composite antibacterial active substance in a second acidic aqueous solution, and then adding a second chitosan, an adhesive and glycerol in sequence to obtain a film-forming solution; and the film-forming solution is subjected to a narrow-slit coating and segmented drying film-forming process to obtain the broad-spectrum antibacterial food preservative film. The application can efficiently destroy bacterial cell membranes, realize broad-spectrum, rapid and drug-resistant-free sterilization effect, and the grafted structure endows the film with excellent temperature and humidity resistance stability, thereby significantly prolonging the food preservation period.

Description

Technical Field

[0001] This invention relates to the field of intelligent food packaging technology, specifically to a broad-spectrum antibacterial food preservation film and its preparation method. Background Technology

[0002] Statistics show that approximately one-third of the world's food is wasted due to spoilage, causing not only enormous resource waste and economic losses, but also posing a serious threat to consumer health due to the accumulation of microbial toxins in spoiled food. Food preservation and safety are directly related to public health; however, improper storage and environmental pollution can easily lead to microbial growth, causing food spoilage and the production of toxic substances that harm human health. Therefore, developing efficient, safe, and environmentally friendly food preservation technologies has become one of the core research directions in the food industry.

[0003] In existing technologies, various antibacterial and preservation techniques for food have been publicly reported, among which the more widely used include conventional preservation methods such as freezing and refrigeration, chemical fumigation, and the addition of exogenous preservatives. In "A method for freezing and preserving Procambarus clarkii based on synergistic treatment with a composite cryoprotectant (CN118000239A)," low-temperature freezing combined with a composite preservative is used to achieve antibacterial preservation of Procambarus clarkii, and the treated shrimp retains the original color and flavor of fresh shrimp. In "A method for biological preservation of blueberries (CN103444841B)," pre-cooled blueberries are fumigated with methyl jasmonate to improve the blueberry's inherent resistance and extend its shelf life. However, current technologies are complex to operate, consume a lot of energy, and cannot be applied to broad-spectrum antibacterial preservation of all types of food, greatly limiting their application scenarios and scope. Antibacterial preservation films are gradually replacing traditional preservation methods due to their numerous advantages, including ease of use, controllable cost, scalability, and suitability for food storage and transportation. In "A Modified Atmosphere Packaging Film for Vegetable Preservation and Its Preparation Method (CN116462946A)," a film prepared from polylactic acid and polyethylene glycol selectively permeates oxygen and carbon dioxide, reducing microbial respiration and thus achieving antibacterial preservation of fruits and vegetables. CN118956118A discloses "A Biodegradable Antibacterial Preservative Film and Its Preparation Method." The method and application utilize polycaprolactone composites dispersed on a Mg-MCM-41 molecular sieve carrier to form an antibacterial film, thereby extending the shelf life of strawberries. In "A Nano-Antibacterial Preservative Film and Its Preparation Process (CN114854100A)," nano-titanium dioxide-modified oyster shells, graded nano-zinc oxide powder, and nano-silica materials are added to a film material prepared from carboxymethyl chitosan and hydroxypropyl methylcellulose to reduce moisture evaporation and achieve antibacterial preservation. However, the antibacterial methods of the aforementioned film materials generally suffer from weak antibacterial activity, easy aggregation of antibacterial substances, and susceptibility to migration and failure due to environmental humidity and temperature, resulting in short preservation time and difficulty in meeting long-term storage requirements.

[0004] Therefore, the technical challenges of weak antibacterial activity, easy aggregation of antibacterial substances, and easy migration due to environmental humidity and temperature in existing technologies, which lead to short preservation time, urgently need to be overcome. Summary of the Invention

[0005] The purpose of this invention is to provide a broad-spectrum antibacterial food preservation film and its preparation method to overcome the problems existing in the prior art. This invention can efficiently destroy bacterial cell membranes, achieve a broad-spectrum, rapid, and drug-free bactericidal effect, and the grafted structure endows the film with excellent temperature and humidity resistance stability, significantly extending the food shelf life.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a broad-spectrum antibacterial food preservation film, comprising the following steps: Berberine was mixed with an amine and then subjected to a reflux reaction, followed by a first post-treatment to obtain amine berberine. The AIE characteristic electron donor is dissolved in N,N-dimethylformamide, then phosphorus oxychloride is added to react, and then a second post-treatment is performed to obtain a trialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole. Amine berberine was dissolved in anhydrous ethanol, a trialdehyde crosslinking agent was added, and then chitosan dissolved in the first acidic aqueous solution was added to obtain a composite antibacterial active substance. After dissolving the composite antibacterial active substance in a second acidic aqueous solution, a second chitosan, an adhesive, and glycerin are added sequentially to obtain a film-forming solution. The film-forming solution is then coated and dried in a slit-type segmented drying process to obtain a broad-spectrum antibacterial food preservation film.

[0007] In some embodiments, the amine includes one of 2,4-dimethoxybenzylamine, 3,4-dimethoxybenzylamine, p-methoxybenzylamine, and 3,4,5-trimethoxybenzylamine; the mass ratio of berberine to the amine is 1:(10-30); the temperature of the reflux reaction is 100-120°C, and the time of the reflux reaction is 10-12 h.

[0008] In some embodiments, the first post-processing includes the following steps: The product of the reflux reaction is first filtered to obtain a first precipitate. The first precipitate is first washed to obtain a pretreated precipitate. The pretreated precipitate, methanol and hydrochloric acid are mixed and then filtered second to obtain a second precipitate. The second precipitate is second washed and then dried to obtain amination berberine. The mass ratio of the pretreated precipitate, methanol, and hydrochloric acid is 1:(10-30):(1-3); the first and second washing cycles are performed 3-5 times each; the drying temperature is 60-80℃, and the drying time is 8-12 hours.

[0009] In some embodiments, the mass ratio of the AIE characteristic electron donor to N,N-dimethylformamide and phosphorus oxychloride is 1:(10-30):(8-24). The addition of phosphorus oxychloride for reaction, followed by a second post-treatment to obtain a trialdehyde crosslinking agent, specifically includes the following steps: Under a protective atmosphere, phosphorus oxychloride was added dropwise to an ice-water bath, and the mixture was heated and refluxed to obtain a reaction solution. The reaction solution was then poured into ice water, and the pH was adjusted to neutral. The mixture was then subjected to a third filtration and a third washing to obtain a residue. The residue was purified by column chromatography using a mixed eluent of petroleum ether and ethyl acetate to obtain a purified product. The purified product was then subjected to a first vacuum drying to obtain a trialdehyde crosslinking agent.

[0010] In some embodiments, the heating includes: heating to 90-100°C at a heating rate of 5°C / min; the reflux reaction time is 4-6 h; the mass ratio of petroleum ether to ethyl acetate is 10:1; the temperature of the first vacuum drying is 40-50°C; and the time of the first vacuum drying is 10-12 h.

[0011] In some embodiments, after obtaining the trialdehyde crosslinking agent, the method further includes: After heating the trialdehyde crosslinking agent with an acidified alcohol solution, a dialdehyde crosslinking agent is obtained through a third post-treatment. The mass ratio of the trialdehyde crosslinking agent to the acidified alcohol solution is 1:(10-20); the heating reaction temperature is 40-60℃, and the heating reaction time is 5-8h.

[0012] In some embodiments, the specific steps of the third post-processing include: The heated reaction product was subjected to a fourth filtration and a fourth washing, followed by a second vacuum drying to obtain a dialdehyde crosslinking agent. The temperature of the second vacuum drying is 40~50℃, and the time of the second vacuum drying is 10~12h.

[0013] In some embodiments, the mass ratio of the amination berberine, anhydrous ethanol, trialdehyde crosslinking agent to chitosan dissolved in acidic aqueous solution is 1:(10~30):(2~3):(2~3). The addition of a trialdehyde crosslinking agent, followed by the addition of chitosan dissolved in an acidic aqueous solution, yields a composite antibacterial active substance. Specific steps include: A trialdehyde crosslinking agent was added to obtain a mixed solution. After the mixed solution underwent a first stirring reaction, chitosan dissolved in an acidic aqueous solution was added to undergo a second stirring reaction. The pH of the product from the second stirring reaction was adjusted to neutral, and then the mixture was subjected to a fifth filtration, a fifth washing, and a third vacuum drying to obtain a composite antibacterial active substance. The temperature of the first stirring reaction is 60-70℃, and the time of the first stirring reaction is 1-2 hours; the temperature of the second stirring reaction is 60-80℃, and the time of the second stirring reaction is 10-12 hours; the temperature of the third vacuum drying is 40-60℃, and the time of the third vacuum drying is 10-12 hours.

[0014] In some embodiments, the mass ratio of the composite antibacterial active substance, the second acidic aqueous solution, the second chitosan, the adhesive, and glycerin is 1:(50~100):(1~3):(1~3):(1~2). The second chitosan, adhesive, and glycerin are added sequentially to obtain a film-forming solution. This solution is then subjected to a slit-coating, segmented drying process to obtain a broad-spectrum antibacterial food preservation film. Specific steps include: After adding the second chitosan, a third stirring reaction is carried out. Then, an adhesive and glycerin are added to obtain a mixture. The mixture is then subjected to a fourth stirring reaction to obtain a film-forming liquid. The film-forming liquid is then subjected to a slit coating and segmented drying film-forming process, followed by pre-drying, drying, and cooling and shaping, to obtain a broad-spectrum antibacterial food preservation film. The adhesive includes one of gelatin, pectin, gum arabic, and xanthan gum; the third stirring reaction time is 30-60 min, and the fourth stirring reaction time is 4-6 h; the wet film thickness of the slit-type coating segmented drying film-forming process is 300-500 μm; the pre-drying temperature is 60-70℃, the pre-drying air velocity is 1.5-2 m / s, and the pre-drying time is 5-8 min; the drying temperature is 80-95℃, the drying air velocity is 2.5-3 m / s, and the drying time is 9-12 min; the cooling and setting temperature is 20-25℃, the cooling and setting air velocity is 0 m / s, and the cooling and setting time is 3-6 min.

[0015] Secondly, the present invention provides a broad-spectrum antibacterial food preservation film, which is obtained based on the above-mentioned method for preparing a broad-spectrum antibacterial food preservation film.

[0016] The above technical solution has the following advantages or beneficial effects: Firstly, this invention provides a method for preparing a broad-spectrum antibacterial food preservation film. Berberine is modified by amination and then reacted with a trialdehyde crosslinking agent prepared using an AIE characteristic electron donor and chitosan in a one-pot reaction to form a covalently grafted composite antibacterial active substance. The trialdehyde crosslinking agent not only acts as a bridging group to stably fix the aminated berberine onto the chitosan molecular chain, effectively inhibiting the π-π stacking between berberine molecules and fundamentally avoiding the aggregation and quenching effect of traditional photosensitizers, thus solving the problems of easy aggregation and migration of antibacterial substances; simultaneously, the AIE crosslinking agent significantly enhances the photodynamic activity of aminated berberine, greatly increasing the generation efficiency of reactive oxygen species (such as singlet oxygen and hydroxyl radicals). Under specific light source irradiation, the resulting preservation film can efficiently destroy bacterial cell membranes, achieving a broad-spectrum, rapid, and drug-resistant bactericidal effect. Furthermore, the grafted structure endows the film with excellent temperature and humidity resistance, significantly extending the food shelf life and overcoming the shortcomings of short preservation time in existing technologies.

[0017] In some embodiments, by optimizing the types and ratios of amines and controlling the reflux reaction temperature and time, efficient amination modification of berberine is ensured. The mass ratio (1:10~30) and temperature and time conditions (100~120℃, 10~12h) are conducive to the full amination reaction, improving the yield and purity of amination berberine, providing sufficient reaction sites for subsequent covalent grafting, thereby enhancing the structural stability and antibacterial properties of the composite antibacterial active substance.

[0018] In some embodiments, by defining the specific steps and parameters of the first post-treatment, unreacted amines and byproducts can be effectively removed, improving the purity of amination berberine. Optimized pretreatment precipitate, methanol to hydrochloric acid mass ratio (1:10~30:1~3), and multiple washings (3~5 times) ensure the full progress of the amination reaction and the integrity of the product structure. Drying at 60~80℃ for 8~12 hours avoids the decomposition of heat-sensitive components and ensures the drying effect of the product, laying the foundation for subsequent efficient graft copolymerization.

[0019] In some embodiments, by limiting the optimized mass ratio of AIE electron donor to N,N-dimethylformamide and phosphorus oxychloride (1:10~30:8~24), the formylation reaction is ensured to proceed fully; the addition of phosphorus oxychloride in an ice-water bath effectively suppresses side reactions and improves reaction safety; column chromatography purification combined with a petroleum ether / ethyl acetate mixed eluent enables efficient separation of the target product, yielding a high-purity trialdehyde crosslinking agent. The resulting crosslinking agent has a well-defined structure and few impurities, which is beneficial for subsequent Schiff base grafting reactions with aminated berberine, thereby enhancing the stability and photosensitizing properties of the antibacterial active substance.

[0020] In some embodiments, by further limiting the heating rate (5℃ / min), reaction temperature (90~100℃), and reflux time (4~6h), the formylation reaction was ensured to be mild and controllable, avoiding side reactions and improving the yield and purity of the trialdehyde crosslinking agent. A 10:1 eluent ratio of petroleum ether to ethyl acetate enabled efficient separation and purification of the target product. Vacuum drying at 40~50℃ for 10~12h avoided heat-sensitive decomposition and preserved the aldehyde activity. The synergistic effect of these parameters provided a structurally complete and highly active crosslinking agent for the subsequent Schiff base grafting reaction with amination berberine, ensuring the stable synthesis of the composite antibacterial active substance.

[0021] In some embodiments, by reacting a trialdehyde crosslinking agent with an acidified alcohol at a mass ratio of 1:10-20 at 40-60°C for 5-8 hours, the degree of hydrolysis can be precisely controlled to obtain a dialdehyde crosslinking agent. Compared to the trialdehyde product, the dialdehyde crosslinking agent has fewer aldehyde groups, which can adjust the crosslinking density with the Schiff base reaction of aminated berberine, avoiding steric hindrance caused by excessive crosslinking. This optimizes the dispersion uniformity and photosensitivity of the composite antibacterial active substance in the chitosan substrate, achieving a balance between antibacterial performance and film flexibility.

[0022] In some embodiments, a purification process involving filtration, washing, and vacuum drying at 40-50°C for 10-12 hours effectively removes residual acids and alcohols, improving the purity of the dialdehyde crosslinking agent. The mild vacuum drying conditions prevent thermal oxidation or decomposition of the aldehyde groups, ensuring the integrity of the product structure and its chemical activity. High-purity dialdehyde crosslinking agents facilitate precise and controllable subsequent Schiff base reactions with aminated berberine, providing a reliable guarantee for preparing composite antibacterial active substances with stable graft structures and uniform dispersion.

[0023] In some embodiments, by optimizing the mass ratio of amination berberine, anhydrous ethanol, trialdehyde crosslinking agent, and chitosan (1:10~30:2~3:2~3), the Schiff base reaction is ensured to be sufficient and the grafting rate controllable. A pre-reaction at 60~70℃ for 1~2 hours promotes the bonding between amination berberine and the crosslinking agent, followed by a reaction at 60~80℃ for 10~12 hours to achieve efficient covalent grafting with chitosan, forming a stable network structure. Mild vacuum drying (40~60℃) protects the active functional groups. These parameters synergistically and effectively inhibit the aggregation and migration of antibacterial agents, enhancing the structural stability and long-lasting antibacterial properties of the composite active substance.

[0024] In some embodiments, by optimizing the ratio of the composite antibacterial active substance to chitosan, adhesive, glycerin and other components (1:50~100:1~3:1~3:1~2), combined with a precisely controlled segmented coating and drying process, uniform film thickness, good flexibility, and stable dispersion of antibacterial active substances are achieved, avoiding agglomeration and migration, and significantly improving the mechanical stability and long-lasting antibacterial performance of the food preservation film.

[0025] Secondly, this invention provides a broad-spectrum antibacterial food preservation film. Amine-modified berberine is stably fixed to a chitosan matrix through covalent grafting, and combined with the photosensitizing effect of an AIE crosslinking agent, the resulting film exhibits uniform dispersion of antibacterial active substances that are not prone to aggregation or migration. The product efficiently generates active oxygen under light irradiation, achieving broad-spectrum sterilization, while also possessing good mechanical properties and moisture and temperature resistance, effectively extending the shelf life of food. Attached Figure Description

[0026] Figure 1This is a schematic flowchart illustrating a method for preparing a broad-spectrum antibacterial food preservation film according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention under visible light; Figure 3 This is a test image of the flexibility of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention under visible light. Figure 4 This is the excitation fluorescence image of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention under ultraviolet light; Figure 5 This is a fluorescence image of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention under ultraviolet light after bending excitation. Figure 6 This is a comparison chart of the preservation effects of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention and commercially available polyethylene food preservation film on cherry tomatoes at 25°C. Figure 7 This is a comparison chart of the antibacterial effects of the broad-spectrum antibacterial food preservation film obtained in Example 1 of the present invention and commercially available polyethylene food preservation film against Staphylococcus aureus. Figure 8 This is a comparison of the Fourier transform infrared spectra of triphenylamine and aldehyde triphenylamine monomers in Example 1 of the present invention; Figure 9 This is a comparison of the Fourier transform infrared spectra of grafted chitosan, amination of berberine, and aldehyde-modified triphenylamine monomer in Example 1 of the present invention. Figure 10 This is the 1H NMR spectrum of the chitosan grafted in Example 1 of the present invention; Figure 11 This is a schematic diagram of the reaction process of 2,4-dimethoxybenzylamine with methanol and hydrochloric acid according to the present invention; Figure 12 This is a schematic diagram of the reaction process between N,N-dimethylformamide and phosphorus oxychloride according to the present invention; Figure 13 This is a schematic diagram of the reaction process between the trialdehyde crosslinking agent or dialdehyde crosslinking agent of the present invention and chitosan. Detailed Implementation

[0027] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In existing technologies, various antibacterial and preservation techniques for food have been publicly reported, among which the more widely used include conventional preservation methods such as freezing and refrigeration, chemical fumigation, and the addition of exogenous preservatives. In "A method for freezing and preserving Procambarus clarkii based on synergistic treatment with a composite cryoprotectant (CN118000239A)," low-temperature freezing combined with a composite preservative is used to achieve antibacterial preservation of Procambarus clarkii, and the treated shrimp retains the original color and flavor of fresh shrimp. In "A method for biological preservation of blueberries (CN103444841B)," pre-cooled blueberries are fumigated with methyl jasmonate to improve the blueberry's inherent resistance and extend its shelf life. However, current technologies are complex to operate, consume a lot of energy, and cannot be applied to broad-spectrum antibacterial preservation of all types of food, greatly limiting their application scenarios and scope. Antibacterial preservation films are gradually replacing traditional preservation methods due to their numerous advantages, including ease of use, controllable cost, scalability, and suitability for food storage and transportation. In "A Modified Atmosphere Packaging Film for Vegetable Preservation and Its Preparation Method (CN116462946A)," a film prepared from polylactic acid and polyethylene glycol selectively permeates oxygen and carbon dioxide, reducing microbial respiration and thus achieving antibacterial preservation of fruits and vegetables. CN118956118A discloses "A Biodegradable Antibacterial Preservative Film and Its Preparation Method." The method and application utilize polycaprolactone composites dispersed on a Mg-MCM-41 molecular sieve carrier to form an antibacterial film, thereby extending the shelf life of strawberries. In "A Nano-Antibacterial Preservative Film and Its Preparation Process (CN114854100A)," nano-titanium dioxide-modified oyster shells, graded nano-zinc oxide powder, and nano-silica materials are added to a film material prepared from carboxymethyl chitosan and hydroxypropyl methylcellulose to reduce moisture evaporation and achieve antibacterial preservation. However, the antibacterial methods of the aforementioned film materials generally suffer from weak antibacterial activity, easy aggregation of antibacterial substances, and susceptibility to migration and failure due to environmental humidity and temperature, resulting in short preservation time and difficulty in meeting long-term storage requirements.

[0031] Therefore, developing an antibacterial preservation film that combines high efficiency, broad-spectrum antibacterial properties, safety, environmental friendliness, long-lasting freshness preservation, and stable mechanical properties has become a technical challenge that urgently needs to be overcome in the field of food preservation materials.

[0032] This embodiment provides a method for preparing a broad-spectrum antibacterial food preservation film. See [link to relevant documentation]. Figure 1 This includes the following steps: Step 1: Berberine and the amine are mixed and heated under reflux, followed by a first post-treatment to obtain amine berberine; Step 2: Dissolve the AIE characteristic electron donor in N,N-dimethylformamide, add phosphorus oxychloride to react, and then perform a second post-treatment to obtain a trialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole. Step 3: Dissolve the amination berberine in anhydrous ethanol, add the trialdehyde crosslinking agent, and then add the first chitosan dissolved in the first acidic aqueous solution to obtain a composite antibacterial active substance. Step 4: After dissolving the composite antibacterial active substance in the second acidic aqueous solution, add the second chitosan, adhesive and glycerin in sequence to obtain the film-forming solution. Use the slit coating and segmented drying film-forming process to obtain a broad-spectrum antibacterial food preservation film.

[0033] This invention aims to provide a broad-spectrum antibacterial preservation film and its preparation method, which possesses highly efficient antibacterial properties, safety and environmental friendliness, and long-lasting preservation characteristics. This addresses the problems of existing food preservation films, such as short antibacterial duration, easy aggregation and loss of antibacterial agents, and weak antibacterial effect. This invention modifies berberine by amination, and then prepares a composite antibacterial active substance in a one-pot process using an aldehyde crosslinking agent, effectively immobilizing the amination berberine on chitosan. On one hand, the aldehyde crosslinking agent can significantly improve the photodynamic activity of berberine and increase the efficiency of reactive oxygen species (ROS) generation; on the other hand, the effective dispersion of berberine in the chitosan substrate can prevent the accumulation of π-π, which leads to low ROS generation efficiency.

[0034] Example 1: This embodiment provides a method for preparing a broad-spectrum antibacterial food preservation film, including the following steps: Step 1: Berberine and the amine are mixed and heated under reflux, followed by a first post-treatment to obtain amine berberine.

[0035] Specifically, 5g of berberine was added to 50g of 2,4-dimethoxybenzylamine, and then refluxed at 100℃ for 12h. After cooling to 25℃, the mixture was washed three times with acetone and filtered to obtain a pretreated precipitate. Then, 3g of the pretreated precipitate was taken, and 30g of methanol and 3g of 65% hydrochloric acid were added. The mixture was stirred at 25℃ for 6h. The reaction solution was then filtered, and the precipitate was washed three times with acetone and dried at 60℃ for 12h to obtain amination-modified berberine.

[0036] Step 2: Dissolve the AIE characteristic electron donor in N,N-dimethylformamide, add phosphorus oxychloride to react, and then perform a second post-treatment to obtain a trialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole.

[0037] Specifically, 3g of triphenylamine was dissolved in 30g of N,N-dimethylformamide, and then 24g of phosphorus oxychloride solution was slowly added dropwise in an ice-water bath at 0℃ under nitrogen protection. After the addition was complete, the temperature was gradually increased to 90℃ at a rate of 5℃ / min, and the reaction was refluxed under nitrogen atmosphere for 6h. After the reaction was completed, the reaction solution was poured into 300g of ice water at 0℃, and the pH was adjusted to neutral with 1mol / L sodium hydroxide solution. The residue was then collected by filtration and washing. The residue was purified by column chromatography using a mixed solution of 300g of petroleum ether and ethyl acetate (petroleum ether:ethyl acetate mass ratio = 10:1) as the eluent. The purified solid product was vacuum dried at 40℃ for 12h to obtain the trialdehyde crosslinking agent.

[0038] Step 3: Dissolve the amination berberine in anhydrous ethanol, add the trialdehyde crosslinking agent, and then add the first chitosan dissolved in the first acidic aqueous solution to obtain a composite antibacterial active substance.

[0039] Specifically, 1g of amination berberine was dissolved in 10g of anhydrous ethanol, and then 2g of trialdehyde crosslinking agent was added. The mixture was stirred at 60℃ for 2h, and then 2g of chitosan solution dissolved in 1% acetic acid aqueous solution (acetic acid aqueous solution: chitosan mass ratio = 100:1) was added. The mixture was stirred at 60℃ for 12h. The pH of the reaction solution was adjusted to neutral with 1mol / L sodium hydroxide solution and filtered. The precipitate was washed with ethanol and then vacuum dried at 40℃ for 12h to obtain the composite antibacterial active substance.

[0040] Step 4: After dissolving the composite antibacterial active substance in the second acidic aqueous solution, add the second chitosan, adhesive and glycerin in sequence to obtain the film-forming solution. Use the slit coating and segmented drying film-forming process to obtain a broad-spectrum antibacterial food preservation film.

[0041] Specifically, 1g of the composite antibacterial active substance was dissolved in 50g of 1% acetic acid aqueous solution, and then 1g of chitosan was added and stirred at room temperature (25℃) for 30min. Then, 1g of gelatin and 1g of glycerol were added to the mixture, and stirred at room temperature (25℃) for 4h to obtain a uniformly dispersed film-forming solution. The wet film thickness was controlled to be 300 μm, and a slit coating and segmented drying film-forming process was adopted. The pre-drying temperature was set to 60℃, the pre-drying air velocity was set to 1.5m / s, and the pre-drying time was 8min. The drying temperature was set to 80℃, the air velocity was set to 2.5m / s, and the drying time was 12min. The cooling and setting temperature was set to 25℃, the cooling and setting air velocity was set to 0m / s, and the cooling and setting time was 3min to obtain a broad-spectrum antibacterial food preservation film.

[0042] Step 5: The broad-spectrum antibacterial food preservation film obtained in Example 1 is used for the preservation packaging of cherry tomatoes. After being kept at room temperature (25-28℃) and under natural light for 5 days, the titratable acid content of the cherry tomatoes is 0.53% and the hardness is 0.43 kg / cm². Compared with conventional packaging methods, this significantly improves the storage quality and shelf life of cherry tomatoes, extending the preservation time of cherry tomatoes to 10 days.

[0043] See Figure 2 The broad-spectrum antibacterial food preservation film obtained in Example 1 is uniformly transparent under visible light. (See [link]). Figure 3 The broad-spectrum antibacterial food preservation film obtained in Example 1 has good flexibility under visible light and can be bent freely without breaking.

[0044] See Figure 4 The broad-spectrum antibacterial food preservation film obtained in Example 1 exhibits bright fluorescence emission under 365 nm ultraviolet light excitation. See [link to example]. Figure 5 The broad-spectrum antibacterial food preservation film obtained in Example 1 retains stable fluorescence properties after being bent under 365 nm ultraviolet light excitation.

[0045] See Figure 6 This study demonstrates a comparison of the preservation effects of the broad-spectrum antibacterial food preservation film obtained in Example 1 and commercially available polyethylene food preservation film on cherry tomatoes at 25°C. Under natural light storage conditions, the cherry tomatoes packaged with the broad-spectrum antibacterial food preservation film obtained in Example 1 showed no obvious signs of spoilage or decay after 10 days of storage, maintaining good edible value. In contrast, the cherry tomatoes packaged with commercially available polyethylene food preservation film showed obvious softening of the flesh by the 5th day of storage, indicating that the fruit had already spoiled internally.

[0046] See Figure 7 This paper compares the antibacterial effects of the broad-spectrum antibacterial food preservation film obtained in Example 1 and commercially available polyethylene food preservation film against Staphylococcus aureus. As shown in the figure, during a 5-day constant-temperature incubation period, Staphylococcus aureus colonies proliferated extensively on the agar medium of the commercially available polyethylene food preservation film group, while the colony count of the broad-spectrum antibacterial food preservation film obtained in Example 1 was significantly lower than that of the polyethylene control group, demonstrating an inhibitory effect on Staphylococcus aureus and indicating that the film has excellent antibacterial properties.

[0047] See Figures 8-9 The Fourier transform infrared spectra of the synthesized substances in each step of Example 1 were characterized, wherein, Figure 8 This is a comparison of the Fourier transform infrared spectra of triphenylamine and aldehyde-modified triphenylamine monomers, in the range of 3000–3100 cm⁻¹. -1 The peak at 1590 cm⁻¹ is attributed to the absorption peak of the aromatic CH stretching vibration. -1and 1500 cm -1 The peak at 1270 cm⁻¹ is attributed to the characteristic peak of the C=C stretching vibration of the benzene ring skeleton, while the peak at 1270 cm⁻¹ is also significant. -1 A CN stretching vibration peak was observed at 2820 cm⁻¹; compared with pure triphenylamine, the infrared spectrum of aldehyde-modified triphenylamine showed a peak at 2820 cm⁻¹. -1 and 2720 cm -1 A new peak appeared at 1695 cm⁻¹, attributed to the characteristic double peak of the CH stretching vibration of the aldehyde group. -1 A strong absorption peak was observed, which is attributed to the C=O stretching vibration of the aromatic aldehyde, further proving the successful preparation of aldehyde-modified triphenylamine molecules. Figure 9 Characterized the efficacy of amination of berberine, 3200~3500 cm⁻¹ -1 The broad absorption band at 2920 cm⁻¹ is attributed to the stretching vibration of amino NH₃; -1 The nearby absorption peak is due to the stretching vibration of aliphatic CH4; 1630 cm⁻¹ -1 The strong peak at 1650 cm⁻¹ is attributed to the C=N stretching vibration of the isoquinoline ring in the berberine nucleus, indicating successful modification of berberine by amination; the composite active substance prepared by grafting onto chitosan exhibits a peak at 1650 cm⁻¹. -1 and 1560 cm -1 The characteristic peaks at 3200–3600 cm⁻¹ are, in order, C=O stretching vibration, NH bending vibration, and CN stretching vibration, respectively. -1 A broad and strong absorption band appears at 2920 cm⁻¹, which is attributed to the overlapping peaks of the OH stretching vibration and the free amino NH stretching vibration on the chitosan backbone; -1 and 2850 cm -1 The absorption peaks at these locations correspond to the asymmetric stretching vibrations of methylene-CH2-, indicating that the composite antibacterial active substance grafted onto the chitosan molecule was successfully synthesized.

[0048] See Figure 10 The figure shows the 1H NMR spectrum of chitosan grafted in Example 1. As shown, the characteristic peak observed at 8.3 ppm is attributed to the imine bond (-CH=N-) proton formed by the Schiff base condensation reaction between the aldehyde group and the amino group. The characteristic peak at 4.9 ppm is attributed to the methylene proton of the berberine side chain. The methoxy (-OCH3) proton on the berberine core has an absorption peak at 3.8 ppm. In addition, the chemical shift of the amino proton at C2 position of chitosan is slightly shifted. This is due to the change in the electron cloud density around the amino group after the formation of the imine bond. This further proves that berberine is grafted onto chitosan through aldehyde triphenylamine.

[0049] Example 2: This embodiment provides a method for preparing a broad-spectrum antibacterial food preservation film, including the following steps: Step 1: Berberine and the amine are mixed and heated under reflux, followed by a first post-treatment to obtain amine berberine.

[0050] Specifically, 5g of berberine was added to 75g of p-methoxybenzylamine, and the mixture was refluxed at 110℃ for 11h. The mixture was then cooled to 25℃ and washed four times with acetone and filtered to obtain a pretreated precipitate. 3g of the pretreated precipitate was then taken, and 45g of methanol and 4.5g of 65% hydrochloric acid were added. The mixture was stirred at 25℃ for 5h. The reaction solution was then filtered, and the precipitate was washed four times with acetone and dried at 70℃ for 10h to obtain amination-modified berberine.

[0051] Step 2: Dissolve the AIE characteristic electron donor in N,N-dimethylformamide, add phosphorus oxychloride to react, and then perform a second post-treatment to obtain a trialdehyde crosslinking agent. After heating the trialdehyde crosslinking agent with an acidified alcohol solution, perform a third post-treatment to obtain a dialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole.

[0052] Specifically, 5g of tetraphenylethylene was dissolved in 75g of N,N-dimethylformamide. Then, under nitrogen protection, 60g of phosphorus oxychloride solution was slowly added dropwise in an ice-water bath at 0℃. After the addition was complete, the temperature was gradually increased to 92℃ at a rate of 5℃ / min. The mixture was refluxed under a nitrogen atmosphere for 5.5h. After the reaction was completed, the reaction solution was poured into 550g of 0℃ ice water, and the pH was adjusted to neutral with 1mol / L sodium hydroxide solution. The residue was then collected by filtration and washing. The residue was purified by column chromatography using a mixed solution of 500g of petroleum ether and ethyl acetate (petroleum ether:ethyl acetate mass ratio = 10:1) as the eluent. The purified solid product was vacuum dried at 45℃ for 11h to obtain a trialdehyde crosslinking agent. Then, 3g of the trialdehyde crosslinking agent was added to 30g of sulfuric acid-acidified methanol solution (sulfuric acid:methanol mass ratio = 1:10), and reacted at 40℃ for 8h. After filtration and washing, the precipitate was vacuum dried at 40℃ for 12h to obtain a dialdehyde crosslinking agent.

[0053] Step 3: Based on the amination of berberine dissolved in anhydrous ethanol, a trialdehyde crosslinking agent is added, followed by the addition of the first chitosan dissolved in the first acidic aqueous solution to obtain a composite antibacterial active substance.

[0054] Specifically, 1g of amination berberine was dissolved in 15g of anhydrous ethanol, and then 2g of dialdehyde crosslinking agent was added. The mixture was stirred at 65℃ for 1.5h, and then 2.5g of chitosan solution dissolved in 1% acetic acid aqueous solution (acetic acid aqueous solution: chitosan mass ratio = 100:1) was added. The mixture was then stirred at 65℃ for 11h. The pH of the reaction solution was adjusted to neutral with 1mol / L sodium hydroxide solution and filtered. The precipitate was washed with ethanol and then vacuum dried at 45℃ for 11h to obtain the composite antibacterial active substance.

[0055] Step 4: After dissolving the composite antibacterial active substance in the second acidic aqueous solution, add the second chitosan, adhesive and glycerin in sequence to obtain the film-forming solution. Use the slit coating and segmented drying film-forming process to obtain a broad-spectrum antibacterial food preservation film.

[0056] Specifically, 1g of the composite antibacterial active substance was dissolved in 70g of 1% acetic acid aqueous solution, and then 1.5g of chitosan was added and stirred at room temperature (25℃) for 40min. Then, 1.5g of gelatin and 1.5g of glycerol were added to the mixture, and stirred at room temperature (25℃) for 5h to obtain a uniformly dispersed film-forming solution. The wet film thickness was controlled to be 400μm, and a slit coating and segmented drying film-forming process was adopted. The pre-drying temperature was set to 65℃, the pre-drying air velocity was set to 1.5m / s, and the pre-drying time was 7min. The drying temperature was set to 85℃, the drying air velocity was set to 3m / s, and the drying time was 11min. The cooling and setting temperature was set to 25℃, the cooling and setting air velocity was set to 0m / s, and the cooling and setting time was 4min to obtain a broad-spectrum antibacterial food preservation film.

[0057] Step 5: The broad-spectrum antibacterial food preservation film obtained in Example 2 was used for packaging bread and pastries. After being kept at room temperature and light conditions of 25-28℃ for one week, the bread and pastries showed no mold growth, no off-odors, and the number of molds was 27 CFU / g (≤50 CFU / g), which significantly extended the shelf life of the bread and pastries.

[0058] Example 3: This embodiment provides a method for preparing a broad-spectrum antibacterial food preservation film, including the following steps: Step 1: Berberine and the amine are mixed and heated under reflux, followed by a first post-treatment to obtain amine berberine.

[0059] Specifically, 5g of berberine was added to 100g of 3,4-dimethoxybenzylamine, and then refluxed at 115℃ for 10.5h. After cooling to 25℃, the mixture was washed four times with acetone and filtered to obtain a pretreated precipitate. Then, 3g of the pretreated precipitate was taken, and 60g of methanol and 6g of 65% hydrochloric acid were added. The mixture was stirred at 25℃ for 4.5h. The reaction solution was then filtered, and the precipitate was washed four times with acetone and dried at 75℃ for 9h to obtain amination-modified berberine.

[0060] Step 2: Dissolve the AIE characteristic electron donor in N,N-dimethylformamide, add phosphorus oxychloride to react, and then perform a second post-treatment to obtain a trialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole.

[0061] Specifically, 3g of N-phenylcarbazole was dissolved in 60g of N,N-dimethylformamide, and then 48g of phosphorus oxychloride solution was slowly added dropwise in a 0℃ ice-water bath under nitrogen protection. After the addition was complete, the temperature was gradually increased to 97℃ at a rate of 5℃ / min, and the reaction was refluxed for 5h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was poured into 345g of 0℃ ice water, and the pH was adjusted to neutral with 1mol / L sodium hydroxide solution. The residue was then collected by filtration and washing. The residue was purified by column chromatography using a mixed solution of 360g of petroleum ether and ethyl acetate (petroleum ether:ethyl acetate mass ratio = 10:1) as the eluent. The purified solid product was vacuum dried at 50℃ for 10h to obtain the trialdehyde crosslinking agent.

[0062] Step 3: Based on the amination of berberine dissolved in anhydrous ethanol, a trialdehyde crosslinking agent is added, followed by the addition of the first chitosan dissolved in the first acidic aqueous solution to obtain a composite antibacterial active substance.

[0063] Specifically, 1g of amination berberine was dissolved in 20g of anhydrous ethanol, and then 2.5g of trialdehyde crosslinking agent was added. The mixture was stirred at 70℃ for 1h, and then 3g of chitosan solution dissolved in 1% acetic acid aqueous solution (acetic acid aqueous solution: chitosan mass ratio = 100:1) was added. The mixture was then stirred at 70℃ for 10.5h. The pH of the reaction solution was adjusted to neutral with 1mol / L sodium hydroxide solution and filtered. The precipitate was washed with ethanol and then vacuum dried at 50℃ for 10.5h to obtain the composite antibacterial active substance.

[0064] Step 4: After dissolving the composite antibacterial active substance in the second acidic aqueous solution, add the second chitosan, adhesive and glycerin in sequence to obtain the film-forming solution. Use the slit coating and segmented drying film-forming process to obtain a broad-spectrum antibacterial food preservation film.

[0065] Specifically, 1g of the composite antibacterial active substance was dissolved in 90g of 1% acetic acid aqueous solution, and then 2g of chitosan was added and stirred at room temperature (25℃) for 50min. Then, 2g of gelatin and 2g of glycerol were added to the mixture and stirred at room temperature (25℃) for 5.5h to obtain a uniformly dispersed film-forming solution. The wet film thickness was controlled to be 450μm, and a slit coating and segmented drying film-forming process was adopted. The pre-drying temperature was set to 65℃, the pre-drying air velocity was set to 2m / s, and the pre-drying time was 6min. The drying temperature was set to 90℃, the drying air velocity was set to 3m / s, and the drying time was 10min. The cooling and setting temperature was set to 20℃, the cooling and setting air velocity was set to 0m / s, and the cooling and setting time was 5min to obtain a broad-spectrum antibacterial food preservation film.

[0066] Step 5: The broad-spectrum antibacterial food preservation film obtained in Example 3 is used for packaging fresh pork. After being kept in a transparent refrigerator at 4°C for 7 days, the volatile basic nitrogen content of the pork is 8.6 mg / 100g, and it still remains fresh. Compared with conventional packaging, the preservation time of pork is extended by 4 days.

[0067] Example 4: This embodiment provides a method for preparing a broad-spectrum antibacterial food preservation film, including the following steps: Step 1: Berberine and the amine are mixed and heated under reflux, followed by a first post-treatment to obtain amine berberine.

[0068] Specifically, 5g of berberine was added to 150g of 3,4,5-trimethoxybenzylamine, and the mixture was refluxed at 120℃ for 10h. The mixture was then cooled to 25℃ and washed five times with acetone and filtered to obtain a pretreated precipitate. 3g of the pretreated precipitate was then taken, and 90g of methanol and 9g of 65% hydrochloric acid were added. The mixture was stirred at 25℃ for 4h. The reaction solution was then filtered, and the precipitate was washed five times with acetone and dried at 80℃ for 8h to obtain amination-modified berberine.

[0069] Step 2: Dissolve the AIE characteristic electron donor in N,N-dimethylformamide, add phosphorus oxychloride to react, and then perform a second post-treatment to obtain a trialdehyde crosslinking agent. After heating the trialdehyde crosslinking agent with an acidified alcohol solution, perform a third post-treatment to obtain a dialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole.

[0070] Specifically, 5g of triphenylamine was dissolved in 150g of N,N-dimethylformamide, and then 120g of phosphorus oxychloride solution was slowly added dropwise in a 0℃ ice-water bath under nitrogen protection. After the addition was complete, the temperature was gradually increased to 100℃ at a rate of 5℃ / min, and the reaction was refluxed for 4h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was poured into 600g of 0℃ ice water, and the pH was adjusted to neutral with 1mol / L sodium hydroxide solution. The residue was then collected by filtration and washing. The residue was purified by column chromatography using a mixed solution of 600g of petroleum ether and ethyl acetate (petroleum ether:ethyl acetate mass ratio = 10:1) as the eluent. The purified solid product was vacuum dried at 50℃ for 10h to obtain the trialdehyde crosslinking agent. Then, 3g of trialdehyde crosslinking agent was added to 60g of sulfuric acid-acidified methanol solution (sulfuric acid:methanol mass ratio = 1:10), and reacted at 60℃ for 5h. After filtration and washing, the precipitate was dried under vacuum at 50℃ for 10h to obtain dialdehyde crosslinking agent.

[0071] Step 3: Based on the amination of berberine dissolved in anhydrous ethanol, a trialdehyde crosslinking agent is added, followed by the addition of the first chitosan dissolved in the first acidic aqueous solution to obtain a composite antibacterial active substance.

[0072] Specifically, 1g of amination berberine was dissolved in 30g of anhydrous ethanol, and then 3g of dialdehyde crosslinking agent was added. The mixture was stirred at 70℃ for 1h, and then 3g of chitosan solution dissolved in 1% acetic acid aqueous solution (acetic acid aqueous solution: chitosan mass ratio = 100:1) was added. The mixture was then stirred at 80℃ for 10h. The pH of the reaction solution was adjusted to neutral with 1mol / L sodium hydroxide solution and filtered. The precipitate was washed with ethanol and then vacuum dried at 60℃ for 10h to obtain the composite antibacterial active substance.

[0073] Step 4: After dissolving the composite antibacterial active substance in the second acidic aqueous solution, add the second chitosan, adhesive and glycerin in sequence to obtain the film-forming solution. Use the slit coating and segmented drying film-forming process to obtain a broad-spectrum antibacterial food preservation film.

[0074] Specifically, 1g of the composite antibacterial active substance was dissolved in 100g of 1% acetic acid aqueous solution, and then 3g of chitosan was added and stirred at room temperature (25℃) for 60min. Then, 3g of gelatin and 2g of glycerol were added to the mixture, and stirred at room temperature (25℃) for 6h to obtain a uniformly dispersed film-forming solution. The wet film thickness was then controlled to be 500μm, and a slit coating and segmented drying film-forming process was adopted. The pre-drying temperature was set to 70℃, the pre-drying air velocity was set to 2m / s, and the pre-drying time was 5min. The drying temperature was set to 95℃, the drying air velocity was set to 2.5m / s, and the drying time was 9min. The cooling and setting temperature was set to 20℃, the cooling and setting air velocity was set to 0m / s, and the cooling and setting time was 6min to obtain a broad-spectrum antibacterial food preservation film.

[0075] Step 5: The broad-spectrum antibacterial food preservation film obtained in Example 4 was used for packaging fresh fish. After being kept at 4°C for 20 days, the volatile basic nitrogen content of the fish was 7.3 mg / 100g, indicating that the fish was still fresh. Compared with traditional chilled fish, the preservation time of the fish was extended by 5 days.

[0076] This invention uses amine berberine as the core antibacterial functional component. Different aldehyde cross-linking agents are used to covalently graft and fix the amine berberine onto the chitosan molecular chain, forming a structurally stable antibacterial active substance. Under specific light source irradiation, this antibacterial active substance can efficiently generate reactive oxygen species (including singlet oxygen and hydroxyl radicals), thereby rapidly destroying harmful microorganisms such as bacteria and mold growing on the surface of food. This achieves a broad-spectrum, rapid, and non-drug-resistant bactericidal effect, effectively ensuring food freshness and food safety. Specific advantages are as follows: First, the antibacterial food preservation film prepared by this invention has a broad-spectrum bactericidal effect. Using aminated berberine as the core antibacterial functional component, different aldehyde crosslinking agents are selected to directionally graft aminated berberine onto the chitosan molecular chain through the formation of imine bonds via Schiff bases. This forms a structurally stable, non-dissociable, and uniformly dispersed antibacterial active substance, fundamentally solving the problem of loose binding, aggregation, and easy migration and loss of traditional antibacterial components and carriers. Under specific light source irradiation, the antibacterial active substance can efficiently generate reactive oxygen species (including singlet oxygen, hydroxyl radicals, etc.) through the enhancement effect of the crosslinking agent on the photosensitivity of aminated berberine and the optimization effect on dispersion stability. This disrupts the integrity of bacterial cell membranes, thereby achieving a bactericidal effect, effectively delaying the food spoilage process, and ensuring the freshness of food.

[0077] Secondly, this invention provides a new technical method for using chitosan in preservation packaging materials. Specifically, berberine is modified with an amination reagent, and then immobilized onto chitosan using a one-pot Schiff base reaction with different aldehyde crosslinking agents. A photosensitizer absorbs light of a specific wavelength to generate reactive oxygen species and other substances that disrupt the integrity of bacterial cell membranes, thereby achieving a broad-spectrum bactericidal effect. Using 2,4-dimethoxybenzylamine and triphenylamine as examples, the chemical reaction process is described below. Figures 11-13 .

[0078] Furthermore, this invention achieves synergistic optimization of photosensitivity and significantly improves the efficiency of reactive oxygen species (ROS) generation by preparing different aldehyde crosslinking agents. These aldehyde crosslinking agents, such as dialdehyde / trialdehyde, not only perform crosslinking functions but also form a photosensitizing synergistic system with aminated berberine. On the one hand, they can regulate the molecular motion of aminated berberine, inhibiting its intermolecular π-π accumulation and overcoming the aggregation quenching effect of traditional photosensitizers at its root. On the other hand, their strong electron-donating ability enhances the photosensitizer's absorption efficiency of visible light, lowers the photoexcitation energy threshold, and promotes the efficient generation of ROS (singlet oxygen, hydroxyl radicals). Compared to antibacterial substances prepared by single grafting substitution, these ROS are better dispersed in the substrate material.

[0079] Furthermore, the present invention exhibits broad-spectrum and highly efficient antibacterial effects, with excellent safety and compatibility. By leveraging the unique chain structure and hydrophilic-hydrophobic regulatory effects of chitosan molecules, the antibacterial active substances are uniformly dispersed in the chitosan carrier and subsequent film matrix, forming a stable dispersion system. This avoids the defects of photosensitizer agglomeration and aggregation quenching in physical blending techniques. The grafting structure can hinder the Π-Π stacking between amination berberine molecules, thereby avoiding the aggregation quenching effect and endowing the film with highly efficient antibacterial properties.

[0080] Finally, the broad-spectrum antibacterial food preservation products prepared by this invention all use biomass raw materials. The grafting reaction of amination berberine and chitosan is completed in a one-pot process. The preparation process is simple and controllable, realizing the high-value utilization of biomass resources. At the same time, the loading of composite antibacterial active substances can be flexibly adjusted by controlling the amount of amination berberine and different aldehyde crosslinking agents, providing a new technology for the preparation of antibacterial preservation films for various foods such as fruits, vegetables, meats, and pastries.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0082] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention fall within the scope of protection of this invention.

Claims

1. A method for preparing a broad-spectrum antibacterial food preservation film, characterized in that, Includes the following steps: Berberine was mixed with an amine and then subjected to a reflux reaction, followed by a first post-treatment to obtain amine berberine. The AIE characteristic electron donor is dissolved in N,N-dimethylformamide, then phosphorus oxychloride is added to react, and then a second post-treatment is performed to obtain a trialdehyde crosslinking agent. The AIE characteristic electron donor includes one of triphenylamine, tetraphenylethylene, and N-phenylcarbazole. Amine berberine was dissolved in anhydrous ethanol, a trialdehyde crosslinking agent was added, and then chitosan dissolved in the first acidic aqueous solution was added to obtain a composite antibacterial active substance. After dissolving the composite antibacterial active substance in a second acidic aqueous solution, a second chitosan, an adhesive, and glycerin are added sequentially to obtain a film-forming solution. The film-forming solution is then coated and dried in a slit-type segmented drying process to obtain a broad-spectrum antibacterial food preservation film.

2. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, The amine includes one of 2,4-dimethoxybenzylamine, 3,4-dimethoxybenzylamine, p-methoxybenzylamine, and 3,4,5-trimethoxybenzylamine; the mass ratio of berberine to the amine is 1:(10-30); the temperature of the reflux reaction is 100-120°C, and the reflux reaction time is 10-12 h.

3. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, The first post-processing includes the following steps: The product of the reflux reaction is first filtered to obtain a first precipitate. The first precipitate is first washed to obtain a pretreated precipitate. The pretreated precipitate, methanol and hydrochloric acid are mixed and then filtered second to obtain a second precipitate. The second precipitate is second washed and then dried to obtain amination berberine. The mass ratio of the pretreated precipitate, methanol, and hydrochloric acid is 1:(10-30):(1-3); the first and second washing cycles are performed 3-5 times each; the drying temperature is 60-80℃, and the drying time is 8-12 hours.

4. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, The mass ratio of the AIE characteristic electron donor to N,N-dimethylformamide and phosphorus oxychloride is 1:(10-30):(8-24). The addition of phosphorus oxychloride for reaction, followed by a second post-treatment to obtain a trialdehyde crosslinking agent, specifically includes the following steps: Under a protective atmosphere, phosphorus oxychloride was added dropwise to an ice-water bath, and the mixture was heated and refluxed to obtain a reaction solution. The reaction solution was then poured into ice water, and the pH was adjusted to neutral. The mixture was then subjected to a third filtration and a third washing to obtain a residue. The residue was purified by column chromatography using a mixed eluent of petroleum ether and ethyl acetate to obtain a purified product. The purified product was then subjected to a first vacuum drying to obtain a trialdehyde crosslinking agent.

5. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 4, characterized in that, The heating includes: heating to 90-100°C at a heating rate of 5°C / min; the reflux reaction time is 4-6 h; the mass ratio of petroleum ether to ethyl acetate is 10:1; the temperature of the first vacuum drying is 40-50°C, and the time of the first vacuum drying is 10-12 h.

6. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, After obtaining the trialdehyde crosslinking agent, the process further includes: After heating the trialdehyde crosslinking agent with an acidified alcohol solution, a dialdehyde crosslinking agent is obtained through a third post-treatment. The mass ratio of the trialdehyde crosslinking agent to the acidified alcohol solution is 1:(10-20); the heating reaction temperature is 40-60℃, and the heating reaction time is 5-8h.

7. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 6, characterized in that, The specific steps of the third post-processing include: The heated reaction product was subjected to a fourth filtration and a fourth washing, followed by a second vacuum drying to obtain a dialdehyde crosslinking agent. The temperature of the second vacuum drying is 40~50℃, and the time of the second vacuum drying is 10~12h.

8. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, The mass ratio of the amination berberine, anhydrous ethanol, trialdehyde crosslinking agent and chitosan dissolved in the acidic aqueous solution is 1:(10~30):(2~3):(2~3). The addition of a trialdehyde crosslinking agent, followed by the addition of chitosan dissolved in an acidic aqueous solution, yields a composite antibacterial active substance. Specific steps include: A trialdehyde crosslinking agent was added to obtain a mixed solution. After the mixed solution underwent a first stirring reaction, chitosan dissolved in an acidic aqueous solution was added to undergo a second stirring reaction. The pH of the product from the second stirring reaction was adjusted to neutral, and then the mixture was subjected to a fifth filtration, a fifth washing, and a third vacuum drying to obtain a composite antibacterial active substance. The temperature of the first stirring reaction is 60-70℃, and the time of the first stirring reaction is 1-2 hours; the temperature of the second stirring reaction is 60-80℃, and the time of the second stirring reaction is 10-12 hours; the temperature of the third vacuum drying is 40-60℃, and the time of the third vacuum drying is 10-12 hours.

9. The method for preparing a broad-spectrum antibacterial food preservation film according to claim 1, characterized in that, The mass ratio of the composite antibacterial active substance, the second acidic aqueous solution, the second chitosan, the adhesive, and glycerin is 1:(50~100):(1~3):(1~3):(1~2). The second chitosan, adhesive, and glycerin are added sequentially to obtain a film-forming solution. This solution is then subjected to a slit-coating, segmented drying process to obtain a broad-spectrum antibacterial food preservation film. Specific steps include: After adding the second chitosan, a third stirring reaction is carried out. Then, an adhesive and glycerin are added to obtain a mixture. The mixture is then subjected to a fourth stirring reaction to obtain a film-forming liquid. The film-forming liquid is then subjected to a slit coating and segmented drying film-forming process, followed by pre-drying, drying, and cooling and shaping, to obtain a broad-spectrum antibacterial food preservation film. The adhesive includes one of gelatin, pectin, gum arabic, and xanthan gum; the third stirring reaction time is 30-60 min, and the fourth stirring reaction time is 4-6 h; the wet film thickness of the slit-type coating segmented drying film-forming process is 300-500 μm; the pre-drying temperature is 60-70℃, the pre-drying air velocity is 1.5-2 m / s, and the pre-drying time is 5-8 min; the drying temperature is 80-95℃, the drying air velocity is 2.5-3 m / s, and the drying time is 9-12 min; the cooling and setting temperature is 20-25℃, the cooling and setting air velocity is 0 m / s, and the cooling and setting time is 3-6 min.

10. A broad-spectrum antibacterial food preservation film, characterized in that, The preparation method of the broad-spectrum antibacterial food preservation film according to any one of claims 1-9 is obtained.

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