Preparation method and application of nano-emulsion bacteriostatic agent taking mango peel as material

Abstract

The invention discloses a preparation method and application of a nano-emulsion bacteriostatic agent with mango peel as a material, and belongs to the technical field of botanical pesticide preparations, the method comprises the following steps: drying and crushing the mango peel, and extracting with a first polar solvent to obtain a first crude extract; dissolving with a second polar solvent, adjusting the pH value to an isoelectric point, and carrying out ultrasonic-assisted extraction and standing layering to obtain an upper organic phase; removing a solvent to obtain a refined extract, and mixing the refined extract with an emulsifier and water to form a pre-emulsion; and carrying out high-speed shearing and high-pressure homogenization treatment to obtain the nano-emulsion bacteriostatic agent. The invention further provides application of the prepared nano emulsion bacteriostatic agent, the technical problems that an existing plant source bacteriostatic agent is low in active ingredient extraction efficiency, easy to degrade, poor in stability, not prone to uniform dispersion and the like are solved, efficient enrichment and stable encapsulation of the active ingredients are achieved through the integrated extraction, refining and nano emulsification technology, and the bacteriostatic agent has the advantages of being environmentally friendly, free of toxic and side effects and the like. Therefore, the antibacterial effect and the storage stability of the final product are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of plant-derived pesticide formulation technology, and in particular to a method for preparing and applying a nanoemulsion antibacterial agent using mango peel as a material. Background Technology

[0002] In agricultural production, the prevention and control of crop diseases is a crucial link in ensuring yield and quality. For a long time, chemically synthesized pesticides have been widely used due to their high efficiency and rapid effect. However, the resulting problems, such as pesticide residues, increased pathogen resistance, and environmental pressure, have become increasingly prominent. Therefore, developing efficient, low-toxicity, and environmentally friendly green alternative pesticide products has become an important research direction for sustainable agricultural development. Among these, the development of plant-derived pesticides using natural antibacterial active substances contained in plants has attracted widespread attention due to its potential advantages, including renewable resources, easy degradation, diverse mechanisms of action, and low likelihood of inducing resistance.

[0003] Mango peels, a significant byproduct of the mango processing industry, are typically discarded or used only for low-value purposes. Studies have shown that mango peels are rich in polyphenols, flavonoids, and other secondary metabolites, which have been proven to possess significant antioxidant and antibacterial activities. Therefore, developing mango peels into plant-derived antibacterial agents could not only provide a new source of material for crop protection but also achieve high-value utilization of agricultural waste, offering both economic and environmental benefits. However, converting the active ingredients in mango peels into practical agricultural antibacterial agents still faces a series of technical challenges. First, efficiently and selectively extracting the target antibacterial components from mango peels is not easy. Traditional extraction methods (such as simple soaking or decoction) often have limited extraction efficiency, and the resulting extracts are complex, containing large amounts of sugars, proteins, pigments, and other impurities, leading to relatively low levels of the target active ingredient and directly affecting the efficacy of subsequent formulations. Secondly, the active ingredients in plant extracts, especially polyphenols, generally suffer from chemical instability. They are prone to oxidation, polymerization, and other reactions and become inactive under the presence of light, heat, or oxygen. This poses a severe challenge to the shelf life of the products and the duration of their effectiveness in field applications.

[0004] More importantly, effectively dispersing hydrophobic plant extracts in a water-based application medium and ensuring their stable and uniform coverage of crop surfaces is a core challenge in formulation. Conventional formulations, such as wettable powders, emulsifiable concentrates, or ordinary emulsions, often fail to achieve uniform dispersion and stable suspension of active ingredients, easily leading to precipitation, layering, or oil phase separation. This not only affects the uniformity of application, resulting in poor control efficacy, but may also clog nozzles, causing inconvenience in application. Furthermore, larger particle or droplet sizes reduce the effective contact area between the agent and the target pathogen, potentially limiting the full expression of its biological activity.

[0005] Existing technologies have explored formulation improvements for plant extracts, such as microemulsions or regular emulsions. While these methods improve dispersibility to some extent, they may still present challenges such as insufficient long-term physical stability, slow degradation of active ingredients during storage, or the need for large amounts of organic solvents and surfactants. In particular, existing technologies are not yet fully developed and require further improvement and innovation to achieve a highly active, stable, and easy-to-use mango peel-derived antibacterial agent that addresses the challenges of multiple stages, from raw material processing, including extraction, purification, protection, and efficient delivery. Summary of the Invention

[0006] This invention overcomes the technical problems of existing plant-derived antibacterial agents, such as low extraction efficiency of active ingredients, easy degradation, poor stability, and difficulty in uniform dispersion. It provides a method for preparing a nanoemulsion antibacterial agent using mango peel as material and its application. By integrating extraction, purification and nanoemulsification technologies, it achieves efficient enrichment and stable encapsulation of active ingredients, thereby significantly improving the antibacterial effect and storage stability of the final product.

[0007] To achieve the above objectives, the present invention adopts the following solution: A method for preparing a nanoemulsion antibacterial agent using mango peel as a material includes the following steps: S1: The dried mango peel raw material is crushed and sieved to obtain mango peel powder. The mango peel powder is mixed with the first polar solvent in a certain proportion to form a first mixture. The first mixture is heated and refluxed to extract the first extract. S2: The first extract is filtered to separate the solid residue and obtain the first filtrate. The first filtrate is then subjected to vacuum distillation to remove the first polar solvent and obtain the first crude extract. S3: The first crude extract obtained is mixed with a second polar solvent and dissolved. The polarity of the second polar solvent is lower than that of the first polar solvent. Acid is added to the dissolved solution to adjust the pH value of the mixed solution to the isoelectric point range. Then, ultrasonic-assisted extraction is performed. The extracted mixed solution is allowed to stand to induce the formation of an upper organic phase containing the target antibacterial component and an aqueous phase containing impurities. The upper organic phase is separated and obtained. S4: The obtained upper organic phase is subjected to vacuum distillation to remove the second polar solvent, and a refined mango peel extract is obtained. The refined mango peel extract, emulsifier and distilled water are mixed in a predetermined ratio to form a pre-emulsion mixture. S5: The obtained pre-emulsion mixture is dispersed by high-speed shearing and then transferred to a high-pressure homogenizer. Homogenization is carried out under the set homogenization pressure and number of cycles to finally obtain the nanoemulsion antibacterial agent.

[0008] Preferably, in step S1, when the dried mango peel raw material is crushed and sieved to obtain mango peel powder, the particle size distribution of the mango peel powder after sieving is controlled so that the particle size of the powder is within a predetermined particle size range, specifically 80-200 mesh. The first polar solvent is an aqueous solution of ethanol and methanol with a volume concentration of 60%-90%. When mango peel powder is mixed with the first polar solvent in a certain proportion to form the first mixture, a step-by-step feeding and stepped heating program is used for heating and reflux extraction. First, a portion of the first polar solvent is mixed with all the mango peel powder at room temperature and stirred at low speed for pre-wetting. Then, the remaining first polar solvent is added. The first mixture is then heated to the first holding temperature at the first heating rate and held for a predetermined holding time. Next, the temperature is increased to a higher second holding temperature at the second heating rate for main reflux extraction. The second holding temperature is 70-90℃, and the main reflux extraction time is 1-3 hours. The entire heating and reflux extraction process is carried out in an inert gas environment.

[0009] Preferably, in step S2, when distilling the first filtrate under reduced pressure, a temperature-controlled reduced pressure distillation method is used, specifically including: The main portion of the first polar solvent is evaporated at the first distillation temperature and first vacuum. When the volume of the distillate is reduced to a predetermined proportion of the initial volume, the vacuum is simultaneously increased to a higher second vacuum, and the temperature is correspondingly increased to the second distillation temperature to continue distillation. Throughout the distillation process, the evaporated first polar solvent is recovered through a condenser, and the first filtrate is continuously stirred by a magnetic stirrer located at the bottom of the distillation flask. When the material in the distillation flask is observed to change from a flowing liquid to a viscous paste, heating is stopped and the vacuum is maintained. The remaining first polar solvent is removed using the residual heat of the system and continuous stirring to obtain the first crude extract.

[0010] Preferably, in step S3, the second polar solvent is ethyl acetate, dichloromethane, n-hexane or a mixture thereof. When adding acid to adjust the pH of the mixed solution, the acid used is an aqueous solution of at least one organic acid selected from citric acid, acetic acid or lactic acid, and the molar concentration of the acid is pre-prepared according to a predetermined value. During the process of adding acid drop by drop, the dropping speed is dynamically controlled according to the rate of decrease of the pH meter reading. When the pH value is close to the isoelectric point range, the dropping speed is slowed down and slow magnetic stirring is used to promote the overall homogeneity of the mixed solution. The isoelectric point range is between 3.5 and 5.0. After pH adjustment, let the mixed solution stand and observe its clarity. If new fine flocs appear, restart gentle stirring and add a small amount of acid until the flocs are completely dissolved and the pH value stabilizes again within the isoelectric point range. Then, perform ultrasonic-assisted extraction.

[0011] Preferably, in step S3, after adding acid to adjust the pH of the mixed solution to the isoelectric point range, ultrasonic-assisted extraction is performed. The ultrasonic treatment is carried out in an ice-water bath container, and a probe-type ultrasonic generator is directly inserted into the mixed solution. The ultrasonic mode is set to pulse mode, with the pulse working time and pulse interval time alternating. During the pulse interval time, the temperature is controlled to allow the mixed solution to briefly return to near room temperature. During the pulse working time, the mixed solution is lowered back to the set temperature of the ice-water bath. During the extraction process, inert gas is continuously introduced into the surface of the mixed solution to remove oxygen; the extracted mixed solution is transferred to a constant temperature shaker and shaken at a slow speed, and the standing time is extended until the mixed solution is completely separated and the interface is clear; the upper organic phase is obtained by separating the mixed solution after standing using a separation funnel pre-wetted with a second polar solvent, so as to reduce the adsorption loss of the upper organic phase on the funnel wall.

[0012] Preferably, in step S4, when mixing the refined mango peel extract, emulsifier, and distilled water in a predetermined ratio, the refined mango peel extract and emulsifier are first mixed evenly in a preheated container to form an oil phase mixture; at the same time, the distilled water is heated to the same predetermined temperature as the oil phase mixture, the predetermined temperature being 50-70℃; then, under constant temperature and continuous stirring conditions, the preheated distilled water is slowly added to the oil phase mixture in batches, first adding 30%-50% of the distilled water and stirring at high speed to form a preliminary uniform viscous paste, then adding all the remaining distilled water, and switching to medium speed stirring until a uniform pre-emulsion mixture is formed.

[0013] Preferably, when uniformly mixing the refined mango peel extract and emulsifier in a preheated container to form an oil phase mixture, the emulsifier is first preheated to above its phase transition temperature and kept in a liquid state. Then, it is mixed with the refined mango peel extract in an inert gas environment. During the mixing process, a constant-temperature container with a wall-scraping stirrer is used. When the preheated distilled water is slowly added to the oil phase mixture in batches, the flow rate of the added distilled water is controlled by a metering pump. When a portion of distilled water is added for the first time, the distilled water is evenly sprayed onto the surface of the continuously stirred oil phase mixture in the form of an atomized spray, and the droplet diameter of the spray is controlled within a predetermined range. After a preliminary uniform viscous paste is formed, the remaining distilled water is added by injecting it in a laminar flow manner through a narrow conduit submerged in the paste liquid surface. At the same time, the stirring speed is gradually reduced from high speed to medium speed, and the circulating water temperature of the constant-temperature container jacket is kept constant until there are no visible oil or water phase aggregates in the pre-emulsion mixture, forming a uniform pre-emulsion mixture.

[0014] Preferably, in step S5, when the pre-emulsion mixture is subjected to high-speed shear dispersion and then transferred to a high-pressure homogenizer for homogenization, a segmented stepped homogenization pressure program is used, specifically including: First, the material is homogenized for the first number of cycles under an initial homogenization pressure. Then, the homogenization pressure is gradually increased to a higher target homogenization pressure, and the remaining homogenization cycles are performed under the target homogenization pressure. The initial homogenization pressure is 30-60 MPa, the target homogenization pressure is 100-150 MPa, and the total number of cycles is 6-10. The entire homogenization process is carried out in a high-pressure homogenizer with an external circulating cooling jacket, and the material temperature at the homogenizer outlet is controlled to be maintained below a predetermined temperature. After the last homogenization cycle is completed, the obtained nanoemulsion antibacterial agent is immediately transferred to a sealed container that has been pre-cooled to the same temperature range for collection and storage.

[0015] Preferably, during the process of gradually increasing the homogenization pressure from the initial homogenization pressure to the target homogenization pressure, a continuously adjustable pressure control system is used to linearly increase the pressure from the initial homogenization pressure to the target homogenization pressure at a predetermined, gradual rate. During this linear pressure increase, the high-pressure homogenizer maintains the homogenization process, but the opening of the homogenization valve is synchronously fine-tuned according to the pressure increase to maintain a stable shear rate. At the same time, by monitoring the material temperature at the homogenizer outlet and the feedback from the pressure sensor in real time, the flow rate and temperature of the coolant in the external circulating cooling jacket are dynamically adjusted to ensure that the material temperature is always maintained below the predetermined temperature of 40°C during the pressure increase. Once the pressure reaches the target homogenization pressure, maintain that pressure for a predetermined period of stable homogenization, and then perform the remaining homogenization cycles. After all homogenization cycles are completed, when transferring the nanoemulsion antibacterial agent into the pre-cooled sealed container, control the flow rate of the transfer pipeline to a speed limit through a flow valve to avoid further damage to the emulsion structure by shear force. During the transfer process, the pre-cooled sealed container is kept under negative pressure.

[0016] This application also provides the application of nanoemulsion antibacterial agents, and the application of crop protection products prepared with nanoemulsions as components, wherein the nanoemulsion antibacterial agents are obtained by any of the preparation methods described above.

[0017] The present invention has at least the following beneficial effects: (1) It constructs a systematic process from extraction, purification to nanoemulsification, with each step closely connected. The extraction step provides basic raw materials for purification, the purification step provides high-purity active ingredients for emulsification, and the nanoemulsification step transforms the results of the previous steps into a stable and efficient dosage form. The synergistic design overcomes the limitations of single-step improvement, so that the final nanoemulsion has a comprehensive improvement in active ingredient content, formulation stability and antibacterial function; (2) By increasing the contact area through crushing and sieving, and using a specific polar solvent for heating and reflux extraction, the antibacterial components in mango peel are efficiently dissolved. The liquid-liquid extraction technology based on pH adjustment to the isoelectric point is used to effectively separate and enrich the target antibacterial substances by utilizing the distribution differences between the target components and impurities in different pH and solvents, thereby significantly improving the purity and specific activity of the purified extract; (3) By pre-forming a homogeneous oil phase with the purified extract and emulsifier, and By controlling the temperature and feeding method, the aqueous phase is introduced and initially dispersed in a stable and uniform manner, effectively preventing local demulsification or phase separation, and forming a pre-emulsion with uniform microstructure and suitable viscosity; (4) High-pressure homogenization technology is used, especially through optimized pressure program and temperature control, the pre-emulsion is efficiently broken into an emulsion with an average particle size at the nanoscale. The nanoscale droplets not only provide a huge specific surface area, which is conducive to their contact and interaction with the target, but also obtain a high absolute value of Zeta potential through process control, which enhances the electrostatic repulsion between droplets, so that the final product has both excellent physical stability and potential higher bioavailability; (5) The mango peel nano-emulsion antibacterial agent prepared by the method of the present invention has strong antibacterial activity, good storage stability, and is easy to use. It is very suitable for direct application as a crop protection product or as an active ingredient in related preparations, solving the main bottleneck of traditional plant extracts in dosage form application. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the principle of the method of the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] like Figure 1 As shown, the preparation method of the nanoemulsion antibacterial agent using mango peel as material provided by the present invention includes the following steps: S1: The dried mango peel raw material is crushed and sieved to obtain mango peel powder. The mango peel powder is mixed with a first polar solvent in a certain proportion to form a first mixture. The first mixture is heated and refluxed to extract the first extract.

[0021] Crushing increases the specific surface area of ​​the raw material, facilitating contact between the solvent and the active ingredients. Sieving controls the particle size distribution of the powder, ensuring it falls within a suitable particle size range. For example, a sieve between 80 and 200 mesh can be used to guarantee extraction efficiency and uniformity in subsequent processing. Mango peel powder is mixed with a first polar solvent in a specific ratio to form a first mixture. This first polar solvent is typically a medium-to-high polar solvent such as water, ethanol, or methanol, which dissolves the polar antibacterial components in the mango peel, such as polyphenols and flavonoids. Reflux extraction promotes the dissolution and diffusion of the target components by increasing the temperature. The reflux device prevents solvent evaporation and loss, improving extraction efficiency and component recovery. The entire extraction process can be carried out in a conventional glass reflux apparatus. The heating temperature can be set according to the solvent's boiling point. For example, if using an ethanol-water mixture, reflux can be performed in the range of 70°C to 85°C, with an extraction time of 1 to 3 hours to ensure complete extraction.

[0022] S2: Filter the obtained first extract to separate the solid residue and obtain the first filtrate. Distill the first filtrate under reduced pressure to remove the first polar solvent and obtain the first crude extract.

[0023] Filtration can be achieved using filter paper, a Buchner funnel, or centrifugation to remove undissolved solid particles and impurities. Subsequent vacuum distillation removes the first polar solvent. This process lowers the solvent's boiling point by reducing system pressure, allowing for solvent evaporation at a lower temperature, which helps protect the heat-sensitive active ingredients from degradation. Vacuum distillation can be performed in a rotary evaporator, setting appropriate vacuum levels (e.g., 0.05 MPa to 0.09 MPa) and temperatures (e.g., 40°C to 60°C) until a viscous or solid first crude extract is obtained. The extract is then preliminarily concentrated to increase the concentration of the target components, preparing the solution for subsequent purification.

[0024] S3: The first crude extract obtained is mixed with a second polar solvent and dissolved. The polarity of the second polar solvent is lower than that of the first polar solvent. Acid is added to the dissolved solution to adjust the pH value of the mixed solution to the isoelectric point range. Then, ultrasonic-assisted extraction is performed. The extracted mixed solution is allowed to stand to induce the formation of an upper organic phase containing the target antibacterial component and an aqueous phase containing impurities. The upper organic phase is separated and obtained.

[0025] The second polar solvent is less polar than the first polar solvent; examples include ethyl acetate, dichloromethane, and n-hexane. It selectively dissolves the target antibacterial component using the principle of "like dissolves like," while simultaneously separating it from some highly polar impurities. The pH is adjusted to the isoelectric point range so that certain amphoteric substances (such as proteins and certain phenolic acids) have the lowest solubility at a specific pH, thus promoting their transfer from the aqueous phase to the organic phase. The added acid can be an organic acid such as citric acid or acetic acid; it should be added slowly with stirring to ensure uniform pH changes. Ultrasonic-assisted extraction utilizes the cavitation effect and mechanical vibration generated by ultrasound to accelerate the release of components from the solid or liquid phase into the organic phase, improving extraction efficiency and selectivity. After settling, the system separates into two layers: the upper organic phase is rich in the target antibacterial component, and the lower aqueous phase contains most polar impurities. The purified organic phase can be obtained by separation.

[0026] S4: The obtained upper organic phase is subjected to vacuum distillation to remove the second polar solvent, resulting in a refined mango peel extract. The refined mango peel extract, emulsifier, and distilled water are mixed in a predetermined ratio to form a pre-emulsion mixture.

[0027] The purpose of this step is to recover high-purity extracts and completely remove residual organic solvents. The refined extract, emulsifier, and distilled water are then mixed in a predetermined ratio to form a pre-emulsion mixture. The emulsifier reduces the oil-water interfacial tension, helping the hydrophobic extract components disperse in the water and forming a preliminary emulsion system. During mixing, the oil phase (extract and emulsifier) ​​can be prepared first, followed by gradual addition of the aqueous phase, with stirring to ensure initial homogenization. The formation of the pre-emulsion mixture is fundamental to subsequent nanoemulsification, and its homogeneity directly affects the stability and particle size distribution of the final emulsion.

[0028] S5: The obtained pre-emulsion mixture is dispersed by high-speed shearing and then transferred to a high-pressure homogenizer. Homogenization is carried out under the set homogenization pressure and number of cycles to finally obtain the nanoemulsion antibacterial agent.

[0029] The droplet size is initially reduced using high-shear equipment (such as a high-speed homogenizer) to form a micron-sized emulsion. It is then transferred to a high-pressure homogenizer for homogenization at a set pressure (e.g., 50 MPa to 150 MPa) and cycle number (e.g., 3 to 10 times). High-pressure homogenization further breaks down the emulsion droplets to the nanoscale (typically below 100 nm) through intense shearing, impact, and cavitation, forming a uniform and stable nanoemulsion antibacterial agent. Cooling measures can be used throughout the process to control the temperature and prevent overheating that could lead to component degradation or emulsion demulsification.

[0030] Compared with existing methods for preparing plant-derived antibacterial agents, this method achieves efficient and selective extraction of antibacterial active ingredients from mango peel through a multi-step synergistic process, ultimately preparing them into a nanoemulsion formulation. In the extraction stage, polar solvents and reflux processes improve extraction efficiency; in the purification stage, pH adjustment and ultrasound-assisted extraction enhance the purity and selectivity of the target components; and in the formulation preparation stage, high-pressure homogenization technology yields nanoemulsions with fine particle size and uniform distribution, significantly improving the dispersibility, stability, and bioavailability of the antibacterial components. Compared to traditional crude extracts or ordinary emulsion systems, the nanoemulsion antibacterial agent prepared by this method exhibits significant improvements in storage stability, adhesion to target surfaces, and persistence of antibacterial action, making it suitable for crop protection applications in the agricultural field.

[0031] To further verify and demonstrate the benefits of the above preparation method, the following experimental scheme was designed, including an example that strictly follows this method, and three comparative examples for comparing key steps.

[0032] 1. Raw materials and general conditions: Raw materials: dried mango peels from the same batch, crushed and passed through an 80-mesh sieve, mixed evenly and set aside.

[0033] First polar solvent: 70% aqueous ethanol solution.

[0034] Second polar solvent: ethyl acetate.

[0035] Emulsifier: Tween 80.

[0036] Target pathogens: Staphylococcus aureus (Gram-positive representative) and Escherichia coli (Gram-negative representative).

[0037] Key test indicators: yield, content of key active ingredient (mangiferin), emulsion particle size and stability, and minimum inhibitory concentration (MIC).

[0038] 2. Grouping and preparation methods: 1) Embodiment 1 of this application: The preparation of nanoemulsion antibacterial agents strictly follows all steps S1-S5 of the above method, including: S1: Take 100g of processed mango peel powder, mix it with 1000mL of 70% ethanol, and reflux at 85℃ for 2 hours.

[0039] S2: Filter the extract, concentrate the filtrate under reduced pressure at 50°C to a paste, and obtain the first crude extract.

[0040] S3: Dissolve the first crude extract in ethyl acetate, adjust the pH to 4.0 with 1 mol / L citric acid solution, and extract by sonication (400W, pulse mode) for 20 minutes in an ice-water bath. After standing and separating the layers, take the upper organic phase.

[0041] S4: The organic phase was concentrated under reduced pressure to obtain a refined extract. 1g of the refined extract was mixed with 2g of Tween 80 at 60°C to form an oil phase. 17g of distilled water was preheated to 60°C, then 1 / 3 of the distilled water was added first, and the mixture was homogenized at high speed (10000rpm, 2min) to form a paste. The remaining distilled water was then added, and the mixture was stirred at medium speed to form a pre-emulsion.

[0042] S5: The pre-emulsion is first homogenized twice at 50MPa using a high-pressure homogenizer, and then homogenized six times at 120MPa. The discharge temperature is controlled to be <40℃ throughout the process to obtain a nano-emulsion.

[0043] 2) Comparative Example 1 (Aqueous dispersion of traditional extract): Using a traditional crude extraction process without refining or nano-sizing: only steps S1 and S2 of Example 1 of this application are performed to obtain a first crude extract. Take the crude extract with an amount of active material equivalent to that in Example 1, add a small amount of ethanol to aid dissolution, and then dilute with distilled water to the same volume as the final emulsion in Example 1. Shake vigorously to prepare an aqueous dispersion of the crude extract.

[0044] 3) Comparative Example 2 (Refined Extract Conventional Emulsion): To evaluate the purification effect, but with a different emulsification method: Steps S1-S4 of Example 1 were performed to obtain the exact same purified extract. This purified extract was directly mixed with the same proportion of Tween 80 and water, and emulsified using only a high-speed dispersion homogenizer (10,000 rpm, 10 min) without high-pressure homogenization to obtain a conventional emulsion.

[0045] 4) Comparative Example 3 (Commercially available chemical antibacterial agent control): Choose a commonly used chemical antibacterial agent as the market benchmark: select 80% mancozeb wettable powder and prepare a dispersion according to the recommended concentration.

[0046] 3. Comparison of data and results: The test data for the key indicators in the above experiments are shown in Table 1 below: Table 1 In Table 1: MIC values ​​are concentrations calculated based on the active ingredient (dry weight of mango peel extract or mancozeb active ingredient). Particle size change rate = [(particle size after 14 days - initial particle size) / initial particle size] × 100%. N / A indicates that this indicator is not applicable or cannot be accurately measured.

[0047] By comparing the data in Table 1 above horizontally and vertically, it is clear that: Compared to Comparative Example 1, the yield of the purified extract in Examples 1 and 2 (approximately 5.2%) was much lower than that of the crude extract (approximately 18.5%), but the content of the key active ingredient mangiferin was significantly enriched. This indicates that step S3 (pH adjustment and ultrasound-assisted extraction) effectively removed a large number of inactive impurities, achieving the purification of the active ingredient.

[0048] Regarding particle size and uniformity, the average particle size of Example 1 (162.3 nm) is much smaller than that of Comparative Example 2 (846.7 nm), and the PDI (0.151) is much lower than that of Comparative Example 2 (0.423), indicating that the high-pressure homogenization process (S5) achieves a nanoscale emulsion system with highly uniform distribution.

[0049] Regarding physical stability, the absolute value of the Zeta potential in Example 1 (38.5 mV) was higher than that in Comparative Example 2 (25.6 mV), indicating stronger electrostatic repulsion stability. This was also verified in actual accelerated experiments: the particle size of Example 1 increased only slightly (+5.1%), and its appearance remained essentially unchanged; while the particle size of Comparative Example 2 increased significantly (+45.8%) and emulsification occurred. This demonstrates that nano-sizing and the corresponding processes greatly improve the storage stability of the product.

[0050] Overall, in terms of core antibacterial activity, Example 1 showed the lowest MIC values ​​against both test bacteria among all groups, demonstrating significantly superior antibacterial efficacy compared to traditional crude extracts (Comparative Example 1) and conventional emulsions (Comparative Example 2). It also outperformed commercially available chemical agents (Comparative Example 3) in these indicators. The reason for the difference in effect in Example 1 is that, compared to Comparative Example 1, the superiority of Example 1 stems from the enrichment of active ingredients resulting from the purification step and the high dispersibility and bioavailability brought about by nano-emulsification. Compared to Comparative Example 2, the superiority of Example 1 is mainly attributed to the nano-emulsification process. Nanoscale droplets provide a larger contact surface area, enhancing the interaction with bacterial cell membranes, thereby significantly amplifying the bioactivity of the same purified extract. In summary, this technical solution is not a simple superposition of steps, but rather an organic combination of "efficient extraction - selective purification - nanoscale delivery," producing a synergistic enhancement effect. It not only achieves a qualitative improvement in physicochemical properties, but more importantly, it amplifies the antibacterial function of natural mango peel extract to a level comparable to or even better than some chemical agents, while also possessing better stability, fully verifying its technological advancement and application potential as a highly efficient and stable crop protection product.

[0051] In another technical solution, in step S1, when the dried mango peel raw material is crushed and sieved to obtain mango peel powder, the particle size distribution of the mango peel powder after sieving is controlled so that the particle size of the powder is within a predetermined particle size range, specifically 80-200 mesh. The first polar solvent is an aqueous solution of ethanol and methanol with a volume concentration of 60%-90%. When mango peel powder is mixed with the first polar solvent in a certain proportion to form the first mixture, a step-by-step feeding and stepped heating program is used for heating and reflux extraction. First, a portion of the first polar solvent is mixed with all the mango peel powder at room temperature and stirred at low speed for pre-wetting. Then, the remaining first polar solvent is added. The first mixture is then heated to the first holding temperature at the first heating rate and held for a predetermined holding time. Next, the temperature is increased to a higher second holding temperature at the second heating rate for main reflux extraction. The second holding temperature is 70-90℃, and the main reflux extraction time is 1-3 hours. The entire heating and reflux extraction process is carried out in an inert gas environment.

[0052] When crushing and sieving dried mango peel raw materials, the particle size distribution of the powder should be controlled within a predetermined range. For example, the majority of the powder can be distributed between 80 and 200 mesh. Excessively large particle sizes can lead to difficulties in solvent penetration and component dissolution, reducing extraction efficiency; excessively fine particle sizes may cause agglomeration or filter blockage in subsequent processing due to excessive surface area, and may also result in the loss of some heat-sensitive or easily oxidized components due to over-crushing. By controlling the particle size within a suitable range, sufficient specific surface area can be ensured to facilitate solvent contact while avoiding process problems caused by excessively fine powder. In practice, standard sieves of different mesh sizes can be used for combined sieving, collecting the powder of the intermediate particle size range for subsequent extraction. First, a portion of the first polar solvent is mixed with all the mango peel powder at room temperature and pre-wetted with low-speed stirring. This step allows the solvent to initially wet the powder particles, expelling air between the particles to ensure sufficient contact later. The pre-wetting time can be from several minutes to half an hour. Subsequently, the remaining first polar solvent is added to form the final first mixture. The heating process employs a stepped procedure: First, the mixture is heated to a first holding temperature at a first heating rate, for example, 2°C to 5°C per minute. This temperature can be set within the range of 10°C to 20°C below the solvent's major boiling point and maintained for a period of time for preliminary extraction. Then, at a second heating rate, typically slightly lower than or equal to the first heating rate, the temperature is further increased to a higher second holding temperature, which is close to or reaches the solvent's reflux temperature, for main reflux extraction. This stepped heating method avoids the rapid decomposition of certain heat-sensitive components due to sudden high temperatures and allows components with different solubility properties to dissolve gradually in stages, contributing to improved extraction comprehensiveness and component stability.

[0053] The entire heating reflux extraction process is conducted in an inert gas environment, such as by continuously introducing nitrogen or argon into the reflux device. Many effective antibacterial components in mango peel, such as polyphenols, are easily oxidized by oxygen in the air, leading to decreased activity or changes in color and properties. An inert gas environment effectively removes oxygen from the device, creating a low-oxygen or anaerobic extraction atmosphere, thereby maximizing the protection of the chemical structure and biological activity of these easily oxidized components. Operationally, an inert gas inlet pipe and an outlet bubbling device can be connected to the upper end of the reflux condenser to ensure sufficient gas replacement.

[0054] This method achieves refined control over the initial extraction steps through the synergistic effects of particle size control, stepwise feeding and stepped heating, and inert gas protection. Compared to the simple reflux method of crushing and then feeding the material all at once and heating it directly to boiling, this method can extract the target antibacterial components from mango peel more gently and efficiently. Particle size control creates the basic conditions for uniform and efficient extraction; stepwise feeding and stepped heating reduce thermal shock and promote the gradual and complete dissolution of components; while inert gas protection significantly inhibits the oxidative degradation of active ingredients during extraction. These measures work together to improve the yield, purity, and stability of the final refined extract, providing a better raw material basis for the preparation of high-performance nanoemulsion antibacterial agents.

[0055] In another technical solution, in step S2, when the first filtrate is subjected to vacuum distillation, a programmed temperature-controlled vacuum distillation method is used, specifically including: The main portion of the first polar solvent is evaporated at the first distillation temperature and first vacuum. When the volume of the distillate is reduced to a predetermined proportion of the initial volume, the vacuum is simultaneously increased to a higher second vacuum, and the temperature is correspondingly increased to the second distillation temperature to continue distillation. Throughout the distillation process, the evaporated first polar solvent is recovered through a condenser, and the first filtrate is continuously stirred by a magnetic stirrer located at the bottom of the distillation flask. When the material in the distillation flask is observed to change from a flowing liquid to a viscous paste, heating is stopped and the vacuum is maintained. The remaining first polar solvent is removed using the residual heat of the system and continuous stirring to obtain the first crude extract.

[0056] The temperature-controlled vacuum distillation method does not involve distillation at a single, constant vacuum level and temperature. Instead, it dynamically adjusts process parameters based on changes in the material state and solvent evaporation characteristics during distillation. In the initial stages of distillation, the solvent content in the filtrate is high, making evaporation relatively easy. Therefore, a relatively low vacuum level and temperature can be used for a smooth start-up. As the solvent continues to evaporate, the remaining material gradually thickens, and the solvent volatility decreases. At this point, increasing the vacuum level and temperature can overcome mass transfer resistance, effectively removing residual solvent while preventing the decomposition of heat-sensitive components in the crude extract due to localized overheating.

[0057] First, distillation is carried out at a first distillation temperature and a first vacuum level to evaporate the main portion of the first polar solvent. For example, the first distillation temperature can be set between 40°C and 50°C, and the first vacuum level can be set between 0.07 MPa and 0.085 MPa. When the liquid volume in the distillation flask is observed or measured to have decreased to a predetermined percentage of the initial volume, such as 30% to 50% of the initial volume, the second stage begins. At this time, the system vacuum level is simultaneously increased to a higher second vacuum level, such as 0.09 MPa to 0.095 MPa, and the temperature is correspondingly increased to a second distillation temperature, such as 50°C to 60°C, to continue distillation. This parameter switching can adapt to changes in the viscosity of the material, ensuring effective solvent removal even in later stages. Throughout the distillation process, the distilled solvent is recovered through a condenser for recycling or environmentally friendly treatment. A magnetic stirrer located at the bottom of the distillation flask continuously stirs the filtrate, which prevents coking due to localized overheating and promotes uniform heat and mass transfer. Stirring is crucial for maintaining heat and mass transfer efficiency, especially when the liquid thickens. When the material in the flask changes from a free-flowing liquid to a viscous paste, it indicates that most of the solvent has been removed. At this point, external heating is stopped, but the system is kept under high vacuum. Using the residual heat of the distillation system and continuous stirring, the remaining trace amounts of solvent in the paste are further removed. This method, utilizing residual heat for final drying, is gentler than continuous heating, helps protect the quality of the crude extract, and prevents overheating.

[0058] Compared to conventional, fixed-parameter vacuum distillation, the programmed temperature-controlled vacuum distillation method used in this study embodies a more intelligent and adaptable control strategy. By adjusting the vacuum level and temperature in stages, solvent removal is more efficient, shortening the distillation time. Simultaneously, utilizing residual heat and continuous stirring in the later stages reduces the risk of thermal damage to heat-sensitive crude extract components. Continuous stirring ensures uniform heating of the material, avoiding component degradation or charring caused by localized overheating. Therefore, this method is expected to yield higher quality first crude extracts with more complete retention of active ingredients, lower solvent residue, and potentially better color and physical properties.

[0059] In another technical solution, in step S3, the second polar solvent is ethyl acetate, dichloromethane, n-hexane or a mixture thereof. When adding acid to adjust the pH of the mixed solution, the acid used is an aqueous solution of at least one organic acid selected from citric acid, acetic acid or lactic acid, and the molar concentration of the acid is pre-prepared according to a predetermined value. During the process of adding acid drop by drop, the dropping speed is dynamically controlled according to the rate of decrease of the pH meter reading. When the pH value is close to the isoelectric point range, the dropping speed is slowed down and slow magnetic stirring is used to promote the overall homogeneity of the mixed solution. The isoelectric point range is between 3.5 and 5.0. After pH adjustment, let the mixed solution stand and observe its clarity. If new fine flocs appear, restart gentle stirring and add a small amount of acid until the flocs are completely dissolved and the pH value stabilizes again within the isoelectric point range. Then, perform ultrasonic-assisted extraction.

[0060] The acid used is an aqueous solution of at least one organic acid selected from citric acid, acetic acid, or lactic acid, rather than a strong inorganic acid. Organic acids are relatively mild, with moderate acidity, and are less likely to cause hydrolysis or drastic chemical changes in certain active ingredients (such as some polyphenols or esters) during pH adjustment. Furthermore, their anions may have minimal interference with the system. The molar concentration of the acid solution needs to be pre-prepared according to a predetermined value, for example, a concentration range of 0.1 mol / L to 1.0 mol / L. Pre-preparing a standard concentration of acid solution enables quantitative and repeatable pH adjustment, avoiding the risk of localized acidity imbalance caused by directly using concentrated acid. In practice, the approximate amount of acid solution required can be calculated based on the target pH range and the volume of the mixed solution, and a freshly prepared acid solution of suitable concentration can be prepared for use. When adding the acid solution dropwise to the mixed solution of the second polar solvent and water containing the first crude extract, a constant dropping rate is not used; instead, the rate of drop is dynamically controlled based on the real-time rate of decrease in the pH meter reading. In pH regions far from the isoelectric point, the solution's buffering capacity may be weak, and the pH value may change rapidly. In this case, the dropping rate can be appropriately increased. However, when the pH value approaches the target isoelectric point range (for example, the isoelectric point may correspond to a narrow range of pH 3.5 to 5.0), the solution's buffering capacity may increase, and the pH value becomes very sensitive to small amounts of added acid. In this case, the dropping rate must be significantly slowed down, for example, adjusted to one drop per second or even slower, to prevent the pH value from exceeding the target range. Throughout the dropping process, slow magnetic stirring should be used to ensure that the added acid is quickly and evenly dispersed throughout the mixed solution, avoiding localized excessively low pH levels. This achieves a smooth and uniform decrease in the overall pH value, accurately reaching the preset isoelectric point range.

[0061] After initial pH adjustment, the next step of ultrasonic extraction is not performed immediately. Instead, the mixed solution is allowed to stand for a short time to observe changes in clarity. When the pH value is precisely at or very close to the isoelectric point of certain amphoteric substances, these substances may aggregate to form fine flocs, causing slight turbidity in the solution. If new flocs are observed, it indicates that pH adjustment may have induced the target component to begin agglomeration, but the system is not yet fully stable. At this point, gentle magnetic stirring should be restarted, and a small amount of acid of the same concentration should be added. The purpose of adding acid is to further fine-tune the pH or to provide a sufficient ionic environment to promote complete dissolution of the flocs to form a stable colloid or complete transfer to the organic phase. By cycling through adjustment-observation-fine-tuning until the solution becomes clear again or the flocs disappear, and the pH meter reading stabilizes within the predetermined isoelectric point range, the pH adjustment step can be considered successfully completed. Compared to simply using any acid and adjusting the pH at a fixed rate, this method achieves highly precise and stable control of the pH value of the mixed solution through precise control of the acid properties, concentration, and adjustment process. Using mild organic acids reduces the risk of chemical damage to active ingredients; dynamic control of the dropping rate combined with continuous stirring effectively prevents localized over-acidity and pH over-adjustment, ensuring that the target component reaches its isoelectric point uniformly and smoothly; and post-adjustment observation and necessary fine-tuning further guarantee the physicochemical stability of the system at the isoelectric point. This significantly improves the selectivity and efficiency of subsequent phase separation steps (i.e., enrichment of the target component into the organic phase), reduces the possibility of active ingredients being lost in the aqueous phase or forming difficult-to-handle intermediate flocs due to improper pH control, thereby helping to improve the purity and recovery rate of the refined extract.

[0062] In step S3, after adding acid to adjust the pH of the mixed solution to the isoelectric point range, ultrasonic-assisted extraction is performed. The ultrasonic treatment is carried out in an ice-water bath container, and a probe-type ultrasonic generator is directly inserted into the mixed solution. The ultrasonic mode is set to pulse mode, with the pulse working time and pulse interval time alternating. During the pulse interval time, the temperature is controlled to allow the mixed solution to briefly return to near room temperature. During the pulse working time, the mixed solution is lowered back to the set temperature of the ice-water bath. During the extraction process, inert gas is continuously introduced into the surface of the mixed solution to remove oxygen; the extracted mixed solution is transferred to a constant temperature shaker and shaken at a slow speed, and the standing time is extended until the mixed solution is completely separated and the interface is clear; the upper organic phase is obtained by separating the mixed solution after standing using a separation funnel pre-wetted with a second polar solvent, so as to reduce the adsorption loss of the upper organic phase on the funnel wall.

[0063] During ultrasonic treatment, the container holding the mixed solution must be placed in an ice-water bath. The cavitation effect and mechanical action of ultrasound generate a large amount of heat, which may cause the system temperature to rise rapidly, threatening the stability of the heat-sensitive antibacterial components in the mango peel extract. The ice-water bath effectively absorbs and dissipates this heat, keeping the temperature during the ultrasonic process at a low level, for example, between 5°C and 15°C. The ultrasonic equipment used is a probe-type ultrasonic generator, whose probe is directly inserted into the solution, resulting in more direct energy transfer and higher efficiency than water bath ultrasound. The ultrasonic mode is set to pulse mode, alternating between active (e.g., 2-5 seconds of ultrasound) and intermittent (e.g., 3-8 seconds of pause). During the pulse interval, the applied ultrasonic energy is stopped, allowing the mixed solution to briefly recover to near room temperature (but still confined to a low temperature range by the ice-water bath), which helps alleviate the accumulation of localized instantaneous high temperatures caused by continuous ultrasound. During the pulse active period, energy is reapplied for extraction. This mode further reduces the thermal load on the material while ensuring extraction efficiency.

[0064] During ultrasonic extraction, an inert gas (such as nitrogen or argon) is continuously introduced into the space above the liquid surface of the mixed solution to remove oxygen from the container and create an inert atmosphere. This is because after pH adjustment, the target components in the system may be in a more easily oxidized state (e.g., the phenolic anion form of phenolic substances), and the free radicals generated by ultrasound may also exacerbate the oxidation reaction. Inert gas protection can effectively inhibit the occurrence of these oxidation side reactions and protect the activity of the antibacterial components. After ultrasonic extraction, the resulting mixed solution is transferred to a constant-temperature shaker and shaken at a gentle, slow speed. The shaking time can be appropriately extended depending on the system conditions, for example, shaking for 10 to 30 minutes. Shaking can promote the collision, aggregation, and growth of tiny droplets, accelerating the phase separation process. Subsequently, a long settling period is allowed, which can be extended to several hours or even overnight, to ensure that the organic phase and aqueous phase are completely and thoroughly separated, and that the interface between the two phases is very clear and flat. Sufficient settling is key to obtaining a high-purity organic phase. A separatory funnel is used to separate the fully settled and layered mixed solution. The separatory funnel is pre-wetted with a second polar solvent (i.e., the solvent used for the upper organic phase to be collected later). This pre-saturates the active adsorption sites on the funnel wall, reducing non-specific adsorption losses of the target component on the glass surface. After pouring the mixed solution into the pre-wetted separatory funnel, the lower aqueous phase is separated using standard methods, and then the upper organic phase is collected. This pre-wetting treatment effectively reduces the significant losses caused by adsorption on the container wall for organic phases rich in trace amounts of highly active components, thereby improving the overall recovery rate of the target antibacterial component.

[0065] By combining an ice-water bath with pulsed ultrasound, the advantages of ultrasound-enhanced extraction are fully utilized while significantly suppressing the damage of thermal effects to active ingredients. Inert gas protection provides an antioxidant barrier throughout the extraction process, maintaining the chemical integrity of the components. Extended oscillation and settling times ensure sufficient and thorough phase separation. Simple solvent pre-wetting of the separation funnel cleverly reduces adsorption losses during separation. These interconnected measures work together to achieve highly efficient extraction while simultaneously providing excellent component protection and purification. Compared to conventional room-temperature ultrasound and simple settling separation, this method yields a refined mango peel extract with higher activity, lower oxidation levels, and higher purity, while also improving the yield of valuable extracts.

[0066] In another technical solution, in step S4, when mixing the refined mango peel extract, emulsifier, and distilled water in a predetermined ratio, the refined mango peel extract and emulsifier are first mixed evenly in a preheated container to form an oil phase mixture; at the same time, the distilled water is heated to the same predetermined temperature as the oil phase mixture, the predetermined temperature being 50-70℃; then, under constant temperature and continuous stirring conditions, the preheated distilled water is slowly added to the oil phase mixture in batches, first adding 30%-50% of the distilled water and stirring at high speed to form a preliminary uniform viscous paste, then adding all the remaining distilled water, and switching to medium speed stirring until a uniform pre-emulsion mixture is formed.

[0067] The refined mango peel extract and emulsifier are uniformly mixed in a preheated container to form an oil-phase mixture. This oil-phase mixture is essentially a homogeneous hydrophobic or lipophilic core composed of the active ingredient (extract) and the surfactant (emulsifier). The emulsifier can be a nonionic surfactant such as Span or Tween, or a mixture thereof, which acts to encapsulate the extract particles or droplets, reducing their surface energy. Mixing in a preheated container means heating the mixture to a specific temperature, for example, between 50°C and 70°C. This helps reduce the viscosity of the oil-phase mixture, improving its fluidity, and may also promote better dissolution or dispersion of certain solid or semi-solid extract components in the emulsifier. Simultaneously, the required amount of distilled water is heated in another container to the same predetermined temperature as the oil-phase mixture. Preheating the distilled water reduces the temperature difference between the oil and water phases during mixing, avoiding changes in emulsifier properties due to sudden temperature changes (such as the cloud point phenomenon of some nonionic emulsifiers) or drastic changes in local viscosity, thus facilitating the contact and fusion of the two phases under mild thermodynamic conditions.

[0068] Under constant temperature conditions, such as by using a water bath or jacket to maintain the container containing the oil phase mixture at the predetermined temperature, and with continuous stirring, preheated distilled water is slowly added in batches. The first portion of distilled water is added, which can be one-third to one-half of the total water volume. Simultaneously with the addition of this water, high-speed stirring is employed; the stirring speed can be set according to the equipment size, for example, within the range of 1000 rpm to 3000 rpm. The strong shear force of high-speed stirring rapidly breaks the added water into tiny droplets, causing initial emulsification with the oil phase mixture. Due to the relatively small initial water volume and the relatively high concentration of oil phase and emulsifier, the system quickly forms a uniform, viscous paste. This paste can be considered a highly concentrated water-in-oil or liquid crystal precursor, in which the aqueous phase is fully dispersed and encapsulated within a continuous oil phase or surfactant matrix. The formation of this uniform, viscous paste indicates that the aqueous phase has been initially and stably introduced into the system. After obtaining the initially uniform, viscous paste, the remaining preheated distilled water is added. At this point, since the system already has a good emulsified base (i.e., a viscous paste), continued stirring can further disperse the remaining aqueous phase. The stirring speed can then be switched to a medium speed, such as 500 rpm to 1500 rpm, to avoid excessive shear force introducing too many air bubbles or causing excessive damage to the already formed emulsion structure when the system has been initially emulsified. Under continuous stirring at a medium speed, the viscous paste is gradually diluted, eventually transforming into a uniform, moderately fluid, milky white or pale yellow emulsion mixture—the pre-emulsion mixture. Maintaining a constant temperature throughout the mixing process is crucial. This ensures that the emulsifier remains within its optimal activity temperature range, maintaining stable interfacial tension, which is conducive to the formation of relatively concentrated emulsion droplets.

[0069] Compared to the simple method of directly mixing all components at once, the stepwise, temperature-controlled mixing strategy significantly improves the control precision and emulsification effect of the pre-emulsion formation process. Preheating eliminates the adverse effects of temperature gradients, creating a stable thermodynamic environment for emulsification. First, a high internal ratio viscous paste is formed with a small amount of water, essentially establishing a highly stable emulsion "seed" or template. This step forces the emulsifier and oil phase to fully function at a limited interface, ensuring the sufficiency and uniformity of the initial emulsification. Subsequent dilution to the final ratio allows the emulsion structure to expand smoothly, avoiding the risks of insufficient local emulsifier concentration, oil phase aggregation, or demulsification caused by adding a large amount of water at once. Therefore, the pre-emulsion mixture prepared by this method has better homogeneity, a more stable microstructure, and a narrower initial droplet size distribution. This provides a higher-quality, more homogeneous feedstock for the subsequent high-pressure homogenization process to efficiently break it down into nanoemulsions, thus contributing to the final obtaining a nanoemulsion antibacterial agent with better stability and superior performance.

[0070] When the refined mango peel extract and emulsifier are uniformly mixed in a preheated container to form an oil phase mixture, the emulsifier is first preheated to above its phase transition temperature and kept in a liquid state. Then, it is mixed with the refined mango peel extract in an inert gas environment. During the mixing process, a constant-temperature container with a scraper stirrer is used. When the preheated distilled water is slowly added to the oil phase mixture in batches, the flow rate of the distilled water is controlled by a metering pump. When a portion of distilled water is added for the first time, it is sprayed evenly onto the surface of the continuously stirred oil phase mixture in the form of atomized spray, and the droplet diameter of the spray is controlled within a predetermined range. After a preliminary uniform viscous paste is formed, the remaining distilled water is added by injecting it in a laminar flow manner through a narrow conduit submerged in the paste liquid surface. At the same time, the stirring speed is gradually reduced from high speed to medium speed, and the circulating water temperature in the jacket of the constant-temperature container is kept constant until there are no visible oil or water phase aggregates in the pre-emulsion mixture, forming a uniform pre-emulsion mixture.

[0071] Before mixing the emulsifier with the refined mango peel extract, the emulsifier is preheated separately to above its phase transition temperature and kept in a liquid state. Many nonionic emulsifiers have a phase transition temperature (PIT), near which their hydrophilic-lipophilic balance changes significantly. Heating it above the PIT (e.g., for some polyoxyethylene ether emulsifiers, the PIT may be between 70°C and 85°C) ensures that it exists in a completely homogeneous liquid form with optimal flowability and spreadability, allowing for faster and more thorough encapsulation or dissolution of the extract components when mixed with it. The mixing operation is carried out in an inert gas environment (such as nitrogen), which prevents oxidation of the oils or active ingredients at high temperatures. The mixing vessel used is a thermostatic container equipped with a scraper agitator. The scraper agitator continuously scrapes away any viscous material that may adhere to the inner wall of the container, ensuring completely uniform heat and mass transfer without dead zones, which is crucial for maintaining a high degree of homogeneity in the oil-phase mixture.

[0072] When adding preheated distilled water in batches, the flow rate is precisely controlled using a metering pump, for example, at a rate of 1% to 5% of the total water volume per minute. The initial addition of distilled water is achieved through atomization. Specifically, the distilled water is dispersed into numerous tiny droplets through an atomizing nozzle and then uniformly sprayed onto the surface of the continuously stirred oil-phase mixture. The diameter of the spray droplets is carefully controlled, for example, within the range of 50 to 150 micrometers. This atomization significantly increases the interfacial area of ​​the initial contact between the aqueous and oil phases, and the small droplets gently fall onto the surface of the vortex formed by vigorous stirring, allowing for rapid capture and entrainment, thus achieving instantaneous and uniform dispersion of the aqueous phase. This is more effective than directly pouring or injecting a stream of water in preventing localized agglomeration of the aqueous phase, promoting mixing at the micrometer level and even smaller from the outset.

[0073] After a preliminary uniform viscous paste is formed through atomized spraying, the remaining distilled water is added slowly via a laminar flow through a narrow conduit submerged in the paste. Laminar flow injection is characterized by smooth fluid flow without violent disturbances, which avoids introducing large eddies or shear into the already formed fine emulsion structure, preventing structural damage. Simultaneously, the stirring speed is gradually reduced from high to medium. This gradual reduction helps the system smoothly transition from high-shear structure building to medium-shear maintenance and refinement. Throughout the process, the jacketed circulating water temperature of the thermostatic container is kept constant, for example, maintained at the previously set preheating temperature. Through continuous stirring and precise temperature control, the system gradually transforms from a viscous paste into a homogeneous pre-emulsion mixture until no visible oil or water phase aggregates remain, exhibiting a completely uniform opalescent appearance.

[0074] By preheating the emulsifier to above its phase transition temperature, its emulsifying potential is fully realized. An inert gas environment and a scraper-type agitator ensure high homogeneity and oxidation prevention during mixing. The initial addition of liquid using a combination of metering pumps and atomized spray achieves excellent dispersion and gentle introduction of the aqueous phase. Subsequent laminar flow injection, coupled with precise adjustment of the stirring speed, allows for stable dilution based on the established fine structure, maximizing the protection of the formed emulsion system. This series of highly synergistic technical features makes the preparation process of the pre-emulsion mixture extremely controllable, resulting in a pre-emulsion with exceptionally excellent homogeneity and microstructural stability, achieving a high degree of integration between the oil and water phases. This top-tier pre-emulsion quality allows the subsequent high-pressure homogenization process to focus more on further nano-sizing the already very fine droplets, rather than correcting macroscopic inhomogeneities, thereby significantly improving the efficiency of high-pressure homogenization.

[0075] In another technical solution, in step S5, when the pre-emulsion mixture is subjected to high-speed shear dispersion and then transferred to a high-pressure homogenizer for homogenization, a segmented stepped homogenization pressure program is used, specifically including: First, the material is homogenized for the first number of cycles under an initial homogenization pressure. Then, the homogenization pressure is gradually increased to a higher target homogenization pressure, and the remaining homogenization cycles are performed under the target homogenization pressure. The initial homogenization pressure is 30-60 MPa, the target homogenization pressure is 100-150 MPa, and the total number of cycles is 6-10. The entire homogenization process is carried out in a high-pressure homogenizer with an external circulating cooling jacket, and the material temperature at the homogenizer outlet is controlled to be maintained below a predetermined temperature. After the last homogenization cycle is completed, the obtained nanoemulsion antibacterial agent is immediately transferred to a sealed container that has been pre-cooled to the same temperature range for collection and storage.

[0076] This approach abandons the conventional practice of multiple cycles under a single constant pressure, instead employing a staged pressure application strategy. Specifically, the pre-emulsion material is first homogenized under a relatively low initial homogenization pressure for the first number of cycles. This initial pressure can be set within a moderate range, such as 30 MPa to 50 MPa. The purpose of this stage is to perform preliminary crushing and homogenization of the material, allowing the system to adapt to the high-pressure environment and avoiding uncontrollable demulsification or excessive heating caused by directly applying extremely high pressure, which could result in the emulsion structure being subjected to excessive shear stress instantaneously. After completing the cycle at the initial pressure (e.g., 2 to 4 cycles), the homogenization pressure is then increased stepwise to a higher target homogenization pressure. The target pressure is typically the high pressure necessary to achieve nanoscale particle sizes, and can be set in the range of 100 MPa to 150 MPa or even higher. Subsequently, the remaining number of cycles (e.g., 4 to 8 more cycles) are performed at the target pressure to ultimately refine the droplets to the nanoscale and ensure their uniform distribution. This step-by-step process, starting with lower droplets and gradually increasing their size, makes the fragmentation of emulsion droplets smoother and more progressive, which is conducive to the formation of more stable nanoemulsion structures with a more concentrated particle size distribution.

[0077] High-pressure homogenization, especially with multiple cycles under high pressure, generates significant heat due to intense shearing, collision, and cavitation, causing a rapid rise in material temperature. Excessive temperature can not only cause emulsifier denaturation and decreased emulsion physical stability but also seriously threaten the activity of heat-sensitive antibacterial components in mango peel. Therefore, the homogenization process in this scheme is carried out in a high-pressure homogenizer with an external circulating cooling jacket. During operation, the cooling system is pre-activated to maintain the coolant (usually water or an aqueous ethylene glycol solution) in the jacket at a low temperature, such as 5°C to 15°C. Throughout the homogenization process, the material temperature at the homogenizer outlet is monitored in real time, and efforts are made to control the outlet temperature below a predetermined safe range by adjusting the coolant flow rate and temperature, for example, maintaining it below 40°C or even lower. Effective cooling can remove the heat generated during homogenization in a timely manner, providing a relatively low-temperature environment for the entire high-pressure process, which is crucial for ensuring the bioactivity and physical stability of the final product. After the final homogenization cycle, the newly formed nanoemulsion antibacterial agent may still be warmer than ambient temperature and its structure may be in a "fresh" but relatively fragile state. Immediately transfer the material to a pre-cooled, sealed container (e.g., 5°C to 15°C, close to the target discharge temperature) for collection and storage. This hot-material-cold-receive method offers several advantages: firstly, it quickly stops the accumulation of residual heat in pipelines or equipment; secondly, the pre-cooled container walls further help cool the emulsion, allowing it to quickly pass through potentially unstable temperature ranges; and thirdly, the sealed environment prevents solvent evaporation and external contamination. Immediate transfer and cryogenic storage lock in the optimal nanostructure created by high-pressure homogenization, preserving the initial properties of the emulsion to the greatest extent possible.

[0078] Compared to traditional constant high-pressure homogenization processes, the segmented, stepped pressure program combined with active temperature control demonstrates a more refined and scientific control over the nanoemulsion formation process. The stepped pressure increase reduces the risk of demulsification and structural defects caused by single high-shear impacts, making the droplet fragmentation process gentler and more efficient, contributing to the acquisition of nanoemulsions with smaller particle sizes and narrower distributions. The continuous active cooling effectively mitigates the inherent thermal effects of high-pressure homogenization, significantly reducing damage to heat-sensitive active ingredients and improving the product's bioactivity retention. Finally, timely low-temperature collection further consolidates the aforementioned process achievements. Overall, the nanoemulsion antibacterial agent prepared by this method exhibits significant improvements in microstructure uniformity, physical stability, and the retention rate of active ingredients.

[0079] During the process of gradually increasing the homogenization pressure from the initial homogenization pressure to the target homogenization pressure, a continuously adjustable pressure control system is adopted to linearly increase the pressure from the initial homogenization pressure to the target homogenization pressure at a predetermined, gradual rate. During this linear pressure increase, the high-pressure homogenizer maintains the homogenization process, but the opening of the homogenization valve is synchronously fine-tuned according to the pressure increase to maintain a stable shear rate. At the same time, by monitoring the material temperature at the homogenizer outlet in real time and the feedback from the pressure sensor, the flow rate and temperature of the coolant in the external circulating cooling jacket are dynamically adjusted to ensure that the material temperature is always maintained below the predetermined temperature of 40°C during the pressure increase. Once the pressure reaches the target homogenization pressure, maintain that pressure for a predetermined period of stable homogenization, and then perform the remaining homogenization cycles. After all homogenization cycles are completed, when transferring the nanoemulsion antibacterial agent into the pre-cooled sealed container, control the flow rate of the transfer pipeline to a speed limit through a flow valve to avoid further damage to the emulsion structure by shear force. During the transfer process, the pre-cooled sealed container is kept under negative pressure.

[0080] The dynamic process of pressure increasing from the initial value to the target value is not a simple step-like jump, but rather employs a continuously adjustable pressure control system to ensure that the pressure increases linearly at a predetermined, gradual rate. For example, the pressure can be set to rise uniformly and continuously from the initial homogenizing pressure to the target homogenizing pressure at a rate of 0.5 MPa to 2 MPa per second. During this linear pressurization period, the high-pressure homogenizer does not stop working but continues to perform homogenization. The opening of the homogenizing valve is synchronously fine-tuned according to the pressure increase, and maintaining a stable shear rate is crucial for the uniform breakup of droplets. As the system pressure increases linearly, if the valve core gap (opening) is not adjusted, the flow velocity and shear force field through the valve gap will change nonlinearly. By fine-tuning the opening, the effects of pressure changes can be compensated, thereby maintaining a relatively constant and intense shear flow field throughout the pressurization process. This ensures that the mechanical action on the material is smoothly enhanced, which is conducive to the formation of more uniform nanodroplets and avoids the widening of the particle size distribution caused by abrupt changes in shear force.

[0081] As the pressure increases linearly, the flow rate and temperature of the coolant in the external circulating cooling jacket are dynamically adjusted by real-time monitoring of the material temperature at the homogenizer outlet and feedback signals from the pressure sensor. For example, when an upward trend in the outlet temperature is detected or the pressure enters a high-level range, the coolant flow rate can be automatically increased or its set temperature can be decreased. This dynamic adjustment enables immediate response and counteraction to the heat generation process, ensuring that even during the most intense heat generation phase, the material temperature can be firmly controlled within a predetermined safe range (e.g., below 40°C). This temperature control strategy, combining feedforward and feedback, is more precise and effective than simple fixed cooling, providing optimal thermal management for high-pressure homogenization processes.

[0082] Once the target homogenization pressure is reached, cycle counting does not begin immediately. Instead, the pressure is maintained for a predetermined period of stable homogenization, such as 15 to 60 seconds. This brief pressure plateau allows the system to fully homogenize under the highest shear force field, ensuring all materials undergo sufficiently intense and high-level homogenization. The remaining cycles are then performed for formal homogenization. After all homogenization cycles are complete, additional safeguards are taken when transferring the nanoemulsion product to a pre-cooled, sealed container: the flow rate in the transfer pipeline is strictly controlled via flow valves, limiting it to a low velocity limit (e.g., below a threshold that could generate significant additional shear force). This is to prevent the high-speed flowing emulsion from being subjected to strong shear forces again at pipe bends and valves during transfer, which could damage the newly formed, delicate, and fragile nanoemulsion structure. Simultaneously, maintaining a slight negative pressure in the pre-cooled, sealed container during transfer allows for smooth product intake using the pressure differential, further reducing the potential adverse effects of mechanical actions such as pumping. The high-pressure homogenization nanoemulsification process upgrades the control of multiple key parameters such as pressure, shear, and temperature from static settings to dynamic, interconnected, and smoothly transitioning precision control. The combination of linear pressure boosting and fine-tuning of the homogenizing valve achieves a smooth enhancement of the shear force field, resulting in extremely uniform droplet breakup and producing nanoemulsions with excellent monodispersity. Dynamic temperature control minimizes the risk of thermal damage. Furthermore, the control of flow rate and negative pressure during the final product transfer stage ensures that the nanostructures are protected from the moment they leave the homogenizer until they are stored. In summary, by implementing this highly integrated and refined control scheme, the prepared nanoemulsion antibacterial agent is expected to achieve excellent levels of uniformity in particle size distribution, thermodynamic stability of the system, and encapsulation and protection efficiency of active ingredients, strongly guaranteeing product quality and reproducibility.

[0083] This application also provides the application of nanoemulsion antibacterial agents, and the application of crop protection products prepared with nanoemulsions as components, wherein the nanoemulsion antibacterial agents are obtained by any of the preparation methods described above.

[0084] The nanoemulsion antibacterial agent obtained by the preparation method provided in this application has been fully verified in the above schemes as a highly efficient and stable crop protection product, demonstrating its technological advancement and application potential. Based on its excellent antibacterial activity, nanoscale particle size, good stability, and environmentally friendly properties, the nanoemulsion antibacterial agent prepared in this application can be widely used in the agricultural field, especially as an active ingredient in crop protection products. Specific usage methods include at least the following: Direct application: The obtained nanoemulsion antibacterial agent can be diluted with water at a certain ratio (e.g., 500-2000 times) and sprayed directly and evenly onto the leaves, stems, or fruit surfaces of crops using a spraying device. It is suitable for controlling plant diseases caused by bacteria or some fungi, such as citrus canker, tomato bacterial spot, and pepper scab. Spraying can be carried out at the early stage of disease occurrence or as a preventative measure.

[0085] As a component in the preparation of compound formulations: This nanoemulsion antibacterial agent can be used as a core active ingredient in compound formulations with other compatible pesticide adjuvants (such as dispersants, stabilizers, and binders), chemical pesticides, or other natural extract antibacterial agents. It can be processed into formulations that are easy to store and use, for example: Soluble solution (SL): Use directly or after slight dilution.

[0086] Emulsion (EW): Further emulsified with other oil or water phase components.

[0087] Microencapsulated suspensions (CS): further enhance their duration of action and sustained-release properties through encapsulation technology.

[0088] Seed treatment suspension (FS): Used for seed dressing to prevent seed-borne or soil-borne diseases.

[0089] The nanoemulsion antibacterial agent provided in this application has the following application advantages: The nanoparticle size significantly improves the contact area and penetration efficiency between the active ingredient and pathogens, as shown in Table 1. Its minimum inhibitory concentration (MIC) is significantly lower than that of traditional extracts and some chemical agents. The main raw material is derived from agricultural waste, mango peel, reducing the amount of chemically synthesized pesticides used and the risk of residues. The nanoemulsion system exhibits good physical and chemical stability, is easy to store and transport, and has a long shelf life. It can be diluted with water in any proportion and is compatible with conventional application equipment.

[0090] In practical applications, the optimal concentration, application time, and application frequency can be determined through field trials based on the target crop, disease type, and severity of occurrence, in order to achieve the best control effect while taking into account both economic and ecological benefits.

[0091] It should be noted that although the steps are described in a specific order above, this does not mean that they must be performed in that order. In fact, some of these steps can be executed concurrently, or even in a different order, as long as the required functionality is achieved. The number of devices and processing scale described herein are for simplification of the invention; applications, modifications, and variations of this invention will be readily apparent to those skilled in the art.

[0092] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a nanoemulsion antibacterial agent using mango peel as a material, characterized in that, Includes the following steps: S1: The dried mango peel raw material is crushed and sieved to obtain mango peel powder. The mango peel powder is mixed with the first polar solvent in a certain proportion to form a first mixture. The first mixture is heated and refluxed to extract the first extract. S2: The first extract is filtered to separate the solid residue and obtain the first filtrate. The first filtrate is then subjected to vacuum distillation to remove the first polar solvent and obtain the first crude extract. S3: The first crude extract obtained is mixed with a second polar solvent and dissolved. The polarity of the second polar solvent is lower than that of the first polar solvent. Acid is added to the dissolved solution to adjust the pH value of the mixed solution to the isoelectric point range. Then, ultrasonic-assisted extraction is performed. The extracted mixed solution is allowed to stand to induce the formation of an upper organic phase containing the target antibacterial component and an aqueous phase containing impurities. The upper organic phase is separated and obtained. S4: The obtained upper organic phase is subjected to vacuum distillation to remove the second polar solvent, and a refined mango peel extract is obtained. The refined mango peel extract, emulsifier and distilled water are mixed in a predetermined ratio to form a pre-emulsion mixture. S5: The obtained pre-emulsion mixture is dispersed by high-speed shearing and then transferred to a high-pressure homogenizer. Homogenization is carried out under the set homogenization pressure and number of cycles to finally obtain the nanoemulsion antibacterial agent.

2. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 1, characterized in that, In step S1, when the dried mango peel raw material is crushed and sieved to obtain mango peel powder, the particle size distribution of the mango peel powder after sieving is controlled so that the particle size of the powder is within a predetermined particle size range, specifically 80-200 mesh. The first polar solvent is an aqueous solution of ethanol and methanol with a volume concentration of 60%-90%. When mango peel powder is mixed with the first polar solvent in a certain proportion to form the first mixture, a step-by-step feeding and stepped heating program is used for heating and reflux extraction. First, a portion of the first polar solvent is mixed with all the mango peel powder at room temperature and stirred at low speed for pre-wetting. Then, the remaining first polar solvent is added. The first mixture is then heated to the first holding temperature at the first heating rate and held for a predetermined holding time. Next, the temperature is increased to a higher second holding temperature at the second heating rate for main reflux extraction. The second holding temperature is 70-90℃, and the main reflux extraction time is 1-3 hours. The entire heating and reflux extraction process is carried out in an inert gas environment.

3. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 1, characterized in that, In step S2, when the first filtrate is subjected to vacuum distillation, a programmed temperature-controlled vacuum distillation method is used, specifically including: The main portion of the first polar solvent is evaporated at the first distillation temperature and first vacuum. When the volume of the distillate is reduced to a predetermined proportion of the initial volume, the vacuum is simultaneously increased to a higher second vacuum, and the temperature is correspondingly increased to the second distillation temperature to continue distillation. Throughout the distillation process, the evaporated first polar solvent is recovered through a condenser, and the first filtrate is continuously stirred by a magnetic stirrer located at the bottom of the distillation flask. When the material in the distillation flask is observed to change from a flowing liquid to a viscous paste, heating is stopped and the vacuum is maintained. The remaining first polar solvent is removed using the residual heat of the system and continuous stirring to obtain the first crude extract.

4. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 1, characterized in that, In step S3, the second polar solvent is ethyl acetate, dichloromethane, n-hexane or a mixture thereof. When adding acid to adjust the pH of the mixed solution, the acid used is an aqueous solution of at least one organic acid selected from citric acid, acetic acid or lactic acid, and the molar concentration of the acid is pre-prepared according to a predetermined value. During the process of adding acid drop by drop, the dropping speed is dynamically controlled according to the rate of decrease of the pH meter reading. When the pH value is close to the isoelectric point range, the dropping speed is slowed down and slow magnetic stirring is used to promote the overall homogeneity of the mixed solution. The isoelectric point range is between 3.5 and 5.

0. After pH adjustment, let the mixed solution stand and observe its clarity. If new fine flocs appear, restart gentle stirring and add a small amount of acid until the flocs are completely dissolved and the pH value stabilizes again within the isoelectric point range. Then, perform ultrasonic-assisted extraction.

5. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 4, characterized in that, In step S3, after adding acid to adjust the pH of the mixed solution to the isoelectric point range, ultrasonic-assisted extraction is performed. The ultrasonic treatment is carried out in an ice-water bath container, and a probe-type ultrasonic generator is directly inserted into the mixed solution. The ultrasonic mode is set to pulse mode, with the pulse working time and pulse interval time alternating. During the pulse interval time, the temperature is controlled to allow the mixed solution to briefly return to near room temperature. During the pulse working time, the mixed solution is lowered back to the set temperature of the ice-water bath. During the extraction process, inert gas is continuously introduced into the surface of the mixed solution to remove oxygen; the extracted mixed solution is transferred to a constant temperature shaker and shaken at a slow speed, and the standing time is extended until the mixed solution is completely separated and the interface is clear; the upper organic phase is obtained by separating the mixed solution after standing using a separation funnel pre-wetted with a second polar solvent, so as to reduce the adsorption loss of the upper organic phase on the funnel wall.

6. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 1, characterized in that, In step S4, when mixing the refined mango peel extract, emulsifier, and distilled water in a predetermined ratio, the refined mango peel extract and emulsifier are first mixed evenly in a preheated container to form an oil phase mixture. At the same time, the distilled water is heated to the same predetermined temperature as the oil phase mixture, which is 50-70°C. Then, under constant temperature and continuous stirring conditions, the preheated distilled water is slowly added to the oil phase mixture in batches. First, 30%-50% of the distilled water is added and stirred at high speed to form a preliminary uniform viscous paste. Then, the remaining distilled water is added, and the stirring speed is switched to medium until a uniform pre-emulsion mixture is formed.

7. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 6, characterized in that, When the refined mango peel extract and emulsifier are uniformly mixed in a preheated container to form an oil phase mixture, the emulsifier is first preheated to above its phase transition temperature and kept in a liquid state. Then, it is mixed with the refined mango peel extract in an inert gas environment. During the mixing process, a constant-temperature container with a scraper stirrer is used. When the preheated distilled water is slowly added to the oil phase mixture in batches, the flow rate of the distilled water is controlled by a metering pump. When a portion of distilled water is added for the first time, it is sprayed evenly onto the surface of the continuously stirred oil phase mixture in the form of atomized spray, and the droplet diameter of the spray is controlled within a predetermined range. After a preliminary uniform viscous paste is formed, the remaining distilled water is added by injecting it in a laminar flow manner through a narrow conduit submerged in the paste liquid surface. At the same time, the stirring speed is gradually reduced from high speed to medium speed, and the circulating water temperature in the jacket of the constant-temperature container is kept constant until there are no visible oil or water phase aggregates in the pre-emulsion mixture, forming a uniform pre-emulsion mixture.

8. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 1, characterized in that, In step S5, when the pre-emulsion mixture is subjected to high-speed shear dispersion and then transferred to a high-pressure homogenizer for homogenization, a segmented stepped homogenization pressure program is used, specifically including: First, the material is homogenized for the first number of cycles under an initial homogenization pressure. Then, the homogenization pressure is gradually increased to a higher target homogenization pressure, and the remaining homogenization cycles are performed under the target homogenization pressure. The initial homogenization pressure is 30-60 MPa, the target homogenization pressure is 100-150 MPa, and the total number of cycles is 6-10. The entire homogenization process is carried out in a high-pressure homogenizer with an external circulating cooling jacket, and the material temperature at the homogenizer outlet is controlled to be maintained below a predetermined temperature. After the last homogenization cycle is completed, the obtained nanoemulsion antibacterial agent is immediately transferred to a sealed container that has been pre-cooled to the same temperature range for collection and storage.

9. The method for preparing the nanoemulsion antibacterial agent using mango peel as material according to claim 8, characterized in that, During the process of gradually increasing the homogenization pressure from the initial homogenization pressure to the target homogenization pressure, a continuously adjustable pressure control system is adopted to linearly increase the pressure from the initial homogenization pressure to the target homogenization pressure at a predetermined, gradual rate. During this linear pressure increase, the high-pressure homogenizer maintains the homogenization process, but the opening of the homogenization valve is synchronously fine-tuned according to the pressure increase to maintain a stable shear rate. At the same time, by monitoring the material temperature at the homogenizer outlet in real time and the feedback from the pressure sensor, the flow rate and temperature of the coolant in the external circulating cooling jacket are dynamically adjusted to ensure that the material temperature is always maintained below the predetermined temperature of 40°C during the pressure increase. Once the pressure reaches the target homogenization pressure, maintain that pressure for a predetermined period of stable homogenization, and then perform the remaining homogenization cycles. After all homogenization cycles are completed, when transferring the nanoemulsion antibacterial agent into the pre-cooled sealed container, control the flow rate of the transfer pipeline to a speed limit through a flow valve to avoid further damage to the emulsion structure by shear force. During the transfer process, the pre-cooled sealed container is kept under negative pressure.

10. The application of the nanoemulsion antibacterial agent obtained by the preparation method according to any one of claims 1 to 9 and the crop protection products prepared using it as a component.

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