Chitosan composite Lipu taro starch nanoparticles as well as preparation method and application thereof

Abstract

The invention relates to the technical field of starch, in particular to chitosan composite Lipu taro starch nanoparticles as well as a preparation method and application thereof. The Lipu taro nano-starch composite chitosan particles (CH / LSNPs) with smaller particle size and stronger hydrophobicity are prepared through a composite method of an anti-solvent precipitation method and an electrostatic composite chitosan method, so that the Lipu taro nano-starch composite chitosan particles have good emulsifying activity and emulsifying stability. The method is a green composite modification method, the hydrophobicity of the Lipu taro starch is enhanced while the particle size of the Lipu taro starch is reduced, and the hydrophobic chitosan composite Lipu taro starch nanoparticles are prepared. The colocasia esculenta nanometer starch composite chitosan particles can be used for preparing Pickering emulsion, and the prepared emulsion has higher emulsion stability compared with the Lipu colocasia esculenta nanometer starch Pickering emulsion and the Lipu colocasia esculenta nanometer starch Pickering emulsion.

Description

Technical Field

[0001] The present application relates to the technical field of starch, and specifically to a chitosan composite Lipu taro starch nanoparticle and its preparation method and application Background Art

[0002] The starch content in Lipu taro is extremely rich, reaching more than 85% of the dry matter, which is the main component of Lipu taro and has very high development and utilization value. Lipu taro starch has functional characteristics such as small particle size and good water and oil retention stability, and has multi-dimensional potential as an emulsifier, stabilizer and fat substitute in the food industry, and is considered a low-cost option for the food industry. Compared with the research on the emulsifying properties of starch, food science researchers have conducted more extensive research on the processing properties of starch such as gel properties, gelatinization properties and digestion properties. However, at present, due to the safety, non-allergenicity, rich source and low cost of starch particles, researchers have begun to conduct in-depth research on the emulsifying properties of starch, and starch particles as stabilizers of emulsions have become a hot research field. Mechanistically, starch particles seem to have two main ways to act as emulsifiers in emulsions. On the one hand, starch particles can adsorb on the oil-water interface, generating a surface layer loaded with particles and forming a steric barrier to protect the droplets. On the other hand, when the starch particle concentration in the system is high enough, the particles may generate a structural barrier in the form of a particle network in the continuous phase between the dispersed droplets. The two mechanisms usually assist in stabilizing the starch-based emulsion system. Improving the emulsifying properties of starch to make it a better stabilizer can be achieved by reducing its particle size or increasing its hydrophobicity in two ways

[0003] At present, a variety of methods for preparing starch nanoparticles and starch nanocrystals have been explored, which are roughly divided into acid hydrolysis method, enzymatic hydrolysis method, mechanical method, ultrasonic method and antisolvent precipitation method. The acid hydrolysis method has problems such as the large use of chemical reagents and too low product recovery rate; the SNP obtained by the mechanical treatment method usually has a large particle size; the antisolvent precipitation method will use highly diluted starch solutions and a large amount of solvents, which is not conducive to improving production efficiency and reducing costs

[0004] For enhancing the hydrophobicity of starch particles, the most commonly used methods are dry heat treatment and chemical modification. Dry heat treatment has a limited effect on the hydrophobicity of native starch

[0005] Therefore, finding a more green and safe modification method that can enhance the emulsifying properties of LTS is the current key research object Summary of the Invention

[0006] In order to solve the above technical problems existing in the prior art, the present application provides a chitosan composite Lipu taro starch nanoparticle and its preparation method and application

[0007] A preparation method of chitosan composite Lipu taro starch nanoparticles, characterized by specifically comprising the following steps:

[0008] (1) Preparation of Lipu taro starch: Grind Lipu taro in a plant tissue crusher; Screen the obtained slurry, and then sediment the filtrate in an ice bath; After sedimentation, pour off the upper-layer purplish-red liquid, and re-suspend the precipitate in distilled water; Adjust the pH of the mixture to 10 by adding NaOH solution, and continuously stir (for about 2 hours); Subsequently, neutralize to pH 7 with HCl solution, centrifuge, remove the supernatant, and scrape off the upper-layer yellow impurities to collect the precipitate; Re-suspend the precipitate in distilled water and centrifuge; Finally, dry the precipitate, grind it into powder, pass it through a 120-mesh sieve, store the starch in a sample bag, and code the obtained powder as LTS for subsequent analysis;

[0009] (2) Preparation of Lipu taro nano-starch particles: Prepare a starch suspension, and continuously stir in a boiling water bath until the starch is completely gelatinized; After gelatinization, the starch is ultrasonically treated and then gradually added dropwise to an ethanol solution under continuous stirring to prepare Lipu taro starch nanoparticles LSNPs by anti-solvent precipitation method; After the solution is stirred and centrifuged, discard the supernatant to obtain LSNPs; Wash the LSNPs with absolute ethanol to remove excess water, and freeze-dry to obtain dry LSNPs;

[0010] (3) Preparation of Lipu taro starch nanoparticle composite chitosan: Dissolve chitosan (CH) in acetic acid solution, stir overnight at room temperature to ensure complete dissolution, and prepare a 1wt% chitosan solution; Dissolve LSNPs in distilled water, and continuously stir magnetically until completely dispersed to form an LSNPs stock solution; Subsequently, add the chitosan solution to the LSNPs stock solution to adjust the pH, and continuously stir magnetically to form a mixed solution of LSNPs:CH.

[0011] Further, in the step (1), when grinding Lipu taro in a plant tissue crusher, specifically, grind it with distilled water at a solid-liquid ratio of 1:3 for 2 minutes.

[0012] Further, the screening in the step (1) is sequentially through 60-mesh and 120-mesh sieves.

[0013] Further, the sedimentation in the step (1) is for 12 hours to prevent deterioration.

[0014] Further, in the step (1), when re-suspending the precipitate in distilled water, specifically, re-suspend the precipitate in distilled water at a solid-liquid ratio of 1:3.

[0015] Further, in the step (1), the concentration of the NaOH solution is 1mol / L; the concentration of the HCl solution is 1mol / L.

[0016] Further, the centrifugation in step (1) is specifically centrifugation at 1200×g for 15 minutes.

[0017] Further, the drying in step (1) is drying at 45°C for 48 hours.

[0018] Further, the step of "re-stirring the precipitated substance in distilled water and centrifuging" in step (1) is repeated at least 3 times to ensure that the supernatant is clear and there are no obvious impurities on the upper layer of the precipitate.

[0019] Further, the centrifugation after stirring the solution in step (2) is specifically that the solution is stirred at room temperature for 10 min and then centrifuged at 8000 rpm for 10 min.

[0020] Further, the LSNPs in step (2) are washed with absolute ethanol to remove excessive water, and dried LSNPs are obtained after lyophilization. Specifically, the LSNPs are washed with absolute ethanol at least 3 times to remove excessive water, pre-frozen at -18°C for 12 h, and then vacuum lyophilized for 48 h to obtain dried LSNPs.

[0021] Further, the acetic acid solution in step (3) is a 1% (v / v) acetic acid solution.

[0022] A chitosan composite Lipu taro starch nanoparticle is prepared by the above method. It can be used in the preparation of emulsions, especially in the preparation of Pickering emulsions.

[0023] A Pickering emulsion of chitosan composite starch nanoparticles is prepared by using the above chitosan composite Lipu taro starch nanoparticles.

[0024] The specific preparation method is as follows:

[0025] The volume of the sunflower seed oil phase is 20% - 70%; under the condition of the compounding of CH and LSNPs with a pH of 2 - 8, according to the ratio of LSNPs:CH = 1:(0 - 0.2), a dispersion liquid with a particle concentration of CH / LSNPs of 1% - 6% is prepared, and is homogenously mixed with the oil phase under the condition of high-speed homogenization at 20000 rpm for 2 min to prepare a Pickering emulsion with the particle concentration of CH / LSNPs. During the homogenization process, the homogenization is carried out under the ice bath condition.

[0026] Compared with the prior art, the technical effects of the present application are reflected in:

[0027] (1) As a Pickering emulsion stabilizer, the micron-sized particle size (2.55 μm) and strong hydrophilicity of Lipu taro starch (LTS) are the main factors limiting its emulsifying performance. In this invention, a green composite modification method will be designed and developed starting from reducing the particle size of natural starch and enhancing the hydrophobicity of starch, so as to enhance the emulsifying properties of LTS and make it a good Pickering emulsion emulsifier. In this chapter, the anti-solvent precipitation method is used to reduce the particle size of natural starch, and the optimal process of the anti-solvent precipitation method is determined with the particle size and polydispersity index (PDI) as the main indicators. Subsequently, starch nanoparticles (SNPs) and natural starch are characterized and compared by methods such as scanning electron microscopy, XRD, and FTIR. Then, the hydrophobicity of SNPs is enhanced by compounding with chitosan, and the optimal compounding conditions are determined with the emulsion particle size and emulsion storage stability as the main indicators. Finally, the physicochemical properties of the particles and the basic characteristics of the emulsion are characterized.

[0028] (2) Through a composite method of an anti-solvent precipitation method and an electrostatic compounding chitosan method, this invention prepares Lipu taro nano-starch composite chitosan particles (CH / LSNPs) with smaller particle size and stronger hydrophobicity, making them have good emulsifying activity and emulsifying stability. This method is a green composite modification method that reduces the particle size of Lipu taro starch while enhancing its hydrophobicity, and prepares relatively hydrophobic chitosan composite Lipu taro starch nanoparticles.

[0029] (3) The Lipu taro nano-starch composite chitosan particles of this invention can be used to prepare Pickering emulsions, and the prepared emulsions have stronger emulsion stability compared with Lipu taro nano-starch Pickering emulsions and Lipu taro starch Pickering emulsions. Description of the Drawings

[0030] Figure 1 Shows the effects of different preparation conditions on the particle size and PDI of SNPs. Among them, A: starch suspension concentration; B: alcohol-water ratio; C: ultrasonic time.

[0031] Figure 2 Shows the scanning electron microscope images (A - C) of LSNPs, CSNPs, and WSNPs.

[0032] Figure 3 Shows the XRD patterns of different natural starches and starch nanoparticles.

[0033] Figure 4 Shows the Fourier transform infrared spectra of different natural starches and starch nanoparticles.

[0034] Figure 5are the particle size distributions (A), changes in emulsion particle size (B), and ESS (C) of Pickering emulsions stabilized by different LSNPs:CH ratios; the particle size distributions (D), changes in emulsion particle size (E), and ESS (F) of Pickering emulsions stabilized by CH / LSNPs particles complexed under different pH conditions.

[0035] Figure 6 is the turbidity change diagram of CH / SNPs in different dissociating agents.

[0036] Figure 7 are the Zeta potential values of CH, LSNPs, and CH / LSNPs at different pH values.

[0037] Figure 8 are the contact angles of CH, LSNPs, and CH / LSNPs (A - C).

[0038] Figure 9 are the Fourier transform infrared spectra of CH, LSNPs, and CH / LSNPs.

[0039] Figure 10 are Pickering emulsions prepared from different Lipu taro starches.

[0040] Figure 11 are the optical microscope images of Pickering emulsions of CH / LSNPs (A - C), LSNPs (D - F), and LTS (G - I) at different magnifications.

[0041] Figure 12 is the CLSM image of the Pickering emulsion stabilized by CH / LSNPs. Among them, LSNPs are blue (stained with Nile blue A), sunflower seed oil is green (stained with Nile red), and CH is red (stained with Rhodamine B).

[0042] Figure 13 are the microstructures and particle size distributions of Pickering emulsions with different CH / LSNPs particle concentrations.

[0043] Figure 14 are the effects of different CH / LSNPs particle concentrations on the particle size (A) and EI value after 7 days of storage (B) of Pickering emulsions.

[0044] Figure 15 are the appearances of Pickering emulsions with different CH / LSNPs particle concentrations.

[0045] Figure 16 are the effects of different CH / LSNPs particle concentrations on the apparent viscosity (A), storage modulus G', and loss modulus G" (B) of Pickering emulsions. Specific implementation methods

[0046] The technical solution of the present application will be further limited in combination with specific implementation manners below, but the scope of protection required is not limited only to the description made.

[0047] In the experimental methods in the following embodiments, unless otherwise specified, they are all conventional methods; the biological and chemical reagents used, unless otherwise specified, are all conventional reagents in this field.

[0048] Example 1

[0049] Preparation of Lipu taro starch nanoparticles:

[0050] (1) Preparation of Lipu taro starch: Fresh Lipu taro is peeled and cut into small pieces, and ground in a plant tissue crusher with distilled water at a solid-liquid ratio of 1:3 for 2 minutes. The slurry is successively sieved through 60-mesh and 120-mesh sieves, and then the filtrate is sedimented in an ice bath for 12 hours to prevent deterioration. After sedimentation for 12 hours, the upper layer of purple-red liquid is poured off, and the precipitate is resuspended in distilled water at a solid-liquid ratio of 1:3. The pH of the mixture is adjusted to 10 by adding NaOH solution (1 mol / L), and stirred continuously for 2 hours. Subsequently, it is neutralized to pH 7 with HCl (1 mol / L), centrifuged at 1200×g for 15 minutes, the supernatant is removed, and the upper layer of yellow impurities is scraped off to collect the precipitate. The precipitate is re-stirred and resuspended in distilled water at a ratio of 1:3 and centrifuged at 1200×g for 15 minutes. This process is repeated three times to ensure that the supernatant is clear and transparent and there are no obvious impurities on the upper layer of the precipitate. Finally, the precipitate is dried at 45°C for 48 hours, ground into powder, passed through a 120-mesh sieve, and the starch is stored in a sample bag to obtain Lipu taro starch.

[0051] (2) Preparation of Lipu taro starch nanoparticles:

[0052] Prepare starch suspensions with concentrations of 1%, 1.5%, 2%, 3%, 4% and 5%, continuously stir in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After the gelatinized starch is ultrasonically treated for 30 min, it is gradually added dropwise to an ethanol solution with an ethanol-water ratio of 3:1 under continuous stirring, and starch nanoparticles (LSNPs) are prepared by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain LSNPs. The LSNPs are washed 3 times with anhydrous ethanol to remove excess water, pre-frozen at -18°C for 12 h, and then freeze-dried in vacuo for 48 h to obtain dry LSNPs.

[0053] Example 2

[0054] Preparation of Lipu taro starch nanoparticles:

[0055] (1) Preparation of Lipu taro starch: Prepare Lipu taro starch in the same way as in Example 1.

[0056] (2) Preparation of Lipu taro starch nanoparticles:

[0057] Prepare a 4% starch suspension, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After gelatinization, the starch is ultrasonically treated for 15 min and then gradually added dropwise to ethanol solutions with alcohol-water ratios of 0.7:1, 0.8:1, 1:1, 3:1, and 6:1 that are continuously stirred. Starch nanoparticles (LSNPs) are prepared by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain LSNPs. The LSNPs are washed three times with absolute ethanol to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry LSNPs.

[0058] Example 3

[0059] Preparation of Lipu taro starch nanoparticles:

[0060] (1) Preparation of Lipu taro starch: Prepare Lipu taro starch as in Example 1.

[0061] (2) Preparation of Lipu taro starch nanoparticles:

[0062] Prepare a 4% starch suspension, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After gelatinization, the starch is ultrasonically treated for 0 min, 30 min, 50 min, 70 min, and 90 min and then gradually added dropwise to a continuously stirred ethanol solution with an alcohol-water ratio of 1:1. Starch nanoparticles (LSNPs) are prepared by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain LSNPs. The LSNPs are washed three times with absolute ethanol to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry LSNPs.

[0063] Example 4

[0064] Preparation of Lipu taro starch nanoparticles:

[0065] (1) Preparation of Lipu taro starch: Prepare Lipu taro starch as in Example 1.

[0066] (2) Preparation of Lipu taro starch nanoparticles:

[0067] Prepare a 4% starch suspension, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After gelatinization, the starch is ultrasonically treated for 50 min and then added dropwise to a continuously stirred ethanol solution with an ethanol-to-water ratio of 1:1 to prepare Lipu taro starch nanoparticles (LSNPs) by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain LSNPs. The LSNPs are washed three times with absolute ethanol to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry LSNPs.

[0068] Comparative Example 1

[0069] Preparation of cassava starch nanoparticles:

[0070] (1) Preparation of cassava starch: It is commercially available cassava starch.

[0071] (2) Preparation of cassava starch nanoparticles:

[0072] Prepare a 4% starch suspension, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After gelatinization, the starch is ultrasonically treated for 50 min and then added dropwise to a continuously stirred ethanol solution with an ethanol-to-water ratio of 1:1 to prepare cassava starch nanoparticles (CSNPs) by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain CSNPs. The CSNPs are washed three times with absolute ethanol to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry CSNPs.

[0073] Comparative Example 2

[0074] Preparation of wheat starch nanoparticles:

[0075] (1) Preparation of wheat starch: It is commercially available wheat starch.

[0076] (2) Preparation of wheat starch nanoparticles:

[0077] Prepare a 4% starch suspension, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After gelatinization, the starch is ultrasonically treated for 50 min and then added dropwise to a continuously stirred ethanol solution with an ethanol-to-water ratio of 1:1 to prepare wheat starch nanoparticles (WSNPs) by the anti-solvent precipitation method. After the solution is stirred at room temperature for 10 min, it is centrifuged at 8000 rpm for 10 min, and the supernatant is discarded to obtain WSNPs. The WSNPs are washed three times with absolute ethanol to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry WSNPs.

[0078] Performance testing and result analysis of starch nanoparticles

[0079] 1. Influence of Preparation Process on the Particle Size and Dispersion Degree of Lipu Taro Starch Nanoparticles

[0080] The sample particles were vortex-dispersed in distilled water to prepare a suspension with a particle concentration of 0.1 wt%. Then the sample was transferred to a cuvette and placed in the sample cell of a Nano-ZS Zetasizer nanoparticle size analyzer for detection under the conditions of a temperature of 25 °C, an incident angle of 90°, an equilibration time of 120 s, a dispersion coefficient of water of 1.33, and a dispersion coefficient of starch of 1.54.

[0081] The decrease in starch particle size increases the stability of Pickering emulsions towards emulsification. Due to more effective packing, smaller starch particles provide a more cohesive barrier at the phase interface. Therefore, taking the particle size and PDI as the investigation indexes, the effects of the mass concentration of the starch suspension (1% - 5%), i.e., Example 1, the alcohol-water ratio (0.7:1 - 5:1), i.e., Example 2, and the ultrasonic time (0 min - 90 min), i.e., Example 3, on the particle size and PDI were explored. In terms of the average particle size, as the starch concentration and the alcohol-water ratio increased, the average particle size first decreased and then increased. As the ultrasonic time increased, the average particle size continuously decreased and then tended to be stable; in terms of PDI, as the starch concentration increased, the PDI of the particles first decreased and then increased. As the alcohol-water ratio and the ultrasonic time increased, the PDI of the particles continuously decreased and then tended to be stable.

[0082] A. In Example 1, the influence of the starch suspension concentration on the average particle size and PDI of SNPs is as Figure 1 shown in A. As the starch suspension concentration increased from 1% to 2%, the size of SNPs decreased significantly from 256.6 nm to 171.2 nm. However, during the period of the starch suspension concentration from 2% to 5%, the particle size and PDI showed a slow increasing trend (171.2 nm - 197.33 nm), and the change during the period of the starch suspension concentration from 2% to 4% was not significant. The change trend of PDI was the same as that of the average particle size. Therefore, according to the principle of efficiently preparing nano-starch particles with small particle size and PDI, a starch suspension concentration of 4% was selected for subsequent single-factor experiments.

[0083] B. In Example 2, the influence of the alcohol-water ratio on the average particle size and PDI of SNPs is as Figure 1As shown in B. The influence of the alcohol-water ratio on the average particle size and PDI of SNPs can also be explained by the supersaturation theory. The solute in the solution starts from the supersaturated state. Once the critical nucleation concentration is reached, atomic nuclei begin to form. This results in a decrease in the solute concentration in the dispersed phase. The decrease in solute concentration slows down the formation of additional atomic nuclei and causes the growth of the already formed atomic nuclei through aggregation and precipitation upon collision. When the alcohol-water ratio is lower than 1:1, the average particle size decreases rapidly and the PDI increases accordingly. At this time, the saturation conditions in the system are more conducive to growth and few atomic nuclei are formed. Therefore, particles with a higher average particle size are grown. When the alcohol-water ratio is higher than 1:1, the average particle size increases significantly, but its PDI is always less than 0.4, indicating that the formed SNPs are relatively uniform. This shows that the saturation at this time has the conditions for homogeneous nucleation. The reason for the increase in the average particle size may be that the number of atomic nuclei is so large under the condition of a large alcohol-water ratio that they often meet, resulting in the aggregation of these atomic nuclei, which hinders the further reduction of the particle size with the increase of the alcohol-water ratio. Therefore, according to the principle of preparing nano-starch particles with small particle size and PDI at high efficiency and low cost, an alcohol-water ratio of 1:1 was selected for the subsequent single-factor experiments.

[0084] C. In Example 3, the influence of the ultrasonic time on the average particle size and PDI of SNPs is as Figure 1 shown in C. From the experimental results, it can be seen that ultrasonic treatment can significantly reduce the average particle size and PDI of SNPs. The cavitation effect generated by ultrasonic treatment will cause the breakage of starch chains, reduce the molecular weight of starch and the viscosity of the starch paste solution. This results in more short starch molecular chains being easily diffused into the non-solvent, aggregating and forming smaller particles, which promotes the uniform kinetics in the nano-precipitation process and will result in the production of SNPs with smaller particle size and more uniform distribution. The intensity of the cavitation effect of ultrasonic treatment is proportional to the ultrasonic time. Therefore, when the ultrasonic time is between 0 - 50 min, with the increase of the ultrasonic time, the average particle size and PDI of starch show a continuous decreasing trend. However, when the ultrasonic time is between 50 - 90 min, the starch particle size and PDI basically remain unchanged, and the starch particle size is reduced to the limit size, indicating that the influence of ultrasonic treatment on the starch paste has a limited degradation process. According to the principle of preparing nano-starch particles with small particle size and PDI at high efficiency and low cost, an ultrasonic time of 50 min was selected as the optimal ultrasonic time for preparing SNPs.

[0085] Through single-factor experiments, the optimal preparation process parameters of SNPs were obtained as follows: the concentration of the starch suspension was 4%, the alcohol-water ratio was 1:1, and the ultrasonic time was 50 min. This is the Lipo taro starch nanoparticles obtained in Example 4.

[0086] 2. Zeta potential measurement

[0087] The sample particles were formulated into a 0.1 wt% suspension and added to the Zeta potential sample cell. The Zeta value of the sample was measured by a nano particle size analyzer under the conditions of 25 °C and a detection angle of 173°.

[0088] After determining the optimal preparation process of SNPs through single - factor experiments, this process was used to prepare Lipo taro starch nanoparticles (LSNPs) in Example 4, cassava starch nanoparticles (CSNPs) in Comparative Example 1, and wheat starch nanoparticles (WSNPs) in Comparative Example 2, respectively. The Zeta potential data of Example 4, Comparative Example 1, and Comparative Example 2 are shown in Table 1. All different types of SNPs showed negative surface charges. Among them, the Zeta potential value of LSNPs was - 16.60 mV, showing the largest surface negative charge.

[0089] Table 1 Average particle size, polydispersity index (PDI), and Zeta potential of SNPs

[0090]

[0091] Previous studies have shown that the negative surface charge of SNPs comes from deprotonated hydroxyl radicals in the aqueous medium. Generally, when the absolute value of the Zeta potential of the suspension system > 30 mV, we say that the particles have a high surface charge, and the interaction between particles is mainly electrostatic repulsion, which can thus inhibit the aggregation of particles. On the other hand, when - 30 mV < Zeta potential < 30 mV, we say that the particles have a low surface charge, and van der Waals attraction dominates in the suspension system, thus leading to a small degree of aggregation of dispersed particles. LSNPs, CSNPs, and WSNPs all belong to low surface charge, which indicates that the electrostatic repulsion between SNPs is insufficient, possibly leading to a certain degree of aggregation. This is consistent with the results obtained from PDI. The lower the absolute value of the Zeta potential of the particles, the larger the PDI and the more serious the aggregation.

[0092] 3. Determination of particle morphological characteristics

[0093] The particle morphology of LTS, CS, and WS was visualized using an F16502 Phenom scanning electron microscope (SEM). Briefly, the starch was positioned on the conductive adhesive fixed on the sample holder, and the starch sample that was not adhered to the conductive adhesive was blown clean with nitrogen. Then a thin gold film was coated by a DC sputtering coater, and after sputtering with gold, it was purged with nitrogen again. It was placed in the instrument sample slot, and images were obtained at a voltage of 10 kV and a magnification of 10000×.

[0094] The particle morphology diagrams and particle size distributions of SNPs observed by SEM are as Figure 2 and shown in Table 1. Among them, the SEM pictures of Example 4 and Comparative Example 1 were relatively similar, existing in the form of relatively discrete small aggregates (Figure 2 A and B), showing a platelet-like shape. Comparative Example 2 exists in the form of tight large aggregates ( Figure 2 C), showing an irregular broken shape. All SNPs exhibit a certain degree of aggregation, indicating poor dispersibility and a tendency to agglomerate. The possible reasons can be explained from the following two aspects. One is that this may be related to the separation and drying methods of SNPs. Previous studies have shown that the separation and drying methods can affect the SNPs produced by the anti-solvent precipitation method. For example, appropriate stirring will cause SNPs to rapidly form aggregates in the ethanol-water mixture and then settle at the bottom of the container. The freeze-drying method of drying often leads to the aggregation of particles. The second is that SNPs have a large surface area and contain a large number of hydroxyl groups, which can form strong connections through hydrogen bonds, resulting in particle aggregation.

[0095] The particle size and PDI of SNPs are shown in Table 1. The average particle size and PDI of LSNPs are the smallest (126.7 nm and 0.24), followed by CSNPs (201.8 nm and 0.38) and WSNPs (710.97 nm and 0.66). The average particle size and PDI of SNPs also conform to the results of the SEM images of SNPs. The smallest average particle size and PDI of LSNPs indicate that it may have the potential to become a Pickering emulsion stabilizer.

[0096] 4. X-ray determination of crystallization properties

[0097] The crystallization properties of the samples were measured using a D8 Discover X-ray diffractometer. The starch was dried in an oven at 45 °C for 24 hours to achieve a similar moisture content, and then flattened onto the sample holder. CuKα radiation diffraction analysis was performed in the angular range of 5° - 45° (2θ) at a scanning rate of 5° / min. The crystallinity of the starch was calculated by integration using Origin 2021 software.

[0098] The XRD patterns of all native starches and their corresponding SNPs are as Figure 3 shown. The results show that all SNP samples formed a V-type crystal. All native starches exhibited an A-type crystal structure. Compared with the XRD patterns of native starches, the diffraction peaks of starch nanoparticles decreased to almost completely disappear, which may be due to the energy input generated by ultrasonic waves that disrupted the original crystal arrangement of the starch. This indicates that native starch undergoes an amorphous process during the conversion to SNP. And the presence of a characteristic V-type peak was also observed at approximately 20.6° for all SNPs, which is related to the complex formed by simple starch and lipids. And the diffraction peak intensity of LSNPs at 20.6° was the largest, which implies that it formed the most starch-lipid complexes.

[0099] 5. Fourier transform infrared spectroscopy determination of absorption peaks

[0100] Mix starch with dry KBr in a ratio of 1:50, finely grind it, and compress it into a transparent circular thin slice. Use OMNIC software (Thermo Fisher Scientific, Waltham, MA, USA) to determine the peak heights at 1047 and 1022 cm-1 within the wavelength range of 1200 to 800 cm-1 in the infrared spectrum of starch by Fourier deconvolution method, where the enhancement factor is set to 1.9 and the peak width is 40 cm-1.

[0101] Fourier transform infrared spectra of all native starches and their corresponding SNPs in the range of 4000 - 400 cm-1 are as shown Figure 4 in. Qualitatively, all native starches and their corresponding SNPs show generally similar Fourier transform infrared spectra, and no new peaks are observed for SNPs, indicating that no new chemical substances are produced by the anti-solvent precipitation method. However, from a quantitative perspective, the peak intensities are changed for SNPs compared with native starches. The results show that the anti-solvent precipitation method reduces the hydrogen bond interaction between SNPs molecules, destroys the α-1,6 glycosidic bond in the starch molecular structure, and reduces the water tightly bound to SNPs.

[0102] Fourier transform infrared spectra of all samples show a broad characteristic band in the region of 3000 - 3600 cm-1, which represents the free stretching vibration of the OH group in starch molecules, and its width indicates the degree of intermolecular and intramolecular hydrogen bond formation. The decrease in peak intensity of SNPs in this region indicates that the anti-solvent precipitation method reduces the hydrogen bond interaction between SNPs molecules. Also, the peak intensity of SNPs at 1022 cm-1 decreases, but the peak intensity at 1400 cm-1 increases, which also indicates the weakening of intermolecular hydrogen bonds. The weakening of intermolecular hydrogen bonds in SNPs may be related to the destruction of the structure of native starch caused by gelatinization and ultrasonic treatment.

[0103] The peaks observed at wavelengths of approximately 2932 cm-1, 1400 cm-1, and 1022 cm-1 show the stretching and bending vibrations of C-H in methylene and the stretching vibration of C-O-C in the α-1,6 glycosidic bond respectively. The decrease in peak intensities at 2932 cm-1 and 1022 cm-1 and the increase in peak intensity at 1400 cm-1 observed in the Fourier transform infrared spectrum of SNPs indicate that the α-1,6 glycosidic bond is destroyed, which is the result of ultrasonic treatment.

[0104] The characteristic absorption peak detected near 1638 cm-1 is related to the bending vibration of water adsorbed in the amorphous region of starch. The weakening of the peak intensity at this position for SNPs indicates a decrease in the water tightly bound to SNPs, which is consistent with the previous result of the weakening of intermolecular hydrogen bonding in SNPs. This is because during the formation of SNPs, amylose forms a single-helix structure complex with ethanol, restricting the binding with water.

[0105] 6. Contact angle measurement

[0106] The starch was pressed into a 10-cm diameter circular disc using a tablet press and placed on the sample stage. A drop of deionized water (3 μl) was placed on the starch film through a contact angle measuring instrument. After reaching equilibrium, the three-phase contact angle was measured through software.

[0107] The contact angle can reflect the two-phase wettability of colloidal particles, which is important for the formation and stability of Pickering emulsions, similar to the hydrophilic-lipophilic balance value HLB value discussed in traditional emulsions. Generally speaking, for solid particles used to prepare oil-in-water Pickering emulsions, the closer the contact angle of the solid particles is to 90°, the greater the stability the particles will impart to the Pickering emulsion. Table 2 shows the contact angle analysis results of native starch and SNPs. The contact angles of all SNPs samples are significantly increased compared to their corresponding native starch, indicating a significant improvement in the hydrophobicity of SNPs, which is relatively beneficial for the formation of a stable Pickering emulsion system.

[0108] In Table 2, the contact angles of native starches LTS, CS, and WS are 37.75°, 34.51°, and 33.16° respectively, indicating that native starch is highly hydrophilic, which is related to the large number of hydrophilic hydroxyl groups in native starch. The presence of these hydroxyl groups makes native starch vulnerable to water erosion. After the anti-solvent precipitation method, the contact angles of the prepared LSNPs, CSNPs, and WSNPs are significantly increased to 53.26°, 50.56°, and 44.23°. The improvement in the hydrophobicity of SNPs may benefit from the single-helix V-type crystalline structure formed by amylose and ethanol molecules, resulting in the formation of a more hydrophobic cavity similar to cyclodextrin. The observation of the diffraction peak with the maximum intensity at 20.6° for LSNPs in the XRD pattern ( Figure 3 ) provides a reasonable explanation for its largest contact angle.

[0109] 7. Emulsifying performance measurement

[0110] Mix 1.4 g of starch sample with 10 mL of sunflower oil and distilled water, and then homogenize it for 2 minutes at 25 °C and 7700×g using a homogenizer. At 0 and 10 minutes after homogenization, dilute 100 μL of the emulsion with 10 mL of 0.1% SDS solution and record its absorbance at 500 nm. The emulsifying activity index (EAI, the interfacial area generated per unit mass of starch) and the emulsifying stability index (ESI, the time when the emulsion turbidity reaches half of its initial value) are calculated using the following formulas:

[0111]

[0112] where T is the turbidity (m-1), is the oil phase fraction in the formed emulsion (0.5), C is the amount of starch in the aqueous phase per unit volume (10000 g / m-3), 0.1 is the conversion factor, D is the dilution factor (100), L is the optical range (0.01), and A0 and A10 are the absorbance values of the diluted emulsion recorded at 500 nm at 0 minutes and 10 minutes after homogenization, respectively.

[0113] To compare the differences in the emulsifying ability between SNPs and native starch, the EAI and ESI values, which are the same as those used to evaluate the emulsifying properties of native starch, are used to characterize the emulsifying ability of SNPs. The results are shown in Table 2. After nano-modification by the anti-solvent precipitation method, the emulsifying properties of SNPs are improved compared to those of native starch, indicating that nano-modification by the anti-solvent precipitation method can improve the emulsifying properties of starch. Among them, LSNPs have the best emulsifying properties, with the EAI and ESI increasing from 8.53 m 2 / g to 9.24 m 2 / g and from 69.18 min to 137.63 min, respectively; followed by CSNPs, with their EAI and ESI increasing from 2.35 m 2 / g to 3.36 m 2 / g and from 25.15 min to 65.77 min, respectively; and finally WSNPs, with their EAI and ESI increasing from 0.37 m 2 / g to 1.81 m 2 / g and from 11.48 min to 36.16 min, respectively.

[0114] Table 2 Contact angles, EAI, and ESI of native starch and SNPs

[0115]

[0116] According to the Pickering emulsion stability principle formula, this may be due to the improvement of starch hydrophobicity and the reduction of particle size. Generally speaking, the overall stability of Pickering emulsion is inversely proportional to the particle size. The smaller the particles, the higher the packing efficiency, and thus the more uniform the adsorption layer generated. However, the improvement of the emulsifying performance of SNPs formed by nano-modification is limited, and there are certain limitations in its industrial application as an emulsifier in the food industry. The limited wettability of SNPs (compared with 90°) may be one of the reasons for the insufficient emulsifying ability of SNPs. To sum up, compared with CS and WS, SNPs prepared by LTS have the best emulsifying activity and emulsifying stability. However, its relatively high hydrophilicity (contact angle of 53.26°) may still be an important reason for the limited emulsifying ability. Research shows that starch particles can be used as effective emulsion stabilizers after hydrophobic modification. Therefore, LSNPs are selected for the next modification to improve their hydrophobicity.

[0117] Example 5

[0118] Preparation of chitosan composite Lipu taro starch nanoparticles (CH / LSNPs):

[0119] (1) Preparation of Lipu taro starch nanoparticles: Operate according to Example 4 to obtain Lipu taro starch nanoparticles.

[0120] (2) Preparation of chitosan composite Lipu taro starch nanoparticles (CH / LSNPs): Dissolve chitosan (CH) in 1% (v / v) acetic acid solution and stir overnight at room temperature to ensure complete dissolution, and prepare a 1 wt% chitosan solution. Dissolve LSNPs with a certain concentration in distilled water and continuously stir magnetically until completely dispersed to form an SNPs stock solution. Subsequently, add the chitosan solution to the SNPs stock solution at ratios of 0:1, 0.025:1, 0.045:1, 0.065:1, 0.085:1, 0.1:1, 0.2:1, adjust the pH to 4, and continuously stir magnetically to form an LSNPs:CH mixed solution.

[0121] Example 6

[0122] Preparation of chitosan composite Lipu taro starch nanoparticles (CH / LSNPs):

[0123] (1) Preparation of Lipu taro starch nanoparticles: Operate according to Example 4 to obtain Lipu taro starch nanoparticles.

[0124] (2) Preparation of chitosan composite Lipo taro starch nanoparticles (CH / LSNPs): Dissolve chitosan (CH) in 1% (v / v) acetic acid solution and stir overnight at room temperature to ensure complete dissolution, and prepare a 1 wt% chitosan solution. Dissolve a certain concentration of LSNPs in distilled water and continuously stir magnetically until completely dispersed to form an SNPs stock solution. Subsequently, add the chitosan solution to the SNPs stock solution at a ratio of 0.085:1, adjust the pH to 2, 3, 4, 5, 6, 7, and 8 respectively, and continuously stir magnetically to form an LSNPs:CH mixed solution.

[0125] Example 7

[0126] Preparation of chitosan composite Lipo taro starch nanoparticles (CH / LSNPs):

[0127] (1) Preparation of Lipo taro starch nanoparticles: Operate according to Example 4 to obtain Lipo taro starch nanoparticles.

[0128] (2) Preparation of chitosan composite Lipo taro starch nanoparticles (CH / LSNPs): Dissolve chitosan (CH) in 1% (v / v) acetic acid solution and stir overnight at room temperature to ensure complete dissolution, and prepare a 1 wt% chitosan solution. Dissolve a certain concentration of LSNPs in distilled water and continuously stir magnetically until completely dispersed to form an SNPs stock solution. Subsequently, add the chitosan solution to the SNPs stock solution at a ratio of 0.085:1, adjust the pH to 4, and continuously stir magnetically to form an LSNPs:CH mixed solution.

[0129] Example 8

[0130] Preparation of chitosan composite Lipo taro starch nanoparticle (CH / LSNPs) emulsion:

[0131] Fix the volume of sunflower seed oil phase at 30%. Under the condition of the compound of CH and LSNPs with a pH of 4, take the chitosan composite Lipo taro starch nanoparticles prepared in Example 7 and prepare a dispersion liquid with a particle concentration of 4% mass concentration of CH / LSNPs, and homogenize and mix it with the oil phase under the condition of high-speed homogenization at 20000 rpm for 2 min to prepare a Pickering emulsion of chitosan composite Lipo taro starch nanoparticles. During the homogenization process, in order to prevent the emulsion temperature from being too high and affecting subsequent tests, homogenization is carried out under ice bath conditions.

[0132] Performance testing and result analysis of chitosan composite starch nanoparticles

[0133] 1. Influence of composite process on the emulsifying performance of CH / LSNPs

[0134] Taking the emulsion storage stability as an index, the effects of the LSNPs:CH ratio (1:0, 1:0.025, 1:0.045, 1:0.065, 1:0.085, 1:0.1, and 1:0.2) and pH (2, 3, 4, 5, 6, 7, and 8) on the emulsification performance of the particles were investigated. With the increase of the LSNPs:CH ratio, the emulsification performance of the particles showed an increasing trend until it leveled off (specifically reflected in the more concentrated particle size distribution of the prepared emulsion, and the droplet size and emulsion stability index ESS continuously decreased until they leveled off); with the increase of the composite environment pH, the emulsification performance of the particles showed a trend of increasing first and then decreasing.

[0135] A. Under the composite condition with a pH value of 4, Pickering emulsions stabilized by different ratios of CH / LSNPs were successfully prepared. Figure 5 A shows the droplet size distribution diagrams of Pickering emulsions prepared with different ratios of LSNPs:CH. It can be seen from the particle size distribution diagrams that all Pickering emulsion samples showed a multimodal distribution. According to previous studies, we believe that the peak at the small particle size is related to the complexes or nanoparticles that have not been adsorbed onto the droplet surface. The peak at the large particle size may be related to the aggregation of emulsion droplets. Only the Pickering emulsion stabilized by LSNPs (labeled 1:0 in the figure) showed a multimodal distribution with many and relatively uniform peaks, indicating that LSNPs alone could not stabilize the Pickering emulsion well, with serious particle aggregation and insufficient emulsification activity. Although the other samples also showed a multimodal distribution with mainly three peaks, the position of their main peak was relatively concentrated, and the shoulder peaks on both sides were smaller, indicating that the addition of CH could enhance the emulsification ability of the particles. With the increase of the CH content, the main peak continuously increased, and the right shoulder peak continuously decreased until it leveled off, indicating that the addition of CH could improve the aggregation of oil droplets in the Pickering emulsion prepared by LSNPs, and the improvement effect reached the maximum when the LSNPs:CH ratio reached 1:0.085. Figure 5B and C show the changes in the emulsion droplet size (expressed as D[4,3]) and the emulsion stability index ESS of Pickering emulsions prepared with different LSNPs:CH ratio particles under the combined condition of pH 4 during storage for up to 7 days. For the Pickering emulsion stabilized only by LSNPs, the emulsion changed sharply 1 day and 7 days after preparation, and the ESS value was also the largest (reaching 2.32), indicating that LSNPs alone could not stabilize the Pickering emulsion well, which was consistent with the results observed in the particle size distribution. As the CH ratio increased, the degree of change in the emulsion droplet size within 7 days gradually decreased, and the emulsion stability gradually increased. For the problem of emulsion stability and larger particle size with the LSNPs:CH ratio between 1:0.025 and 1:0.065, a reasonable explanation is that the surface charge degree of CH may affect the behavior of CH during the coating process (such as self-aggregation of CH or electrostatic interaction between LSNP and chitosan). At low CH addition, the surface charge of the particles was almost neutralized, resulting in bridging flocculation of CH, thus causing droplet aggregation. In addition, the interfacial properties of CH / LSNPs may be weakened due to the interaction of CH existing between droplets, thereby reducing the resistance of the Pickering emulsion to droplet coalescence, and then large droplets appeared. As the LSNPs:CH ratio increased to 1:0.085, the fresh emulsion droplet size reached the minimum value ( Figure 5 B), and the ESS value was also close to 1 ( Figure 5 C). Continuing to increase the CH ratio, the particle size and ESS remained almost unchanged. It shows that when the LSNPs:CH ratio reaches 1:0.085, the stability of the Pickering emulsion can be effectively enhanced, which is consistent with the analysis results of the particle size distribution diagram. When the LSNPs:CH ratio reaches 1:0.085, the particle emulsifying activity and emulsion stability can reach the highest. Therefore, the LSNPs:CH ratio of 1:0.085 is selected to prepare CH / LSNPs particles.

[0136] 2. Under the condition of the LSNPs:CH ratio of 1:0.085, Pickering emulsions stabilized by CH / LSNPs complexed under different pH conditions were successfully prepared. Figure 5Figure D shows the droplet size distribution diagrams of Pickering emulsions prepared with different ratios of CH / LSNPs. It can be seen from the droplet size distribution diagrams that all Pickering emulsion samples exhibit a three-peak distribution. Among them, the samples with pH equal to 7 and 8 show the largest peak at large particle sizes, indicating that there is severe droplet aggregation in the emulsion under neutral and alkaline pH conditions. This may be related to the surface charge of CH and will be verified by dissociation force analysis and Zeta potential measurement in the following. The amino group of CH is protonated and positively charged under acidic conditions (about below pH 6.5), and can be firmly attached to the surface of negatively charged particles through electrostatic interaction. When the pH value is in neutral and alkaline conditions, deprotonation of CH causes it to lose most of its charge, and CH undergoes intermolecular association in the solution to form flocculent precipitates. This not only affects the complexation of CH and LSNPs but also produces precipitates, affecting the stability of the emulsion system. Under strongly acidic conditions (pH value less than 4), the relatively large initial droplet size and ESS value of the emulsion indicate that the emulsifying activity of the particles and the stability of the emulsion are not satisfactory either. This may be due to the fact that the structure and surface charge of SNPs particles are damaged under strongly acidic conditions, which affects the complexation of LSNPs and CH and the adsorption of CH / LSNPs on the droplet surface. When the pH value is between 4 and 6, the droplet size of the emulsion is the smallest and the storage stability of the emulsion is the best, indicating that CH / SNPs can better stabilize the Pickering emulsion when the complexation pH range is between 4 and 6. For the convenience of subsequent preparation, pH 4 (the pH of the acetic acid solution of CH is approximately 4) is selected as the pH condition for the complexation of CH and LSNPs.

[0137] 2. Dissociation Force Measurement

[0138] The interaction forces for the formation and stability of the complex are analyzed by measuring the turbidity of the complex in different types of dissociating agents using a UV spectrophotometer. Specifically, a 6M urea (Urea) solution is prepared as the dissociating agent for hydrogen bond interaction, a 0.5% SDS solution as the dissociating agent for hydrophobic interaction, and a 500 mM NaCl solution as the dissociating agent for electrostatic interaction. CH / LSNPs are separately dispersed in the above three different dissociating agents (concentration 0.1%), vortexed thoroughly and then left to stand at room temperature for 12 hours. The absorbance at 600 nm is recorded using a UV spectrophotometer, and this absorbance is the turbidity. The dissociating agent without CH / LSNPs is used as the blank control.

[0139] The results of the dissociation force measurement of CH / LSNPs are as Figure 6 shown. According to the dissociating forces corresponding to different solutions, CH / LSNPs are mainly complexed by electrostatic interaction, followed by hydrophobic interaction and hydrogen bond. From Figure 6It can be seen that, compared with the control sample, the turbidity of the sample decreases in all dissociating agents, but the degree of decrease is different, which is related to the intermolecular interaction force of the sample. Among all dissociating agents, the turbidity of the sample decreases the most in 500 mM NaCl solution, followed by 0.5% SDS solution and 6 M Urea solution. The degree of turbidity decrease of CH / LSNPs in these two solutions is not much different. The results of the dissociation force experiment are consistent with the analysis of the results of the particle composite pH conditions on the emulsifying properties of CH / LSNPs in the previous text, indicating that pH affects the surface charges of LSNPs and CH, changes the strength of their electrostatic interaction, and thus affects the emulsifying properties of CH / SNPs.

[0140] 3. Zeta Potential Analysis

[0141] The sample particles were prepared into a 0.1% w / v suspension. After adjusting different pH values with 0.2 M HCl or NaOH, they were added to the Zeta potential sample cell. The Zeta value of the sample was measured by a nanoparticle size analyzer under the conditions of 25 °C and a detection angle of 173°.

[0142] Zeta potential is the potential difference between the dispersion medium and the stern layer on the surface of the dispersed particles. By identifying which electrode the particles move towards during electrophoresis, the positive or negative of the surface charge of the particles can be determined. It reflects the electrostatic repulsive force between the particles. In the aqueous dispersion, pH is one of the most influential parameters for Zeta potential measurement. Under acidic and alkaline pH conditions, the magnitude of the Zeta potential becomes more positive and more negative respectively. Therefore, to explore how pH affects the surface charge conditions of LSNPs and CH and further clarify the composite mechanism of LSNPs and CH, the Zeta potential values of LSNPs, CH, and CH / LSNPs under different pH conditions were analyzed respectively, and the results are as Figure 7 shown. Under all pH conditions, LSNPs all showed negative Zeta potential values, but the absolute value of the Zeta potential continuously increased with the increase of the pH value. Under all pH conditions, both LSNPs and CH / LSNPs showed positive Zeta potential values, and the change trend was the same. The absolute value of the Zeta potential continuously decreased with the increase of the pH value.

[0143] In the pH range of 2 - 3, the Zeta potential of LSNPs approaches 0, which affects the electrostatic interaction with CH and results in poor emulsifying performance. When the pH value increases from 2 to 6, the absolute value of the Zeta potential of LSNPs increases sharply. Although the Zeta potential of CH also decreases, its absolute value is still greater than 20, which will contribute to the electrostatic complexation of the two substances. When the pH value is greater than 6, the Zeta potential of CH / LSNPs approaches 0, which may lead to severe aggregation between particles, affecting their adsorption at the droplet interface. At the same time, the particles adsorbed on the droplet surface will also cause droplet aggregation to form large droplets due to insufficient electrostatic repulsion. The analysis results of the Zeta potential indicate that the pH value for particle complexation affects particle complexation and its emulsifying properties by changing the surface charge of the particles.

[0144] 4. Contact Angle Analysis

[0145] The LSNPs:CH mixed solution obtained in Example 7 was pre-frozen at -18 °C for 12 h and then vacuum freeze-dried for 48 h to obtain a dry analysis sample. Starch was pressed into a 10 cm diameter circular tablet using a tablet press and placed on the sample stage. A drop of deionized water (3 μl) was placed on the starch film through a contact angle measuring instrument. After reaching equilibrium, the three-phase contact angle was measured through software.

[0146] We measured the contact angles of LTS, LSNPs, and CH / LSNPs to represent their wettability and thus evaluate the potential of the particles as Pickering emulsion stabilizers. The results are as Figure 8 shown. The results indicate that the hydrophobicity of CH / LSNPs is greatly improved, showing great potential as a Pickering emulsion stabilizer. After nano-modification by the anti-solvent method and electrostatic complexation hydrophobic modification with CH, the contact angle of CH / LSNPs increased from 37.41° to 81.55°, indicating that the contact angle of LSNPs increased significantly and approached 90° by adding CH, increasing the hydrophobicity of the sample.

[0147] 5. FTIR

[0148] The LSNPs:CH mixed solution obtained in Example 7 was pre-frozen at -18 °C for 12 h and then vacuum freeze-dried for 48 h to obtain a dry analysis sample. Starch was mixed with dry KBr at a ratio of 1:50, finely ground, and compressed into a transparent circular thin film. The peak heights at 1047 and 1022 cm-1 were determined by Fourier deconvolution method in the wavelength range of 1200 to 800 cm-1 of the starch infrared spectrum using OMSNIC software (Thermo Fisher Scientific, Waltham, MA, USA), where the enhancement factor was set to 1.9 and the peak width was 40 cm-1.

[0149] As is well known, Fourier transform infrared spectroscopy (FTIR) is a very useful tool for detecting interactions in blends. Therefore, FTIR was applied to examine the possible interactions between blend components. We studied the effect of chitosan composite modification on the infrared spectral characteristics of starch, and the results are as Figure 9 shown. The results indicate that hydrogen bond interactions occurred between the hydroxyl groups of LSNPs and the amino groups of CH.

[0150] The spectrum of the CH molecule shows a broad band between 3000 - 3600 cm-1, which is attributed to the stretching vibrations of N-H and O-H. The spectrogram shows weak absorption in the 2800 - 3000 cm-1 region, related to C-H stretching. The peak near 1651 cm-1 is related to the stretching of C=O (amide I), and the peak near 1596 cm-1 is related to the bending of N-H (amide II). When two or more substances are mixed, physical mixing and chemical interactions are reflected by changes in characteristic spectral bands. With the mixing of CH and LSNPs, an amide - NH2 absorption peak appears at 1560 cm-1 in CH / LSNPs, and the amino band at 1651 cm-1 shifts to 1638 cm-1. This result may indicate that hydrogen bond interactions occurred between the hydroxyl groups of LSNPs and the amino groups of CH.

[0151] 5. Preparation of Pickering emulsions with CH / LSNPs and their emulsion appearance analysis

[0152] The Pickering emulsions of the present invention were all prepared under the conditions of an oil phase volume of 30%, a particle concentration of 4%, and a pH = 4. The particle size of the emulsion was measured by a laser particle size analyzer, and the results are expressed as the D[4,3] value. Specifically, the undiluted emulsion sample was dropped into the instrument sample cell and the sample was continuously ultrasonically dispersed. When the light shielding level reached between 12% and 15%, the particle size distribution of the emulsion was tested. Among them, the dispersion medium was distilled water, the circulation pump speed was 2000 rpm, the refractive index of distilled water was set to 1.333, and the refractive index of the emulsion was set to 1.46.

[0153] The emulsion storage stability (ESS) is expressed by the degree of change in the emulsion particle size within 7 days and is calculated as follows:

[0154]

[0155] where D0 is the D[4,3] value of the freshly prepared emulsion, and D7 is the D[4,3] value of the emulsion after 7 days.

[0156] The emulsion appearance of the Pickering emulsions prepared with the three kinds of particles is as Figure 10As shown. The emulsion prepared by LTS is unstable and emulsifies rapidly after homogenization. This is a typical characteristic of natural starch granule-stabilized emulsions because the droplets are large. The Pickering emulsion stabilized by LSNPs has fewer emulsifying layers, suggesting insufficient emulsifying ability of LSNPs. However, during long-term storage, there are no significant changes in the emulsification and size distribution of the droplets, indicating that these emulsions are stable in terms of long-term coalescence. The Pickering emulsion prepared by CH / LSNPs has better emulsifying activity and emulsion stability than those prepared by LTS and LSNPs, specifically manifested in its higher emulsifying layer and the smallest change in the height of the emulsifying layer after long-term storage. This is because the smaller particle size and the three-phase contact angle closer to 90° are conducive to the adsorption of CH / LSNPs at the oil-water interface.

[0157] 6. Optical Microscopy Analysis

[0158] A drop of Pickering emulsion was placed on a microscope slide and covered with a coverslip. The microscopic structure images of the Pickering emulsion were observed using an optical microscope equipped with a Leica camera. All measurements were carried out at 25 °C.

[0159] The microscopic structures of the Pickering emulsions prepared by CH / LSNPs, LSNPs, and LTS under the same conditions are as Figure 11 shown. Figure 11 As can be seen from A-F, starch granules accumulate at the oil-water interface and form a dense layer around the oil droplets. The starch granule layer prevents the aggregation of oil droplets. The Pickering emulsion prepared by LTS without nano-modification and hydrophobic modification is unstable ( Figure 11 G-I), and a large amount of droplet aggregation occurs after homogenization, significantly showing a large number of large oil droplets and uneven oil droplet distribution. These observed phenomena are not conducive to the stability of the emulsion. The aggregation of oil droplets and the formation of larger oil droplets easily lead to fat floating and oil separation, which is consistent with the phenomena observed in the emulsion appearance. This is because the particles of natural starch are larger and have too strong hydrophilicity, making it difficult for the particles to adsorb on the droplet surface, and the particles quickly desorb from the oil-water interface after homogenization, resulting in the aggregation of droplets. After nano-modification, the particle size of LSNPs and the particle wettability are enhanced, and the Pickering emulsion prepared by it also shows the formation of smaller oil droplets and more uniform distribution ( Figure 11 D-F), but there are still some particle flocculation and the presence of large-sized droplets. This shows that although the adsorption of LSNPs on the droplet surface has been improved, a dense particle adsorption layer still cannot be formed, that is, the interfacial particle coverage is insufficient. This is due to the relatively high hydrophilicity of LSNPs. The insufficient interfacial particle coverage of LSNPs leads to the flocculation and aggregation of droplets, resulting in the partial polymerization of droplets into large droplets and demulsification. CH / LSNPs has well improved the problem of too strong hydrophilicity of LSNPs and increased the contact angle of the particles to 81.55°.

[0160] 7. CLSM Analysis

[0161] Use a confocal laser scanning microscope to observe the Pickering emulsion droplets stabilized by SNPs and chitosan. Specifically, prepare a mixed dye by mixing equal amounts of Nile red (1 mg / ml), Nile blue A (1 mg / ml), and Rhodamine B (1 mg / ml). Nile red is dissolved in isopropanol, and both Nile blue A and Rhodamine B are dissolved in distilled water. Nile red is used for staining sunflower seed oil, Nile blue A is used for staining SNPs, and Rhodamine B is used for staining chitosan. Mix 1 ml of freshly prepared emulsion with 10 μl of the mixed dye, stir well, and then let it stand at room temperature for 1 hour for staining. Drop a drop of the stained emulsion sample onto the center of a confocal Petri dish. Obtain confocal microscopic images by exciting three laser excitation sources (633 nm for Nile blue A, 488 nm for Nile red, and 561 nm for Rhodamine B).

[0162] Observe by CLSM to determine the adsorption of CH / LSNPs at the oil-water interface. In addition, the internal structure of the Pickering emulsion stabilized by CH / LSNPs can be visually observed by CLSM. The distributions of each LSNPs, oil droplets, and CH are visualized using the fluorescent dyes Nile blue A (blue), Nile red (green), and Rhodamine B (red) respectively ( Figure 12 ). The images clearly show that a purple halo formed by the fusion of red and blue surrounds the green oil droplets, which proves that CH / LSNPs have been uniformly adsorbed onto the droplet surface. Interestingly, the blue layer is not located outside the red layer but completely overlaps, indicating the existence of electrostatic interactions between LSNPs and CH on the droplet surface. This layer on the emulsion droplet surface can serve as a powerful physical barrier, thus contributing to improving the storage stability.

[0163] Example 9

[0164] Preparation of Pickering emulsion of Lipo taro nano starch composite chitosan:

[0165] Fix the volume of sunflower seed oil phase at 30%. Under the condition of the compound of CH and LSNPs with a pH of 4, prepare the chitosan composite Lipo taro starch nanoparticles of Example 7 into dispersion liquids with particle concentrations of 1%, 2%, 3%, 4%, 5%, and 6% respectively, and homogenize and mix them with the oil phase under the condition of high-speed homogenization at 20000 rpm for 2 min to prepare Pickering emulsions with different CH / LSNPs particle concentrations. During the homogenization process, to prevent the emulsion temperature from being too high and affecting subsequent tests, the homogenization is carried out under ice bath conditions.

[0166] Relevant performance tests and result analysis of chitosan composite starch nanoparticle Pickering emulsion 1. Determination of emulsion type

[0167] After preparing the Pickering emulsion, a drop of the emulsion was added dropwise to deionized water or sunflower oil. If it was an oil-in-water emulsion, the droplets would disperse in the aqueous phase and remain intact in sunflower oil; if it was a water-in-oil emulsion, the droplets would remain intact in the aqueous phase and disperse in sunflower oil.

[0168] It was found that when freshly prepared Pickering emulsion was dropped into deionized water and sunflower oil respectively, the droplets dispersed in deionized water and remained intact in sunflower oil, indicating that the prepared Pickering emulsion was an oil-in-water Pickering emulsion.

[0169] 2. Emulsion particle size analysis

[0170] The undiluted emulsion sample was dropped into the instrument sample cell and the sample was continuously ultrasonically dispersed. When the light shielding level reached between 12% and 15%, the particle size distribution of the emulsion was measured. Among them, the dispersion medium was distilled water, the circulation pump speed was 2000 rpm, the refractive index of distilled water was set to 1.333, and the refractive index of the emulsion was set to 1.46.

[0171] The emulsion storage stability (ESS) was expressed by the degree of change in the emulsion particle size within 7 days and was calculated as follows:

[0172]

[0173] Among them, D0 was the D[4,3] value of the freshly prepared emulsion, and D7 was the D[4,3] value of the emulsion after 7 days.

[0174] Under the condition of 30% oil phase volume, the particle size distribution of Pickering emulsions with different CH / LSNPs particle concentrations (1% - 6%) was as Figure 13 shown. With the increase of the CH / LSNPs particle concentration, the particle size distribution of the emulsion became more concentrated, the droplets were more uniform, and the droplet size (D[4,3]) showed a trend of continuous decrease until it became stable.

[0175] When the CH / LSNPs particle concentration was between 1% and 4%, the emulsion showed a multi-peak distribution, with a large-size droplet peak and a small-size droplet peak on both sides of the main peak. The large-size droplet peak might be large droplets formed by droplet aggregation, while the small-size droplet peak might be related to unadsorbed CH / LSNPs particles and nanoscale droplets present in the emulsion. With the increase of the particle concentration, the main peak of the emulsion gradually shifted towards a smaller particle size, and the large-size droplet peak gradually became smaller. When the particle concentration increased to 5%, the large-size droplet peak disappeared, and the main peak became more concentrated, indicating that the emulsion droplet distribution was more uniform. This also showed that with the increase of the particle concentration, the anti-aggregation ability of the Pickering emulsion was improved, and almost no large droplets formed by small droplet aggregation.

[0176] The droplet size of Pickering emulsions was quantitatively characterized using the volume - average diameter (D[4,3]). For freshly prepared Pickering emulsions, their droplet size depends on the external energy input that leads to the initial generation of small - sized droplets, as well as the stability of the droplets against flocculation and re - coalescence after formation. Figure 14 Figure A shows the volume - average diameter (D[4,3]) of the oil droplets in Pickering emulsions with different CH / LSNPs particle concentrations. All particle sizes were measured 3 h after the fresh emulsion preparation. This is because after the emulsion preparation, the newly formed oil droplets may have undergone rapid coalescence within 1 h, and then slowly shrank and aggregated during the 3 - h storage time until the CH / LSNPs coverage was sufficient to stabilize the droplets. All the prepared Pickering emulsions shown in the figure are in the micron scale. At a given oil - phase volume, the droplet size of Pickering emulsions highly depends on the CH / LSNPs particle concentration added to the continuous phase. The high dependence of Pickering emulsion droplet size on particle concentration is generally considered a characteristic of Pickering emulsions, reflecting limited coalescence in the emulsion system. As the CH / LSNPs particle concentration in the system increases, the droplet size of the emulsion decreases, indicating a gradually enhanced stability of the Pickering emulsion. The droplet size of the Pickering emulsion stabilized by 1% CH / LSNPs particles is 304.06 ± 46.21 μm. When the concentration of CH / LSNPs particles is 5%, the droplet size drops to 19.40 ± 2.13 μm. Some previous studies have also observed similar results. They believe that an increase in particle concentration will reduce the droplet size of Pickering emulsions and increase the stability of the emulsion. This may be because more CH / LSNPs particles are available to stabilize smaller oil droplets. When the CH / LSNPs particle concentration increases to 6%, compared with 5%, the droplet size does not change significantly (p>0.05), which is basically consistent with the results of optical microscopy ( Figure 13 ). When the CH / LSNPs particles exceed the particles required for complete coverage, more particles may adsorb to form additional layers or remain dispersed in the continuous phase and aggregate to form a gel structure, and thus the change in emulsion D[4,3] is not obvious. This shows that a 5% CH / LSNPs particle concentration can effectively stabilize Pickering emulsions. When the oil - phase volume is fixed, a smaller average emulsion droplet size results in a larger total interfacial area of the emulsion droplets. It can be inferred that after the emulsion forms small - sized droplets under external energy input, increasing the particle concentration enables the particles to adsorb completely, rapidly, and irreversibly on the surface (oil - water interface) of each small droplet. Therefore, the high interfacial area can be stabilized during the limited coalescence process. Therefore, when the oil - phase volume is fixed and the particle concentration increases within a certain range, CH / LSNPs Pickering emulsions tend to have small emulsion droplets.

[0177] 3. Emulsion microstructure

[0178] A drop of Pickering emulsion was placed on a microscope slide and covered with a coverslip. The microscopic structure image of the Pickering emulsion was observed using an optical microscope equipped with a Leica camera. All measurements were carried out at 25 °C.

[0179] The microscopic structures of Pickering emulsions with different CH / LSNPs particle concentrations (1% - 6%) photographed by an optical microscope are as Figure 13 shown. The CH / LSNPs concentration has an obvious effect on the size of the emulsified oil droplets. The results of the emulsion microscopic structure show that with the increase of the particle concentration, the emulsion droplets are smaller and more uniform, and the packing between the droplets is tighter.

[0180] Specifically, compared with the samples with higher particle concentrations (>3%), the samples with low CH / LSNPs concentrations (1%, 2% and 3%) seem to have larger droplet sizes and there are many non-uniform large-sized droplets. These observation results are in good agreement with the results of the droplet size distribution determined by static light scattering experiments. There are very few CH / LSNPs particles at the oil-water interface in the Pickering emulsion sample stabilized by 1% CH / LSNPs particles. However, as the particle concentration increases from 1% to 6%, the starch particles at the oil-water interface become denser. This is because the Pickering emulsion system with high CH / LSNPs particle concentration has a stable network structure, which can inhibit the aggregation of oil droplets. In the Pickering emulsion system with low CH / LSNPs particle concentration, the particle concentration available for adsorption during the emulsification process may be limited, and a closely packed particle layer with complete monolayer coverage required for emulsion stability cannot be formed. The result is the formation of dispersed droplets with reduced surface coverage, and an effective physical barrier cannot be formed on the surface of these droplets, making them unstable in terms of bridging flocculation and coalescence. Therefore, the Pickering emulsion is more stable at high CH / LSNPs particle concentrations than at low CH / LSNPs particle concentrations. The CH / LSNPs nanoparticles rapidly assemble and adsorb at the newly formed oil-water interface, reducing the interfacial tension and rapidly stabilizing the small oil droplets formed under the input of external energy, which is beneficial to the formation of a stable emulsion. Combining the analysis of CLSM in the previous text, it is obvious that the adsorption of CH / LSNPs particles on the surface of oil droplets and the formation of a gel-like network structure between the particles endow it with the ability to stabilize oil-in-water emulsions.

[0181] 4. Determination of Emulsification Index

[0182] The emulsification index (EI) is an index to measure the separation process of droplets due to flocculation and coalescence under buoyancy movement. Usually, the emulsification index (EI) of Pickering emulsion is determined by visual observation method. Specifically, the apparent pictures of the prepared Pickering emulsion are photographed with a digital camera, and the pictures of the samples are analyzed to determine the height of the emulsified layer (the white emulsion layer) and the total height of the emulsion of the samples. The following formula is used for calculation to obtain the EI (%) value of the samples:

[0183]

[0184] Among them, H e is the height of the emulsion layer, and H t is the total height of the emulsion.

[0185] Creaming is a phenomenon reflecting the instability of oil-in-water Pickering emulsions, which originates from the gravitational and density differences between the two liquids in the emulsion. Figure 14 B and Figure 15 respectively show the emulsification index (EI) of the CH / LSNPs emulsion within 7 days of storage and the appearance of the emulsion after 7 days of storage. The EI at 0 Day corresponds to the freshly prepared Pickering emulsion. The change in the emulsification index was measured within 7 days by directly observing the separation of the emulsion in the glass bottle. Samples with different particle concentrations showed varying degrees of creaming over time, specifically manifested as a decrease in the EI value of the emulsion. However, as the particle concentration increased, the degree of change in the EI value of the Pickering emulsion over time became smaller.

[0186] In the emulsion samples with CH / LSNPs particle concentrations of 5% and 6%, the EI value of the emulsion remained at a constant value of approximately 100% after 7 days. In the emulsion sample with a CH / LSNPs particle concentration of 4%, obvious stratification was observed on the third day after preparation, and the stratification phenomenon tended to stabilize after the 5th day. The EI value after 7 days was 91.11%. For the Pickering emulsion with a low CH / LSNPs particle concentration, rapid stratification was observed on the first day after preparation, and the stratification trend tended to balance after the 5th day, with the EI value reaching a minimum of 55.56%. The changing trend of the EI value of different samples over time indicates that the emulsion samples with CH / LSNPs particle concentrations of 5% and 6% have a higher ability to resist the creaming phase separation caused by gravitational separation and a stronger ability to form stable emulsions.

[0187] Although obvious creaming stratification was observed in the Pickering emulsion prepared with a low particle concentration, no separate oil phase layer caused by oil separation was observed at the top of all emulsion samples ( Figure 15 ). The non - coalescence of oil droplets over time during subsequent storage also coincides with the result that the EI tended to be stable ( Figure 14 B). Even after storing for six months under ambient conditions, no separate oil phase was detected (not shown in the figure). This shows that low - concentration CH / LSNPs particles reduce the total area of the oil - water interface through partial aggregation of droplets, making it sufficient to form a monolayer of closely packed particles covering the droplet surface. After forming a particle layer that serves as an effective physical barrier, the extensive coalescence of dispersed droplets and subsequent phase separation are prevented. It should be noted that the lower layer of all samples with obvious creaming phenomenon is very turbid, indicating that many CH / LSNPs particles did not participate in the stabilization of emulsion droplets and are still dispersed in the aqueous phase. This is consistent with the emulsion particle size distribution diagram ( Figure 13) A peak at a smaller particle size was observed to coincide. Although the particle size distribution diagrams of the emulsion samples with CH / LSNPs particle concentrations of 5% and 6% also showed a peak at a smaller particle size, the CH / LSNPs particles that might be dispersed in the aqueous phase could link the droplets through a network structure, enabling the droplets dispersed in the emulsion to form a stable droplet network structure. Therefore, no obvious creaming phenomenon was observed during storage.

[0188] 5. Rheological Property Measurement

[0189] Rheological measurements were immediately carried out on the emulsion in a rheometer after its preparation, and the rheological behavior of the Pickering emulsion was analyzed using TA data analysis software. Briefly, the sample was evenly spread on a circular stainless steel plate geometric measurement cell (40 mm in diameter) with a dropper, and the height of the upper and lower plate gap was set to 1 mm. For the dynamic test, at 25 °C, the sample was subjected to a frequency sweep at a fixed strain of 1% in the frequency range of 0.1 to 10 Hz (within the linear elastic region) to determine the storage modulus (G') and loss modulus (G") of the sample. For the static test, the apparent viscosity of the Pickering emulsion sample was measured at 25 °C with the shear rate set from 0.01 to 300 s-1 to study the variation of the sample's apparent viscosity with the shear rate.

[0190] The variation of the emulsion's apparent viscosity with the shear rate is as Figure 16As shown in A, except for the emulsion sample with a CH / LSNPs particle concentration of 1%, the viscosity of all other emulsion samples decreased with the increase in shear rate (0–300 s-1). The emulsion exhibited non-Newtonian pseudoplastic behavior (shear thinning) that conforms to the Herschel-Bulkley model, reflecting that the increasing shear force disrupted the flocculation network structure formed between emulsion droplets due to weak hydrogen bond forces. The results showed that Pickering emulsions prepared with CH / LSNPs particle concentrations of 2%–6% formed a weak droplet network structure. The emulsion sample with a CH / LSNPs particle concentration of 1% showed Newtonian fluid-like behavior throughout the shear rate range. This indicates that within the shear rate range of 0-300 s-1, when the CH / LSNPs particle concentration increased from 1% to 2%, the emulsion underwent a transition from Newtonian fluid behavior to non-Newtonian fluid pseudoplastic behavior. At the same time, it was also observed that when the CH / LSNPs particle concentration increased from 1% to 6%, the apparent viscosity of the emulsion continuously increased. This is because when the CH / LSNPs particle concentration increases, the oil-water interfaces that can be stabilized by the particles in the emulsion system increase, and more small droplets formed during the homogenization process can be stabilized. The contact area of the dispersed droplets in the system increases, resulting in an increase in the apparent viscosity of the system. As the particle adsorption layer sufficient to form a saturated close-packed layer on the droplet surface, when the particle concentration continues to increase (from a CH / LSNPs particle concentration of 5% to 6%), there will be an excess of particles in the continuous phase. These particles form more network structures between the droplets, strengthening the flocculation network structure between the droplets and further increasing the apparent viscosity of the system, forming a gel-like network structure with poor fluidity. A reasonable explanation for this is that increasing the content of modified starch thickens the water phase, forms a film around the oil droplets, and prevents the oil droplets from aggregating, thereby improving the intramolecular and intermolecular interactions in the emulsion system and reducing the fluidity of the oil droplets. In addition, it was also observed that the increase in the apparent viscosity of the emulsion sample was positively correlated with the EI value, which also well explained why the emulsion samples with CH / LSNPs particle concentrations of 5% and 6% showed good emulsion stability.

[0191] The dependence of the storage and loss moduli (G′, G″) of the emulsion on frequency was analyzed through dynamic frequency tests. G′ represents the energy stored in the material or the magnitude of the energy that can be recovered per deformation cycle. While G″ represents the energy lost as viscous dissipation per deformation cycle. A dynamic frequency scanning experiment was carried out in the frequency range of 0.1 to 10 Hz, and the data obtained are as Figure 16As shown in B. The storage modulus of Pickering emulsions stabilized by different particle concentrations of CH / LSNPs is always higher than its loss modulus in the frequency range of 0.1 to 10 Hz, indicating that its elastic behavior is superior to its viscous behavior. With the increase of particle concentration, the Pickering emulsion of CH / LSNPs shows higher storage modulus (G′) and loss modulus (G″). After the particle concentration is greater than 2%, the frequency dependence of G′ is weak, indicating the enhancement of the emulsion gel network structure. This is because a stronger intermolecular interaction is formed by a high concentration of CH / LSNPs in the Pickering emulsion system, thus enhancing the compactness of the elastic gel network structure and increasing the stability of the system.

[0192] Finally, it should be emphasized that the above-mentioned implementation cases are only highly representative examples shown in this application. Undoubtedly, the technical concepts covered by this application are far more than these specific embodiments, and its boundaries are broad, accommodating many variations and innovations. Therefore, any various deformations and improvements that can be directly deduced or reasonably associated by those skilled in the art based on the information disclosed in this application should all be regarded as falling within the protection scope of this application without exception.

Claims

1. A preparation method of chitosan composite Lipu taro starch nanoparticles, characterized in that, Specifically, it includes the following steps: (1) Preparation of Lipu taro starch: Grind Lipu taro in a plant tissue crusher; Screen the obtained slurry, and then settle the filtrate in an ice bath; After settlement, pour out the upper-layer purplish-red liquid, and re-stir the precipitate and suspend it in distilled water; Adjust the pH of the mixture to 10 by adding NaOH solution, and keep stirring; Subsequently, neutralize it to pH 7 with HCl solution, centrifuge, remove the supernatant, scrape off the upper-layer yellow impurities to collect the precipitate; Re-stir the precipitate and suspend it in distilled water, and centrifuge; Finally, dry the precipitate, grind it into powder, pass it through a 120-mesh sieve, store the starch in a sample bag, and code the obtained powder as LTS for subsequent analysis; (2) Preparation of Lipu taro nano-starch particles: Prepare a starch suspension, and keep stirring in a boiling water bath until the starch is completely gelatinized; After ultrasonic treatment of the gelatinized starch, gradually add it dropwise to an ethanol solution under continuous stirring, and prepare Lipu taro starch nanoparticles LSNPs by anti-solvent precipitation method; After stirring the solution, centrifuge it, and discard the supernatant to obtain LSNPs; Wash the LSNPs with absolute ethanol to remove the excess water, and obtain dry LSNPs after freeze-drying; (3) Preparation of Lipu taro starch nanoparticle composite chitosan: Dissolve chitosan (CH) in acetic acid solution, stir overnight at room temperature to ensure complete dissolution, and prepare a 1wt% chitosan solution; Dissolve LSNPs in distilled water, and keep magnetic stirring until completely dispersed to form an LSNPs stock solution; Subsequently, add the chitosan solution to the LSNPs stock solution to adjust the pH, and keep magnetic stirring to form a mixed solution of LSNPs:CH.

2. The preparation method of the chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, In the step (1), when grinding Lipu taro in a plant tissue crusher, specifically, it is ground with distilled water at a solid-liquid ratio of 1:3 for 2 minutes.

3. The preparation method of the chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, The screening in the step (1) is successively through 60-mesh and 120-mesh sieves.

4. The preparation method of chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, In the step (1), when re-stirring the precipitate and suspending it in distilled water, specifically, the precipitate is re-suspended in distilled water at a solid-liquid ratio of 1:

3.

5. The preparation method of the chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, The centrifugation in the step (1) is specifically centrifugation at 1200×g for 15 minutes.

6. The preparation method of the chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, In the step (2), after stirring the solution and then centrifuging, specifically, after stirring the solution at room temperature for 10 min, centrifuge it at 8000 rpm for 10 min.

7. The preparation method of the chitosan composite Lipu taro starch nanoparticles according to claim 1, characterized in that, In the step (2), when washing the LSNPs with absolute ethanol to remove the excess water and obtaining dry LSNPs after freeze-drying, specifically, the LSNPs are washed with absolute ethanol at least 3 times to remove the excess water, pre-frozen at -18°C for 12 h, and then vacuum freeze-dried for 48 h to obtain dry LSNPs.

8. A chitosan composite Lipu taro starch nanoparticle, characterized in that, Prepared by the method according to any one of claims 1-7.

9. Use of the chitosan composite Lipu taro starch nanoparticles according to claim 8 in the preparation of emulsions.

10. A chitosan composite starch nanoparticle Pickering emulsion, characterized in that, Prepared by using the chitosan composite Lipu taro starch nanoparticles according to claim 8.

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