Lipu taro starch-based Pickering emulsion as well as preparation method and application thereof

Abstract

The invention relates to the technical field of starch, and provides a chitosan composite Lipu taro nano starch particle Pickering emulsion with high storage stability through green modification preparation. The highest loading rate of the curcumin loaded on the emulsion is 97.22%, and the stability of the emulsion is not affected by small particle size; after 5h of ultraviolet radiation, the highest residual rate of curcumin in an emulsion loaded sample is 82.22%, and a relatively good protection effect is shown; after heat treatment in a water bath at 37 DEG C for 4 hours, the retention rate of curcumin in an emulsion-loaded sample is 85% or above, and the retention rate after high-temperature treatment can still reach 80% or above; after the chitosan composite Lipu taro nano starch particle emulsion is stored for 30 days, the retention rate of the chitosan composite Lipu taro nano starch particle emulsion loaded curcumin can reach 79.66%-82.01%. The Lipu taro starch-based emulsion is simple in preparation condition, green, environment-friendly, high in stability and good in fat-soluble active substance load protection effect, and the application range of the starch-based emulsion is widened.

Description

Technical Field

[0001] This application relates to the technical field of starch, and specifically relates to a Lipu taro starch-based Pickering emulsion, its preparation method and application Background Art

[0002] An emulsion is a system that exists in a thermodynamically unstable state because there are two immiscible liquids in the emulsion system. One of the liquids (such as oil) is dispersed in the other liquid (such as water) in the form of countless small droplets. Due to the huge number of small droplets, a huge two-phase interface is generated, which has a high interfacial free energy. The small droplets tend to spontaneously aggregate and fuse, resulting in emulsion stratification and instability

[0003] Traditional emulsions made using small molecule surfactants do not meet the requirements of the "clean label" in the food industry. Currently, the food industry has been working hard to replace many synthetic surfactants with natural ingredients such as starch. Currently, novel Pickering emulsions constructed using food-grade materials with high biodegradability and biocompatibility from biological sources are emerging emulsion types with very good development prospects due to their many advantages such as high stability, high biocompatibility, environmental friendliness, low cost, and easy preparation

[0004] Lipu taro starch has small particles (2-3 μm), an irregular polygonal particle structure, and a relatively rough surface, showing excellent emulsifying properties. There is almost no research on the preparation of Pickering emulsions using Lipu taro starch

[0005] Therefore, exploring the ultraviolet protection, thermal protection, storage stability and other protection characteristics of Lipu taro nano-starch composite chitosan Pickering emulsion for curcumin, and preparing a starch-based emulsion with high stability, high loading rate of fat-soluble active substances and good protection characteristics, is the current key research direction Summary of the Invention

[0006] In order to solve the above technical problems existing in the prior art, this application provides a Lipu taro starch-based Pickering emulsion, its preparation method and application

[0007] A preparation method of a Lipu taro starch-based Pickering emulsion, characterized in that it specifically includes the following steps

[0008] Take the prepared chitosan composite nano-starch particles, and prepare a dispersion with an oil phase volume fraction of 20%-70% under the compounding conditions of a chitosan composite nano-starch particle concentration of 1% to 6% and a pH of 2 to 8. After homogenizing and mixing the dispersion, a Pickering emulsion is obtained

[0009] Further, the concentration of the chitosan composite nano-starch particles is 3%

[0010] Further, the pH is 4

[0011] Furthermore, the volume fraction of the sunflower seed oil in the oil phase is 40%.

[0012] Furthermore, the homogeneous mixing is specifically carried out under the high-speed homogenization condition of 20,000 rpm for 2 minutes.

[0013] Furthermore, the oil phase is sunflower seed oil.

[0014] Furthermore, the environmental pH value of the emulsion can also be adjusted with 2M HCl or NaOH to prepare an emulsion with a specific pH (pH 2 - 10).

[0015] Furthermore, the environmental ionic strength of the emulsion can also be adjusted with NaCl powder to prepare an emulsion with a specific ionic strength (0 - 0.5M).

[0016] Furthermore, the emulsion can also be treated in a boiling water bath to prepare a heat-treated emulsion.

[0017] Furthermore, the chitosan composite nano starch particles are prepared by the following method:

[0018] (1) Preparation of Lipu taro starch: Lipu taro is ground in a plant tissue crusher; the obtained slurry is screened, and then the filtrate is sedimented in an ice bath; after sedimentation, the upper purple-red liquid is poured off, and the precipitate is re-stirred and suspended in distilled water; the pH of the mixture is adjusted to 10 by adding NaOH solution and continuously stirred; subsequently, it is neutralized to pH 7 with HCl solution, centrifuged, the supernatant is removed, and the upper yellow impurities are scraped off to collect the precipitate; the precipitate is re-stirred and suspended in distilled water and centrifuged; finally, the precipitate is dried, ground into powder, passed through a 120-mesh sieve, and the starch is stored in a sample bag. The obtained powder is coded as LTS and used for subsequent analysis;

[0019] (2) Preparation of Lipu taro nano starch particles: Prepare a starch suspension, and continuously stir it in a boiling water bath until the starch is completely gelatinized; after the gelatinized starch is ultrasonically treated, it is gradually added dropwise to an ethanol solution that is continuously stirred, and Lipu taro starch nanoparticles LSNPs are prepared by the anti-solvent precipitation method; after the solution is stirred and centrifuged, the supernatant is discarded to obtain LSNPs; LSNPs are washed with absolute ethanol to remove excess water and freeze-dried to obtain dry LSNPs;

[0020] (3) Preparation of Litchi taro starch nanoparticles composite chitosan: Dissolve chitosan (CH) in acetic acid solution and stir overnight at room temperature to ensure complete dissolution, and prepare a 1 wt% 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.

[0021] Furthermore, in step (1), the Litchi taro is ground in a plant tissue crusher, specifically, it is ground with distilled water at a solid-liquid ratio of 1:3 for 2 minutes.

[0022] Furthermore, the sieving in step (1) is carried out through 60-mesh and 120-mesh sieves in sequence.

[0023] Furthermore, the sedimentation in step (1) is carried out for 12 hours to prevent deterioration.

[0024] Furthermore, in step (1), the precipitate is re-stirred and suspended in distilled water, specifically, the precipitate is re-suspended in distilled water at a solid-liquid ratio of 1:3.

[0025] Furthermore, in step (1), the concentration of the NaOH solution is 1 mol / L; the concentration of the HCl solution is 1 mol / L.

[0026] Furthermore, the centrifugation in step (1) is specifically carried out at 1200×g for 15 minutes.

[0027] Furthermore, the drying in step (1) is carried out at 45 °C for 48 hours.

[0028] Furthermore, the step of "re-stirring and suspending the precipitate in distilled water and centrifuging" in step (1) is repeated at least 3 times to ensure that the supernatant is clear and transparent and there are no obvious impurities on the upper layer of the precipitate.

[0029] Furthermore, the centrifugation after stirring the solution in step (2) is specifically carried out by stirring the solution at room temperature for 10 min and then centrifuging at 8000 rpm for 10 min.

[0030] Furthermore, the LSNPs in step (2) are washed with absolute ethanol to remove excess water, and dried LSNPs are obtained after freeze-drying. Specifically, the LSNPs are washed with absolute ethanol at least 3 times to remove excess water, pre-frozen at -18 °C for 12 h, and then vacuum freeze-dried for 48 h to obtain dried LSNPs.

[0031] Furthermore, the acetic acid solution in step (3) is a 1% (v / v) acetic acid solution.

[0032] A Lipu taro starch-based Pickering emulsion is prepared by the above method.

[0033] The prepared Lipu taro starch-based Pickering emulsion can be applied in protecting lipophilic active substances, and can be applied to the protection of lipophilic antioxidants or lipophilic pigments, such as being used as a protective agent.

[0034] A protective agent for lipophilic active substances is prepared by using the above Lipu taro starch-based Pickering emulsion.

[0035] Compared with the prior art, the technical effects of the present application are reflected in:

[0036] (1) In the present invention, through a green composite modification method, relatively hydrophobic Lipu taro starch nanoparticles are prepared to optimize the process for preparing a starch-based Pickering emulsion with hydrophobic Lipu taro nanoparticles, and a new type of starch-based Pickering emulsion that is green, non-toxic and harmless is developed. Curcumin, as a classic representative of lipophilic bioactive substances, is loaded by using the chitosan nano-starch particle emulsion prepared by green modification, and the loading application of the Lipu taro starch-based emulsion to lipophilic active substances is explored.

[0037] (2) The present invention provides a chitosan composite Lipu taro nano-starch particle Pickering emulsion with high storage stability through green modification. The effects of pH, ion concentration, and heat treatment on the stability of the emulsion are discussed, and the influence of possible application environments on the stability of the emulsion is provided. The preparation conditions of this emulsion are simple, green and environmentally friendly, with high stability, increasing the application range of the starch-based emulsion.

[0038] (3) For the emulsion prepared in the present invention, the highest loading rate of the lipophilic active substance curcumin is 97.22%, and the particle size is small without affecting the stability of the emulsion; after 5 hours of ultraviolet irradiation, the highest residual rate of curcumin in the emulsion-loaded sample is 82.22%, showing a good protective effect; after heat treatment in a 37°C water bath for 4 hours, the retention rate of curcumin in the emulsion-loaded sample is above 85%, and the retention rate after high-temperature treatment can still reach above 80%; after storage for 30 days, the retention rate of curcumin loaded by the chitosan composite Lipu taro nano-starch particle emulsion can reach 79.66%-82.01%. The Lipu taro starch-based emulsion has simple preparation conditions, is green and environmentally friendly, has high stability, and has a good protective effect on the loading of lipophilic active substances, increasing the application range of the starch-based emulsion. Description of the Drawings

[0039] Figure 1 It is the microstructure and particle size distribution of Pickering emulsions with different oil phase volumes.

[0040] Figure 2 It is the influence of different oil phase volumes on the particle size (A) and EI value (B) of the Pickering emulsion stored for 7 days.

[0041] Figure 3 are the appearances of Pickering emulsions with different oil phase volumes.

[0042] Figure 4 are the effects of different oil phase volumes on the apparent viscosity (A), storage modulus G', and loss modulus G" (B) of Pickering emulsions.

[0043] Figure 5 are the changes in D[4,3] and EI values of emulsion D under different environmental pHs and storage times (A).

[0044] Figure 6 are the effects of different environmental pH values on the microstructure of emulsions.

[0045] Figure 7 are the changes in D[4,3] and EI values of emulsions under different ionic strengths and storage times.

[0046] Figure 8 are the effects of different ionic strengths on the microstructure of emulsions.

[0047] Figure 9 are the changes in D[4,3] and EI values of emulsions under different boiling water bath treatment times and storage times.

[0048] Figure 10 are the curcumin loading rates of different curcumin-loaded emulsion samples.

[0049] Figure 11 are the protection characteristics of different curcumin-loaded samples for curcumin under ultraviolet irradiation.

[0050] Figure 12 are the retention rates of curcumin in different curcumin-loaded samples after different heat treatments.

[0051] Figure 13 are the storage stabilities of different curcumin-loaded samples. Specific Embodiments

[0052] The technical solutions of the present application will be further limited below in combination with specific embodiments, but the scope of protection required is not limited only to the description made.

[0053] The experimental methods in the following examples are all conventional methods unless otherwise specified; the biological and chemical reagents used are all conventional reagents in the art unless otherwise specified.

[0054] Preparation method of Lipu taro nano-starch of the present invention: Prepare a starch suspension with a concentration of 4% w / v, continuously stir it in a boiling water bath for 30 min to ensure complete gelatinization of the starch. After the gelatinized starch is treated by ultrasound for 50 min, it is gradually added dropwise into an ethanol solution (alcohol-water ratio 1:1) under continuous stirring, and starch nanoparticles (SNPs) 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 SNPs. The SNPs are washed 3 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 SNPs.

[0055] Preparation method of chitosan composite Lipu taro nano-starch particles of the present invention: Dissolve chitosan (CH) in a 1% (v / v) acetic acid solution, stir it 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, a certain amount of chitosan solution is added to the SNPs stock solution (LSNPs:CH = 1:0.0885), the pH is adjusted to 4, and it is continuously stirred magnetically to form a mixed solution of LSNPs:CH.

[0056] Example 1:

[0057] The preparation method of chitosan composite nano-starch particle Pickering emulsion is as follows:

[0058] ① Configure a suspension with a chitosan composite nano-starch particle concentration of 3% and a compounding condition with a pH adjusted to 4;

[0059] ② Respectively prepare sunflower seed oil with oil phase volume fractions of 20%, 30%, 40%, 50%, 60% and 70%, and homogenize and mix it with the CH / LSNPs particle dispersion liquid under the high-speed homogenization condition of 20000 rpm for 2 min to prepare Pickering emulsions with different sunflower seed oil phase volumes. During the homogenization process, in order to prevent the emulsion temperature from being too high and affecting subsequent tests, the homogenization is carried out under ice bath conditions.

[0060] Example 2:

[0061] The preparation method of chitosan composite nano-starch particle Pickering emulsion is as follows:

[0062] ① Configure a suspension with a chitosan composite nano-starch particle concentration of 5%, a compounding condition with pH = 4, and a formula condition with an oil phase volume of 40%, and homogenize and mix it under the high-speed homogenization condition of 20000 rpm for 2 min to prepare a Pickering emulsion;

[0063] ② 10 mL of freshly prepared emulsion was taken respectively, and the environmental pH value of the emulsion was adjusted with 2 M HCl or NaOH to prepare emulsions with pH = 2, 4, 5, 6, 7, 8 and 10.

[0064] Example 3:

[0065] The preparation method of the chitosan composite nano-starch particle Pickering emulsion is as follows:

[0066] ① A suspension with a chitosan composite nano-starch particle concentration of 5% was prepared, and under the compounding condition of pH = 4 and the high-speed homogenization condition of 20,000 rpm under the formula condition of 40% oil phase volume, it was homogenized and mixed for 2 min to prepare the Pickering emulsion;

[0067] ② 10 mL of freshly prepared emulsion was taken respectively, and the environmental ionic strength of the emulsion was adjusted with NaCl powder to prepare emulsions with ionic strengths of 0, 0.1 M, 0.2 M, 0.3 M, 0.4 M and 0.5 M.

[0068] Example 4:

[0069] The preparation method of the chitosan composite nano-starch particle Pickering emulsion is as follows:

[0070] ① A suspension with a chitosan composite nano-starch particle concentration of 5% was prepared, and under the compounding condition of pH = 4 and the high-speed homogenization condition of 20,000 rpm under the formula condition of 40% oil phase volume, it was homogenized and mixed for 2 min to prepare the Pickering emulsion;

[0071] ② 10 mL of freshly prepared emulsion was taken respectively, and it was treated in a boiling water bath for 0, 1, 2, 3, 4 and 5 min to prepare emulsions with different heat treatment times.

[0072] Testing method:

[0073] (1) Detection of emulsion type

[0074] After the Pickering emulsion was prepared, a drop of the emulsion was dropped into deionized water or sunflower oil. If it was an oil-in-water emulsion, the droplets would disperse in the water phase and remain intact in the sunflower oil; if it was a water-in-oil emulsion, the droplets would remain intact in the water phase and disperse in the sunflower oil.

[0075] When the freshly prepared Pickering emulsions of Example 1, Example 2, Example 3 and Example 4 were respectively dropped into deionized water and sunflower oil, it was found that 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.

[0076] (2) Detection of emulsion particle size

[0077] The particle size of the emulsion was measured by a laser particle size analyzer, and the results were expressed as D[4,3] values. 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 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.

[0078] 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:

[0079]

[0080] where 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.

[0081] Figure 1 、 Figure 2 A shows the particle size distribution and average particle size of Pickering emulsions with different sunflower oil phase volumes (20% - 50%) under the condition of a CH / LSNPs particle concentration of 3%. Since stable Pickering emulsions could not be formed under the condition of a 3% particle concentration when the oil phase volume increased to 60% and 70%, the particle size distribution diagrams and emulsion microstructure diagrams of Pickering emulsion samples with oil phase volumes of 60% and 70% were not placed in the figure. With the increase in the oil phase volume, the particle size distribution of the emulsion became more dispersed, the droplet peak at larger particle sizes continuously increased, and the droplet size (D[4,3]) showed an increasing trend. It can be observed from the figure that all the particle size distribution diagrams showed a multi-peak distribution. Among them, the droplet peaks at larger particle sizes in the particle size distribution diagrams of samples with oil phase volumes of 20% and 30% were smaller. As the oil phase volume further increased, the droplet peaks at larger particle sizes increased accordingly. When it increased to the sample with an oil phase volume of 50%, a new and even larger droplet peak was even observed. Regardless of the change in the oil phase volume, the droplet peaks at smaller particle sizes remained almost unchanged, indicating that there were unadsorbed nanoparticles or droplets with extremely small sizes in all samples.

[0082] (3) Observe the microstructure of the emulsion

[0083] A drop of Pickering emulsion was placed on a microscope slide and covered with a cover slip. The microstructure image of the Pickering emulsion was observed using an optical microscope equipped with a Leica camera. All measurements were carried out at 25°C.

[0084] The microstructures of Pickering emulsions with different oil phase volumes (20% - 50%) are as Figure 1As shown, the droplet sizes of all emulsions range from a few micrometers to 100 micrometers. It can be seen from the optical microscope photos that increasing the oil phase volume from 20% to 30% has no obvious effect on the size of the emulsified oil droplets, which is consistent with the observed results of the emulsion particle size. When the oil phase volume is further increased to 50%, the large-sized droplets in the system gradually increase, the interfacial area significantly decreases, but the range of the continuous phase in the system gradually becomes smaller, and the interconnections between droplets increase and become closer.

[0085] (4) Emulsion index detection

[0086] The emulsion index (EI) is an indicator to measure the separation process of droplets due to flocculation and coalescence under buoyancy motion. Usually, the emulsion index (EI) of Pickering emulsions is determined by the visual observation method. Specifically, a digital camera is used to take pictures to record the apparent pictures of the prepared Pickering emulsions, 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:

[0087]

[0088] where, H e is the height of the emulsified layer, and H t is the total height of the emulsion.

[0089] Figure 2 It can be seen from B the differences in the changes of the emulsion index of CH / LSNPs Pickering emulsions under different oil phase volume conditions within 7 days of storage. As the oil phase volume increases from 20% to 50%, the emulsion stability improves, and the degree of change of the emulsion EI value with time decreases. However, when the oil phase volume increases to 60%, a large amount of oil phase precipitates from the emulsion, and a stable Pickering emulsion cannot be formed.

[0090] When the oil phase volume is 20% and 30%, the emulsion is observed to quickly separate into two layers on the first day after preparation: the upper emulsified layer and the lower serum layer, and gradually reach an equilibrium state within 7 days. This indicates that the droplets in these emulsion systems show a high tendency of flocculation

[188] ; when the oil phase volume is 40%, the emulsion stratification increases slowly with the passage of storage time and reaches equilibrium on the 5th day; when the oil phase volume is 50%, the emulsion is very stable and almost no fat floating phenomenon occurs. The Pickering emulsions prepared with a higher oil phase volume show better emulsion stability. This shows that at a certain particle concentration, within the range of oil phase volume that can form a stable Pickering emulsion at this particle concentration, increasing the oil phase volume can significantly improve the ability of Pickering emulsions to resist gravity separation and stratification and enhance their stability.

[0091] Figure 3The emulsion appearance of emulsions stabilized by 3% CH / LSNPs particle concentration with different oil-phase volumes (20%–70%) is shown. When the oil-phase volume is further increased to 60% and 70%, exceeding the critical oil-phase volume, a large amount of oil phase precipitates. In addition, a very turbid serum layer is also observed in the stratified emulsion, indicating that many CH / LSNPs particles do not participate in the stabilization of emulsion droplets and remain dispersed in the aqueous phase.

[0092] (5) Rheological property measurement

[0093] Rheological measurements were immediately carried out on the Pickering emulsions in a rheometer after emulsion preparation, and the rheological behavior of the Pickering emulsions was analyzed using TA data analysis software. Briefly, the sample was evenly spread on a circular stainless-steel plate geometric measurement cell (diameter 40 mm) with a dropper, and the height of the upper and lower plate gap was set to 1 mm. For dynamic tests, 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 static tests, at 25 °C and with the shear rate set from 0.01 to 300 s−1, the apparent viscosity of the Pickering emulsion sample was measured to study the variation of the sample apparent viscosity with the shear rate.

[0094] Figure 4 The static rheological properties (A) and dynamic rheological properties (B) of CH / LSNPs Pickering emulsions with different oil-phase volumes are shown respectively. These correspond to their flow properties and viscoelastic properties respectively. The static rheological results show that as the oil-phase volume increases from 20% to 50%, the emulsion samples all exhibit non-Newtonian fluid pseudoplastic behavior and the apparent viscosity continuously increases. The dynamic rheological results show that the emulsion samples have an elastic gel network structure, and as the oil-phase volume increases from 20% to 50%, the stability of the emulsion elastic gel network system is improved.

[0095] (6) Influence of different pH environmental conditions on Pickering emulsions

[0096] Figure 5 The changes in the average particle size and EI value of Pickering emulsions stabilized by CH / LSNPs over a storage period of up to 7 days under different environmental pH conditions are shown. The initial droplet size of the emulsion shows a trend of first decreasing and then increasing as the pH value increases from 2 to 10, reaching a minimum value at pH 5. A similar situation is also observed for the EI value of the emulsion, where no obvious stratification phenomenon is observed in the samples with pH 4 and 5 after 7 days of storage, and the EI value is close to 100%; a small amount of creaming phenomenon is observed in the samples with pH 2, 8, and 10 after 7 days, and the EI values all exceed 90%; while obvious creaming phenomena are observed in the samples with pH 6 and 7, with obvious stratification, and the EI values of the emulsions after 7 days of storage are approximately 82% and 76% respectively.

[0097] According to Figure 6 It can be seen that with the increase of storage time, the emulsion droplet sizes of all samples increase, indicating that over time, the particles at the oil-water interface of the droplets undergo a certain degree of rearrangement to reach a relatively stable state. However, larger changes in droplet size within 7 days were observed in the samples with pH values of 6 and 7, while a smaller trend of droplet size increase was observed in the samples with initial larger droplet sizes at pH values of 8 and 10.

[0098] (7) Influence of different ionic strength conditions on Pickering emulsions

[0099] Figure 7 shows the changes in the average droplet size and EI value of the emulsion after 7 days of storage under different ionic strength conditions. With the continuous increase of ionic strength, the average diameter of the emulsion droplets initially increases from about 20 μm to about 360 μm and then gradually levels off. When the NaCl concentration reaches 0.5 M, the average emulsion droplet diameter reaches 371.1 μm. This is consistent with the results observed in the microscopic structure diagram of the emulsion ( Figure 8 ).

[0100] The decrease in the EI value after 1 day of storage also indicates that rapid creaming and stratification occur in the emulsion after adding NaCl. All these results show that the increase in ionic strength is not conducive to the stability of the CH / LSNPs emulsion. In addition, it is observed that the sample with an ionic strength of 0.1 M in the emulsion system shows a smaller average droplet size of 70.81 μm, and the average droplet size and EI value change less within 7 days, suggesting that the emulsion can maintain good stability in a system environment with an ionic strength not greater than 0.1 M.

[0101] (8) Influence of different heat treatments on Pickering emulsions

[0102] The influence of different heat treatments on the average droplet size and EI value of Pickering emulsions stabilized by CH / LSNPs particles is as Figure 9 shown. Since a stable Pickering emulsion cannot be formed after the boiling water bath time exceeds 3 min, the droplet sizes and EI of these samples are excluded. The results show that heat treatment in a boiling water bath is not conducive to the stability of CH / LSNPs Pickering emulsions, but has little effect on the emulsion stability within 1 min of boiling water bath time.

[0103] Example 5: Preparation of curcumin-loaded Pickering emulsions

[0104] ① Weigh curcumin and add it to sunflower oil to prepare a mixed solution with a mass concentration of 0.2%;

[0105] ② After magnetic stirring of the mixture for 24 h to ensure the full dissolution of curcumin, centrifuge at 4000 rpm for 10 min, collect the supernatant, and remove the undissolved curcumin to obtain the oil phase of the Pickering emulsion loaded with curcumin;

[0106] ③ Prepare LSNPs with the process parameters of a starch suspension concentration of 4%, an alcohol-to-water ratio of 1:1, and an ultrasonic time of 50 min, and mix them at a ratio of LSNPs:CH of 1:0.085 under the composite condition of pH = 4, followed by magnetic stirring for 1 h to obtain the aqueous phase of the Pickering emulsion loaded with curcumin;

[0107] ④ With an emulsion formulation of CH / LSNPs particle concentration of 5%, oil phase volume fractions of 40% and 50%, prepare Pickering emulsions loaded with curcumin with different oil phase volumes under the high-speed homogenization condition of 20000 rpm for 2 min;

[0108] Control Example 1:

[0109] Under the same homogenization conditions as in Example 5(4), prepare an emulsion loaded with curcumin with a Tween 80 concentration of 5% and an oil phase volume of 40%.

[0110] Testing method:

[0111] (1) Determination of curcumin loading efficiency

[0112] Dissolve curcumin in ethanol to prepare a series of standard solutions with concentrations of 1 μg / ml, 2 μg / ml, 3 μg / ml, 4 μg / ml, 5 μg / ml, 6 μg / ml, and 7 μg / ml. Use an ultraviolet spectrophotometer to record the absorbance of different standard solutions at 425 nm and plot a curcumin standard curve.

[0113] Figure 10 Shows the loading efficiency of curcumin delivery systems constructed using different emulsifiers. The initial loading rates of all samples are above 90%. The curcumin loading rate of T40 is the lowest, at 90.77%, followed by CL50 at 94.7%, and the loading rate of CL40 is the highest, at 97.22%. These results indicate that all emulsion samples in this experiment have good curcumin loading effects.

[0114] (2) UV stability

[0115] Transfer an equal volume of the sample to a transparent centrifuge tube, and then irradiate it with a UV lamp in a closed environment, maintaining the environmental temperature at 25 °C during irradiation. The total irradiation time is 5 h. During this period, take out the same volume of the sample (0.2 ml) every 1 h, and determine the curcumin content of the sample by the method described in 5.3.1.2. The retention rate of curcumin is expressed as a percentage of the curcumin content: that is, C / C0 (%), where C is the curcumin content of the treated sample and C0 is the curcumin content of the initial sample.

[0116] The results are as Figure 11 shown. The Pickering emulsions stabilized by CH / LSNPs showed significant protective effects on the degradation of curcumin under UV irradiation. After 5 h of UV irradiation, the residual rates of curcumin in the Bulk oil, T40, CL40, and CL50 samples were 59.54%, 69.17%, 85.56%, and 82.22%, respectively. CL40 and CL50 showed better protective performance under UV irradiation. A possible explanation for the slightly higher retention rate of curcumin in CL40 than in CL50 is that the particle coverage at the oil-water interface of CL50 is less than that of CL40, and the space between the stabilizing particles is too large, which exposes more curcumin to UV irradiation.

[0117] (3) Thermal stability

[0118] Referring to the thermal sterilization process commonly used in the emulsion production process, 60 °C for 30 min and 100 °C for 1 min were set as the heating conditions for the experiment. And simulating human body temperature, a heating experiment condition of 37 °C for 4 h was added. After heat treatment, the samples were cooled to room temperature in a water bath, and the curcumin content of the samples was determined by the method described in 5.3.1.2, and the curcumin retention rate was calculated.

[0119] The curcumin retention rates of the samples after different heat treatments are as Figure 12 shown. After heat treatment in a 37 °C water bath for 4 h, the curcumin retention rates of all samples were above 85%; after heat treatment in a 60 °C water bath for 30 min or a 100 °C boiling water bath for 1 min, the curcumin retention rates of all samples decreased rapidly. However, the retention rates of curcumin in the CL40 and CL50 samples were significantly higher than those in the Bulk oil and T40 after both treatments.

[0120] (4) Storage stability

[0121] Under room temperature conditions, the freshly prepared curcumin-loaded emulsion samples and curcumin-loaded oil phase were sealed and stored in screw-cap transparent glass bottles for 30 days. At specific days, equal amounts of samples were taken out, the curcumin content in different samples was measured, and a graph of the curcumin retention rate versus storage time was plotted.

[0122] As Figure 13 shown, the curcumin retention rate decreased with the extension of storage time. Among all samples, the curcumin retention rate of T40 decreased the fastest, and only 43.87% remained after 30 days. Followed by Bulk oil, with a retention rate of 60.18% after 30 days. The curcumin in CL40 and CL50 showed the best retention rate, with a curcumin retention rate of 79.66% - 82.01% after 30 days

[0123] 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 any person 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 a Lipo taro starch-based Pickering emulsion, characterized in that Specifically, it includes the following steps: Take the prepared chitosan composite nano-starch particles. Under the compounding conditions of a chitosan composite nano-starch particle concentration of 1% - 6% and a pH of 2 - 8, prepare a dispersion with an oil phase volume fraction of 20% - 70%. After homogenously mixing the dispersion, a Pickering emulsion is obtained.

2. The preparation method of the Lipo taro starch-based Pickering emulsion according to claim 1, characterized in that, The concentration of the chitosan composite nano-starch particles is 3%.

3. The preparation method of the Lipo taro starch-based Pickering emulsion according to claim 1, characterized in that, The pH is 4.

4. The preparation method of the Lipo taro starch-based Pickering emulsion according to claim 1, characterized in that, The oil phase volume fraction is 40%.

5. The preparation method of the Lipu taro starch-based Pickering emulsion according to claim 1, characterized in that, The homogenously mixing is specifically carried out under the high-speed homogenization condition of 20,000 rpm for 2 minutes.

6. The preparation method of the Lipu taro starch-based Pickering emulsion according to claim 1, characterized in that, The oil phase is sunflower oil.

7. The preparation method of the Lipo taro starch-based Pickering emulsion according to claim 1, characterized in that, The chitosan composite nano-starch particles are prepared by the following method: (1) Preparation of Lipu taro starch: Grind Lipu taro in a plant tissue crusher; screen the obtained slurry, and then let the filtrate settle in an ice bath; after settling, pour off the upper layer of 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; Subsequently, neutralize to pH 7 with HCl solution, centrifuge, remove the supernatant, scrape off the upper layer of 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; (2) Preparation of Lipu taro nano-starch particles: Prepare a starch suspension, continuously stir it in a boiling water bath until the starch is completely gelatinized; after gelatinizing the starch, ultrasonically treat it and then gradually add it dropwise to an ethanol solution under continuous stirring to prepare Lipu taro starch nanoparticles LSNPs by the 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 freeze-dry to obtain dry LSNPs; (3) Preparation of Lipu taro starch nanoparticle composite chitosan: Dissolve chitosan (CH) in acetic acid solution, stir it overnight at room temperature to ensure complete dissolution, and prepare a 1 wt% 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.

8. A Lipu taro starch-based Pickering emulsion, characterized in that, Prepared by the method described in any one of claims 1 - 7.

9. Application of the Lipu taro starch-based Pickering emulsion described in claim 8 in protecting lipophilic active substances.

10. A fat-soluble active substance protectant, characterized in that, Prepared by using the Lipu taro starch-based Pickering emulsion described in claim 8.

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