OSA modified millet starch-based ternary composite particle, preparation method thereof and application of OSA modified millet starch-based ternary composite particle in preparation of high-internal-phase Pickering emulsion

Abstract

The invention discloses an OSA modified millet starch-based ternary composite particle, a preparation method thereof and application of the OSA modified millet starch-based ternary composite particle in preparation of a high-internal-phase Pickering emulsion, and belongs to the field of food industry, and the high-internal-phase Pickering emulsion prepared by the preparation method shows excellent rheological property and structural stability, is in a gel-like state, and can be used for preparing the high-internal-phase Pickering emulsion. The high-internal-phase Pickering emulsion has good self-supporting performance and elasticity-dominated viscoelastic behavior, the composite particles are uniformly distributed on an interface, a compact three-dimensional network structure is constructed, and the high-internal-phase Pickering emulsion has good thixotropic restorability and shape retention ability and can quickly recover the structure after being sheared.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of food industry, and particularly relates to a kind of OSA modified millet starch-based ternary composite particles, a preparation method thereof and application in preparing high internal phase Pickering emulsion. BACKGROUND

[0002] High internal phase Pickering emulsion is a kind of Pickering emulsion with internal phase volume fraction exceeding 74%. In addition to the characteristics of traditional Pickering emulsion (such as long-term stability and larger interface area), high internal phase Pickering emulsion also has a three-dimensional network structure closely connected by droplets and unique rheological properties. This gives high internal phase Pickering emulsion a broad application prospect in the fields of food, pharmaceuticals and other functional materials, especially in the development of semi-solid, gel-like fat substitutes and 3D printing inks.

[0003] High internal phase Pickering emulsion has great application potential in food processing, and is particularly suitable for building personalized food formulations with specific texture characteristics, shapes and functions to meet the nutritional needs of specific populations such as infants, dysphagia patients, etc. However, the high internal phase volume fraction of high internal phase Pickering emulsion requires higher wettability and emulsification of solid particle emulsifiers, which are usually treated by physical, chemical or composite modification methods to better stabilize high internal phase Pickering emulsion.

[0004] Currently, solid particles used to stabilize high internal phase Pickering emulsion mainly include inorganic nanoparticles (such as SiO2, Fe3O4, etc.), protein particles and starch-based particles. Compared with starch particles, protein particles are prone to sedimentation due to the influence of isoelectric point, hindering the preparation of emulsion, and protein is easily denatured by high temperature, leading to poor emulsion stability. However, natural starch has strong hydrophilicity and low interfacial activity, making it difficult to meet the requirements of high internal phase emulsion in interfacial adsorption, structure support and stability, and usually needs to be modified. Octenyl succinic anhydride (OSA) is a food-grade modifier that can impart hydrophobicity to starch particles through esterification, allowing them to have stronger adsorption capacity at the oil-water interface. However, it was found in actual research that OSA-modified starch particles still have significant deficiencies in terms of antioxidant capacity and 3D printing adaptability, etc. For example: the emulsion system lacks antioxidant protection and is prone to oxidative deterioration during storage or heat treatment; the system has poor thixotropic recovery, making it difficult to meet the application requirements of 3D printing ink.

[0005] Millet starch has a wide source and uniform particle distribution, which is suitable for particle construction of Pickering emulsion. However, it is still difficult to realize the stable construction of high internal phase emulsion by using only modified millet starch as a stabilizer. Therefore, it is necessary to construct composite particles to enhance interfacial activity, structural stability and antioxidant properties.

[0006] Chitosan hydrochloride (CHC) is a water-soluble derivative of chitosan, which is positively charged and can interact with modified starch particles with negative charge through electrostatic interaction, further improving the interfacial stability. As a natural tea polyphenol, epigallocatechin gallate (EGCG) has significant antioxidant capacity, which can give the composite particles stronger antioxidant effect. At the same time, its complex with starch particles can improve the emulsifying properties of the particles.

[0007] Patent CN115886204B discloses a preparation method of Pickering high internal phase emulsion for dumpling filling additives, which provides a preparation method of high internal phase Pickering emulsion stabilized by sea bass protein-EGCG composite particles. The sea bass protein and EGCG are prepared into solutions respectively; the two solutions are mixed; the pH of the solution is adjusted to 5-11; and the obtained solution is mixed with edible oil to prepare high internal phase Pickering emulsion by shearing emulsification. However, the protein used in this method is easily affected by the isoelectric point, and the emulsion needs to be prepared under alkaline conditions, and the protein is easily denatured by high temperature.

[0008] In summary, the existing high internal phase Pickering emulsion still has problems such as weak emulsifying capacity of composite particles, poor environmental stability, poor rheological properties of emulsion and poor adaptability to 3D printing. SUMMARY

[0009] To solve the above problems, the present application provides a kind of OSA modified millet starch-based ternary composite particles and its preparation method and application in the preparation of high internal phase Pickering emulsion, which solves the problems of weak emulsifying capacity of traditional starch particle stabilizer, poor environmental stability, weak functionality and poor adaptability of emulsion 3D printing. The OSA modified millet starch-based ternary composite particles prepared by the present application have smaller particle size, suitable wettability and excellent antioxidant capacity. The high internal phase Pickering emulsion prepared by the OSA modified millet starch-based ternary composite particles provided by the present application has good stability and rheological properties, and is suitable for edible 3D printing ink, which has wide application value in food industry.

[0010] One of the technical solutions provided by the present application is:

[0011] A preparation method of OSA modified millet starch-based ternary composite particles, comprising the following steps: millet starch is sequentially subjected to OSA modification and enzymatic modification to obtain enzymatic OSA millet starch; the enzymatic OSA millet starch is subjected to complex reaction with CHC and EGCG to prepare the OSA modified millet starch-based ternary composite particles.

[0012] The introduction of CHC and EGCG into the system can significantly improve the structural compactness and functionality of the composite particles, so that the particle system has good interfacial adsorption capacity and antioxidant performance at the same time, thereby improving the overall stability of the emulsion.

[0013] Further, the complex reaction specifically comprises the following steps: the pH of the mixed solution of the enzymatic OSA millet starch and CHC is adjusted, a first stirring reaction is carried out at room temperature to obtain an enzymatic OSA millet starch / chitosan hydrochloride complex solution; the EGCG is added, a second stirring reaction is carried out, and freeze-drying is carried out to prepare the OSA modified millet starch-based ternary composite particles.

[0014] Further, the mass ratio of the enzymatic OSA millet starch, CHC and EGCG is 60:15:4.

[0015] Further, the pH is 6.0.

[0016] Further, the first stirring reaction time is 30 min, and the second stirring reaction time is 60 min.

[0017] The preparation method of the EOMS (enzymatic OSA millet starch) is as follows:

[0018] (1) The millet is ground through a 100-mesh sieve to obtain millet powder, and millet starch is extracted from the millet powder by an alkali extraction method, that is, the ground millet powder is mixed with a NaOH solution, stirred at 25 DEG C for 4 hours, and then statically placed for 24 hours, centrifuged, washed, and dried to obtain the millet starch.

[0019] (2) The extracted millet starch is subjected to esterification reaction with OSA, the reaction temperature is controlled to be 35 DEG C, the reaction time is 3 hours, and after the reaction, neutralization, washing, and drying, the dried OSA millet starch is dissolved in a phosphate buffer solution, high-temperature-resistant alpha-amylase is added, and stirring is carried out in a 95 DEG C water bath for 12 min, and freeze-drying is carried out to obtain the EOMS.

[0020] The concentration of the NaOH solution in step (1) is 0.2% (W / V), and the solid-liquid ratio of millet powder and the NaOH solution is 1:4; in step (2), the pH of the solution is controlled at 8.5 during the reaction, the OSA addition amount accounts for 3% (W / W) of the dry basis of the starch, the pH of the phosphate buffer solution is 6.5, the concentration is 0.01 mol / L, and the addition amount of the thermostable alpha-amylase is 20 U / g (accounting for the dry basis of the starch).

[0021] The millet starch is used as a raw material, is rich in source, low in cost, does not add inorganic materials, and is high in biological safety. The millet starch is small in particle size and uniform in distribution, and is suitable for preparing Pickering emulsion as a solid particle. After the millet starch is esterified and enzymatically modified by OSA, the millet starch is moderately hydrophobic, has good interfacial activity, can be effectively adsorbed on the oil-water interface, and can stabilize the high internal phase emulsion.

[0022] The second technical solution provided in the application has the following advantages and technical effects:

[0023] The OSA modified millet starch ternary composite particle prepared by the preparation method is provided.

[0024] The third technical solution provided in the application has the following advantages and technical effects:

[0025] The application of the OSA modified millet starch ternary composite particle in preparing a high internal phase Pickering emulsion is provided.

[0026] The fourth technical solution provided in the application has the following advantages and technical effects:

[0027] The preparation method of the high internal phase Pickering emulsion comprises the following steps: mixing the OSA modified millet starch ternary composite particle aqueous solution with medium-chain triglyceride, and dispersing at 12000 r / min for 2 min to prepare the high internal phase Pickering emulsion.

[0028] Further, the pH of the OSA modified millet starch ternary composite particle aqueous solution is 4-6; the mass concentration of the OSA modified millet starch ternary composite particle aqueous solution is 2.5-3.5%; and the volume ratio of the OSA modified millet starch ternary composite particle aqueous solution to the medium-chain triglyceride is 1:3.

[0029] Still further, the pH of the OSA modified millet starch ternary composite particle aqueous solution is 6; and the mass concentration of the OSA modified millet starch ternary composite particle aqueous solution is 2.5%.

[0030] Compared with the prior art, the application has the following advantages and technical effects:

[0031] The prepared high internal phase Pickering emulsion of the application exhibits excellent rheological properties and structural stability, is in a gel-like state, has good self-supporting property and elastic dominant viscoelastic behavior, the particles are uniformly distributed at the interface, and a dense three-dimensional network structure is constructed. The emulsion has good thixotropic recovery and shape retention capacity, can quickly recover the structure after shearing, especially when the composite particle concentration is greater than or equal to 2.5%, the emulsion exhibits excellent deformation resistance and printing precision, and is suitable for being used as edible 3D printing ink to construct a food model with clear and stable structure.

[0032] The prepared high internal phase Pickering emulsion of the application exhibits excellent stability in the pH range of 4-6, the particles are uniformly distributed at the oil-water interface, can construct a dense three-dimensional network structure, and effectively prevent droplet aggregation. The emulsion also has good thermal stability and can remain stable after high-temperature treatment. The emulsion is superior to traditional emulsion systems, and is suitable for acidic or near-neutral food systems or application scenarios with high requirements for structural stability, such as heat processing. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The three-phase contact angle of the composite particles with different EGCG addition amounts in Example 1 of the application;

[0035] Figure 2 The scanning electron microscope image of the composite particles with different EGCG addition amounts in Example 1 of the application;

[0036] Figure 3 The antioxidant performance of the composite particles with different EGCG addition amounts in Example 1 of the application;

[0037] Figure 4 The appearance and centrifugal stability photos of the high internal phase Pickering emulsion prepared by different concentrations of EOMS / CHC-EGCG composite particles in Example 2 of the application;

[0038] Figure 5 The microstructure of the high internal phase Pickering emulsion prepared by different concentrations of EOMS / CHC-EGCG 15-1 composite particles in Example 2 of the application;

[0039] Figure 6Storage modulus and loss modulus of high internal phase Pickering emulsions prepared with different concentrations of EOMS / CHC-EGCG 15-1 composite particles in Example 2 of the present application;

[0040] Figure 7 Strain sweep plot (left) and three-stage thixotropic recovery test results (right) of high internal phase Pickering emulsions prepared with different concentrations of EOMS / CHC-EGCG 15-1 composite particles in Example 2 of the present application;

[0041] Figure 8 3D printing effect plot of high internal phase Pickering emulsions prepared with different concentrations of EOMS / CHC-EGCG 15-1 composite particles in Example 2 of the present application;

[0042] Figure 9 Appearance and centrifugal stability plot of high internal phase Pickering emulsions prepared under different conditions in Example 3 of the present application;

[0043] Figure 10 Microstructure plot of high internal phase Pickering emulsions prepared under different conditions in Example 3 of the present application;

[0044] Figure 11 Strain sweep plot (a and c) and three-stage thixotropic recovery analysis results plot (b and d) of high internal phase Pickering emulsions prepared in Example 3 of the present application;

[0045] Figure 12 3D printing effect plot of high internal phase Pickering emulsions prepared under different conditions in Example 3 of the present application. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be non-limiting examples of the present application, and are intended to provide a further understanding of certain aspects, features and embodiments of the application.

[0047] It should be understood that the terms used in the present application are merely used to describe particular embodiments and are not intended to limit the present application. In addition, for numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is specifically disclosed. Each smaller range within the stated range and between any stated value or intermediate value within the stated range is also encompassed within the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art to which the application relates. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0049] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0050] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0051] The embodiment of the present application provides a preparation method of high internal phase Pickering emulsion, and steps are as follows: (1) taking millet as raw material to extract starch and carry out OSA and enzymatic modification; (2) preparing OSA modified millet starch-based ternary composite particles by compounding the modified millet starch with chitosan hydrochloride and EGCG; (3) mixing the OSA modified millet starch-based ternary composite particles prepared in step (2) with medium-chain triglyceride and carrying out shear emulsification to obtain high internal phase Pickering emulsion. The OSA modified millet starch-based ternary composite particles prepared in the present application have good biological safety, the composite particles have small particle size, suitable wettability and excellent antioxidant property; the high internal phase Pickering emulsion prepared by the composite particles has good stability, unique rheological property, strong supporting force, good thixotropic recovery performance, is not easy to be affected by pH and temperature, can be used for 3D printing and has good prospects in the application of novel edible 3D printing ink.

[0052] The room temperature of the present application refers to 25±2 DEG C.

[0053] The medium-chain triglyceride used in the present application is capric acid triglyceride.

[0054] Example 1

[0055] A preparation method of OSA modified millet starch-based ternary composite particles, comprising the following steps:

[0056] (1) Millet was ground through a 100-mesh screen and dispersed in 0.2% (W / V) NaOH solution at a solid-to-liquid ratio of 1:4. After stirring at room temperature for 4 h, the mixture was allowed to stand for 24 h, and then centrifuged at 4000 r / min for 15 min. The supernatant and yellow substance were removed, and the starch layer was collected, washed repeatedly with deionized water, and centrifuged until only white starch remained in the precipitate. The obtained starch was dissolved in deionized water and adjusted to neutral with dilute hydrochloric acid (concentration of 1 mol / L). After removing the water by centrifugation, the starch was dried in an oven at 40°C for 48 h, ground through a 100-mesh screen, and obtained as millet starch;

[0057] (2) The millet starch was prepared into a 35% (W / V) starch milk by adding deionized water, and the pH was adjusted to 8.5 with 0.1 mol / L NaOH. The obtained starch milk was placed in a 35°C water bath, and then octenyl succinic anhydride (3% of the dry starch by weight) diluted 3 times with anhydrous ethanol was slowly added dropwise. The dropwise addition was controlled for 1 h, and after the dropwise addition was completed, the reaction was continued for 2 h. During the reaction, the pH of the starch milk was maintained at 8.5. After the reaction was completed, the pH was adjusted to 6.5 with 1 mol / L hydrochloric acid, the supernatant was removed by centrifugation, and the starch was washed three times with 75% (V / V) ethanol and deionized water, respectively, and then dried in an oven at 40°C for 48 h to obtain OSA millet starch. The dried OSA millet starch was ground through a 100-mesh screen, dissolved in 0.01 mol / L phosphate buffer solution (pH 6.5), prepared into a 10% (W / W) starch milk, and then 20 U / g (based on the dry starch) of high-temperature-resistant α-amylase (Bacillus licheniformis) was added. The mixture was stirred in a 95°C water bath for 12 min. After the reaction was completed, the pH was adjusted to 3.0 with 1 mol / L hydrochloric acid to inactivate the enzyme, and then the pH was adjusted to 7.0 with 1 mol / L NaOH aqueous solution. The freeze-dried product was obtained as enzyme-digested OSA millet starch, named EOMS;

[0058] (3) EOMS and chitosan hydrochloride (CHC) were weighed and dissolved in deionized water to obtain a 2% (W / W) EOMS solution and a 0.5% (W / W) CHC solution, respectively. The solutions were stored at 4°C overnight to allow them to fully hydrate. Then, the EOMS solution and the CHC solution were mixed in equal volumes at 25°C and pH 6.0, and stirred for 30 min to obtain an EOMS / CHC composite solution with a mass ratio of 4:1;

[0059] (4) EGCG was added to the EOMS / CHC composite solution prepared in step (3) to obtain EOMS / CHC-EGCG composite particles with mass ratios of EOMS to EGCG of 20:1, 15:1, 10:1, and 5:1, respectively. The mixture was stirred at 25°C for 60 min, and then freeze-dried to obtain EOMS / CHC-EGCG composite particles, which were named EOMS / CHC-EGCG 20-1, EOMS / CHC-EGCG 15-1, EOMS / CHC-EGCG 10-1, and EOMS / CHC-EGCG 5-1, respectively.

[0060] Comparative Example 1

[0061] A method for preparing OSA modified millet starch-based binary composite particles, comprising the following steps:

[0062] Steps (1)-(2) are the same as Example 1;

[0063] (3) EOMS and chitosan hydrochloride (CHC) were weighed and dissolved in deionized water to obtain 2% (W / W) EOMS solution and 0.5% (W / W) CHC solution, respectively, which were stored at 4°C overnight to allow full hydration. Then, the above EOMS solution and CHC solution were mixed at equal volume under the condition of 25°C and pH=6.0, stirred for 30 min to obtain EOMS / CHC composite solution with a mass ratio of 4:1, and freeze-dried to obtain EOMS / CHC composite particles, named EOMS / CHC 4:1.

[0064] Performance test test one

[0065] The particle size of EOMS / CHC-EGCG 20-1, EOMS / CHC-EGCG 15-1, EOMS / CHC-EGCG 10-1 and EOMS / CHC-EGCG 5-1 in Example 1 and EOMS / CHC 4:1 in Comparative Example 1 was tested, and the test results are shown in Table 1.

[0066] Table 1

[0067] Sample Particle size (nm) PDI EOMS / CHC4:1 300.4 ± 9.9 bc ]] 0.454 ± 0.05 c <!-- 5 -->]]> EOMS / CHC-EGCG20-1 280.2 ± 10 bcd ]] 0.507 ± 0.04 ab ]] EOMS / CHC-EGCG15-1 277.6 ± 9.8 bcd ]] 0.439 ± 0.02 bc ]] EOMS / CHC-EGCG10-1 309.7 ± 18.8 ab ]] 0.550 ± 0.07 a ]] EOMS / CHC-EGCG5-1 339.8 ± 17.2 a ]] 0.476 ± 0.02 abc ]]

[0068] Note: Different lowercase letters in each column indicate significant differences (p<0.05) between different samples.

[0069] As can be seen from Table 1, with the increase of the amount of EGCG added, the particle size of the composite particles decreases from 300.4 nm (EOMS / CHC 4:1) to 277.6 nm (EOMS / CHC-EGCG 15-1). EGCG is combined with EOMS and CHC through hydrogen bonds and hydrophobic interactions, allowing EGCG to embed in the interstitial space of the composite particles, which promotes the formation of a dense structure inside the composite particles, resulting in a decrease in particle size. In addition, the PDI (Polydispersity Index) of EOMS / CHC-EGCG 15-1 composite particles is the lowest (0.439), indicating a narrow particle size distribution. However, an excessive amount of EGCG will accumulate on the surface of the composite particles, resulting in an increase in the average particle size. Therefore, EOMS / CHC-EGCG 15-1 composite particles have the most suitable particle size and dispersity, which is beneficial to the stability of the emulsion.

[0070] The three-phase contact angles of the composite particles with different EGCG addition amounts are shown in Figure 1 As can be seen from Figure 1 , the hydrophobicity of the composite particles increases first and then decreases with the increase of the EGCG addition amount. The catechin structure of EGCG helps to form the composite particles, thereby enhancing the surface hydrophobicity, while excessive EGCG will gather on the surface of the composite particles due to its strong hydrophilicity, resulting in a decrease in the hydrophobicity. When the three-phase contact angle is close to 90°, the adsorption of the composite particles in the emulsion can reach a peak. This is conducive to the irreversible adsorption of the composite particles at the oil-water interface, effectively preventing droplet coalescence and enhancing the stability of the emulsion. Among them, the three-phase contact angle of the EOMS / CHC-EGCG 15-1 composite particles is 88.17°, which shows strong interfacial adsorption capacity and suitable wettability.

[0071] The scanning electron microscope images of the composite particles with different EGCG addition amounts are shown in Figure 2 As can be seen from Figure 2 , there are wrinkles and pores on the surface of the EOMS / CHC, indicating that the structure arrangement is relatively loose. A small amount of EGCG added will make the structure of the composite particles dense, while excessive EGCG concentration will increase the pores of the composite particles, and the excess EGCG will be adsorbed on the surface of the particles, resulting in a loose structure of the composite particles. Therefore, an appropriate amount of EGCG addition can make the composite particles present a dense network structure, which is conducive to the stability of the emulsion. As can be seen from Figure 2 , the EOMS / CHC-EGCG 15-1 composite particles show the densest structure.

[0072] The antioxidant performance of the composite particles with different EGCG addition amounts is shown in Figure 3 As can be seen from Figure 3 , the DPPH and ABTS free radical scavenging rates of the EOMS / CHC composite particles are 0.67% and 3.53% respectively; the DPPH free radical scavenging rates of the EOMS / CHC-EGCG 20-1, EOMS / CHC-EGCG 15-1, EOMS / CHC-EGCG 10-1 and EOMS / CHC-EGCG 5-1 composite particles are 56.23%, 70.15%, 88.19% and 89.65% respectively, and the ABTS free radical scavenging rates are 55.84%, 70.76%, 91.62% and 91.78% respectively, which proves that the addition of EGCG improves the antioxidant capacity of the composite particles and is conducive to the long-term storage of the emulsion.

[0073] Example 2

[0074] A preparation method of an OSA modified millet starch-based ternary composite particle high internal phase Pickering emulsion is provided.

[0075] The EOMS / CHC-EGCG15-1 composite particles prepared in Example 1 were prepared into aqueous solutions (0.5%, 1%, 1.5%, 2%, 2.5%, 3% and 3.5%, W / V) respectively, and then mixed with medium-chain triglyceride (MCT) respectively to prepare a mixed system with a total volume of 80 mL and an oil phase volume fraction of 75%. Then, a high internal phase Pickering emulsion of OSA modified foxtail millet starch-based ternary composite particles was obtained by using a high-speed disperser at 12000 r / min for 2 min.

[0076] Performance test experiment two

[0077] The appearance and centrifugal stability of the high internal phase Pickering emulsion prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles are shown in Figure 4 From Figure 4 it can be seen that the emulsion with a composite particle concentration of 1% to 3.5% has a uniform gel state and still has self-supporting ability after inversion, so the high internal phase Pickering emulsion prepared by the present application can be used for 3D product printing.

[0078] The microstructure of the liquid droplets in the above high internal phase Pickering emulsion was directly observed by fluorescence inverted microscope. The microstructure of the high internal phase Pickering emulsion prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles is shown in Figure 5 From Figure 5 it can be seen that: compared with the emulsion stabilized by low-concentration EOMS / CHC-EGCG composite particles, the emulsion formed under a higher concentration condition has smaller droplet size, tighter droplet arrangement and higher structural compactness. This structural feature is conducive to enhancing the viscosity and stability of the emulsion. With the further increase of the concentration of the microparticles, the coverage degree of the composite particles on the surface of the droplets and the filling degree of the gap between the droplets are simultaneously improved, thereby promoting the droplets to be firmly embedded in the three-dimensional network architecture constructed by the composite particles, significantly improving the overall structural integrity and storage performance of the emulsion.

[0079] The above high internal phase Pickering emulsion was subjected to frequency scanning. The storage modulus and loss modulus of the high internal phase Pickering emulsion prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles are shown in Figure 6 From Figure 6It can be seen that the storage modulus (G') of all emulsions is significantly greater than the loss modulus (G"), which indicates that the emulsions mainly exhibit elastic characteristics. As the concentration of composite particles increases from 0.5% to 3.5%, both G' and G" increase, and the storage modulus is almost independent of frequency at a constant strain, exhibiting typical characteristics of gel-like emulsions. Higher concentrations of EOMS / CHC-EGCG15-1 composite particles enhance the gel strength of the emulsion.

[0080] The strain sweep of high internal phase Pickering emulsions prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles is shown in Figure 7 The three-stage thixotropic recovery analysis of high internal phase Pickering emulsions prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles is shown in Figure 7 Figure 7 It can be seen fromthat in the linear viscoelastic region, G' is always higher than G", indicating that the emulsion exhibits elastic-dominated structural properties and can withstand deformation caused by mechanical forces. As the strain increases, G' decreases and G" increases. At high strain, the G" value of all emulsions shows a trend of first increasing and then decreasing, indicating that the flowability of the emulsion increases at high strain, indicating that during the 3D printing process, the emulsion can be extruded through the nozzle under high pressure and then solidified to form a specified shape after the pressure is released. When the shear rate is 1 s -1 , the viscosity of the emulsion is high, and shear thinning occurs during the 150 s scanning process. When the shear rate is 100 s -1 , the viscosity decreases rapidly. When the shear rate returns to 1 s -1 , the viscosity rises, indicating that the emulsion has strong anti-deformation ability and thixotropic recovery performance, and the higher the concentration of composite particles, the stronger the recovery properties of the emulsion.

[0081] The 3D printing effect diagram of high internal phase Pickering emulsions prepared from different concentrations of EOMS / CHC-EGCG15-1 composite particles is shown in Figure 8 It can be seen from Figure 8 that the printed samples of high internal phase Pickering emulsions with high composite particle concentration have sufficient mechanical properties and can achieve good printing fidelity. However, when the particle concentration is 0.5% to 2%, the cuboid sample collapses and cannot maintain its shape. When the particle concentration increases from 2.5% to 3.5%, the surface of the sample shows more delicate texture without collapse. Similar phenomena are also observed in the "Superman" pattern, and as the concentration of added composite particles increases, the 3D printed pattern outline gradually becomes clear and the texture becomes more obvious.

[0082] Example 3

[0083] The OSA modified millet starch-based ternary composite particles were used to prepare high internal phase Pickering emulsion under different environmental factors, and the specific steps were as follows:

[0084] The EOMS / CHC-EGCG15-1 composite particles prepared in Example 1 were prepared into an aqueous solution (2.5%, W / V, pH 3, 4, 5 and 6), mixed with medium-chain triglyceride (MCT), and a mixed system with a total volume of 80 mL and an oil phase volume fraction of 75% was prepared. Then, a high internal phase Pickering emulsion of OSA modified millet starch-based ternary composite particles under different pH conditions was obtained by using a high-speed dispersion machine at 12000 r / min for 2 min.

[0085] Five portions of the EOMS / CHC-EGCG15-1 composite particles prepared in Example 1 were prepared into an aqueous solution (2.5%, W / V, pH 6), mixed with medium-chain triglyceride (MCT), and a mixed system with a total volume of 80 mL and an oil phase volume fraction of 75% was prepared. Then, five portions of high internal phase Pickering emulsion of OSA modified millet starch-based ternary composite particles were obtained by using a high-speed dispersion machine at 12000 r / min for 2 min, and the above-mentioned five portions of high internal phase Pickering emulsion were respectively placed at 4℃, 25℃, 37℃, 60℃ and 70℃ for 60 min.

[0086] Performance test test three

[0087] The appearance and centrifugal stability of the high internal phase Pickering emulsion prepared under different conditions in Example 3 are shown in Figure 9 As can be seen from the standing appearance of the emulsion under different pH conditions and the appearance after centrifugation, when pH is 4-6, the emulsion can maintain high stability, and no demulsification or oil phase precipitation is observed after centrifugation. After treatment at different temperatures, the emulsion does not significantly precipitate oil or demulsify, and no obvious phase separation is observed after centrifugation, indicating that the emulsion system has strong thermal stability.

[0088] The microstructure of the high internal phase Pickering emulsion prepared under different conditions in Example 3 is shown in Figure 10 As can be seen from the standing appearance of the emulsion under different pH conditions and the appearance after centrifugation, when pH is 4-6, the emulsion can maintain high stability, and no demulsification or oil phase precipitation is observed after centrifugation. After treatment at different temperatures, the emulsion does not significantly precipitate oil or demulsify, and no obvious phase separation is observed after centrifugation, indicating that the emulsion system has strong thermal stability.

[0089] Figure 11Fig. 3 shows strain sweep diagrams of the high internal phase Pickering emulsions prepared in Example 3, and Fig. 4 shows results of three-stage thixotropic recovery analysis, from which it can be seen that the emulsions prepared under different pH conditions can all recover to the level of low shear rate after the action of high shear rate, indicating that they all have the potential for 3D printing; after treatment at different temperatures, the strength of the gel network of the emulsions decreases, but their recovery ability is not destroyed, indicating that the emulsions can withstand the impact of food thermal processing. Figure 11

[0090] Fig. 5 shows the 3D printing effect of the high internal phase Pickering emulsions prepared under different conditions in Example 3, from which it can be seen that in the range of pH = 3-6, the support force of the printed sample increases with the increase of pH, and the texture profile is clearer; the printed sample of the emulsion after treatment at a higher temperature is slightly reduced in clarity, but is overall stable, indicating that the emulsion has good environmental stability. Figure 12 Figure 12

[0091] In summary, the high internal phase Pickering emulsion prepared from the OSA modified millet starch-based ternary composite particles provided by the present application has wide application value and prospect in 3D printing.

[0092] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.​​​

Claims

1. A method for preparing OSA-modified millet starch-based ternary composite particles, characterized in that: The method comprises the following steps: sequentially subjecting millet starch to OSA modification and enzymatic modification to obtain enzymatically hydrolyzed OSA millet starch; and subjecting the enzymatically hydrolyzed OSA millet starch to a composite reaction with chitosan hydrochloride and epigallocatechin gallate to prepare the OSA-modified millet starch-based ternary composite particles.

2. The preparation method according to claim 1, characterized in that The composite reaction specifically includes the following steps: adjusting the pH of the mixed solution of the enzymatically hydrolyzed OSA millet starch and chitosan hydrochloride to weak acidity, stirring and reacting for the first time at room temperature to obtain an enzymatically hydrolyzed OSA millet starch / chitosan hydrochloride composite solution; adding the epigallocatechin gallate, stirring and reacting for the second time, and freeze-drying to prepare the OSA-modified millet starch-based ternary composite particles.

3. The preparation method according to claim 2, characterized in that The mass ratio of the enzymatically hydrolyzed OSA millet starch, chitosan hydrochloride and epigallocatechin gallate is 60:15:

4.

4. The preparation method according to claim 2, characterized in that The pH was 6.

0.

5. The preparation method according to claim 2, characterized in that The time for the first stirring reaction was 30 min, and the time for the second stirring reaction was 60 min.

6. OSA-modified millet starch-based ternary composite particles prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the OSA-modified millet starch-based ternary composite particles according to claim 6 in preparing a high internal phase Pickering emulsion.

8. A method for preparing a high internal phase Pickering emulsion, characterized in that: The method comprises the following steps: mixing the OSA-modified millet starch-based ternary composite particle aqueous solution according to claim 6 with medium-chain triglycerides, and dispersing the mixture at 12,000 r / min for 2 minutes to prepare the high internal phase Pickering emulsion.

9. The preparation method according to claim 8, characterized in that The pH of the OSA-modified millet starch-based ternary composite particle aqueous solution is 4-6; the mass concentration of the OSA-modified millet starch-based ternary composite particle aqueous solution is 2.5-3.5%; the volume ratio of the OSA-modified millet starch-based ternary composite particle aqueous solution to medium-chain triglycerides is 1:

3.

10. The preparation method according to claim 9, characterized in that The pH of the OSA-modified millet starch-based ternary composite particle aqueous solution is 6; the mass concentration of the OSA-modified millet starch-based ternary composite particle aqueous solution is 2.5%.

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