A soybean protein isolate-ethyl cellulose composite granule, its preparation method and its application in Pickering emulsion.

Abstract

This invention relates to the fields of food science and food processing technology, and provides a soybean protein isolate-ethyl cellulose composite particle, its preparation method, and its application in Pickering emulsions. The composite particle is formed by the self-assembly of soybean protein isolate and ethyl cellulose under acidic conditions, with a contact angle of 96.20°~108.16°, a particle size of 213.1~359.1 nm, a zeta potential of +20.36~+25.90 mV, and an interfacial tension lower than that of a single component. This composite particle can be used as a stabilizer in the preparation of O / W type Pickering emulsions, which exhibit excellent storage stability, shear-thinning properties, and solid-like elasticity, and can be applied to spreads and 3D printing materials. Therefore, this invention provides a new option for plant protein-cellulose-based composite particles in the food industry.

Description

Technical Field

[0001] This invention relates to the fields of food science and food processing technology, and in particular to a soybean protein isolate-ethyl cellulose composite granule, its preparation method, and its application in Pickering emulsion. Background Technology

[0002] Emulsions are colloidal dispersions composed of two immiscible liquids, and traditional emulsions rely on surfactants or amphiphilic polymers for stabilization. However, surfactants pose environmental risks such as enzyme inhibition, water pollution, and poor degradation. Pickering emulsions stabilized with solid particles offer higher stability, lower toxicity, and better biocompatibility, making them a hot research topic.

[0003] Stabilizing Pickering emulsions can be categorized into inorganic and organic particles. Inorganic particles have poor biodegradability, compatibility, and safety, making them unsuitable for the food industry. Green, edible organic particles, especially protein particles, are considered the most promising food-grade Pickering emulsion stabilizers due to their excellent interfacial adsorption properties, low toxicity, and good biocompatibility.

[0004] Soy protein isolate is amphiphilic and can spontaneously adsorb at the oil-water interface to reduce interfacial tension. However, its stability is easily affected by environmental factors such as pH, ionic strength, and temperature, and the emulsion is prone to aggregation. Studies have shown that co-assembly of edible polysaccharides and proteins can improve the emulsifying properties of soy protein isolate. Ethyl cellulose is a food-grade hydrophobic polymer that can form a stable adsorption layer at the oil-water interface. Under acidic conditions, soy protein isolate is positively charged, and ethyl cellulose is negatively charged. The two can form stable composite particles through electrostatic attraction, hydrogen bonding, and hydrophobic interactions. Interfacial rheological measurements can assess the strength of the adsorption film. These interactions are expected to improve the interfacial wettability of the particles, enabling them to be firmly adsorbed at the oil-water interface, constructing a dense particle layer, and thus improving emulsion stability.

[0005] Therefore, developing a composite particle based on soy protein isolate and ethyl cellulose as a highly efficient and stable food-grade Pickering emulsion stabilizer is of significant theoretical and practical importance.

[0006] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the Invention

[0007] To address the aforementioned deficiencies, the present invention aims to provide a soybean protein isolate-ethyl cellulose composite particle, its preparation method, and its application in Pickering emulsions. This particle can self-assemble through electrostatic attraction and hydrophobic interactions to obtain suitable wettability and particle size, thereby efficiently stabilizing O / W type Pickering emulsions and endowing the emulsions with excellent storage stability and rheological properties.

[0008] To achieve the above objectives, the present invention provides a composite particle of soy protein isolate and ethyl cellulose, wherein the composite particle is formed by the self-assembly of soy protein isolate and ethyl cellulose under acidic conditions through electrostatic attraction, hydrogen bonding and hydrophobic interaction; the composite particle has a contact angle of 96.20°~108.16°, an average particle size of 213.1~359.1 nm, and a zeta potential of +20.36 mV~+25.90 mV; furthermore, the equilibrium interfacial tension of the composite particle at the oil-water interface is lower than that of pure soy protein isolate particles and pure ethyl cellulose particles.

[0009] As a further improvement, the total mass percentage of the composite particles is 30% to 60% soy protein isolate and 40% to 70% ethyl cellulose.

[0010] The present invention also provides a method for preparing the composite particles of soy protein isolate and ethyl cellulose, characterized by comprising the following steps:

[0011] S1. Dissolve soy protein isolate in water and adjust the pH to 2.5-3.5 to obtain an aqueous solution of soy protein isolate;

[0012] S2. Dissolve ethyl cellulose in ethanol, heat and stir until completely dissolved to obtain an ethyl cellulose ethanol solution;

[0013] S3. While hot, add the ethyl cellulose ethanol solution from step S2 to the soy protein isolate aqueous solution from step S1, and heat and stir at 80-95°C for 0.5-2 hours.

[0014] S4. Remove ethanol and water to obtain a composite particle dispersion.

[0015] As a further improvement, in step S4, rotary evaporation is used to remove ethanol and water at a temperature of 40~45°C.

[0016] The present invention also provides the application of the aforementioned soy protein isolate and ethyl cellulose composite particles as a stabilizer in the preparation of oil-in-water Pickering emulsions.

[0017] As a further improvement, the volume ratio of the oil phase to the water phase in the Pickering emulsion is 1:3 to 3:1, and the mass concentration of the composite particles is 1% to 5%.

[0018] As a further improvement, the storage modulus G′ of the Pickering emulsion is greater than the loss modulus G″, and G′ > 10 Pa under the conditions of 1 Hz and 1 Pa.

[0019] As a further improvement, the Pickering emulsion is a spreadable sauce.

[0020] The purpose of this invention is to provide a soybean protein isolate-ethyl cellulose composite granule, its preparation method, and its application in Pickering emulsion, with the following beneficial effects:

[0021] The particle size is synergistically refined. The particle size of pure EC particles is greater than 4.6 μm, while the particle size of SPI combined with EC is significantly reduced to 220~350 nm, which is beneficial to the uniform adsorption of particles at the oil-water interface.

[0022] The wettability is adjustable. By changing the SPI / EC ratio, the contact angle of the composite particles can be controlled within the range of 80° to 134°. The contact angle of the composite particles with a high EC ratio exceeds that of pure EC, exhibiting an unexpected hydrophobic enhancement effect, which is beneficial for irreversible adsorption.

[0023] The reduced interfacial tension, with the equilibrium interfacial tension of the composite particles being lower than that of pure SPI and pure EC, indicates a synergistic effect.

[0024] The emulsion exhibits excellent stability; the Pickering emulsion stabilized by these composite particles remains in emulsion form after being stored at room temperature for 3 months without complete demulsification.

[0025] It exhibits good rheological properties, the emulsion shows shear-thinning characteristics, the storage modulus G′ is greater than the loss modulus G″, and it still maintains structural restoring force under high strain.

[0026] It is food-grade and edible, with all raw materials being food-grade. It can be used in spreads, functional foods, and 3D printing materials. Attached Figure Description

[0027] Figure 1 These are analytical diagrams of the zeta potential, average particle size, interfacial tension, and surface contact angle of composite particles with different SPI / EC mass ratios.

[0028] Figure 2 These are scanning electron microscope images of soy protein isolate and ethyl cellulose composite particles (SECPs) in different proportions;

[0029] Figure 3 These are macroscopic appearance and optical microscope images of particle-stabilized Pickering emulsions with different SPI / EC mass ratios;

[0030] Figure 4 This is a graph showing the changes in particle size parameters and zeta potential of particle-stabilized emulsions with different SPI / EC mass ratios during storage.

[0031] Figure 5 These are laser confocal microscopy (CLSM) images of SECPEs;

[0032] Figure 6 This is a rheological property analysis diagram of SECPs-stabilized Pickering emulsions (SECPEs) with different ratios;

[0033] Figure 7 This is an elastic (stress-strain) lissajous curve of the SPEs of the present invention at different strain levels, wherein the elastic conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0034] Figure 8 This is an elastic (stress-strain) Lissajous curve of SECPs 6:4 of the present invention at different strain levels, wherein the elastic conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%.

[0035] Figure 9 This is an elastic (stress-strain) Lissajous curve of SECPs 5:5 of the present invention at different strain levels, wherein the elastic conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%.

[0036] Figure 10 This is an elastic (stress-strain) Lissajous curve of SECPs 4:6 of the present invention at different strain levels, wherein the elastic conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%.

[0037] Figure 11 This is an elastic (stress-strain) lissajous curve of SECPs 3:7 of the present invention at different strain levels, wherein the elastic conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%.

[0038] Figure 12 This is a viscous (stress-strain rate) ligsaw curve of the SPEs of the present invention at different strain levels, where the viscous conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0039] Figure 13This is a viscous (stress-strain rate) liissajous curve of SECPs 6:4 of the present invention at different strain levels, where the viscous conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0040] Figure 14 This is a viscous (stress-strain rate) ligscous curve of SECPs 5:5 of the present invention at different strain levels, where the viscous conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0041] Figure 15 This is a viscous (stress-strain rate) liissajous curve of SECPs 4:6 of the present invention at different strain levels, where the viscous conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0042] Figure 16 This is a viscous (stress-strain rate) liissajous curve of SECPs 3:7 of the present invention at different strain levels, wherein the viscous conditions from left to right and from top to bottom are 100%, 250%, 500%, 750%, and 1000%, respectively.

[0043] Figure 17 These are bread spreadability test diagrams for SECP emulsions with different ratios. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to experimental data and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0045] Raw materials and equipment:

[0046] Soy Protein Isolate (SPI): Shandong Yuwang Protein Co., Ltd., food grade

[0047] Ethyl cellulose (EC): viscosity 90-110 mPa·s, ethoxylate content 44-51%

[0048] Soybean oil: Yihai Kerry (Wuhan) Grain and Oil Industry Co., Ltd., food grade

[0049] Other reagents: sodium hydroxide, hydrochloric acid, ethanol (all analytical grade)

[0050] Deionized water (resistivity ≥ 18.2 MΩ·cm)

[0051] Example 1: Preparation and characterization of composite particles with SPI:EC = 6:4.

[0052] Weigh 1.8 g of SPI and dissolve it in 120 mL of deionized water. After stirring and dissolving, adjust the pH to 3.0 with 1 M and 0.1 M HCl, and sonicate for 5 min (475 W, 3 s on / 3 s off). Separately, weigh 1.2 g of EC and dissolve it in 20 mL of ethanol. Heat and stir at 70 °C for 1 h until completely dissolved. Add the hot EC solution dropwise to the SPI solution while hot, and heat and stir at 90 °C for 1 h. After the reaction is complete, remove the ethanol and water by rotary evaporation at 42 °C, and make up the volume to 50 mL to obtain a 3 wt% SECPs dispersion.

[0053] Particle size and zeta potential: Measured using a Zetasizer Nano ZS, in 5 parallel trials. Results: Average particle size 253.9 nm (range 221.3–346.7 nm), zeta potential +20.36 mV (range 19.5–20.9 mV).

[0054] Contact angle: After freeze-drying the SECPs and pressing them into tablets, the water droplet contact angle was measured in the oil phase using an OCA 25 contact angle meter. Results: Stable contact angle 108.16° (range 106.66~109.43°).

[0055] Interfacial tension: The oil-water interfacial tension was measured using an OCA 25 after diluting the SECPs to 0.01%. The equilibrium interfacial tension was 7.5 mN / m (lower than 12.5 mN / m for pure SPI and 15.2 mN / m for pure EC).

[0056] Example 2: Preparation and characterization of composite particles with SPI:EC = 5:5.

[0057] The preparation method is the same as in Example 1, with 1.5 g of SPI and 1.5 g of EC.

[0058] Average particle size: 302.7 nm (range 277.3~356.0 nm).

[0059] ζ potential: +24.48 mV (range 23.5~26.2 mV).

[0060] Contact angle: 103.71° (range 92.56~109.87°).

[0061] Interfacial tension: 7.8 mN / m.

[0062] Example 3: Preparation and characterization of composite particles with SPI:EC = 4:6.

[0063] The preparation method is the same as in Example 1, with SPI amounting to 1.2 g and EC amounting to 1.8 g.

[0064] Average particle size: 347.6 nm (range 334.5~359.1 nm).

[0065] ζ potential: +25.9 mV (range 24.5~26.4 mV).

[0066] Contact angle: 106.57° (range 103.26~109.07°).

[0067] Interfacial tension: 8.2 mN / m.

[0068] Example 4: Preparation and characterization of composite particles with SPI:EC = 3:7.

[0069] The preparation method is the same as in Example 1, with 0.9 g of SPI and 2.1 g of EC.

[0070] Average particle size: 223.7 nm (range 213.1~235.1 nm).

[0071] ζ potential: +21.88 mV (range 21.3~22.6 mV).

[0072] Contact angle: 96.20° (range 91.98~100.68°).

[0073] Interfacial tension: 8.8 mN / m.

[0074] Comparative Example 1: Pure SPI particles were prepared and characterized.

[0075] Preparation method: Weigh 3.0 g SPI and dissolve it in 120 mL of deionized water, adjust the pH to 3.0, sonicate and then rotary evaporate to a final volume of 50 mL.

[0076] Average particle size: 276.8 nm (range 270.6~286.8 nm).

[0077] ζ potential: +27.8 mV (range 27.0~29.0 mV).

[0078] Contact angle: 71.40° (range 68.07~75.8°).

[0079] Interfacial tension: 5.3 mN / m.

[0080] Comparative Example 2: Pure EC particles were prepared and characterized.

[0081] Preparation method: Weigh 3.0 g EC and dissolve it in 20 mL ethanol. Heat at 70 °C to dissolve. Add the solution dropwise to 120 mL pH 3.0 water. Heat at 90 °C for 1 h. Distill to a final volume.

[0082] Average particle size: 4910.2 nm (range 4644~5202 nm).

[0083] Zeta potential: -34.4 mV (range -35.9 to -32.9 mV).

[0084] Contact angle: 119.57° (range 119.37~119.73°).

[0085] Interfacial tension: 8.4 mN / m.

[0086] Example 5: Pickering emulsion was prepared from composite particles with a ratio of SPI:EC = 6:4 and its performance was tested.

[0087] Take 10 mL of 3 wt% SECPs dispersion, add 10 mL of soybean oil, and shear at 20000 rpm for 3 min to obtain SECPEs (6:4) emulsion.

[0088] Emulsion type: It can be evenly dispersed when dropped into water, and is an O / W type.

[0089] Storage stability: After standing at room temperature for 3 months, a slight creamy layer appeared on the bottle wall, with no emulsion breaking or oil leakage.

[0090] Microscopic morphology: Optical microscopy and CLSM show that the droplets are uniform and the interface is clear.

[0091] Rheological properties: shear thinning, G′ > G″, and the Lissajous curve under high strain in LAOS is full.

[0092] Spreadability: It can be easily spread on bread and spread evenly.

[0093] Example 6: Pickering emulsion was prepared from SPI:EC = 5:5 composite particles and its performance was tested.

[0094] Under the same shearing method, the emulsion is stable, and CLSM exhibits a uniform O / W structure and good rheological properties.

[0095] Example 7: Pickering emulsion was prepared from SPI:EC = 4:6 composite particles and its performance was tested.

[0096] Under the same shearing method, the emulsion is stable, and some W / O / W multi-emulsions appear.

[0097] Example 8: Pickering emulsion was prepared from SPI:EC = 3:7 composite particles and its performance was tested.

[0098] Cut using the same method, the emulsion is semi-solid, similar to mayonnaise, and is stable during storage and retains its shape well after application.

[0099] Comparative Example 3: Pickering emulsions were prepared from pure SPI particles and their performance was tested.

[0100] The emulsion was cut using the same method, and it separated into layers after 7 days and completely broke down after 30 days.

[0101] Comparative Example 4: Pickering emulsion was prepared from pure EC particles and its performance was tested.

[0102] When sheared using the same method, flocculent aggregation immediately occurs, oil and water separate, and a stable O / W emulsion cannot be formed.

[0103] The results and data of the above embodiments and comparative examples are analyzed below.

[0104] Different SPI / EC mass ratios significantly affect the surface charge, particle size, interfacial behavior, and wettability of particles. (See [link to relevant documentation]) Figure 1 , Figure 1 In the figure, A represents the zeta potential of particles under different SPI / EC composite ratios. SPs exhibit a positive zeta potential, while ECPs show a significantly negative zeta potential. The zeta potential of SECPs under different SPI / EC composite ratios is positive (20.36~25.90 mV), indicating that the composite particles are positively charged overall under acidic conditions. There is an electrostatic attraction between the positively charged SPs and the negatively charged ECPs, thus promoting the formation of composite particles, which is consistent with the findings of Hashemi et al. Furthermore, a moderate charge is beneficial to enhancing the adsorption capacity of particles at the oil-water interface, thereby improving the stability of Pickering emulsions. B represents the average particle size under different SPI / EC composite ratios. ECPs have the largest particle size, indicating that pure EC particles are more prone to aggregation and forming larger aggregates. (See [reference needed]). Figure 2The clustered structure observed under SEM also supports this conclusion, which may be related to its strong hydrophobicity. Duffus et al. also reported a similar phenomenon. In contrast, the particle size of SECPs is generally smaller than that of ECPs, indicating that the co-assembly of SPI and EC can inhibit EC aggregation to some extent. However, the particle size of SECPs in the 6:4 ratio is significantly increased, which may be related to the bridging aggregation induced by electrostatic attraction and hydrophobic interaction under this ratio. C is the curve of the interfacial tension (γ) of different particle systems at the oil-water interface over time. The interfacial tension (γ) of all samples decreases over time and tends to equilibrium, indicating that the particles gradually adsorb and rearrange at the oil-water interface. Similar phenomena were also seen in zein particles (ZP), soy protein isolate particles (SP), and their composite particle systems. Compared with SPs, SECPs generally exhibit a lower γ, indicating that the introduction of EC improves the interfacial adsorption behavior of the particles. D represents the trend of contact angle variation on particle surfaces with different SPI / EC composite ratios. SPs exhibit lower contact angles, while the contact angles of SECPs and ECPs significantly increase, indicating that the introduction of ECs significantly enhances the hydrophobicity of the particle surface and its irreversible adsorption capacity at the interface. Meanwhile, previous studies have confirmed that combining SPI with cellulosic materials can regulate wettability, enabling particles to achieve ideal interfacial equilibrium and thus improving the stability of O / W type Pickering emulsions. In summary, the combination of SPI and EC can simultaneously regulate particle charge, particle size, interfacial tension, and wettability. Among these, the 3:7 SECP ratio exhibits superior interfacial characteristics, which is more conducive to the formation of a stable Pickering emulsion system.

[0105] Scanning electron microscopy (SEM) characterization of the microstructure of particle samples prepared at different SPI / EC mass ratios is shown in [reference needed]. Figure 2 Among the samples, a: SPs 10:0, b: SECPs 6:4, c: SECPs 5:5, d: SECPs 4:6, e: SECPs 3:7, and f: ECPs 0:10. As shown in the figure, SPs are distributed in an approximately spherical shape, while ECs are distributed in a blocky shape. The microstructure of SECPs reflects the composite characteristics of SPs and ECPs. With the increase of EC content, the morphology of SECPs gradually transforms into a composite structure with both spherical and ribbon-like shapes, further improving the dispersibility and network degree of the particles. Existing literature indicates that electrostatic attraction, hydrogen bonding, and hydrophobic interactions between proteins and polysaccharides jointly drive the formation and structural rearrangement of composite particles.

[0106] For the macroscopic appearance and microstructure characteristics of Pickering emulsions with composite particles of different SPI / EC mass ratios, please refer to [reference needed]. Figure 3Under conditions of a 1:1 ratio of aqueous phase to soybean oil, an initial pH of 3, and a SECP mass fraction of 3%, Pickering emulsions with different SPI / EC mass ratios exhibited significant differences in macroscopic appearance, storage stability, and microscopic droplet morphology. Figure A shows the macroscopic appearance of the emulsions at 0 days post-preparation. The SPEs were uniformly milky white, and the four different SECPE ratios (6:4, 5:5, 4:6, and 3:7) were also uniformly milky white overall, with only a slight creamy layer appearing on the bottle wall. No obvious stratification or water seepage was observed, indicating good initial stability. In contrast, the ECPs were heterogeneous light yellow, accompanied by obvious flocculent aggregation and initial separation of the oil and water phases, indicating limited emulsifying performance. This is mainly due to the strong hydrophobicity of ECPs, which makes them prone to enrichment and formation of aggregates in the oil phase, thus weakening their stabilizing effect at the interface. B shows the macroscopic appearance of the emulsion after standing for 3 months. After 3 months, both SPEs and SECPEs systems at various ratios showed varying degrees of emulsification, but the SECPEs system generally maintained a certain emulsion state. The ECPs system, however, showed more pronounced phase separation, indicating that the combination of SPI and EC is more beneficial for improving the storage stability of the emulsion. C shows the optical microscopic images of the corresponding emulsions, where samples a: SPEs 10:0, b: SECPEs 6:4, c: SECPEs 5:5, d: SECPEs 4:6, e: SECPEs 3:7, and f: ECPEs 0:10. The stable SPEs emulsion droplets clustered together, with blurred interfaces and localized fusion. In contrast, the SECPEs droplets were more uniformly distributed, smaller in size, and had clearer outlines, indicating that the introduction of EC significantly improved the dispersion characteristics of the emulsion, thereby delaying phase separation. Similar patterns were observed in the cellulose nanocrystal (CNC) and peanut protein isolate (PPI) composite system. Studies by Nie et al. showed that the synergistic adsorption of composite particles at the oil-water interface effectively reduced droplet size and improved emulsion stability. With increasing EC content, the adsorption of particles at the interface in the SECPs system became more compact and uniform. The 3:7 SECPs exhibited the most uniform droplet size and significantly reduced aggregation, indicating a relatively dense and stable interfacial film structure at this ratio. Conversely, the ECPs system showed greater droplet size variation, significant aggregation, and incomplete interfacial coverage, resulting in phase separation and phase inversion, and even the formation of multiple emulsions. Type identification by dropping the emulsions into the aqueous and oil phases revealed that SPEs and all SECPEs were O / W type emulsions, while ECPs suffered severe demulsification.

[0107] For emulsion particle size distribution and potential characteristics, please refer to [reference needed]. Figure 4Where A is the Sauter average particle size D of the emulsion at 0 d and 7 d of storage [3,2]; B is the volume-weighted average particle size D of the emulsion at 0 d and 7 d of storage [4,3]; and C is the zeta potential of the emulsion at 0 d and 7 d of storage. It can be seen that after 7 d of storage, the particle size of the SECPEs emulsion changed less, while the potential changed, indicating that the composite particles underwent interfacial rearrangement or particle redispersion during storage, ultimately forming a denser interfacial film, thereby improving the droplet anti-coalescence ability. This is consistent with the conclusion of Shen et al. that "protein-cellulose composite particles continue to densify during storage, thus better stabilizing high internal phase emulsions." ECPEs initially produced the largest droplets, and microscopic droplet demulsification also verified that emulsions stable with ECPs were unstable. This may be because ECPs have low surface charge and did not effectively adsorb at the interface to form a protective layer. See [link to relevant documentation]. Figure 5 Therefore, the emulsion structure cannot be maintained, which is consistent with the phenomenon reported in previous literature.

[0108] See the results of laser confocal microscopy (CLSM) observations and structural distribution. Figure 5 In the study, samples a: SPEs 10:0, b: SECPEs 6:4, c: SECPEs 5:5, d: SECPEs 4:6, e: SECPEs 3:7, and f: ECPEs 0:10 were used. SECPs and soybean oil were stained with Nile Blue (red) and Nile Red (green). CLSM analysis showed that the SECP-stable emulsion exhibited a typical O / W structure, with the oil phase (green) uniformly dispersed in the aqueous phase (red). Compared to single-protein or ethyl cellulose systems, the composite system showed a more uniform droplet distribution and clearer droplet interfaces, indicating that SECPs can firmly adsorb at the oil-water interface and form a stable three-dimensional network structure in the aqueous phase. This structure significantly hinders droplet movement, inhibiting aggregation and sedimentation, thereby improving emulsion stability. Similar studies have shown that xanthan gum (XG) / lysozyme nanoparticles (Ly NPs) can also construct a three-dimensional network in the aqueous phase, enhancing the viscosity and solid-like elasticity of the emulsion. This study also confirms the crucial role of particle networks in maintaining the stability of Pickering emulsions. Notably, some composite systems exhibited a small number of W / O / W multi-layer emulsions on the basis of the O / W structure, indicating that SECPs possess strong adsorption capacity and moderate wettability at the interface, enabling them to stabilize different types of interfaces and form multi-layer structures.

[0109] For the rheological properties of Pickering emulsions with different SPI / EC mass ratios, please refer to [reference needed]. Figure 6Particle-stabilized emulsions with different SPI / EC mass ratios all exhibited typical non-Newtonian fluid and viscoelastic characteristics. A shows the apparent viscosity versus shear rate curve; the apparent viscosity of all samples decreased with increasing shear rate, exhibiting significant shear thinning behavior, indicating that the droplet-particle network within the emulsion gradually disintegrated under external force. Similar rheological behavior has also been reported in various Pickering emulsion systems. B shows the shear stress versus shear rate curve; the shear stress of all six samples continuously increased with increasing shear rate, indicating that the system has a certain resistance to deformation under shear, which is related to particle-droplet interaction and spatial network structure. Similar studies have found that CNC-SPI emulsions exhibit shear thinning and a shear plateau or thickening behavior under high shear in steady-state flow. This change reflects the relaxation and structural rearrangement process of the particle-droplet network under external shear. C shows the curves of storage modulus (G′) and loss modulus (G″) as a function of oscillating stress. All samples exhibit typical viscoelastic characteristics under oscillating stress. G′ and G″ initially remain relatively stable with increasing oscillating stress, then decrease significantly, indicating that the system gradually transitions from the linear viscoelastic region to the nonlinear viscoelastic region. Specifically, for SECPEs 6:4 and SECPEs 3:7, G′ is significantly higher than G″ in the low stress range, indicating the formation of a relatively stable composite network structure with stronger elastic response and resistance to deformation. D shows the curves of G′ and G″ as a function of angular frequency. For different samples, G′ and G″ increase with increasing angular frequency, showing a clear frequency dependence. For SECPEs 3:7, G′ is consistently higher than G″ throughout the entire frequency range, with the largest difference between the two, indicating that its system exhibits a clear elastic-dominated behavior and has formed a relatively stable three-dimensional network structure. Furthermore, Wang et al. pointed out that the crossover frequency can serve as an important indicator of the deformation resistance of the emulsion network. In this study, the SPEs and SECPEs 5:5 exhibited G″>G′ or near crossover in the low-frequency region, indicating that their internal structure was relatively loose. Overall, the SECPEs 6:4 and SECPEs 3:7 stabilized emulsions showed superior network structure and shear resistance, with SECPEs 3:7 exhibiting the best overall rheological properties.

[0110] Large Amplitude Oscillation (LAOS) behavior and viscoelastic Lissajous plot (see figure) Figures 7 to 16In actual food processing, emulsions often undergo large and rapid deformations, and their response is typically nonlinear. Elastic and viscous lissajous curves of different emulsions under cyclic strain can reveal their nonlinear response. LAOS tests were conducted at a fixed frequency of 1 Hz, with strain amplitude (γ0) set to 100%–1000%. Based on the original oscillation signal, elastic (stress-strain) and viscous (stress-strain rate) lissajous curves were plotted using data at γ0 = 100%, 250%, 500%, 750%, and 1000%. At low strain, the elastic lissajous curve is elongated elliptical, indicating the system is in the linear viscoelastic region (LVR), where elastic energy storage is dominant, and the structure can effectively recover under periodic deformation. Simultaneously, the viscous lissajous curve is approximately circular, indicating lower energy consumption and that the system is primarily elastically dominant. As strain increases, the elastic Lissajous curve gradually becomes rounder and tends towards a parallelogram, indicating that the particle network yields and undergoes an elastic-viscosity transition. Conversely, the viscous Lissajous curve gradually flattens and becomes curved, reflecting enhanced energy dissipation and structural rearrangement. This trend is consistent with previous research results. Studies have shown that as strain increases, the elastic Lissajous curve of the emulsion system changes from an ellipse to a near-parallelogram, while the viscous curve area decreases and secondary ring structures appear, indicating a shift from elastic dominance to viscous dominance, resulting in yielding and reversible microstructural decomposition. Notably, the SECPs 5:5 and 3:7 samples maintained relatively full elastic and viscous Lissajous curves under high strain, demonstrating stronger structural resilience and resistance to deformation. This indicates that the dense composite adsorption layer formed by the particles at the oil-water interface effectively enhances the support of the particle network, enabling the emulsion to maintain high elastic response and energy dissipation performance under repeated loading.

[0111] For the spreadability of the emulsion on bread, see [link to relevant documentation]. Figure 17ECPEs prepared from ECPs and SPEs prepared from SPs were both unstable, exhibiting oil leakage and phase separation. This indicates that emulsion systems stable with a single particle are unable to maintain a complete structure and cannot meet the requirements for further food applications. In contrast, SECPEs prepared from SECPs, especially SECPEs 6:4 and 3:7, were stable, demonstrating that the combination of SPI and EC can effectively improve the stability of the emulsion system and endow it with better structure retention. Further analysis of bread spreading results shows that SECPEs 6:4 have a certain degree of fluidity and can be easily spread and applied to bread, indicating that this sample has good extensibility and spreadability. SECPEs 3:7, on the other hand, have semi-solid properties similar to mayonnaise, and when spread on bread, they resemble the mayonnaise demonstrated by Holey et al. This suggests that under conditions of higher EC content, the emulsion system can form stronger internal structural support, thus maintaining a certain shape even after external forces. The above phenomena are consistent with the conclusions drawn from rheological characterization that SECPEs possess viscoelasticity, indicating that the composite particle stabilized emulsion not only has good stability but also has the potential to be used as a spread. Overall, SECPEs 6:4 is more inclined towards easy spread and easy application, while SECPEs 3:7 is more inclined towards a semi-solid spread system with some shape retention.

[0112] In summary, this study demonstrates that SECPs exhibit higher construction efficiency and stability than single ECPs or SPs in the preparation of O / W type Pickering emulsions. CLSM observation revealed that oil droplets were uniformly dispersed in the aqueous phase with clear interfaces, forming a three-dimensional network in the continuous phase that sterically hindered droplet movement, effectively suppressing aggregation and sedimentation. Optical microscopy further confirmed that SECPEs had more uniform droplet distribution and smaller particle size, while ECPEs showed insufficient interface coverage and more pronounced aggregation, resulting in lower overall stability compared to SECPEs. Rheological analysis revealed that SECPEs 5:5 and 3:7 maintained full elastic and viscous lissajous trajectories under high strain cycling, exhibiting good structural recovery and deformation resistance, confirming the synergistic support of the dense composite adsorption layer and the particle network. Furthermore, SECPEs showed some spreadability, possessing potential as a spreadable paste, while the malleable, semi-solid SECPEs 3:7 showed potential for 3D printing.

[0113] The beneficial effects of this invention are: synergistic particle size refinement; pure EC particles have a particle size greater than 4.6 μm, while the particle size of SPI and EC composites is significantly reduced to 220~350 nm, which is beneficial for uniform adsorption of particles at the oil-water interface; adjustable wettability; by changing the SPI / EC ratio, the contact angle of the composite particles can be controlled within the range of 80°~134°, with the contact angle of the composite particles with a high EC ratio exceeding that of pure EC, exhibiting an unexpected hydrophobic enhancement effect, which is beneficial for irreversible adsorption; reduced interfacial tension; the equilibrium interfacial tension of the composite particles is lower than that of pure SPI and pure EC, indicating a synergistic effect; excellent emulsion stability; the Pickering emulsion stabilized by the composite particles remains in an emulsion state after being stored at room temperature for 3 months without complete demulsification; good rheological properties; the emulsion exhibits shear-thinning characteristics, with a storage modulus G′ greater than the loss modulus G″, maintaining structural recovery force under high strain; food-grade and edible; all raw materials are food-grade and can be used in spreads, functional foods, and 3D printing materials.

[0114] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A composite granule of soy protein isolate and ethyl cellulose, characterized in that, The composite particles are formed by the self-assembly of soy protein isolate and ethyl cellulose under acidic conditions through electrostatic attraction, hydrogen bonding, and hydrophobic interactions. The contact angle of the composite particles is 96.20°~108.16°, the average particle size is 213.1~359.1 nm, and the zeta potential is +20.36 mV~+25.90 mV. Furthermore, the equilibrium interfacial tension of the composite particles at the oil-water interface is lower than that of pure soy protein isolate particles and pure ethyl cellulose particles.

2. The composite particles of soy protein isolate and ethyl cellulose according to claim 1, characterized in that, Based on the total mass of the composite particles, the mass percentage of soy protein isolate is 30% to 60%, and the mass percentage of ethyl cellulose is 40% to 70%.

3. A method for preparing composite particles of soy protein isolate and ethyl cellulose as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Dissolve soy protein isolate in water and adjust the pH to 2.5-3.5 to obtain an aqueous solution of soy protein isolate; S2. Dissolve ethyl cellulose in ethanol, heat and stir until completely dissolved to obtain an ethyl cellulose ethanol solution; S3. While hot, add the ethyl cellulose ethanol solution from step S2 to the soy protein isolate aqueous solution from step S1, and heat and stir at 80-95°C for 0.5-2 hours. S4. Remove ethanol and water to obtain a composite particle dispersion.

4. The method for preparing composite particles of soy protein isolate and ethyl cellulose according to claim 3, characterized in that, In step S4, rotary evaporation is used to remove ethanol and water at a temperature of 40~45℃.

5. The use of the composite particles of soy protein isolate and ethyl cellulose as described in claim 1 or 2 as a stabilizer in the preparation of oil-in-water Pickering emulsions.

6. The application of the composite particles of soy protein isolate and ethyl cellulose according to claim 5, characterized in that, The volume ratio of the oil phase to the water phase in the Pickering emulsion is 1:3 to 3:1, and the mass concentration of the composite particles is 1% to 5%.

7. The application of the composite particles of soy protein isolate and ethyl cellulose according to claim 5, characterized in that, The storage modulus G′ of the Pickering emulsion is greater than the loss modulus G″, and G′ > 10 Pa under the conditions of 1 Hz and 1 Pa.

8. The application of the composite particles of soy protein isolate and ethyl cellulose according to claim 5, characterized in that, The Pickering emulsion is a spreadable sauce.

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