Ternary protein-based composite system and preparation method thereof

Abstract

The invention discloses a ternary protein-based composite system and a preparation method thereof, and relates to the field of functional food and medicines.The protein structures of the ternary protein-based composite system SLE-7, SEL-7, SLE-9 and SEL-9 are obviously changed compared with single soybean protein isolate and binary complexes thereof, and the protein structures of the ternary protein-based composite system SLE-7, SEL-7, SLE-9 and SEL-9 are obviously changed. And the ternary systems have stronger interaction. Through further research, the pH and the adding sequence of the raw materials have obvious influence on the particle size of the compound and the functional characteristics of a compound system. When the pH value is 7, the EAI and ESI of SLE-7 in the ternary complex are the highest; when the pH is 9, the EAI and ESI of SEL-9 in the ternary system are the highest; wherein the SEL-9 has the smallest particle size and the most uniform system, and the SEL-9 composite emulsion has the optimal emulsifying property, so that the application of the SEL-9 composite emulsion in the fields of functional foods and medicines is ensured.

Description

Technical Field

[0001] The present invention relates to the field of functional food and medicine, and in particular to a ternary protein-based composite system and a preparation method thereof. Background Art

[0002] Soy protein isolate (SPI, abbreviated as S in the present invention) plays an important role in the field of food processing due to its good emulsification, gelling, foaming and other functional properties, and scientific processing methods can more effectively improve the application of SPI in the food industry and further broaden its application prospects. The main reason for selecting soy protein isolate in the present invention is that it has extremely high nutritional value and contains essential amino acids for the human body. It is one of the few varieties of plant protein that can replace animal protein. In addition, it has good water solubility, which can avoid the problem that alcohol-soluble proteins are not easy to be directly applied to food.

[0003] Soy lectin (abbreviated as L in the present invention) is an amphiphilic molecule composed of a hydrophobic tail (fatty acid chain) and a hydrophilic head (phosphatidyl substituent). It is an important natural emulsifier and a zwitterionic surfactant widely used in food processing. It can change the secondary structure of protein through hydrophobic interaction, thereby improving the physicochemical and functional properties of protein. It is also rich in nutrition, can reduce serum cholesterol content, treat diabetes, prevent and treat arteriosclerosis, etc., and is suitable for people with three highs. In the present invention, soybean lecithin is selected as the lipid substance because it is obtained from soybeans, aiming to further promote the utilization of the whole soybean plant.

[0004] Epigallocatechin gallate (EGCG, abbreviated as E in the present invention) is a natural hydrophilic polyphenol with abundant phenolic hydroxyl groups, safe and non-toxic, strong antioxidant activity, can prolong the shelf life of food, improve food quality, maintain its original color and nutritional level for a long time, and also makes a significant contribution to the prevention of cancer and cardiovascular disease, and can also promote the interaction with various substances, such as proteins, etc. However, due to its sensitivity to heat and ultraviolet rays, EGCG is also susceptible to oxidation and degradation.

[0005] At present, there is no research on the soy protein isolate-soy lecithin-EGCG ternary composite system. Summary of the invention

[0006] The purpose of the present invention is to propose a ternary protein-based composite system and a preparation method thereof. By compounding soy protein isolate with soy lecithin and EGCG at different pH and addition orders, its physical, chemical and functional properties are studied, and the performance of the composite system is further enhanced, in order to further promote the high-quality development of the protein-based food industry.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows: In the first aspect, the present invention proposes a method for preparing a ternary protein-based composite system, by adjusting the pH value in a soy protein isolate solution and adding soy lecithin and EGCG to obtain a ternary protein-based composite system with a pH of 7-9, wherein the mass ratio of soy protein isolate to soy lecithin is 10:1, and the mass ratio of soy protein isolate to EGCG is 20:1.

[0008] Preferably, in the preparation method of the above-mentioned ternary protein-based composite system, soy lecithin is first added to a soy protein isolate solution with a pH of 7 to obtain a soy protein isolate-soy lecithin binary composite solution, and then EGCG is added to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution.

[0009] Preferably, in the preparation method of the above-mentioned ternary protein-based composite system, EGCG is first added to a soy protein isolate solution with a pH of 9 to obtain a soy protein isolate-EGCG binary composite solution, and then soy lecithin is added to obtain a soy protein isolate-EGCG-soy lecithin ternary composite solution.

[0010] Preferably, the preparation method of the above-mentioned ternary protein-based composite system comprises the following steps: S1, weighing soy protein isolate powder and dissolving it in distilled water, adjusting the pH to 7, magnetically stirring overnight, adding soy lecithin at a mass ratio of soy protein isolate to soy lecithin of 10:1, magnetically stirring for 3 h, and obtaining a soy protein isolate-soy lecithin binary composite solution with a pH of 7; S2. On the basis of the prepared binary composite solution, EGCG was added at a mass ratio of soy protein isolate to EGCG of 20:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 7.

[0011] Preferably, the preparation method of the above-mentioned ternary protein-based composite system comprises the following steps: S1. Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 7, stir magnetically overnight, add EGCG at a mass ratio of soy protein isolate to EGCG of 20:1, stir magnetically for 3 h, and obtain a soy protein isolate-EGCG binary composite solution with a pH of 7; S2. On the basis of the prepared binary composite solution, soybean lecithin was added at a mass ratio of soybean protein isolate to soybean lecithin of 10:1, and magnetic stirring was performed for 3 h to obtain a soybean protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 7.

[0012] Preferably, the preparation method of the above-mentioned ternary protein-based composite system comprises the following steps: S1, weighing soy protein isolate powder and dissolving it in distilled water, adjusting the pH to 9, magnetically stirring overnight, adding soy lecithin at a mass ratio of soy protein isolate to soy lecithin of 10:1, magnetically stirring for 3 h, and obtaining a soy protein isolate-soy lecithin binary composite solution with a pH of 9; S2. On the basis of the prepared binary composite solution, EGCG was added at a mass ratio of soy protein isolate to EGCG of 20:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 9.

[0013] Preferably, the preparation method of the above-mentioned ternary protein-based composite system comprises the following steps: S1. Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 9, stir magnetically overnight, add EGCG at a mass ratio of soy protein isolate to EGCG of 20:1, stir magnetically for 3 h, and obtain a soy protein isolate-EGCG binary composite solution with a pH of 9; S2. On the basis of the prepared binary composite solution, lipid substances were added at a mass ratio of soy protein isolate and soy lecithin of 10:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 9.

[0014] In a second aspect, the present invention provides a ternary protein-based composite system, which is prepared by any of the methods described above.

[0015] Compared with the prior art, the technical effects of the present invention are: The ternary protein-based composite system proposed in the present invention has a significant change in the protein structure of the ternary composite systems SLE-7, SEL-7, SLE-9 and SEL-9 compared to a single soy protein isolate and its binary composite, and the ternary systems have stronger interactions. Through further research, it was found that the pH and the order of addition of the raw materials have a significant effect on the particle size of the composite and the functional properties of the composite system. When the pH is 7, the EAI and ESI of SLE-7 in the ternary composite are both the highest; when the pH is 9, the EAI and ESI of SEL-9 in the ternary system are the highest; among them, SEL-9 has the smallest particle size and the most uniform system, and the SEL-9 composite emulsion has the best emulsifying properties. The above research has obtained several preferred ternary protein-based composite systems, among which SEL-9 is the most preferred ternary protein-based composite system, ensuring the application of the composite system in the field of functional food and medicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A physical picture of the ternary complex provided in an embodiment of the present invention.

[0017] Figure 2This is a fluorescence spectrum diagram of the ternary complex provided in an embodiment of the present invention.

[0018] Figure 3 This is an ultraviolet spectrum of the ternary complex provided by an embodiment of the present invention.

[0019] Figure 4 Fourier infrared spectrum of the ternary complex provided in an embodiment of the present invention.

[0020] Figure 5 This is a DSC thermal enthalpy absolute value diagram of the ternary complex provided in an embodiment of the present invention.

[0021] Figure 6 The particle size and PDI diagram of the ternary complex provided in the embodiment of the present invention.

[0022] Figure 7 A potential diagram of a ternary complex provided by an embodiment of the present invention.

[0023] Figure 8 This is a graph of the emulsification activity and emulsification stability of the ternary complex provided in an embodiment of the present invention.

[0024] Figure 5-8 There are significant differences between data with different letters at the 0.05 level. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present invention.

[0026] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0027] The test materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores. Soy protein isolate was purchased from Shanghai Yuanye Biochemical Technology Co., Ltd. Soy lecithin was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. EGCG was purchased from Xi'an Tongze Biotechnology Co., Ltd.

[0028] 1. Preparation of composite system (1) Soy protein isolate powder was weighed into distilled water, and soy lecithin was added at a mass ratio of 30:1, 25:1, 20:1, 15:1, 10:1, and 5:1 to obtain a soy protein isolate-soy lecithin binary system. Preliminary experiments showed that a mass ratio of 10:1 was the best ratio, with the best emulsification performance and better functional properties.

[0029] (2) Soy protein isolate powder was weighed into distilled water, and EGCG was added at a mass ratio of 50:1, 40:1, 30:1, 20:1, and 10:1 to obtain a soy protein isolate-EGCG binary system. Preliminary experiments showed that a mass ratio of 20:1 was the best ratio, with the best thermal stability and a more uniform system.

[0030] (3) Weigh soy protein isolate powder in distilled water and adjust the pH to 5, 7, 9, and 11. Preliminary experiments show that excessive acidity or alkalinity will affect the protein structure and modify the protein, making it unsuitable for direct application in the food industry. Therefore, pH = 7 / 9 was selected for subsequent experiments.

[0031] (4) Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 7, and stir it magnetically overnight, which is recorded as S-7. Add soy lecithin at a mass ratio of 10:1 and stir it magnetically for 3 h to obtain a soy protein isolate-soy lecithin binary composite solution with a pH of 7, which is recorded as SL-7.

[0032] On the basis of the SL-7 binary composite solution, EGCG was added at a mass ratio of 20:1 and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 7, which was recorded as SLE-7.

[0033] (5) Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 7, and stir it magnetically overnight, which is recorded as S-7. Add EGCG at a mass ratio of 20:1 and stir it magnetically for 3 h to obtain a soy protein isolate-EGCG binary composite solution with a pH of 7, which is recorded as SE-7.

[0034] On the basis of SE-7 binary composite solution, soybean lecithin was added at a mass ratio of 10:1, and magnetic stirring was performed for 3 h to obtain a soybean protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 7, which was recorded as SEL-7.

[0035] (6) Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 9, and stir it magnetically overnight, which is recorded as S-9. Add soy lecithin at a mass ratio of 10:1 and stir it magnetically for 3 h to obtain a soy protein isolate-soy lecithin binary composite solution with a pH of 9, which is recorded as SL-9.

[0036] On the basis of the SL-9 binary composite solution, EGCG was added at a mass ratio of 20:1 and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 9, which was recorded as SLE-9.

[0037] (7) Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 9, and stir it magnetically overnight, which is recorded as S-9. Add EGCG at a mass ratio of 20:1 and stir it magnetically for 3 h to obtain a soy protein isolate-EGCG binary composite solution with a pH of 9, which is recorded as SE-9.

[0038] On the basis of SE-9 binary composite solution, soybean lecithin was added at a mass ratio of 10:1, and magnetic stirring was performed for 3 h to obtain a soybean protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 9, which was recorded as SEL-9.

[0039] 2. Determination of intuitive sample diagram Pour the sample into a colorimetric tube, place the tube on a colorimetric stand, use black flannel as the background, and take a clear picture horizontally.

[0040] like Figure 1 As shown in the figure, the solution colors and transparency obtained by different pH values ​​and different addition orders are very different. The color of the sample at pH 9 is darker than that of the corresponding sample at pH 7. This is because the solubility of the protein is further improved under alkaline conditions, and the structure of the protein is further expanded, which can bind more soybean lecithin and EGCG.

[0041] 3. Determination of fluorescence spectrum Each sample solution was diluted to 0.5 mg / mL with deionized water, and the sample was dropped into a 96-well plate and measured using a fluorescence spectrometer with the excitation wavelength set to 280 nm and the emission spectrum set to 320-400 nm. The obtained fluorescence data were analyzed using Origin software.

[0042] like Figure 2 As shown in the figure, the fluorescence intensity of all complexes is lower than that of proteins and is accompanied by a certain degree of red shift. This is because the binding of soybean lecithin and EGCG to proteins will produce a fluorescence quenching effect. The interaction between them induces a high degree of unfolding of the microstructure of the protein molecule, and the amino acid residues are exposed to a more polar environment. In addition, the fluorescence intensity of the ternary complex with EGCG added first is lower under both pH conditions. This may be because EGCG itself has a fluorescence quenching effect. Adding EGCG first can quench the intrinsic fluorescence of the protein more. Soybean lecithin first binds to the protein and may form a protective layer on the surface of the protein, hindering the interaction between EGCG and the protein. At pH 9, the fluorescence intensity of the single SPI is significantly higher than that at pH 7. This is because under alkaline conditions, the structure of the protein is more stretched, exposing more tryptophan residues, and the internal hydrophobic groups are further exposed on the molecular surface, resulting in an increase in fluorescence intensity.

[0043] 4. Determination of UV spectrum Each sample was diluted to 0.5 mg / mL with deionized water and measured using a UV-visible spectrophotometer. A 1 cm quartz dish was used to scan the absorbance of the sample in the wavelength range of 220–320 nm. The blank solution was deionized water, the slit width was 2 nm, the resolution was 0.2 nm, and the scanning speed was medium. The obtained fluorescence data were analyzed using Origin software.

[0044] like Figure 3 As shown in the figure, under both pH conditions, the addition of soybean lecithin and EGCG will cause an increase in peak intensity and a red shift. In the binary complex, SE has a higher intensity than SL. This is because EGCG has a complex structure and has multiple aromatic rings or functional groups such as hydroxyl groups. It can interact with proteins in various types and cause structural changes. Lipids have a relatively simple structure and usually prefer to interact with hydrophobic regions in proteins. In the ternary system, the peak intensity of SEL-9 is much higher than that of SLE-9. This may be because the covalent binding between polyphenols and proteins can change the structure of proteins to a greater extent and promote the interaction between soybean lecithin and proteins. This is consistent with the results obtained from the fluorescence spectrum.

[0045] 5. Determination of Fourier transform infrared spectroscopy The powdered sample after freeze-drying was mixed with spectral grade potassium bromide at a mass ratio of 1:100, ground and pressed into tablets. All samples were analyzed by Fourier transform infrared spectrometer at 25 °C in the range of 400-4000 cm −1 The measurement was performed in a wavenumber range of 64 scans with a resolution of 4 cm −1 The potassium bromide flakes without mixed samples were used as blank controls. The infrared spectra obtained were analyzed using Origin software.

[0046] like Figure 4 As shown, S-7 has an amide A band at 3286 cm –1 A broad characteristic peak appeared at 1654 cm-1, and the composites showed a slight red shift or blue shift compared with the original ones, which was attributed to the stretching vibration of OH and NH between molecules, indicating that hydrogen bonding occurred between the composites. –1 and 1542cm –1 The peaks near the 200 nm wavelength also slightly red-shifted, which are attributed to the CN, C=O stretching vibrations, N-H bending vibrations, C-N, and C-C stretching vibrations, indicating that electrostatic interactions are formed between the complexes. At pH 7, soybean lecithin and EGCG mainly bind to proteins through hydrogen bonds and hydrophobic forces. At pH 9, the SE-9 and SEL-9 covalent complexes have a higher peak at 3290 cm-1 than S-9. –1The change in the intensity of the characteristic peak at is reduced, which may be because the hydroxyl group of EGCG is oxidized to quinone under alkaline conditions, resulting in a decrease in the hydroxyl content and weakening the formation of hydrogen bonds. The change in the peak intensity of SE-9 between amide I and amide II bands may be because EGCG covalently binds to SPI and participates in CN and NH vibrations.

[0047] 6. Determination of thermal stability Weigh 4-5 mg of the freeze-dried powder sample and place it in a crucible. Use an empty crucible as a control. Put the sample crucible and the empty crucible together into the instrument and take them out after the measurement. The test starts at 20°C and is heated at 10°C / min to a reaction termination temperature of 200°C. The nitrogen flow rate is 50 mL / min. After the test, use the analysis software matched with the instrument to analyze the thermal characteristics of the sample.

[0048] like Figure 5 As shown in the figure, at pH 7, with the addition of soybean lecithin and EGCG, the absolute value of the enthalpy of the complex showed a decreasing trend, indicating that the energy required to destroy the system was reduced. At pH 9, after the addition of EGCG (SE-9 compared with S-9, SLE-9 compared with SL-9), the absolute value of the enthalpy increased significantly, because the quinone generated by EGCG under alkaline conditions reacted with the sulfhydryl or amino group in SPI to form a more ordered complex through covalent interactions of CS or CN bonds, which made it have higher thermal stability.

[0049] 7. Determination of particle size and PDI The sample solution was diluted to 1 mg / mL with ultrapure water, and the particle size and polydispersity index (PDI) of the sample were measured by dynamic light scattering (DLS) using a nanoparticle size analyzer.

[0050] like Figure 6 As shown in the figure, under the two pH conditions, the particle size of all complexes increased, among which the particle size of SLE-7 and SLE-9 was larger than that of SEL-7 and SEL-9, respectively. This is because when SPI and EGCG come into contact first, the binding of protein and soybean lecithin will be reduced, and the molecular structure of soybean lecithin itself is larger. At pH 7, the particle size of the ternary system showed an increasing trend, while at pH 9, the particle size of the ternary complex decreased significantly. In addition, it is worth noting that the overall particle size at pH 9 is larger than that at pH 7, especially the particle size of SL-9, 518.23 ± 10.90 nm, which is significantly higher than the particle size of SL-7, 273.90 ± 8.65 nm. It can be seen from the PDI value that after adding the third substance, the PDI value decreased, among which SEL-9 reached the lowest value of 0.27 ± 0.01.

[0051] 8. Determination of potential The sample solution was diluted to 1 mg / mL with ultrapure water, and the zeta potential of the sample was measured by dynamic light scattering (DLS) using a nanoparticle size potential analyzer.

[0052] like Figure 7 As shown in the figure, all samples show negative values. This is because under these two pH conditions, soy protein isolate itself carries a large amount of negative charge, and soy lecithin and EGCG can also provide negative charge for the complex. Therefore, the combination of the two with protein can increase the negative charge on the surface of protein particles and increase the absolute value of potential. The absolute values ​​of potential of SE-9, SLE-9, and SEL-9 are higher than those of SE-7, SLE-7, and SEL-7, respectively. This is attributed to the fact that EGCG generates quinone compounds in an alkaline environment, and quinone carries a negative charge in the covalent complex.

[0053] 9. Determination of emulsification activity and emulsification stability Take the prepared emulsion, dilute it 100 times with SDS (0.1%), and measure its absorbance at 500nm at 0 min and 10 min. The emulsification activity (EAI) is expressed as the absorbance at 0 min, and the emulsification stability (ESI) is calculated as follows. 10 T0 and T 10 0 min and 10 min respectively.

[0054]

[0055] like Figure 8 As shown in the figure, at pH 7, the EAI and ESI of SL-7 in the binary complex were the highest, and the EAI and ESI of SLE-7 in the ternary complex were the highest. This is because soybean lecithin is a good emulsifier, which can reduce the interfacial tension of each component in the system and form a relatively strong film or a double electric layer on the surface of the droplets to prevent the aggregation of droplets. It first combines with the protein in the system and can form a more stable protective layer at the emulsion interface when forming an emulsion, preventing the aggregation and merging of oil droplets and maintaining the uniformity of the emulsion. Although the interaction between EGCG and protein can enhance the flexibility of the protein and cause the hydrophobic amino acids and active sites buried in the protein molecules to be exposed on the protein surface, thereby improving the adsorption efficiency of the protein at the oil-water interface, its ability is relatively poor compared with that of special emulsifiers. At pH 9, the EAI of SL-9 in the binary system was the highest, the ESI of SE-9 was the highest, and the EAI and ESI of SEL-9 in the ternary system were the highest. This may be because EGCG first covalently interacts with SPI to improve the balance between the hydrophilicity and hydrophobicity of the protein.

[0056] Based on the above experimental results, we draw the following conclusions: (1) The color of the sample can be visually observed to show that more protein is dissolved under alkaline conditions and more soy lecithin and EGCG are combined.

[0057] (2) Fluorescence and ultraviolet spectroscopy tests showed that soybean lecithin, EGCG and protein interacted with each other, changing the microenvironment of the protein's amino acid residues.

[0058] (3) Infrared spectroscopy results show that the binding of non-covalent complexes is mainly driven by hydrogen bonds and hydrophobic forces.

[0059] (4) DSC measurements showed that the structure of the complex was more ordered and that more energy was required to destroy it.

[0060] (5) Through the measurement of particle size, PDI and potential, it was found that adding EGCG first would reduce the binding of protein and soybean lecithin and thus reduce the particle size. The covalent binding under alkaline conditions would increase the particle size of the complex. Among them, SEL-7 had the smallest particle size and SEL-9 had the most uniform system.

[0061] (6) The test of emulsion activity and emulsion stability showed that the emulsion performance was significantly improved after adding soy lecithin and EGCG.

[0062] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a ternary protein-based composite system, characterized in that: The pH value of the soy protein isolate solution was adjusted, and soy lecithin and EGCG were added to obtain a ternary protein-based composite system with a pH of 7-9, wherein the mass ratio of the soy protein isolate to the soy lecithin was 10:1, and the mass ratio of the soy protein isolate to the EGCG was 20:

1.

2. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: When the pH of the soy protein isolate solution is 7, soy lecithin is first added to obtain a soy protein isolate-soy lecithin binary composite solution, and then EGCG is added to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution.

3. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: When the pH value of the soy protein isolate solution is 9, EGCG is first added to obtain a soy protein isolate-EGCG binary composite solution, and then soy lecithin is added to obtain a soy protein isolate-EGCG-soy lecithin ternary composite solution.

4. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: The following steps are involved: S1, weighing soy protein isolate powder and dissolving it in distilled water, adjusting the pH to 7, magnetically stirring overnight, adding soy lecithin at a mass ratio of soy protein isolate to soy lecithin of 10:1, magnetically stirring for 3 h, and obtaining a soy protein isolate-soy lecithin binary composite solution with a pH of 7; S2. On the basis of the prepared binary composite solution, EGCG was added at a mass ratio of soy protein isolate to EGCG of 20:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 7.

5. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: The following steps are involved: S1. Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 7, stir magnetically overnight, add EGCG at a mass ratio of soy protein isolate to EGCG of 20:1, stir magnetically for 3 h, and obtain a soy protein isolate-EGCG binary composite solution with a pH of 7; S2. On the basis of the prepared binary composite solution, soybean lecithin was added at a mass ratio of soybean protein isolate to soybean lecithin of 10:1, and magnetic stirring was performed for 3 h to obtain a soybean protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 7.

6. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: The following steps are involved: S1, weighing soy protein isolate powder and dissolving it in distilled water, adjusting the pH to 9, magnetically stirring overnight, adding soy lecithin at a mass ratio of soy protein isolate to soy lecithin of 10:1, magnetically stirring for 3 h, and obtaining a soy protein isolate-soy lecithin binary composite solution with a pH of 9; S2. On the basis of the prepared binary composite solution, EGCG was added at a mass ratio of soy protein isolate to EGCG of 20:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-soy lecithin-EGCG ternary composite solution with a pH of 9.

7. The method for preparing the ternary protein-based composite system according to claim 1, characterized in that: The following steps are involved: S1. Weigh soy protein isolate powder and dissolve it in distilled water, adjust the pH to 9, stir magnetically overnight, add EGCG at a mass ratio of soy protein isolate to EGCG of 20:1, stir magnetically for 3 h, and obtain a soy protein isolate-EGCG binary composite solution with a pH of 9; S2. On the basis of the prepared binary composite solution, lipid substances were added at a mass ratio of soy protein isolate and soy lecithin of 10:1, and magnetic stirring was performed for 3 h to obtain a soy protein isolate-EGCG-soy lecithin ternary composite solution with a pH of 9.

8. A ternary protein-based composite system, characterized in that: The method according to any one of claims 1 to 7 is used for the preparation.

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