A globulin-egcg complex, emulsion and preparation method and application thereof

Abstract

The application discloses a wheat germ albumin-EGCG compound, an emulsion and a preparation method and application thereof, and relates to the field of food emulsifiers. The wheat germ albumin-EGCG compound comprises wheat germ albumin and EGCG, and the mass molar ratio of the wheat germ albumin and the EGCG is 1:50-350 (g:μmol). The preparation method of the wheat germ albumin-EGCG compound is simple and efficient, and the application value and resource utilization rate of wheat germ protein are improved. The prepared wheat germ albumin-EGCG non-covalent compound is used as an emulsifier of an oil-in-water / oil-in-water emulsion, effectively improves the anti-fat oxidation and protein oxidation capacity of the emulsion, and further improves the stability and nutritional value of the emulsion.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food emulsifiers, in particular to a wheat germ albumin-EGCG complex, an emulsion and a preparation method and application thereof. BACKGROUND

[0002] Wheat germ protein has similar emulsifying properties and stability to bovine serum albumin, good foaming capacity and water retention, but its resources have not been fully utilized, and most of them are used for animal feed. According to statistics, the storage of wheat germ in the world is as high as 25 million tons per year. In recent years, scholars at home and abroad have modified wheat germ protein by various physical and chemical methods to improve its application value, such as electron beam irradiation, low-temperature microwave treatment, etc. However, most of the researches are aimed at total wheat germ protein, and the methods used are mostly based on physical modification. The functions of modified wheat germ protein are evaluated, but the targeting is not strong. There are very limited modification methods for wheat germ albumin, which is the most abundant protein in wheat germ protein and bears most of the physiological functions. Therefore, its application value and resource utilization should be improved.

[0003] Food emulsifiers have a broad market in food production in China, and have a promising development prospect, especially in cakes, chocolates, ice creams and lactic acid beverages. Emulsions are generally composed of two immiscible liquids, one of which is dispersed in the form of droplets in the other, such as oil-in-water (O / W) or water-in-oil (W / O) emulsion. People usually add some stabilizers to prevent emulsion from flocculation and coalescence. Compared with environmentally unfriendly surfactants, proteins, starches and polysaccharides are often used to stabilize emulsions.

[0004] Chinese patent CN105639651A discloses a preparation method and application of a polyphenol-protein / polypeptide-carbohydrate covalent complex. The preparation method of the complex is as follows: taking polyphenol and protein / polypeptide as raw materials, using alkali method to induce reaction to prepare polyphenol-protein / polypeptide covalent complex; then taking carbohydrate and the prepared polyphenol-protein / polypeptide covalent complex as raw materials, using Maillard reaction to prepare polyphenol-protein / polypeptide-carbohydrate covalent complex, and using the covalent complex to stabilize β-carotene emulsion. The preparation method of the complex is complex, and is only applied to β-carotene emulsion.

[0005] Chinese patent CN116172184A discloses a kind of emulsion prepared by soybean protein isolate, sodium alginate, EGCG complex to improve emulsion emulsification and stability. The emulsion preparation method is as follows: first, obtain soybean protein isolate-sodium alginate complex solution, then add different proportions of polyphenols to obtain soybean protein isolate-sodium alginate-EGCG ternary complex solution. Then, with ternary complex solution as water phase, corn oil as oil phase, mix homogeneously at a ratio of 4:1 to obtain emulsion. The complex preparation method is complex, and only corn oil is used as oil phase, which is not comprehensive.

[0006] The two-component complex prepared by the present application, wheat germ albumin-EGCG complex, has a simpler and more efficient preparation method and is easy to produce. The present application uses wheat germ albumin and EGCG as raw materials to prepare wheat germ albumin-EGCG non-covalent complex. The reaction conditions of non-covalent interaction are milder, and the activity of functional active ingredients is lower. The prepared wheat germ albumin-EGCG non-covalent complex as an emulsifier of oil-in-water / water-in-oil emulsion effectively improves the anti-lipid oxidation and protein oxidation capacity of the emulsion, thereby improving the stability and nutritional value of the emulsion. SUMMARY

[0007] Therefore, in view of the deficiencies in the prior art, the present application aims to provide a simpler and more efficient preparation method of wheat germ albumin-EGCG non-covalent complex, to improve the application value and resource utilization rate of wheat germ protein. The prepared wheat germ albumin-EGCG non-covalent complex as an emulsifier of oil-in-water / water-in-oil emulsion effectively improves the anti-lipid oxidation and protein oxidation capacity of the emulsion, thereby improving the stability and nutritional value of the emulsion.

[0008] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0009] On the one hand, the present application provides a wheat germ albumin-EGCG complex, which comprises wheat germ albumin and EGCG, and the mass molar ratio of wheat germ albumin to EGCG is 1:50-350 (g:pmol).

[0010] Preferably, the mass molar ratio of wheat germ albumin to EGCG is 1:50-300, further preferably 1:150-200, and more preferably 1:150.

[0011] Preferably, the preparation method of wheat germ albumin comprises the following steps:

[0012] Mix defatted wheat germ powder and water, heat and dissolve, separate supernatant, adjust the pH of supernatant to be acidic, separate precipitate, adjust the pH of precipitate to be neutral, dry to obtain wheat germ albumin.

[0013] Preferably, the mass-volume ratio of the mixture of defatted wheat germ powder and water is 1:5-20, further preferably 1:5-15, and more preferably 1:10.

[0014] Preferably, the heating and dissolving condition is 20-60℃, further preferably 30-50℃, and more preferably 40℃.

[0015] Preferably, the method for separating the supernatant includes, but is not limited to, centrifugation, decantation, filtration, sedimentation, and flotation, further preferably centrifugation or decantation, and more preferably centrifugation.

[0016] Preferably, the supernatant pH adjustment refers to adjusting the pH of the supernatant to 3.0-5.0, further preferably 3.5-4.5, and more preferably 4.0.

[0017] Preferably, the supernatant pH adjustment can use perchloric acid, hydroiodic acid, sulfuric acid, hydrobromic acid, hydrochloric acid, nitric acid, or iodic acid. In a specific embodiment of the present application, hydrochloric acid is used.

[0018] Preferably, the method for separating the precipitate includes, but is not limited to, centrifugation, decantation, filtration, sedimentation, and flotation, further preferably centrifugation or decantation, and more preferably centrifugation.

[0019] Preferably, the precipitate pH adjustment can use potassium hydroxide, sodium hydroxide, calcium hydroxide, or barium hydroxide. In a specific embodiment of the present application, sodium hydroxide is used.

[0020] Preferably, the drying method includes, but is not limited to, freeze drying, vacuum drying, air flow drying, microwave drying, infrared drying, and high frequency drying, further preferably freeze drying or vacuum drying, and more preferably freeze drying. More preferably, the specific conditions of freeze drying are a temperature of -10℃ to -90℃ and a vacuum degree of 1.3-13 Pa. More preferably, the specific conditions of freeze drying are a temperature of -80℃ and a vacuum degree of 8 Pa.

[0021] The EGCG is epigallocatechin gallate, with a chemical formula of C 22 H 18 O 11 .

[0022] In another aspect, the present application provides a preparation method of the above-mentioned wheat germ albumin-EGCG complex, comprising the following steps:

[0023] (1) Dissolving the wheat germ albumin in solvent 1, stirring until complete hydration to obtain a protein solution;

[0024] (2) Dissolving the EGCG in solvent 2 to obtain an EGCG solution;

[0025] (3) mixing the protein solution obtained in step (1) and the EGCG solution obtained in step (2), treating in the dark, dialyzing, drying to obtain the said complex of gliadin-EGCG.

[0026] Preferably, in step (1) and step (2), the said solvent 1 and solvent 2 are selected from at least one of HBSS buffer solution, PBS buffer solution, further preferably PBS buffer solution, and more further preferably PBS buffer solution with a concentration of 5mM and pH 7.0.

[0027] Preferably, in step (1), the said stirring time is 12-24h, further preferably 16-20h, and more further preferably 18h.

[0028] Preferably, in step (1), the mass concentration of the said protein solution is 0.1%-3%, further preferably 0.5%-2%, and more further preferably 1%.

[0029] Preferably, in step (2), the molar concentration of the said EGCG solution is 1-350μmol / g, preferably 50-300μmol / g, further preferably 150-200μmol / g, and more further preferably 150μmol / g.

[0030] Preferably, in step (3), the said mixing is carried out at a temperature of 20-30℃ and a pH of 6.8-7.2, further preferably at a temperature of 25℃ and a pH of 7.0.

[0031] Preferably, in step (3), the said mixing is carried out by slowly adding the EGCG solution to the protein solution.

[0032] Preferably, in step (3), the said treatment in the dark is carried out for 12-24h, further preferably 16-20h, and more further preferably 18h.

[0033] Preferably, in step (3), the said dialysis is carried out using a dialysis membrane with a molecular weight cut-off of 3kDa.

[0034] Preferably, in step (3), the said dialysis is carried out for 40-56h, further preferably 44-52h, and more further preferably 48h.

[0035] Preferably, in step (3), the drying method includes, but is not limited to, freeze drying, vacuum drying, air flow drying, microwave drying, infrared drying, high frequency drying, further preferably freeze drying, vacuum drying, and more preferably freeze drying, and more preferably freeze drying at a temperature of -10℃ to 90℃ and a vacuum degree of 1.3 to 13 Pa.

[0036] In another aspect, the present application provides the use of the above-mentioned glutelin-EGCG complex or the glutelin-EGCG complex prepared according to the above-mentioned preparation method in the preparation of an emulsion.

[0037] In another aspect, the present application provides an emulsion comprising the above-mentioned glutelin-EGCG complex and vegetable oil.

[0038] Preferably, the mass ratio of the glutelin-EGCG complex and the vegetable oil is 5-13:1, further preferably 7-11:1, and more preferably 9:1.

[0039] Preferably, the vegetable oil is selected from at least one of walnut oil, corn oil, soybean oil, olive oil, and wheat germ oil, further preferably at least one of corn oil and soybean oil, and more preferably soybean oil.

[0040] In another aspect, the present application provides a preparation method of the above-mentioned emulsion, comprising the steps of mixing the glutelin-EGCG complex and the vegetable oil, and homogenizing to obtain the emulsion.

[0041] Preferably, the homogenization process includes, but is not limited to, high-pressure homogenization, high-shear emulsification, and micro-jet homogenization.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] (1) The present application prepares a glutelin-EGCG non-covalent complex, and the preparation method is simple and efficient, which improves the application value and resource utilization rate of glutelin.

[0044] (2) The glutelin-EGCG non-covalent complex prepared by the present application effectively improves the anti-fat oxidation and protein oxidation capacity of the oil-in-water / oil-in-water emulsion, and further improves the stability and nutritional value of the emulsion. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The preparation flowchart of the present application is shown in the figure.

[0046] Figure 2A graph comparing the particle size and Zeta potential of the emulsions obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, in which the line graph represents the Zeta potential and the column graph represents the particle size.

[0047] Figure 3 A graph comparing the particle size and Zeta potential of the emulsions obtained in Example 1, Example 6, Example 7, Example 8, Example 9, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, in which the line graph represents the Zeta potential and the column graph represents the particle size.

[0048] Figure 4 A graph comparing the particle size and Zeta potential of the emulsions obtained in Example 1, Example 10, Example 11, Example 12, Example 13, in which the line graph represents the Zeta potential and the column graph represents the particle size.

[0049] Figure 5 A graph comparing the lipid hydroperoxide content of the emulsions obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, in which each group of data from left to right represents the lipid hydroperoxide content of the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, Example 2, Example 3, Example 4, Example 5.

[0050] Figure 6 A graph comparing the lipid hydroperoxide content of the emulsions obtained in Example 1, Example 6, Example 7, Example 8, Example 9, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, in which each group of data from left to right represents the lipid hydroperoxide content of the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 6, Example 7, Example 1, Example 8, Example 9.

[0051] Figure 7 A graph comparing the lipid hydroperoxide content of the emulsions obtained in Example 1, Example 10, Example 11, Example 12, Example 13 at different times, in which each group of data from left to right represents the lipid hydroperoxide content of the emulsions obtained in Example 10, Example 11, Example 1, Example 12, Example 13.

[0052] Figure 8 A graph comparing the malondialdehyde content of the emulsions obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, in which each group of data from left to right represents the malondialdehyde content of the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, Example 2, Example 3, Example 4, Example 5.

[0053] Figure 9 A comparison chart of the content of malondialdehyde in the emulsions obtained in Example 1, Example 6, Example 7, Example 8, Example 9, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, wherein each group of data from left to right represents the content of malondialdehyde in the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 6, Example 7, Example 1, Example 8, Example 9.

[0054] Figure 10 A comparison chart of the content of malondialdehyde in the emulsions obtained in Example 1, Example 10, Example 11, Example 12, Example 13 at different times, wherein each group of data from left to right represents the content of malondialdehyde in the emulsions obtained in Example 10, Example 11, Example 1, Example 12, Example 13.

[0055] Figure 11 A comparison chart of the content of sulfhydryl groups in the emulsions obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, wherein each group of data from left to right represents the content of sulfhydryl groups in the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, Example 2, Example 3, Example 4, Example 5.

[0056] Figure 12 A comparison chart of the content of sulfhydryl groups in the emulsions obtained in Example 1, Example 6, Example 7, Example 8, Example 9, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 at different times, wherein each group of data from left to right represents the content of sulfhydryl groups in the emulsions obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 6, Example 7, Example 1, Example 8, Example 9.

[0057] Figure 13 A comparison chart of the content of sulfhydryl groups in the emulsions obtained in Example 1, Example 10, Example 11, Example 12, Example 13 at different times, wherein each group of data from left to right represents the content of sulfhydryl groups in the emulsions obtained in Example 10, Example 11, Example 1, Example 12, Example 13.

[0058] Figure 14 The droplet morphology of the emulsions obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11, Example 12, Example 13, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4. DETAILED DESCRIPTION

[0059] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following further illustrates the present application with specific examples. However, the following examples are only preferred embodiments of the present application, not all. Based on the examples in the embodiments, other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0060] The present application is further illustrated below in the manner of specific examples. The various chemical reagents used in the embodiments of the present application are obtained through conventional commercial channels unless otherwise specified. The contents described below are mass contents unless otherwise specified. It is understood that the operations are carried out at room temperature unless otherwise specified.

[0061] Example 1

[0062] (1) Defatted wheat germ powder (Shandong Youkang Natural Plant Technology Co., Ltd.) was dispersed in water at a ratio of 1:10 (w / v), stirred at 40℃ for 2h, and then centrifuged at 7000rpm for 15min. The supernatant obtained after centrifugation was adjusted to pH 4.0 with HCl (1.0M), and the precipitate obtained after centrifugation was adjusted to pH 7.0 with NaOH (1.0M). The precipitate was freeze-dried to obtain wheat germ albumin. The specific conditions for freeze-drying were a temperature of -80℃ and a vacuum degree of 8Pa.

[0063] (2) Wheat germ albumin was dissolved in PBS buffer (5mM, pH 7.0) at a concentration of 1% (w / v), and the protein solution was continuously stirred overnight to ensure complete hydration, obtaining a wheat germ albumin solution with a volume of 1000mL. EGCG (Shanghai Maikelin Biotechnology Co., Ltd., purity 99%) was dissolved in PBS buffer (5mM, pH 7.0) at a concentration of 50μmol / g, obtaining an EGCG solution with a mass of 10g. Under the conditions of a temperature of 25℃ and a pH of 7.0, the EGCG solution was slowly added to the wheat germ albumin solution, and the mixture was incubated in the dark with shaking for 12h, followed by dialysis in water (3kDa molecular weight cutoff filter) for 48h. After freeze-drying, wheat germ albumin-EGCG complex was obtained. The specific conditions for freeze-drying were a temperature of -80℃ and a vacuum degree of 8Pa.

[0064] (3) Wheat germ albumin-EGCG complex was dissolved in PBS buffer (5mM, pH 7.0) at a concentration of 1% (w / v), and the wheat germ albumin-EGCG complex solution and soybean oil were mixed uniformly at a ratio of 9:1 (v / v), and an emulsion was obtained by high-speed homogenization at 10000rpm for 2min.

[0065] Example 2

[0066] The difference between Example 2 and Example 1 is that the concentration of EGCG is replaced by 150μmol / g, and the rest is the same.

[0067] Example 3

[0068] The difference from Example 1 is that the concentration of EGCG was replaced with 200 μmol / g, while everything else remained the same.

[0069] Example 4

[0070] The difference from Example 1 is that the concentration of EGCG was replaced with 300 μmol / g, while the rest were the same.

[0071] Example 5

[0072] The difference from Example 1 is that the concentration of EGCG was replaced with 350 μmol / g, while the rest were the same.

[0073] Example 6

[0074] The difference from Example 1 is that the concentration of wheat germ albumin was replaced with 0.1%, while the rest remained the same.

[0075] Example 7

[0076] The difference from Example 1 is that the concentration of wheat germ albumin was replaced with 0.5%, while the rest remained the same.

[0077] Example 8

[0078] Unlike Example 1, the concentration of wheat germ albumin was replaced with 2%, while the rest remained the same.

[0079] Example 9

[0080] Unlike Example 1, the concentration of wheat germ albumin was replaced with 3%, while the rest remained the same.

[0081] Example 10

[0082] The difference from Example 1 is that soybean oil is replaced with walnut oil, otherwise they are the same.

[0083] Example 11

[0084] The difference from Example 1 is that soybean oil is replaced with corn oil, otherwise they are the same.

[0085] Example 12

[0086] The difference from Example 1 is that soybean oil is replaced with olive oil, otherwise the same.

[0087] Example 13

[0088] The difference from Example 1 is that soybean oil is replaced with wheat germ oil, otherwise the same.

[0089] Comparative Example 1

[0090] Different from Example 1, step (2) was omitted, and the glutelin-EGCG complex was replaced by glutelin, and the rest were the same.

[0091] Comparative Example 2

[0092] Different from Example 1, step (1), step (2) was omitted, and the glutelin-EGCG complex was replaced by soybean protein (Beijing Solabio Technology Co., Ltd., purity more than 90%), and the rest were the same.

[0093] Comparative Example 3

[0094] Different from Example 1, glutelin was replaced by soybean protein, and the rest were the same.

[0095] Comparative Example 4

[0096] Different from Example 1, EGCG was replaced by chlorogenic acid (Shanghai Maikelin Biological Technology Co., Ltd., purity 99%), and the rest were the same.

[0097] Results detection:

[0098] 1, Particle size detection

[0099] 1.1, Particle size detection method

[0100] The sample was diluted 50 times with PBS buffer to avoid multiple scattering effects. The average particle size was measured by dynamic light scattering method. The emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was used as the sample, and the particle size of the sample was determined at 25°C using a Malvern nanoparticle size potential instrument (Zetasizer Nano ZS).

[0101] 1.2, Particle size detection results

[0102] The emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was used as the sample, and the particle size of the emulsion was tested according to the above method, and the results are shown in Table 1.

[0103] Table 1. Particle size detection results

[0104] Group Particle size / μm Group Particle size / μm Example 1 1.45±0.26 Example 10 2.57±0.62 Example 2 0.81±0.17 Example 11 1.22±0.11 Example 3 0.95±0.27 Example 12 6.63±1.04 Example 4 1.95±0.28 Example 13 2.05±0.52 Example 5 2.56±0.07 Comparative Example 1 1.90±0.32 Example 6 6.22±0.44 Comparative Example 2 3.15±0.34 Example 7 3.02±0.41 Comparative Example 3 2.38±0.35 Example 8 2.74±0.20 Comparative Example 4 1.67±0.13 Example 9 3.50±0.42 —— ——

[0105] 2, Potential detection

[0106] 2.1, Potential detection method

[0107] The emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was used as the sample, and the Zeta potential value of the sample was determined at 25°C using a Malvern nanoparticle size potential instrument (Zetasizer Nano ZS).

[0108] 2.2, Potential detection results

[0109] The emulsions obtained in Examples 1-13 and Comparative Examples 1-4 were used as samples, and the Zeta potential of the emulsions was tested according to the above method, and the results are shown in Table 2.

[0110] Table 2. Potential detection results

[0111]

[0112]

[0113] 3, Droplet morphology detection

[0114] 3.1, Droplet morphology detection method

[0115] The microstructure of the emulsions obtained in Examples 1-13 and Comparative Examples 1-4 was observed by optical microscope, and the images were recorded. The emulsions were diluted 5 times with PBS buffer, then dropped on a glass slide (10 μL), and microscopically observed with a 20x objective lens.

[0116] 3.2, Droplet morphology detection results

[0117] The emulsions obtained in Examples 1-13 and Comparative Examples 1-4 were used as samples, and the morphology change of the droplets was observed according to the above method, and the results are shown in the attached Figure 14

[0118] 4, Lipid oxidation level detection of emulsion

[0119] 4.1, Lipid oxidation level detection method of emulsion

[0120] The emulsion was placed for 7 days, and the hydrogen peroxide and malondialdehyde contents in the emulsion were determined using a hydrogen peroxide content determination kit (Beijing Solabio Technology Co., Ltd.) and a malondialdehyde content determination kit (Beijing Solabio Technology Co., Ltd.) to characterize the lipid oxidation level of the emulsion. The specific operation is as follows: take 250 μL of the emulsion obtained in Examples 1-13 and Comparative Examples 1-4, add 25 μL of reagent two and 50 μL of reagent three in the kit according to the kit instructions, at the same time, set up a blank control by replacing the sample with acetone, and replace the sample with a 2 mmol / mL hydrogen peroxide standard solution as a standard tube, centrifuge all samples at 10000 rpm for 10 min at room temperature, discard the supernatant and leave the precipitate, add 250 μL of reagent four, dissolve the precipitate, and then stand for 5 min at room temperature, transfer 200 μL to a 96-well plate, and determine the absorbance at 415 nm.

[0121] Hydrogen peroxide content (μmol / g) = 2 x ΔA measured ÷ ΔA standard ÷ W

[0122] ​Wherein, ΔA measured = A measured - A blank, ΔA standard = A standard - A blank, and W is the mass of the oil.

[0123] The content of malondialdehyde was also determined according to the kit instructions, and the specific operation was as follows: 200 μL of the emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was taken, 600 μL of malondialdehyde working solution and 200 μL of reagent three in the kit were added, and the sample was replaced with distilled water to set up a blank control. The mixed solution was heated in boiling water for 60 min, cooled, centrifuged at 10,000 rpm for 10 min, and 200 μL of supernatant was transferred to a 96-well plate to determine the absorbance at 532 nm and 600 nm.

[0124] Malondialdehyde content (μmol / kg) = 53.763 x ΔA ÷ W

[0125] Wherein, ΔA532 = A532 测定 - A532 空白 , ΔA600 = A600 测定 - A600 空白 , ΔA = ΔA532 - ΔA600, and W is the mass of the sample.

[0126] 4.2, Results of detection of the lipid oxidation level of the emulsion

[0127] The hydrogen peroxide content in the emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was determined by referring to the above method, and the results are shown in Table 3.

[0128] Table 3. Results of determination of hydrogen peroxide content

[0129]

[0130]

[0131] The malondialdehyde content in the emulsion obtained in Examples 1-13 and Comparative Examples 1-4 was determined by referring to the above method, and the results are shown in Table 4.

[0132] Table 4. Results of determination of malondialdehyde content

[0133]

[0134] 5, Detection of the protein oxidation level of the emulsion

[0135] 5.1, Method for detecting the protein oxidation level of the emulsion

[0136] The emulsions were left for 7 days and the thiol content in the emulsions was determined to characterize the protein oxidation level of the emulsions. The detection procedure was as follows: 1 mL of emulsion was mixed with 5 mL of urea (8 M, Fuhen (Tianjin) Chemical Reagent Co., Ltd.), 0.05 mL of 5,5'-dithiobis(2-nitrobenzoic acid) (4 mg / mL, Shanghai Yinn Chemical Technology Co., Ltd.) was added, and the reaction was carried out in the dark for 90 min, and then the absorbance of the sample at 412 nm was determined. The content of thiol was calculated using the following formula:

[0137] μM SH / g = (73.53 · A 412 ·D) / C

[0138] A 412 is the absorbance of the sample at 412 nm, D is the dilution ratio, and C is the concentration of the sample.

[0139] 5.2, Results of the detection of the lipid oxidation level of the emulsions

[0140] The emulsions obtained in Examples 1-13 and Comparative Examples 1-4 were taken as samples, and the thiol content in the emulsions was determined according to the above method, and the results are shown in Table 5.

[0141] Table 5. Results of the determination of the thiol content

[0142] Group Thiol content / μM at 0 days Thiol content / μM at 3 days Thiol content / μM at 6 days Example 1 37.07±2.04 36.39±0.68 35.60±0.04 Example 2 33.32±1.48 30.58±0.94 32.69±0.53 Example 3 31.75±0.41 29.42±0.17 28.36±0.84 Example 4 28.33±2.06 26.48±0.45 26.25±0.19 Example 5 25.50±0.98 24.26±1.18 23.69±0.22 Example 6 24.07±3.04 26.45±0.33 19.89±0.47 Example 7 32.43±1.02 29.93±0.63 24.90±0.72 Example 8 39.33±1.34 36.79±0.21 37.33±0.65 Example 9 48.13±0.30 41.58±0.42 38.52±1.72 Example 10 40.02±0.45 36.66±0.26 33.25±0.64 Example 11 38.57±0.33 36.91±0.28 36.38±0.17 Example 12 41.79±0.52 36.79±0.20 29.38±0.72 Example 13 43.80±0.89 42.13±0.85 38.55±0.19 Comparative Example 1 45.35±1.49 36.60±1.21 33.73±0.79 Comparative Example 2 58.13±0.81 53.91±0.54 52.63±1.72 Comparative Example 3 42.80±1.49 38.22±1.31 37.29±1.44 Comparative Example 4 40.33±0.73 38.08±1.70 36.14±0.28

[0143] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A non-covalent complex of wheat germ albumin and EGCG, characterized in that, It is composed of wheat germ albumin and EGCG, wherein the mass molar ratio of wheat germ albumin to EGCG is 1g:50-350μmol; The method for preparing the wheat germ albumin-EGCG complex includes the following steps: (1) Dissolve wheat germ albumin in a buffer solution and stir until completely hydrated to obtain a protein solution with a w / v concentration of 1%; (2) Dissolve EGCG in a buffer solution to obtain an EGCG solution with a molar concentration of 50-350 μmol / g; (3) Mix the protein solution obtained in step (1) and the EGCG solution obtained in step (2), treat in the dark, dialyze, and dry to obtain the wheat germ albumin-EGCG non-covalent complex. The mixing conditions in step (3) are: temperature of 20-30℃, pH of 6.8-7.2, and light-protected treatment time of 12-24h.

2. The wheat germ albumin-EGCG nonvalent complex according to claim 1, characterized in that, The molar ratio of wheat germ albumin to EGCG is 1g:50-300μmol.

3. The wheat germ albumin-EGCG nonvalent complex according to claim 1, characterized in that, The molar ratio of wheat germ albumin to EGCG is 1g:150-200μmol.

4. The wheat germ albumin-EGCG nonvalent complex according to claim 1, characterized in that, The molar ratio of wheat germ albumin to EGCG is 1g:150μmol.

5. The wheat germ albumin-EGCG non-covalent complex according to claim 1, characterized in that, The molar concentration of the EGCG solution is 50-300 μmol / g.

6. The wheat germ albumin-EGCG nonvalent complex according to claim 1, characterized in that, The molar concentration of the EGCG solution is 150-200 μmol / g.

7. The use of the wheat germ albumin-EGCG nonvalent complex according to any one of claims 1-6 in the preparation of emulsions.

8. An emulsion, characterized in that, It comprises the wheat germ albumin-EGCG non-covalent complex according to any one of claims 1-6 and a vegetable oil, wherein the vegetable oil is selected from at least one of corn oil and soybean oil.

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