Modification method for improving solubility of soybean protein

Abstract

The invention relates to the technical field of food processing, in particular to a modification method for improving solubility of soybean protein. The method comprises the following steps: carrying out heat treatment on a first solution containing soybean protein and inorganic acid; and performing cold plasma treatment on the first solution subjected to heat treatment to obtain a second solution. According to the physical and chemical synergistic superposition modification method provided by the embodiment of the invention, the cold plasma treatment is performed after the protein is subjected to deamidation modification by using the inorganic acid, so that the dissolvability is remarkably improved on the basis of not prolonging the deamidation reaction time, and the dissolvability is greatly improved. And moreover, the problem of protein molecular weight change caused by excessive deamidation is effectively solved, the deamidation reaction time is shortened, and industrial production is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and particularly relates to a method for preparing highly soluble soy protein by modifying deamidation with cold plasma in cooperation with inorganic acid. Background Art

[0002] In 2023, the global plant protein market size reached as high as $9.7 billion, and the average annual compound growth rate in the past five years was 7.31%. Due to differences in lifestyle and eating habits, the obesity rate is higher in many regions such as the United States and the United Kingdom. According to the 2022 United Nations Sustainable Development Goals Report, approximately 41% of adults in the United States are facing obesity problems. Plant proteins such as soybeans and other legume proteins are becoming increasingly popular among consumers in developed regions due to their low fat content and sufficient micronutrients. At the same time, influenced by concepts such as healthy eating and vegetarianism, most consumers are turning to plant proteins and meat substitutes, and it is expected that the global demand for plant proteins will continue to increase in the future. Soy protein is the main source of plant-based protein. However, due to the influence of its spatial structure, the functional properties of natural soy protein, such as solubility, emulsifying property, foaming property, and gelling property, are relatively poor, and usually present problems such as weak continuity, low water-holding capacity, and discontinuity of extrusion products. Therefore, it has great economic value to study the physical and chemical properties with commercially available soy protein as a representative.

[0003] Among the various physical and chemical properties of proteins, solubility, as one of the most important physical and chemical properties, will directly affect various functional properties such as emulsifying property and rheological properties. For this, many new physical and chemical treatment methods have been developed by experts at home and abroad. Physical methods include ultra-high pressure, microwave, ultrasound, pulsed electric field, and cold plasma, etc. Chemical methods such as glycosylation modification, deamidation modification, and fibrillation treatment, etc.

[0004] In related technologies, the protein structure is mainly modified by physical or chemical methods to achieve the purpose of improving the solubility of soy protein. Among them, deamidation modification will induce asparagine and glutamine to contact with H + to transform into carboxyl groups with strong hydrophilicity, thus resulting in an increase in hydrophilicity. Therefore, deamidation modification has become an effective means to improve protein solubility. Researchers have tried to increase the degree of deamidation and solubility by extending the treatment time. However, long-term deamidation will cause excessive hydrolysis of proteins, which not only destroys the nutritional components of proteins but also produces disadvantages such as bitter peptides.

[0005] Therefore, there is an urgent need to propose a method that can not only improve the degree of deamidation and solubility of soy protein but also avoid significant changes in the molecular weight of soy protein. Summary of the Invention

[0006] The present invention solves at least one of the problems of the related technologies from the following aspects.

[0007] In the first aspect of the embodiments of the present invention, a method for modifying soy protein is provided, including: performing heat treatment on a first solution containing soy protein and inorganic acid; and performing cold plasma treatment on the heat-treated first solution to obtain a second solution.

[0008] The embodiments of the present invention provide a superposition modification method of physical and chemical synergy. By using inorganic acid to perform deamidation modification on proteins and then performing cold plasma treatment, on the basis of not prolonging the deamidation reaction time, not only is the solubility significantly improved, but also the problem of protein molecular weight change caused by excessive deamidation is effectively solved, which helps to shorten the deamidation reaction time and promote industrial production.

[0009] In some embodiments, the first solution contains soy protein powder with a mass fraction of 1% (w / v) - 3% (w / v), preferably 1.5% (w / v) - 2.5% (w / v), and more preferably 2% (w / v).

[0010] In some embodiments, the first solution contains 0.1M - 0.3M of inorganic acid, preferably 0.15M - 0.25M, and more preferably 0.2M.

[0011] Compared with the use of organic acids such as tartaric acid and citric acid, the use of inorganic acids such as hydrochloric acid significantly improves the solubility and deamidation degree of the prepared soy protein.

[0012] In some embodiments, the inorganic acid is HCl.

[0013] In some embodiments, the heat treatment of the first solution containing soy protein and inorganic acid includes: maintaining the first solution at 65 - 75 °C, preferably 70 °C for 2 - 4 h, preferably 3 h.

[0014] In some embodiments, the cold plasma treatment of the heat-treated first solution includes: using a cold plasma reaction device to treat the heat-treated first solution for 5 min - 25 min at a power of 75 W - 80 W, preferably 80 W.

[0015] In some embodiments, the cold plasma treatment of the heat-treated first solution includes: using a cold plasma reaction device, with air as the gas source, treating the heat-treated first solution for 5 min - 25 min at a power of 75 W - 80 W, preferably 80 W and a current of 1 ± 0.2 A.

[0016] In some embodiments, the method for modifying soy protein further includes: dissolving soy protein powder in water to obtain a soy protein solution; maintaining the soy protein solution at 2°C - 8°C, preferably 3°C - 5°C for 6 - 18 h, preferably 8 - 12 h, to obtain a hydrated soy protein solution; and mixing the hydrated soy protein solution with the inorganic acid to obtain the first solution.

[0017] In some embodiments, after mixing the hydrated soy protein solution with the inorganic acid to obtain the first solution, the first solution is heat-treated within a time of less than or equal to 10 min, preferably less than or equal to 5 min.

[0018] In some embodiments, after obtaining the heat-treated first solution, the heat-treated first solution is subjected to the cold plasma treatment within a time of less than or equal to 10 min, preferably less than or equal to 5 min.

[0019] In some embodiments, the method for modifying soy protein further includes: adjusting the pH of the second solution to 6.5 - 7.5, preferably 7.0, and then freeze-drying to obtain modified soy protein.

[0020] Compared with the related art, the embodiments of the present application at least achieve the following beneficial effects:

[0021] The present invention provides a novel dual modification method combining physics and chemistry. By using inorganic acid to deamidate and modify proteins and then performing cold plasma treatment, the superimposed modification of physical means and chemical means is realized. The method provided by the embodiments of the present invention has a significant effect on improving the solubility of soy protein, and the raw material sources are widespread and the operation is simple, meeting the needs of future large-scale industrial production and having great application prospects. Description of the Drawings

[0022] Figure 1 It is a bar chart of the surface hydrophobicity index of soy protein provided by the embodiments and comparative examples of the present invention;

[0023] Figure 2 It is a bar chart of the Zeta potential of soy protein provided by the embodiments and comparative examples of the present invention;

[0024] Figure 3 It is a gel electrophoresis diagram of soy protein provided by the embodiments and comparative examples of the present invention. Detailed Embodiments

[0025] The present invention will be further described in detail below in conjunction with the specific embodiments. The provided embodiments are only for clarifying the present invention and do not limit the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements and do not limit the present invention in any way.

[0026] In the present invention, the term "comprising" is an open expression, that is, it includes the content specified in the present invention, but does not exclude other aspects of the content.

[0027] The present invention is made based on the following understanding of the inventors:

[0028] Cold plasma, as a harmless processing technology for improving the specific functional activity of food components, has attracted much attention in the food industry. Cold plasma has the advantages of simple equipment, low cost, and green and high efficiency. Cold plasma is the fourth state of matter composed of a series of substances such as positive and negative ions, electrons, and free radicals generated after gas atoms are ionized. Based on its strong oxidative modification ability and non-thermal characteristics, it shows great potential in the modification of heat-sensitive food components.

[0029] The embodiment of the present invention provides a superposition modification method combining physics and chemistry. After deamidation modification of proteins with inorganic acids and then cold plasma treatment, without prolonging the deamidation reaction time, not only is the solubility significantly improved, but also the problem of protein molecular weight change caused by over-deamidation is effectively solved. To some extent, it helps to shorten the deamidation reaction time and promote industrial production. Through the implementation of this patent, prominent problems such as poor functionality, serious homogenization, and insufficient research and development of new products in the soybean protein processing industry can be solved, contributing to the development of the soybean protein industry and enhancing the technical level and international competitiveness of China's soybean protein industry.

[0030] The embodiment of the present invention provides a modification method for soybean protein, including steps S200 - S300.

[0031] S200: Heat-treat a first solution containing soybean protein and inorganic acid.

[0032] In some embodiments, the first solution contains soybean protein powder with a mass fraction of 1% (w / v) - 3% (w / v) (for example: 1.1% (w / v), 1.2% (w / v), 1.3% (w / v), 1.4% (w / v), 1.5% (w / v), 1.6% (w / v), 1.7% (w / v), 1.8% (w / v), 1.9% (w / v), 2.0% (w / v), 2.1% (w / v), 2.2% (w / v), 2.3% (w / v), 2.4% (w / v), 2.5% (w / v), 2.6% (w / v), 2.7% (w / v), 2.8% (w / v), 2.9% (w / v)), preferably 1.5% (w / v) - 2.5% (w / v), and more preferably 2% (w / v).

[0033] As an example, the soybean protein used in the embodiment of the present invention is soy protein isolate.

[0034] In some embodiments, the first solution comprises an inorganic acid with a concentration of 0.1M - 0.3M (such as 0.11M, 0.12M, 0.13M, 0.14M, 0.15M, 0.16M, 0.17M, 0.18M, 0.19M, 0.20M, 0.21M, 0.22M, 0.23M, 0.24M, 0.25M, 0.26M, 0.27M, 0.28M, 0.29M), preferably 0.15M - 0.25M, and more preferably 0.2M.

[0035] In some embodiments, the inorganic acid is HCl.

[0036] In some embodiments, S100 further includes: maintaining the first solution at 65°C - 75°C (such as 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C), preferably at 70°C, for 2 - 4 h (such as 2.5 h, 3 h, 3.5 h, 4 h), and preferably for 3 h.

[0037] S300: Performing cold plasma treatment on the heat-treated first solution to obtain a second solution.

[0038] In some embodiments, S200 further includes: using a cold plasma reaction device to treat the heat-treated first solution at a power of 75W - 80W (such as 76W, 77W, 78W, 79W), preferably 80W, for 5 min - 25 min (such as 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min).

[0039] In some embodiments, S200 further includes: using a cold plasma reaction device, with air as the gas source, treating the heat-treated first solution at a power of 75W - 80W, preferably 80W, and a current of 1 ± 0.2 A for 5 min - 25 min.

[0040] As an example, the model of the cold plasma reaction device is DBD - 150 (Nanjing Suman Plasma Technology Co., Ltd., China).

[0041] In some embodiments, before step S200, the soybean protein modification method provided by the embodiments of the present invention further includes step S100: Preparation of the first solution.

[0042] In some embodiments, S100 includes S101 - S103.

[0043] S101: Dissolve soy protein powder in water to obtain a soy protein solution.

[0044] S102: Keep the soy protein solution at 2°C - 8°C (such as 3°C, 4°C, 5°C, 6°C, 7°C), preferably 3°C - 5°C for 6 - 18 h (such as 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h), preferably 8 - 12 h, to obtain a hydrated soy protein solution.

[0045] S103: Mix the hydrated soy protein solution and the inorganic acid to obtain the first solution.

[0046] In some embodiments, after mixing the hydrated soy protein solution and the inorganic acid to obtain the first solution, heat-treat the first solution within a time less than or equal to 10 min (such as 0.1 min, 0.2 min, 0.3 min, 0.4 min, 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1.0 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min), preferably less than or equal to 5 min.

[0047] That is to say, the time interval between step S103 and step S200 does not exceed 10 min, preferably does not exceed 5 min. Exceeding this time range will cause an increase in the degree of protein hydrolysis.

[0048] In some embodiments, after obtaining the heat-treated first solution, perform the cold plasma treatment on the heat-treated first solution within a time less than or equal to 10 min (such as 0.1 min, 0.2 min, 0.3 min, 0.4 min, 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1.0 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min), preferably less than or equal to 5 min.

[0049] That is to say, the time interval between step S200 and step S300 does not exceed 10 min, preferably does not exceed 5 min. Exceeding this time range will cause an increase in the degree of protein hydrolysis.

[0050] In some embodiments, the method for modifying soy protein provided by the embodiments of the present invention further includes step 400: after adjusting the pH value of the second solution to 6.5 - 7.5, preferably 7.0, freeze-drying to obtain the modified soy protein.

[0051] The following embodiments are used to further illustrate the advantages and characteristics of the method, rather than limiting the present invention. The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions.

[0052] The solution of the present invention will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those without specific techniques or conditions noted in the embodiments, they are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0053] The present invention will be further described below in conjunction with specific embodiments. It should be noted that for the field of improving the solubility of soy protein by cold plasma synergistic inorganic acid deamidation modification, without departing from the principle of the present invention, several variations and improvements can also be made, which should also be regarded as belonging to the protection scope of the present invention.

[0054] Unless otherwise specified, in the following embodiments, quantitative analysis tests are all set with three repeated experiments, and the results are averaged.

[0055] Example 1:

[0056] Step S100: Mix commercially available soy protein powder (product model: S9510, manufacturer: Beijing Solarbio Science & Technology Co., Ltd.) and water to obtain a protein solution (4.0%, w / v), and place it in a 4°C refrigerator for overnight hydration.

[0057] Step S200: Immediately mix the protein solution obtained in step S1 with HCl solution (0.4M) at a ratio of 1:1 (v / v), and then carry out water bath heating (70°C, 3h) to obtain a mixed solution.

[0058] Step S300: Immediately treat the mixed solution after water bath heating in step S2 with cold plasma (power 80W, current 1 ± 0.2A, treatment time 5min) to obtain a deamidated protein solution.

[0059] Step S400: Adjust the pH of the deamidated protein solution obtained in step S3 to 7.0 with NaOH solution (1.0M), and freeze-dry for 48h to obtain highly soluble soy protein.

[0060] Example 2:

[0061] Step S100: Mix commercially available soy protein powder and water to obtain a protein solution (4.0%, w / v), and place it in a refrigerator at 4 °C for overnight hydration.

[0062] Step S200: Immediately mix the protein solution obtained in Step S1 with HCl solution (0.4 M) at a ratio of 1:1 (v / v), and then immediately carry out water bath heating (70 °C, 3 h) to obtain a mixed solution.

[0063] Step S300: Immediately treat the mixed solution after water bath heating in Step S2 with cold plasma (power 80 W, current 1 ± 0.2 A, treatment time 15 min) to obtain a deamidated protein solution.

[0064] Step S400: Adjust the pH of the deamidated protein solution obtained in Step S3 to 7.0 using NaOH solution (1.0 M), and obtain highly soluble soy protein after freeze-drying for 48 h.

[0065] Example 3:

[0066] Step S100: Mix commercially available soy protein powder and water to obtain a protein solution (4.0%, w / v), and place it in a refrigerator at 4 °C for overnight hydration.

[0067] Step S200: Immediately mix the protein solution obtained in Step S1 with HCl solution (0.4 M) at a ratio of 1:1 (v / v), and then immediately carry out water bath heating (70 °C, 3 h) to obtain a mixed solution.

[0068] Step S300: Immediately treat the mixed solution after water bath heating in Step S2 with cold plasma (power 80 W, current 1 ± 0.2 A, treatment time 25 min) to obtain a deamidated protein solution.

[0069] Step S400: Adjust the pH of the deamidated protein solution obtained in Step S3 to 7.0 using NaOH solution (1.0 M), and obtain highly soluble soy protein after freeze-drying for 48 h.

[0070] Comparative Example 1

[0071] Commercially available soy protein powder without any treatment (product model: S9510, manufacturer: Beijing Solarbio Science & Technology Co., Ltd.).

[0072] Comparative Example 2

[0073] This example provides a method for preparing deamidated soy protein. The difference between this comparative example and Examples 1 - 3 is that during the preparation process, cold plasma treatment is no longer carried out. The specific steps are as follows:

[0074] Step S100: Mix commercially available soy protein powder and water to obtain a protein solution (4.0%, w / v), and place it in a refrigerator at 4 °C for overnight hydration.

[0075] Step S200: Immediately mix the protein solution obtained in Step S1 with HCl solution (0.4 M) at a ratio of 1:1 (v / v), and then perform water bath heating (70 °C, 3 h) to obtain a mixed solution.

[0076] Step S400: Adjust the pH of the mixed solution obtained in Step S2 to 7.0 using NaOH solution (1.0 M), and obtain deamidated soy protein after freeze-drying for 48 h.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 1 is only that the acid used in Step S200 is tartaric acid.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 1 is only that the acid used in Step S200 is citric acid.

[0081] Comparative Example 5

[0082] The difference between this comparative example and Example 1 is only that the water bath heating time in Step S200 is 30 min.

[0083] Performance Analysis

[0084] Solubility measurement method: Prepare a protein sample solution of 5 mg / mL in deionized water. Centrifuge at 4000 g for 10 min to collect the supernatant. Uniformly mix reagent A (containing 10 mg / mL bicinchoninic acid, 20 mg / mL anhydrous sodium carbonate, 1.6 mg / mL sodium tartrate, 4 mg / mL sodium hydroxide, and 9.5 mg / mL sodium bicarbonate, adjust the pH to 11.25) and reagent B (40 mg / mL copper sulfate) at a ratio of 50:1 (v / v) to obtain a color-developing solution. Dissolve bovine serum albumin in 0.01 M phosphate buffer to obtain protein solutions of 0, 0.1, 0.2, 0.3, 0.4, 0.5 mg / mL, and establish a bovine serum standard protein calibration curve. Mix the supernatant or bovine serum albumin solution with the color-developing solution at a ratio of 1:10 (v / v), and incubate at 37 °C for 20 min. Measure the absorbance value at 562 nm using an ultraviolet spectrophotometer (UV2550, Shimadzu Corporation, Japan), and calculate the solubility (mg / mL) of the protein sample according to the bovine serum standard protein calibration curve.

[0085] Method for determining deamidation degree: Accurately weigh 0.2 g of protein sample and mix it with 0.2 g of CuSO4, 3.0 g of K2SO4 and 10 mL of H2SO4 in a glass digestion tube, and perform gradient temperature rise digestion (220 °C - 250 °C - 280 °C - 320 °C - 370 °C - 420 °C, heating up once every 30 min, and finally maintaining at 420 °C for 1 h) to achieve complete deamidation. Collect the digestion solution, and after it cools down, use a Kjeldahl nitrogen analyzer (KDY-8920, Tongrunyuan Company, China) to measure the ammonia content. The receiving flask contains 10 mL of boric acid (20 g / L) and 100 μL of bromocresol green-methyl red mixed indicator. After the Kjeldahl nitrogen analyzer finishes distillation, remove the receiving flask and titrate it with 0.1 M standard hydrochloric acid solution, and calculate the ammonia content in the sample. The protein deamidation degree (%) is calculated by the ammonia content A of the untreated soy protein and the ammonia content B of the sample after deamidation treatment ((A - B) / A * 100%).

[0086] The solubility of the highly soluble soy proteins prepared in Comparative Examples 1-5 and Examples 1-3 was analyzed, and the results are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] It can be seen from Table 1 that the highly soluble soy proteins prepared in Examples 1-3 of this application have good solubility. Compared with Comparative Examples 1-4, the solubility improvement effect of the highly soluble soy proteins prepared in Examples 1-3 is significant.

[0091] The deamidation degrees of the highly soluble soy proteins prepared in Comparative Examples 2-4 and Examples 1-3 were analyzed, and the results are shown in Table 2.

[0092] Table 2

[0093] Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Degree of deamidation (%) 31.45±0.48 28.71±0.44 26.25±0.30 33.18±0.71 37.42±0.18 37.11±0.48

[0094] It can be seen from Table 2 that the highly soluble soy proteins prepared in Examples 1-3 of this application have good deamidation efficiency.

[0095] Figure 1 It is a comparative graph of the surface hydrophobicity of the highly soluble soy proteins prepared in Comparative Examples 1-2 and Example 1. Through Figure 1It can be seen that the highly soluble soy protein prepared in the embodiments of the present application has good surface hydrophobicity and does not show a significant increase compared with Comparative Example 2, indicating that cold plasma treatment does not change the number of hydrophobic groups on the surface of deamidated proteins. This helps to improve the adsorption capacity of the protein at the two-phase interface without affecting the solubility of the modified protein, thereby contributing to the improvement of the emulsifying properties of the protein.

[0096] Figure 2 Figure for comparing the Zeta potential of the highly soluble soy proteins prepared in Comparative Examples 1-2 and Example 1. By Figure 2 It can be seen that since deamidation causes neutral amide residues to transform into negatively charged carboxyl groups, and the oxidative modification of cold plasma also leads to the generation of negatively charged products, the highly soluble soy protein prepared in the embodiments of the present application has good electrostatic interaction, thus contributing to the improvement of the solubility of the protein.

[0097] Figure 3 Figure for comparing the gel electrophoresis of the highly soluble soy proteins prepared in Comparative Examples 1-2 and Example 1. By Figure 2 It can be seen that the deamidation reaction is accompanied by peptide bond cleavage, resulting in inevitable hydrolysis of proteins. However, compared with Comparative Example 2, the molecular weight of the highly soluble soy protein prepared in the embodiments of the present application has not changed significantly.

[0098] The solubility of the soy protein prepared by the method provided by the present invention is significantly improved. The results show that the soy protein developed by the synergistic deamidation modification of cold plasma and inorganic acid can effectively improve the solubility, which is beneficial to the improvement of various functional properties such as emulsifying properties and rheological properties, providing technical guidance for the processing and regulation of high-performance emulsion foods in the food industry.

[0099] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0100] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for modifying soybean protein, characterized in that: include: heat-treating a first solution comprising soybean protein and an inorganic acid; The heat-treated first solution is subjected to cold plasma treatment to obtain a second solution.

2. The method according to claim 1, characterized in that The first solution contains soy protein powder in an amount of 1% (w / v) to 3% (w / v), preferably 1.5% (w / v) to 2.5% (w / v), and more preferably 2% (w / v).

3. The method according to claim 1, characterized in that The first solution contains 0.1M-0.3M, preferably 0.15M-0.25M, more preferably 0.2M of the inorganic acid.

4. The method according to claim 1, characterized in that: The inorganic acid is HCl.

5. The method according to claim 1, characterized in that The heat treatment of the first solution containing soy protein and inorganic acid comprises: maintaining the first solution at 65° C.-75° C., preferably 70° C., for 2-4 hours, preferably 3 hours.

6. The method according to claim 1, characterized in that The performing cold plasma treatment on the heat-treated first solution comprises: using a cold plasma reaction device to treat the heat-treated first solution at a power of 75W-80W, preferably 80W, for 5min-25min.

7. The method according to claim 1, characterized in that The cold plasma treatment of the heat-treated first solution includes: using a cold plasma reaction device, using air as a gas source, treating the heat-treated first solution with a power of 75W-80W, preferably 80W, and a current of 1±0.2A for 5min-25min.

8. The method according to claim 1, characterized in that Also includes: dissolving soy protein powder in water to obtain a soy protein solution; Maintaining the soy protein solution at 2°C-8°C, preferably 3°C-5°C for 6-18 hours, preferably 8-12 hours, to obtain a hydrated soy protein solution; The hydrated soybean protein solution and the inorganic acid are mixed to obtain the first solution.

9. The method according to claim 8, characterized in that After mixing the hydrated soy protein solution and the inorganic acid to obtain the first solution, heat-treating the first solution for a time of less than or equal to 10 minutes, preferably less than or equal to 5 minutes; Optionally, after obtaining the heat-treated first solution, the cold plasma treatment is performed on the heat-treated first solution for a time period of less than or equal to 10 minutes, preferably less than or equal to 5 minutes.

10. The method according to claim 1, characterized in that Also includes: The pH value of the second solution is adjusted to 6.5-7.5, preferably 7.0, and then freeze-dried to obtain the modified soybean protein.

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