Soy protein product and method of making same

Abstract

The application relates to the food field and discloses a soybean protein product and a preparation method thereof, the method comprising the following steps: performing grinding and centrifugal treatment on soybeans and water to obtain residue-removed soybean milk and soybean residue; performing cold precipitation and centrifugal treatment on the residue-removed soybean milk to obtain a cold precipitation and a cold precipitation supernatant; performing ultrafiltration treatment on the cold precipitation supernatant to collect a retentate; respectively drying the cold precipitation and the retentate to obtain a cold precipitation dry product and a retentate dry product; and mixing the cold precipitation dry product and the retentate dry product to obtain the soybean protein product. The soybean protein product prepared by the method has all the essential amino acids for human bodies, the proportion of the essential amino acids is close to the ideal amino acid composition, and the soybean protein product has high nutritional value. Moreover, the method is simple in operation, low in cost and suitable for large-scale production.

Description

Technical Field

[0001] This application relates to the food industry, specifically to soybean protein products and their preparation methods. Background Technology

[0002] Modern nutrition science believes that the quality of food protein depends mainly on the types, quantities, and proportions of essential amino acids it contains. The closer the proportions are to the proportions of amino acids needed by the human body, the higher its nutritional value.

[0003] However, current technologies only focus on: utilizing the nutritional properties of other substances to promote the absorption of soybean protein, without improving the soybean itself; improving the extraction efficiency or functional properties of soybean protein through changes in extraction methods, but neglecting its nutritional value; and enhancing the nutritional value of soybean protein through microbial fermentation. None of these methods address the issue of low nutritional value of plant proteins from the perspective of amino acid ratios, resulting in the underutilization of the inherent value of plant proteins. Summary of the Invention

[0004] This application aims to at least partially address the technical problems existing in the prior art. To this end, this application proposes soybean protein products and a method for their preparation. Soybean protein products prepared using the method of this application contain all essential amino acids for the human body, and their proportions are close to the ideal amino acid composition, resulting in high nutritional value. Furthermore, the method is simple to operate, low in cost, and suitable for large-scale production.

[0005] In one aspect of this application, a method for preparing soybean protein products is provided. According to an embodiment of this application, the method includes: grinding and centrifuging soybeans and water to obtain soybean milk and soybean residue; subjecting the soybean milk to cold sedimentation and centrifugation to obtain cold sedimentation precipitate and cold sedimentation supernatant; subjecting the cold sedimentation supernatant to ultrafiltration and collecting the retentate; drying the cold sedimentation precipitate and retentate separately to obtain dried cold sedimentation material and dried retentate material; and mixing the dried cold sedimentation material and dried retentate material to obtain the soybean protein product; wherein the mass ratio of the dried cold sedimentation material to the dried retentate material is 1:(0.2~3).

[0006] Currently, the main method for extracting soybean protein is alkali dissolution followed by acid precipitation. However, despite extensive experimental design and adjustments to the extraction parameters, the inventors were unable to obtain soybean protein with a near-ideal amino acid composition. Therefore, the inventors explored alternative extraction methods and, through extensive theoretical analysis and experimental optimization, combined cold precipitation and ultrafiltration. By blending the extracts obtained from both methods in a specific ratio, they achieved a soybean protein product containing all essential amino acids in proportions close to the ideal amino acid composition. Specifically: First, soybeans and water are ground into a slurry. Mechanical force disrupts the cell wall structure of the soybeans, allowing soluble components such as proteins to be fully released into the water, forming a homogeneous slurry. Next, a cold precipitation process is used. Low temperature induces changes in the protein structure, causing disulfide bonds to cross-link and increasing hydrophobicity, thus forming a molecular polymer precipitate. This process achieves selective precipitation: protein subunits containing more hydrophobic residues are more likely to precipitate at low temperatures, while the remaining protein remains in the solution (i.e., the cold precipitation supernatant). This initially separates soybean protein into two categories: "cold precipitation precipitate protein" and "cold precipitation supernatant protein," with differences in their amino acid compositions. Then, the cold precipitation supernatant is ultrafiltered to retain the protein components with differing amino acid compositions, i.e., the retained product. Finally, the dried cold precipitation precipitate and the retained product are mixed at a mass ratio of 1:(0.2~3) to obtain a soybean protein product containing all essential amino acids, with a proportion close to the ideal amino acid composition for humans, resulting in high nutritional value.

[0007] According to embodiments of this application, the method for preparing soybean protein products may further include the following additional technical features: According to embodiments of this application, the mass ratio of the cold-sinking dried material to the retained dried material is 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, or 1:3. Therefore, the soybean protein products formulated according to this ratio contain all essential amino acids for the human body, and their proportions are close to the ideal amino acid composition, resulting in high nutritional value.

[0008] According to embodiments of this application, the mass-to-volume ratio of soybeans to water is 1:(5~10), in g / mL. In some embodiments, the mass-to-volume ratio of soybeans to water is 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, in g / mL. This ensures efficient protein extraction, avoids excessive viscosity and insufficient extraction due to insufficient water, and prevents excessive water from causing low protein concentration, which is detrimental to subsequent processing and increases unnecessary waste.

[0009] According to embodiments of this application, the cold settling treatment is performed at a temperature of 2-6°C for 14-18 hours. In some embodiments, the cold settling treatment is performed at temperatures of 2°C, 3°C, 4°C, 5°C, and 6°C for 14 hours, 15 hours, 16 hours, 17 hours, and 18 hours, respectively. This effectively promotes cross-linking of soybean protein molecules through disulfide bonds and enhances hydrophobicity, thereby forming a stable polymer precipitate. This process not only helps preserve the natural conformation and biological activity of the protein but also avoids protein denaturation that may be caused by high temperatures or harsh treatments, thus improving protein recovery.

[0010] According to embodiments of this application, the pore size of the ultrafiltration membrane used in the ultrafiltration process is 100-180 kDa. In some embodiments, the pore size of the ultrafiltration membrane used in the ultrafiltration process is 100 kDa, 120 kDa, 140 kDa, 150 kDa, 160 kDa, or 180 kDa. This allows for the effective separation of target soybean protein components, facilitating the enrichment of protein fragments with larger molecular weights, while allowing small molecule impurities (such as salts and oligopeptides) to pass through smoothly, improving the high recovery rate of the target protein, and avoiding easy clogging and decreased flux due to excessively small pores, or loss of the target protein due to excessively large pores.

[0011] According to embodiments of this application, the pressure of the ultrafiltration process is 0.2~0.6 MPa. In some embodiments, the pressure of the ultrafiltration process is 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or 0.6 MPa. This facilitates further separation of the target protein, resulting in a soybean protein product rich in amino acids.

[0012] According to embodiments of this application, the ultrafiltration temperature is 30-40°C. In some embodiments, the ultrafiltration temperature is 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, or 40°C. This facilitates further separation of the target protein, resulting in a soybean protein product containing all essential amino acids in proportions close to the ideal amino acid composition.

[0013] In another aspect, this application discloses a soy protein product. According to an embodiment of this application, the soy protein product is obtained by the method for preparing soy protein products described above. Therefore, the soy protein product of this application contains all essential amino acids for the human body, and their proportions are close to the ideal amino acid composition, resulting in high nutritional value.

[0014] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0015] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the process for preparing soybean protein products according to an embodiment of this application is shown. Detailed Implementation

[0016] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] This application discloses a method for preparing soybean protein products. According to embodiments of this application, see [link to embodiment]. Figure 1 The method includes: Soybeans were ground into a slurry with water at a ratio of 1:8 (g / ml) at 80℃, and the soybean residue was removed by centrifugation. The resulting soy milk was then placed at 4℃ for 16 hours for cold settling, followed by centrifugation to separate the precipitate and supernatant. The supernatant was then passed through a 150kDa membrane at 0.4MPa and 35℃ to obtain a 150kDa retentate. The precipitate and 150kDa retentate were freeze-dried and then reconstituted to obtain soy protein products.

[0019] This application utilizes two green technologies, cold sedimentation and ultrafiltration membrane separation, to obtain two types of soybean protein—cold sedimentation protein and ultrafiltration protein. By combining these technologies, a highly nutritious soybean protein product is obtained, which is rich in amino acids and closely resembles the composition of essential amino acids for the human body.

[0020] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0021] Example 1 1. At a temperature of 80℃, soybeans are ground into a slurry with water at a material-to-liquid ratio of 1:8 (g / ml), and then centrifuged to obtain soybean residue and soybean milk after removing the residue.

[0022] 2. After the sludge-free soy milk is placed at 4℃ for 16 hours to settle, it is centrifuged at 10000×g at 4℃ for 20 minutes to separate the precipitate and the supernatant.

[0023] 3. The supernatant was cooled and filtered through a 150kDa ultrafiltration membrane at 0.4MPa and 35℃ to obtain a 150kDa retentate.

[0024] 4. Freeze-dry the cold precipitation and 150kDa retentate into powder, and then compound them at a mass ratio of 2:1 to obtain soybean protein products.

[0025] Example 2 Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows: 4. Freeze-dry the cold precipitation and 150kDa retentate into powder, and then compound them at a mass ratio of 1:1 to obtain soybean protein products.

[0026] Example 3 Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows: 4. Freeze-dry the cold precipitation and 150kDa retentate into powder, and then compound them at a mass ratio of 1:2 to obtain soybean protein products.

[0027] Example 4 Soy protein products were prepared according to the method in Example 1, except that the cold settling time was 12 h.

[0028] Example 5 Soy protein products were prepared according to the method in Example 1, except that the cold settling time was 20 h.

[0029] Example 6 Soy protein products were prepared according to the method of Example 1, except that the pore size of the ultrafiltration membrane was 30 kDa.

[0030] Example 7 Soy protein products were prepared according to the method of Example 1, except that the pore size of the ultrafiltration membrane was 200 kDa.

[0031] Comparative Example 1 1. At a temperature of 80℃, soybeans are ground into a slurry with water at a material-to-liquid ratio of 1:8 (g / ml), and then centrifuged to obtain soybean residue and soybean milk after removing the residue.

[0032] 2. After the sludge-free soy milk is placed at 4℃ for 16 hours to settle, it is centrifuged at 10000×g at 4℃ for 20 minutes to separate the precipitate and obtain soy protein products.

[0033] Comparative Example 2 1. At a temperature of 80℃, soybeans are ground into a slurry with water at a material-to-liquid ratio of 1:8 (g / ml), and then centrifuged to obtain soybean residue and soybean milk after removing the residue.

[0034] 2. After the sludge-free soy milk is placed at 4℃ for 16 hours to settle, it is centrifuged at 10000×g at 4℃ for 20 minutes to separate the precipitate and the supernatant.

[0035] 3. Pass the cold sedimentation supernatant through a 150kDa ultrafiltration membrane at 0.4MPa and 35℃ to obtain a 150kDa retentate, and freeze-dry it to obtain soybean protein products.

[0036] Comparative Example 3 Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows: 4. Freeze-dry the cold precipitation and 150kDa retentate into powder, and compound them at a mass ratio of 1:0.15 to obtain soybean protein products.

[0037] Comparative Example 4 Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows: 4. Freeze-dry the cold precipitation and 150kDa retentate into powder, and then compound them at a mass ratio of 1:5 to obtain soybean protein products.

[0038] Test case The soybean protein products prepared in Examples 1-7 and Comparative Examples 1-4 were tested as follows: The protein content of compound soybean protein products was determined according to the Kjeldahl method in GB5009.5-2016 "Determination of Protein in Food"; the content of essential amino acids such as threonine, valine, isoleucine, leucine, phenylalanine, and lysine was determined according to GB 5009.124-2016; the methionine content was determined by acid oxidation hydrolysis; and the tryptophan content was determined by alkaline hydrolysis.

[0039] The amino acid ratio coefficient is calculated based on the amino acid balance theory and the essential amino acid model proposed by FAO / WHO. It is used to calculate the amino acid ratio (RAA) and amino acid ratio coefficient (RC) of EAA in the sample protein, and finally obtain the ratio coefficient score (SRC). The calculation formulas for the three are as shown in equations (1), (2) and (3):

[0040]

[0041]

[0042] In the formula: CV is the coefficient of variation of RC; CV = standard deviation / mean If the essential amino acid composition of food protein is consistent with the WHO / FAO model, then SRC = 100. As can be seen from Table 1, the SRC values ​​of soybean protein products prepared using Examples 1-7 are significantly higher than those of Comparative Examples 1-4, with the SRC values ​​of Examples 1-2 being closer to 100, indicating that they are more in line with the essential amino acid model proposed by FAO / WHO and have higher nutritional value.

[0043] According to the Langevin distance method, the proximity U(a, u) between object u and model protein a is defined. The proximity can reflect the degree of closeness between the protein of the evaluation object and the model protein. The calculation formula is as shown in equation (4):

[0044] In the formula: a k The content (mg / g) of the kth type of EAA in the standard protein pattern, 1≤k≤7; u ik Let be the content (mg / g) of the k-th type of EAA for the i-th evaluation object, where 1≤k≤7.

[0045] The closer the similarity is to 1, the closer the protein is to the model protein. As can be seen from Table 1, the U(a,u) values ​​of the soybean protein products prepared using Examples 1-7 are significantly higher than those of Comparative Examples 1-4. Among them, the U(a,u) values ​​of Examples 1-2 are closer to 1, indicating that they are closer to the model protein and have higher nutritional value.

[0046] Table 1. Measurement of soybean protein products

[0047] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing soybean protein products, characterized in that, include: Soybeans and water are ground and centrifuged to obtain soy milk and soybean residue after removing the residue. The de-residue soybean milk is subjected to cold sedimentation and centrifugation to obtain cold sedimentation precipitate and cold sedimentation supernatant. The supernatant from the cold sedimentation is subjected to ultrafiltration, and the retentate is collected. The cold precipitate and the retained product were dried separately to obtain the dried cold precipitate and the dried retained product. The cold-sinking dried material and the retained dried material are mixed and processed to obtain the soybean protein product; The mass ratio of the cold-sinking dried material to the retained dried material is 1:(0.2~3); The ultrafiltration membrane used in the ultrafiltration process has a pore size of 100~180 kDa; The temperature of the cold sink treatment is 2~6℃, and the time is 14~18 h.

2. The method according to claim 1, characterized in that, The mass-to-volume ratio of soybeans to water is 1:(5~10), with units of g / mL.

3. The method according to claim 1, characterized in that, The pressure of the ultrafiltration process is 0.2~0.6 MPa.

4. The method according to claim 1, characterized in that, The ultrafiltration process is performed at a temperature of 30~40℃.

5. A soybean protein product, characterized in that, The soybean protein product is obtained by the method for preparing soybean protein products according to any one of claims 1 to 4.

Images