Sulfur-containing amino acid soy protein product and method of making same

Abstract

The application relates to the food field and discloses a soybean protein product containing sulfur amino acids and a preparation method thereof, the method comprising the following steps: performing leaching and centrifugal treatment on soybean meal 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 cold precipitation and cold precipitation supernatant; simultaneously performing ultrasonic treatment and first ultrafiltration treatment on the cold precipitation supernatant, and collecting a permeate; performing second ultrafiltration treatment on the permeate, collecting a retentate, and obtaining the soybean protein product containing sulfur amino acids. The soybean protein product has high sulfur amino acid content, high nutritional value, good flavor and little protein soybean smell. Moreover, the preparation method is simple in operation and suitable for large-scale popularization and application.

Description

Technical Field

[0001] This application relates to the food industry. Specifically, this application relates to sulfur-containing amino acid soybean protein products and methods for preparing the same. Background Technology

[0002] Soybeans are not only an important oilseed crop, but also an ideal source of edible protein. Soy protein is rich in all eight essential amino acids required by the human body, with levels similar to those in meat, making it an ideal meat substitute and earning it the nickname "meat of the field."

[0003] In protein nutrition evaluation systems, soy protein, with its wide availability and low cost, has become an important representative of plant proteins. However, compared with high-quality animal proteins such as milk protein and egg protein, soy protein has significant nutritional shortcomings. Research data shows that every 100 grams of milk protein contains approximately 2.8-3.2 grams of sulfur-containing amino acids (methionine and cysteine), egg protein contains approximately 3.0-3.5 grams, while the same weight of soy protein contains only 1.8-2.2 grams. Sulfur-containing amino acids (such as methionine and cysteine) are the first limiting amino acids in soy protein, and their content and distribution directly determine the nutritional value of soy protein. Methionine is a sulfur-containing essential amino acid whose carbon-sulfur skeleton cannot be synthesized in the body. Methionine is an important methyl donor in the body and an important substance for the synthesis of choline and creatine. Choline is an important substance for preventing fatty liver and has an important protective effect against liver poisoning. Therefore, when the body's methionine supply is insufficient, it can affect growth and quality of life, and even cause diseases such as fatty liver.

[0004] The lack of sulfur-containing amino acids in soybean protein severely limits its application in high-end food products, such as infant formula, sports nutrition foods, and beverages, where protein quality requirements are extremely high. Soybean protein cannot meet the ideal nutritional ratio standards due to insufficient sulfur-containing amino acids.

[0005] Currently, the traditional process for extracting protein from soybeans is mainly alkaline extraction followed by acid precipitation. This process requires the use of large quantities of acid and alkali reagents, significantly increasing production costs and generating large amounts of acidic and alkaline wastewater, causing serious environmental pollution. Statistics show that producing 1 ton of soy protein isolate using the alkaline extraction and acid precipitation process generates approximately 15-20 tons of acidic and alkaline wastewater, which is costly and difficult to treat. Furthermore, the alkaline extraction and acid precipitation process is cumbersome, involving multiple acid and alkali adjustments and precipitation operations, resulting in a long production cycle. In addition, existing processes are not ideal for enriching sulfur-containing amino acids, failing to effectively address the insufficient sulfur-containing amino acid content in soy protein and thus failing to meet the market's urgent demand for soy protein products with high sulfur-containing amino acid content. Other methods, such as chromatography, have lower production efficiency, longer production cycles, expensive packing materials, require repeated elution, consume large amounts of water, and involve the concentration of elution water. These methods are unsuitable for large-scale industrial production.

[0006] Therefore, it is urgent to develop a high-efficiency, environmentally friendly, low-cost soybean protein extraction process that can significantly increase the content of sulfur-containing amino acids. This is of great practical significance for enhancing the added value of soybean protein products and promoting the high-quality development of the food industry. Summary of the Invention

[0007] This application aims to at least partially address the technical problems existing in the prior art. To this end, this application proposes a sulfur-containing amino acid soybean protein product and its preparation method. The soybean protein product of this application has a high sulfur amino acid content, high nutritional value, excellent flavor, and minimal beany odor. Furthermore, the preparation method is simple to operate and suitable for large-scale application.

[0008] In one aspect of this application, a method for preparing a sulfur-containing amino acid soybean protein product is provided. According to an embodiment of this application, the method includes: extracting and centrifuging soybean meal and water to obtain de-residue soybean milk and soybean residue; subjecting the de-residue soybean milk to cold sedimentation and centrifugation to obtain cold sedimentation precipitate and cold sedimentation supernatant; simultaneously subjecting the cold sedimentation supernatant to ultrasonic treatment and a first ultrafiltration treatment, collecting the permeate; subjecting the permeate to a second ultrafiltration treatment, collecting the retained product, and obtaining the sulfur-containing amino acid soybean protein product.

[0009] First, water is added to the soybean meal for extraction. The purpose of this step is to fully dissolve the protein in the soybean meal in the water to form a homogeneous mixed solution, which lays the foundation for subsequent separation and enrichment.

[0010] Next, a cold precipitation process is employed. The residue-free soy milk is placed under low-temperature conditions for sedimentation. Low temperature induces changes in protein structure, causing disulfide bonds to cross-link and increasing hydrophobicity, thus forming molecular polymer precipitates. 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 solution (i.e., the cold precipitation supernatant). This initially separates soy protein into two categories: "cold precipitation protein" and "cold precipitation supernatant protein," with differences in their amino acid compositions. The cold precipitation protein is also rich in sulfur-containing amino acids and has a low beany odor, making it a suitable component of sulfur-containing amino acid soy protein products.

[0011] Next, the supernatant from the cold sedimentation is subjected to ultrafiltration. Based on the retention and permeation characteristics of substances with different molecular weights on the ultrafiltration membrane, sulfur-containing amino acids in the solution are separated. Simultaneously, under the synergistic effect of ultrasound, the structure and particle size of sulfur-containing amino acid proteins undergo corresponding changes. During the first ultrafiltration treatment, under the synergistic effect of these two actions, sulfur-containing amino acids preferentially pass through the membrane, while proteins with high sulfur-containing amino acid content are retained, resulting in a significant enrichment of sulfur-containing amino acids in the permeate. A second ultrafiltration treatment is then performed to remove impurities, and the retained material, rich in sulfur-containing amino acids, is collected.

[0012] Soy protein with a high content of sulfur-containing amino acids has a strong beany odor that is difficult for the general public to accept. Therefore, the inventors of this application unexpectedly discovered that by simultaneously performing ultrasonic treatment during the first ultrafiltration process, due to the promoting effect of cavitation, certain small molecules that produce the beany odor are removed through filtration and volatilization under the combined action of the membrane, resulting in protein with minimal beany odor.

[0013] According to embodiments of this application, the method for preparing sulfur-containing amino acid soybean protein products described above may also have the following additional technical features:

[0014] According to embodiments of this application, the molecular weight cutoff of the first ultrafiltration treatment is 200 kDa to 400 kDa. In some embodiments, the molecular weight cutoff of the first ultrafiltration treatment is 200 kDa, 220 kDa, 250 kDa, 280 kDa, 300 kDa, 320 kDa, 350 kDa, 380 kDa, or 400 kDa. Therefore, sulfur-containing amino acid proteins can effectively pass through the ultrafiltration membrane with this molecular weight cutoff, achieving enrichment. Furthermore, small molecules that produce a beany odor are retained, thereby reducing the beany odor of the product and improving its flavor and taste.

[0015] According to embodiments of this application, the molecular weight cutoff of the second ultrafiltration treatment is 2 kDa to 8 kDa. In some embodiments, the molecular weight cutoff of the second ultrafiltration treatment is 2 kDa, 3 kDa, 4 kDa, 5 kDa, 6 kDa, 7 kDa, or 8 kDa. Therefore, sulfur-containing amino acid proteins can be effectively retained, thereby further increasing the sulfur-containing amino acid content in the product.

[0016] According to embodiments of this application, the ultrasonic treatment power is 400 W to 1500 W, and the temperature is 40℃ to 60℃. In some embodiments, the ultrasonic treatment power is 400 W, 500 W, 600 W, 800 W, 1000 W, 1200 W, 1400 W, or 1500 W, and the temperature is 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, or 60℃. Thus, certain small molecules that produce a beany odor are removed through filtration and volatilization under the combined action of the membrane, thereby further reducing the beany odor of the protein.

[0017] According to embodiments of this application, the mass ratio of soybean meal to water is 1:(5~15), the extraction temperature is 30℃~60℃, and the extraction time is 30 min~120 min. In some embodiments, the mass ratio of soybean meal to water is 1:5, 1:6, 1:8, 1:10, 1:12, or 1:15, the extraction temperature is 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, or 60℃, and the extraction time is 30 min, 40 min, 50 min, 60 min, 80 min, 100 min, or 120 min, respectively. This ensures efficient protein extraction, avoids excessive viscosity and insufficient extraction due to insufficient water, and prevents excessive water from causing excessively low protein concentration, which is detrimental to subsequent processing and increases unnecessary waste.

[0018] According to embodiments of this application, the soybean meal is selected from low-temperature defatted soybean meal or low-temperature pressed soybean meal.

[0019] According to an embodiment of this application, the method further includes: extracting the soybean residue, collecting the supernatant, and then subjecting it to the cold precipitation treatment. Thus, the extraction treatment can further extract protein from the soybean residue, thereby increasing the yield of sulfur-containing amino acids. In some embodiments, the extractant used in the extraction treatment includes water.

[0020] According to embodiments of this application, the cold settling treatment is performed at a temperature of 0°C to 10°C for a duration of 8 h to 20 h. In some embodiments, the cold settling treatment is performed at temperatures of 0°C, 2°C, 4°C, 5°C, 6°C, 8°C, and 10°C for durations of 8 h, 10 h, 12 h, 14 h, 15 h, 16 h, 18 h, and 20 h, 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. Specifically, the cold settling treatment includes placing the de-residue soybean milk under low-temperature conditions for settling.

[0021] According to embodiments of this application, the method further includes drying the retained material. This yields a solid product, facilitating storage and transportation and extending shelf life. In some embodiments, the drying process includes spray drying or freeze drying.

[0022] According to an embodiment of this application, the method further includes: dissolving the cold-precipitated precipitate in water and mixing it with the retained product to obtain the sulfur-containing amino acid soybean protein product. This facilitates the preparation of sulfur-containing amino acid soybean protein products by combining the cold-precipitated precipitate rich in sulfur-containing amino acids with the retained product.

[0023] According to an embodiment of this application, the method includes:

[0024] Step 1: Place defatted soybean meal into a container equipped with a stirring device, add water, heat, and stir and extract at a uniform speed;

[0025] Step 2: Centrifuge the extracted mixture and collect the supernatant;

[0026] Step 3: Allow the supernatant to settle at 4°C for 16 hours;

[0027] Step 4: Centrifuge the solution after cold precipitation to obtain the supernatant and precipitate; redissolve the precipitate in water and dry it to obtain the cold-precipitated protein component;

[0028] Step 5: Pass the cold supernatant through an ultrafiltration membrane with a molecular weight cutoff of 300 kDa, and sonicate the cold supernatant during the ultrafiltration process. The ultrasonic power is 500 W and the temperature is 50°C. Collect the permeate.

[0029] Step 6: Pass the permeate through an ultrafiltration membrane with a molecular weight cutoff of 5 kDa, collect the retained product, and dry it to obtain the sulfur-containing amino acid soybean protein product.

[0030] Therefore, the soybean protein products obtained using this method have high sulfur amino acid content, high nutritional value, excellent flavor, and minimal beany odor. Furthermore, the preparation method is simple to operate and suitable for large-scale application.

[0031] In another aspect of this application, a sulfur-containing amino acid soy protein product is proposed. According to an embodiment of this application, the sulfur-containing amino acid soy protein product is obtained by the method described above for preparing sulfur-containing amino acid soy protein products. Therefore, the sulfur-containing amino acid soy protein product of this application has a high sulfur amino acid content, high nutritional value, excellent flavor, and minimal beany taste.

[0032] According to an embodiment of this application, the sulfur-containing amino acid content in the soybean protein product is 2.77% to 3.68%. Therefore, the soybean protein product is rich in sulfur-containing amino acids.

[0033] 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

[0034] 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:

[0035] Figure 1 A flowchart of a method for preparing sulfur-containing amino acid soybean protein products according to an embodiment of this application is shown. Detailed Implementation

[0036] 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.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0038] 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.

[0039] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this application but do not exclude other contents.

[0040] This application discloses a method for preparing soybean protein products containing sulfur-containing amino acids. According to embodiments of this application, see [link to embodiment]. Figure 1 The method uses low-temperature defatted soybean meal or low-temperature pressed soybean meal as raw material, and extracts it by dissolving it in water without adding acid or alkali additives. The extracted mixture is centrifuged to remove residue, and the supernatant is retained. The centrifuged soybean residue is subjected to multiple water extractions to extract as much protein as possible. This residue, along with the supernatant, is then placed in a low-temperature precipitate and centrifuged to obtain the precipitate and supernatant. The precipitate can be used as the precipitated protein component, and its sulfur-containing amino acid content is significantly increased, making it usable.

[0041] The supernatant from the cold settling is subjected to a first and second ultrafiltration process using an organic polymer membrane. The two ultrafiltration processes use membranes with different molecular weight cutoffs, applied first with a high molecular weight cutoff membrane and then with a low molecular weight cutoff membrane, to achieve staged filtration. During the first ultrafiltration process, an ultrasonic device is used simultaneously for synergistic processing. The retentate from the second ultrafiltration process is collected, dried, and the resulting soy protein product is obtained. Alternatively, the dried retentate and the dried cold-set protein fraction can be used together as the target soy protein product.

[0042] 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.

[0043] Low-temperature defatted soybean meal: prepared according to GB / T 21494-2008, with a nitrogen solubility index ≥80%.

[0044] Example 1

[0045] In this embodiment, soy protein products are prepared according to the following method:

[0046] 1. Take 100 parts by weight of low-temperature defatted soybean meal, put it into a container with a stirring device, add 1250 parts by weight of water, heat the temperature to 55℃, and stir and extract at a uniform speed for 60 minutes.

[0047] 2. Centrifuge the extracted mixture at 5000×g for 20 minutes. Collect the supernatant and discard the precipitate. Transfer the supernatant to a low-temperature refrigerator and allow it to settle at 4°C for 16 hours.

[0048] 3. Transfer the cooled solution to a centrifuge and centrifuge at 5000×g for 20 min to obtain the precipitate and supernatant. Collect the precipitate, redissolve it in water, and obtain the cooled protein fraction 1. Retain the supernatant for the next step of membrane separation and fractionation.

[0049] 4. The supernatant is sequentially filtered through 300kDa and 5kDa ultrafiltration membranes for staged filtration. When passing through the 300kDa membrane, an ultrasonic probe needs to be placed in the feed-liquid balance tank to perform ultrasonic treatment on the material. The ultrasonic power is 500W and the temperature is 50℃. The permeate is collected and concentrated through a 5kDa ultrafiltration membrane, concentrated 3 times, washed once, and the concentrated liquid (retentate) is collected. It is a high-sulfur amino acid protein component 2.

[0050] Example 2

[0051] In this embodiment, soy protein products are prepared according to the following method:

[0052] 1. Take 100 parts by weight of low-temperature defatted soybean meal, put it into a container with a stirring device, add 500 parts by weight of water, heat the temperature to 60℃, and stir and extract at a uniform speed for 30 minutes.

[0053] 2. Centrifuge the extracted mixture at 5000×g for 20 minutes. Collect the supernatant and discard the precipitate. Transfer the supernatant to a low-temperature refrigerator and allow it to settle at 0℃ for 8 hours.

[0054] 3. Transfer the cooled solution to a centrifuge and centrifuge at 5000×g for 20 min to obtain the precipitate and supernatant. Collect the precipitate, redissolve it in water, and obtain the cooled protein fraction 1. Retain the supernatant for the next step of membrane separation and fractionation.

[0055] 4. Pass the supernatant sequentially through 200kDa and 2kDa ultrafiltration membranes for fractional filtration. When passing through the 200kDa membrane, place the ultrasonic probe in the feed-liquid balance tank to perform ultrasonic treatment on the material. The ultrasonic power is 400W and the temperature is 40℃. Collect the permeate and concentrate it through a 2kDa ultrafiltration membrane, concentrating it 3 times. Wash the filter once and collect the concentrate (retentate), which is protein component 2.

[0056] Example 3

[0057] In this embodiment, soy protein products are prepared according to the following method:

[0058] 1. Take 100 parts by weight of low-temperature defatted soybean meal, put it into a container with a stirring device, add 1500 parts by weight of water, heat the temperature to 60℃, and stir and extract at a uniform speed for 30 minutes.

[0059] 2. Centrifuge the extracted mixture at 5000×g for 20 minutes. Collect the supernatant and discard the precipitate. Transfer the supernatant to a low-temperature refrigerator and allow it to settle at 10℃ for 20 hours.

[0060] 3. Transfer the cooled solution to a centrifuge and centrifuge at 5000×g for 20 min to obtain the precipitate and supernatant. Collect the precipitate, redissolve it in water, and obtain the cooled protein fraction 1. Retain the supernatant for the next step of membrane separation and fractionation.

[0061] 4. The supernatant is sequentially filtered through 400kDa and 8kDa ultrafiltration membranes for fractional filtration. When passing through the 400kDa membrane, an ultrasonic probe needs to be placed in the feed-liquid balance tank to perform ultrasonic treatment on the material. The ultrasonic power is 1500W and the temperature is 60℃. The permeate is collected and concentrated through an 8kDa ultrafiltration membrane, concentrated 3 times, washed once, and the concentrate (retentate) is collected, which is protein component 2.

[0062] Example 4

[0063] Soy protein products were prepared according to the method of Example 1, except that in step 4, the 300kDa ultrafiltration membrane was replaced with a 100kDa ultrafiltration membrane.

[0064] Example 5

[0065] Soy protein products were prepared according to the method of Example 1, except that in step 4, the 300kDa ultrafiltration membrane was replaced with a 500kDa ultrafiltration membrane.

[0066] Example 6

[0067] Soy protein products were prepared according to the method of Example 1, except that in step 4, the 5kDa ultrafiltration membrane was replaced with a 1kDa ultrafiltration membrane.

[0068] Example 7

[0069] Soy protein products were prepared according to the method of Example 1, except that in step 4, the 5kDa ultrafiltration membrane was replaced with a 10kDa ultrafiltration membrane.

[0070] Comparative Example 1

[0071] In this comparative example, soybean protein products were prepared according to the following method (alkali dissolution and acid precipitation):

[0072] 1. Take 100 parts by weight of low-temperature defatted soybean meal, put it into a container with a stirring device, add 1250 parts by weight of water, heat the temperature to 55℃, adjust the pH to 7.50 with 2mol / L NaOH, and stir and extract at a uniform speed for 60 minutes.

[0073] 2. Centrifuge the extracted mixed solution at 5000×g for 20 minutes. After centrifugation, keep the supernatant and discard the precipitate.

[0074] 3. Adjust the pH of the supernatant collected after centrifugation to 4.50 with 2 mol / L HCl, stir well, and centrifuge at 5000×g for 20 min to obtain the precipitate and supernatant. Discard the supernatant and collect the precipitate.

[0075] 4. Dissolve the precipitate from the previous acid precipitation in water, adjust the pH to neutral, and obtain the alkali-extracted and acid-precipitated soybean protein product.

[0076] Comparative Example 2

[0077] Soy protein products were prepared according to the method of Example 1, except that ultrasonic treatment was not performed in step 4, as detailed below:

[0078] 4. Pass the supernatant sequentially through 300kDa and 5kDa ultrafiltration membranes for fractional filtration. Collect the 300kDa permeate and concentrate it through a 5kDa ultrafiltration membrane. Concentrate it 3 times, wash once, and collect the concentrate (retentate), which is protein component 2.

[0079] Comparative Example 3

[0080] Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows:

[0081] 4. Pass the supernatant through a 400kDa membrane. Place the ultrasonic probe in the feed-liquid balance tank to perform ultrasonic treatment on the material. The ultrasonic power is 1500W, and the temperature is 60℃. Collect the permeate, which is protein component 2.

[0082] Comparative Example 4

[0083] Soy protein products were prepared according to the method in Example 1, except that step 4 is as follows:

[0084] 4. Pass the supernatant through a 5kDa ultrafiltration membrane and collect the concentrate (retentate), which is protein fraction 2.

[0085] Test case

[0086] 1. The amino acid composition of the soybean protein products, soybean meal, and milk prepared in each example and comparative example was tested separately. The determination methods are as follows:

[0087] GB 5009.124-2016 "National Food Safety Standard - Determination of Amino Acids in Food" and GB / T 18246-2019 "Determination of Amino Acids in Feed".

[0088] 2. Sensory evaluation of the beany odor of protein components 1 and 2 prepared in Examples 1-7 and Comparative Examples 2-4, and the alkali-soluble and acid-precipitated proteins of Comparative Example 1, was conducted using the following methods:

[0089] The final score is the average of the ratings from 20 or more evaluators, and the grades are divided as follows:

[0090] Excellent (85-100 points): Very mild beany smell, no off-odors, and highly acceptable;

[0091] Good (70-84 points): Slight beany smell, no obvious off-odor, and relatively acceptable;

[0092] Pass (55-69 points): Moderate beany smell, no unpleasant odor, acceptable;

[0093] Unacceptable (≤54 points): Strong beany smell or unpleasant odor, low acceptance.

[0094] 3. Results Analysis

[0095] (1) Amino acid content

[0096] As shown in Table 1, the total amount of sulfur-containing amino acids (cystine (Cys) and methionine (Met)) in protein component 1 obtained in Example 1 was significantly higher than that in the isolated protein prepared by the conventional alkaline extraction and acid precipitation method in Comparative Example 1, with an increase of nearly 11.24%. The total amount of sulfur-containing amino acids in protein component 2 obtained in Example 1 was significantly increased, by 47.79% compared with the isolated protein in Comparative Example 1.

[0097] Table 1. Amino acid composition of soybean protein products and control products in Example 1, Comparative Example 1, and Comparative Example 2.

[0098]

[0099] As can be seen from Table 2, after using the combined process path of the present invention, through the classification of membrane materials and the change of protein conformation induced by ultrasound, the protein components with high sulfur amino acid content are enriched and retained and permeated by the corresponding membranes. The total amount of sulfur amino acids in the extracted protein component 2 is significantly increased compared with comparative examples 1-4.

[0100] Table 2. Amino acid composition of protein component 2 prepared in Examples 2-7 and Comparative Examples 2-4

[0101]

[0102] (2) Sensory evaluation

[0103] As shown in Table 3, for the sensory evaluation of protein component 1, the cold precipitation process of this application is significantly superior to the traditional process of Comparative Example 1, and the beany odor is significantly reduced. For protein component 2, after membrane filtration and the synergistic effect of ultrasound, while obtaining high sulfur-containing amino acids, certain oxides and volatile substances are largely removed, thus significantly improving the beany odor.

[0104] Table 3 Sensory scores (protein component 1)

[0105]

[0106] Table 4 Sensory Scores (Protein Component 2)

[0107]

[0108] 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 sulfur-containing amino acid soybean protein products, characterized in that, include: Soybean meal and water are extracted and centrifuged to obtain soybean milk and soybean residue after slag removal; The de-residue soybean milk is subjected to cold sedimentation and centrifugation to obtain cold sedimentation precipitate and cold sedimentation supernatant. The cold sediment supernatant is simultaneously subjected to ultrasonic treatment and a first ultrafiltration treatment, and the permeate is collected. The permeate is subjected to a second ultrafiltration treatment, and the retentate is collected to obtain the sulfur-containing amino acid soybean protein product. The molecular weight cutoff of the first ultrafiltration treatment is 200 kDa~400 kDa; The molecular weight cutoff for the second ultrafiltration treatment is 2 kDa to 5 kDa; The power of the ultrasonic treatment is 400 W to 1500 W.

2. The method according to claim 1, characterized in that, The temperature for ultrasonic treatment is 40℃~60℃.

3. The method according to claim 1, characterized in that, The mass ratio of soybean meal to water is 1:(5~15), and the extraction temperature is 30℃~60℃, and the time is 30 min~120 min; The method further includes: extracting the soybean residue, collecting the supernatant, and then performing the cold sedimentation treatment.

4. The method according to claim 1, characterized in that, The temperature of the cold sinking treatment is 0℃~10℃, and the time is 8 h~20 h.

5. The method according to claim 1, characterized in that, Further includes: The retained material is then dried.

6. The method according to claim 1 or 5, characterized in that, The method further includes: dissolving the cold precipitate in water and mixing it with the retained material to obtain the sulfur-containing amino acid soybean protein product.

7. The method according to claim 1, characterized in that, include: Step 1: Place defatted soybean meal into a container equipped with a stirring device, add water, heat, and stir and extract at a uniform speed; Step 2: Centrifuge the extracted mixture and collect the supernatant; Step 3: Allow the supernatant to settle at 4°C for 16 hours; Step 4: Centrifuge the solution after cold precipitation to obtain the supernatant and precipitate; redissolve the precipitate in water and dry it to obtain the cold-precipitated protein component; Step 5: Pass the cold supernatant through an ultrafiltration membrane with a molecular weight cutoff of 300 kDa, and sonicate the cold supernatant during the ultrafiltration process. The ultrasonic power is 500 W and the temperature is 50°C. Collect the permeate. Step 6: Pass the permeate through an ultrafiltration membrane with a molecular weight cutoff of 5 kDa, collect the retained product, and dry it to obtain the sulfur-containing amino acid soybean protein product.

8. The method according to claim 7, characterized in that, The cold-sinking protein component obtained in step 4 is mixed with the dried residue in step 6 to obtain the sulfur-containing amino acid soybean protein product.

9. A sulfur-containing amino acid soybean protein product, characterized in that, The sulfur-containing amino acid soybean protein product is obtained by the method for preparing sulfur-containing amino acid soybean protein products according to any one of claims 1 to 8.

10. The sulfur-containing amino acid soybean protein product according to claim 9, characterized in that, The sulfur-containing amino acid soybean protein product contains 2.77% to 3.68% sulfur-containing amino acids.

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