Soybean protein with high digestion speed and high digestion rate as well as preparation method and application of soybean protein

Abstract

The invention provides soybean protein with high digestion speed and high digestibility as well as a preparation method and application of the soybean protein, and belongs to the technical field of vegetable protein processing. The preparation method of the soybean protein with the high digestion speed and the high digestion rate comprises the three steps of raw material pretreatment, alkali dissolution and acid extraction, purification and drying. The soybean protein with high digestion speed and high digestibility obtained by the invention has the protein hydrolysis degree of 52% within 3 hours in a simulated gastrointestinal tract digestion system, and the digestibility can reach 88%, which is obviously higher than that of the traditional soybean protein (the digestibility is about 60%). Based on the excellent quick digestion performance, the low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-fat low-

Description

Technical Field

[0001] This invention belongs to the field of plant protein processing technology, and particularly relates to a soybean protein with high digestibility and high digestibility, its preparation method and application. Background Technology

[0002] Soy protein, as a high-quality plant protein, is rich in essential amino acids, and its abundant and inexpensive resources make it a promising candidate for use in the food industry. However, the molecular structure of natural soy protein is relatively complex, with a high content of 11S globulin and a relatively high proportion of α-helices in its secondary structure. This makes it prone to forming stable aggregates between protein molecules, resulting in slow digestion and low bioavailability in the human gastrointestinal tract, which limits its application in nutritional foods for specific populations (such as infants, the elderly, and athletes).

[0003] Existing technologies modify soybean protein through enzymatic hydrolysis, ultrasound, and high-pressure homogenization to improve its digestibility. However, these methods mostly focus only on optimizing the modification process and fail to clarify the core structural characteristics of rapidly digestible soybean protein, resulting in unstable digestibility of modified products and difficulty in achieving precise industrial production. Furthermore, the application scenarios for existing modified soybean protein are relatively limited, and its potential in specialized nutritional foods has not been fully explored.

[0004] Therefore, clarifying the structural characteristics of rapidly digestible plant-based soybean protein, developing a stable and efficient preparation method, and expanding its application scenarios have become urgent technical problems to be solved in this field. Summary of the Invention

[0005] To address the problems of slow digestibility, low bioavailability, unclear structural characteristics, and limited application scenarios of existing soybean protein, this invention proposes a soybean protein with high digestibility and high digestibility, as well as its preparation method and applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing soybean protein with high digestibility and high digestibility, comprising the following steps: (1) The soybean meal is washed, dehulled, dried, crushed, sieved and defatted to obtain defatted soybean flour; (2) Disperse the defatted soybean powder in water, adjust the system to alkaline, heat to extract, and collect the supernatant by centrifugation; (3) Adjust the pH of the supernatant to acidic, let it stand, centrifuge to collect the precipitate, redissolve the precipitate, dialyze it, and freeze dry it to obtain the soybean protein with high digestibility and high digestibility.

[0007] Further, in step (1), the defatting treatment is performed by defatting soybean flour with petroleum ether at a ratio of 1g:5mL (w / v); the defatting treatment is performed 3 times.

[0008] Further, in step (2), the pH of the system is adjusted to 8.5 and the mixture is heated to 50°C for 2 hours for extraction.

[0009] Further, in step (3), the pH of the supernatant is adjusted to 4.4.

[0010] The present invention also provides a soybean protein with high digestibility and high digestibility, which is prepared according to the above preparation method.

[0011] The structural features of the soybean protein of this invention, which possesses high digestibility and high digestibility, are as follows: (a) The ratio of 7S globulin to 11S globulin was 0.58; (b) In the secondary structure, the content of β-sheets is 40% and the content of α-helices is 16%; (c) Surface hydrophobicity is 4020; Its hydrolysis is concentrated in the acidic β-subunit of 7S globulin, and the hydrolysis target is the carboxyl-terminal peptide bond of arginine (Arg) and lysine (Lys). The average particle size of the prepared soybean protein was 235 nm. After digestion in a simulated gastrointestinal digestive system for 3 hours, the degree of protein hydrolysis of the soybean protein was 52%, the digestibility was 88%, and its first-order hydrolysis rate constant k was 0.240 h. -1 .

[0012] The present invention also provides an application of the above-mentioned soy protein with high digestibility and high digestibility in the preparation of infant formula; further, by mass fraction, the infant formula contains: 18% soy protein, 12% whey protein, 55% lactose, 2% complex vitamins, and 13% minerals.

[0013] The present invention also provides an application of the above-mentioned soybean protein with high digestibility and high digestibility in the preparation of nutritional supplements for the elderly; further, by mass fraction, the nutritional supplement for the elderly contains: 65% soybean protein, 15% dietary fiber, 10% unsaturated fatty acids, 5% calcium, 2% iron, and 2% zinc.

[0014] The present invention also provides an application of the above-mentioned soybean protein with high digestibility and high digestibility in the preparation of sports nutrition protein bars; further, by mass fraction, the sports nutrition protein bar contains: 28% soybean protein, 15% whey protein, 25% maltodextrin, 12% nut powder, and 10% isomaltooligosaccharide.

[0015] The present invention also provides an application of the above-mentioned soybean protein with high digestibility and high digestibility in the preparation of functional beverages; further, by mass fraction, the functional beverage comprises: 6% soybean protein, 5% glucose, 3% fructose, 0.3% sodium citrate, 0.2% potassium chloride, 0.1% B vitamins, 0.1% vitamin C, and the balance being water.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The present invention provides a method for preparing soybean protein with high digestibility and high digestibility, comprising the steps of raw material pretreatment, alkali dissolution and acid extraction, purification, and drying. The soybean protein obtained by the present invention exhibits a protein hydrolysis degree of 52% and a digestibility of up to 88% within 3 hours in a simulated gastrointestinal digestion system, significantly higher than that of traditional soybean protein (digestibility approximately 60%). Based on its excellent rapid digestibility, it can be widely used in infant formula, nutritional supplements for the elderly, sports nutrition foods, and functional beverages.

[0017] (2) The soybean protein of the present invention has a relatively high content of 7S globulin (7S / 11S ratio 0.58) with high digestion speed and high digestibility. Its structure is relatively loose and easy to be attacked by digestive enzymes. The proportion of β-sheet is 40% and the proportion of α-helix is ​​16%. This secondary structure distribution reduces the stability of protein molecules and facilitates the degradation of digestive enzymes. The surface hydrophobicity is high (4020), which not only ensures the solubility of protein molecules in the digestion system, but also facilitates the binding of digestive enzymes with protein molecules. The particle size is controlled at 235nm, which increases the contact area between protein molecules and digestive enzymes. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Fourier transform infrared spectra of the proteins in the examples and comparative examples; Figure 2 The protein secondary structure percentages of each protein in the examples and comparative examples are shown. Figure 3 The particle size distribution results of each protein in the examples and comparative examples are shown. Figure 4 The changes in the degree of protein hydrolysis after 3 hours of simulated in vitro digestion of each protein in the examples and comparative examples; Figure 5 The changes in protein digestibility after 3 hours of simulated in vitro digestion of each protein in the examples and comparative examples are shown. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides a method for preparing soybean protein with high digestibility and high digestibility, comprising the following steps: (1) The soybean meal is washed, dehulled, dried, crushed, sieved and defatted to obtain defatted soybean flour; (2) Disperse the defatted soybean powder in water, adjust the system to alkaline, heat to extract, and collect the supernatant by centrifugation; (3) Adjust the pH of the supernatant to acidic, let it stand, centrifuge to collect the precipitate, redissolve the precipitate, dialyze it, and freeze dry it to obtain the soybean protein with high digestibility and high digestibility.

[0025] The preparation method of this invention includes raw material pretreatment, alkali dissolution and acid extraction, purification and drying. The raw material pretreatment (washing, peeling, drying, crushing, sieving, and defatting) removes impurities, oils, and non-protein components from soybean meal to avoid interfering with subsequent protein extraction and structural stability. Alkali dissolution and acid extraction utilize the characteristic that soybean protein has significantly increased solubility in an alkaline environment (pH=8.5). Heating (50°C) promotes the full dissolution of protein molecules, and then adjusting the pH to the isoelectric point (4.4) causes the protein to precipitate specifically, achieving efficient separation of protein from soluble impurities. Purification and drying (reconstitution, dialysis, and freeze-drying) removes residual salts and small molecule impurities. At the same time, freeze-drying avoids protein denaturation and aggregation caused by high temperature, preserving the natural structural basis that is conducive to digestion. This invention achieves precise control of the structure of soybean protein through standardized processes, resulting in soybean protein with an optimal structural combination of "7S / 11S ratio 0.58, β-sheet 40%, α-helix 16%, surface hydrophobicity 4020, and particle size 235nm". In a simulated gastrointestinal digestion system, the degree of hydrolysis reaches 52% and the digestibility reaches 88% within 3 hours, which is significantly better than traditional soybean protein (digestibility of about 60%), solving the core problems of slow digestion and low bioavailability of natural soybean protein.

[0026] In step (1) of the preferred embodiment of the present invention, the defatting treatment is performed by defatting soybean flour with petroleum ether at a ratio of 1g:5mL (w / v); the defatting treatment is performed three times. The precise liquid-solid ratio can fully remove the oil from the soybean flour, avoid residual oil from coating protein molecules and hindering the binding of digestive enzymes to protein active sites, and at the same time create a pure system for subsequent alkali-soluble protein extraction, improve the protein extraction rate and purity, and lay the foundation for the high digestibility of the final product.

[0027] In step (2) of the preferred embodiment of the present invention, the pH of the system is adjusted to 8.5 and the system is heated to 50°C for 2 hours for extraction.

[0028] In step (3) of the preferred embodiment of the present invention, the pH of the supernatant is adjusted to 4.4.

[0029] This invention also provides a soybean protein with high digestibility and high digestibility, prepared according to the above-described preparation method. The structural characteristics of the soybean protein with high digestibility and high digestibility in this invention satisfy the following combination: (a) The ratio of 7S globulin to 11S globulin was 0.58; (b) In the secondary structure, the content of β-sheets is 40% and the content of α-helices is 16%; (c) Surface hydrophobicity is 4020; Its hydrolysis is concentrated in the acidic β-subunit of 7S globulin, and the hydrolysis target is the carboxyl-terminal peptide bond of arginine (Arg) and lysine (Lys). The average particle size of the prepared soybean protein was 235 nm. After digestion in a simulated gastrointestinal digestive system for 3 hours, the degree of protein hydrolysis of the soybean protein was 52%, the digestibility was 88%, and its first-order hydrolysis rate constant k was 0.240 h. -1 .

[0030] The present invention also provides an application of the above-mentioned soy protein with high digestibility and high digestibility in infant formula; further, by mass fraction, it comprises: 18% soy protein, 12% whey protein, 55% lactose, 2% complex vitamins, and 13% minerals.

[0031] This invention also provides an application of the above-mentioned soy protein with high digestibility and high digestibility in nutritional supplements for the elderly; further, by mass fraction, it comprises: 65% soy protein, 15% dietary fiber, 10% unsaturated fatty acids, 5% calcium, 2% iron, and 2% zinc.

[0032] The present invention also provides an application of the above-mentioned soy protein with high digestibility and high digestibility in sports nutrition protein bars; further, by mass fraction, it comprises: 28% soy protein, 15% whey protein, 25% maltodextrin, 12% nut powder, and 10% isomaltooligosaccharide.

[0033] This invention also provides an application of the above-mentioned soybean protein with high digestibility and high digestibility in functional beverages; further, by mass fraction, it comprises: 6% soybean protein, 5% glucose, 3% fructose, 0.3% sodium citrate, 0.2% potassium chloride, 0.1% B vitamins, 0.1% vitamin C, and the balance being water.

[0034] All raw materials used in the embodiments of this invention were purchased commercially.

[0035] The technical solution of the present invention will be further illustrated by the following embodiments.

[0036] Example 1 A method for preparing soybean protein with high digestibility and high digestibility includes the following steps: (1) The soybean meal was washed, dehulled and dried. The dried soybeans were ground and passed through a 60-mesh sieve to obtain whole soybean flour. The flour was then defatted three times with petroleum ether at a ratio of 1g:5mL (w / v). (2) Disperse the defatted soybean powder obtained in step (1) in distilled water at a ratio of 1g:20mL (w / v), then adjust the pH of the system to 8.5 with 1mol / L sodium hydroxide solution, extract the mixture at 50℃ for 2h, and then centrifuge to collect the supernatant. (3) Then the pH of the supernatant was adjusted to 4.4 with 1 mol / L dilute hydrochloric acid solution. After standing for 1 hour, the precipitate was collected by centrifugation, reconstituted, and the crude protein sample was dialyzed with deionized water (with a molecular weight cutoff of 3.5 kDa). The sample was then freeze-dried to obtain a soybean protein product (XDD-23-P) with high digestibility and high digestibility.

[0037] Comparative Example 1 (HK-60-P) Same as Example 1, except that in step (2), the pH of the system is adjusted to 8.5 with a 1 mol / L sodium hydroxide solution.

[0038] Comparative Example 2 (XZD-1-P) Same as Example 1, except that in step (2), the mixture is extracted at 40°C for 2 hours.

[0039] Comparative Example 3 (XZD-15-P) Same as Example 1, except that in step (2), the mixture is extracted at 50°C for 3 hours.

[0040] Performance test examples The structural characteristics of the rapidly digestible plant-based soy protein (XDD-23-P) prepared in Example 1 and the protein samples from Comparative Examples 1-3 were analyzed. The analysis methods and results are as follows: (1) Detection of 7S / 11S globulin ratio Protein subunit distribution was analyzed using 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Each protein sample was diluted to 5 mg / mL (w / v), mixed with SDS loading buffer (5×) at a ratio of 1:4 (v / v), heated in a 100°C water bath for 5 min, and cooled to room temperature in an ice bath before use. 10 μL of protein solution was loaded onto each gel lane, and molecular weight was estimated using standard markers (10–180 kDa). Electrophoresis was performed on a stacking gel at 80 V for 30 min, followed by separation gel electrophoresis at 120 V for 1 h. After electrophoresis, the gel was stained with Coomassie Brilliant Blue for 1 h and rinsed with distilled water until a clear background was obtained. Electrophoretic images were captured using a gel imaging system, and subunit composition was analyzed using ImageJ software (Table 1). The protein subunit composition and content test results of the rapidly digestible plant-based soy protein prepared in Example 1 are shown in Table 1.

[0041] Table 1. Results of protein subunit composition and content testing

[0042] The results in Table 1 show that the 7S / 11S globulin ratio of rapidly digestible plant-based soybean protein (XDD-23-P) is 0.58. This 7S / 11S ratio of XDD-23-P is significantly higher than the other three proteins (0.42–0.49). The looser structure and higher exposure of enzymatic hydrolytic sites of 7S globulin (β-conglycinin) compared to 11S globulin (soybean globulin) indicate a higher proportion of readily hydrolyzable components in the protein molecule, providing a core material basis for rapid digestion.

[0043] (2) Fourier transform infrared spectroscopy detection The lyophilized sample (2 mg) was mixed with KBr (198 mg) and compressed into tablets. Fourier transform infrared spectroscopy was used to analyze the sample at 400-4000 cm⁻¹. -1 The spectrum was scanned 32 times within the range.

[0044] The Fourier transform infrared spectra of the proteins in the examples and comparative examples are shown below. Figure 1 Located at 1650cm -1 The amide I bands on the left and right are particularly important because they reflect the secondary structure of the protein. The peak positions and intensities differ among the protein samples in the examples and comparative examples; for instance, XDD-23-P has a peak at 1657.2 cm⁻¹. -1 A strong peak is observed at this point, indicating a high β-sheet content, which is consistent with... Figure 2 The results were consistent. Conversely, HK-60-P was at 1654.8cm. -1 There is a peak at this point, indicating a low β-sheet content.

[0045] (3) Secondary structure inspection Circular dichroism (CD) chromatography was used for detection, with a scanning wavelength range of 190–250 nm and a protein concentration of 0.1 mg / mL. -1 The buffer solution is 0.01 mol·L⁻¹. -1 The phosphate buffer (pH=7.0) was used. The percentages of protein secondary structures (Random coil, β-turn, β-sheet, α-helix) for each protein in the examples and comparative examples are shown below. Figure 2 The results showed that the β-sheet content of rapidly digestible plant-based soy protein (XDD-23-P) was 40%, and the α-helix content was 16%.

[0046] (4) Surface hydrophobicity test The protein was detected using the 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescent probe method at concentrations ranging from 0.05 to 0.5 mg / mL.-1 The ANS concentration was 1 mmol·L⁻¹ -1 The excitation wavelength was 390 nm and the emission wavelength was 470 nm. The surface hydrophobicity test results of each protein in the examples and comparative examples are shown in Table 2.

[0047] Table 2 Surface hydrophobicity test results

[0048] Table 2 shows that the surface hydrophobicity of rapidly digestible plant-based soy protein (XDD-23-P) was significantly increased to 4020 compared to soy protein with a medium to low proportion (7S / 11S). XDD-23-P had a β-sheet content of 40% and a significantly higher surface hydrophobicity (4020.00±156.47) than other samples. The more flexible β-sheet structure makes it easier for proteases to recognize; while high surface hydrophobicity promotes hydrophobic interactions between proteases (pepsin and trypsin are both hydrophobic proteins) and substrate proteins, improving enzyme-substrate binding efficiency and accelerating enzymatic hydrolysis.

[0049] (5) Particle size detection Detection was performed using dynamic light scattering (DLS) at a protein concentration of 1 mg / mL. -1 The buffer solution is 0.01 mol·L⁻¹. -1 The phosphate buffer (pH=7.0) was used, and the detection temperature was 25℃; the particle size distribution results of each protein in the examples and comparative examples are shown in [reference needed]. Figure 3 , Figure 3 The results showed that the particle size distribution of rapidly digestible plant-based soybean protein (XDD-23-P) ranged from 220 to 250 nm, with an average particle size of 235 nm.

[0050] (6) Amino acid composition detection High-performance liquid chromatography (HPLC) was used for determination. Approximately 100 mg of sample was hydrolyzed in 10 mL of 6 M hydrochloric acid in a sealed tube at 110 °C under a nitrogen atmosphere for 24 h, then filtered and evaporated to dryness under vacuum at 50 °C. The residue was dissolved in 25 mL of 0.02 M hydrochloric acid and filtered through a 0.22 μm filter membrane before injection. Amino acid analysis was performed on an HPLC system (Agilent 1100, Agilent Technologies, USA) equipped with a C18 reversed-phase column (4.6 × 250 mm, 5 μm). The mobile phase consisted of solution A (0.1 M sodium acetate buffer, pH 6.5) and solution B (acetonitrile:methanol:water = 45:45:10, v / v / v). Detection was performed at 254 nm using a UV detector, and the results are expressed as mg of amino acids per 100 g of protein. The amino acid composition (mg / 100 g protein) of each protein in the examples and comparative examples is shown in Table 3.

[0051] Table 3. Amino acid composition (mg / 100 g protein) test results

[0052] Table 3 shows that, compared to soybean protein with a medium to low amino acid ratio (7S / 11S), the content of aspartic acid (Asp), alanine (Ala), and histidine (His) in rapidly digestible plant-based soybean protein (XDD-23-P) was significantly reduced, while the content of valine (Val) and leucine (Leu) was significantly increased. The significantly increased valine and leucine content in XDD-23-P indicates that the side chain structures of these two branched amino acids are more easily recognized by trypsin hydrolysis sites. Simultaneously, its uniform and moderate particle size distribution of 220–250 nm facilitates better contact with proteases compared to large aggregates, avoiding incomplete enzymatic hydrolysis caused by excessively large particles.

[0053] The digestibility of the rapidly digestible plant-based soy protein (XDD-23-P) prepared in Example 1 and the protein samples of Comparative Examples 1-3 was tested using a simulated gastrointestinal digestion system. The specific steps are as follows: (1) Simulated gastric digestion: 1g of raw protein was mixed with 20mL of distilled water to prepare a 5% solution by mass, boiled for 2min, cooled, and the pH was adjusted to 2.0 with 1mol / L HCl. 0.04g of pepsin (4% of the substrate mass) was added and reacted at 37℃ for 1h. (2) Simulated intestinal digestion: The pH of the solution was adjusted to 5.3 with 0.9 mol / L NaHCO3, and then the pH was adjusted to 7.0 with 1 mol / L NaOH. 0.04 g of trypsin (4% of the substrate mass) was added, and the reaction was carried out at 37℃ for 2 h. The reaction was terminated by boiling water bath for 10 min. Samples were taken at 0, 30, 60, 90, 120, and 180 min during the digestion process for the determination of degree of hydrolysis and digestibility. (3) Calculation of degree of hydrolysis and digestibility: Degree of hydrolysis: The ortho-phthalaldehyde (OPA) method was used. 3.00 mL of OPA solution was added to a 5 mL test tube, followed by 400 μL of hydrolysate diluted to a specific concentration. The reaction was allowed to proceed at room temperature for 2 min, and the absorbance was measured at 340 nm. A serine standard solution (0.9516 mmol / L) was used as a reference, and a blank test was performed with water. The calculation formula is as follows: Serine NH2 (L / g protein) = (OD sample - OD blank) / (OD standard - OD blank) × 0.9516 × (N × V) / (X × P) DH (%) = [(Serine NH2-0.342) / 0.970] / 7.8×100 Wherein, Serine NH2—mass of Serine NH2 per gram of protein; X—sample mass, g; P—protein content in the sample, %; N—dilution factor; V—volume of supernatant, L; 0.9516, 0.342, 0.970—constants; 7.8—amount of peptide bonds per gram of protein, mmol / g.

[0054] Protein digestibility: Protein content was determined using a semi-automatic Kjeldahl nitrogen analyzer. The in-vitro digestibility rate (DR) was then calculated using the following formula.

[0055] DR(%) = (P1-P2) / P1×100 P1 and P2 represent the protein content before and after in vitro digestion, respectively.

[0056] Under these conditions, the average degree of hydrolysis of existing soybean protein after 3 hours of digestion is 39.8%, and the average digestibility is 60.5%. The corresponding hydrolysis kinetic equation is DHt = 55 × (1 - e -0.167t The correlation equation between digestibility and degree of hydrolysis is D = 1.520 × DH. t +0.09, its first-order reaction rate constant k = 0.167 h -1 The time t for the degree of hydrolysis to reach 50% (maximum degree of hydrolysis) 1 / 2 =ln2 / k≈4.15 h.

[0057] Figure 4 The changes in the degree of protein hydrolysis after 3 hours of simulated in vitro digestion for the examples and comparative examples are shown. Figure 5 The changes in protein digestibility after 3 hours of simulated in vitro digestion of each protein in the examples and comparative examples are shown. Figure 4 and Figure 5 The results showed that the selected fast-digestible plant-based soybean protein (XDD-23-P) had a protein hydrolysis degree of 52% and a digestibility of 88% within 3 hours, with the corresponding hydrolysis kinetic equation being DH. t =65×(1-e -0.240t The correlation equation between digestibility and degree of hydrolysis is D = 1.686 × DH. t +0.24, its first-order reaction rate constant k = 0.240h. -1 The time t for the degree of hydrolysis to reach 50% (maximum degree of hydrolysis) 1 / 2 =ln2 / k≈2.9h. XDD-23-P achieved a degree of hydrolysis of 52% and a digestibility of 88% after 3 hours of in vitro digestion. This is not only far higher than the three comparative proteins HK-60-P, XZD-1-P, and XZD-15-P, but also significantly better than the average of existing soybean proteins (degree of hydrolysis 39.8%, digestibility 60.5%), directly demonstrating its superior digestibility.

[0058] The larger the value of k, the faster the enzymatic hydrolysis rate of soybean protein. The reaction rate constant k (0.240 h⁻¹) for a high digestibility system... -1 ) is a conventional system (0.167h) -1 The ratio of 1.44 times that of the selected fast-digestible plant-based soybean protein (XDD-23-P) indicates that the protease-substrate binding efficiency is higher and the enzymatic hydrolysis sites are more fully exposed; the time to reach the maximum degree of hydrolysis of 50% (t) is also higher. 1 / 2 =ln2 / k), the high-efficiency digestion system took 2.9 h, and the conventional system took 4.15 h, further demonstrating that the larger the k value, the more obvious the "rate advantage" of the digestion process. This indicates that the enzymatic hydrolysis reaction of XDD-23-P starts faster and proceeds more efficiently, and the advantage of digestion rate is fully verified at the kinetic level. The high 7S / 11S ratio, high β-sheet ratio, and strong surface hydrophobicity of XDD-23-P are not isolated but work synergistically to achieve full exposure of the enzymatic hydrolysis sites and efficient binding of the protease to the substrate, ultimately exhibiting a performance advantage far exceeding that of the other three proteins in hydrolysis kinetics and digestibility. This strong correlation between structure and function further confirms the stability and superiority of the rapid digestibility of XDD-23-P.

[0059] Application Example 1 Application of soy protein, which has high digestibility and digestibility, in infant formula: The soy protein prepared in Example 1 was compounded with whey protein, lactose, multivitamins, and minerals. The formula composition (by mass fraction) was: 18% soy protein, 12% whey protein, 55% lactose, 2% multivitamins, and 13% minerals. After the components were mixed evenly, they were spray-dried to produce infant formula powder. This formula powder has good solubility after being brewed. In a simulated infant gastrointestinal digestive system, the protein digestibility can reach 86% within 2 hours, which can meet the nutritional needs of infants for rapid digestion and absorption.

[0060] Application Example 2 Application of soy protein, which has high digestibility and digestibility, in nutritional supplements for the elderly: The soy protein prepared in Example 1 was compounded with dietary fiber, unsaturated fatty acids, calcium, iron, zinc, etc., and the formula composition (by mass fraction) was: 65% soy protein, 15% dietary fiber, 10% unsaturated fatty acids, 5% calcium, 2% iron, 2% zinc, and 1% other components. After mixing all components evenly, a powdered nutritional supplement for the elderly was prepared. This supplement can be taken directly with warm water, is easily digested and absorbed by the elderly, and effectively supplements the protein and minerals needed by them.

[0061] Application Example 3 Application of soy protein, which has high digestibility and digestibility, in sports protein bars: The soy protein prepared in Example 1 was compounded with whey protein, maltodextrin, nut powder, and isomaltooligosaccharide. The formula composition (by mass fraction) was: 28% soy protein, 15% whey protein, 25% maltodextrin, 12% nut powder, 10% isomaltooligosaccharide, 6% vegetable oil, 1% salt, and 3% food additives. Preparation steps: The fast-digestible soy protein, whey protein, and maltodextrin were sieved through an 80-mesh sieve and mixed evenly with the nut powder; the isomaltooligosaccharide, vegetable oil, and salt were heated and dissolved to make a syrup; the dry powder mixture was thoroughly stirred and mixed with the syrup until a uniform dough was formed, pressed into a mold, cut into 20g / bar protein bars, and sealed in packaging. These protein bars have a delicate texture and do not stick to teeth. Testing showed that in a simulated post-exercise gastrointestinal digestive system, the protein digestibility reached 87% within 2 hours, quickly replenishing protein for athletes and relieving muscle fatigue.

[0062] Application Example 4 Applications of soy protein, which has high digestibility and digestibility, in functional beverages: The soybean protein prepared in Example 1 was compounded with glucose, fructose, sodium citrate, potassium chloride, B vitamins, vitamin C (0.1%), and deionized water. The formulation (by mass fraction) was: soybean protein 6%, glucose 5%, fructose 3%, sodium citrate 0.3%, potassium chloride 0.2%, B vitamins 0.1%, vitamin C 0.1%, and deionized water 85.3%. Preparation steps: The rapidly digestible soybean protein was added to a portion of the deionized water and homogenized twice under 25 MPa pressure to obtain a stable protein dispersion. Glucose, fructose, sodium citrate, potassium chloride, and vitamins were dissolved in the remaining deionized water. The two solutions were mixed thoroughly, the pH was adjusted to 6.5-7.0, sterilized at 121℃ for 15 minutes, cooled, and then bottled to obtain a functional beverage. This beverage is clear and transparent, without sediment, and can be rapidly absorbed by the body after consumption, quickly replenishing energy and protein during or after exercise.

[0063] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing soybean protein with high digestibility and high digestibility, characterized in that, Includes the following steps: (1) The soybean meal is washed, dehulled, dried, crushed, sieved and defatted to obtain defatted soybean flour; (2) Disperse the defatted soybean powder in water, adjust the system to alkaline, heat to extract, and collect the supernatant by centrifugation; (3) Adjust the pH of the supernatant to acidic, let it stand, centrifuge to collect the precipitate, redissolve the precipitate, dialyze it, and freeze dry it to obtain the soybean protein with high digestibility and high digestibility.

2. The method for preparing soybean protein with high digestibility and high digestibility according to claim 1, characterized in that, In step (1), the defatting process is to defatt the soybean flour with petroleum ether at a ratio of 1g:5mL.

3. The method for preparing soybean protein with high digestibility and high digestibility according to claim 2, characterized in that, The degreasing treatment was performed three times.

4. The method for preparing soybean protein with high digestibility and high digestibility according to claim 1, characterized in that, In step (2), the pH of the system is adjusted to 8.5 and the mixture is heated to 50°C for 2 hours for extraction.

5. The method for preparing soybean protein with high digestibility and high digestibility according to claim 1, characterized in that, In step (3), the pH of the supernatant is adjusted to 4.

4.

6. A soybean protein with high digestibility and high digestibility, characterized in that, Prepared according to any one of claims 1-5.

7. The use of the soybean protein with high digestibility and high digestibility as described in claim 6 in the preparation of infant formula.

8. The use of the soybean protein with high digestibility and high digestibility as described in claim 6 in the preparation of nutritional supplements for the elderly.

9. The application of the soybean protein with high digestibility and high digestibility as described in claim 6 in the preparation of sports nutrition protein bars.

10. The use of the soybean protein with high digestibility and high digestibility as described in claim 6 in the preparation of functional beverages.

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