Soy protein amyloid fibril and fiber-iron complex, and preparation method and application thereof

Abstract

The application provides a soybean protein amyloid fiber and fiber-iron complex, a preparation method and application, and belongs to the technical field of protein fibers. The preparation method of the soybean protein amyloid fiber provided by the application comprises the following steps: providing soybean 7S globulin amyloid fiber, wherein the soybean 7S globulin amyloid fiber is prepared from soybean 7S globulin through an acid-heat method; mixing the soybean 7S globulin amyloid fiber as seeds, soybean protein isolate and water, and performing fiberization treatment to obtain the soybean protein amyloid fiber. The soybean protein amyloid fiber is prepared by taking the soybean 7S globulin amyloid fiber as seeds and taking the soybean protein isolate as a main material, and the cost is low; the fiber-iron complex prepared by using the soybean protein amyloid fiber as a carrier has a high iron loading rate, good gastric digestion resistance and excellent iron ion valence protection ability.

Description

Technical Field

[0001] This invention relates to the field of protein fiber technology, and in particular to a soybean protein starch-like fiber and fiber-iron complex, its preparation method, and its application. Background Technology

[0002] Traditional iron supplements such as ferrous sulfate and ferrous fumarate have problems with gastrointestinal irritation and instability. Third-generation iron supplements are new iron supplement products developed in recent years. They often use complex delivery with biological macromolecules such as proteins and polysaccharides. However, they still have problems such as some stomach discomfort and poor absorption of trivalent iron. The main reasons are that the carrier has a weak iron loading capacity, insufficient gastric resistance to digestion and iron reduction capacity.

[0003] Plant proteins, such as soy protein, are often used as important components of functional foods. However, they are mainly composed of globulins, which are easily degraded by proteases in the stomach. Acid-heat treatment can induce protein self-assembly into amyloid fibrils, effectively altering the original protein structure and significantly enhancing its resistance to gastric digestion. Simultaneously, soy protein is rich in reducing amino acids such as cysteine, tyrosine, and tryptophan, which help maintain iron in its divalent state, thus facilitating absorption and giving it the potential to serve as an iron delivery carrier.

[0004] Soy protein is mainly composed of 7S globulin and 11S globulin. The two have significant differences in fibrosis ability and digestibility. 7S globulin has a strong fibrosis ability and easily forms highly coiled and tangled fibers. It also has good gastric resistance to digestion and intestinal dissociation ability. However, its extraction process is cumbersome and complicated. Directly using 7S globulin as the main raw material to prepare soybean protein starch-like fiber is costly and difficult to achieve large-scale production. Summary of the Invention

[0005] The purpose of this invention is to provide a soybean protein amyloid fiber and a fiber-iron complex, as well as their preparation method and application. This invention uses soybean 7S globulin amyloid fiber as a seed and soybean protein isolate as the main material to prepare soybean protein amyloid fiber, which has a low cost. The fiber-iron complex prepared using this soybean protein amyloid fiber as a carrier has a high iron loading rate, good gastric resistance to digestion, and excellent iron ion valence state protection ability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing soybean protein amyloid fibers, comprising the following steps: Soybean 7S globulin amyloid fiber is provided, wherein the soybean 7S globulin amyloid fiber is prepared from soybean 7S globulin by an acid-heat method; The soybean 7S globulin amyloid fiber was used as a seed and mixed with soybean protein isolate and water. The resulting mixture was subjected to fiberization treatment to obtain the soybean protein amyloid fiber.

[0007] Preferably, the mass of the seeds is 1-30% of the soybean protein isolate content; the total concentration of soybean protein isolate and seeds in the mixture is 10-50 mg / mL.

[0008] Preferably, the fiberization treatment is carried out at a temperature of 70-90°C for 4-24 hours.

[0009] Preferably, the method for preparing the soybean 7S globulin amyloid fiber includes the following steps: Soybean 7S globulin was dissolved in water to obtain a soybean 7S globulin solution. The pH value was adjusted to 1.5-3.0, and hydration treatment and fiber growth treatment were performed sequentially to obtain the soybean 7S globulin amyloid fiber.

[0010] Preferably, the concentration of the soybean 7S globulin solution is 10~25 mg / mL; the hydration treatment temperature is 2~6℃ and the time is 8~24 h; the fiber growth treatment temperature is 70~90℃ and the time is 4~24 h.

[0011] The present invention provides soybean protein starch-like fiber prepared by the preparation method described in the above technical solution.

[0012] This invention provides the application of the soybean protein starch-like fiber described in the above technical solution in the preparation of iron delivery carriers.

[0013] This invention provides a method for preparing a fiber-iron composite, comprising the following steps: The soybean protein starch-like fiber, ferrous salt, antioxidant and water described in the above technical solution are mixed and compounded to obtain the fiber-iron complex.

[0014] The present invention provides a fiber-iron composite prepared by the preparation method described in the above technical solution.

[0015] This invention provides the application of the fiber-iron complex described above in the preparation of iron supplements.

[0016] Beneficial Effects: The seeding method, by introducing pre-formed fiber fragments as templates, not only accelerates fiber formation by skipping the nucleation stage but also allows newly generated fibers to inherit the functional characteristics of the seed itself. Current methods for preparing soybean protein amyloid fiber (SPF) often directly utilize conventional acid-heat methods or only use homologous soybean protein isolate (SPI) seeds for seeding. In contrast, this invention uses a seeding method to modify SPF, specifically using soybean 7S globulin amyloid fiber (7SF) as the seed (denoted as 7S seed). This seed is added to the reaction system at the beginning of SPI fiberization treatment, accelerating SPF growth and guiding its microstructure towards a high-density network fiber structure, ultimately effectively enhancing the gastric resistance to digestion. Furthermore, its application in the construction of composite iron-loaded formulations (i.e., fiber-iron complexes) shows that SPF enhanced with 7S seeds exhibits a higher iron loading rate and better iron ion valence state protection, effectively achieving stable and sustained release of iron ions in the stomach and efficient release in the intestines, achieving efficient iron ion delivery while maintaining low cost. Attached Figure Description

[0017] Figure 1 The changes in Th T fluorescence intensity at 6 h and 1 h during the fibrillation process of SPF for SPI and 7S seeds; Figure 2 TEM images of SPF enhanced for SPI and 7S seeds; Figure 3 Morphology distribution of SPF for SPI and 7S seed enhancement; Figure 4 Statistical chart of the number of SPF formations and the proportion of long fibers (>100nm) enhanced for SPI and 7S seeds; Figure 5 Figure 1. Results of Th T fluorescence loss rate test in SGF and SIF for SPF enhanced for SPI and 7S seeds; Figure 6 Statistical chart of free amino acid release during simulated digestion of SPF fortified with SPI and 7S seeds; Figure 7 The graph shows the iron loading rate test results for different fiber-iron composites. Figure 8 Energy dispersive spectroscopy (EDS) spectra of different fiber-iron composites; Figure 9 The graph shows the results of homogenization iron content tests for different fiber-iron composites. Figure 10 Fourier transform infrared spectra of different fiber systems before and after iron loading; Figure 11 Free Fe in different fiber-iron complexes during simulated digestion2+ Content test results graph; Figure 12 Fe in different fiber-iron complexes during simulated digestion 2+ Release rate test results graph; Figure 13 To simulate the effects of different fiber-iron complexes on Fe during digestion 2+ The graph shows the test results for the proportion of total free iron. Detailed Implementation

[0018] This invention provides a method for preparing soybean protein amyloid fibers, comprising the following steps: Soybean 7S globulin amyloid fiber is provided, wherein the soybean 7S globulin amyloid fiber is prepared from soybean 7S globulin by an acid-heat method; The soybean 7S globulin amyloid fiber was used as a seed and mixed with soybean protein isolate and water. The resulting mixture was subjected to fiberization treatment to obtain the soybean protein amyloid fiber.

[0019] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0020] This invention provides soybean 7S globulin amyloid fibers, which are prepared from soybean 7S globulin via an acid-thermal method. As one embodiment of this invention, the preparation method of the soybean 7S globulin amyloid fibers includes the following steps: dissolving soybean 7S globulin in water to obtain a soybean 7S globulin solution; adjusting the pH to 1.5-3.0; and sequentially performing hydration treatment and fiber growth treatment to obtain the soybean 7S globulin amyloid fibers. This invention does not specifically limit the source of the soybean 7S globulin and it can be prepared using methods well known to those skilled in the art. The preparation method of the soybean 7S globulin in this invention will be described in detail later. As one embodiment of this invention, the concentration of the soybean 7S globulin solution is 10-25 mg / mL, specifically 12 mg / mL, 15 mg / mL, 18 mg / mL, 20 mg / mL, or 22 mg / mL; in the example, it is 20 mg / mL. Preferably, soybean 7S globulin is mixed with water and stirred until fully dissolved to obtain a soybean 7S globulin solution; the stirring time can be 1.5-2 hours. In one embodiment of the present invention, the reagent used to adjust the pH value can be hydrochloric acid, and the concentration of the hydrochloric acid can be 0.5~3 mol / L, more specifically 2.5~3 mol / L, and the pH value can specifically be 1.8, 2.0, 2.2 or 2.5. In another embodiment of the present invention, the hydration treatment temperature is 2~6℃, specifically 3℃, 4℃ or 5℃; the time is 8~24h, specifically 10h, 12h, 15h, 18h or 20h; preferably, the hydration treatment further includes solid-liquid separation, collecting the supernatant for the fiber growth treatment; the solid-liquid separation method can be centrifugation, the centrifugation speed can be 9000 rpm, and the time can be 30min; the present invention removes insoluble matter in the system through solid-liquid separation. The protein concentration in the supernatant can be adjusted to a suitable concentration as needed, such as 12 mg / mL in the example, before proceeding with the fiber growth treatment. In one embodiment of the present invention, the temperature of the fiber growth treatment is 70~90℃, specifically 75℃, 80℃, or 85℃; the time is 4~24h, specifically 5h, 6h, 8h, 10h, 15h, or 20h; the fiber growth treatment is carried out under stirring conditions, and the stirring speed is 200~250rpm. In another embodiment of the present invention, no post-treatment is required after the fiber growth treatment; the soybean 7S globulin amyloid fiber dispersion obtained after the fiber growth treatment can be directly used for subsequent processing; alternatively, the soybean 7S globulin amyloid fiber dispersion obtained after the fiber growth treatment can be freeze-dried to obtain soybean 7S globulin amyloid fiber (freeze-dried powder).

[0021] After obtaining soybean 7S globulin amyloid fibers, this invention uses the soybean 7S globulin amyloid fibers as seeds, mixes them with soy protein isolate and water, and then performs a fibrosis treatment on the resulting mixture to obtain the soy protein amyloid fibers. This invention does not have a specific limitation on the source of the soy protein isolate; it can be prepared using methods well-known to those skilled in the art. The preparation method of the soy protein isolate in this invention will be described in detail later. As one embodiment of this invention, the mass of the seeds is 1-30% of the soy protein isolate mass, specifically 3%, 5%, 10%, 15%, 20%, 25%, or 30%; the total concentration of soy protein isolate and seeds in the mixture is 10-50 mg / mL, specifically 12 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, or 40 mg / mL. Preferably, this invention mixes the soybean 7S globulin amyloid fiber dispersion with the soy protein isolate solution, and then performs a fibrosis treatment on the resulting mixture. In one embodiment of the present invention, the concentration of the soybean 7S globulin amyloid fiber dispersion can be 10-50 mg / mL, specifically 12 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, or 40 mg / mL; the pH value can be 1.5-3.0, specifically 1.8, 2.0, 2.2, or 2.5. In another embodiment of the present invention, the concentration of the soybean protein isolate solution can be 10-50 mg / mL, specifically 12 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, or 40 mg / mL; the pH value can be 1.5-3.0, specifically 1.8, 2.0, 2.2, or 2.5. The volume ratio of the soybean 7S globulin amyloid fiber dispersion to the soybean protein isolate solution is based on ensuring that the seed mass is 1-30% of the soybean protein isolate content. In one embodiment of the present invention, the temperature of the fiberization treatment is 70~90℃, specifically 75℃, 80℃, or 85℃; the time is 4~24h, specifically 5h, 6h, 8h, 10h, 15h, or 20h; the fiberization treatment is carried out under stirring conditions, and the stirring speed is 200~250rpm. In another embodiment of the present invention, no post-treatment is required after the fiberization treatment; the soybean protein starch-like fiber dispersion obtained after the fiberization treatment can be directly used for subsequent processing; alternatively, the soybean protein starch-like fiber dispersion obtained after the fiberization treatment can be freeze-dried to obtain soybean protein starch-like fiber (freeze-dried powder).

[0022] This invention provides soybean amyloid fibers prepared by the method described in the above-mentioned technical solution. This invention uses a sowing method with soybean 7S globulin amyloid fibers as seeds to prepare soybean amyloid fibers, which can alter the growth kinetics and microstructure of soybean amyloid fibers, and also change their digestive behavior. Specifically, using soybean 7S globulin amyloid fibers as seeds can accelerate the fiberization process of soybean amyloid fibers, while also reducing the formation of long, straight fibers, forming high-density network fibers, resulting in lower protein hydrolysis during gastric digestion and higher protein hydrolysis during intestinal digestion.

[0023] This invention provides the application of the soybean protein starch-like fiber described in the above technical solution in the preparation of iron delivery carriers.

[0024] This invention provides a method for preparing a fiber-iron composite, comprising the following steps: The soybean protein starch-like fiber, ferrous salt, antioxidant and water described in the above technical solution are mixed and compounded to obtain the fiber-iron complex.

[0025] In one embodiment of the present invention, the mixing of soybean protein amyloid fiber, ferrous salt, antioxidant, and water specifically involves: mixing a soybean protein amyloid fiber dispersion with a ferrous salt solution containing an antioxidant, then adjusting the pH of the resulting mixture to 4.0-7.0 (specifically, 5.5, 6.0, or 6.5), and performing a compounding treatment; the concentration of the soybean protein amyloid fiber dispersion can be 10-50 mg / mL, specifically 12 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, or 40 mg / mL; the concentration of the ferrous salt containing the antioxidant... The concentration of ferrous salt in the ferrous salt solution can be 0.1~1.0 mol / L, specifically 0.3 mol / L or 0.5 mol / L; the mass ratio of soybean protein starch-like fiber to ferrous salt can be 3:0.5~1.5, specifically 3:0.8, 3:1 or 3:1.2, and the ferrous salt can be ferrous sulfate, specifically FeSO4·7H2O in the example; the mass ratio of antioxidant to iron in the ferrous salt can be 2:0.5~1.5, specifically 2:0.8, 2:1 or 2:1.2, and the antioxidant can specifically be ascorbic acid. As one embodiment of the invention, the reagent used to adjust the pH of the mixture solution can be an aqueous solution of NaOH, and the concentration of the NaOH aqueous solution can be 0.5~3.0 mol / L, specifically 2.5~3.0 mol / L.

[0026] In one embodiment of the present invention, the temperature of the composite treatment can be 15~30℃, specifically 20℃ or 25℃, and in this embodiment, the composite treatment is carried out at room temperature (25℃); the time of the composite treatment can be 30~50min, specifically 35min, 40min or 45min; the composite treatment can be carried out under stirring conditions, and the stirring speed can be 200~400rpm, further 200~300rpm. In one embodiment of the present invention, no post-treatment is required after the composite treatment, and the fiber-iron composite liquid obtained after the composite treatment can be directly used for subsequent applications; alternatively, the fiber-iron composite liquid obtained after the composite treatment can be freeze-dried to obtain fiber-iron composite (freeze-dried powder).

[0027] This invention provides a fiber-iron complex prepared by the method described in the above technical solution. The fiber-iron complex prepared using soybean protein starch-like fiber provided by this invention as a carrier exhibits high iron loading, good gastric resistance to digestion, and excellent iron ion valence state protection. Specifically, the soybean protein starch-like fiber provided by this invention can achieve the protection of Fe... 2+ High-efficiency load and can effectively delay Fe 2+ Premature release in the stomach can accelerate its release in the intestines and delay Fe 2+ Oxidation.

[0028] This invention provides the application of the fiber-iron complex described above in the preparation of iron supplements.

[0029] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Preparation Example 1 Soy protein isolate (SPI), soybean 7S globulin, and soybean 11S globulin were extracted, as detailed below: Defatted soybean meal (source: Shandong Yuwang Ecological Food Co., Ltd.) was pulverized using a grinder and passed through a 60-mesh sieve. The sieve residue was collected and dispersed in a 0.03M Tris-HCl buffer solution (pH=8.5) at a ratio of 1g:15mL. The solution was stirred in a water bath at 45℃ for 2 hours. The resulting slurry was centrifuged at 6000rpm for 30 minutes, and the supernatant (referred to as the first supernatant) was collected. One-third of the first supernatant was used to extract SPI, and two-thirds of the first supernatant was used to extract soybean 7S globulin and soybean 11S globulin. The specific steps are as follows: The pH of 1 / 3 of the first supernatant was adjusted to 4.6 with 3M hydrochloric acid, and allowed to precipitate naturally. The precipitate was then centrifuged at 6000 rpm for 30 min. The precipitate was washed with ultrapure water and dissolved in ultrapure water at a ratio of 1 g: 10 mL. The pH of the resulting solution was adjusted to 7.0 with 3M NaOH aqueous solution. The solution was dialyzed at 4 °C for 48 h (the molecular weight cutoff of the dialysis bag used was 8~14 kDa). After lyophilization, SPI was obtained. The pH of 2 / 3 of the first supernatant was adjusted to 6.4 using 3M hydrochloric acid and allowed to stand at 4°C for 2 hours. Then, it was centrifuged at 6000 rpm for 30 minutes. The supernatant (referred to as the second supernatant, used to prepare soybean 11S globulin) and the precipitate were collected separately. The precipitate was washed with ultrapure water and dissolved in ultrapure water at a ratio of 1 g: 10 mL. The pH of the resulting solution was adjusted to 7.5 using 3M NaOH aqueous solution. The solution was dialyzed at 4°C for 48 hours (the molecular weight cutoff of the dialysis bag used was 8~14 kDa). After freeze-drying, soybean 11S globulin was obtained. The pH of the second supernatant was adjusted to 5.5 with 3M hydrochloric acid, and the solution was allowed to stand at 4°C for 2 hours. Then, it was centrifuged at 6000 rpm for 30 minutes, and the supernatant was collected. The pH of the supernatant was adjusted to 4.8 with 3M hydrochloric acid, and then centrifuged at 6000 rpm for 30 minutes. The precipitate was collected, washed with ultrapure water, and dissolved in ultrapure water at a ratio of 1 g: 10 mL. The pH of the resulting solution was adjusted to 7.5 with 3M NaOH aqueous solution, and dialyzed at 4°C for 48 hours (the molecular weight cutoff of the dialysis bag used was 8~14 kDa). After that, the solution was freeze-dried to obtain soybean 7S globulin.

[0031] Example 1 (1) Soybean protein amyloid fiber (SPF), soybean 7S globulin amyloid fiber (7SF) and soybean 11S globulin amyloid fiber (11SF) were prepared by acid-heat method. The specific steps are as follows: SPI, soybean 7S globulin, and soybean 11S globulin were each mixed with ultrapure water to a final concentration of 20 mg / mL. The mixtures were stirred at room temperature (25°C) for 2 hours to ensure complete dissolution. The pH of the resulting solution was then adjusted to 2.0 using 3M hydrochloric acid, and hydrated at 4°C for 12 hours. The solution was then centrifuged at 9000 rpm for 30 minutes, and the supernatant was collected. The protein concentration of the supernatant was determined using the BCA method. The concentration was adjusted to 12 mg / mL using water with pH 2.0 (with 3M hydrochloric acid used to adjust the pH). The solution was then placed in an 85°C water bath and heated at 200 rpm for 6 hours with continuous stirring. Samples were taken at regular intervals and immediately stored at 4°C or freeze-dried (except for the subsequent FTIR experiment which used lyophilized powder, all other experiments used protein solutions directly). SPF, 7SF, and 11SF were obtained, respectively. (2) Seed-enhanced SPF formation, the specific steps are as follows: SPF and 7SF obtained by heating for 6 hours were used as seeds (the two types of seeds were denoted as SPI seeds and 7S seeds, respectively). Three groups of experiments were set up. Specifically, the SPI group without seeds was used as the blank control (Control), the group with added SPI seeds was used as the positive control, and the group with added 7S seeds was used as the experimental group. The seed solution with a concentration of 12 mg / mL prepared in step (1) was added to the SPI solution with a concentration of 12 mg / mL (the solvent was water with pH=2.0, and the pH value was adjusted by 3M hydrochloric acid). The seed mass was 5%, 10%, 20%, and 30% of the SPI mass in the SPI solution, respectively. The samples of each group were continuously stirred in an 85℃ water bath at 200 rpm for 6 hours. Samples were taken at regular intervals and immediately stored in a 4℃ refrigerator or freeze-dried (except for the subsequent FTIR experiment which used freeze-dried powder, the other experiments used fiber dispersion directly). The blank control group (Control) and soybean protein starch-like fiber (SPF-X% SPI, where X% represents the amount of seeds added, specifically SPF-5%) were obtained. SPI, SPF-10% SPI, SPF-20% SPI, SPF-30% SPI) and soybean protein amyloid fiber fortified with X% 7S seeds (SPF-X% 7S, where X% represents the amount of seeds added, specifically SPF-5% 7S, SPF-10% 7S, SPF-20% 7S, SPF-30% 7S); (3) The preparation of the fiber-iron complex is as follows: A FeSO4·7H2O solution containing ascorbic acid was prepared (the mass ratio of ascorbic acid to iron was 2:1, and the concentration of FeSO4·7H2O was 0.3 mol / L). This FeSO4·7H2O solution was added to the 12 mg / mL fiber dispersion prepared in step (2), making the mass ratio of fiber to FeSO4·7H2O 3:1. The pH of the resulting mixture was then adjusted to 6 using a 3M NaOH aqueous solution, and stirred continuously at 200 rpm for 40 min at room temperature. This yielded soybean protein amyloid fiber-iron complex (SPF-Fe), soybean 7S globulin amyloid fiber-iron complex (7SF-Fe), soybean 11S globulin amyloid fiber-iron complex (11SF-Fe), 20% SPI seed-fortified soybean protein amyloid fiber-iron complex (SPF-20% SPI-Fe), and 20% 7S seed-fortified soybean protein amyloid fiber-iron complex (SPF-20%). 7S-Fe) was stored in a refrigerator at 4°C (the fiber-iron composite solution was used directly in subsequent experiments).

[0032] Test Example 1 Monitoring of growth kinetics of soybean amyloid fibers: 8.0 mg ThT was mixed with 10 mL PBS (pH=7.0, containing 150 mM NaCl), stirred for 20 min to dissolve, and then filtered through a 0.22 μm microporous membrane to obtain a ThT stock solution (0.08%, w / v), stored at 4℃ in the dark. Before use, the ThT stock solution was diluted 50 times with PBS to obtain a ThT working solution. 15 μL of soybean amyloid fiber sample (concentration 12 mg / mL) was mixed with 135 μL of pH=2.0 ultrapure water, and 2850 μL of ThT working solution was added. The mixture was incubated in the dark for 10 min, and the ThT fluorescence intensity of the sample was measured using a microplate reader at an excitation wavelength of 440 nm and an emission wavelength of 485 nm. The fiber growth kinetics were fitted using an exponential plateau model according to Equation 1. Formula 1; In Equation 1, t is the heating time, in hours; Y M Y0 is the fluorescence intensity at 0 h, in au; k is the apparent rate constant, in au / h.

[0033] Figure 1The graphs show the changes in ThT fluorescence intensity of SPF enhanced with SPI and 7S seeds at 6 h and 1 h during the fibrillation process. A represents the change in ThT fluorescence intensity of SPF enhanced with SPI seeds at 6 h during fibrillation, B represents the change at 1 h, C represents the change at 6 h, and D represents the change at 1 h. The results show that the ThT fluorescence intensity of all samples increased rapidly in the early stages of the reaction and eventually plateaued, without a lag phase. (Magnified images from 0–60 min are also shown.) Figure 1 Figures B and D show that the introduction of seeds significantly altered the ThT growth kinetics curve, with the initial fluorescence intensity increasing significantly with the increase of the sowing ratio. The initial fluorescence intensity of the 7S seed group increased significantly more than that of the SPI seed group with the same ratio, indicating that the 7S seeds can provide a better template.

[0034] To further quantitatively assess the differences in fibrillation kinetics, the ThT fluorescence curves were fitted using a plateau index model. The results are shown in Table 1. 2 Both values ​​were greater than 0.95, indicating a good model fit. Specifically, for the homologous SPI seed group, the Y0 value increased with the increase of the seeding ratio, gradually rising from 1284 in the Control group to 3147, indicating that the seeds directly provided a large number of nucleation sites for the system. Simultaneously, the k value also showed an increasing trend, indicating that an appropriate amount of homologous seeds can effectively accelerate polypeptide chain elongation. At a 30% addition ratio, k and Y... M All showed a decline, a phenomenon that may be related to the composition of the SPI seed. In a pH 2.0 environment, homologous proteins with similar high-density positive charges tend to exhibit electrostatic repulsion when close together. Spatial hindrance and mutual interference caused by the mixing of different structural fragments can inhibit fiber assembly under high seed ratio conditions. In contrast, the single-component 7S seed exhibited superior induction ability. The addition of 7S seeds significantly increased the system's Y0 value, with the 30% addition group reaching 5523, significantly higher than the SPI seed group with the same proportion. Furthermore, the Y0 value of the 7S seed group... M The value did not decline and continued to increase with the increase of the 7S seed addition ratio, reaching a peak of 10465 at a 30% addition level, which is about 38.7% higher than the control group. This result may be related to the sequence matching of proteins; 7S seeds can more efficiently guide the fibrinolysis of soybean 7S globulin in SPI, promoting the participation of more polypeptide chains in assembly, ultimately manifesting as Y M The increase.

[0035] Table 1. Growth kinetic fitting parameters of SPF enhanced by SPI and 7S seeds.

[0036] Test Example 2 Morphological observation and quantitative analysis of soybean protein amyloid fibers: The sample was diluted with ultrapure water at pH 2.0 to a concentration of 0.1 mg / mL. 5 μL of the diluted solution was placed on a carbon film. After the sample was allowed to dry naturally at room temperature, it was stained with phosphotungstic acid. Excess staining was removed with filter paper, and the sample was observed using TEM after 15 minutes. The rigidity and flexibility of the fiber TEM images were analyzed using FiberApp. The effect of seed addition ratio on the number and length of SPF formation was also evaluated. Since the added seeds themselves contain pre-formed fibers, a normalization method was used to correct the data to avoid interference with the statistical analysis of the induced fiber number: the control group without added seeds was used as the baseline (set to 1), and the measured fiber number of the other groups was calculated and corrected according to Equation 2. Correction value = Measured value / (1 + Seed addition ratio) Equation 2.

[0037] Figure 2 TEM images of SPF enhanced with SPI and 7S seeds show that the addition of seeds alters the morphological distribution of the SPF and exhibits a clear template dependence. Specifically, after enhancement with SPI seeds, the fiber system maintains its original mixed morphology, containing both coiled fibers formed by soybean 7S globulin and long, straight fibers formed by soybean 11S globulin. Furthermore, the fiber density within the field of view significantly increases with the increase in the seed proportion. In contrast, the morphology of SPF enhanced with 7S seeds undergoes a significant transformation. Long, straight fibers are almost entirely absent in the TEM images, and the overall morphology develops towards a coiled, entangled fiber pattern, which becomes more pronounced with increasing seed proportion.

[0038] Figure 3 The images show the morphological distribution of SPF enhanced with SPI and 7S seeds, where A represents the morphological distribution of SPF enhanced with SPI seeds and B represents the morphological distribution of SPF enhanced with 7S seeds. The results show that the rigid fiber proportion in the control group was approximately 11.56%. While the proportions of rigid, semi-flexible, and flexible fibers in the SPI seed group fluctuated with increasing seed addition, the overall distribution characteristics remained largely consistent with the control group. In the 7S seed-enhanced SPF system, the proportion of rigid fibers was significantly lower than both the control and SPI seed groups, remaining at a low level regardless of seed addition ratios. Under acid-heat conditions, soybean 11S globulin was the main source of long, straight, rigid fibers. These results further confirm the observations of TEM, namely that the induction of 7S seeds in the SPI system is targeted, inducing the system to transform into coiled and entangled 7SF. This may be due to the sequence mismatch between 7S seeds and 11S monomers, resulting in the morphology of the SPF enhanced with 7S seeds being predominantly 7S.

[0039] Figure 4 The charts show the number of SPFs formed and the proportion of long fibers (>100nm) enhanced by SPI and 7S seeds, respectively. Chart A shows the number of SPFs formed and the proportion of long fibers enhanced by SPI seeds, and chart B shows the number of SPFs formed and the proportion of long fibers enhanced by 7S seeds. The results show that the number of fibers, corrected according to Equation 2, did not differ significantly under different seed types and addition ratios. However, the proportion of fibers longer than 100nm showed a significant increasing trend with increasing seed ratio. This phenomenon suggests that SPI and 7S seeds may capture more peptide monomers generated by acid hydrolysis for elongation, thereby accelerating fiber formation.

[0040] Test Example 3 To investigate the digestive characteristics of seed-fortified SPF (heated for 6 h) in the gastrointestinal tract, an in vitro simulated digestion model using INFUGEST 2.0 was employed. Combined with ThT fluorescence intensity measurements and protein hydrolysis degree analysis, the structural changes and degradation behavior of various fiber systems in simulated gastric juice (SGF) and simulated intestinal juice (SIF) were examined. Specifically, this included the ThT fluorescence intensity loss rate and protein hydrolysis degree measurement of soybean protein amyloid fiber during simulated digestion. The steps are as follows: Th T fluorescence intensity loss rate determination: Preheated (37℃, 10 min) SGF stock solution (pH=3.0) was mixed with the sample (concentration 12 mg / mL) at a 1:1 (v / v) ratio. Pepsin was added to bring the final protease activity to 2000 U / mL. The pH was adjusted to 3.0 using 1 mol / L hydrochloric acid, and the mixture was subjected to gastric digestion for 120 min in a constant temperature shaker (37℃, 150 rpm). The gastric digestion phase was then terminated by adjusting the pH to 7.0 using 1 M NaOH solution. During gastric digestion, certain intervals were observed... At each gastric digestion system, 200 μL of the digested sample was taken and placed in an ice bath. After gastric digestion, intestinal digestion experiments were performed. Specifically, secretin and ox bile salts were dissolved in preheated (37°C, 10 min) SIF stock solution (pH=7.0) and added to the gastric digestion system at a 1:1 (v / v) ratio. The final concentrations of ox bile salts and secretin during intestinal digestion were 10 mmol / L and 100 U / mL, respectively. The system was then placed in a constant-temperature shaker (37°C, 150 rpm) for 120 min of intestinal digestion. Intestinal digestion samples were collected at regular intervals during intestinal digestion and placed in an ice bath. The Th T fluorescence intensity loss rate was calculated according to Equation 3. Formula 3; In Equation 3, I0 represents the Th T fluorescence intensity at 0 min during gastric or intestinal digestion. tThe fluorescence intensity of ThT is the fluorescence intensity of ThT at t min during gastric or intestinal digestion.

[0041] Protein hydrolysis degree determination (the amount of free amino released was determined by the OPA method, and the digestibility of fiber in the stomach and intestine was evaluated by the protein hydrolysis degree): 3.81 g of disodium tetraborate decahydrate was mixed with 90 mL of deionized water (pH adjusted to 9.5), stirred and dissolved, and then 0.1 g of sodium dodecyl sulfate (SDS) was added. The solution was heated to 45 °C to obtain solution S1. Separately, 80 mg of o-phthalaldehyde (OPA) and 0.088 g of dithiothreitol (DTT, a thiol reducing agent) were dissolved in 2 mL of ethanol, and then added to solution S1. The solution was then diluted to 100 mL with deionized water to obtain OPA solution, which was stored at 4 °C protected from light. Before determining total free amino groups, the sample needs to be fully hydrolyzed, as follows: Dilute 100 μL of sample (concentration of 12 mg / mL) to 1 mL with 6 M hydrochloric acid and hydrolyze at 110 °C for 24 h; neutralize the hydrolyzed sample with 1 mL of 6 M NaOH solution, and finally dilute to 10 mL with deionized water; for determination, dilute 100 μL of sample (total free amino group sample dilution factor 100-fold, gastric and intestinal digested samples dilution factor 10-fold, undigested samples dilution factor 10-fold), add 2 mL of OPA solution, react for 5 s, let stand at room temperature in the dark for 2 min, and measure absorbance at 340 nm. Plot a standard curve using leucine solutions of different concentrations (0~0.5 mg / mL), fit the curve, and calculate the free amino group content of the sample based on the standard curve. The result is expressed as leucine equivalent in mmol / L; then, calculate the degree of protein hydrolysis in the gastric and intestinal digestion stages using Equation 4. Equation 4; In Equation 4, A t A represents the free amino content during gastric or intestinal digestion (t min), and A0 represents the free amino content during gastric digestion (0 min). T This represents the total free amino content.

[0042] Figure 5 The figures show the ThT fluorescence loss rate test results of SPF enhanced with SPI seeds and 7S seeds in SGF and SIF, respectively. Figure A shows the ThT fluorescence loss rate test results of SPF enhanced with SPI seeds in SGF, Figure B shows the ThT fluorescence loss rate test results of SPF enhanced with SPI seeds in SIF, Figure C shows the ThT fluorescence loss rate test results of SPF enhanced with 7S seeds in SGF, and Figure D shows the ThT fluorescence loss rate test results of SPF enhanced with 7S seeds in SIF. This indicates that during the gastric digestion stage (… Figure 5In systems A and C, the Th-T fluorescence loss rate within 120 min remained in the low range of 20-30%. The fluorescence loss rate in the control group without seeds was the highest, approaching 30%. The SPF fluorescence loss rate enhanced by SPI seeds and 7S seeds was generally lower than that in the control group, and this difference was more pronounced at seed addition ratios of 10-30%. The fiber in each group during the intestinal digestion stage (… Figure 5 Both B and D samples underwent rapid degradation, with ThT fluorescence loss rates exceeding 90% at 120 min. Despite being highly hydrolyzed, the ThT fluorescence loss rate of the seed-enhanced SPF was still slightly lower than that of the control group. These results indicate that the seed-enhanced SPF exhibits stronger structural stability during both gastric and intestinal digestion.

[0043] Figure 6 The statistical chart shows the release of free amino acids in SPF enhanced with SPI and 7S seeds during simulated digestion. The results indicate that after 120 minutes of simulated gastric digestion, the free amino acid content increased in all systems. The free amino acid release in the control group without seeds reached 22 mmol / L. The free amino acid release in the SPF systems enhanced with SPI and 7S seeds was generally lower than that in the control group, with the 7S seed group showing a greater decrease. The SPF-20% 7S group only increased to 16 mmol / L, indicating that the introduction of a high proportion of 7S seeds effectively inhibited the hydrolysis of peptide bonds by pepsin. After 120 minutes of simulated intestinal digestion, the free amino acid content in all samples increased significantly, generally falling within the range of 54–63 mmol / L, indicating that regardless of the resistance exhibited in the stomach, all fiber systems underwent deep hydrolysis in the intestinal environment.

[0044] The degree of protein hydrolysis and total protein hydrolysis of each system during gastric and intestinal digestion were calculated based on the free amino content, and the results are listed in Table 2. It can be seen that the control group without added seeds exhibited the highest degree of protein hydrolysis (6.24%) during gastric digestion, while the degree of protein hydrolysis in all seed-enriched groups generally decreased. Specifically, the degree of protein hydrolysis of SPF enhanced with SPI seeds during gastric digestion decreased slightly with increasing seed addition ratio, but the difference from the control group was not significant. The decrease in the degree of protein hydrolysis of SPF enhanced with 7S seeds was more pronounced, with SPF-20% 7S showing the lowest degree of protein hydrolysis at 3.03% during gastric digestion, a reduction of 51.44% compared to the control group. This result is consistent with the Th T fluorescence loss rate, demonstrating that seed-enriched SPF has better structural stability in the gastric environment. During intestinal digestion, the degree of protein hydrolysis in the control group was 28.15%, and the total degree of protein hydrolysis was 34.39%. SPF-20% 7S, which exhibited the strongest resistance to enzymatic hydrolysis in the gastric environment, also demonstrated a high degree of protein hydrolysis (33.85%) in intestinal fluid, ultimately exceeding the total protein hydrolysis of the control group without seeds and all SPI seed groups. These results suggest that the introduction of different seed types altered fiber digestion behavior. SPF enhanced with 7S seeds showed the strongest gastric resistance, possibly related to the highly coiled and entangled morphology of the SPF after enhancement, which reduced the accessibility of digestive enzymes.

[0045] Table 2. Degree of proteolysis during simulated digestion of SPF enhanced with SPI and 7S seeds.

[0046] Test Example 4 Determination of iron loading of soybean protein amyloid fiber: SPF and Fe were reacted according to the method in Example 1. 2+ After combination, 40 mL of 95% pure ethanol was added, and the mixture was allowed to stand for 30 min. Then, it was centrifuged at 7000 rpm for 20 min to remove excess iron ions. The precipitate was collected, and the process of adding ethanol and centrifugation was repeated three times. The precipitate was collected and vacuum dried to obtain fiber-iron complex powder. Then, Fe was added at a concentration of 1 mg / mL. 2+ The standard solution was used as the mother liquor, and Fe was prepared by stepwise dilution. 2+ A series of standard working solutions with concentrations of 0, 0.01 mg / mL, 0.02 mg / mL, 0.04 mg / mL, 0.06 mg / mL, 0.08 mg / mL, and 0.1 mg / mL were prepared. Then, 0.1 mL of each standard working solution was added to 1 mL of 0.2 M acetate-sodium acetate buffer (pH=5.0) and 1 mL of 20 mg / mL ascorbic acid solution. After mixing, 400 μL of 5 mg / mL 1,10-phenanthroline solution was added. The mixture was reacted in the dark for 15 min, with ultrapure water used as a blank control. Based on Fe... 2+A standard curve was plotted based on the concentration, and the absorbance was measured at 512 nm. To completely dissociate iron ions, the fiber-iron composite powder was acid-hydrolyzed with 6M hydrochloric acid at 110°C for 24 h. Following the same operating procedures as described above, the iron loading rate was determined using the standard curve and calculated according to Equation 5. Formula 5; In Formula 5, m1 represents the Fe in the fiber-iron composite powder. 2+ Mass (mg), m0 is the amount of Fe added to the solution 2+ Total mass (mg).

[0047] In addition, the iron content of the fiber-iron complex was determined by energy dispersive spectroscopy (EDS). To more accurately compare the iron loading capacity of different fibers, the relative iron content after homogenization was calculated with reference to the relatively constant nitrogen content (set at 16%) in the protein backbone.

[0048] Figure 7 The figure shows the iron loading rate test results for different fiber-iron complexes. It can be seen that under the loading conditions of pH=6 and a fiber-to-FeSO4 mass ratio of 3:1, the iron loading rates of the five fibers showed significant differences. Among them, 7SF had the highest iron loading rate at 60.20%, while 11SF had the lowest at only 44.40%. The SPF-20% 7S enriched with 7S seeds achieved an iron loading rate of 56.52%, significantly higher than SPF (50.05%) and SPF-20% SPI (48.27%). The difference in iron loading rate stems from the abundance of acidic amino acids such as aspartic acid and glutamic acid in the natural sequence of 7S globulin. These residues with free carboxyl groups on their side chains are the core sites for metal ion coordination, directly enhancing the iron loading capacity of the fiber. The iron loading rate may also be related to the differences in the microstructure of different fibers. Due to the lack of rigid disulfide bonds, 7SF forms a highly coiled and densely entangled network fiber, resulting in a denser coordination and binding region for iron ions, thus increasing the iron loading rate. SPF-20% 7S combines the abundant coordination binding sites of SPI with the high-density network fiber morphology of 7SF, thus exhibiting a high iron loading capacity.

[0049] Figure 8 The images show the energy dispersive spectroscopy (EDS) analysis of different fiber-iron composites. A represents SPF-Fe, B represents 7SF-Fe, C represents 11SF-Fe, D represents SPF-20% SPI-Fe, E represents SPF-20% 7S-Fe, and F represents the blank control. The results show that the Blank group represents a blank background region with no obvious fiber aggregation in SPF. Apart from carbon and oxygen introduced by the support film and a small amount of background iron signal, no other obvious characteristic peaks were detected. Figure 8(F). Characteristic peaks of carbon, nitrogen, oxygen, and sulfur, representing the basic backbone of protein polypeptide chains, were detected in all samples from the fiber distribution area. Simultaneously, all five fiber-iron complex samples showed a distinct iron characteristic peak near 6.4 keV. These results confirm that Fe... 2+ It does not exist as a free precipitate, but is bound to the fibrous skeleton.

[0050] Figure 9 The graph shows the homogenized iron content test results for different fiber-iron composites. It reveals significant differences in iron content among the composites, with 7SF-Fe having the highest iron content at 9.40%, and 11SF-Fe having the lowest at 5.16%. The iron contents of the fiber-iron composites formed by seed-fortified SPF-20% SPI and SPF-20% 7S are 8.13% and 8.27%, respectively, both higher than the iron content in unfortified SPF-Fe (6.99%). This trend is consistent with the iron loading rate test results, further confirming that the iron loading capacity of fibers is closely related to their microstructure and the number of surface coordination sites.

[0051] Test Example 5 FTIR characterization of the fiber system before and after iron loading was performed to clarify the relationship between the five fibers and Fe. 2+ Binding method: The freeze-dried fiber sample was placed above an ATR crystal, and Fourier transform infrared spectroscopy was used to analyze the sample at 4000~400cm. -1 Within a range of 4cm -1 The sample was scanned 64 times at a high resolution, and the resulting spectra were corrected by ATR before analysis.

[0052] Figure 10 Fourier transform infrared spectra of different fiber systems before and after iron loading are shown, where A represents SPF, B represents 7SF, C represents 11SF, D represents SPF-20% SPI, and E represents SPF-20% 7S. The results show that Fe... 2+ After loading, all fiber systems are between 3271 and 3287 cm. -1 The NH and OH stretching vibration peaks within the range showed significant shifts, indicating that the -NH and -OH groups on the fiber participated in the Fe... 2+ Coordination. 1646~1650cm -1 The absorption peak of the C=O vibration of the amide I band in the vicinity shifts significantly to lower wavenumbers, with the peak position of SPF-20% SPI shifting from 1646 cm⁻¹. -1 Moved to 1633cm -1 This indicates that the C=O group in the peptide backbone is also Fe. 2+ The coordination sites. After iron loading, the fibers range from 1395 to 1452 cm⁻¹. -1The characteristic peaks of nearby free carboxyl groups also shifted, a change caused by the formation of the -COO-Fe complex, confirming that the carboxyl groups on the side chains of aspartic acid and glutamic acid residues are fibrous-bound Fe. 2+ The core site. All fiber-iron complexes are located at 1135–1140 cm⁻¹. -1 A new characteristic absorption band appears, which is related to the CO-Fe bond formed by the coordination reaction. The regular changes in the above characteristic peaks indicate that all types of fibers mainly bind to Fe through carboxyl, carbonyl, amino, and hydroxyl groups. 2+ Coordination occurs. Because 7S globulin contains higher levels of acidic amino acids such as glutamic acid and aspartic acid, and basic amino acids such as histidine, arginine, and lysine than 11S globulin, they can coordinate with Fe... 2+ Therefore, both 7SF and SPF-20% 7S have high iron loading rates.

[0053] Test Example 6 In vitro simulated digestion was conducted on five types of fiber-iron complexes, and free Fe was systematically tracked throughout the digestion process. 2+ Content, release rate, and valence stability were used to evaluate the actual effect of the fiber as a iron carrier, including free Fe content. 2+ The content can directly reflect the amount of iron in the digestive juice that can be potentially absorbed.

[0054] Fiber-iron complex releases free Fe during simulated digestion 2+ Release rate and proportion were determined as follows: Samples were taken at different time points during gastric and intestinal digestion. The samples were centrifuged at 10,000 rpm for 10 min, and the supernatant was collected for analysis. Specifically, free Fe... 2+ The content was determined as follows: Take 0.1 mL of supernatant, add 1 mL of 0.2 M acetate-sodium acetate buffer (pH=5.0), mix well, then add 400 μL of 5 mg / mL 1,10-phenanthroline solution, react in the dark for 15 min, and measure the absorbance at 512 nm. The free total iron content was determined as follows: Take 0.1 mL of supernatant, first add 1 mL of 20 mg / mL ascorbic acid solution to allow free Fe to be released. 3+ Reduced to Fe 2+ Subsequently, referring to free Fe 2+ The method for determining the content involved adding the same acetate-sodium acetate buffer and 1,10-phenanthroline solution, reacting in the dark for 15 min, and measuring the absorbance at 512 nm. Free Fe was then separately established. 2+ A standard curve for total free iron was used to calculate the free Fe content in each digested sample. 2+ And the total free iron content, and then calculate Fe according to Equation 6. 2+ Release rate, to evaluate the fiber's protective effect on the loaded iron and its release behavior: Formula 6; In Equation 6, C t Free Fe for gastric or intestinal digestion (t min) 2+ Content, C0 is the free Fe content after 0 minutes of gastric or intestinal digestion. 2+ Content, C s For the total Fe added 2+ Content, in mg / mL.

[0055] In addition, to assess the antioxidant protection of iron valence state by fiber during digestion, free Fe was calculated according to Equation 7. 2+ Percentage: Formula 7; In Equation 7, C t Free Fe for gastric or intestinal digestion (t min) 2+ Content, C T Total free Fe for gastric or intestinal digestion (t min) 2+ Content, in mg / mL.

[0056] Figure 11 Free Fe in different fiber-iron complexes during simulated digestion 2+ The content test results are shown in the figure, where A corresponds to SGF (i.e., simulating gastric digestion) and B corresponds to SIF (i.e., simulating intestinal digestion). This indicates that in the initial stage of gastric digestion (0 min), the free Fe in each system... 2+ The content varies significantly and is related to the initial iron loading: the 7SF-Fe system has the highest iron loading, with the highest initial free Fe content. 2+ The lowest concentration was observed. During a 120-minute gastric digestion process, the free Fe concentrations in each group were [data missing]. 2+ The content showed a slow upward trend. After entering the intestinal digestion stage, all systems had free Fe at 0 min. 2+ The contents all decreased significantly, mainly due to the change in pH; the neutral intestinal fluid caused the free Fe to... 2+ Rapid hydrolysis and oxidation form a poorly soluble precipitate. Subsequently, under the action of secretin, free Fe... 2+ The content slowly recovers, with the final free Fe of 7SF-Fe and SPF-20% 7S-Fe increasing. 2+ Its content is significantly higher than that of other fibers.

[0057] Figure 12 Fe in different fiber-iron complexes during simulated digestion 2+The release rate test results are shown in Tables 3 and 4, where A corresponds to SGF (simulating gastric digestion) and B corresponds to SIF (simulating intestinal digestion). It can be seen that during gastric digestion, 11SF-Fe had the fastest release rate, reaching 29.84% at 120 min, the highest among all groups. The curves for 7SF-Fe and SPF-20% 7S-Fe groups were relatively flat, with release rates of only 20.24% and 24.12% respectively at 120 min, indicating significantly lower overall release levels. This difference may be related to the digestive properties of the fiber itself. 7SF and SPF-20% 7S form a high-density network of fibers, exhibiting stronger resistance to enzymatic degradation in gastric juice and effectively encapsulating and protecting Fe. 2+ This reduces the premature release of 7SF-Fe during gastric digestion. The 7SF-Fe and SPF-20% 7S-Fe groups, which release the slowest in the stomach, have a higher release rate after entering the intestinal digestion stage than other fibers. This is because 7SF is pH sensitive; electrostatic repulsion in a neutral environment causes fiber swelling, resulting in a large release of Fe. 2+ .

[0058] Table 3. Fe content of different fiber-iron complexes during simulated gastric digestion. 2+ Release rate

[0059] Table 4. Fe content of different fiber-iron complexes during simulated intestinal digestion. 2+ Release rate

[0060] Figure 13 To simulate the effects of different fiber-iron complexes on Fe during digestion 2+ The graph shows the results of the test for the proportion of total free iron, where A corresponds to SGF (simulating gastric digestion) and B corresponds to SIF (simulating intestinal digestion). Since intestinal epithelial cells primarily absorb Fe... 2+ Therefore, the ability of fibers to protect the iron valence state is crucial when acting as iron carriers. Figure 13 It can be seen that during the gastric digestion stage, a low pH environment inhibits oxidation reactions. Combined with the protective effect of fiber, the Fe content in all systems is reduced. 2+ The proportion of total free iron remained consistently above 90%. After entering the intestinal digestion stage, Fe... 2+ It is easily oxidized, therefore each group of Fe 2+ The proportions of both decreased. Specifically, in the 7SF-Fe and SPF-20% 7S-Fe groups, during a 120-minute intestinal digestion process, the Fe... 2+ The proportion was consistently significantly higher than that of 11SF-Fe and SPF-Fe, remaining at a high level. This indicates that 7S seed-fortified SPF effectively delays Fe degradation through reducing amino acid side chains.2+ The oxidation process makes Fe, which has high bioavailability, readily available. 2+ Maintain a high proportion. In summary, regarding Fe... 2+ In terms of intestinal-specific release and valence protection, the SPF-20%7S system enhanced with 7S seeds showed good performance.

[0061] From the above results, it can be seen that the present invention has at least the following beneficial effects: 1. This invention utilizes the product of the fibrosis reaction of β-conglycinin (soybean 7S globulin) as a seed (i.e., 7S seed) to accelerate the induction of fibrosis in SPI. Soybean 7S globulin is an important component of SPI, accounting for approximately 30-35%. Therefore, 7S seed can be used to accelerate the fibrosis rate of SPI, which is beneficial for reducing actual production energy consumption and production costs.

[0062] 2. The addition of 7S seeds in this invention alters the microstructure of SPF and enhances its resistance to digestion. SPF prepared directly using the traditional acid-heat method, or SPF fortified with SPI seeds (SPF-5%SPI, SPF-10%SPI, SPF-20%SPI, SPF-30%SPI), contains a large number of long, straight fibers, resulting in a high degree of hydrolysis during gastric digestion due to their large specific surface area. However, SPF fortified with 7S seeds (SPF-5% 7S, SPF-10% 7S, SPF-20% 7S, SPF-30% 7S) forms a high-density network of fibers, significantly enhancing its resistance to digestion in the stomach.

[0063] 3. This invention utilizes SPF enhanced with 7S seeds (SPF-20% 7S). Due to the high content of coordinating amino acids such as aspartic acid and glutamic acid in its sequence, and the high-density network fiber morphology, it can form denser iron ion coordination binding regions, thus achieving the binding of Fe... 2+ A highly efficient combination.

[0064] 4. This invention utilizes 7S seed-enhanced SPF (SPF-20% 7S) as a carrier to prepare fiber-iron composites, thereby protecting Fe through physical isolation and antioxidant environmental protection. 2+ During simulated digestion, this carrier can effectively delay the degradation of Fe. 2+ The early release of Fe and the accelerated release of Fe in the intestine can maintain Fe 2+ The valence state is stable, realizing Fe 2+ High bioavailability.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing soybean protein amyloid fibers, comprising the following steps: Soybean 7S globulin amyloid fiber is provided, wherein the soybean 7S globulin amyloid fiber is prepared from soybean 7S globulin by an acid-heat method; The soybean 7S globulin amyloid fiber was used as a seed and mixed with soybean protein isolate and water. The resulting mixture was subjected to fiberization treatment to obtain the soybean protein amyloid fiber.

2. The preparation method according to claim 1, characterized in that, The mass of the seeds is 1-30% of the soybean protein isolate; the total concentration of soybean protein isolate and seeds in the mixture is 10-50 mg / mL.

3. The preparation method according to claim 1 or 2, characterized in that, The fiberization treatment is carried out at a temperature of 70~90℃ for 4~24h.

4. The preparation method according to claim 1 or 2, characterized in that, The method for preparing soybean 7S globulin amyloid fibers includes the following steps: Soybean 7S globulin was dissolved in water to obtain a soybean 7S globulin solution. The pH value was adjusted to 1.5-3.0, and hydration treatment and fiber growth treatment were performed sequentially to obtain the soybean 7S globulin amyloid fiber.

5. The preparation method according to claim 4, characterized in that, The concentration of the soybean 7S globulin solution is 10~25 mg / mL; the hydration treatment temperature is 2~6℃ and the time is 8~24 h; the fiber growth treatment temperature is 70~90℃ and the time is 4~24 h.

6. Soybean protein starch-like fiber prepared by the preparation method according to any one of claims 1 to 5.

7. The use of the soybean protein amyloid fiber of claim 6 in the preparation of an iron delivery carrier.

8. A method for preparing a fiber-iron composite, comprising the following steps: The soybean protein starch-like fiber, ferrous salt, antioxidant, and water described in claim 6 are mixed and subjected to a compounding treatment to obtain the fiber-iron complex.

9. The fiber-iron composite prepared by the method of claim 8.

10. The use of the fiber-iron complex of claim 9 in the preparation of iron supplements.

Images