Wheat bran having a high content of soluble dietary fiber and a method for preparing the same

Abstract

The application belongs to the technical field of wheat bran modification, and particularly relates to wheat bran with high soluble dietary fiber content and a preparation method thereof. The preparation method comprises the following steps: S1, preparing a eutectic solvent; S2, preparing a diluted eutectic solvent-water solution by using the eutectic solvent and water; S3, adding the wheat bran into the eutectic solvent-water solution, stirring and heating to obtain treated material; S4, cooling the treated material to room temperature, adjusting pH, adding solvent A, and standing to obtain a solution system; and S5, filtering the solution system to obtain a filter cake, washing the filter cake, and sequentially drying, grinding and sieving the filter cake to obtain the wheat bran with high soluble dietary fiber content. The percentage content of soluble dietary fiber in the wheat bran with high soluble dietary fiber content prepared by using the preparation method is 29.72% to 46.08%, and the percentage content of total dietary fiber is 67.75% to 70.56%.

Description

Technical Field

[0001] This invention belongs to the field of wheat bran modification technology, specifically relating to a wheat bran with high soluble dietary fiber content and its preparation method. Background Technology

[0002] Globally, approximately 150 million tons of wheat bran are produced annually as a byproduct of wheat processing. However, they are primarily used as brewing raw materials or animal feed. Wheat bran contains 30%-50% dietary fiber, making it an ideal raw material for dietary fiber production. However, the dietary fiber in natural wheat bran is mainly insoluble, with soluble dietary fiber typically accounting for less than 10%. This low soluble dietary fiber content hinders the high-value utilization of wheat bran. Significantly increasing the soluble dietary fiber content of wheat bran has become a challenge. Therefore, this application provides a wheat bran with a high soluble dietary fiber content and its preparation method. Summary of the Invention

[0003] To address the above problems, this invention provides wheat bran with high soluble dietary fiber content and its preparation method.

[0004] To achieve the above objectives, the technical solution adopted in this experiment is as follows: A type of wheat bran with high soluble dietary fiber content, wherein the percentage content of soluble dietary fiber (SDF) in the wheat bran is 29.72% to 46.08%, and the percentage content of total dietary fiber is 67.75% to 70.56%.

[0005] A method for preparing wheat bran with high soluble dietary fiber content includes the following steps: S1. Preparation of eutectic solvent; S2. Prepare a diluted eutectic solvent-water solution using a eutectic solvent and water; S3. Add wheat bran to a eutectic solvent-water solution, stir and heat to obtain the treated material; S4. Cool the treated material to room temperature, adjust the pH, add solvent A, and let it stand to obtain the solution system; S5. Filter the solution system to obtain a filter cake. Wash the filter cake with solvent B. Dry, grind and sieve the filter cake in sequence to obtain wheat bran with high soluble dietary fiber content.

[0006] Preferably, step S1 includes the following steps: mixing choline chloride, citric acid, and glycerol, heating to 75-85°C under stirring conditions, and stirring at a constant temperature of 75-85°C for 100-150 minutes at a stirring speed of 55-65 rpm; then naturally cooling to room temperature to obtain a eutectic solvent.

[0007] Preferably, in step S1, the mass ratio of choline chloride, citric acid, and glycerol is (3.2-3.8):(9.3-9.9):(6.6-7.2).

[0008] Preferably, step S2 includes the following steps: mixing a eutectic solvent and water, and heating in a water bath at 75-85°C for 4-6 minutes to obtain a eutectic solvent-water solution.

[0009] Preferably, in step S2, the mass ratio of the eutectic solvent to water is (10-30):(70-90).

[0010] Preferably, step S3 includes the following steps: adding wheat bran to a eutectic solvent-water solution, heating in a water bath at 75-85°C for 30-150 minutes, continuously stirring during the heating process at a stirring speed of 55-65 rpm, to obtain the processed material.

[0011] Preferably, in step S3, the mass-to-volume ratio of wheat bran to eutectic solvent-water solution is (4-6) g:(80-120) mL.

[0012] Preferably, step S4 includes the following steps: cooling the treated material to room temperature, adjusting the pH of the treated material to 6.5-7.5 with sodium hydroxide solution to obtain a liquid, then adding solvent A to the liquid and letting it stand for 1-1.5 hours to obtain a solution system.

[0013] Preferably, solvent A is one of anhydrous ethanol and isopropanol.

[0014] Preferably, solvent B is one of anhydrous ethanol and isopropanol.

[0015] Preferably, in step S4, the volume of anhydrous ethanol is the same as the volume of the feed liquid.

[0016] Preferably, in step S5, the filter cake is dried at 55–65°C for 16–20 hours.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The wheat bran with high soluble dietary fiber content prepared using the method described in this application has a dense network of pores on its surface, as well as many small particles. This may be because the method described in this application disrupts the intermolecular cross-linking between insoluble dietary fibers such as cellulose, lignin, and hemicellulose in the outer cell wall of the wheat bran. The eutectic solvent can penetrate into the gaps between the wheat bran layers, dissolving some hemicellulose and starch, which weakens the bonding between the wheat bran layers. At the same time, the swelling effect caused by the eutectic solvent leads to the peeling and loosening of the layer structure, thereby destroying the original dense layer structure of the wheat bran raw material and forming a rich network of pores and voids.

[0018] Wheat bran, high in soluble dietary fiber, has a dense porous structure, which enhances its adsorption of sodium tauronate. This is likely because the larger specific surface area of ​​the porous structure increases the number of adsorption contact sites on the wheat bran, leading to an increase in the exposure sites of active groups (such as carboxyl, hydroxyl, and carbonyl groups). The increased number of adsorption contact sites enhances the adsorption and binding capacity of wheat bran for sodium tauronate, while the increased exposure sites of active groups allow for more interactions between these groups and sodium tauronate molecules, further improving the adsorption effect. Furthermore, the wheat bran prepared in this application with high soluble dietary fiber content has a dense porous structure and a high soluble dietary fiber content, which results in a better adsorption effect on cholesterol. This may be because soluble dietary fiber contains a large number of polar groups such as hydroxyl and carboxyl groups. The increased soluble dietary fiber content in the wheat bran prepared in Example 1 results in more polar groups such as hydroxyl and carboxyl groups in the wheat bran. These polar groups will bind to cholesterol through hydrogen bonds, hydrophobic interactions, and electrostatic adsorption. The large specific surface area of ​​the porous structure will also have a physical interception and encapsulation effect on cholesterol, thus enabling the wheat bran prepared in Example 1 with high soluble dietary fiber content to have a better adsorption effect on cholesterol. Attached Figure Description

[0019] Figure 1 The results of scanning electron microscopy at 500× magnification are shown for the wheat bran sample in Comparative Example 1. Figure 2 The results of scanning electron microscopy at 500× magnification are shown for the wheat bran sample in Comparative Example 2. Figure 3 The results of scanning electron microscopy at 500× magnification are shown for the wheat bran sample in Comparative Example 3. Figure 4 The results of the microstructure characterization of the wheat bran sample in Example 1 using a scanning electron microscope at 500× magnification; Figure 5 The results of the microstructure characterization of the wheat bran sample in Example 1 using a scanning electron microscope at 1000× magnification; Figure 6 The results of the microstructure characterization of the wheat bran sample in Example 2 using a scanning electron microscope at 500× magnification; Figure 7 The results of the microscopic morphology characterization of the wheat bran sample in Example 3 by scanning electron microscopy at 500× magnification; Figure 8 The results of the microstructure characterization of the wheat bran sample in Example 4 using a scanning electron microscope at 500× magnification; Figure 9 The results of the microstructure characterization of the wheat bran sample in Example 5 by scanning electron microscopy at 500× magnification; Figure 10 The FTIR spectra of the samples in Examples 1-4 and Comparative Examples 1-3 are shown. Figure 11 The XRD patterns of the samples in Examples 1-4 and Comparative Examples 1-3 are shown. Figure 12 The results show the adsorption capacity tests of sodium taurocholate and cholesterol for the samples of Examples 1, 5 and Comparative Example 1. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments thereof. Of course, the described embodiments are merely a part of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1:

[0022] A method for preparing wheat bran with high soluble dietary fiber content includes the following steps: Step S1, Preparation of eutectic solvent: 3.5g choline chloride, 9.6g citric acid, and 6.9g glycerol were mixed to obtain a mixture. Then, under stirring conditions, the mixture was heated to 80°C in an oil bath and stirred at a constant temperature of 80°C for 2 hours at a stirring speed of 60 rpm. After that, it was naturally cooled to room temperature to obtain the eutectic solvent. In this application, the mixture obtained after stirring for 2 hours is a transparent liquid, and the mixture is also a transparent liquid after naturally cooling to room temperature. Step S2: Mix 20g of eutectic solvent and 80g of water, and heat in a water bath at 80°C for 5 minutes to obtain eutectic solvent-water solution. The eutectic solvent prepared in this application has a large viscosity at room temperature. Therefore, this application first mixes the eutectic solvent and water, and then heats the mixture so that the heated eutectic solvent can be diluted with water to obtain eutectic solvent-water solution for later use. Step S3: Add 5g of wheat bran (the wheat bran is referred to as wheat bran raw material) to 100mL of the eutectic solvent-water solution prepared in step S2, heat in an 80℃ water bath for 120min, and continuously stir during the heating process at a stirring speed of 60rpm to obtain the processed material. Step S4: Cool the treated material to room temperature, then adjust the pH of the treated material to 7 with a sodium hydroxide solution with a molar concentration of 8 mol / L to obtain a liquid. Then add anhydrous ethanol to the liquid and let it stand for 1 hour to obtain a solution system. The amount of anhydrous ethanol added is the same as the volume of the liquid. Step S5: Filter the solution system to obtain a filter cake. Wash the filter cake twice with anhydrous ethanol, and then dry it in an oven at 60°C for 18 hours. Then grind the dried filter cake into powder using a mortar and pestle, and pass it through a 60-mesh sieve to obtain wheat bran with high soluble dietary fiber content.

[0023] Example 2:

[0024] The only difference between Example 2 and Example 1 is that in step S2 of Example 2, 10g of eutectic solvent and 90g of water are mixed and heated in a water bath for 30 minutes.

[0025] Example 3:

[0026] The only difference between Example 3 and Example 1 is that the water bath heating time in step S3 of Example 3 is 30 minutes.

[0027] Example 4:

[0028] The only difference between Example 4 and Example 1 is that in step S2 of Example 4, 30g of eutectic solvent and 70g of water are mixed and heated in a water bath for 30 minutes.

[0029] Example 5:

[0030] The only difference between Example 5 and Example 1 is that the water bath heating time in step S2 of Example 5 is 150 min.

[0031] Comparative Example 1: 5g of wheat bran was ground into powder using a mortar and pestle, and then passed through a 60-mesh sieve to obtain a wheat bran comparison sample. The wheat bran in Comparative Example 1 refers to the raw wheat bran, i.e., untreated wheat bran.

[0032] Comparative Example 2: Add 5g of wheat bran to 100mL of water and heat in an 80℃ water bath for 30min. Stir continuously during the heating process at a speed of 60rpm to obtain the processed material. The treated material was cooled to room temperature, and then anhydrous ethanol was added. The mixture was allowed to stand for 1 hour to obtain a solution system. The amount of anhydrous ethanol added was the same as the volume of the treated material. The solution system was filtered to obtain a filter cake. The filter cake was washed twice with anhydrous ethanol and then placed in an oven at 60°C to dry for 18 hours. The dried filter cake was then ground into powder using a mortar and pestle and passed through a 60-mesh sieve to obtain the wheat bran comparison sample.

[0033] Comparative Example 3: Add 5g of wheat bran to 100mL of 1% citric acid aqueous solution, heat in an 80℃ water bath for 30min, and stir continuously at a speed of 60rpm during the heating process to obtain the processed material. The treated material was cooled to room temperature, and then the pH of the treated material was adjusted to 7 with a sodium hydroxide solution with a molar concentration of 8 mol / L to obtain a liquid. Anhydrous ethanol was then added, and the mixture was allowed to stand for 1 hour to obtain a solution system. The amount of anhydrous ethanol added was the same as the volume of the liquid. The solution system was filtered to obtain a filter cake. The filter cake was washed twice with anhydrous ethanol and then placed in an oven at 60°C to dry for 18 hours. The dried filter cake was then ground into powder using a mortar and pestle and passed through a 60-mesh sieve to obtain the wheat bran comparison sample.

[0034] test:

[0035] (1) The soluble dietary fiber content and insoluble dietary fiber content in the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 5 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3 were determined. Taking the determination of the soluble and insoluble dietary fiber content in wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the steps include: First, 0.5g of wheat bran with high soluble dietary fiber content prepared in Example 1 was added to 2mL of sodium acetate buffer solution with a molar concentration of 2 mol / L and a pH of 4.5, and autoclaved for 1h at a temperature of 121℃ and a pressure of 0.1MPa. Then, 100 μL of high-temperature α-amylase solution was added, and the mixture was heated in a 95°C water bath for 30 min with constant stirring during heating to obtain the treatment solution. The high-temperature α-amylase solution was obtained by diluting 1.25 mL of high-temperature α-amylase reagent (enzyme activity of 20000 U / mL, CAS number 9001-19-8) with 0.1 mol / L phosphate buffer (pH 7.0) and bringing the volume to 50 mL to obtain the high-temperature α-amylase solution. Then, add 4 mL of a molar concentration of 2. The enzyme solution was prepared by first adding 0.075 mL of saccharifying enzyme reagent (enzyme activity 100,000 U / mL; CAS number 9032-08-0) to 0.1 mol / L phosphate buffer (pH 7.0) and then bringing the volume to 50 mL. The solution was then incubated at 55°C for 30 min to obtain the enzyme treatment solution. Next, 1 mol / L sodium hydroxide solution was added to the enzyme treatment solution to adjust the pH to 10. Finally, 20 μL of alkaline protease solution was added and the solution was incubated at 45°C for 30 min. The alkaline protease solution was prepared by adding 0.005 g of alkaline protease (enzyme activity 200 kJ / mL) to the alkaline protease solution. U / mg (CAS No. 9014-01-1), dissolved in 0.1 mol / L phosphate buffer (pH 7.0) and brought to a final volume of 50 mL to obtain an alkaline protease solution; then heated in a 100°C water bath for 10 min to inactivate the enzyme, followed by centrifugation for 20 min at 5500 rpm to obtain the supernatant. Anhydrous ethanol was added to the supernatant for 60 min of alcohol precipitation, with a supernatant to anhydrous ethanol volume ratio of 1:4; then filtered, and the filtrate was dried to obtain soluble dietary fiber, which was weighed and its mass recorded; the precipitate obtained by filtration was washed twice with water, twice with 80% ethanol, and twice with 95% ethanol, and filtered again, and the filtrate was dried to obtain insoluble dietary fiber, which was weighed and its mass recorded; Based on the mass of soluble dietary fiber, the mass of insoluble dietary fiber, and the mass (0.5g) of wheat bran with high soluble dietary fiber content prepared in Example 1, the percentage content of soluble dietary fiber (SDF) and the percentage content of insoluble dietary fiber (IDF) in the wheat bran with high soluble dietary fiber content prepared in Example 1 were calculated. The percentage content of total dietary fiber (TDF) in the wheat bran with high soluble dietary fiber content was obtained by summing the percentage content of soluble dietary fiber (SDF) and the percentage content of insoluble dietary fiber (IDF). The results are shown in Table 1.

[0036] The methods for determining the soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) content in the wheat bran prepared in Examples 2 to 5 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3 differ from the methods for determining the soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) content in the wheat bran prepared in Example 1. The only difference is that when testing the wheat bran prepared in Examples 2 to 5 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3, the test samples used are the wheat bran prepared in Examples 2 to 5 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3, respectively.

[0037] The results of determining the content of soluble dietary fiber (SDF), insoluble dietary fiber (IDF), and total dietary fiber (TDF) in the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 5 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3 are shown in Table 1.

[0038] Table 1

[0039] As shown in Table 1, the percentage content of soluble dietary fiber (SDF) in the wheat bran prepared in Examples 1 to 5 of this application ranges from 29.72% to 46.08%. Among them, the percentage content of soluble dietary fiber (SDF) in the wheat bran prepared in Example 5 is increased by (46.08% - 9.04%) / 9.04% × 100% = 409.7% compared with the percentage content of soluble dietary fiber (SDF) in the wheat bran prepared in Comparative Example 1. As can be seen from Table 1, the percentage content of insoluble dietary fiber (IDF) in the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 5 of this application decreased to 21.66% to 40.83%; among them, the percentage content of insoluble dietary fiber (IDF) in the wheat bran with high soluble dietary fiber content prepared in Example 5 decreased by (46.98%-21.66%) / 46.98%×100%=53.89% compared with the percentage content of insoluble dietary fiber (IDF) in the wheat bran control sample prepared in Comparative Example 1. The above results show that, compared with the wheat bran control sample prepared in Comparative Example 1, the percentage content of soluble dietary fiber in the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 5 of this application is significantly increased, while the percentage content of insoluble dietary fiber is significantly reduced. Moreover, as can be seen from Table 1, the percentage content of total dietary fiber in the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 5 is 67.74% to 70.56%, which is significantly higher than the percentage content of total dietary fiber of 56.02% ± 0.79% in the wheat bran control sample prepared in Comparative Example 1. Obviously, as can be seen from the above, the wheat bran with high soluble dietary fiber content prepared by the method described in this application not only significantly increases the percentage content of soluble dietary fiber, but also increases the percentage content of total dietary fiber. The increase in soluble dietary fiber may be due to the destruction of the wheat bran structure after processing by the method described in this application, releasing the soluble dietary fiber within the wheat bran structure. The process described in this application may also destroy insoluble dietary fiber, converting it into soluble dietary fiber. The increase in total dietary fiber may be due to the separation of certain components from the wheat bran raw material after processing by the method described in this application, resulting in wheat bran with high soluble dietary fiber content. In this case, the content of components other than soluble and insoluble dietary fiber in the wheat bran with high soluble dietary fiber content decreases, ultimately leading to a higher percentage content of total dietary fiber calculated based on the high soluble dietary fiber content.

[0040] (2) The microstructure of wheat bran with high soluble dietary fiber content prepared in Examples 1 to 5 and comparative samples prepared in Comparative Examples 1 to 3 were tested: Taking the microstructure test of the wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the following steps were included: a small amount of the wheat bran with high soluble dietary fiber content prepared in Example 1 was uniformly adhered onto a conductive adhesive, and then vacuum sputtered with gold. The microstructure was observed using a scanning electron microscope (GeminiSEM500; ZEISS; Germany) at an accelerating voltage of 5kV, and images were taken at 500× and 1000× magnification, respectively, as shown in the figures. Figure 4 and Figure 5 As shown; The method for testing the microstructure of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 5 and the comparative samples of wheat bran prepared in Comparative Examples 1 to 3 differs from the method for testing the microstructure of the wheat bran with high soluble dietary fiber content prepared in Example 1 only in the following aspects: (1) When testing the microstructure of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 5 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3, a small amount of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 5 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3 were dried, ground through a 60-mesh sieve, and uniformly adhered to the conductive adhesive. (2) Images are taken only at magnification of 500x; The results of testing the microstructure of the wheat bran comparative samples prepared in Comparative Examples 1 to 3 and the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 5 are as follows: Figures 1 to 3 as well as Figures 6 to 9 As shown.

[0041] from Figure 1 It can be seen that the wheat bran comparative sample prepared in Comparative Example 1 exhibits a lamellar structure, which is relatively dense and has wrinkles on the surface.

[0042] from Figure 2 It can be seen that the wheat bran comparison sample prepared in Comparative Example 2 also exhibits a lamellar structure with obvious wrinkles on the surface, and the lamellar structure is not significantly damaged. from Figure 3 It can be seen that the wheat bran control sample prepared in Comparative Example 3 no longer has a lamellar structure; the lamellar structure has been damaged, forming many small particles. from Figure 4 and Figure 5 The images shown at 500× and 1000× magnification reveal that the surface of the wheat bran prepared in Example 1, which is high in soluble dietary fiber, has formed dense pores and numerous small particles, significantly smaller than [the specified size]. Figure 3 The particle size of the small particles shown; and, from Figure 5 It can also be seen that the structure of the pores is loose and there are cracks. This may be because the method described in this application destroys the intermolecular cross-linking between insoluble dietary fibers such as cellulose, lignin and hemicellulose in the outer cell wall of wheat bran. The eutectic solvent can penetrate into the gaps between the wheat bran layers, dissolving some hemicellulose and starch components, which weakens the bonding between the wheat bran layers. At the same time, the swelling effect caused by the eutectic solvent will cause the layers to peel and loosen, which in turn will destroy the original dense layer structure of the wheat bran raw material and form a rich pore and porous structure.

[0043] from Figure 6 It can be seen that the wheat bran with high soluble dietary fiber content prepared in Example 5 is in the form of blocks and granules, and no longer has the original dense lamellar structure.

[0044] (3) Fourier transform infrared spectroscopy was performed on the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3: Taking the Fourier transform infrared spectroscopy (FTIR) determination of the wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the steps include: preparing a sample by using the KBr pelleting method with the wheat bran with high soluble dietary fiber content prepared in Example 1 and KBr, wherein the mass ratio of the wheat bran with high soluble dietary fiber content to KBr is 1:100; and then using a Fourier transform infrared spectroscopy instrument at 4000–500 cm⁻¹. -1 Scan within the range, with a resolution of 4cm. -1 The scan was performed 32 times, and the Fourier transform infrared spectrum of the wheat bran with high soluble dietary fiber content prepared in Example 1 was obtained, as shown below. Figure 10 As shown.

[0045] The method for testing the Fourier transform infrared spectra of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3 differs from the method for testing the Fourier transform infrared spectra of the wheat bran with high soluble dietary fiber content prepared in Example 1 only in that: when testing the Fourier transform infrared spectra of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3, small amounts of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparison samples prepared in Comparative Examples 1 to 3 were prepared using the KBr pelleting method. The results obtained by testing the Fourier transform infrared spectra of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3 are all as follows. Figure 10 As shown.

[0046] From Figure 10 It can also be seen that: compared with the wheat bran control samples prepared in Comparative Examples 1 to 3, the wheat bran prepared in Examples 1 to 4, which have a high soluble dietary fiber content, has a higher soluble dietary fiber content at 3200-3500 cm⁻¹. -1 The position and intensity of the characteristic peaks in the region have changed, specifically: The wheat bran control sample prepared in Comparative Example 1 was at 3200-3500 cm⁻¹ -1 The characteristic peak position is 3359cm. -1 Compared to the wheat bran control sample prepared in Comparative Example 1, the wheat bran prepared in Example 1, which has a higher soluble dietary fiber content, showed a higher content in 3200-3500 cm⁻¹. -1The characteristic peak position shifts to a lower wavenumber, while the transmittance at this site increases from 10% to 20%, and the absorbance (A) decreases from 1 to 0.699. The decrease in peak intensity is (1-0.699) / 1*100%=30.1%. In this application, the absorbance (A) is calculated as -log 10 （T） (Where T is transmittance); This indicates that the method described in this application significantly disrupts the hydrogen bonds in the wheat bran raw material, resulting in a significant reduction in the hydrogen bonds in the wheat bran with high soluble dietary fiber content prepared in this application compared to the hydrogen bonds in the wheat bran raw material. Since the intermolecular hydrogen bonding in this application is mainly manifested in the intermolecular cross-linking between insoluble dietary fibers such as cellulose, lignin, and hemicellulose in the outer cell wall of the wheat bran, the significant disruption of hydrogen bonds in the wheat bran raw material by the method described in this application will lead to the destruction of the lamellar structure of the wheat bran. The wheat bran control sample prepared in Comparative Example 1 was at 3200-3500 cm⁻¹ -1 The characteristic peak position is 3359cm. -1 Compared to the wheat bran control sample prepared in Comparative Example 1, the wheat bran prepared in Example 2, which has a higher soluble dietary fiber content, showed a higher content in 3200-3500 cm⁻¹. -1 The characteristic peak position shifts to a lower wavenumber; simultaneously, the transmittance at this site increases from 10% to 15%, and the absorbance (A) decreases from 1 to 0.824. The calculated rate of decrease in peak intensity is (1-0.824) / 1*100%=17.6%. The wheat bran control sample prepared in Comparative Example 1 was at 3200-3500 cm⁻¹ -1 The characteristic peak position is 3359cm. -1 Compared to the wheat bran control sample prepared in Comparative Example 1, the wheat bran prepared in Example 3, which has a higher soluble dietary fiber content, showed a higher content in 3200-3500 cm⁻¹. -1 The characteristic peak position shifts to lower wavenumbers at this location; simultaneously, the transmittance at this site increases from 10% to 19%, and the absorbance (A) decreases from 1 to 0.721, with a peak intensity reduction rate of (1-0.721) / 1*100%=27.9%. The wheat bran control sample prepared in Comparative Example 1 was at 3200-3500 cm⁻¹ -1 The characteristic peak position is 3359cm. -1 Compared to the wheat bran control sample prepared in Comparative Example 1, the wheat bran prepared in Example 4, which has a higher soluble dietary fiber content, showed a higher content in 3200-3500 cm⁻¹. -1 The characteristic peak position shifts to lower wavenumbers at this location; simultaneously, the transmittance at this site increases from 10% to 19%, and the absorbance (A) decreases from 1 to 0.721, with a peak intensity reduction rate of (1-0.721) / 1*100%=27.9%. From Figure 10 It can also be seen that the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4, and the wheat bran control samples prepared in Comparative Examples 1 to 3, have a 2921 cm⁻¹ content. -1 Weak absorption peaks appeared in the vicinity, corresponding to the CH stretching vibrations of methyl (-CH3) and methylene (-CH2-) groups in the polysaccharide polymer; moreover, by comparison, it was found that the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 had a peak at 2921 cm⁻¹. -1 The absorption peak intensity in the vicinity is significantly weaker than that of the wheat bran control samples prepared in Comparative Examples 1 to 3; specifically: The wheat bran control sample prepared in Comparative Example 1 was at 2921 cm⁻¹ -1 The transmittance at the characteristic peak site was 24.55%; compared with the wheat bran control sample prepared in Comparative Example 1, the wheat bran prepared in Example 1, which has a high soluble dietary fiber content, showed a transmittance of 2921 cm⁻¹. -1 The transmittance at the characteristic peak site increased from 24.55% to 34.47%, and the absorbance (A) decreased from 0.610 to 0.463, with a peak intensity reduction rate of (0.610-0.463) / 0.610*100%=24.09%; Example 2 sample at 2921 cm⁻¹ -1 The transmittance at the characteristic peak site increased from 24.55% to 28.82%, and the absorbance (A) decreased from 0.610 to 0.540, with a peak intensity reduction rate of (0.610-0.540) / 0.610*100%=11.48%; Example 3 sample at 2921 cm⁻¹ -1 The transmittance at the characteristic peak site increased from 24.55% to 36.73%, and the absorbance (A) decreased from 0.610 to 0.435, with a peak intensity reduction rate of (0.610-0.435) / 0.610*100%=28.69%; Example 4 sample at 2921 cm⁻¹ -1 The transmittance at the characteristic peak site increased from 24.55% to 32.74%, and the absorbance (A) decreased from 0.610 to 0.484, with a peak intensity reduction rate of (0.610-0.484) / 0.610*100%=20.66%. These results indicate that the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 of the method described in this application exhibits good transmittance at 2921 cm⁻¹. -1The intensity of the methylene CH stretching vibration peak at the point is significantly reduced. This may be related to the fact that the method described in this application can dissolve lipids or some small molecule polysaccharides in wheat bran raw materials and destroy the hydrogen bonds and the original cellulose crystal structure in wheat bran raw materials. Specifically, the dissolution of lipids or some small molecule polysaccharides in wheat bran raw materials will lead to fewer CH bonds in wheat bran with high soluble dietary fiber content, which will weaken the characteristic absorption of CH bonds and reduce the CH bond absorption peak. On the other hand, the destruction of hydrogen bonds and the original cellulose crystal structure in wheat bran raw materials will cause the CH bonds to change from an ordered and bound state to a disordered and loose state, the regularity of the group arrangement will decrease, the degree of restriction of CH bond vibration will decrease, and the intensity of the CH stretching vibration absorption peak will decrease. (4) The crystal structures of the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 and the comparative samples of wheat bran prepared in Comparative Examples 1 to 3 were determined: Taking the crystal structure test of wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the following steps are included: The wheat bran with high soluble dietary fiber content prepared in Example 1 is spread flat on a sample holder, and tested using an X-ray diffractometer (XRD). The radiation source is Cu-Kα (λ=0.15406nm), the scanning range is 2θ=5°–50°, the scanning speed is 2° / min, the tube voltage is 40kV, and the tube current is 30mA. The test results are as follows: Figure 11 As shown; The method for testing the crystal structure of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3 differs from the method for testing the crystal structure of the wheat bran with high soluble dietary fiber content prepared in Example 1 only in that: when testing the crystal structure of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3, a small amount of the wheat bran with high soluble dietary fiber content prepared in Examples 2 to 4 and the wheat bran comparative samples prepared in Comparative Examples 1 to 3 are laid flat on the sample rack. The results obtained by testing the crystal structures of the wheat bran samples with high soluble dietary fiber content prepared in Examples 2 to 4 and the comparative samples of wheat bran prepared in Comparative Examples 1 to 3 are all as follows. Figure 11 As shown.

[0047] from Figure 11It can be seen that the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4, as well as the wheat bran control samples prepared in Comparative Examples 1 to 3, all exhibit characteristic diffraction peaks of cellulose type I at 2θ≈20°. The crystallinity was determined using Origin, and the results are as follows: the crystallinity of the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 was 19.14%, 25.49%, 21.65%, and 20.18%, respectively; the crystallinity of the wheat bran control samples prepared in Comparative Examples 1 to 3 was 34.10%, 30.56%, and 18.53%, respectively. Moreover, compared with the wheat bran comparative sample prepared in Comparative Example 1, the crystallinity of the wheat bran with high soluble dietary fiber content prepared in Examples 1 to 4 was significantly reduced. This may be because the original cellulose crystal structure in the wheat bran raw material was destroyed and the degree of order decreased after the method described in this application was processed, resulting in a decrease in crystallinity.

[0048] (5) The sodium taurocholate adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Examples 1 and 5, as well as the wheat bran comparative sample prepared in Comparative Example 1, was determined in the same manner: Taking the determination of the sodium taurocholate adsorption capacity of wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the following steps are included: Add 0.1g of wheat bran (high in soluble dietary fiber prepared in Example 1), 0.02g of sodium taurocholate, and 10mL of 0.15mol / L sodium chloride solution to a 50mL centrifuge tube. Shake well and place in a 220rpm constant temperature water bath at 37℃ for 3h. Then centrifuge for 15min to obtain the supernatant at 10000rpm. Take 0.5mL of the supernatant and place it in a 25mL glass bottle. Then add 6mL of 45% sulfuric acid solution and 1mL of 0.3% furfural. Incubate at 65℃ for 1h to obtain the test sample. Then measure the absorbance of the test sample at 620nm. Then, according to the standard curve y=0.2286x+0.0613(R 2 =0.9931, where y represents absorbance and x represents sodium taurocholate concentration) to calculate the concentration of sodium taurocholate, and then calculate the adsorption amount of sodium taurocholate using formula (1): (1) In formula (1), C: sodium taurocholate concentration before adsorption; C1: sodium taurocholate concentration after adsorption; V: volume of sodium taurocholate aqueous solution; m: amount of wheat bran with high soluble dietary fiber content prepared in Example 1.

[0049] The adsorption capacity test results of taurine sodium on wheat bran with high soluble dietary fiber content prepared in Example 1 are as follows: Figure 12As shown, the results indicate that the adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Example 1 for sodium tauronate is significantly higher than that in Comparative Example 1. The adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Example 1 is 2.53 times that of the wheat bran prepared in Comparative Example 1. This is related to the dense porous structure of the wheat bran with high soluble dietary fiber content prepared in Example 1 of this application. The larger specific surface area of ​​the porous structure increases the number of contact sites for adsorption with the wheat bran with high soluble dietary fiber content, and also increases the exposure sites of active groups (such as carboxyl, hydroxyl, carbonyl, etc.). The increase in contact sites for adsorption enhances the adsorption and binding capacity of the wheat bran with high soluble dietary fiber content for sodium tauronate. The increase in the exposure sites of active groups (such as carboxyl, hydroxyl, carbonyl, etc.) allows more active groups to interact with sodium tauronate molecules, further improving the adsorption effect.

[0050] And from Figure 12 It can also be seen that the adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Example 5 for sodium tauronate decreased by 5.24% compared with Example 1. This may be due to the excessively long treatment time of the wheat bran with the eutectic solvent, which caused greater damage to the wheat bran raw material and destroyed its pore structure. The destruction of the pore structure leads to a decrease in the specific surface area of ​​the wheat bran with high soluble dietary fiber content, and the exposure sites of active groups (such as carboxyl, hydroxyl, carbonyl, etc.) are reduced accordingly. Ultimately, the adsorption effect of the wheat bran with high soluble dietary fiber content prepared in Example 5 on sodium tauronate is not as good as that of the wheat bran with high soluble dietary fiber content prepared in Example 1.

[0051] (6) The cholesterol adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Examples 1 and 5, as well as the comparative sample of wheat bran prepared in Comparative Example 1, was determined using the same test method: Taking the determination of cholesterol adsorption capacity of wheat bran with high soluble dietary fiber content prepared in Example 1 as an example, the following steps are included: Add 0.1g of the wheat bran with high soluble dietary fiber content prepared in Example 1 to a 50mL centrifuge tube, then add 10mL of cholesterol solution with a mass concentration of 1mg / mL, shake well, place in a 37℃ water bath for 1h, and then centrifuge at a speed of 4000rpm for 15min to obtain the precipitate. Then, add 1 mL of extraction solution (isopropanol was used as the extraction solution) to the precipitate, homogenize in an ice bath, and then centrifuge at 10,000 rpm for 15 min. Then, take 0.5 mL of the supernatant and determine the cholesterol content according to the determination method of the Beijing Solarbio Total Cholesterol Assay Kit.

[0052] The cholesterol adsorption capacity of the wheat bran with high soluble dietary fiber content prepared in Example 1 and the comparative sample of wheat bran prepared in Comparative Example 1 were measured, as shown in the following results. Figure 12 As shown.

[0053] from Figure 12 It can be seen that the adsorption capacity (μmol / g) of cholesterol by the wheat bran prepared in Example 1 is 11.53% higher than that of the wheat bran prepared in Comparative Example 1. This is related to the dense porous structure and high soluble dietary fiber content of the wheat bran prepared in Example 1 of this application. Soluble dietary fiber contains a large number of polar groups such as hydroxyl and carboxyl groups. The increased soluble dietary fiber content in the wheat bran prepared in Example 1 results in more polar groups such as hydroxyl and carboxyl groups in the wheat bran. These polar groups will bind to cholesterol through hydrogen bonds, hydrophobic interactions, and electrostatic adsorption. The larger specific surface area of ​​the porous structure will also have a physical interception and encapsulation effect on cholesterol, thus enabling the wheat bran prepared in Example 1 with high soluble dietary fiber content to have a better adsorption effect on cholesterol.

[0054] And from Figure 12 It can also be seen that the adsorption capacity (μmol / g) of cholesterol by the wheat bran with high soluble dietary fiber content prepared in Example 5 decreased by 6.6% compared with Example 1. This may be because the wheat bran was treated with a low eutectic solvent for too long, which caused greater damage to the wheat bran raw material and destroyed its pore structure. The destruction of the pore structure leads to a decrease in the specific surface area of ​​the wheat bran with high soluble dietary fiber content, and the exposure sites of active groups (such as carboxyl, hydroxyl, carbonyl, etc.) are reduced accordingly. Moreover, the destruction of the pore structure weakens the physical interception and encapsulation effect of the wheat bran with high soluble dietary fiber content on cholesterol. Ultimately, the adsorption effect of the wheat bran with high soluble dietary fiber content prepared in Example 5 on sodium taurocholate is not as good as that of the wheat bran with high soluble dietary fiber content prepared in Example 1 on sodium taurocholate.

Claims

1. A type of wheat bran with high soluble dietary fiber content, characterized in that: The percentage content of soluble dietary fiber in the wheat bran with high soluble dietary fiber content is 29.72% to 46.08%, and the percentage content of total dietary fiber is 67.75% to 70.56%.

2. A method for preparing wheat bran with high soluble dietary fiber content, characterized in that: The wheat bran with high soluble dietary fiber content is the wheat bran with high soluble dietary fiber content as described in claim 1; the preparation method of the wheat bran with high soluble dietary fiber content includes the following steps: S1. Preparation of eutectic solvent; S2. Prepare a diluted eutectic solvent-water solution using a eutectic solvent and water; S3. Add wheat bran to a eutectic solvent-water solution, stir and heat to obtain the treated material; S4. Cool the treated material to room temperature, adjust the pH, add solvent A, and let it stand to obtain the solution system; S5. Filter the solution system to obtain a filter cake. Wash the filter cake and then dry, grind and sieve it to obtain wheat bran with high soluble dietary fiber content.

3. The method for preparing wheat bran with high soluble dietary fiber content according to claim 2, characterized in that: Step S1 includes the following steps: choline chloride, citric acid, and glycerol are mixed, heated to 75-85°C under stirring, and stirred at a constant temperature of 75-85°C for 100-150 minutes at a stirring speed of 55-65 rpm; then naturally cooled to room temperature to obtain a eutectic solvent.

4. The method for preparing wheat bran with high soluble dietary fiber content according to claim 3, characterized in that: In step S1, the mass ratio of choline chloride, citric acid, and glycerol is (3.2–3.8):(9.3–9.9):(6.6–7.2).

5. The method for preparing wheat bran with high soluble dietary fiber content according to claim 2, characterized in that: Step S2 includes the following steps: mixing a eutectic solvent and water, and heating in a water bath at 75–85°C for 4–6 minutes to obtain a eutectic solvent-water solution.

6. The method for preparing wheat bran with high soluble dietary fiber content according to claim 5, characterized in that: In step S2, the mass ratio of the eutectic solvent to water is (10-30):(70-90).

7. The method for preparing wheat bran with high soluble dietary fiber content according to claim 2, characterized in that: Step S3 includes the following steps: adding wheat bran to a eutectic solvent-water solution, heating in a water bath at 75-85°C for 30-150 minutes, stirring continuously during the heating process at a speed of 55-65 rpm, to obtain the processed material.

8. The method for preparing wheat bran with high soluble dietary fiber content according to claim 7, characterized in that: In step S3, the mass-to-volume ratio of wheat bran to eutectic solvent-water solution is (4-6) g:(80-120) mL.

9. The method for preparing wheat bran with high soluble dietary fiber content according to claim 2, characterized in that: Step S4 includes the following steps: cooling the treated material to room temperature, adjusting the pH of the treated material to 6.5-7.5 with sodium hydroxide solution to obtain a liquid, then adding solvent A to the liquid and letting it stand for 1-1.5 hours to obtain a solution system.

10. The method for preparing wheat bran with high soluble dietary fiber content according to claim 9, characterized in that: In step S4, the volume of anhydrous ethanol is the same as the volume of the feed liquid.

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