Highly swellable rice bran dietary fiber and method for preparing the same

Abstract

The application provides high-swellability rice bran dietary fiber and a preparation method thereof, and utilizes inulinase to mildly hydrolyze rice bran fiber, realizes mild dissociation of fiber bundles and exposure of natural active sites, and on this basis, in-situ assembly of zinc phytate on the surface and inside of the fiber is guided by endogenous and exogenous phytic acid to construct a dense and stable functional coating. The coating significantly improves the water holding capacity, swelling capacity and bound water capacity of the product through the synergistic effect of strong hydrophilic sites and multi-stage pores, and fundamentally solves the problems of slow water absorption and poor water retention of traditional products. The rice bran dietary fiber prepared by the application has high yield and high purity, and also has good storage stability and thermal stability, which widens the application prospect in high-standard food systems, and has important significance for extending the grain industry chain and improving the added value of by-products.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a highly swellable rice bran dietary fiber and its preparation method. Background Technology

[0002] As a leading global producer and processor of grains and oils, my country generates a vast amount of edible byproducts annually during the processing of staple grains and oils. These byproducts are rich in nutrients and bioactive substances, and have high value for edible development and utilization. However, the overall food conversion rate of grain and oil processing byproducts in my country is currently low, which not only causes loss and waste of grain resources but also brings corresponding environmental pressures, thus restricting the sustainability of the grain supply system to some extent.

[0003] As a fundamental source of human nutrition, grains often lose a significant amount of nutrients in byproducts during processing. Scientific analysis shows that grain and oil processing byproducts are rich in various unique nutrients and bioactive components with physiological regulatory functions. Rice bran, a major byproduct of rice processing, accounts for 64% of rice's nutritional composition and contains high-quality protein, fat, carbohydrates, vitamins, dietary fiber, and minerals, as well as functional components such as tocopherols and tocotrienols. Wheat bran, a byproduct of wheat processing, has a dietary fiber content as high as 35-50%, and also contains abundant protein, vitamins, minerals, and bioactive substances such as phenols, which have significant effects on promoting intestinal health and weight control. Achieving large-scale, high-value, and nutritionally sound utilization of these byproducts will effectively alleviate domestic grain and oil supply pressures, better meet the growing health consumption demands of residents, achieve a balance of economic, social, and ecological benefits, and provide crucial support for promoting grain conservation and loss reduction and addressing potential food crises.

[0004] my country has a huge annual rice production, and rice bran, generated during processing, accounts for about 10% of the weight of rice. While the total amount is considerable, its effective utilization rate is low. Traditional rice bran utilization is mostly limited to animal feed or simple processing. High-value-added conversion technologies, such as the preparation of dietary fiber, typically involve stabilization treatment to inhibit lipase activity, followed by component separation and modification through physical, chemical, or biological methods. Existing processes include alkaline extraction, enzymatic hydrolysis, and extrusion puffing, aiming to improve the yield of soluble dietary fiber, enhance its functional properties, and apply it as a nutritional fortifier in baked goods, beverages, and meat products to improve product texture and nutrition labeling. However, the current technology system has significant shortcomings: First, rice bran has a high lipid content and strong lipase activity, which easily leads to rancidity and high stabilization costs, potentially damaging heat-sensitive components. Second, existing extraction processes mostly use strong alkalis or high temperatures, which easily cause environmental pollution, damage to fiber structure, and loss of functional activity. At the same time, the yield of soluble dietary fiber is generally low, making it difficult to simultaneously achieve the desired product physicochemical properties (such as water-holding capacity and swelling power) and taste. Third, rice bran fiber often causes problems such as a rough texture and darkening of color in food applications, affecting the sensory quality of the final product. Therefore, there is an urgent need to develop green and efficient integrated stabilization and extraction modification technology, and to strengthen its application research in diversified food matrices, in order to overcome the technical and industrial bottlenecks from by-products to high-value food ingredients. Summary of the Invention

[0005] Technical Problem to be Solved: Addressing the aforementioned industry pain points and technical bottlenecks, the purpose of this invention is to provide a highly swellable rice bran dietary fiber and its preparation method. Through a synergistic process of inulinase pretreatment and in-situ coordination assembly of zinc phytate guided by endogenous phytic acid, the problems of structural damage, low product yield, low purity, and low water-holding capacity and swelling capacity associated with traditional preparation methods are solved. The highly swellable rice bran dietary fiber prepared by this invention possesses high water-holding capacity, high swelling power, high yield, and high purity, and exhibits excellent storage stability and high-temperature tolerance.

[0006] Technical solution: A method for preparing highly swellable rice bran dietary fiber, comprising the following steps:

[0007] S1. Rice bran is pulverized and sieved, then defatted with n-hexane, filtered, and dried to obtain defatted rice bran;

[0008] S2. Disperse defatted rice bran in tartaric acid-malic acid solution, stir and react, adjust pH to 5.0~5.5, add inulinase for enzymatic hydrolysis, after enzymatic hydrolysis, heat the reaction system to inactivate the enzyme, filter while hot, wash the filter cake several times with hot water until the washing liquid is neutral, collect the filter cake, and obtain rice bran fiber base material.

[0009] S3. Disperse rice bran fiber substrate in water, add phytic acid, adjust the pH to 3.5-4.0, stir at 55-60℃ and 200-300 rpm for 45-90 min, adjust the stirring speed to 400-500 rpm, add zinc lactate solution, and continue the reaction at 55-65℃ for 1.5-2.5 h. After the reaction is completed, immediately filter, wash the filter cake repeatedly with a large amount of hot water, freeze dry the filter cake under vacuum, crush and sieve to obtain highly swellable rice bran dietary fiber.

[0010] Preferably, the concentration of the tartaric acid-malic acid solution in step S2 is 2-5%.

[0011] Preferably, in step S2, the mass ratio of tartaric acid to malic acid in the tartaric acid-malic acid solution is 1:1 to 4.

[0012] Preferably, in step S2, the temperature of the stirring reaction is 50~60℃, the stirring speed is 300~400rpm, and the stirring time is 30~50min.

[0013] Preferably, the amount of inulinase added in step S2 is 0.5 to 2.0% of the mass of defatted rice bran.

[0014] Preferably, in step S3, the mass ratio of rice bran fiber base material to phytic acid is 1:0.05~0.1.

[0015] Preferably, the mass ratio of phytic acid to zinc lactate in step S3 is 1:1 to 1.5.

[0016] The highly swellable rice bran dietary fiber prepared by the above preparation method.

[0017] The application of the above-mentioned highly swellable rice bran dietary fiber in the preparation of beverages.

[0018] The above-mentioned beverages are solid beverages, liquid beverages, or yogurt.

[0019] The above-mentioned highly swellable rice bran dietary fiber is added to beverages at a rate of 2-5%.

[0020] Beneficial effects:

[0021] 1. This invention utilizes inulinase to specifically hydrolyze the bonds between fiber bundles, achieving gentle dissociation of the fiber bundles. This loosens the fiber bundles, creating pores and exposing natural active sites, avoiding structural damage, component destruction, and loss caused by traditional physicochemical methods. Based on this, a functional coating is constructed through in-situ assembly of zinc phytate guided by endogenous phytic acid. The pores created by enzymatic hydrolysis allow phytic acid molecules to diffuse in, achieving an inside-out coating rather than just surface coverage. The coating itself also provides effective weight gain and structural stability, while natural active sites, such as ferulic acid esterified on rice bran hemicellulose, have phenolic hydroxyl groups that can interact with Zn. 2+ Coordination can occur, and it can also be oxidized and cross-linked, increasing the bonding force between the zinc phytate network and the fiber substrate. This allows the final product to maintain high purity and high yield while improving water retention, swelling force, and water binding capacity. It solves the contradiction between yield and high performance that traditional processes struggle to balance. It also has the advantages of being a green process that requires no strong chemical reagents, consumes little energy, and is pollution-free.

[0022] 2. This invention constructs a multi-level porous system through the synergistic effect of enzymatic hydrolysis of the fiber matrix and a zinc phytate coating. Numerous uncoordinated phosphate groups and Zn²⁺ sites on the phytate molecules in the coating instantaneously bind water molecules through strong polar interactions (hydrogen bonds, ion-dipole, coordination bonds). The nanoscale pores within the coating convert water vapor into liquid water under low humidity conditions and lock it within the pores. After water absorption, the zinc phytate coordination network itself undergoes slight swelling, further expanding the pores and accommodating more water. This structure, through the synergistic effect of capillary cohesion and the strong hydrophilicity of the coordination sites, achieves a breakthrough improvement in water retention and swelling capacity, fundamentally improving the shortcomings of traditional products such as slow water absorption and poor water retention.

[0023] 3. Traditional rice bran processing focuses on removing anti-nutritional factors such as phytic acid, often resulting in the loss of functional components. This invention utilizes an acid replacement system to displace bound phytic acid (phytate), exposing it at the fiber interface. These natural anchor points, along with exogenous phytic acid, interact with Zn. 2+ Coordination occurs, forming a zinc phytate coating. Endogenous phytic acid, acting as a natural anchor point in the fiber, enhances the adhesion between the coating and the substrate. The zinc phytate structure, synergistically constructed with exogenous phytic acid, is more dense and uniform, improving the swelling capacity of the coordination network. In the zinc phytate coating, the phosphate groups of phytic acid have already coordinated with Zn... 2+ High coordination saturation causes phytic acid to lose its ability to chelate minerals in the intestine, fundamentally eliminating its anti-nutritional risk. This invention transforms the phytic acid that needs to be removed into a key structural unit of the process, not only eliminating the yield loss caused by removing phytic acid alone and fundamentally eliminating the anti-nutritional properties of phytic acid, but also realizing the high-value utilization of raw materials and improving raw material utilization rate and economy.

[0024] 4. The rice bran dietary fiber prepared by this invention is functionally stable after being stored at room temperature for 6 months, proving that its structure has good durability.

[0025] Its zinc phytate hybrid coating exhibits excellent thermal stability with minimal mass loss after heat treatment at 300°C. This enables it to withstand food systems involving heat processing, such as baked goods, hot beverage preparations, and high-temperature sterilized foods, providing a reliable functional ingredient for foods requiring heat treatment. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments:

[0027] The inulinase used in the following examples and comparative examples was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd., with an enzyme activity of 10,000 U / g; phytase was purchased from Xi'an Darwen Biotechnology Co., Ltd., with an enzyme activity of 2,000 U / g; α-amylase was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd., with an enzyme activity of 10,000 U / g; alkaline protease was purchased from Jiangsu Yuanzhiyuan Biotechnology Co., Ltd., with an enzyme activity of 50,000 U / g; Aspergillus niger was purchased from Shandong Changtai Biotechnology Co., Ltd.; EM bacteria were purchased from Jining Alida Bioengineering Co., Ltd.; Trichoderma reesei was purchased from Yiyuan Kangyuan Biotechnology Co., Ltd.; cellulase was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd., with an enzyme activity of 50,000 U / g; xylanase was purchased from Anhui Zhonghong Bioengineering Co., Ltd., with an enzyme activity of 50,000 U / g; and trypsin was purchased from Jiangsu Yuanzhiyuan Biotechnology Co., Ltd., with an enzyme activity of 50,000 U / g.

[0028] Example 1

[0029] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0030] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0031] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 2% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:1). Stir at 50℃ and 400 rpm for 45 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0032] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 3.75 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 55℃ and 200 rpm for 60 min.

[0033] S4. 3.8 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 55℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0034] Example 2

[0035] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0036] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0037] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 2% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:2). Stir at 55℃ and 300 rpm for 30 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 0.5 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0038] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 3.75 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 55℃ and 200 rpm for 60 min.

[0039] S4. 3.8 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 55℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0040] Example 3

[0041] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0042] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0043] S2. Take 100 g of defatted rice bran and disperse it in 2 L of a 3% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:1). Stir at 50℃ and 300 rpm for 30 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0044] S3. Disperse 50 g of rice bran fiber base material in 750 mL of deionized water, dissolve 2.5 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH of the system to 3.5 with 10% citric acid solution, and stir the reaction at 55℃ and 200 rpm for 60 min.

[0045] S4. 3.25 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 55℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0046] Example 4

[0047] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0048] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0049] S2. Take 100 g of defatted rice bran and disperse it in 2 L of a 4% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:2). Stir at 60℃ and 400 rpm for 40 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1.5 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0050] S3. Disperse 50 g of rice bran fiber base material in 750 mL of deionized water, dissolve 3 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH of the system to 3.5 with 10% citric acid solution, and stir the reaction at 60℃ and 300 rpm for 45 min.

[0051] S4. 4.2 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 55℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0052] Example 5

[0053] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0054] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0055] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 4% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:3). Stir at 60℃ and 400 rpm for 40 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0056] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 3.5 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 60℃ and 200 rpm for 80 min.

[0057] S4. 4.2 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 55℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0058] Example 6

[0059] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0060] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0061] S2. Take 100 g of defatted rice bran and disperse it in 2 L of a 5% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:1). Stir at 55℃ and 400 rpm for 50 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0062] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 3.75 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 58℃ and 200 rpm for 50 min.

[0063] S4. 3.8 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 500 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 60℃ for 2.5 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0064] Example 7

[0065] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0066] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0067] S2. Take 100 g of defatted rice bran and disperse it in 2 L of a 5% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:2). Stir at 50℃ and 400 rpm for 45 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 2 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0068] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 4 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 55℃ and 200 rpm for 60 min.

[0069] S4. 6 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 400 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 65℃ for 2 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0070] Example 8

[0071] This embodiment describes a method for preparing highly swellable rice bran dietary fiber, including the following steps:

[0072] S1. After screening, removing impurities, and crushing, rice bran is passed through a 100-mesh sieve, and n-hexane is added at a solid-liquid ratio of 1:8. The mixture is stirred at 50°C for 2 hours to remove fat. After filtration, it is dried in a ventilated place to obtain defatted rice bran.

[0073] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 3% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:2). Stir at 55℃ and 350 rpm for 50 min. Adjust the pH value to 5.0 with 1 mol / L NaOH. Add 1.5 g of inulinase and enzymatically hydrolyze at 50℃ for 4 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0074] S3. Take 50 g of rice bran fiber base material and disperse it in 750 mL of deionized water. Dissolve 4 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add it to the rice bran fiber base material dispersion, adjust the pH value of the system to 3.5 with 10% citric acid solution, and stir the reaction at 55℃ and 200 rpm for 70 min.

[0075] S4. 5.6 g of zinc lactate was dissolved in deionized water to prepare a zinc lactate solution. The rotation speed was adjusted to 450 rpm, and the zinc lactate solution was slowly and dropwise added to the reaction system. The reaction was continued at 60℃ for 2.5 h. After the reaction was completed, the mixture was immediately filtered. The filter cake was repeatedly washed with a large amount of 55℃ deionized water. The conductivity of the last washing liquid was tested with a conductivity meter. When the conductivity was ≤20 μS / cm, it was considered to be qualified for washing. The filter cake was then freeze-dried under vacuum to obtain highly swellable rice bran dietary fiber.

[0076] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows:

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 is that in this comparative example, the inulinase pretreatment is replaced by physical grinding, and the specific method includes the following steps:

[0079] S1. Same as Example 1 S1;

[0080] S2. Take 100 g of defatted rice bran and disperse it in 2 L of deionized water. Shear it at 50℃ and 10000 rpm for 45 min. Filter and collect the filter cake to obtain rice bran fiber base material.

[0081] S3~S4. Same as S3~S4 in Example 1.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that the inulinase pretreatment is replaced with chemical alkali treatment in this comparative example. The specific method includes the following steps:

[0084] S1. Same as Example 1 S1;

[0085] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 5% NaOH solution. Stir at 50℃ and 400 rpm for 45 min. After filtration, wash the filter cake several times with deionized water until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0086] S3~S4. Same as S3~S4 in Example 1.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 1 is that phytic acid is replaced with deionized water in this comparative example, while the other steps are the same as in Example 1.

[0089] Comparative Example 4

[0090] The difference between this comparative example and Example 1 is that zinc lactate is not added in this comparative example. After adding phytic acid and stirring the reaction, the mixture is directly filtered, washed, and dried. The remaining steps are the same as in Example 1.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 1 is that steps S3 and S4 are interchanged in this comparative example. The specific method includes the following steps:

[0093] S1~S2. Same as Example 1, S1~S2;

[0094] S3. Disperse 50 g of rice bran fiber base material in 750 mL of deionized water, adjust the pH of the system to 5.5 with 10% citric acid solution, dissolve 3.8 g of zinc lactate in deionized water to prepare zinc lactate solution, add zinc lactate solution to the system, react at 55℃ for 2 h, adjust the pH of the system to 3.5 with 10% citric acid solution, dissolve 3.75 g of phytic acid in deionized water to prepare phytic acid aqueous solution, add phytic acid aqueous solution to the system, stir and react at 55℃ and 200 rpm for 60 min;

[0095] S4. After the reaction is complete, filter the filter cake immediately and wash it repeatedly with a large amount of 55°C deionized water. Use a conductivity meter to test the final washing liquid. When its conductivity is ≤20 μS / cm, it is considered to be qualified for washing. After vacuum freeze-drying the filter cake, rice bran dietary fiber is obtained.

[0096] Comparative Example 6

[0097] The difference between this comparative example and Example 1 is that phytase is used to remove endogenous phytic acid from rice bran fiber in this comparative example. The specific method includes the following steps:

[0098] S1. Same as Example 1 S1;

[0099] S2. Take 100 g of defatted rice bran and disperse it in 2 L of 2% tartaric acid-malic acid mixed solution (the mass ratio of tartaric acid to malic acid is 1:1). Stir at 50℃ and 400 rpm for 45 min. Adjust the pH value to 5.0 with 1 mol / L NaOH, add 1 g of inulinase, and enzymatically hydrolyze at 50℃ for 4 h. Adjust the pH value to 5.5 with 1 mol / L NaOH, add 1.5 g of phytase, and enzymatically hydrolyze at 55℃ for 1 h. After the enzymatic hydrolysis is completed, raise the temperature of the reaction system to 90℃ and keep it for 15 min to completely inactivate the enzyme. Filter while hot and wash the filter cake several times with deionized water at 60℃ until the washing liquid is neutral. Collect the filter cake to obtain rice bran fiber base material.

[0100] S3~S4. Same as S3~S4 in Example 1.

[0101] Comparative Example 7

[0102] This comparative example demonstrates the preparation of rice bran dietary fiber using ultrasound-assisted enzymatic hydrolysis and microbial fermentation. The specific method includes the following steps:

[0103] S1. Crush rice bran through a 100-mesh sieve, add distilled water at a solid-liquid ratio of 1:8, heat, adjust pH to 5.5, stir at 50℃ for 3 h, filter to obtain supernatant and solid, wash the solid with water until neutral, add distilled water at a solid-liquid ratio of 1:9, adjust pH to 6.0, add 4% α-amylase by weight of rice bran, enzymatically hydrolyze at 75℃ and ultrasonic power 300 W for 3 h, filter after enzymatic hydrolysis, add 3 times the weight of distilled water to the filter residue, adjust pH to 8.0, add 2.5% alkaline protease by weight of rice bran, enzymatically hydrolyze at 55℃ and ultrasonic power 300 W for 1 h, inactivate enzyme after enzymatic hydrolysis, filter, add 4 times the weight of distilled water to the filter residue and rinse twice, collect the filter residue;

[0104] S2. By weight, take 9 parts zeolite, 4 parts calcium dihydrogen phosphate, 7 parts glucose, 13 parts wheat bran, 12 parts corn flour, 4 parts rapeseed cake, 12 parts wheat bran, 2.5 parts Aspergillus niger, 1.5 parts EM bacteria, and 1.5 parts Trichoderma reesei. Mix and stir evenly. Adjust the water content to 35% with an aqueous solution containing 2% molasses. Perform anaerobic fermentation at 30℃ for 8 days to prepare the starter culture.

[0105] S3. By weight, take 100 parts of filter residue, 4 parts of fermentation agent, 0.8 parts of cellulase and 0.7 parts of xylanase, mix them evenly, adjust the moisture to 40%, and anaerobic ferment at 30℃ for 2.5 days, stirring regularly.

[0106] S4. After fermentation, add 4 times the amount of water to the fermentation residue, add 4% (by weight) of cellulase from the fermentation residue, and perform enzymatic hydrolysis at 55℃ and 300 W for 25 min. After enzymatic hydrolysis, wash twice with water, filter to obtain the supernatant, combine it with the supernatant obtained in S1, add 2.5 times the volume of anhydrous ethanol, stir, let stand, filter, dry the filter cake, pulverize it, and pass it through an 80-mesh sieve to obtain rice bran dietary fiber.

[0107] Table 1. Yield of total dietary fiber and soluble dietary fiber

[0108]

[0109] As shown in Table 1, the total dietary fiber yield of Examples 1-8 of this invention was 63-66%, and the purity was 81.53-85.66%. Inulinase effectively loosened the fiber bundles and exposed active sites while minimizing destructive loss of the fiber skeleton. Comparative Example 1 (physical grinding) and Comparative Example 2 (chemical alkali treatment) directly resulted in reduced yield and purity, indicating that non-selective damage such as physical shearing and strong chemical corrosion caused excessive breakage and dissolution loss of the fiber body while opening the structure. Comparative Example 3 (without phytic acid) and Comparative Example 4 (without zinc lactate) did not form a complete functional coating, indicating that the dense zinc lactate network formed in these examples provided structural stability and protection for the fiber substrate, reducing material loss in subsequent processes. Comparative Example 5 (step exchange) showed a significant decrease in both yield and purity, indicating that adding Zn first... 2+ This leads to the preferential binding or precipitation of phytic acid with limited sites on the fiber surface, hindering the subsequent adsorption and diffusion of phytic acid molecules. Furthermore, it results in a loose and weakly bonded complex structure, making it prone to detachment and loss during subsequent washing, thus reducing the yield and purity of the final product. Comparative Example 6 (removal of endogenous phytic acid) showed yields and purity close to the examples, but slightly lower. This indicates that endogenous phytic acid acts as an anchor point guiding the formation of the zinc phytate network. After acid replacement exposure, endogenous phytic acid provides sites for chemical bonding with the coating from within the fiber, enhancing the adhesion and uniformity of the coating to the substrate. After its removal, the coating bonding relies mainly on surface interactions, weakening its stability and potentially leading to slight detachment during vigorous washing or drying, thus having a slight negative impact on yield and purity. Comparative Example 7 (other processes), using ultrasound-assisted enzymatic hydrolysis and fermentation, achieved the highest yield and purity of total dietary fiber among all comparative examples, but still lower than the examples.

[0110] Table 2 Physicochemical properties of rice bran dietary fiber

[0111]

[0112] As shown in Table 2, Examples 1-8 of this invention achieved mild dissociation of fiber bundles and generation of nanopores by pretreating rice bran fiber with inulinase. Furthermore, through an in-situ coordination reaction of zinc phytate guided by endogenous phytic acid, an inorganic-organic hybrid coating rich in nanopores was constructed on the fiber surface and within the pores, thus forming a hierarchical pore system. Micrometer-level pores are provided by the rice bran fiber itself, primarily functioning to rapidly transport water. Nanometer-level pores are provided by the nanopores within the coating, converting water vapor into liquid water and locking it within the pores under low humidity conditions, effectively capturing and locking water molecules. Molecular-level pores are provided by the zinc phytate coating; after water absorption, the zinc phytate coordination network itself undergoes slight swelling, further expanding the pores and accommodating more water. Ultimately, the prepared highly swellable rice bran dietary fiber achieved water-holding capacity, swelling capacity, and water-binding capacity of 10.59-14.62 g / g, 8.94-9.86 mL / g, and 10.07-12.31 mL / g, respectively. g / g, achieving a synergistic breakthrough in three key functions. Comparative Example 1 (physical grinding) resulted in fiber structure damage, excessive powdering, and pore blockage, failing to generate uniform nanopores to support the zinc phytate coating. Therefore, the hierarchical pore system was incomplete, significantly weakening both rapid water transport (micrometer) and capillary water retention (nanometer) functions. Comparative Example 2 (chemical alkali treatment), while opening the fiber structure, severely damaged the fiber skeleton and active sites, leading to subsequent coatings failing to bond firmly and failing to form uniformly sized nanopores, resulting in poor functionality. Comparative Example 3 (no phytate added) showed only slight performance improvement due to insufficient total endogenous phytate, failing to form a complete functional network. Comparative Example 4 (no zinc lactate added) failed to form a hydrophilic network, resulting in the most complete loss of function. Comparative Example 5 (step exchange) failed to achieve ordered self-assembly, leading to a loose coating structure; the first added Zn... 2+ It will block pores and randomly precipitate, making it difficult for subsequent phytic acid to penetrate and coordinate evenly, resulting in an uneven surface and loosely bonded structure with an incomplete hierarchical pore system. Comparative Example 6 (removal of endogenous phytic acid) loses its natural molecular anchor points, and exogenous phytic acid can only act on the fiber surface through physical adsorption and hydrogen bonding. The coating adhesion and uniformity decrease, and it is easy to peel off from the substrate under swelling stress, thus weakening the water absorption and swelling effect. Comparative Example 7 (ultrasound-assisted enzymatic hydrolysis and fermentation) provides a better fiber matrix, but its functional properties are still inferior to those of the examples.

[0113] Table 3. Stability of Rice Bran Dietary Fiber

[0114]

[0115] As shown in Table 3, after 6 months of storage at room temperature, its water-holding capacity remained at a relatively high level of 9.61~13.35 g / g, indicating that its coating structure maintained good integrity during long-term storage without significant aging or dissociation. After heat treatment at 300℃, the mass loss rate was 12.44~15.67%. In summary, the highly swellable rice bran-based dietary fiber of this invention not only maintains its function during long-term storage but also withstands high-temperature processing conditions such as baking, making it suitable as a functional additive with heat-processing capabilities.

[0116] Example 9

[0117] This example demonstrates the application of highly swellable rice bran dietary fiber in the preparation of protein beverages. 8.5 g of the highly swellable rice bran dietary fiber prepared in Example 1 was added to a protein beverage and stirred evenly to obtain a rice bran dietary fiber beverage.

[0118] Example 10

[0119] The difference between this embodiment and embodiment 9 is that the high-swelling rice bran dietary fiber in this embodiment is the high-swelling rice bran dietary fiber prepared in embodiment 2.

[0120] Example 11

[0121] The difference between this embodiment and embodiment 9 is that the highly swollen rice bran dietary fiber in this embodiment is the highly swollen rice bran dietary fiber prepared in embodiment 3.

[0122] Example 12

[0123] The difference between this embodiment and embodiment 9 is that the high-swelling rice bran dietary fiber in this embodiment is the high-swelling rice bran dietary fiber prepared in embodiment 4.

[0124] Example 13

[0125] The difference between this embodiment and embodiment 9 is that the highly swollen rice bran dietary fiber in this embodiment is the highly swollen rice bran dietary fiber prepared in embodiment 5.

[0126] Example 14

[0127] The difference between this embodiment and embodiment 9 is that the highly swollen rice bran dietary fiber in this embodiment is the highly swollen rice bran dietary fiber prepared in embodiment 6.

[0128] Example 15

[0129] The difference between this embodiment and embodiment 9 is that the highly swollen rice bran dietary fiber in this embodiment is the highly swollen rice bran dietary fiber prepared in embodiment 7.

[0130] Example 16

[0131] The difference between this embodiment and embodiment 9 is that the highly swollen rice bran dietary fiber in this embodiment is the highly swollen rice bran dietary fiber prepared in embodiment 8.

[0132] Comparative Example 8

[0133] This comparative example is a protein beverage without added highly swollen rice bran dietary fiber.

[0134] Comparative Example 9

[0135] The difference between this comparative example and Example 9 is that the highly swollen rice bran dietary fiber in this comparative example is replaced with dietary fiber from celery residue. The specific steps include the following:

[0136] S1. Celery residue was treated with 0.7% α-amylase at 70℃ and pH 5.5 for 40 min, followed by enzyme inactivation at 90℃; 0.3% trypsin was added and treated with 50℃ and pH 8.0 for 40 min, followed by enzyme inactivation at 90℃; the residue was filtered, washed, dehydrated, and dried to obtain dietary fiber derived from celery residue.

[0137] S2. Take 8.5 g of dietary fiber from celery residue and add it to the protein beverage. Stir well to obtain a dietary fiber beverage.

[0138] Table 4 Quality of Protein Beverages

[0139]

[0140] As shown in Table 4, the protein beverages with added highly swellable rice bran dietary fiber in Examples 9-16 were superior to Comparative Example 1 (protein beverage without added dietary fiber) and Comparative Example 2 (dietary fiber derived from celery residue) in terms of centrifugal sedimentation rate and viscosity. The highly swellable rice bran dietary fiber prepared by this invention can effectively lock in water and effectively bind protein particles in the system, significantly reducing phase separation and precipitation caused by gravity, and improving the physical stability of the product. In terms of viscosity, its high swelling capacity avoids the roughness of ordinary fibers or the stickiness of colloids, providing a full and mellow taste.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing highly swellable rice bran dietary fiber, characterized in that, Includes the following steps: S1. Rice bran is pulverized and sieved, then defatted with n-hexane, filtered, and dried to obtain defatted rice bran; S2. Disperse defatted rice bran in tartaric acid-malic acid solution, stir and react, adjust pH to 5.0~5.5, add inulinase for enzymatic hydrolysis, after enzymatic hydrolysis, heat the reaction system to inactivate the enzyme, filter while hot, wash the filter cake several times with hot water until the washing liquid is neutral, collect the filter cake, and obtain rice bran fiber base material. S3. Disperse rice bran fiber substrate in water, add phytic acid, adjust the pH to 3.5-4.0, stir at 55-60℃ and 200-300 rpm for 45-90 min, adjust the stirring speed to 400-500 rpm, add zinc lactate solution, and continue the reaction at 55-65℃ for 1.5-2.5 h. After the reaction is completed, immediately filter, wash the filter cake repeatedly with a large amount of hot water, freeze-dry the filter cake under vacuum, pulverize and sieve to obtain highly swellable rice bran dietary fiber.

2. The preparation method according to claim 1, characterized in that: The concentration of the tartaric acid-malic acid solution in step S2 is 2-5%.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of tartaric acid to malic acid in the tartaric acid-malic acid solution is 1:1~4.

4. The preparation method according to claim 1, characterized in that: In step S2, the stirring reaction temperature is 50~60℃, the stirring speed is 300~400rpm, and the stirring reaction time is 30~50min.

5. The preparation method according to claim 1, characterized in that: In step S2, the amount of inulinase added is 0.5-2.0% of the mass of defatted rice bran.

6. The preparation method according to claim 1, characterized in that: In step S3, the mass ratio of rice bran fiber base material to phytic acid is 1:0.05~0.

1.

7. The preparation method according to claim 1, characterized in that: In step S3, the mass ratio of phytic acid to zinc lactate is 1:1 to 1.

5.

8. Highly swellable rice bran dietary fiber prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the highly swellable rice bran dietary fiber according to claim 8 in the preparation of beverages.

10. The application according to claim 9, characterized in that: The amount of highly swellable rice bran dietary fiber added to the beverage is 2-5%.

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