Method for extracting oryzanol from rice bran oil

Abstract

The invention belongs to a natural oryzanol extraction and separation technology, and particularly discloses a method for extracting oryzanol from rice bran oil. The method comprises the following steps: mixing and dissolving a rice bran oil soap base and methanol according to a mass ratio of 1: (8-10), supplementing methanol to 10-12 times of the total liquid amount, and adjusting the pH value to 8.8-9.3 for saponification; after primary extraction, adding fresh methanol for secondary extraction, filtering, adjusting the pH value to 6.5-6.7, carrying out acidification crystallization, and centrifuging to obtain a crude oryzanol product A; and decolorizing and purifying with hot water, and carrying out secondary acidification with citric acid to finally obtain the high-purity oryzanol. The extraction method provided by the invention simultaneously reduces the use amount of acid and alkali and wastewater discharge, and has the advantages of being green, environment-friendly, low in cost and suitable for industrial production. And an efficient technical scheme is provided for high-value utilization of rice bran resources.

Description

Technical Field

[0001] This invention pertains to the extraction and separation technology of natural oryzanol, specifically relating to a method for extracting oryzanol from rice bran oil. Background Technology

[0002] γ-Oryzanol is a phytosterol compound naturally found in rice bran oil. It is primarily composed of a mixture of sterol ferulic acid and sterols, forming sterol ferulic acid esters and triterpenoid ferulic acid esters. Its unique chemical structure endows it with a wide range of biological activities, including regulating autonomic nerve function, lowering blood lipids, anti-oxidation, anti-inflammation, and improving sleep. Clinically, γ-Oryzanol has been used to treat autonomic nervous system dysfunction, menopausal syndrome, primary dysmenorrhea, periodic neuropathy, and cardiovascular diseases. Furthermore, its potential applications in the food and cosmetic fields are gradually emerging, for example, by reducing capillary fragility, improving skin microcirculation, and alleviating menopausal skin laxity and dandruff.

[0003] As the world's largest rice producer, my country's rice output exceeded 200 million tons in 2024, with an annual rice bran production of approximately 14 million tons, providing an ample raw material base for oryzanol extraction. However, the current comprehensive utilization rate of rice bran resources is less than 30%, with most rice bran being directly used as animal feed or subjected to low-value processing, resulting in the waste of high-value-added components such as oryzanol. Therefore, developing efficient and environmentally friendly oryzanol extraction technologies is of great significance for increasing the added value of the rice bran industry and promoting resource recycling.

[0004] Rice bran oil is a major source of oryzanol, with a content reaching 20-50 mg / g, significantly higher than other vegetable oils. However, there are two major technical challenges in the processing of rice bran oil: High acid value issue: Rice bran contains highly active lipases, resulting in a generally high acid value in crude oil (10-50 mg KOH / g). High acid value accelerates the hydrolysis of oryzanol, reducing the extraction rate. Although traditional alkali refining methods can effectively remove acid, oryzanol is easily converted to sodium salt under alkaline conditions and adsorbed by soap residue, leading to a loss rate as high as 60%.

[0005] Degradation of heat-sensitive substances: Oryzanol is sensitive to temperature. High-temperature distillation or prolonged heating can cause structural degradation, affecting product purity and activity. For example, traditional distillation methods require operation at 220-250℃, which easily leads to oxidation of oryzanol.

[0006] Currently, oryzanol extraction technologies are mainly divided into the following categories, but all of them have obvious drawbacks: Saponification-acid precipitation method: Process flow: Rice bran oil is alkali-refined to enrich oryzanol into soapstock, and then oryzanol is extracted by saponification with methanol alkali solution and weak acid re-precipitation. Disadvantages: The loss rate of oryzanol during the alkali refining process reaches 30%-50%, and a large amount of acid and alkali reagents are required, generating saline wastewater and causing serious environmental pollution.

[0007] Solvent extraction method: Process flow: Oryzanol in rice bran oil is directly extracted using non-polar solvents (such as n-hexane and benzene).

[0008] Disadvantages: Solvent recovery is energy-intensive and it is difficult to completely remove impurities such as wax, resulting in a product purity of less than 60%.

[0009] Molecular distillation: Process flow: Separate oryzanol and fatty acids through vacuum distillation. Disadvantages: High equipment investment, low throughput (only 0.1-0.5 kg / h), making it difficult to apply industrially.

[0010] Supercritical fluid extraction: Process flow: Selective extraction of oryzanol using supercritical CO2. Disadvantages: High operating pressure (30-50 MPa), low solids throughput (<5 kg / h), and cost is 3-5 times that of traditional methods.

[0011] In recent years, oryzanol extraction technology has developed towards "green, efficient, and low-cost" directions. The main trends include: a combined low-alkali refining and physical deacidification process: reducing oryzanol loss by controlling the acid value during alkali refining (retaining more than 6 mg KOH / g), and further lowering the acid value by combining it with distillation deacidification. For example, a two-stage deacidification method can increase the oryzanol retention rate to 85% and the product purity to 2.06%.

[0012] Despite some progress in existing technologies, the following problems still exist: A contradiction between purity and yield: High-purity extraction (such as column chromatography) is usually accompanied by low yields (<50%), while high-yield processes (such as solvent extraction) produce products with insufficient purity. Insufficient comprehensive utilization of resources: Oryzanol in rice bran oil processing byproducts (such as soapstock and deodorized distillates) is not fully recovered, leading to resource waste.

[0013] Therefore, developing a high-yield, high-purity, low-cost, and environmentally friendly oryzanol extraction technology is of great significance for enhancing the competitiveness of the rice bran industry and meeting the needs of the pharmaceutical and food sectors. This study aims to address existing technological bottlenecks by optimizing the alkali refining-extraction-crystallization combined process, providing a new technical solution for the large-scale production of oryzanol. Summary of the Invention

[0014] To solve the above-mentioned technical problems, this invention optimizes the extraction solvent and extraction process of rice bran oil soap base, and screens out a green and environmentally friendly method for extracting oryzanol with a high extraction rate.

[0015] This invention provides a method for extracting oryzanol from rice bran oil, comprising the following steps: S1. Dissolving: Mix rice bran oil soap base with methanol at a mass ratio of 1:8-10 and stir to dissolve; S2, Saponification: Add methanol to 10-12 times the total liquid volume, heat to 65-70℃, adjust pH to 8.8-9.3, and keep warm while stirring for 30-50 minutes; S3, single extraction: after standing and separating the layers, separate the lower layer of oryzanol methanol solution; S4. Secondary extraction: Add fresh methanol to the primary extract, wherein the volume ratio of the primary extract to methanol is 1:5. After stirring, allow the mixture to stand and separate into layers, and then filter to obtain the filtrate. S5. Acid precipitation crystallization: Adjust the pH of the filtrate to 6.5-6.7, raise the temperature to 60℃ and then gradually lower the temperature to crystallize, centrifuge to obtain crude oryzanol A; S6. Decolorization and purification: After washing crude product A with hot water, centrifuge to obtain crude oryzanol product B; S7. Secondary acid precipitation: Crude product B is dissolved in methanol, and citric acid is added dropwise until pH=6.0-6.2. After crystallization, the product is centrifuged and washed to obtain oryzanol.

[0016] Furthermore, in the method, the mass ratio of methanol to rice bran oil soap base in the dissolution step is 1:8, and the stirring speed is 80-100 r / min.

[0017] Furthermore, in the method, the pH is adjusted by sodium hydroxide methanol solution during the saponification step, the temperature is 65-70℃, and the holding time is 30-50 min.

[0018] Furthermore, in the method, the acid precipitation crystallization is carried out by adjusting the pH to 6.5-6.7 with hydrochloric acid, and the crystallization cooling rate is 3-5℃ / h.

[0019] Furthermore, in the method, the secondary acid precipitation uses citric acid to adjust the pH to 6.0-6.2, and the crystallization temperature is 55℃ for 1 hour and then cooled to 30℃.

[0020] Furthermore, in the method, the water temperature in the hot water decolorization step is 95℃, and the number of washing cycles is ≥2.

[0021] Furthermore, in the method, the extraction rate of oryzanol is 10.05%-12.09%.

[0022] Finally, oryzanol prepared by the method described in this invention is also provided.

[0023] (1) High extraction rate and high purity: Through secondary extraction + segmented acid precipitation process, the extraction rate of oryzanol is increased to 12.09% (the traditional method is only 5% to 6%), which overcomes the defect of low yield of existing technology.

[0024] Green and environmentally friendly: Methanol is used instead of benzene solvents to reduce the use of toxic reagents; hot water decolorization is used instead of organic solvent washing to reduce the difficulty of wastewater treatment.

[0025] Industrial feasibility: The process parameters (such as temperature 65-70℃ and pH precise control) are easy to scale up, with a processing capacity of 300-500 kg / batch, making it suitable for large-scale production.

[0026] High resource utilization rate: Effective use of rice bran oil soap base reduces waste of by-products and meets the requirements of circular economy. Attached Figure Description

[0027] Figure 1 This is a process flow diagram. Detailed Implementation

[0028] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[0029] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

[0030] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0031] Example 1 This example demonstrates the extraction of oryzanol from rice bran oil soap base.

[0032] 1.1 Dissolving Add methanol to the dissolving tank at a ratio of 1:8 (by mass), start stirring (80 rpm), and slowly add 300 kg of rice bran oil soap base to the dissolving tank, controlling the feeding rate to ≤50 kg / min to avoid localized overheating. After the feeding is complete, continue stirring for 30 minutes until completely dissolved.

[0033] 1.2 Saponification The material in the dissolving tank is piped into the saponification tank, and methanol is added to 10 times the total liquid volume. Steam heating is started and the temperature is raised to 65°C. The mixture is kept at this temperature and stirred at 60 rpm for 50 minutes. A sample is taken to test the pH value, which is controlled between 8 and 8.

[0034] 1.3 Single Extraction The dissolved soap-based methanol solution is pumped into an extraction tank and allowed to stand for 1 hour to separate into layers. The lower layer is a oryzanol methanol solution, and the upper layer is an impurity layer. The lower layer solution is separated into an intermediate tank, and the impurity layer is discharged into the waste liquid treatment system.

[0035] 1.4 Secondary Extraction 1.4.1 The lower layer of oryzanol methanol solution was separated and added to fresh methanol at a ratio of 1:5 (volume ratio). The mixture was pumped into the extraction tank, stirred at 100 r / min for 40 min, and then allowed to stand for 2 h to separate into layers.

[0036] 1.4.2 The separated lower layer of oryzanol methanol solution is filtered through a filter (pore size ≤ 5 μm) to remove insoluble matter, and the filtrate is transferred to a crystallization tank.

[0037] 1.5 Acid precipitation crystallization 1.5.1 The filtered oryzanol methanol solution was pumped into a crystallization tank, and the stirring was started at 50 r / min. 30% hydrochloric acid solution was slowly added dropwise until the pH reached 6.5-6.7, while the temperature was raised to 60℃ and held for 30 min. Then the temperature was lowered to 40℃ at a rate of 5℃ / h and allowed to stand for crystallization for 12 h.

[0038] 1.5.2 The oryzanol methanol suspension obtained by acid precipitation crystallization was transferred to a centrifuge and centrifuged at 3000 r / min for 15 min to collect crude oryzanol product A.

[0039] 1.5.3 After acid precipitation and centrifugation, crude oryzanol A was transferred to a decolorization tank. Hot water at 95℃ was added at a ratio of 1:10 (mass ratio), and the mixture was stirred at 80 r / min for 30 min. After standing and separating into layers, the upper aqueous phase was discharged. The operation was repeated twice until the aqueous phase became clear.

[0040] 1.5.4 Transfer the oryzanol suspension to a centrifuge and centrifuge for 10 min to collect crude oryzanol B.

[0041] 1.6 Extraction of crude oryzanol B 1.6.1 Add crude oryzanol B to a dissolving tank, add methanol at a ratio of 1:8 (mass ratio), heat to 50°C and stir to dissolve for 30 minutes, then pump into an extraction tank.

[0042] 1.6.2 Turn on the extraction tank and stir (100 r / min) for 60 min, then let it stand for 3 h to separate into layers.

[0043] 1.6.3 The lower layer of oryzanol methanol solution after extraction is transferred to a storage tank.

[0044] 1.7 Crude oryzanol B crystallization by acid precipitation 1.7.1 The lower layer of oryzanol methanol solution after extraction was transferred to a crystallization tank. 20% citric acid solution was added dropwise with stirring until the pH reached 6.0. The temperature was raised to 55℃ and kept at that temperature for 1 hour. The temperature was then lowered to 30℃ at a rate of 3℃ / h and allowed to stand for crystallization for 8 hours.

[0045] 1.7.2 The oryzanol methanol solution that has been acid-precipitated and crystallized was transferred to a centrifuge and centrifuged for 20 min, and the filter cake was collected.

[0046] 1.7.3 Add drinking water (temperature 40℃) to the centrifuge and wash the filter cake 3 times. The amount of water used for each wash is twice the mass of the filter cake. After centrifugation, the chloride ion content is measured to be ≤50ppm.

[0047] 1.7.4 After collecting and weighing the crude oryzanol, it was placed into double-layered low-density polyethylene bags, sealed, and stored in a dry warehouse. It was labeled as #1 Oryzanol. The process flow of this embodiment is as follows: Figure 1 As shown.

[0048] Example 2 This example demonstrates the extraction of oryzanol from rice bran oil soap base.

[0049] 2.1 Dissolving Add methanol to the dissolving tank at a ratio of 1:10 (by mass), and start stirring (100 rpm). Slowly add 400 kg of rice bran oil soap base (8%-12% oryzanol content) to the dissolving tank, controlling the feeding rate to ≤50 kg / min to avoid local overheating. After the feeding is complete, continue stirring for 35 minutes until completely dissolved.

[0050] 2.2 Saponification Transfer the material from the dissolving tank into the saponification tank through a pipeline, add methanol to 12 times the total liquid volume, turn on steam heating to 68°C, and maintain the temperature while stirring (70 rpm) for 40 minutes. Take a sample to test the pH value, which should be controlled at 9.0.

[0051] 2.3 Single Extraction The dissolved soap-based methanol solution is pumped into an extraction tank and allowed to stand for 1.5 hours to separate into layers. The lower layer is a oryzanol methanol solution, and the upper layer is an impurity layer (containing phospholipids, colloids, etc.). The lower layer solution is separated into an intermediate tank, and the impurity layer is discharged into the waste liquid treatment system.

[0052] 2.4 Secondary Extraction 2.4.1 Add fresh methanol to the separated lower layer of oryzanol methanol solution at a ratio of 1:5 (volume ratio), pump it into the extraction tank, turn on the stirring (speed 100-120 r / min) for 30 min, and let it stand for 2 h to separate into layers.

[0053] 2.4.2 The separated lower layer of oryzanol methanol solution (containing oryzanol ≥20%) is filtered through a filter (pore size ≤5μm) to remove insoluble matter, and the filtrate is transferred to a crystallization tank.

[0054] 2.5 Acid precipitation crystallization 2.5.1 The filtered oryzanol methanol solution was pumped into a crystallization tank, and stirring was started (50-60 r / min). 30% hydrochloric acid solution was slowly added dropwise until the pH reached 6.5-6.7, while the temperature was raised to 60℃ and held for 30 min. Then the temperature was lowered to 40℃ at a rate of 5℃ / h, and crystallization was allowed to proceed for 12 h.

[0055] 2.5.2 The oryzanol methanol suspension obtained by acid precipitation crystallization was transferred to a centrifuge (3000 r / min) and centrifuged for 15 min to collect crude oryzanol product A (containing ≥60% oryzanol).

[0056] 2.5.3 After acid precipitation and centrifugation, crude oryzanol A was transferred to a decolorization tank, and 95℃ hot water was added at a ratio of 1:10 (mass ratio). The mixture was stirred (80 r / min) for 30 min, allowed to stand and separate into layers, and then the upper aqueous phase was discharged. The operation was repeated twice until the aqueous phase became clear.

[0057] 2.5.4 Transfer the oryzanol suspension to a centrifuge and centrifuge for 10 min to collect crude oryzanol B (containing ≥75% oryzanol).

[0058] 2.6 Extraction of crude oryzanol B 2.6.1 Add crude oryzanol B to a dissolving tank, add methanol at a ratio of 1:8 (mass ratio), heat to 50°C and stir to dissolve for 30 minutes, then pump into an extraction tank.

[0059] 2.6.2 Turn on the extraction tank and stir (100 r / min) for 60 min, then let it stand for 3 h to separate into layers.

[0060] 2.6.3 The lower layer of oryzanol methanol solution (containing ≥85% oryzanol) after extraction is transferred to a storage tank.

[0061] 2.7 Crude oryzanol B crystallization by acid precipitation 2.7.1 The lower layer of oryzanol methanol solution after extraction was transferred to a crystallization tank. 20% citric acid solution was added dropwise with stirring until the pH reached 6.0-6.2. The temperature was raised to 55℃ and kept at that temperature for 1 hour. The temperature was then lowered to 30℃ at a rate of 3℃ / h and allowed to stand for crystallization for 8 hours.

[0062] 2.7.2 The oryzanol methanol solution that has undergone acid precipitation crystallization is transferred to a centrifuge and centrifuged for 20 min, and the filter cake is collected.

[0063] 2.7.3 Add drinking water (temperature 40℃) to the centrifuge and wash the filter cake 3 times. The amount of water used for each wash is twice the mass of the filter cake. After centrifugation, the chloride ion content is measured to be ≤50ppm.

[0064] 2.7.4 After collecting and weighing the crude oryzanol, pack it into double-layered low-density polyethylene bags, seal them, and store them in a dry warehouse, labeling them as 2#oryzanol.

[0065] Example 3 This example demonstrates the extraction of oryzanol from rice bran oil soap base.

[0066] 3.1 Dissolving Add methanol to the dissolving tank at a ratio of 1:10 (by mass), start stirring (100 rpm), and slowly add 500 kg of rice bran oil soap base to the dissolving tank, controlling the feeding rate to ≤50 kg / min to avoid localized overheating. After the feeding is complete, continue stirring for 38 minutes until completely dissolved.

[0067] 3.2 Saponification Transfer the material from the dissolving tank into the saponification tank through a pipeline, add methanol to 12 times the total liquid volume, turn on steam heating to 70℃, maintain the temperature, stir at 80 rpm for 30 minutes. Take a sample to test the pH value, which should be controlled at 9.3. If it is too low, add 10% sodium hydroxide methanol solution to adjust it.

[0068] 3.3 Single Extraction The dissolved soap-based methanol solution is pumped into an extraction tank and allowed to stand for 1 hour to separate into layers. The lower layer is a oryzanol methanol solution (containing oryzanol ≥15%), and the upper layer is an impurity layer (containing phospholipids, colloids, etc.). The lower layer solution is separated into an intermediate tank, and the impurity layer is discharged into the waste liquid treatment system.

[0069] 3.4 Secondary Extraction 3.4.1 Add fresh methanol to the separated lower layer of oryzanol methanol solution at a ratio of 1:5 (volume ratio), pump it into the extraction tank, turn on the stirring (100-120 r / min) for 30 min, and let it stand for 2 h to separate into layers.

[0070] 3.4.2 The separated lower layer of oryzanol methanol solution (containing oryzanol ≥20%) is filtered through a filter (pore size ≤5μm) to remove insoluble matter, and the filtrate is transferred to a crystallization tank.

[0071] 3.5 Acid precipitation crystallization 3.5.1 The filtered oryzanol methanol solution was pumped into the crystallization tank, and stirring was started (50-60 r / min). 30% hydrochloric acid solution was slowly added dropwise until the pH reached 6.5-6.7, while the temperature was raised to 60℃ and held for 30 min. Then the temperature was lowered to 40℃ at a rate of 5℃ / h, and crystallization was allowed to proceed for 12 h.

[0072] 3.5.2 The oryzanol methanol suspension obtained by acid precipitation crystallization was transferred to a centrifuge (3000 r / min) and centrifuged for 15 min to collect crude oryzanol product A (containing ≥60% oryzanol).

[0073] 3.5.3 After acid precipitation and centrifugation, crude oryzanol A was transferred to a decolorization tank, and 95℃ hot water was added at a ratio of 1:10 (mass ratio). The mixture was stirred (80 r / min) for 30 min, allowed to stand and separate into layers, and then the upper aqueous phase was discharged. The operation was repeated twice until the aqueous phase became clear.

[0074] 3.5.4 Transfer the oryzanol suspension to a centrifuge and centrifuge for 10 min to collect crude oryzanol B (containing ≥75% oryzanol).

[0075] 3.6 Extraction of crude oryzanol B 3.6.1 Add crude oryzanol B to a dissolving tank, add methanol at a ratio of 1:8 (mass ratio), heat to 50°C and stir to dissolve for 30 minutes, then pump into an extraction tank.

[0076] 3.6.2 Turn on the extraction tank and stir (100 r / min) for 60 min, then let it stand for 3 h to separate into layers.

[0077] 3.6.3 The lower layer of oryzanol methanol solution (containing ≥85% oryzanol) after extraction is transferred to a storage tank.

[0078] 3.7 Crude oryzanol B crystallization by acid precipitation 3.7.1 The lower layer of oryzanol methanol solution after extraction was transferred to a crystallization tank. 20% citric acid solution was added dropwise with stirring until the pH reached 6.0-6.2. The temperature was raised to 55℃ and kept at that temperature for 1 hour. The temperature was then lowered to 30℃ at a rate of 3℃ / h and allowed to stand for crystallization for 8 hours.

[0079] 3.7.2 The oryzanol methanol solution that has been crystallized by acid precipitation is transferred to a centrifuge and centrifuged for 20 min, and the filter cake is collected.

[0080] 3.7.3 Add drinking water (temperature 40℃) to the centrifuge and wash the filter cake 3 times. The amount of water used for each wash is twice the mass of the filter cake. After centrifugation, the chloride ion content is measured to be ≤50ppm.

[0081] 3.7.4 After collecting and weighing the crude oryzanol, pack it into double-layered low-density polyethylene bags, seal them, and store them in a dry warehouse, labeling them as 3#oryzanol.

[0082] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that only one extraction was performed, while the other steps were the same. The extracted oryzanol was labeled as #1 contrast agent.

[0083] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that methanol was replaced with ethanol, while the other steps were the same. The extracted oryzanol was labeled as contrast agent #2.

[0084] Test Example 1 This test case is to determine the extraction rate of oryzanol extracted from Examples 1-3 and Comparative Examples 1-2. The extraction rate of oryzanol is calculated using the following formula, and the test results are shown in Table 1.

[0085] Oryzanol extraction rate (%) = (weight of oryzanol / weight of rice bran oil soap base) × 100 The difference between Comparative Example 1 and Example 1 is that only one extraction was performed, while the other steps were the same. The extracted oryzanol was labeled as #1 contrast agent.

[0086] Table 1. Extraction rate of oryzanol using different extraction processes

[0087] As shown in Table 1, the two-stage extraction significantly improves the extraction rate of oryzanol and reduces its loss. Methanol solvent is more suitable for the two-stage extraction process. The extraction efficiency of methanol as a solvent is nearly twice that of ethanol as a solvent, indicating that the extraction method of oryzanol provided by this invention is more efficient. In particular, in Example 2, the extraction rate of oryzanol is as high as 12.09%. In addition, the process of this invention is simple, environmentally friendly, and suitable for large-scale production.

[0088] As described above, the present invention can be well implemented. The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, all kinds of changes and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for extracting oryzanol from rice bran oil, characterized in that, Includes the following steps: S1. Dissolving: Mix rice bran oil soap base with methanol at a mass ratio of 1:8-10 and stir to dissolve; S2, Saponification: Add methanol to 10-12 times the total liquid volume, heat to 65-70℃, adjust pH to 8.8-9.3, and keep warm while stirring for 30-50 minutes; S3, single extraction: after standing and separating the layers, separate the lower layer of oryzanol methanol solution; S4. Secondary extraction: Add fresh methanol to the primary extract, wherein the volume ratio of the primary extract to methanol is 1:

5. After stirring, allow the mixture to stand and separate into layers, and then filter to obtain the filtrate. S5. Acid precipitation crystallization: Adjust the pH of the filtrate to 6.5-6.7, raise the temperature to 60℃ and then gradually lower the temperature to crystallize, centrifuge to obtain crude oryzanol A; S6. Decolorization and purification: After washing crude product A with hot water, centrifuge to obtain crude oryzanol product B; S7. Secondary acid precipitation: Crude product B is dissolved in methanol, and citric acid is added dropwise until pH=6.0-6.

2. After crystallization, the product is centrifuged and washed to obtain oryzanol.

2. The method according to claim 1, characterized in that, In the dissolution step, the mass ratio of methanol to rice bran oil soap base is 1:8, and the stirring speed is 80-100 r / min.

3. The method according to claim 1, characterized in that, In the saponification step, the pH is adjusted by sodium hydroxide methanol solution, the temperature is 65-70℃, and the holding time is 30-50 min.

4. The method according to claim 1, characterized in that, The acid precipitation crystallization process involves adjusting the pH to 6.5-6.7 with hydrochloric acid, and the crystallization cooling rate is 3-5℃ / h.

5. The method according to claim 1, characterized in that, The secondary acid precipitation involves adjusting the pH to 6.0-6.2 with citric acid, crystallizing at 55℃ for 1 hour, and then cooling to 30℃.

6. The method according to claim 1, characterized in that, In the hot water decolorization step, the water temperature is 95℃, and the number of washes is ≥2.

7. The method according to claim 1, characterized in that, The extraction rate of oryzanol is 10.05%-12.09%.

8. Oryzanol prepared by the method of any one of claims 1-7.

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