Rice oil with high active substance content and preparation method thereof

Abstract

The invention discloses rice oil with high active substance content and a preparation method thereof, and relates to the technical field of deep processing of edible oil, raw material refining pretreatment is carried out to guarantee material reaction suitability, a specific composite enzymatic hydrolysis system is adopted to directionally cut off characteristic chemical bonds of a binding state precursor under low-temperature, light-proof and oxygen-controlled conditions, and the active substance content of the rice oil is high. Active substrates such as free ferulic acid and free phytosterol are efficiently released; in an in-situ solid-phase system of the rice bran, directional conversion of a free substrate to fat-soluble oryzanol, sterol ferulate and high-activity tocotrienol is realized through synergistic catalysis of immobilized lipase and acyltransferase, multi-step separation and purification are not needed, a whole-process low-temperature mild oil extraction and low-loss precise refining process is matched, and the yield is high. And degradation and loss of active components are reduced to the maximum extent.

Description

Technical Field

[0001] This invention relates to the field of edible oil deep processing technology, specifically to a rice bran oil with high content of active substances and its preparation method. Background Technology

[0002] Rice bran oil is a special healthy edible oil made from rice bran, a byproduct of rice processing. It is rich in various fat-soluble bioactive substances such as oryzanol, phytosterols, and tocopherols / tocotrienols. Medical studies have confirmed that it has multiple physiological effects such as regulating blood lipids, anti-oxidation, anti-inflammation, improving autonomic nerve function, and aiding sleep. It is a recognized high-end functional edible oil, and market demand and product added value continue to increase.

[0003] Currently, the technological development of active substances in rice bran oil in the industry has always been limited to two traditional directions: one is the optimization of processes at the raw material and extraction ends, which maximizes the release of the inherent free active substances in rice bran raw materials and improves the extraction efficiency of active substances through technologies such as low-temperature stabilization of rice bran, low-temperature cold pressing, and subcritical / supercritical mild extraction; the other is the control of losses at the refining end, which reduces the degradation, saponification and distillation loss of active substances in each refining stage through processes such as enzymatic degumming, physical refining and low-temperature short-path deodorization, thereby improving the retention rate of active substances in the finished product.

[0004] However, the aforementioned existing technologies all revolve around the inherent free active substances in rice bran raw materials. The upper limit of the active substance content in the final product is entirely limited by the total amount of naturally occurring active substances in the rice bran raw materials, making it impossible to achieve a leapfrog increase in the total amount of active substances. At the same time, existing technologies completely ignore the large number of physiologically inactive or low-activity active substance precursors present in rice bran, including bound ferulic acid in the form of ferulic acid ester polysaccharides and ferulic acid ester lignin, bound sterols in the form of phytosterol glycosides, and tocopherol precursors, etc. In the existing processing technology, most of these precursors are lost with by-products such as degumming wastewater and oil pressing residue, and cannot be transformed into highly active fat-soluble functional components that can be enriched in oils. This not only causes a great waste of rice bran functional resources, but also fundamentally restricts the improvement of the active substance content and product quality of rice bran oil. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a rice bran oil with high content of active substances and its preparation method. This method ensures material compatibility through refined pretreatment of raw materials, employs a specific composite enzymatic hydrolysis system under low-temperature, light-protected, and oxygen-controlled conditions to directionally cleave the characteristic chemical bonds of bound precursors, efficiently releasing active substrates such as free ferulic acid and free phytosterols. In the rice bran in-situ solid-phase system, the synergistic catalysis of immobilized lipase and acyltransferase achieves the directional conversion of free substrates into fat-soluble oryzanol, sterol ferulic acid esters, and highly active tocotrienols, eliminating the need for multi-step separation and purification. Combined with a low-temperature, gentle oil extraction and low-loss, precise refining process, this method minimizes the degradation and loss of active components.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On one hand, a method for preparing rice bran oil with high content of active substances, the method comprising the following specific steps: S1: Take fresh rice bran raw material, first remove impurities by combination impurity removal, then perform low-temperature controllable pulverization, and then use atomization conditioning process to adjust the moisture content of the material. The whole process is carried out at low temperature and in the dark to obtain pre-treated uniform material. S2: Add a complex enzymatic hydrolysis system to the pretreated material. The complex enzymatic hydrolysis system includes ferulic acid esterase, glycosidase, and sterol glycosidase. The enzymatic hydrolysis reaction is carried out under low temperature and light-protected conditions to break the ester bond and glycosidic bond of the bound precursor, release free ferulic acid and free phytosterol, and obtain the enzymatically hydrolyzed material. S3: Adjust the water activity of the material after enzymatic hydrolysis, add an immobilized composite catalytic enzyme system, which includes immobilized lipase and immobilized acyltransferase, and carry out catalytic reaction in the rice bran in-situ solid phase system. Catalyze the directed esterification and transesterification reaction of free ferulic acid with phytosterols and glycerides to generate oryzanol monomer and sterol ferulic acid ester. At the same time, catalyze the cyclization and methylation modification of tocopherol precursors to convert them into tocotrienols, and obtain the catalytically hydrolyzed material. S4: Extract oil from the catalytically catalyzed material and then perform mild refining to obtain rice bran oil with high content of active substances.

[0007] Furthermore, in step S1, a 40-mesh vibrating screen is used to remove large rice husks and stone impurities, and then an air separation process is used to remove dust, shriveled grains, and other light impurities. After impurity removal, the mass percentage of impurities in the rice bran is ≤0.5%, avoiding impurities from affecting the contact efficiency between the enzyme and the substrate. The low-temperature controllable pulverization specifically involves using a low-temperature hammer mill for pulverization. During the pulverization process, the temperature is controlled by jacketed cooling water to keep the material temperature rise ≤5℃, avoiding rancidity caused by the activation of lipoxygenase in the rice bran. After pulverization, the material passes through a 40-80 mesh standard sieve, and the material remaining on the sieve is returned for secondary pulverization. The final particle size of the material is controlled at 40-80 mesh, ensuring a suitable specific surface area and improving the mass transfer efficiency of the subsequent enzymatic hydrolysis reaction. The atomization conditioning specifically involves using purified water for spray conditioning through a high-pressure atomizing nozzle, while simultaneously using a low-speed ribbon mixer to ensure uniform mixing of the material. After conditioning, the moisture content of the material is controlled at 20%-35%, and the coefficient of variation of moisture uniformity is ≤5%. The material temperature is controlled below 25℃ throughout the process, and the operation is carried out in the dark to avoid oxidation and degradation of active substances.

[0008] Furthermore, in S2, the amount of the compound enzymatic hydrolysis system added, based on the dry weight of rice bran, is: ferulic acid esterase 100-300 U / g, β-glucosidase 50-200 U / g, and sterol glycosylase 80-250 U / g. Ferulic acid esterase specifically cleaves the ester bonds between ferulic acid and polysaccharides and lignin, while β-glucosidase synergistically cleaves the glycosidic bonds between ferulic acid and sugars. The two work synergistically to enhance the release efficiency of bound ferulic acid. Sterol glycosylase specifically cleaves the glycosidic bonds between phytosterols and sugars, releasing free phytosterols. The compound enzymatic hydrolysis system is added using a pre-dilution method. The enzyme preparation is diluted into an enzyme solution using a citrate-sodium citrate buffer system and then added to the material via atomized spray. Simultaneous stirring ensures uniform dispersion of the enzyme in the material, avoiding uneven reactions caused by excessively high or low local enzyme concentrations.

[0009] Furthermore, in S2, the enzymatic hydrolysis process conditions are as follows: the pH value of the system is adjusted to 4.5-6.5 using a food-grade citric acid-sodium citrate buffer system, the reaction temperature is controlled at 30-45℃, the entire process is protected from light and purged with nitrogen or argon gas, and the reaction time is 6-16 hours.

[0010] Furthermore, in S2, the specific process conditions for the enzymatic hydrolysis reaction are as follows: Nitrogen gas with a purity ≥99.9% is continuously introduced into a sealed reaction vessel to replace the air inside the vessel, controlling the oxygen content to ≤0.5%. A slight positive pressure of 0.02-0.05 MPa is maintained throughout the process to isolate oxygen and prevent the oxidative degradation of active substances such as free ferulic acid and phytosterols. The reaction temperature is controlled at 30-45℃, using a jacketed low-temperature circulating water system to ensure the optimal reaction temperature of the enzyme and avoid enzyme inactivation and substrate degradation caused by high temperatures. Low-speed stirring is employed at 10-30 rpm, stirring for 5 minutes every 30 minutes to ensure sufficient contact between the material and the enzyme while avoiding material clumping and enzyme inactivation caused by high-speed stirring. The enzymatic hydrolysis reaction time is 6-16 hours, with the endpoint controlled at a free ferulic acid release rate ≥85% and a free phytosterol release rate ≥80%. After enzymatic hydrolysis, no high-temperature enzyme inactivation treatment is performed to avoid damaging the activity of the enzyme used for subsequent catalysis and to prevent the high-temperature degradation of released active substances.

[0011] Furthermore, in S3, the low-temperature humidity control conditioning specifically involves: placing the enzymatically hydrolyzed material in a sealed conditioning vessel, regulating the humidity of the system through low-temperature drying nitrogen circulation, controlling the material temperature to ≤40℃, gradually adjusting the water activity of the system to 0.2-0.4, and ensuring that the water activity deviation of the entire batch of material is ≤0.05; this water activity range can effectively inhibit the hydrolytic side reaction of lipase, maximize the directional conversion rate of esterification and transesterification reactions, and at the same time ensure the catalytic activity of the enzyme.

[0012] Furthermore, in S3, the amount of immobilized composite catalytic enzyme system added, based on the dry weight of rice bran, is: 150-300 U / g of immobilized lipase and 80-250 U / g of immobilized acyltransferase. The immobilized lipase catalyzes the main reactions of esterification and transesterification, while the immobilized acyltransferase enhances the directional selectivity of the transesterification reaction and reduces side reactions. Together, they synergistically improve the conversion rate of the target product. During addition, low-speed stirring is used, with a stirring speed of 10-20 rpm, to ensure uniform mixing of the enzyme and materials and avoid breakage of the immobilized carrier caused by high-speed stirring.

[0013] Furthermore, in S3, the carriers for the immobilized lipase and immobilized acyltransferase are porous carriers including food-grade macroporous adsorption resin and diatomaceous earth, and the immobilized enzymes can be recycled and reused.

[0014] Furthermore, in S3, the specific process conditions for the catalytic reaction are as follows: Nitrogen gas with a purity ≥99.9% is continuously introduced into a sealed reactor, controlling the oxygen content within the reactor to ≤0.5%, maintaining a slight positive pressure of 0.02-0.05 MPa throughout the process, operating in the dark to isolate oxygen and light, and preventing the oxidation and degradation of active substances and products; controlling the reaction temperature to 35-50℃, using a jacketed low-temperature circulating water system for precise temperature control, with temperature fluctuations ≤±1℃ to ensure the optimal catalytic temperature for the immobilized enzyme; employing low-speed stirring at 10-20 rpm, stirring for 10 minutes every 1 hour to ensure sufficient contact between the material and the immobilized enzyme, while preventing breakage of the immobilized enzyme carrier; the catalytic reaction time is 8-24 hours, with the reaction endpoint controlled at a oryzanol production of ≥5 mg / g (dry rice bran basis) and a sterol ferulic acid ester production of ≥0.8 mg / g (dry rice bran basis); after the reaction is completed, the material is sieved using a 20-mesh vibrating screen to separate and recover the immobilized enzyme carrier, which can be reused after washing with buffer solution.

[0015] Furthermore, in step S4, the low-temperature and mild oil extraction process employs any one of low-temperature cold pressing, subcritical butane extraction, or supercritical CO2 extraction, using low-temperature and mild conditions throughout to avoid high-temperature degradation of active substances and maximize the enrichment of the fat-soluble active components generated during the transformation. The specific process is as follows: Low-temperature cold pressing: The catalytic material is first pre-pressed and shaped to control the thickness of the cake to 3-5cm. Then it is fed into a twin-screw low-temperature cold press. The pressing chamber temperature is controlled to be ≤50℃ throughout the process, the pressing chamber pressure is 30-40MPa, and the cake thickness is ≤5mm. The crude oil obtained by pressing is filtered through a 200-mesh plate and frame filter to remove cake debris, and cold-pressed crude oil is obtained. Subcritical butane extraction: The catalytically treated material is loaded into an extraction vessel, and food-grade butane is used as the extraction solvent. The material-to-liquid ratio is controlled at 1:3-1:5 (g:mL), the extraction temperature is 35-45℃, the extraction pressure is 0.4-0.6MPa, the extraction time is 1-2h, and the extraction is performed 2-3 times. After extraction, the mixed oil is evaporated to separate the solvent. The evaporation temperature is controlled at ≤45℃, the vacuum degree is controlled at ≥0.08MPa, and the solvent residue is controlled at ≤50mg / kg to obtain subcritical extracted crude oil. Supercritical CO2 extraction: The catalytically treated material is loaded into the extraction vessel, and CO2 is used as the extraction medium. The extraction temperature is controlled at 35-50℃, the extraction pressure at 25-35MPa, the CO2 flow rate at 20-30L / h, and the extraction time at 2-4h. The separation vessel is controlled at 40-45℃ and 5-8MPa to separate crude oil, thus obtaining supercritical extracted crude oil.

[0016] Furthermore, in step S4, the entire process of low-loss refining employs a gentle process to avoid the loss and degradation of active substances. The specific process for each step is as follows: Enzymatic degumming: Crude oil is fed into a degumming reactor and heated to 35-45℃. Purified water (0.5%-2% by weight of oil) is added and stirred until homogeneous. The pH of the system is adjusted to 4.5-5.0 with citric acid. Food-grade phospholipase A1 or phospholipase C is added at a rate of 0.01%-0.03% by weight of oil, and the mixture is stirred for 2-4 hours. After the reaction is complete, the temperature is raised to 80℃ to inactivate the enzyme for 10 minutes. The mixture is then fed into a disc centrifuge at 6000-8000 rpm to remove gum impurities, yielding degummed oil. This process avoids the loss of active substances with wastewater caused by conventional hydration degumming. The phospholipid content in the degummed oil is ≤50mg / kg, providing qualified raw materials for subsequent refining. Short-path physical deacidification: The degummed oil is fed into a scraped-film short-path distillation device for physical deacidification. The distillation heating temperature is controlled at 160-190℃, the vacuum degree is ≤0.5Pa, the feed rate is 10-20L / h, the scraper speed is 100-150rpm, and the condensation temperature is 40-50℃. Through the high vacuum and short residence time characteristics of short-path distillation, free fatty acids are efficiently removed, completely avoiding the loss of a large amount of active substances due to saponification caused by traditional alkali refining deacidification. The acid value of the oil after deacidification is ≤0.2mgKOH / g. Vacuum-cooled mild decolorization: The deacidified oil is fed into a decolorization reactor and heated to 80-100℃ under a vacuum of ≥0.09MPa. 1%-3% (by weight) of a composite adsorbent is added. This composite adsorbent is a mixture of food-grade activated clay and powdered activated carbon in a mass ratio of 8:1-10:1. The mixture is stirred and adsorbed for 20-40 minutes. After adsorption, the adsorbent is removed by filtration through a 300-mesh plate and frame filter under nitrogen protection to obtain the decolorized oil. This process uses low temperature and low adsorbent dosage, and operates under vacuum conditions, avoiding the oxidative degradation of active substances caused by high-temperature atmospheric pressure decolorization. After decolorization, the oil has a Lovibond colorimetric index (25.4mm cell) of Y≤10 and R≤1.0, meeting the color requirements of the finished product. Low-temperature short-path deodorization: The decolorized oil is fed into a packed short-path deodorization tower for deodorization under high vacuum and low temperature conditions. The vacuum degree inside the tower is controlled to be ≤0.1Pa, the oil temperature is 210-230℃, and direct steam is introduced at a rate of 0.5%-1% of the oil weight. The deodorization residence time is 15-30 minutes. The high vacuum reduces the deodorization temperature, and the short residence time reduces the thermal degradation of active substances, significantly reducing the thermal decomposition and distillation loss of active substances such as oryzanol and phytosterols. After deodorization, the oil is rapidly cooled to below 40℃ under nitrogen protection throughout the process to obtain deodorized oil. The peroxide value of the deodorized oil is ≤0.1g / 100g, and the odor and taste meet national standards. Post-processing of finished product: The deodorized oil is filtered through a precision filter with a precision of 5μm under nitrogen protection to remove trace impurities. Then, it is filled with nitrogen to control the headspace oxygen content in the filling container to ≤1%, so as to obtain rice bran oil with high active substance content and ensure the stability of the product during storage.

[0017] On the other hand, a rice bran oil with a high content of active substances, wherein the rice bran oil contains ≥5.2 mg / g of oryzanol, ≥5.6 mg / g of phytosterols, ≥0.9 mg / g of tocotrienols, and ≥0.8 mg / g of sterol ferulic acid esters.

[0018] Compared with existing technologies, this rice bran oil with high content of active substances and its preparation method have the following beneficial effects: This invention transforms inactive / low-activity bound precursors in rice bran, which are originally lost with byproducts, into highly active fat-soluble functional components that can be enriched in oils. This fundamentally breaks through the ceiling of the inherent total amount of active substances in rice bran raw materials, and achieves a leapfrog increase in the content of core active substances in rice oil.

[0019] This invention precisely screens specific composite enzymatic hydrolysis systems and immobilized composite catalytic systems based on the molecular structural characteristics of different precursors: the composite enzymatic hydrolysis system can precisely cleave target chemical bonds, achieving efficient dissociation of bound precursors and high substrate release rate; the immobilized composite catalytic system can directionally catalyze target esterification, transesterification, and modification reactions with fewer side reactions and high conversion rate of target products, while avoiding the generation of byproducts caused by non-specific reactions, thus ensuring the edible safety and product quality of rice bran oil.

[0020] This invention uses food-grade carriers to immobilize lipases and acyltransferases. The immobilized enzymes have good stability, and after the catalytic reaction is completed, they can be quickly separated from the materials by simple sieving. The recovered immobilized enzymes can be reused after simple cleaning, which greatly reduces the cost of enzyme preparations and solves the industry pain points of high cost and inability to be industrialized for free enzyme preparations.

[0021] This invention generates high-purity oryzanol monomer, sterol ferulic acid ester with stronger fat solubility and antioxidant activity, and tocotrienol with antioxidant activity far exceeding that of ordinary tocopherols through targeted conversion. This enriches the types of active substances in rice bran oil, greatly improves the physiological activity and bioavailability of the product, and significantly enhances the added value and market competitiveness of rice bran oil.

[0022] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0024] Figure 1 A flowchart illustrating a method for preparing rice bran oil with high content of active substances; Figure 2 This is a flowchart of a rice bran oil with high content of active substances and its preparation method, step S4. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0026] Example 1 The method for preparing rice bran oil with high content of active substances in this embodiment is as follows: Figure 1 As shown, the specific steps are as follows: S1: Fresh rice bran raw material is first passed through a 40-mesh vibrating screen to remove large particles of impurities, and then through air separation to remove dust, shriveled grains, and light impurities. After impurity removal, the impurity content of the rice bran is 0.32%. A low-temperature hammer mill is used for crushing, with jacket cooling water temperature control to ensure that the material temperature rise is ≤3℃. After crushing, the material is passed through a 60-mesh standard sieve, and the material on the sieve is returned for secondary crushing. The final material particle size is concentrated at 60 mesh. Subsequently, a high-pressure atomizing nozzle is used for spray conditioning, while a ribbon agitator is used at a speed of 20 rpm. Purified water is added to adjust the material moisture content to 28%. After conditioning, the coefficient of variation of the material moisture uniformity is 3.2%. The material temperature is controlled below 22℃ throughout the process, and the operation is carried out in the dark to obtain pre-treated uniform material.

[0027] S2: The pretreated material is fed into a closed enzymatic hydrolysis reactor, and a 0.15 mol / L citrate-sodium citrate buffer system is added to adjust the pH of the material system to 5.2. Then, a pre-diluted compound enzymatic hydrolysis system is added, with 180 U / g ferulic acid esterase, 100 U / g β-glucosidase, and 120 U / g sterol glycosidase added based on the dry weight of rice bran. The enzyme solution is added via atomized spray while simultaneously stirring at low speed to ensure uniform dispersion. The reactor is then sealed and purified with pure... The air inside the reactor was replaced with 99.99% nitrogen to control the oxygen content to ≤0.3%, and a slight positive pressure of 0.03MPa was maintained throughout the process, while avoiding light. The reaction temperature was controlled at 38℃ using a jacketed low-temperature circulating water system. The reactor was stirred by turning the material at 20 rpm for 5 minutes every 30 minutes. After 10 hours of enzymatic hydrolysis, the release rates of free ferulic acid and free phytosterols were measured to be 89.2% and 85.7%, respectively. No enzyme inactivation treatment was performed after the enzymatic hydrolysis, resulting in the obtained solid phase material.

[0028] S3: The enzymatically hydrolyzed solid material is fed into a sealed conditioning vessel. The humidity of the system is regulated by low-temperature drying and nitrogen circulation, maintaining the material temperature at ≤38℃. The water activity of the system is adjusted to 0.3, with a water activity deviation of ≤0.03 for the entire batch. Then, an immobilized composite catalytic enzyme system is added. Based on dry rice bran weight, the immobilized lipase dosage is 220 U / g, and the immobilized acyltransferase dosage is 150 U / g. The immobilized enzyme carrier is food-grade macroporous adsorption resin with a particle size of 30 mesh. The enzyme activity recovery rates are 78.5% and 75.2%, respectively. The mixture is stirred at 15 rpm for 10 minutes to ensure uniform mixing of the enzyme and material. The vessel is then sealed. The reactor was purged with 99.99% pure nitrogen gas to control the oxygen content inside the reactor to ≤0.3%, and maintained at a slight positive pressure of 0.03MPa throughout the process, operating in the dark. A jacketed circulating water system was used to control the reaction temperature at 42℃, with temperature fluctuations ≤±1℃. The reactor was stirred by turning the material at 15 rpm for 10 minutes every 1 hour. After 15 hours of catalytic reaction, the yield of oryzanol was measured to be 5.92 mg / g (dry rice bran basis), and the yield of sterol ferulic acid ester was 0.95 mg / g (dry rice bran basis). After the reaction was completed, the material was sieved using a 20-mesh vibrating screen to separate and recover the immobilized enzyme carrier. After washing with buffer solution, the catalytically prepared material was obtained.

[0029] S4: As Figure 2As shown, the catalytically catalyzed material was pre-pressed into cakes 4 cm thick and fed into a twin-screw low-temperature cold press. The pressing chamber temperature was controlled at ≤45℃ throughout the process, the pressing chamber pressure at 35MPa, and the cake thickness at 4mm. The crude oil obtained from pressing was filtered through a 200-mesh plate and frame filter to remove cake debris, yielding cold-pressed crude oil. The cold-pressed crude oil was then fed into a degumming reactor and heated to 40℃. 1% purified water by weight of the oil was added, and the mixture was stirred evenly. The pH of the system was adjusted to 4.8 with citric acid, and phospholipase A1 was added at 0.02% of the oil weight. The mixture was stirred and reacted for 3 hours. After the reaction was completed, the temperature was raised to 80℃ to inactivate the enzyme for 10 minutes. The mixture was then fed into a disc centrifuge at 7000 rpm to remove gum impurities, yielding degummed oil. The phospholipid content in the degummed oil was measured to be 32 mg / kg. The degummed oil was then fed into a scraped-film short-path distillation apparatus, with the distillation heating temperature controlled at 180℃, the vacuum degree at 0.1Pa, the feed rate at 15L / h, and the scraper speed at 120 rpm. The deacidified oil was obtained by condensing at 45℃ and testing, with an acid value of 0.15 mg KOH / g. The deacidified oil was then fed into a decolorizing reactor and heated to 90℃ under a vacuum of 0.095 MPa. 2% (by weight) of a composite adsorbent (activated clay: activated carbon = 9:1) was added, and the mixture was stirred and adsorbed for 30 minutes. After adsorption, the adsorbent was removed by a 300-mesh plate and frame filter under nitrogen protection, yielding decolorized oil. This decolorized oil was then fed into a packed-bed short-path deodorization tower, with the vacuum controlled at 0.05 Pa and the oil temperature at 220℃. 0.8% (by weight) of direct steam was introduced, and the deodorization residence time was 20 minutes. After deodorization, the oil was rapidly cooled to below 35℃ under nitrogen protection throughout the process, yielding deodorized oil. The deodorized oil was then filtered through a 5μm precision filter under nitrogen protection, followed by nitrogen-filled bottling, with the headspace oxygen content in the bottling bottles controlled to ≤0.8%, resulting in a high-activity rice bran oil product.

[0030] Example 2 The method for preparing rice bran oil with high content of active substances in this embodiment includes the following specific steps: S1: Fresh rice bran raw material is taken, and after combined impurity removal, the impurity content is 0.35%; it is crushed using a low-temperature hammer mill, and the material temperature rise is controlled to be ≤4℃. After crushing, the material is passed through a 40-mesh standard sieve, and the final material particle size is concentrated at 40 mesh; high-pressure atomization conditioning is used to adjust the material moisture content to 32%, the moisture uniformity variation coefficient is 3.8%, the material temperature is ≤23℃ throughout the process, and the operation is carried out in the dark to obtain pre-treated material.

[0031] S2: Add a 0.2 mol / L citric acid-sodium citrate buffer system to the pretreated material and adjust the pH of the system to 5.5; add a compound enzymatic hydrolysis system, based on the dry weight of rice bran, with 250 U / g ferulic acid esterase, 150 U / g β-glucosidase, and 200 U / g sterol glycosidase, added by atomization and stirred evenly; seal the reactor, replace the air with nitrogen, maintain an oxygen content ≤0.3%, maintain a slight positive pressure of 0.03 MPa, and avoid light; control the reaction temperature at 35℃, turn and stir, and perform enzymatic hydrolysis for 14 hours; after testing, the release rate of free ferulic acid is 92.5%, and the release rate of free phytosterols is 88.3%. No enzyme inactivation treatment is performed to obtain the enzymatically hydrolyzed material.

[0032] S3: The enzymatically hydrolyzed material was subjected to low-temperature and humidity-controlled conditioning to adjust the water activity to 0.35 and the material temperature to ≤38℃. An immobilized composite catalytic enzyme system was added, with 280 U / g of immobilized lipase and 200 U / g of immobilized acyltransferase based on dry rice bran weight. The immobilized enzyme carrier had a particle size of 30 mesh, and the enzyme activity recovery rates were 77.2% and 76.1%, respectively. After stirring and mixing evenly, nitrogen gas was purged to protect the reaction, and the reaction temperature was controlled at 40℃ for 20 hours. The catalytic reaction was detected to produce 6.31 mg / g of oryzanol (dry rice bran weight) and 1.02 mg / g of sterol ferulic acid ester (dry rice bran weight). After the reaction was completed, the immobilized enzyme was recovered by sieving, and the catalytically treated material was obtained.

[0033] S4: The catalytically treated material was loaded into an extraction vessel, and food-grade butane was used as the extraction solvent. The material-to-liquid ratio was controlled at 1:4 (g:mL), the extraction temperature at 40℃, the extraction pressure at 0.5MPa, the extraction time at 1.5h, and the extraction was performed 3 times. After extraction, the mixed oil was evaporated to separate the solvent. The evaporation temperature was controlled at ≤42℃ and the vacuum degree at 0.09MPa to obtain crude extracted oil with a solvent residue of 28mg / kg. The same enzymatic degumming process as in Example 1 was used to obtain degummed oil with a phospholipid content of 28mg / kg. The same short-path distillation process as in Example 1 was used to obtain deacidified oil with an acid value of 0.12mgKOH / g. The same decolorization process as in Example 1 was used to obtain decolorized oil. The same deodorization process as in Example 1 was used to obtain deodorized oil. The same post-processing process as in Example 1 was used to obtain rice bran oil with a high content of active substances.

[0034] Example 3 The method for preparing rice bran oil with high content of active substances in this embodiment includes the following specific steps: S1: Fresh rice bran raw material is taken, and the impurity content is 0.41% after combined impurity removal; it is crushed by low temperature hammer mill, and the material temperature rise is controlled to be ≤3℃. After crushing, the material is passed through an 80-mesh standard sieve, and the final material particle size is concentrated at 80 mesh; high pressure atomization conditioning is used to adjust the material moisture content to 22% by mass, the moisture uniformity variation coefficient is 4.1%, the material temperature is ≤22℃ throughout the process, and the operation is carried out in the dark to obtain pre-treated material.

[0035] S2: Add a 0.1 mol / L citric acid-sodium citrate buffer system to the pretreated material and adjust the pH of the system to 4.8; add a compound enzymatic hydrolysis system, based on the dry weight of rice bran, containing 120 U / g ferulic acid esterase, 70 U / g β-glucosidase, and 90 U / g sterol glycosidase, atomized and stirred evenly; seal the reactor, purge the air with nitrogen to maintain an oxygen content ≤0.4%, maintain a slight positive pressure of 0.02 MPa, and protect from light; control the reaction temperature at 42℃, turn and stir, and perform enzymatic hydrolysis for 8 hours; after testing, the release rate of free ferulic acid is 86.1%, and the release rate of free phytosterols is 81.2%. No enzyme inactivation treatment is performed to obtain the enzymatically hydrolyzed material.

[0036] S3: The enzymatically hydrolyzed material was subjected to low-temperature and humidity-controlled conditioning to adjust the water activity to 0.25 and the material temperature to ≤38℃. An immobilized composite catalytic enzyme system was added, with 180 U / g of immobilized lipase and 100 U / g of immobilized acyltransferase based on dry rice bran weight. The immobilized enzyme carrier had a particle size of 30 mesh. After stirring and mixing evenly, nitrogen gas was purged to protect the reaction, and the reaction temperature was controlled at 45℃ for 10 hours. The reaction was tested and found to produce 5.28 mg / g of oryzanol (dry rice bran weight) and 0.83 mg / g of sterol ferulic acid ester (dry rice bran weight). After the reaction was completed, the immobilized enzyme was recovered by sieving to obtain the catalytically treated material.

[0037] S4: Using the same low-temperature cold-pressing process as in Example 1, cold-pressed crude oil was obtained; using the same enzymatic degumming process as in Example 1, degummed oil was obtained with a phospholipid content of 35 mg / kg; using the same short-path distillation process as in Example 1, deacidified oil was obtained with an acid value of 0.16 mg KOH / g; using the same decolorization process as in Example 1, decolorized oil was obtained; using the same deodorization process as in Example 1, deodorized oil was obtained; using the same finished product post-processing process as in Example 1, rice bran oil with high active substance content was obtained.

[0038] Comparative Example 1 This comparative example represents the existing conventional rice bran oil preparation process. The specific steps are as follows: Take rice bran raw material from the same batch as in Example 1, remove impurities and crush it, and directly use the same low-temperature cold pressing process as in Example 1 to press oil to obtain conventional cold-pressed crude oil; The crude oil is processed using the same full-process mild refining process as in Example 1 (enzymatic degumming, short-path physical deacidification, vacuum mild decolorization, and low-temperature short-path deodorization) to finally obtain the conventional rice bran oil product.

[0039] Comparative Example 2 This comparative example only involves the enzymatic release of precursor materials and does not involve in-situ directional catalytic conversion. The specific steps are as follows: Take rice bran raw materials from the same batch as in Example 1, and perform pretreatment and low-temperature compound enzymatic hydrolysis according to steps S1 and S2 of Example 1. After enzymatic hydrolysis, the material does not undergo the in-situ directional catalytic reaction in step S3, but is directly subjected to low-temperature cold pressing and the same mild refining process as in step S4 of Example 1, and finally obtains rice bran oil product.

[0040] Comparative Example 3 This comparative example uses conventional enzymatic hydrolysis + free enzyme catalysis, without using an in-situ solid-phase system. The specific steps are as follows: Take rice bran raw material from the same batch as in Example 1, and pretreat it according to step S1 of Example 1; then enzymatic hydrolysis is performed according to step S2 of Example 1. After enzymatic hydrolysis, free ferulic acid and free phytosterols are extracted with 80% ethanol solution. After solid-liquid separation, the extract is concentrated to obtain the extract; mix the extract with cold-pressed crude rice bran oil, add free lipase and acyltransferase, and carry out esterification and transesterification reactions in an organic phase system. After the reaction is completed, remove the solvent to obtain the reacted oil; process the reacted oil according to the refining process of Example 1 to finally obtain the finished rice bran oil.

[0041] The content of core active substances in the rice bran oil products prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the test results are shown in the table below.

[0042]

[0043] The rice bran oil prepared in Examples 1-3 of this invention contains significantly higher levels of oryzanol, phytosterols, tocotrienols, and sterol ferulic acid esters than the rice bran oil prepared by conventional processes in Comparative Example 1. This fully demonstrates that the technical solution of this invention can efficiently achieve the directional conversion of precursors, significantly increase the content of active substances in rice bran oil, and completely overcome the limitations of raw material background. Comparative Example 2 only underwent enzymatic release of precursors without in-situ directional catalytic conversion, and its content of active substances was significantly lower than that of the examples of this invention. This is because the free ferulic acid released by enzymatic release is water-soluble, and the free phytosterols are also poorly lipid-soluble, resulting in a large loss during oil extraction and refining, and thus failing to accumulate in the rice bran oil. This fully demonstrates the effectiveness of the integrated system of enzymatic release + in-situ solid-phase directional catalytic conversion of this invention. The necessity and innovation of this invention lie in the fact that only through in-situ catalytic conversion, transforming the precursor into a lipid-soluble, highly active component, can the high concentration of active substances in rice bran oil be achieved. Comparative Example 3, employing a conventional enzymatic extraction-separation-solvent-phase catalysis process, exhibits a much lower content of active substances than the embodiments of this invention. Furthermore, the oil has a higher peroxide value and poorer color. This is because the multi-step separation and extraction process results in significant substrate loss, poor catalytic selectivity of the free enzyme, numerous side reactions, low conversion rate of the target product, and the use of organic solvents that easily leads to oxidation of active substances, affecting product quality. In contrast, the in-situ solid-phase system of this invention eliminates the need for separation and extraction, avoiding substrate loss. Simultaneously, the immobilized enzyme exhibits strong catalytic selectivity, resulting in a high conversion rate of the target product. The entire process is conducted at low temperatures, in the dark, and with controlled oxygen, leading to superior product quality.

[0044] The rice bran oil prepared by this invention has added a highly active sterol ferulic acid ester component, which is almost absent in conventional rice bran oil. At the same time, the content of tocotrienols is greatly increased, realizing the quality upgrade of the active components. The antioxidant activity and physiological function of the product are significantly better than those of conventional rice bran oil.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing rice bran oil with high content of active substances, characterized in that, The method includes the following specific steps: S1: Take fresh rice bran raw material, first remove impurities by combination impurity removal, then perform low-temperature controllable pulverization, and then use atomization conditioning process to adjust the moisture content of the material. The whole process is carried out at low temperature and in the dark to obtain pre-treated uniform material. S2: Add a complex enzymatic hydrolysis system to the pretreated material. The complex enzymatic hydrolysis system includes ferulic acid esterase, glycosidase, and sterol glycosidase. The enzymatic hydrolysis reaction is carried out under low temperature and light-protected conditions to break the ester bond and glycosidic bond of the bound precursor, release free ferulic acid and free phytosterol, and obtain the enzymatically hydrolyzed material. S3: Adjust the water activity of the material after enzymatic hydrolysis, add an immobilized composite catalytic enzyme system, which includes immobilized lipase and immobilized acyltransferase, and carry out catalytic reaction in the rice bran in-situ solid phase system. Catalyze the directed esterification and transesterification reaction of free ferulic acid with phytosterols and glycerides to generate oryzanol monomer and sterol ferulic acid ester. At the same time, catalyze the cyclization and methylation modification of tocopherol precursors to convert them into tocotrienols, and obtain the catalytically hydrolyzed material. S4: Extract oil from the catalytically catalyzed material and then perform mild refining to obtain rice bran oil with high content of active substances.

2. The method for preparing rice bran oil with high active substance content according to claim 1, characterized in that, In S2, the amount of the compound enzymatic hydrolysis system added, based on the dry weight of rice bran, is: ferulic acid esterase 100-300 U / g, glycosidase 50-200 U / g, and sterol glycosidase 80-250 U / g.

3. The method for preparing rice bran oil with high active substance content according to claim 1, characterized in that, In S2, the enzymatic hydrolysis process conditions are as follows: the pH value of the system is adjusted to 4.5-6.5 using a food-grade citric acid-sodium citrate buffer system, the reaction temperature is controlled at 30-45℃, the entire process is protected from light and purged with nitrogen or argon gas, and the reaction time is 6-16 hours.

4. The method for preparing rice bran oil with high content of active substances according to claim 1, characterized in that, In step S3, adjusting the water activity of the enzymatically hydrolyzed material specifically involves placing the enzymatically hydrolyzed material in a sealed conditioning vessel, regulating the humidity of the system through low-temperature drying nitrogen circulation, controlling the material temperature to ≤40℃, gradually adjusting the water activity of the system to 0.2-0.4, and ensuring that the water activity deviation of the entire batch of material is ≤0.

05.

5. The method for preparing rice bran oil with high active substance content according to claim 1, characterized in that, In S3, the amount of immobilized composite catalytic enzyme system added, based on the dry weight of rice bran, is: 150-300 U / g of immobilized lipase and 80-250 U / g of immobilized acyltransferase.

6. The method for preparing rice bran oil with high content of active substances according to claim 1, characterized in that, In S3, the carriers for immobilized lipase and immobilized acyltransferase are porous carriers including food-grade macroporous adsorption resin and diatomaceous earth, and the immobilized enzymes can be recycled and reused.

7. The method for preparing rice bran oil with high content of active substances according to claim 1, characterized in that, In S3, the process conditions for the catalytic reaction are: controlling the reaction temperature at 35-50℃, avoiding light throughout the process and introducing inert gas for protection, and the reaction time is 8-24h.

8. The method for preparing rice bran oil with high content of active substances according to claim 1, characterized in that, In S4, the low-temperature and mild oil extraction process adopts any one of low-temperature cold pressing, subcritical butane extraction, or supercritical CO2 extraction.

9. The method for preparing rice bran oil with high content of active substances according to claim 1, characterized in that, In S4, the mild refining process includes enzymatic degumming, physical deacidification, mild decolorization, and low-temperature short-path deodorization, all performed sequentially, and the entire process adopts a low-loss process.

10. A rice bran oil with a high content of active substances, prepared by the method for preparing a rice bran oil with a high content of active substances according to any one of claims 1-9, characterized in that, The rice bran oil contains ≥5.2 mg / g of oryzanol, ≥5.6 mg / g of phytosterols, ≥0.9 mg / g of tocotrienols, and ≥0.8 mg / g of sterol ferulic acid esters.

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