Method for hot air pretreatment extraction of oat oil

Abstract

The application discloses a hot air pretreatment method for extracting oat oil and belongs to the technical field of oil extraction. The application solves the technical problems of low extraction efficiency, easy oxidation of oil and large solvent consumption existing in the prior art. The method comprises the following steps: a. oat bran is dried by hot air at 130-150 DEG C for 15-20 min; b. the oat bran is placed in a negative pressure environment, and ethanol vapor flash treatment is performed for 5-15 min; c. the oat bran is mixed with a mixed solvent of petroleum ether and ethanol, immobilized lipase and natural antioxidant are added, and extraction is performed for 8-12 h, and then filtration separation is performed; d. the first residue is mixed with the mixed solvent, extraction is performed for 4-6 h, and then filtration separation is performed; e. the first supernatant and the second supernatant are combined, the solvent is recovered by reduced pressure distillation, and oat crude oil is obtained; and f. the immobilized lipase is recovered. The method is mainly used for efficiently extracting high-quality oat oil from oat bran.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology. More specifically, this invention relates to a method for extracting oat oil using hot air pretreatment. Background Technology

[0002] Oat bran is a major byproduct of oat processing, containing abundant oils, primarily oat oil with high nutritional value. Oat oil is high in unsaturated fatty acids and also contains natural vitamin E and phenolic compounds, showing promising applications in the food, health product, and cosmetic industries. Extracting oat oil from oat bran is an important way to increase the added value of oat processing byproducts.

[0003] Currently, the main methods for extracting oil from oat bran include pressing and organic solvent extraction. Pressing relies on mechanical pressure to squeeze the oil out of the bran. This method is simple to operate, but the oil yield is low, and a large amount of oil remains in the bran, resulting in insufficient resource utilization. Organic solvent extraction utilizes the solubility of oil in organic solvents, dissolving the oil through methods such as soaking or percolation. This method has relatively high extraction efficiency and is commonly used in industrial production.

[0004] However, oat bran has a relatively dense structure, with components such as cellulose, hemicellulose, and protein encapsulating the oils, making it difficult for solvents to quickly penetrate the bran's interior. This results in longer extraction times and limited extraction efficiency. To improve extraction results, pretreatment of the bran is usually necessary to disrupt its structure and increase the contact area between the solvent and the oils. Common pretreatment methods include grinding, heat treatment, or extrusion puffing. While heat treatment can alter the bran's structure to some extent, conventional heat treatment has limited effect on disrupting the bran's structure, and improper temperature control can cause oil oxidation, affecting the quality of the extracted oils.

[0005] Furthermore, oat oil has a high content of unsaturated fatty acids, which are prone to oxidation during extraction and subsequent processing. This leads to increased acid value, unpleasant flavor, and compromised product quality. To inhibit oxidation, antioxidants are typically added during extraction or refined after extraction. However, the timing and method of adding antioxidants directly affect the final antioxidant effect. Therefore, effectively protecting the oil and reducing oxidation loss during extraction is a problem that needs to be addressed in actual production.

[0006] In solvent extraction, the consumption of organic solvents is a significant factor affecting production costs. Commonly used extraction solvents such as petroleum ether and n-hexane need to be recycled to reduce production costs. Solvent recovery typically employs distillation to separate the solvent from the oil and then recycle it. However, the recovered solvent may contain trace amounts of oil decomposition products or pigments, which can gradually accumulate during repeated solvent recycling, affecting subsequent extraction results and potentially even adversely impacting oil quality. Therefore, how to achieve effective solvent recycling while ensuring extraction efficiency is a crucial consideration in extraction process design.

[0007] The use of enzyme preparations to assist extraction has become a research focus in recent years. Enzymes such as lipases can act on lipids or cell wall components, helping to improve extraction efficiency. However, in practical applications, there are still many details to explore regarding the timing of enzyme addition, control of reaction conditions, and the recycling of enzyme preparations. Enzyme preparations are relatively expensive, and the inability to effectively recycle them will increase production costs.

[0008] In summary, existing methods for extracting oat oil from oat bran still have room for improvement in terms of pretreatment efficiency, antioxidant protection of the oil during extraction, solvent recovery and utilization, and the economic efficiency of enzyme preparation use. Designing an extraction method with high efficiency, good oil quality, and effective utilization of solvents and enzyme preparations is a key technical problem to be solved in the extraction of oat oil from oat bran. Summary of the Invention

[0009] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0010] Another objective of this invention is to provide a method for extracting oat oil through hot air pretreatment, which solves the problems of low extraction efficiency, easy oxidation of oil during extraction, and large solvent consumption in existing oat bran oil extraction methods.

[0011] To achieve these objectives and other advantages according to the present invention, a method for hot air pretreatment extraction of oat oil is provided, comprising the following steps:

[0012] a. Hot air drying pretreatment: Using oat bran that has been roasted during the oat flour processing as raw material, hot air drying is carried out at 130-150℃ for 15-20 minutes to obtain hot air dried oat bran;

[0013] b. Negative pressure flash evaporation treatment: Place the hot-air dried oat bran obtained in step a in a negative pressure environment and pass ethanol vapor through it for flash evaporation treatment for 5-15 minutes to obtain flash-treated oat bran.

[0014] c. Reaction-Extraction Coupling: The flash-treated oat bran obtained in step b is mixed with a mixed solvent at a material-to-liquid ratio of 1:3 to 1:5. Immobilized lipase and a natural antioxidant are added, and the mixture is soaked and extracted at 40-60℃ for 8-12 hours. The mixed solvent is a mixture of petroleum ether and ethanol in a volume ratio of 1:1 to 3:1. The natural antioxidant is selected from at least one of rosemary extract, tea polyphenols, or vitamin E. The amount added is based on the mass of the oat bran obtained in step a, with the amount of rosemary extract being 0.1-0.7 g / kg, the amount of tea polyphenols being 0.1-0.4 g / kg, and the amount of vitamin E being 0.1-10 g / kg. The mixture is filtered to separate the first supernatant, the first residue, and the immobilized lipase. The immobilized lipase is a preparation of lipase B derived from Candida antarctica immobilized on macroporous acrylic resin.

[0015] d. Secondary extraction: The first residue obtained in step c is mixed with the mixed solvent described in step c, and the mixture is soaked and extracted at 40-60℃ for 4-6 hours. The second supernatant and the second residue are obtained by filtration.

[0016] e. Solvent recovery: Combine the first supernatant obtained in step c and the second supernatant obtained in step d, and distill under reduced pressure at 45°C to recover petroleum ether and ethanol, respectively, to obtain crude oat oil;

[0017] f. Enzyme recovery: The immobilized lipase obtained by filtration and separation in step c is recovered.

[0018] Preferably, the method further includes an enzymatic degumming step for the crude oat oil obtained in step e: heating the crude oat oil to 45-55°C, adjusting the pH to 4.5-5.5, adding phospholipase A1 at a concentration of 0.02%-0.1% of the crude oat oil mass, and reacting under stirring conditions for 2-4 hours; after the reaction is completed, heating to 80-90°C to inactivate the enzyme for 10-15 minutes, and centrifuging to obtain degummed oat oil.

[0019] Preferably, the method further includes a step of low-temperature adsorption decolorization of degummed oat oil: cooling the degummed oat oil to 35-45℃, adding a composite adsorbent, the amount of the composite adsorbent being 1%-3% of the mass of the degummed oat oil, and adsorbing for 30-60 minutes under stirring conditions; the composite adsorbent is a mixture of activated clay and food-grade silica gel in a mass ratio of 1:0.5 to 1:2; after adsorption, filtering and separation are performed to obtain decolorized oat oil.

[0020] Preferably, the process also includes a step of low-temperature vacuum deodorization of the bleached oat oil: heating the bleached oat oil to 120-150°C and passing direct steam under vacuum conditions with an absolute pressure of less than 200Pa for 1-3 hours for deodorization; using a dry condensation system to capture volatile substances during the deodorization process; and cooling the oil to 50-60°C under vacuum conditions after deodorization to obtain the finished oat oil.

[0021] Preferably, the process also includes a step of magnetic field-assisted adsorption purification of the finished oat oil: cooling the obtained finished oat oil to 25-35℃, adding a magnetic adsorbent, the amount of magnetic adsorbent added being 0.5%-1.5% of the mass of the finished oat oil, and adsorbing under stirring conditions for 20-40 minutes; the magnetic adsorbent is Fe3O4 magnetic microspheres with silica gel coating on the surface, with a particle size of 50-200nm; after adsorption treatment, the magnetic adsorbent is recovered by a magnetic field separation device, and then precisely filtered through a 0.22μm filter membrane to obtain high-purity oat oil.

[0022] Preferably, the method further includes a step of classifying and utilizing the second residue obtained in step d: adjusting the moisture content of the second residue to 8%-12%, and extruding and puffing it through an extruder at 120-150℃ and 2-4MPa to obtain puffed material; mixing the puffed material with a citrate buffer solution of pH 4.5-5.5 at a material-to-liquid ratio of 1:8 to 1:12, adding cellulase and β-glucanase, with enzyme addition amounts of 0.1%-0.3% and 0.05%-0.15% of the mass of the puffed material, respectively, and enzymatically hydrolyzing at 45-55℃ for 2-4 hours; after enzymatic hydrolysis, filtering and separating, concentrating and spray-drying the filtrate to obtain oat β-glucan, and drying and pulverizing the filter residue to obtain oat dietary fiber powder.

[0023] Preferably, after obtaining the immobilized lipase through filtration and separation in step c and obtaining crude oat oil in step e, the process further includes the following steps:

[0024] The immobilized lipase obtained by filtration and separation in step c is added to the crude oat oil obtained in step e at 0.05%-0.3% of the mass of crude oat oil obtained in step e. Under nitrogen protection, the reaction temperature is controlled at 55-65℃ and the reaction time is 8-10h. During the reaction, the water content of the system is maintained below 0.5%. After the reaction is completed, the immobilized lipase is recovered by passing it through a 40-60 mesh sieve.

[0025] The filtrate after passing through a 40-60 mesh sieve is subjected to vacuum distillation at a temperature of 40-50℃ and an absolute pressure of 100-300Pa for 10-20 minutes, and then filtered through a plate and frame filter press to obtain refined oat oil.

[0026] Preferably, the ethanol vapor in step b is recycled ethanol that has been vaporized and reused; the recycled ethanol is derived from the ethanol recovered by vacuum distillation in step e, which is dehydrated to a water content of 3%-5% by anhydrous sodium sulfate fixed bed, while simultaneously adsorbing and removing pigments and oil decomposition products entrained in the recycled ethanol, and then vaporized into ethanol vapor at 115-125℃, which is recycled for the negative pressure flash evaporation treatment in step b.

[0027] The present invention has at least the following beneficial effects:

[0028] First, this invention effectively destroys the dense structure of oat bran through the synergistic effect of hot air drying pretreatment and negative pressure flash evaporation treatment, improves the accessibility of the solvent to the oil, achieves rapid dissolution of the oil under mild conditions, significantly shortens the extraction time, and avoids the oil oxidation problem caused by long-term high-temperature treatment, thereby improving extraction efficiency and oil quality.

[0029] Secondly, this invention introduces immobilized lipase and natural antioxidants during the extraction process. While the lipase catalyzes the release of oil, it promotes the synergistic effect between the antioxidant and the oil, effectively protecting the oil during the extraction stage, inhibiting the oxidative degradation of unsaturated fatty acids, and reducing the oxidation risk in the subsequent refining process. The resulting oat oil has a low crude oleic acid value, light color, and good quality stability.

[0030] Third, this invention achieves multiple reuses of enzyme preparations and organic solvents by recycling immobilized lipases and using vacuum distillation of solvents, thereby reducing production costs. At the same time, the recovered ethanol is dehydrated and purified before being recycled for the pretreatment process, ensuring the stability of solvent quality, avoiding the impact of impurity accumulation on the extraction effect, and improving the economy and environmental friendliness of the process.

[0031] Fourth, this invention further recovers β-glucan and dietary fiber from the extracted bran residue through enzymatic hydrolysis, realizing multi-level utilization of oat bran, increasing the added value of by-products, reducing resource waste, and forming a complete process chain from oil extraction to functional component recovery.

[0032] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0034] <Example 1>

[0035] This invention discloses a method for hot air pretreatment to extract oat oil, specifically including the following steps:

[0036] a. Hot air drying pretreatment: Take 1000g of roasted oat bran, spread it evenly in a tray with a layer thickness of about 2cm, place it in a hot air drying oven, and dry it at 140℃ for 18min. Turn it over once every 5min during the process to ensure even heating, and obtain hot air dried oat bran.

[0037] b. Negative pressure flash evaporation treatment: Place the hot-air dried oat bran obtained in step a into a negative pressure flash evaporation tank, evacuate to an absolute pressure of 15 kPa, introduce ethanol vapor at a temperature of 115℃ and a flow rate of 5 L / min, and flash evaporate for 10 min, maintaining a negative pressure state inside the tank during the process, to obtain the flash-treated oat bran.

[0038] c. Reaction-Extraction Coupling: Take 500g of the flash-treated oat bran obtained in step b, place it in an extraction tank, add 2000mL of a mixed solvent of petroleum ether (boiling range 60-90℃) and ethanol in a volume ratio of 2:1 (solid-liquid ratio 1:4), add 0.25g of immobilized lipase (equivalent to 0.5g / kg bran), the immobilized lipase being a preparation of Candida antarcticis lipase B immobilized on macroporous acrylic resin (the immobilized lipase in this example is from Novozymes 435, and unless otherwise specified in the following examples and comparative examples, the immobilized lipase used is the same), and add 0.2g of the natural antioxidant rosemary extract (25% oxalic acid content) (equivalent to 0.4g / kg bran). Soak and extract in a 50℃ water bath for 10h, stirring intermittently at 60rpm for 5min each time, and stirring once every hour. After extraction, the mixture was filtered through a 200-mesh filter cloth to obtain the first supernatant, the first residue, and the immobilized lipase. The filtered immobilized lipase was washed three times with petroleum ether, 50 mL each time. The washings were added to the first supernatant. The washed immobilized lipase was then vacuum-dried at 40°C for 2 hours and recovered for later use.

[0039] d. Secondary extraction: Place the first residue obtained in step c into an extraction tank, add 2000 mL of a mixed solvent of petroleum ether and ethanol with the same composition as in step c, and extract by soaking in a water bath at 50°C for 5 hours. During the extraction, stir intermittently at 60 rpm for 5 minutes each time, and stir once every hour. After extraction, filter through a 200-mesh filter cloth to separate the second supernatant and the second residue.

[0040] e. Solvent recovery: Combine the first supernatant obtained in step c and the second supernatant obtained in step d, place them in a rotary evaporator, and distill under reduced pressure at a water bath of 45°C and an absolute pressure of 20 kPa. First, recover petroleum ether (control the temperature of the receiving flask at -5°C). After no more petroleum ether is distilled off, switch the receiving flask and continue distilling under the same conditions to recover ethanol, obtaining 46.3 g of crude oat oil.

[0041] f. Enzyme recovery: The immobilized lipase, after being filtered, separated, washed, and dried in step c, was weighed. The recovered mass was 0.23 g, with a recovery rate of 92.0%.

[0042] <Example 2>

[0043] Example 2 differs from Example 1 in that, after obtaining crude oat oil, it further includes the following steps:

[0044] g. Enzymatic degumming: Take 40g of crude oat oil obtained in step e, heat to 50℃, adjust the pH to 5.0 with 0.1mol / L citric acid solution, add 0.02g of phospholipase A1 (Novozymes, enzyme activity 10000U / g) (the amount added is 0.05% of the crude oil mass), and stir at 100rpm for 3h in a 50℃ water bath. After the reaction is completed, heat to 85℃ and hold for 12min to inactivate the enzyme, then transfer to a centrifuge tube, centrifuge at 4000rpm for 15min, separate the upper oil phase, and obtain 38.5g of degummed oat oil.

[0045] h. Low-temperature adsorption decolorization: The degummed oat oil obtained in step g was cooled to 40℃, and 0.77g of composite adsorbent (activated clay: food-grade silica gel mass ratio 1:1) was added (the amount added is 2% of the mass of the degummed oil). Adsorption was carried out in a 40℃ water bath with stirring at 150rpm for 45min. After adsorption, the adsorbent was separated by qualitative filter paper under normal pressure to obtain 37.8g of decolorized oat oil.

[0046] i. Low-temperature vacuum deodorization: The decolorized oat oil obtained in step h was placed in a deodorization kettle, heated to 135℃, and evacuated to an absolute pressure of 150Pa. Direct steam (steam flow rate 0.5L / min) was introduced, and deodorization was performed for 2 hours. During the deodorization process, a dry condensation system (condensation temperature -10℃) was used to capture volatile substances. After deodorization, cooling water was circulated while maintaining a vacuum state, and the oil was cooled to 55℃. The vacuum was then broken, and the oil was removed to obtain 36.5g of finished oat oil. The finished oil was pale yellow, clear and transparent, and had the inherent aroma of oats.

[0047] <Example 3>

[0048] Example 3 differs from Example 2 in that, after obtaining the finished oat oil in step i, the following steps are also included:

[0049] j. Magnetic field-assisted adsorption purification: The oat oil obtained in step i was cooled to 30℃, and 0.36g of magnetic adsorbent (Fe3O4 magnetic microspheres coated with silica gel, particle size 100nm) was added (the addition amount is 1.0% of the oil mass). Adsorption was carried out in a 30℃ water bath with stirring at 200rpm for 30min. After adsorption, the oil was passed through a magnetic field separation device (magnetic field strength 0.5T) to recover the magnetic adsorbent. The collected oil was then vacuum filtered through a 0.22μm microporous membrane to obtain 35.8g of high-purity oat oil.

[0050] The magnetic adsorbent was prepared as follows: Fe3O4 nanoparticles (approximately 20 nm) were mixed with tetraethyl orthosilicate (TEOS) at a molar ratio of 5:1 and ultrasonically dispersed in a mixed solution of ethanol and water (ethanol:water volume ratio 4:1), controlling the TEOS concentration to be 0.6 mol / L. Ammonia was added to adjust the pH to 9.5, and the reaction was carried out at room temperature with stirring for 8 hours. The stirring speed was maintained at 800 rpm during the reaction. The reaction product was magnetically separated, washed with ethanol, and vacuum dried to obtain Fe3O4 magnetic microspheres coated with silica gel. By adjusting the concentration of TEOS in the reaction system and the reaction time, the thickness of the silica gel coating layer could be controlled, so that the final particle size was stabilized at around 100 nm.

[0051] <Example 4>

[0052] Example 4 differs from Example 3 in that it further includes the following steps:

[0053] k. Graded utilization: Take the second residue (approximately 300g after drying) obtained in step d of Example 3, adjust the moisture content to 10%, place it in an extrusion puffing machine, and extrude and puff it at 135℃ and 3MPa to obtain puffed material. Take 100g of puffed material, add 1000mL of citrate buffer solution with pH 5.0 (material-to-liquid ratio 1:10), add 0.2g of cellulase (enzyme activity 50000U / g) (addition amount 0.2%) and 0.1g of β-glucanase (enzyme activity 20000U / g) (addition amount 0.1%), and stir at 100rpm for 3h in a 50℃ water bath for enzymatic hydrolysis. After enzymatic hydrolysis, filter through a 200-mesh filter cloth to separate the filtrate and filter residue. The filtrate was concentrated under reduced pressure at 60°C to 1 / 5 of its original volume, and then spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C to obtain 6.2g of oat β-glucan powder (78% purity). The filter residue was dried at 80°C to constant weight, pulverized and passed through an 80-mesh sieve to obtain 78.5g of oat dietary fiber powder (85% dietary fiber content).

[0054] <Example 5>

[0055] Example 5 is the same as Example 4, except that after obtaining crude oat oil in step e and before enzymatic degelatination in step g, a phenol esterification step is added: 40g of crude oat oil obtained in step e is placed in a reaction flask, and 0.12g of immobilized lipase recovered in step f (the amount added is 0.3% of the crude oil mass) is added. Nitrogen gas is introduced to replace the air in the flask, and after sealing, the mixture is stirred at 120rpm in a 60℃ water bath for 9 hours. The system is kept sealed during the reaction. After the reaction, the immobilized lipase is recovered by filtration through a 60-mesh sieve (the recovered enzyme is washed with petroleum ether, dried, and weighed to obtain 0.11g, with a recovery rate of 91.7%). The filtrate is the phenol-esterified oat oil, which is used for the subsequent refining process in step g1. The remaining steps are the same as in Example 4, including the fractional utilization in step k.

[0056] <Example 6>

[0057] The difference from Example 1 is that the following steps are also included: 1000 mL of ethanol recovered by vacuum distillation in step e is passed through a fixed-bed adsorption column packed with anhydrous sodium sulfate (column diameter 5 cm, packing height 30 cm, anhydrous sodium sulfate particle size 20-40 mesh) at a controlled flow rate of 5 mL / min for dehydration and adsorption treatment. The treated ethanol is sampled and its water content is measured to be 4.2%, which meets the requirement of 3%-5% water content. The treated ethanol is colorless and transparent with no odor.

[0058] The treated ethanol was vaporized at 120°C and used for negative pressure flash evaporation of oat bran according to the process parameters of step b in Example 1 (absolute pressure 15 kPa, flow rate 5 L / min, flash evaporation for 10 min). The above extraction-recovery-treatment-circulation process was repeated 10 times.

[0059] <Comparative Example 1>

[0060] Comparative Example 1 has no pretreatment step compared to Example 1, as detailed below:

[0061] a. Hot air drying pretreatment: omitted.

[0062] b. Negative pressure flash evaporation treatment: omitted.

[0063] c. Reaction-extraction coupling: Same as step c in Example 1.

[0064] d. Secondary extraction: Same as step d in Example 1.

[0065] e. Solvent recovery: Same as step e in Example 1, to obtain 39.2g of crude oat oil.

[0066] f. Enzyme recovery: Same as step f in Example 1, 0.22 g of immobilized lipase was recovered, with a recovery rate of 88.0%.

[0067] <Comparative Example 2>

[0068] Comparative Example 2, compared to Example 1, contains no enzymes and no antioxidants, as detailed below:

[0069] a. Hot air drying pretreatment: Same as step a in Example 1.

[0070] b. Negative pressure flash evaporation treatment: Same as step b in Example 1.

[0071] c. Reaction-Extraction Coupling: Take 500g of the flash-treated oat bran obtained in step b, place it in an extraction tank, add 2000mL of a mixed solvent of petroleum ether and ethanol at a volume ratio of 2:1, without adding immobilized lipase and rosemary extract, and soak and extract in a 50℃ water bath for 10h, stirring intermittently at 60rpm during the extraction process. After extraction, filter through a 200-mesh filter cloth to separate the first supernatant and the first residue (without immobilized lipase, which can be recovered).

[0072] d. Secondary extraction: Same as step d in Example 1.

[0073] e. Solvent recovery: Same as step e in Example 1, to obtain 45.9g of crude oat oil.

[0074] f. Enzyme recovery: None.

[0075] <Comparative Example 3>

[0076] Compared with Example 1, Comparative Example 3 used pure petroleum ether solvent, as follows:

[0077] a. Hot air drying pretreatment: Same as step a in Example 1.

[0078] b. Negative pressure flash evaporation treatment: Same as step b in Example 1.

[0079] c. Reaction-Extraction Coupling: Take 500g of the flash-treated oat bran obtained in step b, place it in an extraction tank, add 2000mL of petroleum ether (boiling range 60-90℃, without ethanol), add 0.25g of immobilized lipase, and add 0.2g of rosemary extract. Soak and extract in a 50℃ water bath for 10h, stirring intermittently at 60rpm during the extraction process. After extraction, filter through a 200-mesh filter cloth to separate the first supernatant, the first residue, and the immobilized lipase. Wash the filtered immobilized lipase three times with petroleum ether, 50mL each time. The washings are combined with the first supernatant. The washed immobilized lipase is vacuum-dried at 40℃ for 2h and recovered for later use.

[0080] d. Secondary extraction: Place the first residue in an extraction tank, add 2000 mL of petroleum ether, and extract by soaking in a 50°C water bath for 5 hours, stirring intermittently at 60 rpm during the extraction process. After extraction, filter through a 200-mesh filter cloth to obtain the second supernatant and the second residue.

[0081] e. Solvent recovery: The first and second supernatants were combined and placed in a rotary evaporator. The petroleum ether was recovered by vacuum distillation under the conditions of a 45°C water bath and an absolute pressure of 20 kPa, yielding 43.8 g of crude oat oil.

[0082] f. Enzyme recovery: The immobilized lipase, after being filtered, separated, washed, and dried in step c, was weighed. The recovered mass was 0.22 g, with a recovery rate of 88.0%.

[0083] <Comparative Example 4>

[0084] Compared with Example 1, Comparative Example 4 added an antioxidant after extraction, as follows:

[0085] a. Hot air drying pretreatment: Same as step a in Example 1.

[0086] b. Negative pressure flash evaporation treatment: Same as step b in Example 1.

[0087] c. Reaction-Extraction Coupling: Take 500g of the flash-treated oat bran obtained in step b, place it in an extraction tank, add 2000mL of a mixed solvent of petroleum ether and ethanol at a volume ratio of 2:1, add 0.25g of immobilized lipase, without adding rosemary extract, and soak and extract in a 50℃ water bath for 10h, stirring intermittently at 60rpm during the extraction process. After extraction, immediately add 0.2g of rosemary extract to the extract, stir for 10min, and then filter through a 200-mesh filter cloth to separate, obtaining the first supernatant, the first residue, and the immobilized lipase. Wash the filtered immobilized lipase three times with petroleum ether, 50mL each time, and combine the washings with the first supernatant. Dry the washed immobilized lipase under vacuum at 40℃ for 2h and recover it for later use.

[0088] d. Secondary extraction: Same as step d in Example 1.

[0089] e. Solvent recovery: Same as step e in Example 1, to obtain 46.1g of crude oat oil.

[0090] f. Enzyme recovery: Same as step f in Example 1, 0.22 g of immobilized lipase was recovered, with a recovery rate of 88.0%.

[0091] <Indicator Detection>

[0092] 1. Oil yield

[0093] The mass of the crude oat oil obtained in step e is calculated using the following formula:

[0094] Oil yield (%) = (mass of crude oat oil / mass of oat bran used for extraction in step c) × 100%.

[0095] 2. Petroleum ether recovery rate

[0096] Measure the volume of petroleum ether recovered in step e and calculate it using the following formula:

[0097] Petroleum ether recovery rate (%) = (volume of recovered petroleum ether / total volume of petroleum ether used) × 100%.

[0098] 3. Ethanol recovery rate

[0099] Measure the volume of ethanol recovered in step e and calculate it using the following formula:

[0100] Ethanol recovery rate (%) = (volume of recovered ethanol / total volume of ethanol used) × 100%.

[0101] 4. Acid value

[0102] The acid value was determined according to GB 5009.229-2016, "National Food Safety Standard - Determination of Acid Value in Food".

[0103] 5. Peroxide value

[0104] The peroxide value was determined according to GB 5009.227-2016, "National Food Safety Standard: Determination of Peroxide Value in Food".

[0105] 6. Phospholipid content

[0106] The content of phospholipids in grains and oils was determined according to GB / T 5537-2008 "Determination of Phospholipid Content in Grains and Oils".

[0107] 7. Oxidation induction time

[0108] The Rancimat method was used for determination.

[0109] Instrument: Rancimat 743 oil oxidation stability tester (Swiss Metrohm).

[0110] Measurement conditions: temperature 110℃, air flow rate 20L / h, sample amount 3g.

[0111] Determination method: Weigh 3g of oil sample (accurate to 0.01g) into the reaction tube, and install the reaction tube and absorption tube according to the instrument operating procedure (add 50mL of deionized water to the absorption tube). Set the temperature to 110℃ and the air flow rate to 20L / h, and start the determination. The instrument automatically records the conductivity-time curve and calculates the oxidation induction time (i.e., the time when the conductivity begins to rise sharply). The results are expressed in hours (h).

[0112] 8. β-glucan yield

[0113] Weigh the oat β-glucan powder obtained by spray drying and calculate the mass using the following formula:

[0114] β-glucan yield (%) = (mass of β-glucan powder / mass of puffed material) × 100%.

[0115] <Measurement Results>

[0116] 1. The oil yield, petroleum ether recovery rate, ethanol recovery rate, acid value, and peroxide value of Example 1 and Comparative Examples 1-4 were determined. The specific results are shown in Table 1.

[0117] Table 1

[0118]

[0119] Note: Comparative Example 3 did not use ethanol, therefore there is no data on ethanol recovery rate.

[0120] As can be seen from the data in Table 1, Example 1 is superior to the other comparative examples in terms of oil yield and oil quality. This is mainly attributed to the synergistic effect of multiple technical features in the technical solution of the present invention.

[0121] Compared to Example 1, Comparative Example 1 omitted the hot air drying and negative pressure flash evaporation pretreatments. Oat bran has a dense structure, with cellulose, hemicellulose, and protein encapsulating the oils, making rapid solvent penetration difficult. Hot air drying, under specific temperature and time conditions, rapidly vaporizes the internal moisture of the bran, creating micropores; negative pressure flash evaporation utilizes the penetrating power of ethanol vapor and its instantaneous pressure reduction to further disrupt the cell wall structure. The synergistic effect of both significantly increases the contact area between the solvent and the oils, improving extraction efficiency. In other words, the hot air-flash evaporation pretreatment is the core determining factor for improving extraction efficiency. Simultaneously, the pretreatment allows for more complete exposure of the oils, shortening the contact time between the oils and oxygen during extraction, and also contributes to inhibiting oxidation.

[0122] Compared to Example 1, Comparative Example 2 did not include immobilized lipase or natural antioxidants. During extraction, the immobilized lipase not only catalyzes the release of triglycerides, but more importantly, it catalyzes the transesterification reaction between natural antioxidants and triglycerides or free fatty acids in the oil, generating esterified products with antioxidant functions. This in-situ reaction covalently binds the antioxidant components to the oil molecules, forming effective protection during the extraction stage. The phenolic hydroxyl groups in the natural antioxidants can capture free radicals, chelate metal ions, and inhibit the chain reaction of oil oxidation. The synergistic effect of both significantly reduces the degree of hydrolysis and oxidation of the oil. Simultaneously introducing immobilized lipase and natural antioxidants during extraction enables in-situ catalytic protection, which is crucial for ensuring oil quality.

[0123] Compared to Example 1, Comparative Example 3 used pure petroleum ether instead of the mixed solvent of petroleum ether and ethanol. The addition of ethanol not only improved the solubility of polar lipids and antioxidants, but more importantly, provided a suitable microenvironment for the immobilized lipase-catalyzed reaction. As a polar solvent, ethanol improves the interfacial contact between the enzyme and substrate, promoting enzyme catalytic efficiency. Simultaneously, the presence of ethanol helps disperse natural antioxidants in the oil phase, allowing them to react more fully with the oils. The pure petroleum ether system lacks this polar environment, resulting in reduced enzyme catalytic efficiency, limited antioxidant activity, and consequently, a decline in oil quality.

[0124] Compared to Example 1, in Comparative Example 4, the antioxidant was added only after extraction. This demonstrates the crucial importance of the timing design of the "reaction-extraction coupling." Only when immobilized lipase and natural antioxidants are present simultaneously during extraction can an in-situ catalytic reaction be achieved, allowing the antioxidant components to covalently bind to the oil molecules. Adding the antioxidant after extraction only achieves physical mixing; the antioxidant cannot penetrate the internal structure of the oil molecules and is easily removed or deactivated during subsequent processing and storage, significantly reducing its protective effect.

[0125] 2. The phospholipid content and oxidation induction time of Examples 2-5 were determined, and the β-glucan yield of Examples 4-5 was determined. The specific results are shown in Table 2.

[0126] Table 2

[0127]

[0128] As can be seen from the data in Table 2, from Example 2 to Example 5, with the assistance of more technical features, the quality of the oil continued to improve. This proves that there is no conflict between the various technical features and that they have a synergistic effect.

[0129] Example 2 adds enzymatic degumming, low-temperature adsorption decolorization, and low-temperature vacuum deodorization steps to Example 1. Enzymatic degumming utilizes phospholipase A1 to specifically hydrolyze the colloidal components (mainly phospholipids) in the oil, converting them into hydrated substances that are easy to separate. After degumming, the phospholipid content is significantly reduced, improving not only the appearance and stability of the oil but also creating favorable conditions for subsequent decolorization and deodorization. Low-temperature adsorption decolorization uses a composite adsorbent of activated clay and food-grade silica gel to adsorb and remove pigments, trace metals, and oxidation products under relatively low temperatures, avoiding the adverse effects of high temperatures on oil quality. Low-temperature vacuum deodorization involves introducing direct steam under vacuum conditions, utilizing steam stripping to remove volatile odor components such as free fatty acids, aldehydes, and ketones, while the lower temperature protects heat-sensitive nutrients.

[0130] Example 3 adds a magnetic field-assisted adsorption purification step to Example 2. Fe3O4 magnetic microspheres coated with silica gel have a large specific surface area and excellent adsorption performance, enabling selective adsorption of trace polar impurities remaining in the oil. After adsorption, the magnetic adsorbent is recovered using a magnetic field separation device, avoiding clogging of the filter media and allowing for reusability of the adsorbent. This step further removes trace impurities that may catalyze oxidation, improving the oxidative stability of the oil.

[0131] Example 4 adds a step of graded utilization of the extraction residue to Example 3. The second residue still contains abundant β-glucan and dietary fiber. Through extrusion puffing, the material is instantaneously puffed under high temperature and pressure, destroying the dense structure of the residue and increasing enzyme accessibility. Subsequently, cellulase and β-glucanase are used synergistically to convert insoluble polysaccharides into soluble components. The filtrate is concentrated and spray-dried to obtain oat β-glucan, and the filter residue is dried and pulverized to obtain oat dietary fiber powder. This step achieves multi-stage utilization of oat bran, increases the added value of by-products, and runs parallel to the main process without affecting oil extraction and refining effects.

[0132] Example 5 adds an enzymatic phenol esterification step to Example 4. This step utilizes the immobilized lipase recovered in step c to catalyze the esterification or transesterification reaction of residual free fatty acids or glycerides in crude oat oil with the natural antioxidants introduced in step c, generating the corresponding phenolic ester derivatives. The phenolic esters retain the antioxidant active groups of polyphenols and have stronger lipid solubility, allowing them to be firmly integrated into the oil system. More importantly, the covalently bound antioxidant components are not easily removed or destroyed in subsequent refining processes such as degumming, decolorization, deodorization, and magnetic field purification, and can be retained in the final finished oil. Therefore, Example 5 significantly extends the oxidation induction time, further reduces the phospholipid content, and achieves optimal oil quality.

[0133] In summary, the various technical features of this invention have good compatibility, positive synergy, and synergistic effects, achieving efficient extraction, deep refining, and high-value utilization of oat oil byproducts.

[0134] 3. Verification of Cyclic Effect: Oat bran treated with ethanol vapor in the 1st, 5th, and 10th cycles of Example 6 was extracted and the oil quality was tested according to step ce in Example 1. Fresh ethanol (without recycling) was used as a control. The test results are shown in Table 3.

[0135] Table 3

[0136]

[0137] As shown in Table 3, after the recovered ethanol was treated with anhydrous sodium sulfate fixed bed and recycled 10 times, the oil yield, acid value and peroxide value of the crude oat oil were not significantly different from those of the fresh ethanol treatment group. This proves that the treatment method can effectively remove moisture and impurities from the recovered ethanol and ensure the process stability of recycling.

[0138] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for hot air pretreatment to extract oat oil, characterized in that, Includes the following steps: a. Hot air drying pretreatment: Using oat bran that has been roasted during the oat flour processing as raw material, hot air drying is carried out at 130-150℃ for 15-20 minutes to obtain hot air dried oat bran; b. Negative pressure flash evaporation treatment: Place the hot-air dried oat bran obtained in step a in a negative pressure environment and pass ethanol vapor through it for flash evaporation treatment for 5-15 minutes to obtain flash-treated oat bran. c. Reaction-Extraction Coupling: The flash-treated oat bran obtained in step b is mixed with a mixed solvent at a material-to-liquid ratio of 1:3 to 1:

5. Immobilized lipase and a natural antioxidant are added, and the mixture is soaked and extracted at 40-60℃ for 8-12 hours. The mixed solvent is a mixture of petroleum ether and ethanol in a volume ratio of 1:1 to 3:

1. The natural antioxidant is selected from at least one of rosemary extract, tea polyphenols, or vitamin E. The amount added is based on the mass of the oat bran obtained in step a, with the amount of rosemary extract being 0.1-0.7 g / kg, the amount of tea polyphenols being 0.1-0.4 g / kg, and the amount of vitamin E being 0.1-10 g / kg. The mixture is filtered to separate the first supernatant, the first residue, and the immobilized lipase. d. Secondary extraction: The first residue obtained in step c is mixed with the mixed solvent described in step c, and the mixture is soaked and extracted at 40-60℃ for 4-6 hours. The second supernatant and the second residue are obtained by filtration. e. Solvent recovery: Combine the first supernatant obtained in step c and the second supernatant obtained in step d, and distill under reduced pressure at 45°C to recover petroleum ether and ethanol, respectively, to obtain crude oat oil; f. Enzyme recovery: The immobilized lipase obtained by filtration and separation in step c is recovered; After obtaining the immobilized lipase through filtration and separation in step c and the crude oat oil in step e, the following steps are also included: The immobilized lipase obtained by filtration and separation in step c is added to the crude oat oil obtained in step e at 0.05%-0.3% of the mass of crude oat oil obtained in step e. Under nitrogen protection, the reaction temperature is controlled at 55-65℃ and the reaction time is 8-10h. During the reaction, the water content of the system is maintained below 0.5%. After the reaction is completed, the immobilized lipase is recovered by passing it through a 40-60 mesh sieve. The filtrate after passing through a 40-60 mesh sieve is subjected to vacuum distillation at a temperature of 40-50℃ and an absolute pressure of 100-300Pa for 10-20 minutes, and then filtered through a plate and frame filter press to obtain refined oat oil.

2. The method for hot air pretreatment to extract oat oil as described in claim 1, characterized in that, The process also includes an enzymatic degumming step for the crude oat oil obtained in step e: the crude oat oil is heated to 45-55℃, the pH is adjusted to 4.5-5.5, phospholipase A1 is added at a concentration of 0.02%-0.1% of the crude oat oil mass, and the mixture is reacted for 2-4 hours under stirring. After the reaction is completed, the temperature is raised to 80-90℃ to inactivate the enzyme for 10-15 minutes, and the degummed oat oil is obtained by centrifugation.

3. The method for hot air pretreatment to extract oat oil as described in claim 2, characterized in that, The method also includes a low-temperature adsorption decolorization step for degummed oat oil: cooling the degummed oat oil to 35-45℃, adding a composite adsorbent at a concentration of 1%-3% of the mass of the degummed oat oil, and adsorbing for 30-60 minutes under stirring conditions; the composite adsorbent is a mixture of activated clay and food-grade silica gel in a mass ratio of 1:0.5 to 1:2; after adsorption, the mixture is filtered and separated to obtain decolorized oat oil.

4. The method for hot air pretreatment to extract oat oil as described in claim 3, characterized in that, It also includes a step of low-temperature vacuum deodorization of bleached oat oil: the bleached oat oil is heated to 120-150℃ and deodorized for 1-3 hours under vacuum conditions with an absolute pressure of less than 200Pa by introducing direct steam; during the deodorization process, a dry condensation system is used to capture volatile substances; after deodorization, the oil is cooled to 50-60℃ under vacuum conditions to obtain the finished oat oil.

5. The method for hot air pretreatment to extract oat oil as described in claim 4, characterized in that, The process also includes a step of magnetic field-assisted adsorption purification of the finished oat oil: cooling the obtained finished oat oil to 25-35℃, adding a magnetic adsorbent at a concentration of 0.5%-1.5% of the mass of the finished oat oil, and adsorbing for 20-40 minutes under stirring conditions; the magnetic adsorbent is Fe3O4 magnetic microspheres coated with silica gel with a particle size of 50-200nm; after adsorption treatment, the magnetic adsorbent is recovered by a magnetic field separation device, and then the oil is precisely filtered through a 0.22μm filter membrane to obtain high-purity oat oil.

6. The method for extracting oat oil using hot air pretreatment as described in claim 1, characterized in that, The process also includes a step of classifying and utilizing the second residue obtained in step d: adjusting the moisture content of the second residue to 8%-12%, and extruding and puffing it using an extruder at 120-150℃ and 2-4MPa to obtain puffed material; mixing the puffed material with a citrate buffer solution of pH 4.5-5.5 at a material-to-liquid ratio of 1:8 to 1:12, adding cellulase and β-glucanase at 0.1%-0.3% and 0.05%-0.15% of the mass of the puffed material, respectively, and enzymatically hydrolyzing at 45-55℃ for 2-4 hours; after enzymatic hydrolysis, filtering and separating, concentrating and spray-drying the filtrate to obtain oat β-glucan, and drying and pulverizing the filter residue to obtain oat dietary fiber powder.

7. The method for hot air pretreatment to extract oat oil as described in claim 1, characterized in that, The ethanol vapor mentioned in step b is recycled ethanol that has been vaporized and reused. The recycled ethanol comes from the ethanol recovered by vacuum distillation in step e, which is dehydrated to a water content of 3%-5% by anhydrous sodium sulfate fixed bed, while adsorbing and removing pigments and oil decomposition products entrained in the recycled ethanol. Then, it is vaporized into ethanol vapor at 115-125℃ and recycled for the negative pressure flash evaporation treatment in step b.

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