Method for extracting fatty acid from refined mixed oil

Abstract

The invention relates to the technical field of grease processing, and discloses a method for extracting fatty acid from refined mixed oil, which comprises the steps of pretreatment, enzymolysis reaction, demulsification separation, centrifugal extraction, solvent recovery, molecular distillation purification and finished product treatment. High-efficiency extraction of fatty acid is realized through pretreatment and impurity removal of activated clay, mild enzymolysis of immobilized lipase and selective extraction of a composite extractant in combination with solvent recovery through reduced pressure distillation and precise purification through molecular distillation. The method has the advantages of simple process, moderate equipment investment, fatty acid extraction rate greater than or equal to 92%, fatty acid purity greater than or equal to 98.5%, low energy consumption, no generation of a large amount of acid-alkali wastewater, light product color and small peculiar smell, can meet the requirements of food, medicine and other high-end fields, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of oil processing technology, specifically a method for extracting fatty acids from refined blended oils. Background Technology

[0002] Refined blended oils are mixtures of various oils obtained through refining processes such as degumming, deacidification, decolorization, and deodorization during oil processing. Their composition is complex, containing not only triglycerides, diglycerides, and monoglycerides, but also a certain amount of free fatty acids. These fatty acids have extremely high economic value and are widely used in the food, pharmaceutical, cosmetic, feed, and industrial sectors. Currently, the main methods for extracting fatty acids from refined blended oils include saponification acid hydrolysis, enzymatic hydrolysis, high-pressure hydrolysis, urea inclusion complexation, low-temperature crystallization, and distillation. However, existing methods generally have many drawbacks.

[0003] Saponification acid hydrolysis is a mature and widely applicable technology, but the process is long, consumes a lot of strong acids and bases, generates a lot of saline wastewater, puts great pressure on the environment, and the acid and alkaline conditions can easily lead to the isomerization of unsaturated fatty acids, affecting product quality. Enzymatic hydrolysis has mild reaction conditions and is environmentally friendly, but lipases are expensive, the reaction rate is slow, and the process control requirements are strict, making it difficult to achieve large-scale industrial production.

[0004] In response to the problems of low extraction efficiency, insufficient product purity, high energy consumption, heavy environmental pressure, and large equipment investment in existing technologies, there is an urgent need to develop a method for extracting fatty acids from refined blended oils that is simple, efficient, environmentally friendly, produces high-purity products, and is suitable for large-scale industrial applications. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for extracting fatty acids from refined blended oils. This method has the characteristics of simple process, high extraction efficiency, high product purity, low energy consumption, and environmental friendliness. It can achieve efficient separation and extraction of fatty acids and meet the needs of industrial production and high-end applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for extracting fatty acids from refined blended oils, comprising the following steps:

[0007] (1) Pretreatment: The refined mixed oil to be treated (acid value 2-10 mg KOH / g, specifically vegetable oil, animal oil or a mixture of vegetable and animal oils to ensure the compatibility of raw materials) is uniformly introduced into a closed pretreatment tank. Pretreated activated clay is added at a ratio of 0.5%-2% of the mass of the refined mixed oil (pretreatment process: constant temperature drying at 105-110℃ for 2-3 hours to remove moisture and adsorbed volatile impurities, followed by pulverization to 100-200 mesh to increase the specific surface area and improve the adsorption effect); the stirring device is started and the stirring speed is controlled at 200-300 r. / min (to avoid local material agglomeration and ensure full contact between the clay and the oil phase), heat to 60-80℃ (this temperature can ensure decolorization and impurity removal efficiency while preventing slight oxidation of the oil), and decolorize by stirring at a constant temperature for 30-60 minutes, during which the color change of the system is monitored in real time; after stirring, the material is filtered under pressure through a plate and frame filter press (filtration accuracy 0.1μm) to completely remove the activated clay (adsorbing pigments, mechanical impurities and trace amounts of colloids) and unreacted solid particles. The clear liquid after filtration is collected, which is the refined mixed oil, ensuring that the subsequent enzymatic hydrolysis reaction is not interfered with by impurities; (2) Enzymatic hydrolysis reaction: The refined mixed oil obtained in step (1) is pumped into a constant temperature enzymatic hydrolysis reactor. Deionized water is added at a ratio of 1-3 times the mass of the refined mixed oil (to control the oil-water ratio, provide a suitable system environment for the enzymatic hydrolysis reaction, and avoid excessive concentration of the oil phase affecting the reaction rate). Citric acid or phosphoric acid aqueous solution with a concentration of 0.1-0.5 mol / L (both reagents are food grade and can accurately adjust the pH value) is slowly added to the system to adjust the pH value to 4.5-6.0 (matching the optimal reaction pH range of immobilized lipase). Then, at a ratio of 0.2%-0.8% of the mass of the refined mixed oil, the water is added to the system. For example, add immobilized lipase (enzyme activity ≥10000U / g; immobilization can enable enzyme reuse, reduce production costs, and facilitate separation from materials after reaction); seal the reactor, control the reaction temperature at 45-55℃ (mild temperature conditions to avoid lipase inactivation and oxidative isomerization of unsaturated fatty acids), and stir at 150-250r / min (uniform stirring ensures sufficient oil-water contact and improves enzymatic hydrolysis efficiency). Perform constant-temperature enzymatic hydrolysis for 4-8 hours, taking samples periodically to detect the free fatty acid content of the system. Stop the reaction after the content stabilizes to obtain an enzymatic hydrolysate containing fatty acids, glycerol, water, and trace amounts of enzyme. (3) Demulsification and separation: Add polyoxyethylene polyoxypropylene ether block copolymer demulsifier to the enzymatic hydrolysate obtained in step (2) at a ratio of 0.3%-0.8% of the hydrolysate mass (this demulsifier has strong surface activity, can quickly destroy the oil-water interface film, and has good biodegradability with no residue); start stirring, control the temperature at 50-60℃ (to enhance the activity of the demulsifier and accelerate the stratification), and the stirring speed at 100-200 r / min (low-speed stirring to avoid secondary emulsification), and stir at a constant temperature for 10-20 min to allow the demulsifier to fully play its role; then introduce the material into a high-speed centrifuge for separation. The centrifuge operates at a speed of 8000-10000 r / min (high-intensity centrifugal force for rapid three-phase separation) and a centrifugation time of 15-30 min. After centrifugation, the system is allowed to stand for 5 min, and naturally separates into three layers: the upper layer is the crude fatty acid phase (mainly containing free fatty acids and a small amount of oil impurities), the middle layer is the glycerol aqueous phase (containing glycerol, water, and trace amounts of enzymes), and the lower layer is a small amount of impurity precipitate (unfiltered solid particles and enzyme carriers). The upper crude fatty acid phase is precisely collected through the separator's built-in flow guiding device, and the middle glycerol aqueous phase can be recovered and purified to achieve resource recycling. (4) Centrifugal extraction: The crude fatty acid phase collected in step (3) is introduced into a centrifugal extractor (continuous operation, suitable for industrial production). A composite extractant (made of ethylene propanol and a weakly alkaline aqueous solution in a volume ratio of 55:45-65:35, wherein the weakly alkaline aqueous solution is a sodium bicarbonate aqueous solution with a mass fraction of 0.5%-1.5%) is added at a ratio of 1-2 times the mass of the crude fatty acid phase. Ethyl propanol can enhance the solubility of fatty acids, and sodium bicarbonate aqueous solution can adjust the pH of the system, improve the selectivity of separation between fatty acids and impurities, and the two have no adverse reactions when combined. (Toxic and harmful substances are generated); adjust the extraction temperature to 30-40℃ (this temperature range ensures the selectivity of the extractant and avoids the volatilization of fatty acids), start the extractor, and control the extraction time to 5-10 minutes (to ensure extraction balance). During the extraction process, centrifugal force is used to accelerate the separation of the oil and water phases. After standing for 2-3 minutes, the system is divided into an organic phase (containing fatty acids and extractant) and an aqueous phase (containing polar impurities and trace amounts of glycerol). The organic phase (target phase) is accurately collected through the layered collection device of the extractor, and the aqueous phase can be treated to recover trace amounts of fatty acids, reducing losses. (5) Solvent recovery: Pump the organic phase collected in step (4) into a vacuum distillation column (a packing layer is set in the column to improve separation efficiency), close the top valve of the column, start the vacuum system, adjust the vacuum degree to 0.08-0.095MPa (the low pressure environment can reduce the boiling point of the extractant and avoid the oxidation of fatty acids caused by high temperature), raise the temperature to 70-90℃ (at this temperature the extractant can evaporate quickly and the fatty acids do not evaporate), and distill under vacuum at a constant temperature for 1-2 hours; during the distillation process, the condenser at the top of the column condenses the evaporated extractant vapor into liquid and introduces it into the solvent recovery tank. After the purity is tested to be ≥98%, it can be directly recycled for the next batch of centrifugal extraction process, which greatly reduces solvent consumption and environmental pressure; the viscous liquid remaining at the bottom of the distillation column is the desolventized crude fatty acid, with no risk of solvent residue; (6) Molecular distillation purification: The desolventized crude fatty acid obtained in step (5) is introduced into a short-path molecular distillation apparatus (the distance between the evaporation surface and the condensation surface is 20-50 mm, which shortens the molecular movement distance and improves the separation efficiency). The equipment is started and various parameters are precisely controlled: distillation temperature 120-160℃ (adjusted according to the molecular weight of fatty acids to ensure that the target fatty acid is volatilized and high-boiling-point impurities are not volatilized), vacuum degree 1-5Pa (extremely high vacuum degree, further reducing the boiling point of fatty acids and avoiding degradation), feed rate 50-100kg / h (uniform feed to ensure uniform distribution of materials on the evaporation surface), and scraper rotation speed 300-500r / min (the scraper device makes the material form a uniform liquid film and increases the evaporation area). Under the above conditions, low-molecular-weight off-odor substances (such as short-chain aldehydes and ketones), residual trace impurities and some high-boiling-point components (such as unhydrolyzed oils) in the crude fatty acid are retained, the target fatty acid molecules evaporate rapidly and condense on the condensation surface, and the condensed liquid is collected to obtain high-purity fatty acid products, which effectively improves product quality and purity. Furthermore, in step (1), the activated clay is pretreated, specifically by drying the activated clay at 105-110℃ for 2-3 hours and pulverizing it to 100-200 mesh.

[0008] Further, in step (1), the refined blended oil is a refined blended vegetable oil, a refined blended animal oil, or a refined blended vegetable and animal oil, and its acid value is 2-10 mg KOH / g.

[0009] Furthermore, in step (2), the lipase is an immobilized lipase with an enzyme activity ≥10000U / g; the pH value is adjusted by using an aqueous solution of citric acid or phosphoric acid with a concentration of 0.1-0.5mol / L.

[0010] Further, in step (3), the demulsifier is a polyoxyethylene polyoxypropylene ether block copolymer, the centrifugation speed is 8000-10000 r / min, and the centrifugation time is 15-30 min.

[0011] Further, in step (4), the composite extractant is composed of ethanol and a weakly alkaline aqueous solution in a volume ratio of 55:45-65:35, and the weakly alkaline aqueous solution is a sodium bicarbonate aqueous solution with a mass fraction of 0.5%-1.5%.

[0012] Furthermore, in step (5), the vacuum distillation time is 1-2 hours.

[0013] Furthermore, in step (6), the molecular distillation equipment is a short-path molecular distillation apparatus, and the distance between the evaporation surface and the condensation surface is 20-50 mm.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention employs a core process combining enzymatic hydrolysis and centrifugal extraction. Enzymatic hydrolysis efficiently catalyzes the hydrolysis of triglycerides in refined mixed oils to generate free fatty acids under mild conditions. Centrifugal extraction uses a composite extractant with high selectivity for fatty acids. Further purification by molecular distillation effectively removes impurities and harmful substances. The final fatty acid product has a purity of ≥98.5% and an extraction rate of ≥92%, which is far superior to existing traditional methods. 2. The enzymatic hydrolysis reaction is mild, requiring no high temperature or high pressure, which significantly reduces energy consumption, solvent waste, and environmental pollution. The entire process does not use large amounts of strong acids or alkalis, generates little wastewater, and simplifies subsequent treatment, thus reducing environmental pressure. The mild process conditions effectively prevent the oxidation, decomposition, and isomerization of unsaturated fatty acids, preserving the natural characteristics of fatty acids. The product has a light color, minimal odor, and stable quality, meeting the application needs of high-end fields such as food and medicine. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Polyoxyethylene polyoxypropylene ether block copolymer (Poloxamer 188, analytical grade), Nanjing Well Pharmaceutical Group.

[0017] Test methods The test data for the following examples and comparative cases were all tested using the following standard methods. All tests were repeated three times, and the average value was taken as the final result to ensure the data was true and reliable. 1. Detection method for fatty acid purity: Preparation of fatty acid methyl esters: Weigh 200 mg of sample into a 50 mL centrifuge tube, add 4 mL of methanol-potassium hydroxide solution (0.5 mol / L), vortex mix for 1 min, react in a 60 °C water bath for 15 min, cool, add 5 mL of n-hexane, vortex extract for 2 min, centrifuge at 8000 r / min for 5 min, and take the upper n-hexane phase (containing fatty acid methyl ester) for later use; Chromatographic conditions: Column temperature program: initial temperature 60℃, hold for 2 min, increase to 240℃ at 5℃ / min, hold for 15 min; injection port temperature 250℃, detector temperature 260℃; carrier gas: nitrogen (purity ≥99.999%), flow rate 1.0 mL / min; split ratio 100:1, injection volume 1 μL; Quantitative calculation: The area normalization method is used, and the percentage of the peak area of ​​each fatty acid methyl ester to the total peak area is used as the purity of the corresponding fatty acid. The sum of the purities of all fatty acids is the total purity of the product.

[0018] 2. Fatty acid extraction rate calculation: Extraction rate = (Final product quality × Product purity) / (Raw material mixed oil quality × Total fatty acid content of raw materials) × 100%, Total fatty acid quality (kg) = Raw material mixed oil quality (kg) × [(Acid value × 56.11) + (Saponification value - Acid value) × M / 1000] / 1000 Where: 56.11 is the molar mass of potassium hydroxide (g / mol); M is the average molar mass of fatty acids in the raw material mixed oil (g / mol, estimated according to the fatty acid composition of common oils, such as 282 g / mol for vegetable oil and 286 g / mol for animal oil, and the mixed oil is calculated by weighting the proportions); Data requirements: The determination of total fatty acid content of raw materials needs to be repeated 3 times, and the average value is used for calculation.

[0019] 3. Auxiliary evaluation indicators: Color was measured according to GB / T22460-2008, and sensory odor was scored by 5 blind judges (out of 10 points, the higher the score, the milder the odor).

[0020] Example 1 A method for extracting fatty acids from refined blended oils, comprising the following steps: (1) Pretreatment: 100 kg of refined vegetable oil mixture (acid value 5.2 mg KOH / g3) was introduced into a pretreatment tank, and 1 kg of activated clay (1% of the oil weight; dried at 105℃ for 2 h and pulverized to 150 mesh) was added. The mixture was stirred and decolorized for 45 min at a temperature of 70℃ and a stirring rate of 250 r / min. Then it was filtered through a plate and frame filter press to obtain 98.5 kg of refined mixed oil. (2) Enzymatic hydrolysis: 98.5 kg of refined mixed oil was introduced into the enzymatic hydrolysis reactor, and 200 kg of deionized water (twice the weight of oil) was added. The pH of the system was adjusted to 5.0 with 0.3 mol / L citric acid aqueous solution. Then, 0.5 kg of immobilized lipase (0.5% of the weight of oil, enzyme activity 12000 U / g) was added. The enzyme was hydrolyzed at a constant temperature of 50℃ and a stirring rate of 200 r / min for 6 h to obtain the hydrolysate. (3) Demulsification and separation: Add 0.8 kg of polyoxyethylene polyoxypropylene ether block copolymer demulsifier (accounting for 0.5% of the weight of the enzymatic hydrolysate) to the enzymatic hydrolysate, stir for 15 min at a temperature of 55℃ and a stirring speed of 150 r / min, and then introduce the enzymatic hydrolysate into a centrifuge and centrifuge at a speed of 9000 r / min and a centrifugation time of 20 min, and collect 42.3 kg of the upper crude fatty acid phase; (4) Centrifugal extraction: 42.3 kg of crude fatty acid phase was introduced into a centrifugal extractor, and 60 kg of composite extractant (1.4 times the weight of oil; ethanol and 1.0% sodium bicarbonate aqueous solution were mixed at a volume ratio of 60:40) was added. The extraction temperature was adjusted to 35℃ and the extraction time was 8 min. After standing and layering, 58.7 kg of organic phase was collected. (5) Solvent recovery: 58.7 kg of organic phase was introduced into a vacuum distillation column and distilled under vacuum conditions of 0.09 MPa, 80 °C and 1.5 h to recover 57.2 kg of composite extractant and obtain 39.8 kg of desolventized crude fatty acid; (6) Molecular distillation purification: 39.8 kg of desolventized crude fatty acid was introduced into a short-path molecular distillation apparatus. The distillation temperature was controlled at 140℃, the vacuum degree was 3Pa, the feed rate was 80 kg / h, the scraper speed was 400 r / min, and the distance between the evaporation surface and the condensation surface was 30 mm. Molecular distillation purification was carried out to obtain 38.6 kg of high-purity fatty acid product. (7) Finished product processing: Cool 38.6 kg of high-purity fatty acid product to 55°C, filter it through a precision filter, and then transfer it into the finished product storage tank.

[0021] The fatty acid product obtained in this embodiment has a purity of 98.8%, an extraction rate of 92.5%, a color of Lovibond Red value of 1.2, and a sensory odor score of 9.0.

[0022] Example 2 A method for extracting fatty acids from refined blended oils, comprising the following steps: (1) Pretreatment: 200 kg of refined mixed animal and vegetable oil (acid value 8.6 mg KOH / g3) was introduced into a pretreatment tank, and 3 kg of activated clay (1.5% of the oil weight1; dried at 110℃ for 2.5 h and pulverized to 200 mesh2) was added. The mixture was stirred and decolorized for 30 min at 80℃ and 300 r / min. Then it was filtered through a plate and frame filter press to obtain 196.2 kg of refined mixed oil. (2) Enzymatic hydrolysis reaction: 196.2 kg of refined mixed oil was introduced into the enzymatic hydrolysis reactor, and 500 kg of deionized water (2.5 times the weight of oil) was added. The pH of the system was adjusted to 5.5 with 0.5 mol / L phosphoric acid aqueous solution. Then 1.2 kg of immobilized lipase (0.6% of the weight of oil, enzyme activity 15000 U / g) was added. The enzyme was hydrolyzed at a constant temperature of 55℃ and a stirring rate of 250 r / min for 4 h to obtain the enzymatic hydrolysate. (3) Demulsification and separation: Add 2.0 kg of polyoxyethylene polyoxypropylene ether block copolymer demulsifier (accounting for 0.8% of the weight of the enzymatic hydrolysate) to the enzymatic hydrolysate, stir for 10 min at a temperature of 60℃ and a stirring speed of 200 r / min, and then introduce the enzymatic hydrolysate into a centrifuge and centrifuge at a speed of 10000 r / min and a centrifugation time of 15 min, and collect 88.5 kg of the upper crude fatty acid phase; (4) Centrifugal extraction: 88.5 kg of crude fatty acid phase was introduced into a centrifugal extractor, and 170 kg of composite extractant (1.9 times the weight of oil; ethanol and 1.5% sodium bicarbonate aqueous solution were mixed at a volume ratio of 65:35) was added. The extraction temperature was adjusted to 40℃ and the extraction time was 5 min. After standing and layering, 156.3 kg of organic phase was collected. (5) Solvent recovery: 156.3 kg of organic phase was introduced into a vacuum distillation column and distilled under vacuum conditions of 0.095 MPa, 90 °C and 1 h to recover 153.5 kg of composite extractant and obtain 82.6 kg of desolventized crude fatty acid. (6) Molecular distillation purification: 82.6 kg of desolventized crude fatty acid was introduced into a short-path molecular distillation apparatus. The distillation temperature was controlled at 160℃, the vacuum degree was 5 Pa, the feed rate was 100 kg / h, the scraper speed was 500 r / min, and the distance between the evaporation surface and the condensation surface was 50 mm. Molecular distillation purification was carried out to obtain 80.2 kg of high-purity fatty acid product. (7) Finished product processing: Cool 80.2 kg of high-purity fatty acid product to 60°C, filter it through a precision filter, and then transfer it into the finished product storage tank.

[0023] The fatty acid product obtained in this embodiment has a purity of 99.1%, an extraction rate of 93.2%, a color of Lovibond Red value of 1.0, and a sensory odor score of 9.2.

[0024] Example 3 A method for extracting fatty acids from refined blended oils, comprising the following steps: (1) Pretreatment: 150 kg of refined animal oil mixture (acid value 3.8 mg KOH / g3) was introduced into a pretreatment tank, and 0.75 kg of activated clay (0.5% of the oil weight1; dried at 105℃ for 3 h and pulverized to 100 mesh2) was added. The mixture was stirred and decolorized for 60 min at a temperature of 60℃ and a stirring rate of 200 r / min. Then it was filtered through a plate and frame filter press to obtain 148.8 kg of refined mixed oil. (2) Enzymatic hydrolysis reaction: 148.8 kg of refined mixed oil was introduced into the enzymatic hydrolysis reactor, and 200 kg of deionized water (1.3 times the weight of oil) was added. The pH of the system was adjusted to 4.5 with 0.1 mol / L citric acid aqueous solution. Then, 0.3 kg of immobilized lipase (0.2% of the weight of oil, enzyme activity 10000 U / g) was added. The enzyme was hydrolyzed at a constant temperature of 45℃ and a stirring rate of 150 r / min for 8 h to obtain the enzymatic hydrolysate. (3) Demulsification and separation: Add 0.6 kg of polyoxyethylene polyoxypropylene ether block copolymer demulsifier (accounting for 0.3% of the weight of the enzymatic hydrolysate) to the enzymatic hydrolysate, stir for 20 min at a temperature of 50℃ and a stirring speed of 100 r / min, and then introduce the enzymatic hydrolysate into a centrifuge and centrifuge at a speed of 8000 r / min and a centrifugation time of 30 min, and collect 62.4 kg of the upper crude fatty acid phase; (4) Centrifugal extraction: 62.4 kg of crude fatty acid phase was introduced into a centrifugal extractor, and 62.4 kg of composite extractant (oil weight 1:1; ethanol and 0.5% sodium bicarbonate aqueous solution were mixed at a volume ratio of 55:45) was added. The extraction temperature was adjusted to 30℃ and the extraction time was 10 min. After standing and layering, 78.6 kg of organic phase was collected. (5) Solvent recovery: 78.6 kg of organic phase was introduced into a vacuum distillation column and distilled under vacuum conditions of 0.08 MPa, 70 °C and 2 h to recover 75.8 kg of composite extractant and obtain 58.9 kg of desolventized crude fatty acid. (6) Molecular distillation purification: 58.9 kg of desolventized crude fatty acid was introduced into a short-path molecular distillation apparatus. The distillation temperature was controlled at 120℃, the vacuum degree was 1 Pa, the feed rate was 50 kg / h, the scraper speed was 300 r / min, and the distance between the evaporation surface and the condensation surface was 20 mm. Molecular distillation purification was carried out to obtain 57.2 kg of high-purity fatty acid product. (7) Finished product processing: Cool 57.2 kg of high-purity fatty acid product to 50°C, filter it through a precision filter, and then transfer it into the finished product storage tank.

[0025] The fatty acid product obtained in this embodiment has a purity of 98.6%, an extraction rate of 92.1%, a Lovibond Red value of 1.3, and a sensory odor score of 8.8.

[0026] Comparative Example 1 (Traditional Saponification Acid Hydrolysis Method) The specific steps of using the existing traditional saponification acid hydrolysis method are as follows: (1) Take 100 kg of refined vegetable oil mixture (same as the raw material in Example 1, acid value 5.2 mg KOH / g), put it into the reaction vessel, add 200 kg of sodium hydroxide aqueous solution with a mass fraction of 10%, and saponify for 2 h at 85℃ and 200 r / min to obtain saponified liquid; (2) Slowly add 30% hydrochloric acid aqueous solution to the saponification solution, adjust the pH to 2.0, stir for 30 min, let stand to separate the layers, and collect the upper crude fatty acid phase; (3) The crude fatty acid phase is washed three times with deionized water (each time the amount of water added is equal to the weight of the crude fatty acid) until the pH of the washing water is 6.5-7.0. The water is then removed by drying at 105℃ for 2 hours to obtain the fatty acid product.

[0027] Testing revealed that the purity of this comparative product was 89.2%, the extraction rate was 78.5%, the color was Lovibond Red value of 5.2, and the sensory odor score was 6.2. All indicators were significantly lower than those of the embodiments of this invention.

[0028] Comparative Example 2 (Traditional Single Enzymatic Hydrolysis Method) The traditional enzymatic hydrolysis method is adopted, and the specific steps are as follows (the pretreatment, enzymatic hydrolysis, and demulsification steps are the same as in Example 1, and the subsequent steps are simplified): (1) Pretreatment: Same as step (1) in Example 1, to obtain 98.5 kg of refined mixed oil; (2) Enzymatic hydrolysis: Same as step (2) in Example 1, to obtain the enzymatic hydrolysate; (3) Demulsification and separation: Same as step (3) in Example 1, collect 42.3 kg of crude fatty acid phase; (4) Finished product processing: The crude fatty acid phase is distilled under reduced pressure at 0.09 MPa and 100℃ for 1 h to remove moisture and a small amount of low molecular weight impurities. After cooling to 55℃, it is filtered to obtain fatty acid products.

[0029] The comparative product tested showed a purity of 92.3%, an extraction rate of 85.1%, a Lovibond red value of 2.8, and a sensory odor score of 7.5, which are lower than those of the embodiments of the present invention.

[0030] In summary, Examples 1-3 demonstrate that immobilized enzymatic hydrolysis is mild and efficient, effectively catalyzing the hydrolysis of triglycerides into fatty acids; the composite extractant exhibits strong selectivity for fatty acids, removing impurities such as glycerol and colloids; and molecular distillation further removes low / high boiling point impurities, resulting in a final purity ≥98.6% and an extraction rate ≥92.1%.

[0031] Comparative Example 1: The strong acid and alkaline environment caused some fatty acids to isomerize and degrade, and without precise purification steps, there were many impurities remaining, resulting in significantly lower purity and extraction rate (only 89.2% and 78.5%, respectively). Comparative Example 2: Lacking complex extraction and molecular distillation, the crude fatty acids contained impurities such as glycerol and unhydrolyzed oils. Although the purity (92.3%) and extraction rate (85.1%) were better than Comparative Example 1, they were far inferior to the Example.

[0032] Differences in color and odor (product quality advantages) Examples 1-3: Pretreatment with activated clay for decolorization + molecular distillation to remove low-molecular-weight odor substances (aldehydes and ketones), with a gentle process avoiding fatty acid oxidation; color red value only 1.0-1.3 (light), odor score 8.8-9.2 (slight / no odor). Comparative Example 1: Strong acid-base reaction produces byproducts, and no decolorization or deodorization steps are performed; color red value 5.2 (dark), odor score 6.2 (obvious odor). Comparative Example 2: Decolorization only through pretreatment, without molecular distillation for deodorization; color red value 2.8 (relatively dark), odor score 7.5 (slight odor).

[0033] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0035] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A method of extracting fatty acids from a refined mixed oil, characterized by, The method comprises the following steps: (1) Pretreatment: introducing refined mixed oil into a pretreatment tank, adding 0.5%-2% of activated clay by mass of the refined mixed oil, stirring and decolorizing at a temperature of 60-80℃ and a stirring speed of 200-300 r / min for 30-60 min, and removing the activated clay and mechanical impurities by filtration to obtain refined mixed oil; (2) Enzymatic reaction: introducing the refined mixed oil into an enzymatic reaction kettle, adding 1-3 times of deionized water by mass of the refined mixed oil, adjusting the pH value of the system to 4.5-6.0, adding 0.2%-0.8% of lipase by mass of the refined mixed oil, and carrying out constant-temperature enzymatic reaction at a temperature of 45-55℃ and a stirring speed of 150-250 r / min for 4-8 h to obtain an enzymatic hydrolysate; (3) Demulsification and separation: adding 0.3%-0.8% of a demulsifier by mass of the enzymatic hydrolysate to the enzymatic hydrolysate, stirring at a temperature of 50-60℃ and a stirring speed of 100-200 r / min for 10-20 min, and collecting a crude fatty acid phase after centrifugal separation; (4) Centrifugal extraction: introducing the crude fatty acid phase into a centrifugal extractor, adding 1-2 times of a composite extractant by mass of the crude fatty acid phase, and carrying out extraction at a temperature of 30-40℃ for 5-10 min, and collecting an organic phase after static layering; (5) Solvent recovery: introducing the organic phase into a vacuum distillation column, carrying out vacuum distillation at a vacuum degree of 0.08-0.095 MPa and a temperature of 70-90℃ for 1-2 h to recover the composite extractant, and obtaining a desolventized crude fatty acid; (6) Molecular distillation purification: introducing the desolventized crude fatty acid into a molecular distillation device, and carrying out molecular distillation purification at a distillation temperature of 120-160℃, a vacuum degree of 1-5 Pa, a feeding speed of 50-100 kg / h, and a scraper rotating speed of 300-500 r / min to obtain a high-purity fatty acid product.

2. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (1), the activated clay is pretreated by drying at 105-110℃ for 2-3 h and crushing to 100-200 meshes.

3. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (1), the refined mixed oil is a plant oil refined mixed oil, an animal oil refined mixed oil, or a plant and animal oil refined mixed oil, and has an acid value of 2-10 mgKOH / g.

4. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (2), the lipase is an immobilized lipase with an enzyme activity of ≥10000 U / g, and the pH value is adjusted by using a citric acid or phosphoric acid aqueous solution with a concentration of 0.1-0.5 mol / L.

5. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (3), the demulsifier is a polyoxyethylene polyoxypropylene ether block copolymer, the centrifugal separation rotating speed is 8000-10000 r / min, and the centrifugal separation time is 15-30 min.

6. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (4), the composite extractant is composed of ethylene propylene alcohol and a weak alkaline aqueous solution at a volume ratio of 55:45-65:35, and the weak alkaline aqueous solution is a sodium bicarbonate aqueous solution with a mass fraction of 0.5%-1.5%.

7. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (5), the vacuum distillation time is 1-2 h.

8. The method of extracting fatty acids from refined blended oil according to claim 1, characterized by, In the step (6), the molecular distillation device is a short-path molecular distillation instrument, and the distance between the evaporation surface and the condensation surface is 20-50 mm.