A Low-Temperature Deacidification and Purification Method for Peanut Oil Refining

Abstract

This application relates to the field of food processing technology, specifically disclosing a method for refining peanut oil through low-temperature deacidification and purification. The method involves: cold-pressing peanut raw materials at low temperature, followed by centrifugal separation to obtain a first crude oil; then performing ultrasonic-assisted degumming, low-temperature crystallization dewaxing, and centrifugation to remove wax to obtain a second crude oil; adding a magnetic adsorbent to the second crude oil, stirring and adsorbing it in an inert gas atmosphere, and then removing the magnetic adsorbent through magnetic separation by increasing a magnetic field to obtain a pretreated crude oil; finally, subjecting the pretreated crude oil to low-temperature distillation for deacidification and deodorization to obtain the final product. This method achieves a high deacidification rate and maximum retention of nutrients under consistently low-temperature conditions, ensuring the rich flavor of the finished peanut oil.

Description

Technical Field

[0001] This application relates to the field of food processing technology, and more specifically, it relates to a method for refining peanut oil by low-temperature deacidification and purification. Background Technology

[0002] Peanut oil is highly favored for its rich flavor and abundant nutrients, but impurities such as free fatty acids, phospholipids, and pigments in crude oil must be removed through refining. Deacidification is the core step in refining, directly affecting the quality, yield, and nutrient retention of the finished oil.

[0003] Currently, the deacidification and purification of peanut oil mainly employs chemical refining and traditional physical refining methods. Chemical refining often involves adding strong alkalis such as sodium hydroxide to neutralize free fatty acids. While this lowers the acid value, it consumes large amounts of chemical reagents, generates significant amounts of soap-containing wastewater, polluting the environment. Furthermore, excessive alkali can saponify neutral oils, causing losses and damaging antioxidants such as vitamin E and natural aroma components in peanut oil. Traditional physical refining requires high-temperature, high-vacuum conditions to remove free fatty acids. This process demands high precision and is difficult to control. High temperatures can also cause the volatilization of aroma compounds such as pyrazines in peanut oil, destroying its natural flavor and original rich aroma. It may also generate trans fatty acids, reducing the product's nutritional value and food safety.

[0004] Regarding the aforementioned technologies, the inventors have found that in recent years, in order to improve the deacidification effect of peanut oil, those skilled in the art have mostly begun to study low-temperature technologies such as solvent extraction deacidification, enzymatic deacidification, and membrane separation deacidification, but all of these have significant limitations. Solvent extraction methods have a high risk of residual solvent and high recovery costs; although enzymatic methods are mild, lipases are expensive, reaction times are long, and process control is complex, making large-scale application difficult; membrane separation methods are limited by membrane selectivity and flux, and the deacidification efficiency is difficult to meet industrial requirements. None of these methods can simultaneously achieve low-temperature, high-efficiency deacidification and preservation of nutritional flavor. Summary of the Invention

[0005] In order to improve the deacidification and purification effect in the peanut oil refining process and retain more of the nutrients and rich flavor of peanut oil, this application provides a low-temperature deacidification and purification method for peanut oil refining.

[0006] In the first aspect, this application provides a method for refining peanut oil through low-temperature deacidification and purification, employing the following technical solution:

[0007] A method for refining peanut oil by low-temperature deacidification and purification includes the following steps:

[0008] S1: Peanuts are removed from their red skins to obtain peanut kernels, which are then crushed to obtain raw peanuts.

[0009] S2: The peanut raw material is subjected to low-temperature cold pressing and centrifugation to obtain the first crude oil;

[0010] S3: The first crude oil is subjected to ultrasonic-assisted degumming, then cooled to -5 to 0℃ for low-temperature crystallization dewaxing, and centrifuged to remove the wax to obtain the second crude oil;

[0011] S5: Add a magnetic adsorbent to the second crude oil, stir and adsorb it in an inert gas atmosphere, and then remove the magnetic adsorbent by magnetic separation by increasing the magnetic field to obtain the pretreated crude oil.

[0012] S5: The pretreated crude oil is subjected to low-temperature distillation deacidification in an inert gas atmosphere at a distillation temperature of 110-130℃, and then vacuum deodorization is carried out at 140-150℃ and a vacuum degree of 0.005-0.008MPa to obtain the final product.

[0013] By adopting the above technical solution, the peanut oil refining process of this application achieves low temperature throughout the entire process, with cold pressing at ≤40℃, adsorption at 50-60℃, distillation at 110-130℃, and deodorization at 140-150℃. This effectively prevents the reduction of peanut oil flavor caused by the formation of trans fatty acids and the volatilization of aroma substances due to high temperatures. It completely eliminates the use of strong alkalis such as sodium hydroxide in traditional chemical refining, eliminates the generation of soap-containing wastewater from the source, and avoids the saponification reaction between strong alkalis and neutral triglycerides. The total oil yield is effectively improved compared with chemical refining.

[0014] This application introduces a magnetic adsorbent before low-temperature deacidification. This allows for the pre-removal of most free fatty acids before distillation, reducing the acid load on the distillation column. This means subsequent low-temperature distillation only needs to process the remaining small amount of fatty acids, achieving effective deacidification in a shorter time while maintaining a distillation temperature of 110-130℃, significantly reducing the volatilization loss of pyrazine-based characteristic flavor compounds. Furthermore, the magnetic adsorbent not only adsorbs free fatty acids but also simultaneously removes non-volatile bound fatty acids, trace amounts of phospholipid residues, peroxides, and heavy metal ions, overcoming the limitation of low-temperature distillation in removing only volatile impurities. The magnetic adsorbent in this application achieves rapid separation of the adsorbent and oil through an external magnetic field, leaving no filter cake residue and avoiding the entrainment loss of oil in traditional filtration processes.

[0015] Optionally, the preparation method of the magnetic adsorbent includes the following steps:

[0016] FeCl2 and FeCl3 in a molar ratio of 1:(1.8-2.2) were added to water, the pH was adjusted to 10±0.5, and a co-precipitation reaction was carried out in an inert gas atmosphere at 70-80℃. After magnetic separation, washing and drying, Fe3O4 particles were obtained.

[0017] Fe3O4 particles were dispersed in an ethanol-water solution, ultrasonically dispersed, and then hexadecyltrimethylammonium bromide was added. After stirring evenly, tetraethyl orthosilicate was added dropwise, followed by ammonia water. The mixture was stirred at room temperature and then magnetically separated. After washing, the product was dispersed in ethanol, ammonium nitrate was added, and the mixture was refluxed at 55-65℃ to obtain a core-shell structured pre-prepared magnetic adsorbent.

[0018] The pre-made magnetic adsorbent was dispersed in toluene and ultrasonically dispersed. Then, an aqueous ethanol solution containing a silane coupling agent and a long-chain alkyl modifier was added. The mixture was refluxed at 105-115°C under an inert gas atmosphere. After magnetic separation, washing, and drying, the final product was obtained.

[0019] Optionally, the silane coupling agent is selected from aminosilane coupling agents, and the long-chain alkyl reagent is selected from octadecyltrimethoxysilane.

[0020] Optionally, in step S5, the temperature condition for the magnetic adsorbent to adsorb is 50-60℃.

[0021] Optionally, the amount of magnetic adsorbent added is 1-3% of the second crude oil.

[0022] By adopting the above technical solution, using Fe3O4 as the magnetic core, rapid separation between the adsorbent and crude oil can be achieved under low magnetic field strength, without the need for centrifugation or filtration equipment, making it suitable for continuous industrial production; at the same time, it avoids the residue of fine adsorbent particles in the oil, improving the transparency of the finished oil.

[0023] The mesoporous silica shell constructed by the Fe3O4 magnetic core not only effectively isolates the Fe3O4 magnetic core from direct contact with the oil, preventing the dissolution of iron ions and avoiding spoilage of the oil due to catalytic oxidation by metal ions, but also provides a pore confinement effect. In the mesoporous silica layer structure constructed in this application, small molecular weight free fatty acids can enter the pores, while large molecular weight triglycerides and vitamin E are repelled, achieving selective adsorption.

[0024] Furthermore, amino alkaline sites and long-chain alkyl structures were introduced into the outer layer of the magnetic adsorbent through silane grafting, which endowed the magnetic adsorbent with hydrophobicity. This enabled the magnetic adsorbent to form a synergistic dual-site adsorption with the carboxyl groups and carbon chains of fatty acids, resulting in a significantly improved adsorption capacity compared to single activated clay adsorbents.

[0025] Optionally, the peanut raw material undergoes the following pretreatment before low-temperature cold pressing:

[0026] The peanut raw material was sprayed with water and stirred until the moisture content was (17±1)%, then ultrasonically vibrated and dried until the moisture content was (7±1)%, thus obtaining pretreated peanut material.

[0027] By adopting the above technical solution, the moisture content of the peanut raw material obtained after crushing is first adjusted to (17±1)%, followed by wet ultrasonic vibration, which helps to fully soften the peanut cell walls, expand the intercellular spaces, and increase the oil release channels. After ultrasonic vibration, the moisture content is adjusted to (7±1)%, and moderate dehydration makes the cell structure brittle, which facilitates the extraction of oil during subsequent cold pressing, while preventing oil emulsification during the pressing process due to high moisture content. Compared with the traditional cold pressing process, the pretreatment of peanut raw material in this application helps to increase the peanut oil yield under low temperature conditions, and effectively retains volatile aroma precursors in peanuts, such as free amino acids and reducing sugars, avoiding the destruction of flavor substances by high temperature pretreatment.

[0028] Optionally, the peanut raw material is subjected to low-temperature cold pressing at a temperature of 35-40℃ and a pressure of 25-30MPa.

[0029] Secondly, this application provides a peanut oil prepared by the low-temperature deacidification and purification peanut oil refining method of this application.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. Because this application adopts a process that combines magnetic adsorbent pre-deacidification with low-temperature distillation deacidification, a high deacidification rate is achieved under low-temperature conditions throughout the process. This effectively prevents the volatilization of pyrazine flavor substances and the formation of trans fatty acids, and maximizes the retention of heat-sensitive nutrients such as vitamin E and phytosterols, thus ensuring the rich flavor of the finished peanut oil.

[0032] 2. The magnetic adsorbent used in this application can be quickly separated and recovered by an external magnetic field without the need for filtration or centrifugation. It has low energy consumption and no soap-containing wastewater is generated. From low-temperature cold pressing (35-40℃), ultrasonic-assisted degumming, low-temperature crystallization dewaxing to magnetic adsorption and low-temperature distillation deodorization, the entire process does not require strong alkali, organic solvents or high temperature and high pressure. There is no risk of chemical reagent residue or solvent residue. The process control is simple and easy to scale up for production, which meets the requirements of green food processing and clean production. Detailed Implementation

[0033] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0034] Preparation example of magnetic adsorbent

[0035] Preparation Example 1

[0036] A magnetic adsorbent, the preparation method of which includes the following steps:

[0037] S1: FeCl2 and FeCl3 in a molar ratio of 1:2 were added to deionized water, and ammonia was added dropwise to adjust the pH to 10±0.5. The co-precipitation reaction was carried out at 75℃ under N2 protection for 1 hour. After magnetic separation, the mixture was washed three times each with deionized water and ethanol and then vacuum dried at 60℃ to obtain Fe3O4 particles with an average particle size of 10-20nm.

[0038] S2: 1g of Fe3O4 particles were dispersed in 200mL of 80% ethanol aqueous solution and ultrasonically dispersed for 30min. Then, 1.5g of hexadecyltrimethylammonium bromide was added and stirred evenly. 5mL of tetraethyl orthosilicate was added dropwise, followed by 2mL of ammonia water. The mixture was stirred at room temperature for 12h and then magnetically separated. After washing three times with ethanol, the product was dispersed in 100mL of ethanol and 0.5g of ammonium nitrate was added. The mixture was refluxed at 60℃ for 2h to obtain a core-shell structured pre-prepared magnetic adsorbent.

[0039] S3: Disperse 1g of pre-prepared magnetic adsorbent in 50mL of anhydrous toluene and sonicate for 30min to obtain a suspension. Dissolve 0.5g of 3-aminopropyltriethoxysilane and 0.3g of octadecyltrimethoxysilane in 10mL of 90% ethanol solution and adjust the pH to 4.5±0.2 with acetic acid to obtain a mixture. Add the mixture to the suspension and reflux at 110℃ for 12h under N2 protection. After magnetic separation, wash three times each with toluene and ethanol and then vacuum dry at 60℃ to obtain the final product.

[0040] Preparation Example 2

[0041] A magnetic adsorbent, the preparation method of which includes the following steps:

[0042] S1: FeCl2 and FeCl3 in a molar ratio of 1:1.8 were added to deionized water, and ammonia was added dropwise to adjust the pH to 10±0.5. The co-precipitation reaction was carried out at 70℃ under N2 protection for 1 hour. After magnetic separation, the mixture was washed three times each with deionized water and ethanol and then vacuum dried at 60℃ to obtain Fe3O4 particles with an average particle size of 10-20 nm.

[0043] S2: 1g of Fe3O4 particles were dispersed in 200mL of 80% ethanol aqueous solution and ultrasonically dispersed for 30min. Then, 1.5g of hexadecyltrimethylammonium bromide was added and stirred evenly. 5mL of tetraethyl orthosilicate was added dropwise, followed by 2mL of ammonia water. The mixture was stirred at room temperature for 12h and then magnetically separated. After washing three times with ethanol, the product was dispersed in 100mL of ethanol and 0.5g of ammonium nitrate was added. The mixture was refluxed at 55℃ for 2.5h to obtain a core-shell structured pre-prepared magnetic adsorbent.

[0044] S3: Disperse 1g of pre-prepared magnetic adsorbent in 50mL of anhydrous toluene and sonicate for 30min to obtain a suspension. Dissolve 0.5g of 3-aminopropyltriethoxysilane and 0.3g of octadecyltrimethoxysilane in 10mL of 90% ethanol solution and adjust the pH to 4.5±0.2 with acetic acid to obtain a mixture. Add the mixture to the suspension and reflux at 105℃ for 14h under N2 protection. After magnetic separation, wash three times each with toluene and ethanol and then vacuum dry at 60℃ to obtain the final product.

[0045] Preparation Example 3

[0046] A magnetic adsorbent, the preparation method of which includes the following steps:

[0047] S1: FeCl2 and FeCl3 in a molar ratio of 1:2.2 were added to deionized water, and ammonia was added dropwise to adjust the pH to 10±0.5. The co-precipitation reaction was carried out at 80℃ for 1 hour under N2 protection. After magnetic separation, the mixture was washed three times each with deionized water and ethanol and then vacuum dried at 60℃ to obtain Fe3O4 particles with an average particle size of 10-20 nm.

[0048] S2: 1g of Fe3O4 particles were dispersed in 200mL of 80% ethanol aqueous solution and ultrasonically dispersed for 30min. Then, 1.5g of hexadecyltrimethylammonium bromide was added and stirred evenly. 5mL of tetraethyl orthosilicate was added dropwise, followed by 2mL of ammonia water. The mixture was stirred at room temperature for 12h and then magnetically separated. After washing three times with ethanol, the product was dispersed in 100mL of ethanol and 0.5g of ammonium nitrate was added. The mixture was refluxed at 65℃ for 1.5h to obtain a core-shell structured pre-prepared magnetic adsorbent.

[0049] S3: Disperse 1g of pre-prepared magnetic adsorbent in 50mL of anhydrous toluene and sonicate for 30min to obtain a suspension. Dissolve 0.5g of 3-aminopropyltriethoxysilane and 0.3g of octadecyltrimethoxysilane in 10mL of 90% ethanol solution and adjust the pH to 4.5±0.2 with acetic acid to obtain a mixture. Add the mixture to the suspension and reflux at 115℃ for 10h under N2 protection. After magnetic separation, wash three times each with toluene and ethanol, and then vacuum dry at 60℃ to obtain the final product.

[0050] Preparation Example 4

[0051] The magnetic adsorbent differs from that in Preparation Example 1 only in that 3-aminopropyltriethoxysilane is not added in step S3.

[0052] Preparation Example 5

[0053] The magnetic adsorbent differs from that in Preparation Example 1 only in that octadecyltrimethoxysilane was not added in step S3.

[0054] Preparation Example 6

[0055] The magnetic adsorbent differs from that in Preparation Example 1 in that its preparation method includes the following steps:

[0056] S1: FeCl2 and FeCl3 in a molar ratio of 1:2 were added to deionized water, and ammonia was added dropwise to adjust the pH to 10±0.5. The co-precipitation reaction was carried out at 75℃ under N2 protection for 1 hour. After magnetic separation, the mixture was washed three times each with deionized water and ethanol and then vacuum dried at 60℃ to obtain Fe3O4 particles with an average particle size of 10-20nm.

[0057] S2: Disperse 1g of Fe3O4 particles in 200mL of 80% ethanol aqueous solution, sonicate for 30min, add 1.5g of hexadecyltrimethylammonium bromide, stir evenly, add 5mL of tetraethyl orthosilicate dropwise, then add 2mL of ammonia water, stir at room temperature for 12h, then perform magnetic separation, wash 3 times with ethanol, disperse the product in 100mL of ethanol, add 0.5g of ammonium nitrate, reflux at 60℃ for 2h, wash 3 times each with water and ethanol, and vacuum dry at 60℃ to obtain the product.

[0058] Example

[0059] Example 1

[0060] A method for refining peanut oil by low-temperature deacidification and purification includes the following steps:

[0061] S1: Peanuts are shelled and sieved to remove moldy kernels. After removing the red skin, peanut kernels are obtained. They are then crushed and sieved to obtain peanut raw materials with a particle size of (1.5±0.5) mm.

[0062] S2: Spray water and stir the peanut raw material until the moisture content is (17±1)%, then ultrasonically vibrate it and dry it until the moisture content is (7±1)% to obtain pretreated peanut material;

[0063] S3: The pre-treated peanut raw material is fed into a twin-screw cold slag press. The pressing chamber temperature is controlled at 40℃, the pressure at 25MPa, and the screw speed at 60r / min for low-temperature cold pressing. After centrifugation, the first crude oil is obtained.

[0064] S4: The first crude oil is sent into an ultrasonic degumming tank and ultrasonically assisted degumming is performed at 40°C. The degummed oil is then sent into a low-temperature crystallization tank and cooled to -5 to 0°C. The tank is kept warm for 2 hours to allow the wax to crystallize and undergo low-temperature crystallization dewaxing. After centrifugation to remove the wax, the second crude oil is obtained.

[0065] S5: Add 1% by weight of the magnetic adsorbent prepared in Preparation Example 1 to the second crude oil, stir and adsorb for 1.5 h under N2 protection at 50 °C, and then remove the magnetic adsorbent by magnetic separation by increasing the magnetic field to obtain the pretreated crude oil.

[0066] S6: The pretreated crude oil is subjected to low-temperature distillation and deacidification at 110°C in an inert gas atmosphere, followed by vacuum deodorization at 140°C and 0.008MPa to obtain the final product.

[0067] Example 2

[0068] A method for refining peanut oil by low-temperature deacidification and purification includes the following steps:

[0069] S1: Peanuts are shelled and sieved to remove moldy kernels. After removing the red skin, peanut kernels are obtained. They are then crushed and sieved to obtain peanut raw materials with a particle size of (1.5±0.5) mm.

[0070] S2: Spray water and stir the peanut raw material until the moisture content is (17±1)%, then ultrasonically vibrate it and dry it until the moisture content is (7±1)% to obtain pretreated peanut material;

[0071] S3: The pre-treated peanut raw material is fed into a twin-screw cold slag press. The pressing chamber temperature is controlled at 35℃, the pressure at 30MPa, and the screw speed at 50r / min for low-temperature cold pressing. After centrifugal separation, the first crude oil is obtained.

[0072] S4: The first crude oil is sent into an ultrasonic degumming tank and ultrasonically assisted degumming is performed at 45°C. The degummed oil is then sent into a low-temperature crystallization tank and cooled to -5 to 0°C. The tank is kept warm for 1 hour to allow the wax to crystallize and undergo low-temperature crystallization dewaxing. After centrifugation to remove the wax, the second crude oil is obtained.

[0073] S5: Add 2% by mass of the second crude oil of the magnetic adsorbent prepared in Preparation Example 2 to the second crude oil, stir and adsorb for 1 hour under N2 protection at 60°C, and then remove the magnetic adsorbent by magnetic separation by increasing the magnetic field to obtain the pretreated crude oil.

[0074] S6: The pretreated crude oil is subjected to low-temperature distillation and deacidification at 130℃ in an inert gas atmosphere, followed by vacuum deodorization at 150℃ and 0.005MPa to obtain the final product.

[0075] Example 3

[0076] A method for refining peanut oil by low-temperature deacidification and purification includes the following steps:

[0077] S1: Peanuts are shelled and sieved to remove moldy kernels. After removing the red skin, peanut kernels are obtained. They are then crushed and sieved to obtain peanut raw materials with a particle size of (1.5±0.5) mm.

[0078] S2: Spray water and stir the peanut raw material until the moisture content is (17±1)%, then ultrasonically vibrate it and dry it until the moisture content is (7±1)% to obtain pretreated peanut material;

[0079] S3: The pre-treated peanut raw material is fed into a twin-screw cold slag press. The pressing chamber temperature is controlled at 40℃, the pressure at 30MPa, and the screw speed at 50r / min for low-temperature cold pressing. After centrifugal separation, the first crude oil is obtained.

[0080] S4: The first crude oil is sent into an ultrasonic degumming tank and ultrasonically assisted degumming is performed at 45°C. The degummed oil is then sent into a low-temperature crystallization tank and cooled to -5 to 0°C. The tank is kept warm for 1.5 hours to allow the wax to crystallize and undergo low-temperature crystallization dewaxing. After centrifugation to remove the wax, the second crude oil is obtained.

[0081] S5: Add 3% by weight of the magnetic adsorbent prepared in Preparation Example 3 to the second crude oil, stir and adsorb for 1.5 h under N2 protection at 50 °C, and then remove the magnetic adsorbent by magnetic separation by increasing the magnetic field to obtain the pretreated crude oil.

[0082] S6: The pretreated crude oil is subjected to low-temperature distillation and deacidification at 120°C in an inert gas atmosphere, followed by vacuum deodorization at 140°C and 0.007MPa to obtain the final product.

[0083] Example 4

[0084] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the magnetic adsorbent in step S5 is prepared by Example 4.

[0085] Example 5

[0086] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the magnetic adsorbent in step S5 is prepared by Example 5.

[0087] Example 6

[0088] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the magnetic adsorbent in step S5 is prepared by Example 6.

[0089] Example 7

[0090] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the peanut raw material is not subjected to the pretreatment process in step S2.

[0091] Example 8

[0092] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the amount of magnetic adsorbent added in step S5 is 0.5% of the mass of the second crude oil.

[0093] Example 9

[0094] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 3 only in that the amount of magnetic adsorbent added in step S5 is 3.5% of the mass of the second crude oil.

[0095] Comparative Example

[0096] Comparative Example 1

[0097] A method for refining peanut oil by low-temperature deacidification and purification differs from Example 1 only in that the second crude oil is not subjected to the magnetic adsorbent pretreatment in step S5.

[0098] Performance testing

[0099] The peanut oils prepared by the low-temperature deacidification and purification method of Examples 1-9 and Comparative Example 1 were subjected to the following related performance tests. Each group of tests was conducted 3 times, and the average value of the 3 test results was taken as the final result and recorded in Table 1.

[0100] 1. Refer to the relevant provisions of GB 5009 "National Food Safety Standard" to test the acid value and peroxide value of peanut oil;

[0101] 2. Characteristic aroma: The content of pyrazine characteristic aroma and flavor compounds in peanut oil was determined by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry.

[0102] 3. Sensory evaluation of aroma intensity: Take 15-20g of the aroma-enhancing peanut oil into 50mL sensory evaluation bottles, and select 12 sensory evaluators with peanut oil evaluation experience to score the aroma intensity. The evaluation of the aroma intensity of the aroma-enhancing peanut oil includes aspects such as raw taste, steamed taste, sweet taste, roasted taste, burnt taste, bitter taste, sour taste and off-taste, to evaluate the flavor of the peanut oil.

[0103] Evaluation criteria:

[0104] 8 < fraction ≤ 10, the aroma is rich, complex, and layered;

[0105] 4 < fraction ≤ 8, strong aroma, with a certain degree of complexity;

[0106] 1 ≤ score ≤ 4, the aroma is weak and lacks complexity.

[0107] Table 1

[0108] Example 1 0.18 2.2 78.5 9.2 Example 2 0.15 2.0 79.2 9.4 Example 3 0.12 1.9 80.1 9.5 Example 4 0.42 2.5 58.3 6.8 Example 5 0.38 2.4 61.5 7.2 Example 6 0.55 2.8 52.2 5.5 Example 7 0.20 2.3 74.2 8.2 Example 8 0.22 2.5 62.0 6.5 Example 9 0.17 2.1 78.8 9.3 Comparative Example 1 0.60 3.2 40.2 4.5

[0109] According to the performance test results of Examples 1-3 and Comparative Example 1 in Table 1, it can be seen that the process of combining magnetic adsorbent pre-deacidification with low-temperature distillation deacidification in this application achieves a high deacidification rate under low-temperature conditions throughout the process, effectively preventing the volatilization of pyrazine flavor substances, ensuring the rich flavor of the finished peanut oil, and significantly improving the oxidative stability of the finished oil. In Comparative Example 1, no magnetic adsorbent was used for pretreatment, and low-temperature distillation deacidification was relied upon alone, which shows a significant decrease in deacidification effect. This also indicates that the magnetic adsorbent of this application can remove most of the free fatty acids before distillation, reduce the acid load of the distillation column, and allow the subsequent low-temperature distillation to treat only the remaining small amount of fatty acids. Under the premise of maintaining a distillation temperature of 110-130℃, effective deacidification can be achieved in a short time, significantly reducing the volatilization loss of pyrazine characteristic flavor substances.

[0110] Based on the performance test results of Examples 1 and 4-6, it can be seen that Example 4, lacking an aminosilane coupling agent, lacked active sites for binding with free fatty acids, resulting in a significant decrease in deacidification capacity; Example 5, without the addition of octadecyltrimethoxysilane, showed reduced dispersibility and hydrophobicity of the adsorbent in the oil phase; Example 6, having only prepared a core-shell structure without surface functionalization modification, lacked selective adsorption capacity. It can be seen that the introduction of amino sites provides effective chemisorption, while long-chain alkyl groups provide hydrophobicity and dispersibility. The two work synergistically to endow the adsorbent with high selectivity and high adsorption capacity; neither can be omitted.

[0111] According to the performance test results of Examples 1 and 7, Example 7 did not perform water spraying, ultrasonication and drying pretreatment of raw materials. Its pyrazine aroma retention rate (74.2%) and aroma intensity (7.5 points) were reduced. This shows that the raw material pretreatment can improve the cell wall breaking effect, reduce the dissolution of impurities and retain aroma precursor substances, thereby further improving the flavor and quality of the finished product.

[0112] According to the performance test results of Examples 1, 3 and 8-9, the addition amount of magnetic adsorbent can achieve the ideal effect in the range of 1-3%. Excessive addition will not further improve the product quality and meets the requirements of economic efficiency in industrial production.

[0113] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for refining peanut oil by low-temperature deacidification and purification, characterized in that, Includes the following steps: S1: Peanuts are removed from their red skins to obtain peanut kernels, which are then crushed to obtain raw peanuts. S2: The peanut raw material is subjected to low-temperature cold pressing and centrifugation to obtain the first crude oil; S3: The first crude oil is subjected to ultrasonic-assisted degumming, then cooled to -5 to 0℃ for low-temperature crystallization dewaxing, and centrifuged to remove the wax to obtain the second crude oil; S5: Add a magnetic adsorbent to the second crude oil, stir and adsorb it in an inert gas atmosphere, and then remove the magnetic adsorbent by magnetic separation by increasing the magnetic field to obtain the pretreated crude oil. S5: The pretreated crude oil is subjected to low-temperature distillation deacidification in an inert gas atmosphere at a distillation temperature of 110-130℃, and then vacuum deodorization is carried out at 140-150℃ and a vacuum degree of 0.005-0.008MPa to obtain the final product.

2. The method for refining peanut oil by low-temperature deacidification and purification according to claim 1, characterized in that, The preparation method of the magnetic adsorbent includes the following steps: FeCl2 and FeCl3 in a molar ratio of 1:(1.8-2.2) were added to water, the pH was adjusted to 10±0.5, and a co-precipitation reaction was carried out in an inert gas atmosphere at 70-80℃. After magnetic separation, washing and drying, Fe3O4 particles were obtained. Fe3O4 particles were dispersed in an ethanol-water solution, ultrasonically dispersed, and then hexadecyltrimethylammonium bromide was added. After stirring evenly, tetraethyl orthosilicate was added dropwise, followed by ammonia water. The mixture was stirred at room temperature and then magnetically separated. After washing, the product was dispersed in ethanol, ammonium nitrate was added, and the mixture was refluxed at 55-65℃ to obtain a core-shell structured pre-prepared magnetic adsorbent. The pre-made magnetic adsorbent was dispersed in toluene and ultrasonically dispersed. Then, an aqueous ethanol solution containing a silane coupling agent and a long-chain alkyl modifier was added. The mixture was refluxed at 105-115°C under an inert gas atmosphere. After magnetic separation, washing, and drying, the final product was obtained.

3. The method for refining peanut oil by low-temperature deacidification and purification according to claim 2, characterized in that, The silane coupling agent is selected from aminosilane coupling agents, and the long-chain alkyl reagent is selected from octadecyltrimethoxysilane.

4. The method for refining peanut oil by low-temperature deacidification and purification according to claim 3, characterized in that, In step S5, the magnetic adsorbent is adsorbed at a temperature of 50-60℃.

5. The method for refining peanut oil by low-temperature deacidification and purification according to claim 4, characterized in that, The amount of magnetic adsorbent added is 1-3% of the second crude oil.

6. The method for refining peanut oil by low-temperature deacidification and purification according to claim 1, characterized in that, The peanut raw material undergoes the following pretreatment before low-temperature cold pressing: The peanut raw material was sprayed with water and stirred until the moisture content was (17±1)%, then ultrasonically vibrated and dried until the moisture content was (7±1)%, thus obtaining pretreated peanut material.

7. The method for refining peanut oil by low-temperature deacidification and purification according to claim 1, characterized in that, The peanut raw material is subjected to low-temperature cold pressing at a temperature of 35-40℃ and a pressure of 25-30MPa.

8. A peanut oil, characterized in that, It is prepared by the peanut oil refining method of low-temperature deacidification and purification as described in any one of claims 1-7.