Method for extracting avocado oil and application thereof

Abstract

The invention provides a method for extracting avocado oil and application thereof. The method comprises the following steps: S1, raw material pretreatment: slicing, drying and crushing avocado pulp; s2, extracting by adopting subcritical n-butane: filling the dried pulp powder and n-butane into a reaction kettle, then adding a Fe3O4 (at) ZnO-PVCL nano material, adjusting the pH value of the system to 5.0-5.5, starting an extraction system, and stopping extraction when the online monitoring system shows that the grease concentration acceleration is less than 0.5 mg / mL / min; s3, separation and recovery of the Fe3O4-coated ZnO-PVCL nano material: applying a permanent magnet to recover the nano material, carrying out vacuum rotary evaporation to remove n-butane, and separating an oil phase and residues; s4, refining the avocado oil and utilizing residues: centrifuging and refining the oil phase to obtain the avocado oil; and converting the residue into a feed additive. According to the method, efficient and environment-friendly extraction of the avocado oil is realized through the magnetic property and catalytic performance of a nano material and the thermosensitivity of PVCL.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a method for extracting avocado oil and application thereof. Background Art

[0002] Avocado oil has attracted much attention in the fields of food, medicine and cosmetics due to its high nutritional value and antioxidant properties. At present, the industrial extraction of avocado oil mainly relies on traditional technology, but it still has significant limitations. Although the cold pressing method is simple, has no solvent residue, and has a high vitamin E retention rate, the extraction rate is low and the cost is relatively high; although the supercritical CO2 extraction method has no solvent residue and high selectivity, the cost is high. CO2 has poor solubility for polar components (such as polyphenols), and entrainers (such as ethanol) need to be added, which introduces the problem of secondary separation. The aqueous enzymatic method that has emerged in recent years destroys the cell wall through biological enzymatic hydrolysis, but the cost of enzyme preparations accounts for more than 30% of the production cost, and the process takes as long as 8 to 12 hours, making it difficult to promote industrialization. In recent years, subcritical fluids (such as water, butane, and propane) have attracted attention due to their low toxicity and easy recycling. While subcritical water extraction can change polarity by adjusting the temperature, its high temperature (>160°C) easily triggers the Maillard reaction, leading to a darker oil color and a loss of >20% of vitamin E. Subcritical butane / propane extraction can be performed at low temperatures (<100°C), but its use alone still presents problems such as low cell wall disruption efficiency and insufficient extraction of polar components. Overall, the common problem faced by existing technologies is that it is difficult to achieve both extraction efficiency and nutrient retention. High-extraction processes are often accompanied by high temperatures or chemical reagents that damage active ingredients.

[0003] In response to the above bottlenecks, the present invention proposes a method for extracting avocado oil based on the synergistic effect of subcritical n-butane extraction and nanomaterials. Compared with traditional methods, subcritical n-butane is non-toxic, easy to recycle, has lower carbon emissions than CO2, and does not require wastewater treatment. The vitamin E retention rate is >90%, and the peroxide value is ≤2.5meq / kg; combined with the directional catalysis and intelligent separation characteristics of functional nanomaterials, the extraction efficiency and selectivity are further enhanced. This technology also achieves the efficient utilization of pulp residues, which are converted into feed additives. The resource utilization rate reaches more than 95%, forming a "zero waste" closed-loop production system. Compared with the supercritical CO2 method, its energy consumption is reduced by 40%, and no complex pretreatment is required. It has the advantages of high efficiency, environmental protection and economy, and provides an effective solution for the high-value development of all components of avocado. Summary of the Invention

[0004] The present invention provides a method for extracting avocado oil and its application. The method of the present invention combines nanomaterials with dual functions of temperature response and catalysis with subcritical n-butane extraction, significantly improving the extraction efficiency and quality of avocado oil while having the advantages of high efficiency, environmental protection and economy.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a method for extracting avocado oil, comprising the following steps:

[0006] S1: Raw material pretreatment

[0007] Fresh, mold-free avocados are selected and washed 3-5 times with deionized water. The peel and seeds are removed and the pulp is separated. The pulp is then cut into 3-5 mm slices. The pulp slices are freeze-dried for 48-72 hours and crushed into 80-100 mesh particles to obtain dried pulp powder.

[0008] S2: Subcritical n-butane extraction

[0009] The dried fruit pulp powder and n-butane in S1 are charged into a reactor at a mass-to-volume ratio of 1:(20-40), and then a Fe3O4@ZnO-PVCL nanomaterial with a mass concentration of 0.3% is added. The pH of the system is adjusted to 5.0-5.5 with a 0.1 mol / L citric acid solution, and static mixing is performed for 5-10 minutes. The extraction system is started with an n-butane flow rate of 1.0-1.5 L / min, an extraction temperature of 40-50°C, and a pressure of 4-6 MPa. The vortex generator flow rate is controlled to be 1.3-1.7 m / s to stir the system. When the online monitoring system shows that the oil concentration growth rate is less than 0.5 mg / mL / min, the extraction is terminated.

[0010] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0011] After the extraction is terminated, the system temperature is lowered to below 30°C at a rate of 3-5°C / min, and a 0.5-0.8T permanent magnet is applied to the bottom of the reactor for 10-15 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial is washed 3-5 times with 70% ethanol and dried under vacuum at 60-70°C for recycling. The extract is collected in a collection bottle, and the n-butane is removed by vacuum rotary evaporation. The remaining mixed solution is centrifuged to separate the oil phase and the residue.

[0012] S4: Avocado oil refining and residue utilization

[0013] The oil phase in S3 is centrifuged and refined to obtain avocado oil; the residue is dried with hot air and converted into a feed additive.

[0014] Preferably, the freeze-drying temperature in S1 is -40 to -20°C.

[0015] Preferably, the amount of Fe3O4@ZnO-PVCL nanomaterial added to the S2 is 0.2-0.3 wt%.

[0016] Preferably, the filtration condition in S4 is 0.22 μm nylon membrane filtration.

[0017] Preferably, the centrifugation condition in S4 is centrifugation at a speed of 2000-4000 r / min for 10-15 min.

[0018] Preferably, the hot air drying temperature in S4 is 60-70° C., and the drying time is 4-6 hours.

[0019] Furthermore, the preparation steps of the Fe3O4@ZnO-PVCL nanomaterial are as follows:

[0020] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 10-11 with ammonia water, and the mixture was reacted at 80-90°C under nitrogen protection for 1-2 h. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0021] (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 10-12. After the reaction was completed, the particles were washed with deionized water and ethanol, separated by a magnet, and dried to obtain Fe3O4@ZnO.

[0022] (3) Fe3O4@ZnO was dispersed in anhydrous ethanol and ultrasonically treated for 30-40 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4@ZnO, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g: (50-150 mL): (1-3 mL). The mixture was refluxed and stirred at 70-90 °C under nitrogen protection for 6-7 h. After the reaction was completed, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40 °C and -0.1 MPa to obtain NH2-Fe3O4@ZnO.

[0023] (4) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4@ZnO was dispersed in the monomer solution, and nitrogen was bubbled for 30-40 min to deoxygenate. The mixture was stirred at 70°C for 12 h, and a nitrogen atmosphere was maintained during the reaction. After magnetic separation, the mixture was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed with deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@ZnO-PVCL nanomaterials, wherein the particle size of the nanomaterials was 30-70 nm.

[0024] Preferably, the mass volume ratio of Fe3O4 nanoparticles, deionized water and Zn(NO3)2 solution in step (2) is (0.05-0.2g): (50-100mL): (0.6-3g).

[0025] Preferably, in step (4), the mass volume ratio of N-vinyl caprolactam VCL, anhydrous ethanol and NH2-Fe3O4@ZnO is (1-5g): (50-100mL): 1g, and the added amount of initiator AIBN is 1-5% of N-vinyl caprolactam VCL.

[0026] On the other hand, the present invention also provides the use of the above method in extracting avocado oil.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] First, the ZnO shell of the functionalized nanomaterial used in the present invention releases trace amounts of Zn in a weakly acidic environment (pH 5.0-5.5). 2+ , can simulate the activity of cellulase, directionally hydrolyze cellulose and hemicellulose in the cell walls of pulp and core, and destroy the oil packaging structure;

[0029] Second, the poly (N-vinyl caprolactam) (PVCL) thermosensitive layer on the surface of the functionalized nanomaterial used in the present invention can undergo a hydrophobic phase transition, becoming hydrophilic below 35°C and oleophilic above 35°C. It specifically adsorbs non-polar oil molecules through hydrophobic interaction. During the extraction process, the system temperature is 40-50°C, and the PVCL thermosensitive layer is in a hydrophobic, oil-absorbing state, thereby improving the extraction rate of avocado oil. After the extraction is completed, the temperature is lowered to below 30°C, and the PVCL becomes hydrophilic and releases oil, achieving integrated extraction and separation, allowing the same material to perform different functions in the extraction stage (hydrophobic oil absorption) and the separation stage (hydrophilic oil release). Combined with the rapid recovery of the magnetic core, high-energy-consuming steps such as centrifugation and distillation in traditional processes are avoided, effectively reducing energy consumption.

[0030] Third, the subcritical n-butane extraction technology used in the present invention has relatively low temperature and pressure, which can effectively prevent high temperature from damaging heat-sensitive components in avocado, such as vitamin E, polyphenols and other active ingredients, thereby ensuring that the quality of the oil and its nutrients are not oxidized or degraded. The subcritical n-butane extraction technology has high extraction efficiency and can significantly improve the extraction rate of avocado oil.

[0031] Fourth, the nanomaterials used in this invention can be recycled more than 50 times, and the residue can be converted into feed additives after processing, achieving a comprehensive resource utilization rate of 95%. This technology uses n-butane as the only solvent, generating almost no "three wastes" pollution during operation. The solvent n-butane can be recycled, reducing the impact on the environment and achieving low-carbon green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning electron microscope image of the Fe3O4@ZnO-PVCL nanomaterial prepared in Example 3;

[0033] Figure 2 This is a physical picture of the avocado oil prepared in Example 8. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0035] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0036] It should be understood that the following limitations on the process parameters in the avocado extraction process of the present invention, the amount of Fe3O4@ZnO-PVCL nanomaterial added, the direct ratio range of each substance, and the ratio and concentration of each substance involved in the preparation process of Fe3O4@ZnO-PVCL nanomaterial are all preferred embodiments and should not be understood as limiting the scope of protection of the independent claims. The embodiments are only used to explain the present invention and are not used to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0037] Example 1 Preparation of Fe3O4@ZnO-PVCL nanomaterials

[0038] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 10 with ammonia water, and the mixture was reacted at 80°C under nitrogen protection for 1 h. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0039] (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 10. After the reaction was completed, the mixture was washed with deionized water and ethanol, separated by a magnet, and dried to obtain Fe3O4@ZnO, wherein the mass volume ratio of Fe3O4 nanoparticles, deionized water, and Zn(NO3)2 solution was 0.05 g:50 mL:0.6 g;

[0040] (3) Fe3O4@ZnO was dispersed in anhydrous ethanol and ultrasonically treated for 30 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4@ZnO, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g:50 mL:1 mL. The mixture was refluxed at 70 °C under nitrogen protection for 6 h. After the reaction, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40 °C and -0.1 MPa to obtain NH2-Fe3O4@ZnO.

[0041] (4) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4@ZnO was dispersed in the monomer solution, wherein the mass volume ratio of N-vinylcaprolactam (VCL), anhydrous ethanol and NH2-Fe3O4@ZnO was 1g:50mL:1g, and the amount of initiator AIBN added was 1% of N-vinylcaprolactam (VCL); nitrogen was bubbled for 30 minutes to deoxygenate, and the reaction was stirred at 70°C for 12 hours, during which the nitrogen atmosphere was maintained. After magnetic separation, the mixture was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed with deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@ZnO-PVCL nanomaterials.

[0042] Example 2 Preparation of Fe3O4@ZnO-PVCL nanomaterials

[0043] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 11 with ammonia water, and the mixture was reacted at 80°C under nitrogen protection for 1.5 h. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0044] (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 11. After the reaction was completed, the mixture was washed with deionized water and ethanol, separated by a magnet, and dried to obtain Fe3O4@ZnO, wherein the mass volume ratio of Fe3O4 nanoparticles, deionized water, and Zn(NO3)2 solution was 0.1 g:70 mL:1 g;

[0045] (3) Fe3O4@ZnO was dispersed in anhydrous ethanol and ultrasonically treated for 35 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4@ZnO, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g:80 mL:2 mL. The mixture was refluxed at 80 °C under nitrogen protection for 6.5 h. After the reaction was completed, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40 °C and -0.1 MPa to obtain NH2-Fe3O4@ZnO.

[0046] (4) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4@ZnO was dispersed in the monomer solution, wherein the mass volume ratio of N-vinylcaprolactam (VCL), anhydrous ethanol and NH2-Fe3O4@ZnO was 3g:80mL:1g, and the amount of initiator AIBN added was 3% of N-vinylcaprolactam (VCL); nitrogen was bubbled for 35 minutes to deoxygenate, and the reaction was stirred at 70°C for 12 hours, during which the nitrogen atmosphere was maintained. After magnetic separation, the product was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed with deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@ZnO-PVCL nanomaterials.

[0047] Example 3 Preparation of Fe3O4@ZnO-PVCL nanomaterials

[0048] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 11 with ammonia water, and the mixture was reacted at 90°C for 2 h under nitrogen protection. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0049] (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 12. After the reaction was completed, the mixture was washed with deionized water and ethanol, separated by a magnet, and dried to obtain Fe3O4@ZnO, wherein the mass volume ratio of Fe3O4 nanoparticles, deionized water, and Zn(NO3)2 solution was 0.2 g:100 mL:3 g;

[0050] (3) Fe3O4@ZnO was dispersed in anhydrous ethanol and ultrasonically treated for 40 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4@ZnO, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g:150 mL:3 mL. The mixture was refluxed at 90 °C for 7 h under nitrogen protection. After the reaction was completed, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40 °C and -0.1 MPa to obtain NH2-Fe3O4@ZnO.

[0051] (4) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4@ZnO was dispersed in the monomer solution. The mass volume ratio of N-vinylcaprolactam (VCL), anhydrous ethanol and NH2-Fe3O4@ZnO was 5g:100mL:1g, and the amount of initiator AIBN added was 5% of N-vinylcaprolactam (VCL). Nitrogen was bubbled for 40 minutes to deoxygenate, and the reaction was stirred at 70°C for 12 hours, during which the nitrogen atmosphere was maintained. After magnetic separation, the product was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed against deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@ZnO-PVCL nanomaterials.

[0052] Figure 1 This is a scanning electron microscope image of the Fe3O4@ZnO-PVCL nanomaterial prepared in this example.

[0053] Example 4 Preparation of Fe3O4@PVCL nanomaterials

[0054] The difference between this embodiment and embodiment 3 is that the catalyst layer ZnO is not included.

[0055] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 11 with ammonia water, and the mixture was reacted at 90°C for 2 h under nitrogen protection. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0056] (2) Fe3O4 nanoparticles were dispersed in anhydrous ethanol and ultrasonically treated for 40 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4 nanoparticles, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g:150 mL:3 mL. The mixture was refluxed at 90°C for 7 h under nitrogen protection. After the reaction, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40°C and -0.1 MPa to obtain NH2-Fe3O4.

[0057] (3) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4 was dispersed in the monomer solution. The mass volume ratio of N-vinylcaprolactam (VCL), anhydrous ethanol and NH2-Fe3O4 was 5g:100mL:1g, and the amount of initiator AIBN added was 5% of N-vinylcaprolactam (VCL). Nitrogen was bubbled for 40 minutes to deoxygenate, and the reaction was stirred at 70°C for 12 hours, during which the nitrogen atmosphere was maintained. After magnetic separation, the product was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed against deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@PVCL nanomaterials.

[0058] Example 5 Preparation of Fe3O4@ZnO Nanomaterials

[0059] The difference between this embodiment and embodiment 3 is that the temperature-sensitive layer PVCL is not included.

[0060] (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 11 with ammonia water, and the mixture was reacted at 90°C for 2 h under nitrogen protection. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles;

[0061] (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 12. After the reaction was completed, the mixture was washed with deionized water and ethanol, separated by a magnet and dried to obtain Fe3O4@ZnO nanomaterials, wherein the mass volume ratio of Fe3O4 nanoparticles, deionized water and Zn(NO3)2 solution was 0.2g:100mL:3g.

[0062] Example 6 Preparation of Fe3O4 Nanoparticles

[0063] The difference between this embodiment and embodiment 3 is that it does not contain the catalytic layer ZnO and the temperature sensitive layer PVCL

[0064] FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 11 with ammonia water, and the mixture was reacted at 90°C for 2 h under nitrogen protection. After the reaction was completed, the mixture was washed with deionized water and ethanol several times, separated by a magnet and dried to obtain Fe3O4 nanoparticles.

[0065] Example 7 A method for extracting avocado oil, comprising the following steps:

[0066] S1: Raw material pretreatment

[0067] Fresh, mold-free avocados were selected and washed three times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 3 mm slices. The pulp slices were freeze-dried at -40°C for 48 hours and crushed into 80 mesh particles to obtain the dried pulp powder.

[0068] S2: Subcritical n-butane extraction

[0069] The dried fruit pulp powder and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:20, and then the Fe3O4@ZnO-PVCL nanomaterial with a mass concentration of 0.3% prepared in Example 3 was added. The pH of the system was adjusted to 5.0 with 0.1 mol / L citric acid solution, and static mixing was performed for 5 minutes. The extraction system was started with an n-butane flow rate of 1.0 L / min, an extraction temperature of 40°C, and a pressure of 4 MPa. The vortex generator flow rate was controlled to be 1.3 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.2 wt%.

[0070] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0071] After the extraction is terminated, the system temperature is lowered to 25°C at a rate of 3-5°C / min. A 0.5T permanent magnet is applied to the bottom of the reactor for 10 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial is washed three times with 70% ethanol and dried under vacuum at 60°C for recycling. The extract is collected in a collection bottle and the n-butane is removed by vacuum rotary evaporation. The remaining mixed solution is centrifuged to separate the oil phase and the residue.

[0072] S4: Avocado oil refining and residue utilization

[0073] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 2000 r / min for 10 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 60° C. for 4 hours and then converted into a feed additive.

[0074] Example 8 A method for extracting avocado oil comprises the following steps:

[0075] S1: Raw material pretreatment

[0076] Fresh, mold-free avocados were selected and washed four times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -35°C for 50 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0077] S2: Subcritical n-butane extraction

[0078] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:30, and the Fe3O4@ZnO-PVCL nanomaterial prepared in Example 3 with a mass concentration of 0.3% was subsequently added. The pH of the system was adjusted to 5.3 with 0.1 mol / L citric acid solution, and static mixing was performed for 8 minutes. The extraction system was started with an n-butane flow rate of 1.2 / min, an extraction temperature of 35°C, and a pressure of 5 MPa. The vortex generator flow rate was controlled to be 1.5 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.25 wt%.

[0079] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0080] After the extraction was terminated, the system temperature was lowered to 20°C at a rate of 3-5°C / min. A 0.7T permanent magnet was applied to the bottom of the reactor for 12 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial was washed four times with 70% ethanol and dried under vacuum at 65°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixed solution was centrifuged to separate the oil phase and the residue.

[0081] S4: Avocado oil refining and residue utilization

[0082] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 3000 r / min for 12 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 65° C. for 5 hours and then converted into a feed additive.

[0083] Example 9 A method for extracting avocado oil, comprising the following steps:

[0084] S1: Raw material pretreatment

[0085] Fresh, mold-free avocados were selected and washed five times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -30°C for 60 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0086] S2: Subcritical n-butane extraction

[0087] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:35, and then 0.3% Fe3O4@ZnO-PVCL nanomaterial was added. The pH of the system was adjusted to 5.3 with 0.1 mol / L citric acid solution, and static mixing was performed for 8 minutes. The extraction system was started with an n-butane flow rate of 1.5 L / min, an extraction temperature of 30°C, and a pressure of 6 MPa. The vortex generator flow rate was controlled at 1.3 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was less than 0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.3 wt%.

[0088] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0089] After the extraction was terminated, the system temperature was lowered to 25°C at a rate of 3-5°C / min. A 0.7T permanent magnet was applied to the bottom of the reactor for 10 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial was washed four times with 70% ethanol and dried under vacuum at 60°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixed solution was centrifuged to separate the oil phase and the residue.

[0090] S4: Avocado oil refining and residue utilization

[0091] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 3500 r / min for 15 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 70° C. for 5 hours and then converted into a feed additive.

[0092] Example 10 A method for extracting avocado oil, comprising the following steps:

[0093] S1: Raw material pretreatment

[0094] Fresh, mold-free avocados were selected and washed five times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 5 mm slices. The pulp slices were freeze-dried at -20°C for 72 hours and crushed into 100 mesh particles to obtain dried pulp powder.

[0095] S2: Subcritical n-butane extraction

[0096] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:40, followed by the addition of 0.3% Fe3O4@ZnO-PVCL nanomaterials. The pH of the system was adjusted to 5.5 with 0.1 mol / L citric acid solution, and static mixing was performed for 10 minutes. The extraction system was started with an n-butane flow rate of 1.5 L / min, an extraction temperature of 40°C, and a pressure of 6 MPa. The vortex generator flow rate was controlled at 1.7 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.3 wt%.

[0097] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0098] After the extraction was terminated, the system temperature was lowered to 20°C at a rate of 3-5°C / min. A 0.8T permanent magnet was applied to the bottom of the reactor for 15 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial was washed five times with 70% ethanol and dried under vacuum at 70°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixed solution was centrifuged to separate the oil phase and the residue.

[0099] S4: Avocado oil refining and residue utilization

[0100] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 4000 r / min for 15 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 70° C. for 6 hours and then converted into a feed additive.

[0101] Comparative Example 1 A method for extracting avocado oil comprises the following steps:

[0102] S1: Raw material pretreatment

[0103] Fresh, mold-free avocados were selected and washed four times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -35°C for 50 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0104] S2: Subcritical n-butane extraction

[0105] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:30, and the Fe3O4@ZnO-PVCL nanomaterial prepared in Example 4 with a mass concentration of 0.3% was then added. The mixture was statically mixed for 8 minutes, and the extraction system was started with an n-butane flow rate of 1.2 / min, an extraction temperature of 35°C, and a pressure of 5 MPa. The vortex generator flow rate was controlled to be 1.5 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.25 wt%.

[0106] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0107] After terminating the extraction, a 0.7T permanent magnet was applied to the bottom of the reactor for 12 minutes to recover the Fe3O4@ZnO-PVCL nanomaterials. The recovered nanomaterials were washed four times with 70% ethanol and dried under vacuum at 65°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixture was centrifuged to separate the oil phase and the residue.

[0108] S4: Avocado oil refining and residue utilization

[0109] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 3000 r / min for 12 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 65° C. for 5 hours and then converted into a feed additive.

[0110] Comparative Example 2 A method for extracting avocado oil, comprising the following steps:

[0111] S1: Raw material pretreatment

[0112] Fresh, mold-free avocados were selected and washed four times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -35°C for 50 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0113] S2: Subcritical n-butane extraction

[0114] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:30, and the Fe3O4@ZnO-PVCL nanomaterial prepared in Example 5 with a mass concentration of 0.3% was then added. The mixture was statically mixed for 8 minutes, and the extraction system was started with an n-butane flow rate of 1.2 / min, an extraction temperature of 35°C, and a pressure of 5 MPa. The vortex generator flow rate was controlled to be 1.5 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.25 wt%.

[0115] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0116] After terminating the extraction, a 0.7T permanent magnet was applied to the bottom of the reactor for 12 minutes to recover the Fe3O4@ZnO-PVCL nanomaterials. The recovered nanomaterials were washed four times with 70% ethanol and dried under vacuum at 65°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixture was centrifuged to separate the oil phase and the residue.

[0117] S4: Avocado oil refining and residue utilization

[0118] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 3000 r / min for 12 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 65° C. for 5 hours and then converted into a feed additive.

[0119] Comparative Example 3 A method for extracting avocado oil, comprising the following steps:

[0120] S1: Raw material pretreatment

[0121] Fresh, mold-free avocados were selected and washed four times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -35°C for 50 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0122] S2: Subcritical n-butane extraction

[0123] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:30, and the Fe3O4@ZnO-PVCL nanomaterial prepared in Example 6 with a mass concentration of 0.3% was then added. The mixture was statically mixed for 8 minutes, and the extraction system was started with an n-butane flow rate of 1.2 / min, an extraction temperature of 35°C, and a pressure of 5 MPa. The vortex generator flow rate was controlled to be 1.5 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was <0.5 mg / mL / min. The amount of Fe3O4@ZnO-PVCL nanomaterial added was 0.25 wt%.

[0124] S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials

[0125] After terminating the extraction, a 0.7T permanent magnet was applied to the bottom of the reactor for 12 minutes to recover the Fe3O4@ZnO-PVCL nanomaterials. The recovered nanomaterials were washed four times with 70% ethanol and dried under vacuum at 65°C for recycling. The extract was collected in a collection bottle and the n-butane was removed by vacuum rotary evaporation. The remaining mixture was centrifuged to separate the oil phase and the residue.

[0126] S4: Avocado oil refining and residue utilization

[0127] The oil phase in S3 is filtered through a 0.22 μm nylon membrane, centrifuged at 3000 r / min for 12 minutes, and refined to obtain avocado oil; the residue is dried with hot air at 65° C. for 5 hours and then converted into a feed additive.

[0128] Comparative Example 4: A method for extracting avocado oil. Compared with Example 8, this comparative example does not use nanomaterials and includes the following steps:

[0129] S1: Raw material pretreatment

[0130] Fresh, mold-free avocados were selected and washed four times with deionized water. The peel and seeds were removed and the pulp was separated. The pulp was then cut into 4 mm slices. The pulp slices were freeze-dried at -35°C for 50 h and crushed into 90 mesh particles to obtain dried pulp powder.

[0131] S2: Subcritical n-butane extraction

[0132] The dried fruit pulp and n-butane in S1 were charged into a reactor at a mass-to-volume ratio of 1:30, and statically mixed for 8 minutes. The extraction system was started with an n-butane flow rate of 1.2 / min, an extraction temperature of 35°C, and a pressure of 5 MPa. The vortex generator flow rate was controlled at 1.5 m / s to stir the system. The extraction was terminated when the online monitoring system showed that the oil concentration growth rate was less than 0.5 mg / mL / min.

[0133] S3: Avocado oil refining and residue utilization

[0134] The extract was collected into a collection bottle, and n-butane was removed by vacuum rotary evaporation. The remaining mixed liquid was centrifuged to separate the oil phase and the residue. The oil phase was filtered through a 0.22 μm nylon membrane, centrifuged at 3000 r / min for 12 minutes, and refined to obtain avocado oil; the residue was hot-air dried at 65° C. for 5 hours and then converted into a feed additive.

[0135] The oil extraction rate, cellulose hydrolysis rate, peroxide value, vitamin E retention rate, polyphenol content of Examples 7 to 10 and Comparative Examples 1 to 4, and the residual amounts of Fe, Zn and VCL in avocado oil of the nanomaterials of Examples 7 to 10 were measured. The method used for oil extraction rate is GB 5009.6-2016 Determination of Fat in Food; the method used for cellulose hydrolysis rate is 3,5-dinitrosalicylic acid method; the method used for peroxide value is GB 5009.227-2023 National Food Safety Standard Determination of Peroxide Value in Food; the method used for vitamin E retention rate is GB 5009.82-2016 National Food Safety Standard Determination of Vitamins A, D, and E in Food; the method used for polyphenol content is Folin-phenol method, and the polyphenol content is calculated as gallic acid; the method used for the determination of the residual amount of Fe and Zn in avocado oil from nanomaterials is GB 5009.268-2016 National Food Safety Standard Determination of Multiple Elements in Food, and the method used for the residual amount of VCL in avocado oil is HPLC. The specific operation is as follows:

[0136] (1) Preparation of standard stock solution: Accurately weigh a certain amount of VCL standard, dissolve it in methanol and dilute to a certain volume to prepare a standard stock solution with a concentration of 1.0 mg / mL. Store in a brown bottle at -20°C.

[0137] (2) Preparation of standard working solution: Take appropriate amount of standard stock solution and dilute it with mobile phase to make standard working solution with concentration gradient of 0.01, 0.05, 0.1, 0.5, and 1.0 μg / mL.

[0138] (3) Chromatographic conditions: Specifications: 250 mm × 4.6 mm, 5 μm C 18 Chromatographic column; mobile phase is methanol: water = 70:30 (v / v); flow rate is 1.0 mL / min; detection wavelength is 210-220 nm; column temperature is 30°C; injection volume is 10 μL.

[0139] (4) Sample pretreatment: Accurately weigh 5.0 g of the avocado oil sample prepared in Examples 7 to 10 into a 50 mL centrifuge tube, add 10 mL of n-hexane, and vortex mix for 1 min to fully dissolve the avocado oil; then add 10 mL of dichloromethane and ultrasonically extract for 15 min, shaking once every 5 min; after the extraction is completed, centrifuge at 3000 r / min for 10 min to separate the organic phase and the aqueous phase; transfer the lower organic phase to a rotary evaporator and evaporate it under reduced pressure at 40°C to near dryness; dilute to 1.0 mL with methanol, filter through a 0.45 μm microporous filter membrane, and take the filtrate as the sample solution to be tested.

[0140] (5) Plotting the standard curve: Sequentially inject different concentrations of standard working solution into the HPLC instrument and record the chromatographic peak area of ​​VCL at each concentration. Plot the standard curve with VCL concentration as the horizontal axis and chromatographic peak area as the vertical axis.

[0141] (6) Sample determination: Inject the treated sample solution into a high performance liquid chromatograph and record the chromatographic peak area of ​​VCL in the sample. Calculate the VCL content in the sample based on the standard curve. The calculation formula is as follows:

[0142]

[0143] Where: X is the residual amount of VCL in the sample (mg / kg); C is the concentration of VCL in the sample solution obtained from the standard curve (μg / mL); V is the constant volume of the sample solution (mL); and m is the mass of the sample (g).

[0144] The oil extraction rate, cellulose hydrolysis rate, peroxide value, vitamin E retention rate, and polyphenol content of Examples 7 to 10 and Comparative Examples 1 to 4 are shown in Table 1. The residual amounts of Fe, Zn, and VCL in avocado oil of the nanomaterials of Examples 7 to 10 are shown in Table 2.

[0145] Table 1. Oil extraction rate, cellulose hydrolysis rate, peroxide value, vitamin E retention rate, and polyphenol content

[0146]

[0147] The data in Table 1 show that Examples 7-10 were superior to Comparative Examples 1-4 in terms of oil extraction rate, cellulose hydrolysis rate, vitamin E retention rate, and polyphenol content. Among them, Example 8 performed best in all indicators, with the highest oil extraction rate, cellulose hydrolysis rate, vitamin E retention rate, and polyphenol content, and the lowest peroxide value, indicating that the avocado oil extracted from it was of the highest quality.

[0148] Table 2. Residual amounts of Fe, Zn and VCL in avocado oil from nanomaterials of Examples 7 to 10

[0149] Fe residue (mg / kg) Zn residue (mg / kg) VCL residue (mg / kg) Example 7 3.5 4.5 5.7 Example 8 2.8 4.0 4.9 Example 9 3.0 4.2 5.5 Example 10 4.1 4.1 5.2

[0150] As can be seen from Table 2, the residual amounts of Fe, Zn, and VCL in the nanomaterials of Examples 7 to 10 in avocado oil are all less than 10 mg / kg, which are far below the safety limit. This indicates that the nanomaterials of the present invention are highly safe and will not harm the quality of avocado oil or human health.

[0151] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for extracting avocado oil, characterized in that: The following steps are involved: S1: Raw material pretreatment Fresh, mold-free avocados are selected and washed 3-5 times with deionized water. The peel and seeds are removed and the pulp is separated. The pulp is then cut into 3-5 mm slices. The pulp slices are freeze-dried for 48-72 hours and crushed into 80-100 mesh particles to obtain dried pulp powder. S2: Subcritical n-butane extraction The dried fruit pulp powder and n-butane in S1 are charged into a reactor at a mass-to-volume ratio of 1:(20-40), followed by the addition of 0.3% Fe3O4@ZnO-PVCL nanomaterial, and the pH of the system is adjusted to 5.0-5.5 with 0.1 mol / L citric acid solution. The system is statically mixed for 5-10 minutes, and the extraction system is started with an n-butane flow rate of 1.0-1.5 L / min, an extraction temperature of 40-50°C, and a pressure of 4-6 MPa. The vortex generator flow rate is controlled at 1.3-1.7 m / s to stir the system. The extraction is terminated when the online monitoring system shows that the oil concentration growth rate is less than 0.5 mg / mL / min. S3: Separation and recovery of Fe3O4@ZnO-PVCL nanomaterials After the extraction is terminated, the system temperature is lowered to below 30°C at a rate of 3-5°C / min, and a 0.5-0.8T permanent magnet is applied to the bottom of the reactor for 10-15 minutes to recover the Fe3O4@ZnO-PVCL nanomaterial. The recovered nanomaterial is washed 3-5 times with 70% ethanol and dried under vacuum at 60-70°C for recycling. The extract is collected in a collection bottle, and the n-butane is removed by vacuum rotary evaporation. The remaining mixed solution is centrifuged to separate the oil phase and the residue. S4: Avocado oil refining and residue utilization The oil phase in S3 is centrifuged and refined to obtain avocado oil; the residue is dried with hot air and converted into a feed additive.

2. The method according to claim 1, wherein The freeze-drying temperature in S1 is -40 to -20°C.

3. The method according to claim 1, wherein The amount of Fe3O4@ZnO-PVCL nanomaterial added to the S2 is 0.2-0.3 wt%.

4. The method according to claim 1, wherein The filtration condition in S4 is 0.22 μm nylon membrane filtration.

5. The method according to claim 1, wherein The centrifugal condition in S4 is centrifugation at a speed of 2000-4000 r / min for 10-15 minutes.

6. The method according to claim 1, wherein The hot air drying temperature in S4 is 60-70° C., and the drying time is 4-6 hours.

7. The method according to claim 1, wherein The preparation steps of the Fe3O4@ZnO-PVCL nanomaterial are as follows: (1) FeCl3·6H2O with a concentration of 0.1 mol / L and FeCl2·4H2O with a concentration of 0.05 mol / L were mixed in a molar ratio of 2:1, the pH was adjusted to 10-11 with ammonia water, and the mixture was reacted at 80-90°C under nitrogen protection for 1-2 h. After the reaction, the mixture was washed with deionized water and ethanol several times, separated by a magnet, and dried to obtain Fe3O4 nanoparticles; (2) Fe3O4 nanoparticles were dispersed in deionized water, Zn(NO3)2 solution was slowly added, and NaOH solution was added dropwise under stirring to adjust the pH to 10-12. After the reaction was completed, the particles were washed with deionized water and ethanol, separated by a magnet, and dried to obtain Fe3O4@ZnO. (3) Fe3O4@ZnO was dispersed in anhydrous ethanol and ultrasonically treated for 30-40 min. 3-aminopropyltriethoxysilane (APTES) was added, wherein the mass volume ratio of Fe3O4@ZnO, anhydrous ethanol and 3-aminopropyltriethoxysilane (APTES) was 1 g: (50-150 mL): (1-3 mL). The mixture was refluxed and stirred at 70-90 °C under nitrogen protection for 6-7 h. After the reaction was completed, the product was separated with a magnet, washed with ethanol and water three times in sequence, and dried in a vacuum at 40 °C and -0.1 MPa to obtain NH2-Fe3O4@ZnO. (4) N-vinylcaprolactam (VCL) was dissolved in anhydrous ethanol, and initiator AIBN was added to obtain a PVCL monomer solution. NH2-Fe3O4@ZnO was dispersed in the monomer solution, and nitrogen was bubbled for 30-40 min to deoxygenate. The mixture was stirred at 70°C for 12 h, and a nitrogen atmosphere was maintained during the reaction. After magnetic separation, the mixture was washed with ethanol three times to remove unreacted monomers. The product was dispersed in water, dialyzed with deionized water for 3 days to remove oligomers, and freeze-dried to obtain Fe3O4@ZnO-PVCL nanomaterials, wherein the particle size of the nanomaterials was 30-70 nm.

8. The method according to claim 7, wherein The mass volume ratio of Fe3O4 nanoparticles, deionized water and Zn(NO3)2 solution in step (2) is (0.05-0.2g): (50-100mL): (0.6-3g).

9. The method according to claim 7, wherein In the step (4), the mass volume ratio of N-vinyl caprolactam VCL, anhydrous ethanol and NH2-Fe3O4@ZnO is (1-5g): (50-100mL): 1g, and the added amount of initiator AIBN is 1-5% of N-vinyl caprolactam VCL.

10. Use of the method according to any one of claims 1 to 6 in extracting avocado oil.

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