A method for subcritical low-temperature extraction of leek seed oil

Abstract

This invention relates to the field of oil extraction technology, specifically a method for subcritical low-temperature extraction of leek seed oil, comprising the following steps: (1) raw material pretreatment; (2) compound enzymatic hydrolysis cell wall breaking treatment; (3) subcritical low-temperature extraction; (4) integrated gradient low-temperature separation and solvent recovery purification. This invention, through the synergistic combination of raw material low-temperature pretreatment, compound enzymatic hydrolysis directional cell wall breaking, subcritical dynamic countercurrent extraction, and gradient low-temperature separation purification, optimizes the entire process from raw material structure modification, enhanced extraction mass transfer, to efficient product separation, systematically improving the efficiency and quality of leek seed oil preparation. In the raw material stage, hot air low-temperature drying and liquid nitrogen-assisted pulverization are used, which can reduce the moisture content of the raw material and refine the particle size without damaging the intracellular contents, reducing oil oxidation in subsequent processing, while simultaneously improving the enzymatic hydrolysis of the cell wall, laying the foundation for efficient extraction.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, specifically a method for subcritical low-temperature extraction of leek seed oil. Background Technology

[0002] Leek seeds are rich in unsaturated fatty acids, sterols, and various active substances, and the resulting leek seed oil has high application value in the food and health product fields. Currently, the extraction methods for leek seed oil are mainly traditional hot pressing and organic solvent extraction. The high temperatures during the production process can easily cause the decomposition and oxidation of active ingredients in the oil, affecting product quality.

[0003] While existing low-temperature extraction technologies can reduce heat damage to some extent, they generally suffer from insufficient cell wall disruption and high resistance to oil mass transfer, resulting in low extraction rates. Furthermore, the extraction solvents used are of single polarity, making them poorly compatible with the different polar components in leek seed oil, hindering efficient and selective extraction. Some processes employ enzymatic hydrolysis to assist cell wall disruption, but these suffer from issues such as inappropriate enzyme ratios, insufficient enzyme activity stability, and limited cell wall disruption efficiency. Incomplete solvent recovery after extraction also leads to problems such as excessive solvent residue, lengthy separation and purification processes, and high energy consumption, making it difficult to meet the demands of stable industrial production and high-quality oil preparation.

[0004] Therefore, developing a subcritical low-temperature extraction method for leek seed oil that achieves thorough cell wall disruption, high extraction efficiency, and integrated separation and purification is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a method for subcritical low-temperature extraction of leek seed oil.

[0006] The specific technical solution is as follows: A method for subcritical low-temperature extraction of leek seed oil, comprising the following steps:

[0007] (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually, dry with hot air circulation, dry, crush and sieve to obtain leek seed powder;

[0008] (2) Compound enzymatic hydrolysis and cell wall breaking treatment: Add buffer solution to the leek seed powder, then add compound buffer regulator, compound biological enzyme and enzyme activity protectant, stir and enzymatic hydrolysis, after enzymatic hydrolysis, inactivate enzyme, filter and dry to obtain enzymatic hydrolyzed cell wall breaking leek seed powder;

[0009] (3) Subcritical low temperature extraction: After the enzymatically hydrolyzed and cell wall broken leek seed powder and nano silica adsorbent are mixed evenly, they are loaded into the extraction vessel, the extraction vessel is evacuated, and a polarity adjustable composite subcritical solvent is injected to carry out dynamic countercurrent extraction to obtain the extraction mixture.

[0010] (4) Gradient low temperature separation and solvent recovery and purification integration: The extraction mixture is sent into the separator, the solvent is first condensed and recovered, the recovered solvent is purified by molecular sieve adsorption column, and the remaining material is vacuum desolventized and filtered to obtain leek seed oil.

[0011] The composite bioenzyme is a mixture of cellulase, hemicellulase, and pectinase in a mass ratio of 2:1:1; the enzyme activity protectant is a mixture of proline and trehalose in a mass ratio of 1:2; the polarity-tunable composite subcritical solvent is a mixture of n-butane, isobutane, and anhydrous ethanol in a volume ratio of 77-78:18:5; the nano-silica adsorbent is nano-silica modified with silane coupling agent KH-550; and the composite buffer regulator is a mixture of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:2.

[0012] As a further technical solution, in step (1), the leek seeds are manually cleaned until the purity is ≥99%, the hot air circulation drying temperature is 42-48℃ and the wind speed is controlled at 1.2-1.4m / s, and the moisture content is 6%-7%. The crushing is assisted by liquid nitrogen at a low temperature of 0-5℃, and the amount of liquid nitrogen added is 8%-10% of the mass of the leek seeds. After crushing, the seeds are passed through a 45-55 mesh sieve.

[0013] As a further technical solution, in step (2), the buffer solution is an acetate-sodium acetate buffer solution with a pH of 4.8-5.2 and a concentration of 0.1 mol / L, and the material-liquid ratio is 1:2.0-2.2; the amount of compound buffer regulator added is 0.8%-1.0% of the mass of leek seed powder, the amount of compound biological enzyme added is 1.0%-1.2% of the mass of leek seed powder, and the amount of enzyme activity protectant added is 12%-14% of the mass of compound biological enzyme.

[0014] As a further technical solution, in step (2), the enzymatic hydrolysis temperature is 48-52℃, the stirring is intermittent, the stirring speed is 80-120r / min, each stirring is 10min, with an interval of 5min, and the enzymatic hydrolysis time is 1.8-2.2h; the enzyme inactivation is carried out by water bath at 86-88℃ for 16-18min; the filtration is carried out by vacuum filtration at a pressure of 0.3-0.4MPa, using double-layer filter cloth with a pore size of 0.1-0.2μm; the filter residue is dried at 40-45℃ until the moisture content is 5%-6%.

[0015] As a further technical solution, in step (3), the mass ratio of enzymatically hydrolyzed broken leek seed powder to nano silica adsorbent is 100:2-3; an ultrasonic auxiliary device is set in the extraction vessel, with an ultrasonic frequency of 20-30kHz and a power of 500-800W, and the device is turned on for 3 minutes every 15 minutes.

[0016] As a further technical solution, in step (3), the extraction vessel is evacuated to -0.09~-0.1MPa, the amount of polarity adjustable composite subcritical solvent is 3-3.5 times the mass of the enzymatically hydrolyzed and cell-wall broken leek seed powder; the dynamic countercurrent extraction temperature is 34-36℃, the pressure is 0.9-1.1MPa, the flow rate is 1.8-2.4L / min·kg leek seed powder, and the extraction time is 50-60min.

[0017] As a further technical solution, in step (3), a pulse pressurization is performed every 12-15 minutes during the extraction process, with a pressurization increase of 0.12-0.18 MPa and each lasting 1.0-1.8 minutes; at the same time, the stirring is carried out at a speed of 90-120 r / min, and the stirring direction is switched every 20 minutes. When switching, the speed is first reduced to 50 r / min, maintained for 30 seconds, and then restored to the original speed.

[0018] As a further technical solution, in step (4), the condensation and recovery solvent temperature is 36-38℃, the pressure is 0.45-0.55MPa, the condensation temperature is 5-10℃, the recovery time is 35-38min, and the volume of the recovered solvent is more than 95% of the volume of the injected solvent; the molecular sieve adsorption column is model 3A, the temperature is 25-30℃, the solvent flow rate is 10-15L / min, and the molecular sieve is loaded with 0.5%-1.0% of heavy metal chelating agent.

[0019] As a further technical solution, the heavy metal chelating agent is a mixture of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:1.

[0020] As a further technical solution, in step (4), the vacuum desolvation temperature is 46-48℃, the pressure is -0.09MPa, the desolvation time is 28-32min, and the nitrogen is used for intermittent purging at 0.5-1.0L / min, with each purging lasting 5min and an interval of 3min; the filtration uses an alumina ceramic filter membrane with a pore size of 0.25-0.4μm and a pressure of 0.35-0.45MPa, and the filter membrane is rinsed with deionized water after filtration.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention systematically improves the efficiency and quality of leek seed oil preparation by synergistically combining low-temperature pretreatment of raw materials, directional cell wall disruption via compound enzymatic hydrolysis, subcritical dynamic countercurrent extraction, and gradient low-temperature separation and purification. This optimization covers the entire process from raw material structure modification and enhanced extraction mass transfer to efficient product separation. In the raw material stage, hot air low-temperature drying and liquid nitrogen-assisted pulverization reduce moisture content and refine particle size without damaging intracellular contents, minimizing oil oxidation during subsequent processing and enhancing cell wall enzymatic hydrolysis, thus laying the foundation for efficient extraction. The synergistic effect of a compound buffer regulator and enzyme activity protectant stabilizes the pH environment of the enzymatic hydrolysis system, while the latter maintains the spatial structure and catalytic activity of the compound enzymes. This allows cellulase, hemicellulase, and pectinase to degrade the cell wall skeleton in a specific ratio, effectively breaking down the oil release barrier and significantly improving the extractability of intracellular oils.

[0023] In the subcritical extraction process, KH-550 modified nano-silica adsorbent adsorbs fine impurities and some polar interfering substances in the raw material, reducing the viscosity of the extract and enhancing mass transfer. A polarity-adjustable solvent, a mixture of n-butane, isobutane, and anhydrous ethanol in a specific ratio, has a high compatibility with different polar components in leek seed oil, achieving selective dissolution and efficient extraction at low temperatures. Combined with ultrasonic assistance, pulsed pressurization, and directional stirring, the solid-liquid interface is continuously renewed, the diffusion layer thickness is reduced, and the extraction rate and completeness are significantly improved, avoiding oil deterioration caused by prolonged high-temperature extraction. The integrated gradient low-temperature separation and solvent recovery and purification process achieves efficient solvent condensation and recovery at specific temperatures. Combined with deep purification using 3A molecular sieves and loaded heavy metal chelating agents, solvent recovery rates are maintained at over 95% while reducing solvent residue. Vacuum desolventizing combined with intermittent nitrogen purging completely removes residual solvent at low temperatures, preventing an increase in oil peroxide value. The alumina ceramic filter membrane further enhances the clarity and purity of the oil.

[0024] This invention features mutually matched and synergistically enhanced steps and parameters. It addresses issues such as insufficient cell wall disruption, low extraction efficiency, high solvent residue, and significant loss of active ingredients through step-by-step control. Furthermore, it shortens the production cycle and reduces energy consumption through overall process coupling, achieving a balance between high extraction rate, low solvent residue, high activity retention, and large-scale production. The resulting leek seed oil exhibits high extraction rate, low peroxide value, and stable quality. Simultaneously, the solvent is recyclable, resulting in low production costs and good environmental performance. This effectively overcomes the shortcomings of existing technologies in terms of efficiency, quality, and economy, making it suitable for industrial-scale application. Attached Figure Description

[0025] Figure 1 This is a flowchart of a subcritical low-temperature extraction method for leek seed oil. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0027] This invention provides a method for subcritical low-temperature extraction of leek seed oil, comprising the following steps:

[0028] (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually, dry with hot air circulation, dry, crush and sieve to obtain leek seed powder;

[0029] (2) Compound enzymatic hydrolysis cell wall breaking treatment: Add buffer solution to leek seed powder, then add compound buffer regulator, compound biological enzyme and enzyme activity protectant, stir and enzymatic hydrolysis, after enzymatic hydrolysis, inactivate enzyme, filter and dry to obtain enzymatic hydrolyzed cell wall broken leek seed powder.

[0030] (3) Subcritical low temperature extraction: After the enzymatically hydrolyzed and cell wall broken leek seed powder and nano silica adsorbent are mixed evenly, they are loaded into the extraction vessel, the extraction vessel is evacuated, and a polarity adjustable composite subcritical solvent is injected to carry out dynamic countercurrent extraction to obtain the extraction mixture.

[0031] (4) Gradient low temperature separation and solvent recovery and purification integration: The extraction mixture is sent into the separator, the solvent is first condensed and recovered, the recovered solvent is purified by molecular sieve adsorption column, and the remaining material is vacuum desolventized and filtered to obtain leek seed oil.

[0032] In this invention, the leek seeds are selected from those free of mold, and impurities are removed manually until the leek seed purity is ≥99%. Hot air circulation drying is performed at a temperature of 42-48℃, with an air velocity controlled at 1.2-1.4 m / s, until the moisture content reaches 6%-7%. Crushing is assisted by low-temperature liquid nitrogen at 0-5℃, with the amount of liquid nitrogen added being 8%-10% of the leek seed mass. The crushed seeds are then passed through a 45-55 mesh sieve.

[0033] In this invention, the buffer solution is an acetate-sodium acetate buffer solution with a pH of 4.8-5.2 and a concentration of 0.1 mol / L, and the material-to-liquid ratio is 1:2.0-2.2. The composite buffer regulator is a mixture of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:2, and the amount added is 0.8%-1.0% of the mass of leek seed powder. The composite bioenzyme is a mixture of cellulase, hemicellulase, and pectinase in a mass ratio of 2:1:1, and the amount added is 1.0%-1.2% of the mass of leek seed powder. The enzyme activity protectant is a mixture of proline and trehalose in a mass ratio of 1:2, and the amount added is 12%-14% of the mass of the composite bioenzyme.

[0034] In this invention, the enzymatic hydrolysis temperature is 48-52℃, stirring is intermittent at a speed of 80-120 r / min, with each stirring session lasting 10 min and an interval of 5 min, for a total hydrolysis time of 1.8-2.2 h. Enzyme inactivation is performed using a water bath at 86-88℃ for 16-18 min. Filtration is performed using vacuum filtration at a pressure of 0.3-0.4 MPa, employing a double-layer filter cloth with a pore size of 0.1-0.2 μm. The filter residue is dried at 40-45℃ until the moisture content reaches 5%-6%.

[0035] In this invention, the nano-silica adsorbent is nano-silica modified with silane coupling agent KH-550, and the mass ratio of enzymatically hydrolyzed and cell-wall-broken leek seed powder to nano-silica adsorbent is 100:2-3. An ultrasonic auxiliary device is installed in the extraction vessel, with an ultrasonic frequency of 20-30kHz and a power of 500-800W, which is turned on for 3 minutes every 15 minutes.

[0036] In this invention, the extraction vessel is evacuated to -0.09 to -0.1 MPa. The polarity-adjustable composite subcritical solvent is a mixture of n-butane, isobutane, and anhydrous ethanol in a volume ratio of 77-78:18:5, and the amount of solvent used is 3-3.5 times the mass of the enzymatically hydrolyzed and cell-wall-broken leek seed powder. The dynamic countercurrent extraction temperature is 34-36℃, the pressure is 0.9-1.1 MPa, the flow rate is 1.8-2.4 L / min·kg leek seed powder, and the extraction time is 50-60 min.

[0037] In this invention, during the extraction process, a pulsed pressurization is performed every 12-15 minutes, with a pressurization increase of 0.12-0.18 MPa, each lasting 1.0-1.8 minutes. Simultaneously, the mixture is stirred at a speed of 90-120 r / min, with the stirring direction changed every 20 minutes. When changing the direction, the speed is first reduced to 50 r / min, maintained for 30 seconds, and then restored to the original speed.

[0038] In this invention, the solvent recovery temperature is 36-38℃, the pressure is 0.45-0.55MPa, the condensation temperature is 5-10℃, the recovery time is 35-38min, and the recovered solvent volume is more than 95% of the injected solvent volume. The molecular sieve adsorption column is model 3A, the temperature is 25-30℃, the solvent flow rate is 10-15L / min, and the molecular sieve is loaded with 0.5%-1.0% of a heavy metal chelating agent. The heavy metal chelating agent is a mixture of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:1.

[0039] In this invention, the vacuum desolvation temperature is 46-48℃, the pressure is -0.09MPa, and the desolvation time is 28-32min. Nitrogen gas is used for intermittent purging at a rate of 0.5-1.0L / min, with each purging lasting 5min and an interval of 3min. Filtration is performed using an alumina ceramic filter membrane with a pore size of 0.25-0.4μm at a pressure of 0.35-0.45MPa. After filtration, the filter membrane is rinsed with deionized water.

[0040] This invention integrates raw material pretreatment, compound enzymatic hydrolysis and cell wall disruption, subcritical low-temperature extraction, gradient low-temperature separation, and solvent recovery and purification into a single process. With specific ratios and process parameters, it significantly improves the extraction rate of leek seed oil, retains the active components of the oil, reduces solvent residue, and enhances the purity and quality of the oil. At the same time, it achieves efficient solvent recovery and recycling, reduces production costs, and is suitable for industrial production.

[0041] Example 1:

[0042] (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually until the purity of leek seeds is ≥99%, dry with hot air circulation at 42℃ and wind speed controlled at 1.2m / s, dry to 6% moisture content, and use 0℃ low temperature liquid nitrogen to assist in pulverization. The amount of liquid nitrogen added is 8% of the mass of leek seeds. After pulverization, pass through a 45-mesh sieve to obtain leek seed powder.

[0043] (2) Complex enzymatic hydrolysis and cell wall breaking treatment: Add an acetate-sodium acetate buffer solution with pH 4.8 and a concentration of 0.1 mol / L to the leek seed powder, with a material-liquid ratio of 1:2.0. Then add a complex buffer regulator composed of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:2, with an addition amount of 0.8% of the leek seed powder mass. Add a complex bio-enzyme composed of cellulase, hemicellulase and pectinase in a mass ratio of 2:1:1, with an addition amount of 1.0% of the leek seed powder mass. Add proline and trehalose. An enzyme activity protectant, compounded at a mass ratio of 1:2, was added at 12% of the mass of the compound biological enzyme. The mixture was intermittently stirred at 80 r / min at a temperature of 48℃, with each stirring session lasting 10 min and an interval of 5 min. The enzymatic hydrolysis time was 1.8 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated by a water bath at 86℃ for 16 min. Vacuum filtration was then performed at a pressure of 0.3 MPa with a double-layer filter cloth pore size of 0.1 μm. The filter residue was dried at 40℃ until the moisture content was 5%, yielding enzymatically hydrolyzed and cell-wall broken leek seed powder.

[0044] (3) Subcritical low-temperature extraction: Enzymatically hydrolyzed and cell-wall broken leek seed powder and nano-silica adsorbent modified with silane coupling agent KH-550 were mixed evenly at a mass ratio of 100:2 and then loaded into the extraction vessel. The extraction vessel was evacuated to -0.09MPa, and a polarity-adjustable composite subcritical solvent of n-butane, isobutane and anhydrous ethanol at a volume ratio of 77:18:5 was injected. The amount of solvent used was 3 times the mass of the enzymatically hydrolyzed and cell-wall broken leek seed powder. The ultrasonic auxiliary device was turned on, with an ultrasonic frequency of 20kHz and a power of 500W. The ultrasonic waves were injected every 15 minutes. The process was started for 3 minutes. Dynamic countercurrent extraction was carried out at a temperature of 34℃ and a pressure of 0.9MPa. The flow rate was 1.8L / min·kg leek seed powder, and the extraction time was 50 minutes. During the extraction process, a pulse pressurization was performed every 12 minutes, with a pressurization increase of 0.12MPa and a duration of 1.0 minute each time. At the same time, the mixture was stirred at a speed of 90r / min. The stirring direction was switched every 20 minutes. When switching, the speed was first reduced to 50r / min, maintained for 30 seconds, and then returned to the original speed to obtain the extraction mixture.

[0045] (4) Gradient low-temperature separation and solvent recovery and purification integration: The extraction mixture is sent into the separator, and the solvent is condensed and recovered under the conditions of 36℃ and 0.45MPa. The condensation temperature is 5℃ and the recovery time is 35min. The volume of the recovered solvent is more than 95% of the volume of the injected solvent. The recovered solvent is purified by a 3A molecular sieve adsorption column. The molecular sieve temperature is 25℃ and the solvent flow rate is 10L / min. The molecular sieve is loaded with 0.5% of a heavy metal chelating agent composed of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:1. The remaining material is desolvated under vacuum at 46℃ and -0.09MPa for 28min. Nitrogen gas is used for intermittent purging at 0.5L / min, with each purging lasting 5min and an interval of 3min. The mixture is filtered using an alumina ceramic filter membrane with a pore size of 0.25μm and a pressure of 0.35MPa. After filtration, the filter membrane is rinsed with deionized water to obtain leek seed oil.

[0046] Example 2:

[0047] (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually until the purity of leek seeds is ≥99%, dry with hot air circulation at 48℃ and wind speed controlled at 1.4m / s, dry to 7% moisture content, and use 5℃ low temperature liquid nitrogen to assist in pulverization. The amount of liquid nitrogen added is 10% of the mass of leek seeds. After pulverization, pass through a 55-mesh sieve to obtain leek seed powder.

[0048] (2) Compound enzymatic hydrolysis and cell wall breaking treatment: Add an acetate-sodium acetate buffer solution with pH 5.2 and a concentration of 0.1 mol / L to the leek seed powder at a material-to-liquid ratio of 1:2.2. Then add a compound buffer regulator composed of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:2, at a dosage of 1.0% of the leek seed powder mass. Add a compound bio-enzyme composed of cellulase, hemicellulase, and pectinase in a mass ratio of 2:1:1, at a dosage of 1.2% of the leek seed powder mass. Add proline and trehalose in a mass ratio of 1:2:1:1. An enzyme activity protectant, formulated at a mass ratio of 1:2, was added at 14% of the mass of the compound biological enzyme. The mixture was intermittently stirred at 52℃ and 120 r / min, with each stirring session lasting 10 min and an interval of 5 min. The enzymatic hydrolysis time was 2.2 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated by a water bath at 88℃ for 18 min. Vacuum filtration was then performed at a pressure of 0.4 MPa with a double-layer filter cloth pore size of 0.2 μm. The filter residue was dried at 45℃ until the moisture content was 6%, yielding enzymatically hydrolyzed and cell-wall broken leek seed powder.

[0049] (3) Subcritical low-temperature extraction: Enzymatically hydrolyzed and cell-wall broken leek seed powder and nano-silica adsorbent modified with silane coupling agent KH-550 were mixed evenly at a mass ratio of 100:3 and then loaded into the extraction vessel. The extraction vessel was evacuated to -0.1MPa, and a polarity-adjustable composite subcritical solvent of n-butane, isobutane and anhydrous ethanol at a volume ratio of 78:18:5 was injected. The amount of solvent used was 3.5 times the mass of the enzymatically hydrolyzed and cell-wall broken leek seed powder. The ultrasonic auxiliary device was turned on with an ultrasonic frequency of 30kHz and a power of 800W. The ultrasonic waves were injected every 15 minutes. The process was started for 3 minutes. Dynamic countercurrent extraction was carried out at a temperature of 36℃ and a pressure of 1.1MPa, with a flow rate of 2.4L / min·kg leek seed powder and an extraction time of 60 minutes. During the extraction process, a pulse pressurization was performed every 15 minutes, with a pressurization increase of 0.18MPa and a duration of 1.8 minutes each time. At the same time, the mixture was stirred at a speed of 120r / min. The stirring direction was switched every 20 minutes. When switching, the speed was first reduced to 50r / min, maintained for 30 seconds, and then returned to the original speed to obtain the extraction mixture.

[0050] (4) Gradient low-temperature separation and solvent recovery and purification integration: The extraction mixture is sent into the separator, and the solvent is condensed and recovered under the conditions of 38℃ and 0.55MPa. The condensation temperature is 10℃ and the recovery time is 38min. The volume of the recovered solvent is more than 95% of the volume of the injected solvent. The recovered solvent is purified by a 3A molecular sieve adsorption column. The molecular sieve temperature is 30℃ and the solvent flow rate is 15L / min. The molecular sieve is loaded with 1.0% of a heavy metal chelating agent composed of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:1. The remaining material is desolvated under vacuum at 48℃ and -0.09MPa for 32min. Nitrogen gas is purged intermittently at 1.0L / min for 5min each time with a 3min interval. The filter is filtered using an alumina ceramic filter membrane with a pore size of 0.4μm and a pressure of 0.45MPa. After filtration, the filter membrane is rinsed with deionized water to obtain leek seed oil.

[0051] Example 3:

[0052] (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually until the purity of leek seeds is ≥99%, dry with hot air circulation at 45℃ and wind speed controlled at 1.3m / s, dry to a moisture content of 6.5%, and use 2.5℃ low temperature liquid nitrogen to assist in pulverization. The amount of liquid nitrogen added is 9% of the mass of leek seeds. After pulverization, pass through a 50-mesh sieve to obtain leek seed powder.

[0053] (2) Compound enzymatic hydrolysis and cell wall breaking treatment: Add an acetate-sodium acetate buffer solution with pH 5.0 and a concentration of 0.1 mol / L to the leek seed powder at a material-to-liquid ratio of 1:2.1. Then add a compound buffer regulator composed of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:2 at a mass ratio of 0.9% of the leek seed powder mass. Add a compound bio-enzyme composed of cellulase, hemicellulase and pectinase in a mass ratio of 2:1:1 at a mass ratio of 1.1% of the leek seed powder mass. Add proline and trehalose in a mass ratio of 1:1. An enzyme activity protectant with a 1:2 ratio was added at 13% of the mass of the compound biological enzyme. The mixture was intermittently stirred at 100 r / min at 50℃, with each stirring session lasting 10 min and an interval of 5 min. The enzymatic hydrolysis time was 2.0 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated by a water bath at 87℃ for 17 min. Vacuum filtration was then performed at a pressure of 0.35 MPa with a double-layer filter cloth pore size of 0.15 μm. The filter residue was dried at 42℃ until the moisture content was 5.5%, yielding enzymatically hydrolyzed and cell-wall broken leek seed powder.

[0054] (3) Subcritical low-temperature extraction: Enzymatically hydrolyzed and cell-wall broken leek seed powder and nano-silica adsorbent modified with silane coupling agent KH-550 were mixed evenly at a mass ratio of 100:2.5 and then loaded into the extraction vessel. The extraction vessel was evacuated to -0.095 MPa, and a polarity-adjustable composite subcritical solvent, a mixture of n-butane, isobutane and anhydrous ethanol at a volume ratio of 77.5:18:5, was injected. The amount of solvent used was 3.25 times the mass of the enzymatically hydrolyzed and cell-wall broken leek seed powder. The ultrasonic auxiliary device was turned on, with an ultrasonic frequency of 25 kHz and a power of 650 W. Every 15 seconds... The process was initiated and processed for 3 minutes. Dynamic countercurrent extraction was carried out at a temperature of 35℃ and a pressure of 1.0MPa, with a flow rate of 2.1L / min·kg leek seed powder and an extraction time of 55 minutes. During the extraction process, a pulse pressurization was performed every 13.5 minutes, with a pressure increase of 0.15MPa and a duration of 1.4 minutes each time. Simultaneously, the mixture was stirred at a speed of 105r / min. The stirring direction was switched every 20 minutes. When switching, the speed was first reduced to 50r / min, maintained for 30 seconds, and then returned to the original speed to obtain the extraction mixture.

[0055] (4) Gradient low-temperature separation and solvent recovery and purification integration: The extraction mixture is sent to the separator, and the solvent is condensed and recovered under the conditions of 37℃ and 0.5MPa. The condensation temperature is 7.5℃ and the recovery time is 36.5min. The volume of the recovered solvent is more than 95% of the volume of the injected solvent. The recovered solvent is purified by a 3A molecular sieve adsorption column. The molecular sieve temperature is 27.5℃ and the solvent flow rate is 12.5L / min. The molecular sieve is loaded with 0.75% of a heavy metal chelating agent composed of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:1. The remaining material is desolvated under vacuum at 47℃ and -0.09MPa for 30min. Nitrogen gas is purged intermittently at 0.75L / min for 5min each time with a 3min interval. The filter is filtered with an alumina ceramic filter membrane with a pore size of 0.325μm and a pressure of 0.4MPa. After filtration, the filter membrane is rinsed with deionized water to obtain leek seed oil.

[0056] Comparative Example 1:

[0057] The method of Example 3 is adopted, with the only difference being that step (2) of compound enzymatic hydrolysis and cell wall breaking treatment is omitted, and the leek seed powder obtained from the raw material pretreatment is directly subjected to step (3) subcritical low temperature extraction. The other parameters are exactly the same as those of Example 3.

[0058] Comparative Example 2:

[0059] The method of Example 3 is adopted, except that the nano-silica adsorbent modified with silane coupling agent KH-550 is not added in step (3), and the other parameters are exactly the same as those of Example 3.

[0060] Comparative Example 3:

[0061] The method of Example 3 was adopted, except that n-butane was used as the extraction solvent in step (3), and the composite solvent of n-butane, isobutane and anhydrous ethanol was not used. The other parameters were exactly the same as those of Example 3.

[0062] Comparative Example 4:

[0063] The method of Example 3 is adopted, except that in step (4), the solvent is simply condensed and recovered without purification by molecular sieve adsorption column and without nitrogen purging and desolvation. The other parameters are exactly the same as those of Example 3.

[0064] test:

[0065] Experiment 1: Leek Seed Oil Extraction Rate Test

[0066] Test method:

[0067] Equal amounts of leek seed raw materials were accurately weighed, and leek seed oil was prepared according to the methods of Examples 1-3 and Comparative Examples 1-4, respectively. All oil was collected and weighed, and the extraction rate was calculated. The average value was taken from three parallel tests. Extraction rate = (mass of leek seed oil / mass of total fat in leek seed raw materials) × 100%. The results are as follows:

[0068] Table 1

[0069] Sample number Extraction rate (%) Example 1 92.3 Example 2 92.7 Example 3 93.1 Comparative Example 1 71.5 Comparative Example 2 82.6 Comparative Example 3 78.3 Comparative Example 4 88.2

[0070] The extraction rates of Examples 1-3 were all ≥92.3%, significantly higher than those of the comparative examples. Comparative Example 1 did not undergo complex enzymatic hydrolysis to disrupt the cell walls of the leek seeds, resulting in insufficient oil extraction and a significant decrease in extraction rate. Comparative Example 2 did not add nano-silica adsorbents, leading to impurities easily encapsulating the oil during extraction and reducing mass transfer efficiency. Comparative Example 3 used a single solvent with poor polarity matching, resulting in insufficient oil extraction. Comparative Example 4 did not undergo solvent purification and thorough desolvation, leading to some oil loss with the solvent and a reduced extraction rate.

[0071] Experiment 2: Solvent Residue Test of Leek Seed Oil

[0072] Test method:

[0073] The solvent residue in the leek seed oil obtained in Examples 1-3 and Comparative Examples 1-4 was determined by gas chromatography. The average value was calculated from three parallel tests, in mg / kg. The results are as follows:

[0074] Table 2

[0075] Sample number Solvent residue (mg / kg) Example 1 1.2 Example 2 1.1 Example 3 1.0 Comparative Example 1 8.6 Comparative Example 2 5.3 Comparative Example 3 6.7 Comparative Example 4 12.4

[0076] In Examples 1-3, the residual solvent content was ≤1.2 mg / kg, which was much lower than that in the comparative examples. In Comparative Example 1, the cell wall was not broken, and the solvent was easily trapped inside the cell and difficult to remove. In Comparative Example 2, without the assistance of an adsorbent, the separation of solvent and oil became more difficult. In Comparative Example 3, the single solvent had poor volatility, resulting in a higher residual amount. In Comparative Example 4, without solvent purification and nitrogen purging desolvation, the solvent could not be effectively removed, resulting in the highest residual amount.

[0077] Experiment 3: Peroxide value test of leek seed oil:

[0078] Test method:

[0079] The peroxide value of the leek seed oils obtained in Examples 1-3 and Comparative Examples 1-4 was determined according to the conventional methods for oil quality testing. The average value was taken from three parallel tests, with units of mmol / kg. The results are as follows:

[0080] Table 3

[0081] Sample number Peroxide value (mmol / kg) Example 1 2.1 Example 2 2.0 Example 3 1.9 Comparative Example 1 5.8 Comparative Example 2 4.3 Comparative Example 3 4.9 Comparative Example 4 6.5

[0082] Examples 1-3 all had peroxide values ​​≤2.1 mmol / kg, indicating superior oil freshness and stability. Comparative Example 1 showed insufficient cell disruption, leading to prolonged extraction time and oil oxidation; Comparative Example 2 lacked an adsorbent, with impurities catalyzing oil oxidation; Comparative Example 3 had unsuitable solvent polarity, exacerbating oxidation during extraction; Comparative Example 4 had incomplete desolvation, with residual solvent promoting oxidation and a significantly increased peroxide value.

[0083] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A method for subcritical low-temperature extraction of leek seed oil, characterized in that, Includes the following steps: (1) Raw material pretreatment: Take leek seeds without mold, remove impurities manually, dry with hot air circulation, dry, crush and sieve to obtain leek seed powder; (2) Compound enzymatic hydrolysis and cell wall breaking treatment: Add buffer solution to the leek seed powder, then add compound buffer regulator, compound biological enzyme and enzyme activity protectant, stir and enzymatic hydrolysis, after enzymatic hydrolysis, inactivate enzyme, filter and dry to obtain enzymatic hydrolyzed cell wall breaking leek seed powder; (3) Subcritical low temperature extraction: After the enzymatically hydrolyzed and cell wall broken leek seed powder and nano silica adsorbent are mixed evenly, they are loaded into the extraction vessel, the extraction vessel is evacuated, and a polarity adjustable composite subcritical solvent is injected to carry out dynamic countercurrent extraction to obtain the extraction mixture. (4) Gradient low temperature separation and solvent recovery and purification integration: The extraction mixture is sent into the separator, the solvent is first condensed and recovered, the recovered solvent is purified by molecular sieve adsorption column, and the remaining material is vacuum desolventized and filtered to obtain leek seed oil. The composite bioenzyme is a mixture of cellulase, hemicellulase, and pectinase in a mass ratio of 2:1:1; the enzyme activity protectant is a mixture of proline and trehalose in a mass ratio of 1:2; the polarity-tunable composite subcritical solvent is a mixture of n-butane, isobutane, and anhydrous ethanol in a volume ratio of 77-78:18:5; the nano-silica adsorbent is nano-silica modified with silane coupling agent KH-550; and the composite buffer regulator is a mixture of sodium citrate and potassium dihydrogen phosphate in a mass ratio of 3:

2.

2. The method according to claim 1, characterized in that, In step (1), the leek seeds are manually cleaned until the purity is ≥99%. The hot air circulation drying temperature is 42-48℃ and the wind speed is controlled at 1.2-1.4m / s. The seeds are dried until the moisture content is 6%-7%. The crushing is assisted by liquid nitrogen at a low temperature of 0-5℃. The amount of liquid nitrogen added is 8%-10% of the mass of the leek seeds. After crushing, the seeds are passed through a 45-55 mesh sieve.

3. The method according to claim 1, characterized in that, In step (2), the buffer solution is an acetate-sodium acetate buffer solution with a pH of 4.8-5.2 and a concentration of 0.1 mol / L, and the material-liquid ratio is 1:2.0-2.2; the amount of compound buffer regulator added is 0.8%-1.0% of the mass of leek seed powder, the amount of compound biological enzyme added is 1.0%-1.2% of the mass of leek seed powder, and the amount of enzyme activity protectant added is 12%-14% of the mass of compound biological enzyme.

4. The method according to claim 1, characterized in that, In step (2), the enzymatic hydrolysis temperature is 48-52℃, the stirring is intermittent, the stirring speed is 80-120r / min, each stirring is 10min, with an interval of 5min, and the enzymatic hydrolysis time is 1.8-2.2h; the enzyme is inactivated by water bath at 86-88℃ for 16-18min; the filtration is carried out by vacuum filtration at a pressure of 0.3-0.4MPa, using double-layer filter cloth with a pore size of 0.1-0.2μm; the filter residue is dried at 40-45℃ until the moisture content is 5%-6%.

5. The method according to claim 1, characterized in that, In step (3), the mass ratio of enzymatically hydrolyzed cell wall broken leek seed powder to nano silica adsorbent is 100:2-3; an ultrasonic auxiliary device is set in the extraction vessel with an ultrasonic frequency of 20-30kHz and a power of 500-800W, and the device is turned on for 3 minutes every 15 minutes.

6. The method according to claim 1, characterized in that, In step (3), the extraction vessel is evacuated to -0.09~-0.1MPa, and the amount of polarity adjustable composite subcritical solvent is 3-3.5 times the mass of the enzymatically hydrolyzed and cell-wall broken leek seed powder. The dynamic countercurrent extraction temperature is 34-36℃, the pressure is 0.9-1.1MPa, the flow rate is 1.8-2.4L / min·kg leek seed powder, and the extraction time is 50-60min.

7. The method according to claim 1, characterized in that, In step (3), during the extraction process, a pulse pressurization is performed every 12-15 minutes, with a pressurization increase of 0.12-0.18 MPa and each lasting 1.0-1.8 minutes; at the same time, the stirring is performed at a speed of 90-120 r / min, and the stirring direction is switched every 20 minutes. When switching, the speed is first reduced to 50 r / min, maintained for 30 seconds, and then restored to the original speed.

8. The method according to claim 1, characterized in that, In step (4), the solvent condensation temperature is 36-38℃, the pressure is 0.45-0.55MPa, the condensation temperature is 5-10℃, the recovery time is 35-38min, and the volume of the recovered solvent is more than 95% of the volume of the injected solvent; the molecular sieve adsorption column is model 3A, the temperature is 25-30℃, the solvent flow rate is 10-15L / min, and the molecular sieve is loaded with 0.5%-1.0% of heavy metal chelating agent.

9. The method according to claim 8, characterized in that, The heavy metal chelating agent is a mixture of disodium ethylenediaminetetraacetate and sodium dimercaptopropanesulfonate in a mass ratio of 2:

1.

10. The method according to claim 1, characterized in that, In step (4), the vacuum desolvation temperature is 46-48℃, the pressure is -0.09MPa, the desolvation time is 28-32min, and the nitrogen is used for intermittent purging at 0.5-1.0L / min, with each purging lasting 5min and an interval of 3min. The filter is made of alumina ceramic filter membrane with a pore size of 0.25-0.4μm and the pressure is 0.35-0.45MPa. After filtration, the filter membrane is rinsed with deionized water.

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