Astaxanthin supercritical CO2 extraction process and special equipment

Abstract

The invention discloses an astaxanthin supercritical CO2 extraction process and special equipment, and relates to the field of astaxanthin preparation, the astaxanthin supercritical CO2 extraction process comprises a multistage wall-breaking granulation pretreatment stage and a dynamic countercurrent supercritical extraction stage, and liquid nitrogen low-temperature embrittlement is performed on a haematococcus pluvialis mud raw material; carrying out ultrahigh-pressure homogenization wall breaking on the algae mud subjected to low-temperature embrittlement to obtain wall-broken algae powder; carrying out vacuum belt type drying on the wall-broken algae powder, and removing moisture to a critical value; and preparing high-porosity particles from the dried wall-broken algae powder, porous starch, lecithin and nano calcium carbonate. In the multi-stage wall breaking pretreatment stage, cell walls of haematococcus pluvialis are efficiently destroyed under the combined action of liquid nitrogen low-temperature embrittlement and ultrahigh-pressure homogeneous wall breaking, so that astaxanthin wrapped in cells is fully exposed; according to the prepared high-porosity particles, the specific surface area and the pore structure of the particles are greatly increased, the contact efficiency of supercritical CO2 and astaxanthin is enhanced, the problems that in a traditional technology, the astaxanthin is high in wrapping rate and difficult to dissolve out are solved, and the extraction rate is remarkably increased.

Description

Technical Field

[0001] The present invention relates to the technical field of astaxanthin preparation, in particular to an astaxanthin supercritical CO2 extraction process and special equipment. Background Art

[0002] As a powerful antioxidant, the efficiency of astaxanthin extraction technology directly affects product quality and application value. Currently, four major extraction technologies are used: physical and mechanical wall-breaking extraction, chemical solvent extraction, bio-enzymatic hydrolysis, and supercritical CO2 extraction.

[0003] Among them, the physical mechanical wall-breaking extraction method uses high-pressure homogenization to break the cell wall. Although it can maintain the activity of astaxanthin, the wall-breaking rate is only about 70%. To achieve a wall-breaking rate of more than 90%, the equipment pressure needs to reach more than 300MPa, which brings extremely high safety risks and more than 5 times the energy consumption cost. Ultrasonic airflow milling is a low-temperature milling under the protection of liquid nitrogen to avoid oxidation loss. However, the liquid nitrogen consumption reaches 2-3kg / kilogram of algae powder, and the processed micropowder is easy to agglomerate, forming a mass transfer barrier in subsequent extraction. Microwave-assisted extraction heats the cells through molecular polarization, but the thermosensitivity of astaxanthin leads to a degradation rate of 10-15%. More seriously, the local high temperature generated by microwaves can induce cis-trans isomerization of astaxanthin, reducing biological activity.

[0004] Chemical solvent extraction uses an ethanol-hexane mixture as an organic solvent, which is low-cost but carries the risk of excessive residual solvent. The subsequent desolventizing process also results in astaxanthin loss.

[0005] The enzyme cost of the biological enzymatic hydrolysis method is high, and the enzyme needs to be inactivated after cell wall breaking, which increases the complexity of the process.

[0006] Although supercritical CO2 extraction is recognized as the most promising green extraction method, it still has four major bottlenecks:

[0007] The challenge of cell wall disruption: Haematococcus pluvialis cell walls are 2-3μm thick, and the CO2 permeation efficiency during direct supercritical extraction is less than 40%. While pretreatment can be used, the additional step increases the risk of oxidation.

[0008] Energy consumption for drying raw materials: Algae mud contains 70% water, so drying requires a lot of energy. Direct extraction of wet algae also risks freezing and clogging the pipeline.

[0009] Poor extraction uniformity: Finely powdered algae powder forms a dense accumulation layer in the autoclave with a density of 0.8-1.2g / cm³, resulting in a channeling effect and extraction rates as low as 50% in some areas.

[0010] Solvent residue control: Although the entrainer ethanol can increase solubility, the traditional process has a residual of 1000-1500ppm, requiring additional distillation and purification, which increases costs. Summary of the Invention

[0011] In order to solve the technical problem of supercritical CO2 extraction of astaxanthin, the present invention provides a supercritical CO2 extraction process and dedicated equipment for astaxanthin. The following technical solutions are adopted:

[0012] An astaxanthin supercritical CO2 extraction process includes a multi-stage wall-breaking granulation pretreatment stage and a dynamic countercurrent supercritical extraction stage. The multi-stage wall-breaking granulation pretreatment stage includes the following steps:

[0013] Step 1, subjecting the Haematococcus pluvialis algae mud raw material to low-temperature embrittlement by liquid nitrogen;

[0014] Step 2: subjecting the algae mud after low-temperature embrittlement to ultra-high pressure homogenization to obtain broken algae powder;

[0015] Step 3: vacuum belt drying the broken algae powder to remove moisture to a critical value;

[0016] Step 4, preparing high-porosity particles using the dried broken algae powder, porous starch, lecithin and nano-calcium carbonate;

[0017] The dynamic countercurrent supercritical extraction stage includes the following steps:

[0018] Step 5: The prepared high-porosity particles are conveyed through a closed conveying system into a three-stage series extraction kettle with a decreasing entrainer ratio, CO2 concentration, and pressure;

[0019] Step 6, extracting in the first extraction kettle until the astaxanthin concentration in the CO2 at the kettle outlet drops to a first concentration threshold;

[0020] Step 7, transferring the reactants extracted in step 6 to a second extraction kettle for secondary extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a second concentration threshold;

[0021] Step 8: Transfer the reactants extracted in step 7 to a third extraction kettle for three-stage extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a third concentration threshold to complete the extraction.

[0022] Optionally, a Haematococcus pluvialis mud with a moisture content of 60%-70% and an initial astaxanthin content of 2.5mg / g-3.0mg / g is used; the mud is continuously fed into the feed port of the screw machine, and liquid nitrogen is sprayed into the mud when the screw is advanced to one-third and two-thirds respectively, with the flow rate stably controlled at 40L / min-60L / min; the mud is embrittled by cooling the temperature from room temperature to -48°C to -52°C within 8-12 seconds, and scanning electron microscopy observation shows that the density of cell wall microcracks increases to 200 / mm², completing low-temperature embrittlement.

[0023] Optionally, in step 2, the algae mud embrittled in step 1 and food-grade ethanol are put into a static mixer at a mass ratio of 1:(0.6-1), premixed at room temperature for 20-40 seconds, and the mixture premixed at room temperature is subjected to three-stage homogenization using a three-stage series ultra-high pressure homogenizer until the proportion of free astaxanthin in the broken algae powder is greater than or equal to 90%.

[0024] Optionally, in step 3, the critical value of moisture is that the moisture content is stabilized at 7.5-8.5%.

[0025] Optionally, in step 4, the high-porosity particles include the following components: 85wt%-92wt% of broken-wall algae powder, 7wt%-9wt% of porous starch, 1.5wt%-2.5wt% of lecithin, and 0.3wt%-0.7wt% of nano-calcium carbonate.

[0026] Optionally, in step 4, the high-porosity particles are prepared by: first, the broken algae powder, porous starch, and nano-calcium carbonate are put into a mixer according to a weight ratio and dry-mixed for 4-6 minutes; then, lecithin is dissolved in a 5% ethanol solution, sprayed into the mixer through a top spray device, and the mixing is continued for 4-6 minutes;

[0027] The mixed material is fed into a screw extrusion granulator, extruded through a die head, and cut into granules by a 7-9 m / s airflow; the granules are classified by a vibrating screen, and 0.2-0.5 mm particle size particles are selected to obtain high-porosity granules with a granular porosity of 65-70%.

[0028] Optionally, the initial astaxanthin content of the particles in the first extraction kettle is 2.2-2.8 mg / g, the extraction pressure is 31.5-32.5 MPa, the temperature is 48-52°C, the CO2 flow rate is 580-620 L / h, the entrainer ratio is (1.4-1.6):1, and the stirring speed is 80-120 rpm; the astaxanthin concentration in the CO2 is monitored in real time by an ultraviolet detector at the outlet of the first extraction kettle. When the astaxanthin concentration in the outlet CO2 drops to 0.9-1.1 mg / mL, the primary extraction is stopped and the particles are transferred to the second extraction kettle via a screw conveyor at the bottom of the kettle. The transfer time is less than or equal to 5 minutes.

[0029] The extraction pressure in the second extraction kettle is 29.5-30.5 MPa, the temperature is 43-46°C, the CO2 flow rate is 540-560 L / h, the entrainer ratio is (1.1-1.3):1, and the stirring speed is 80-120 rpm. When the astaxanthin concentration in the CO2 at the outlet of the second extraction kettle drops to 0.4-0.6 mg / mL, the secondary extraction is stopped and the particles are transferred to the third extraction kettle.

[0030] The extraction pressure in the third extraction kettle is 27.5-28.5 MPa, the temperature is 38-42°C, the CO2 flow rate is 490-510 L / h, the entrainer ratio is (0.7-0.9):1, and the stirring speed is 80-120 rpm; when the astaxanthin concentration in the CO2 at the outlet of the third extraction kettle drops to 0.09-0.11 mg / mL, the tertiary extraction is stopped.

[0031] Alternatively, the entrainer is a 0.1% rosmarinic acid solution in ethanol.

[0032] Optionally, step 9 is also included, wherein the CO2, astaxanthin, and entrainer mixed outlet of the third extraction kettle is connected to the inlet of the fourth-stage separation kettle, and the outlet of the fourth-stage separation kettle is connected to the astaxanthin product collection tank and the CO2 reflux pipe respectively.

[0033] A special equipment for astaxanthin supercritical CO2 extraction process, comprising a twin-screw spiral freezer, a static mixer, a three-stage series ultrahigh pressure homogenizer, a three-stage vacuum belt dryer, a twin-screw mixer, a spiral extrusion granulator, a vibrating screening machine, a closed pneumatic conveying system, a three-stage series extraction kettle and a four-stage separation kettle, wherein the twin-screw spiral freezer is used to perform liquid nitrogen low-temperature embrittlement on Haematococcus pluvialis algae mud raw material, the inlet of the static mixer is connected to the outlet of the spiral freezer, the inlet of the three-stage series ultrahigh pressure homogenizer is connected to the outlet of the mixer, and is used to perform ultrahigh pressure homogenization and wall breaking on the low-temperature embrittled algae mud to obtain wall-broken algae powder, and the inlet of the three-stage vacuum belt dryer is connected to the outlet of the three-stage series ultrahigh pressure homogenizer. It is used for vacuum belt drying of broken wall algae powder. The feed port of the twin-screw mixer is connected to the outlet of the vacuum belt drying of the broken wall algae powder. The auxiliary material storage tanks are added to the twin-screw mixer according to the formula ratio through the metering valve. The inlet of the spiral extrusion granulator is connected to the outlet of the twin-screw mixer for granulation. The vibration screening machine screens the particles to obtain high-porosity particles. The qualified particle outlet of the vibration screening machine is connected to the inlet of the first extraction kettle of the three-stage series extraction kettle through a closed pneumatic conveying system. The three-stage series extraction kettle is used for three-stage extraction of high-porosity particles. The inlet of the four-stage separation kettle is connected to the CO2, astaxanthin, and entrainer mixed outlet of the third extraction kettle of the three-stage series extraction kettle, and is used to separate astaxanthin and entrainer.

[0034] In summary, the present invention includes at least one of the following beneficial technical effects:

[0035] The present invention can provide an astaxanthin supercritical CO2 extraction process and special equipment. In the multi-stage wall-breaking pretreatment stage, the cell walls of Haematococcus pluvialis can be efficiently destroyed through the combined effects of liquid nitrogen low-temperature embrittlement and ultra-high-pressure homogenization wall-breaking, so that the astaxanthin encapsulated in the cells is fully exposed; the high-porosity particles prepared subsequently greatly increase the specific surface area and pore structure of the particles, enhance the contact efficiency between supercritical CO2 and astaxanthin, solve the problems of high astaxanthin encapsulation rate and difficult dissolution in traditional processes, and significantly improve the extraction rate.

[0036] Multi-stage wall breaking and pretreatment of high-porosity particles shorten the equilibrium time of supercritical extraction and increase the output per unit time; the three-level gradient parameter design can match the solubility characteristics of astaxanthin at different extraction stages, avoid energy waste caused by high-parameter operation throughout the process, and reduce production costs; each link can achieve continuous operation, the equipment has strong connectivity, and is suitable for large-scale industrial production.

[0037] Supercritical CO2 as an extraction agent is non-toxic, easy to recycle, and leaves no residue. Combined with the use of no organic solvents in the pretreatment stage, it avoids the chemical residue problems caused by traditional solvent extraction. At the same time, there is no wastewater or waste gas emissions throughout the process, which meets the requirements of green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic flow diagram of a supercritical CO2 extraction process for astaxanthin according to the present invention;

[0039] Figure 2 This is a schematic diagram of the effect of broken algae powder in the supercritical CO2 extraction process of astaxanthin in the present invention;

[0040] Figure 3 This is a schematic diagram of the effect of high-porosity particles in the astaxanthin supercritical CO2 extraction process of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings.

[0042] The embodiment of the present invention discloses an astaxanthin supercritical CO2 extraction process and special equipment.

[0043] Reference Figure 1-Figure 3 Example 1: A supercritical CO2 extraction process for astaxanthin, comprising a multi-stage wall-breaking granulation pretreatment stage and a dynamic countercurrent supercritical extraction stage. The multi-stage wall-breaking granulation pretreatment stage comprises the following steps:

[0044] Step 1, subjecting the Haematococcus pluvialis algae mud raw material to low-temperature embrittlement by liquid nitrogen;

[0045] Step 2: subjecting the algae mud after low-temperature embrittlement to ultra-high pressure homogenization to obtain broken algae powder;

[0046] Step 3: vacuum belt drying the broken algae powder to remove moisture to a critical value;

[0047] Step 4, preparing high-porosity particles using the dried broken algae powder, porous starch, lecithin and nano-calcium carbonate;

[0048] The dynamic countercurrent supercritical extraction stage includes the following steps:

[0049] Step 5: The prepared high-porosity particles are conveyed through a closed conveying system into a three-stage series extraction kettle with a decreasing entrainer ratio, CO2 concentration, and pressure;

[0050] Step 6, extracting in the first extraction kettle until the astaxanthin concentration in the CO2 at the kettle outlet drops to a first concentration threshold;

[0051] Step 7, transferring the reactants extracted in step 6 to a second extraction kettle for secondary extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a second concentration threshold;

[0052] Step 8: Transfer the reactants extracted in step 7 to a third extraction kettle for three-stage extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a third concentration threshold to complete the extraction.

[0053] By adopting the above technical solution, the multi-stage wall-breaking pretreatment stage can effectively destroy the cell walls of Haematococcus pluvialis through the combined effects of liquid nitrogen low-temperature embrittlement and ultra-high pressure homogenization wall-breaking, so that the astaxanthin encapsulated in the cells is fully exposed; the high-porosity particles prepared subsequently greatly increase the specific surface area and pore structure of the particles, enhance the contact efficiency between supercritical CO2 and astaxanthin, solve the problems of high astaxanthin encapsulation rate and difficult dissolution in traditional processes, and significantly improve the extraction rate.

[0054] The liquid nitrogen low-temperature embrittlement and vacuum belt drying in the pretreatment stage are both carried out in a low-temperature, low-oxygen environment, which can reduce the degradation of astaxanthin (an easily oxidizable substance) caused by exposure to high temperature and oxygen;

[0055] Supercritical CO2 itself is an inert medium, and the entire process uses a closed conveying system to reduce the contact between materials and air, further reducing the risk of oxidation and effectively retaining the biological activity of astaxanthin (such as antioxidant capacity).

[0056] The dynamic countercurrent supercritical extraction stage uses a three-stage series extraction kettle and a gradient decreasing parameter design (entrainer ratio, CO2 concentration, pressure) to specifically separate astaxanthin in different states:

[0057] In the first kettle, free and soluble astaxanthin was preferentially extracted under high parameter conditions;

[0058] The parameters of the second and third kettles are gradually reduced to extract the bound and insoluble astaxanthin, reduce the co-extraction of impurities (such as polysaccharides and pigments), and improve the purity of the product.

[0059] Transfer control based on the outlet concentration threshold can accurately terminate extraction at each stage, avoid impurities caused by over-extraction, and further improve selectivity.

[0060] Multi-stage wall breaking and pretreatment of high-porosity particles shorten the equilibrium time of supercritical extraction and increase the output per unit time; the three-level gradient parameter design can match the solubility characteristics of astaxanthin at different extraction stages, avoid energy waste caused by high-parameter operation throughout the process, and reduce production costs; each link (such as homogenization, drying, transportation, and extraction) can be operated continuously, with strong equipment connectivity, suitable for large-scale industrial production.

[0061] Supercritical CO2 as an extraction agent is non-toxic, easy to recycle, and leaves no residue. Combined with the use of no organic solvents in the pretreatment stage, it avoids the chemical residue problems caused by traditional solvent extraction (such as ethanol and acetone). At the same time, there is no wastewater or waste gas emissions throughout the process, which meets the requirements of green production.

[0062] In Example 2, a Haematococcus pluvialis algae mud with a moisture content of 60%-70% and an initial astaxanthin content of 2.5 mg / g-3.0 mg / g was used; the algae mud was continuously fed through the feed port of the screw machine, and liquid nitrogen was sprayed into the screw machine when the screw was advanced to one-third and two-thirds, respectively, with a flow rate stably controlled at 40 L / min-60 L / min; the algae mud was embrittled by cooling from room temperature to -48°C to -52°C within 8-12 seconds, and scanning electron microscopy observation showed that the density of cell wall microcracks increased to 200 / mm², completing low-temperature embrittlement.

[0063] By adopting the above technical solution, a process is designed for Haematococcus pluvialis algae mud with a moisture content of 60%-70%. This moisture content range can not only ensure that the algae mud has a certain fluidity for continuous transportation, but also can generate sufficient mechanical force to destroy the cell wall due to the rapid crystallization of water at low temperature, avoiding the problem of over-drying or over-wetting, and significantly improving the adaptability of the embrittlement process to the raw materials.

[0064] By adopting the method of continuous feeding with a screw machine and segmented spraying of liquid nitrogen, the continuous operation of low-temperature embrittlement of algae mud is realized, avoiding the efficiency bottleneck of intermittent treatment; at the same time, the liquid nitrogen flow rate is stably controlled at 40L / min-60L / min, preferably 50L / min. The flow rate can be adjusted to match the feed speed to ensure process stability and facilitate large-scale industrial production.

[0065] The algae mud is cooled from room temperature to -50°C within 8-12 seconds. The ultra-rapid low temperature causes the water inside the algae mud to crystallize instantly. The mechanical force generated by the expansion of the ice crystals can efficiently tear the cell walls. The final density of cell wall microcracks reaches 200 / mm², indicating that the cell wall is fully destroyed, laying the foundation for the subsequent ultra-high pressure homogenization breaking of the cell wall in step 2. The presence of microcracks can reduce the pressure requirement during homogenization, reduce energy consumption, and at the same time make the cell wall more completely broken during the homogenization process, improving the breaking efficiency.

[0066] Using liquid nitrogen for low-temperature embrittlement avoids the damage to heat-sensitive astaxanthin (which is susceptible to oxidative degradation at high temperatures). While effectively destroying the cell wall, the low temperature environment stabilizes the astaxanthin structure, preserving more active ingredients for subsequent extraction, thereby improving the yield and purity of the final product.

[0067] In Example 3, in step 2, the algae mud embrittled in step 1 and food-grade ethanol are placed in a static mixer at a mass ratio of 1:(0.6-1), premixed at room temperature for 20-40 seconds, and the mixture premixed at room temperature is subjected to three-stage homogenization using a three-stage series ultra-high pressure homogenizer until the proportion of free astaxanthin in the broken algae powder is greater than or equal to 90%.

[0068] By adopting the above technical solution, food-grade ethanol is mixed with embrittled algae mud in a mass ratio of 1:(0.6-1), preferably 1:0.8. Ethanol can penetrate into the cell walls that have already produced microcracks in step 1 through osmosis. On the one hand, it softens the lipid layer and cellulose structure of the cell wall, reducing the mechanical resistance during homogenization. On the other hand, ethanol, as a polar medium, can form a synergistic effect with the water in the algae cells, enhancing the osmotic pressure difference between the inside and outside of the cell, and promoting the cell wall to rupture more easily under the homogenization pressure. At the same time, the use of food-grade ethanol avoids the risk of chemical residues and ensures the safety of subsequent products.

[0069] Premixing for 30 seconds at room temperature in a static mixer allows ethanol to evenly penetrate the algae mud and fully contact the brittle microcracks. This provides a pretreatment buffer for subsequent ultrahigh-pressure homogenization, avoiding variations in the cell wall breaking effect caused by localized ethanol concentration variations. Furthermore, short-term premixing at room temperature reduces oxidative degradation of astaxanthin caused by high temperatures or prolonged treatment, further protecting its activity. Static mixers have no moving parts, making them suitable for continuous operation. They integrate with the screw feeder and homogenizer to enhance process continuity.

[0070] The three-stage ultra-high-pressure homogenizer uses a stepped pressure mechanism (typically initial fragmentation in the first stage, crack refinement in the second stage, and complete cell wall tearing in the third stage) to gradually intensify the mechanical shearing, impact, and cavitation effects on algal cells. Compared to single-stage homogenization, this process is more effective in preventing material agglomeration or incomplete fragmentation caused by localized over-crushing. Ultimately, the free astaxanthin content is ≥90%, effectively releasing the astaxanthin from its intracellular encapsulation, providing an easily accessible free substrate for the subsequent supercritical extraction stage. This significantly reduces extraction resistance and directly improves the final extraction yield.

[0071] In Example 4, in step 3, the critical value of moisture is that the moisture content is stabilized at 7.5-8.5%.

[0072] By adopting the above technical solution, the critical moisture content in step 3 is a stable moisture content of 7.5-8.5%, preferably 8%. At a stable moisture content of 8%, the cracked algae powder will neither be too dry, resulting in a brittle texture and reduced adhesion to excipients such as porous starch and lecithin, nor too wet, resulting in granule adhesion and filling of pores with water after molding. This moisture content allows for the formation of appropriate hydrogen bonds and van der Waals forces between excipients, ensuring a stable granule structure during granulation, ultimately yielding uniform granules with high porosity.

[0073] In Example 5, in step 4, the high-porosity particles include the following components: 85 wt%-92 wt% of broken-wall algae powder, 7 wt%-9 wt% of porous starch, 1.5 wt%-2.5 wt% of lecithin, and 0.3 wt%-0.7 wt% of nano-calcium carbonate.

[0074] In Example 6, in step 4, the high-porosity particles are prepared by first placing the broken algae powder, porous starch, and nano-calcium carbonate in a mixer according to a weight ratio and dry-mixing them for 4-6 minutes; then dissolving lecithin in a 5% ethanol solution and spraying the solution through a top spray device, and continuing to mix for 4-6 minutes;

[0075] The mixed material is fed into a screw extrusion granulator, extruded through a die head, and cut into granules by a 7-9 m / s airflow; the granules are classified by a vibrating screen, and 0.2-0.5 mm particle size particles are selected to obtain high-porosity granules with a granular porosity of 65-70%.

[0076] By adopting the above technical solution, the high-porosity particles include the following components: 90wt% cracked algae powder, 8wt% porous starch, 2wt% lecithin, and 0.5wt% nano-calcium carbonate. The cracked algae powder accounts for 85-92wt% and serves as the primary carrier for astaxanthin. While ensuring a high loading capacity, it is balanced with other excipients to avoid the dense particles caused by an excessively high algae powder content. The porous starch, with its inherent honeycomb porous structure, serves as a pore framework, complementing the loose structure of the cracked algae powder to create a continuous pore network. Lecithin, a natural surfactant and binder, reduces the interfacial tension between the algae powder and starch while maintaining the pore structure through moderate adhesion. Its lipophilicity enhances the compatibility of astaxanthin. Nano-calcium carbonate, an inorganic filler, refines the pore distribution through nanoscale particle size and regulates the pH of the particle microenvironment. These four components work together to achieve a combination of high loading capacity, high porosity, and high stability.

[0077] The pore structure of porous starch provides a diffusion channel for supercritical CO2, the emulsifying property of lecithin can promote the desorption of astaxanthin from the algae powder matrix, and the rigid structure of nano-calcium carbonate enhances the compression resistance of the particles under extraction pressure. The three respectively empower from the three dimensions of mass transfer channel, desorption promotion, and structural stability, solving the problems of easy agglomeration, low porosity, and high extraction resistance in the granulation of pure algae powder.

[0078] First, dry-mix the broken-wall algae powder, porous starch and nano-calcium carbonate. Mechanical force can be used to fully disperse the solid particles and initially form a loose mixed system. Then, dissolve lecithin in a 5% ethanol solution and spray it in. Continue mixing to evenly coat the surface of the solid particles with lecithin, which not only plays a bonding role but also prevents residual liquid from clogging the pores due to the volatile nature of ethanol. Ultimately, the original pores of the porous starch and algae powder are retained.

[0079] Spiral extrusion granulation and airflow cutting can stabilize the particle size at 0.2-0.5mm by controlling the die head aperture and airflow velocity: the particles in this particle size range have a moderate specific surface area, and the surface of the particles formed by airflow cutting is rougher; vibration screen classification further ensures the uniformity of particle size, and ultimately stabilizes the particle porosity at 65-70%. The high porosity provides sufficient channels for the penetration and diffusion of supercritical CO2, greatly reducing the contact resistance between astaxanthin and the extraction medium, laying a key foundation for the efficient subsequent three-stage dynamic countercurrent extraction.

[0080] The porosity of 65-70% enables supercritical CO2 to quickly penetrate the interior of the particles and fully contact astaxanthin; the uniform particles of 0.2-0.5mm ensure that in the three-stage series extraction kettle, the gradually decreasing pressure and entrainer ratio can act evenly on each particle, ultimately achieving efficient and sufficient extraction of astaxanthin.

[0081] The antioxidant properties of lecithin and the weakly alkaline environment of nano-calcium carbonate work together to inhibit the oxidative degradation of free astaxanthin after wall breaking; the structure of the particles is stable after formation, which reduces material loss from the pretreatment to the extraction stage and ensures the activity and purity of astaxanthin in the final product.

[0082] In Example 7, the initial astaxanthin content of the particles in the first extraction kettle was 2.2-2.8 mg / g, the extraction pressure was 31.5-32.5 MPa, the temperature was 48-52° C., the CO2 flow rate was 580-620 L / h, the entrainer ratio was (1.4-1.6):1, and the stirring speed was 80-120 rpm; the astaxanthin concentration in the CO2 was monitored in real time by an ultraviolet detector at the outlet of the first extraction kettle. When the astaxanthin concentration in the outlet CO2 dropped to 0.9-1.1 mg / mL, the primary extraction was stopped and the particles were transferred to the second extraction kettle via a screw conveyor at the bottom of the kettle. The transfer time was less than or equal to 5 min.

[0083] The extraction pressure in the second extraction kettle is 29.5-30.5 MPa, the temperature is 43-46°C, the CO2 flow rate is 540-560 L / h, the entrainer ratio is (1.1-1.3):1, and the stirring speed is 80-120 rpm. When the astaxanthin concentration in the CO2 at the outlet of the second extraction kettle drops to 0.4-0.6 mg / mL, the secondary extraction is stopped and the particles are transferred to the third extraction kettle.

[0084] The extraction pressure in the third extraction kettle is 27.5-28.5 MPa, the temperature is 38-42°C, the CO2 flow rate is 490-510 L / h, the entrainer ratio is (0.7-0.9):1, and the stirring speed is 80-120 rpm; when the astaxanthin concentration in the CO2 at the outlet of the third extraction kettle drops to 0.09-0.11 mg / mL, the tertiary extraction is stopped.

[0085] In Example 8, the entrainer is an ethanol solution containing 0.1% rosmarinic acid.

[0086] By adopting the above technical solution, the pressure gradient of the three-stage extraction kettle decreases from 32MPa to 30MPa to 28MPa, the temperature gradient decreases from 50℃ to 45℃ to 40℃, the CO2 flow rate gradient decreases from 600L / h to 550L / h to 500L / h, and the entrainer ratio decreases in a step-by-step manner from 1.5:1 to 1.2:1 to 0.8:1, accurately matching the residual characteristics of astaxanthin in the particles:

[0087] The first kettle has high parameters, high pressure, high temperature, high flow rate, and high entrainer. The high pressure is used to increase the solubility of astaxanthin in supercritical CO2, and the high entrainer ratio strengthens desorption to quickly extract the soluble part.

[0088] The parameters in the second kettle are aimed at medium concentration residues. By appropriately lowering the parameters, energy consumption is reduced while ensuring the continuous dissolution of astaxanthin with medium solubility.

[0089] The low parameters of the third kettle are aimed at low concentration residues, and deep extraction is achieved through precise control to avoid excessive energy consumption.

[0090] The three-level synergy significantly increases the overall extraction rate, which is significantly more efficient than traditional single-parameter extraction.

[0091] All parameters are controlled within a small range of fluctuation to avoid fluctuations in astaxanthin solubility caused by drastic changes in parameters, ensuring consistent extraction results for each batch and solving the problem of poor batch reproducibility caused by extensive parameters in traditional processes.

[0092] Example 9 also includes step 9, wherein the CO2, astaxanthin, and entrainer mixed outlet of the third extraction kettle is connected to the inlet of the fourth-stage separation kettle, and the outlet of the fourth-stage separation kettle is connected to the astaxanthin product collection tank and the CO2 reflux pipe respectively.

[0093] By adopting the above technical solution, the mixed system (CO2, astaxanthin, and entrainer) at the outlet of the third extraction kettle is separated through a four-stage separation kettle. The multi-stage separation design can significantly improve the separation effect of astaxanthin from CO2 and entrainer, reduce the loss of astaxanthin during the separation process, and greatly improve the product recovery rate.

[0094] Guaranteed product purity: The four-stage separation kettle can more accurately separate astaxanthin from other components. Combined with the directional collection of the astaxanthin product collection tank, it can effectively avoid the mixing of impurities, ensuring that the final collected astaxanthin product has higher purity and more stable quality.

[0095] CO2 is recovered and reused through the reflux pipe, and the CO2 used as the extraction agent in supercritical extraction can be reintroduced into the previous extraction link, which significantly reduces the CO2 raw material consumption and production costs, complies with the green and environmentally friendly process concept, and reduces the burden on the environment.

[0096] Example 10, a special equipment for astaxanthin supercritical CO2 extraction process, including a twin-screw spiral freezer, a static mixer, a three-stage series ultra-high pressure homogenizer, a three-stage vacuum belt dryer, a twin-screw mixer, a spiral extrusion granulator, a vibrating screening machine, a closed pneumatic conveying system, a three-stage series extraction kettle and a four-stage separation kettle, the twin-screw spiral freezer is used to perform liquid nitrogen low-temperature embrittlement on the Haematococcus pluvialis algae mud raw material, the inlet of the static mixer is connected to the outlet of the spiral freezer, the inlet of the three-stage series ultra-high pressure homogenizer is connected to the outlet of the mixer, and is used to perform ultra-high pressure homogenization and wall breaking on the low-temperature embrittled algae mud to obtain broken wall algae powder, the inlet of the three-stage vacuum belt dryer is connected to the outlet of the three-stage series ultra-high pressure homogenizer The twin-screw mixer is connected to the vacuum belt drying outlet of the broken-wall algae powder, and each auxiliary material storage tank is added to the twin-screw mixer according to the formula ratio through a metering valve. The inlet of the spiral extrusion granulator is connected to the outlet of the twin-screw mixer for granulation. The vibration screening machine screens the particles to obtain high-porosity particles. The outlet of the qualified particles of the vibration screening machine is connected to the inlet of the first extraction kettle of the three-stage series extraction kettle through a closed pneumatic conveying system. The three-stage series extraction kettle is used to perform three-stage extraction on the high-porosity particles. The inlet of the four-stage separation kettle is connected to the CO2, astaxanthin, and entrainer mixed outlet of the third extraction kettle of the three-stage series extraction kettle, and is used to separate astaxanthin and entrainer.

[0097] The following specific embodiments are used to illustrate the implementation principle of the present invention:

[0098] Haematococcus pluvialis mud with a water content of 65% and an initial astaxanthin content of 2.8 mg / g;

[0099] Step 1, liquid nitrogen embrittlement: algae mud is continuously fed into a twin-screw spiral freezer (300kg / h), and liquid nitrogen at -196℃ is sprayed into the screw at 1 / 3 and 2 / 3 at a flow rate of 50L / min. The temperature is cooled to -50℃ within 10 seconds, and the density of cell wall microcracks reaches 200 / mm²;

[0100] Step 2: Ultra-high pressure homogenization: The embrittled algae mud and food-grade ethanol are placed in a static mixer at a mass ratio of 1:0.8 and premixed at room temperature for 30 seconds. The mixture is then processed in a three-stage series ultra-high pressure homogenizer (50 MPa to 150 MPa to 250 MPa) for 3 minutes, resulting in 92% free astaxanthin in the broken algae powder.

[0101] Step 3, vacuum drying: The broken algae mud is dried in a three-stage vacuum belt dryer (45°C to 40°C to 35°C, vacuum degree -0.08MPa) until the moisture content is stabilized at 8.0%;

[0102] Step 4, granulation:

[0103] Formula: broken algae powder 90wt%, porous starch 8wt%, lecithin 2wt%, nano calcium carbonate 0.5wt%;

[0104] Preparation: After dry mixing for 5 minutes, lecithin (dissolved in 5% ethanol) was sprayed in and mixed for another 5 minutes. Granulation was performed by spiral extrusion with an 8 m / s airflow cutter. Vibrating screens were used to obtain 0.2-0.5 mm particles with a porosity of 68% and a specific surface area of ​​18 m² / g.

[0105] Steps 5-8 Dynamic Countercurrent Extraction:

[0106] First extraction kettle: pressure 32 MPa, temperature 50°C, CO2 flow rate 600 L / h, entrainer (ethanol containing 0.1% rosmarinic acid) ratio 1.5:1, stirring 100 rpm, transfer when the outlet concentration drops to 1.0 mg / mL;

[0107] Second extraction kettle: pressure 30MPa, temperature 45℃, CO2 flow rate 550L / h, entrainer ratio 1.2:1, transfer when the outlet concentration drops to 0.5mg / mL;

[0108] The third extraction kettle: pressure 28MPa, temperature 40℃, CO2 flow rate 500L / h, entrainer ratio 0.8:1, terminated when the outlet concentration dropped to 0.1mg / mL;

[0109] The transfer time between kettles is 5 minutes, and the whole process is closed;

[0110] Step 9, separation: The mixed outlet is separated by a four-stage separation kettle (10MPa to 7MPa to 5MPa to 3MPa), and the astaxanthin product purity is 94.2% and the CO2 recovery rate is 95%.

[0111] The comparison results of this technical solution with the traditional process in terms of wall breaking rate, particle porosity, total extraction rate, product purity, astaxanthin oxidation loss, and solvent residue are shown in Table 1:

[0112] Table 1

[0113] Comparison Item This technical solution Traditional process (solvent extraction and single-stage supercritical fluidization) Improvement effect Broken wall rate 99.2% 70% (traditional homogenization + enzymatic hydrolysis) Increased by 41.7% Particle porosity 68% 30% (ungranulated or simply granulated) Increased by 126.7% Total extraction rate 93.5% 80% Increased by 16.9% Product purity 94.2% 82% (contains polysaccharides and pigment impurities) Increased by 14.9% Astaxanthin oxidative loss Less than 3% 12% (high temperature, oxygen exposure) Reduced by 75% Solvent residues Less than 10ppm (ethanol) 500-1000ppm (acetone / petroleum ether) Reduced by more than 98% Single batch production cycle 120min (3-stage extraction + separation) 300 min (single-stage extraction + multiple purifications) 60% reduction Drying energy consumption 40kWh / t (vacuum belt type) 100kWh / t (spray drying) 60% reduction <![CDATA[CO2 consumption]]> 0.8kg / kg product (95% recovery rate) 2.0kg / kg product (recovery rate 60%) 60% reduction

[0114] Through the collaborative innovation of multi-stage wall breaking, high-porosity granulation, and dynamic gradient extraction, it has surpassed traditional processes in extraction efficiency, product quality, and energy consumption, providing an efficient solution for the industrial production of astaxanthin.

[0115] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A supercritical CO2 extraction process for astaxanthin, characterized in that: The method includes a multi-stage wall-breaking granulation pretreatment stage and a dynamic countercurrent supercritical extraction stage. The multi-stage wall-breaking granulation pretreatment stage includes the following steps: Step 1, subjecting the Haematococcus pluvialis algae mud raw material to low-temperature embrittlement by liquid nitrogen; Step 2: subjecting the algae mud after low-temperature embrittlement to ultra-high pressure homogenization to obtain broken algae powder; Step 3: vacuum belt drying the broken algae powder to remove moisture to a critical value; Step 4, preparing high-porosity particles using the dried broken algae powder, porous starch, lecithin and nano-calcium carbonate; The dynamic countercurrent supercritical extraction stage includes the following steps: Step 5: The prepared high-porosity particles are conveyed through a closed conveying system into a three-stage series extraction kettle with a decreasing entrainer ratio, CO2 concentration, and pressure; Step 6, extracting in the first extraction kettle until the astaxanthin concentration in the CO2 at the kettle outlet drops to a first concentration threshold; Step 7, transferring the reactants extracted in step 6 to a second extraction kettle for secondary extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a second concentration threshold; Step 8: Transfer the reactants extracted in step 7 to a third extraction kettle for three-stage extraction until the astaxanthin concentration in the CO2 at the kettle outlet drops to a third concentration threshold to complete the extraction.

2. A supercritical CO2 extraction process for astaxanthin according to claim 1, characterized in that, In step 1, Haematococcus pluvialis mud with a moisture content of 60%-70% and an initial astaxanthin content of 2.5mg / g-3.0mg / g is used; the mud is continuously fed into the feed port of the screw machine, and liquid nitrogen is sprayed into the screw when the screw is advanced to one-third and two-thirds respectively, with the flow rate stably controlled at 40L / min-60L / min; the mud is embrittled by cooling the temperature from room temperature to -48°C to -52°C within 8-12 seconds, and scanning electron microscopy observation shows that the density of cell wall microcracks increases to 200 / mm², completing low-temperature embrittlement.

3. A supercritical CO2 extraction process for astaxanthin according to claim 1, characterized in that, In step 2, the algae mud embrittled in step 1 and food-grade ethanol are put into a static mixer at a mass ratio of 1: (0.6-1), premixed at room temperature for 20-40 seconds, and the mixture premixed at room temperature is homogenized in three stages using a three-stage series ultra-high pressure homogenizer until the proportion of free astaxanthin in the broken algae powder is greater than or equal to 90%.

4. A supercritical CO2 extraction process for astaxanthin according to claim 1, characterized in that, In step 3, the critical value of moisture is that the moisture content is stable at 7.5-8.5%.

5. A supercritical CO2 extraction process for astaxanthin according to claim 1, characterized in that, In step 4, the high-porosity particles include the following components: 85wt%-92wt% of broken-wall algae powder, 7wt%-9wt% of porous starch, 1.5wt%-2.5wt% of lecithin, and 0.3wt%-0.7wt% of nano-calcium carbonate.

6. A supercritical CO2 extraction process for astaxanthin according to claim 5, characterized in that, In step 4, the high-porosity particles are prepared by first placing the broken algae powder, porous starch, and nano-calcium carbonate in a mixer according to a weight ratio and dry mixing for 4-6 minutes, then dissolving lecithin in a 5% ethanol solution and spraying the solution through a top spray device, and continuing to mix for 4-6 minutes; The mixed material is fed into a screw extrusion granulator, extruded through a die head, and cut into granules by a 7-9 m / s airflow; the granules are classified by a vibrating screen, and 0.2-0.5 mm particle size particles are selected to obtain high-porosity granules with a granular porosity of 65-70%.

7. A supercritical CO2 extraction process for astaxanthin according to claim 6, characterized in that, The initial astaxanthin content of the particles in the first extraction kettle is 2.2-2.8 mg / g, the extraction pressure is 31.5-32.5 MPa, the temperature is 48-52°C, the CO2 flow rate is 580-620 L / h, the entrainer ratio is (1.4-1.6):1, and the stirring speed is 80-120 rpm. The astaxanthin concentration in the CO2 is monitored in real time by a UV detector at the outlet of the first extraction kettle. When the astaxanthin concentration in the outlet CO2 drops to 0.9-1.1 mg / mL, the primary extraction is stopped and the particles are transferred to the second extraction kettle via a screw conveyor at the bottom of the kettle. The transfer time is less than or equal to 5 minutes. The extraction pressure in the second extraction kettle is 29.5-30.5 MPa, the temperature is 43-46°C, the CO2 flow rate is 540-560 L / h, the entrainer ratio is (1.1-1.3):1, and the stirring speed is 80-120 rpm. When the astaxanthin concentration in the CO2 at the outlet of the second extraction kettle drops to 0.4-0.6 mg / mL, the secondary extraction is stopped and the particles are transferred to the third extraction kettle. The extraction pressure in the third extraction kettle is 27.5-28.5 MPa, the temperature is 38-42°C, the CO2 flow rate is 490-510 L / h, the entrainer ratio is (0.7-0.9):1, and the stirring speed is 80-120 rpm; when the astaxanthin concentration in the CO2 at the outlet of the third extraction kettle drops to 0.09-0.11 mg / mL, the tertiary extraction is stopped.

8. The supercritical CO2 extraction process for astaxanthin according to claim 7, characterized in that: The entrainer was an ethanol solution containing 0.1% rosmarinic acid.

9. The supercritical CO2 extraction process for astaxanthin according to claim 7, characterized in that: The process also includes step 9, wherein the mixed outlet of CO2, astaxanthin and entrainer of the third extraction kettle is connected to the inlet of the fourth-stage separation kettle, and the outlet of the fourth-stage separation kettle is connected to the astaxanthin product collection tank and the CO2 reflux pipe respectively.

10. A dedicated device for the supercritical CO2 extraction process of astaxanthin according to any one of claims 1 to 9, characterized in that: The invention comprises a twin-screw spiral freezer, a static mixer, a three-stage series ultra-high pressure homogenizer, a three-stage vacuum belt dryer, a twin-screw mixer, a spiral extrusion granulator, a vibrating screening machine, a closed pneumatic conveying system, a three-stage series extraction kettle and a four-stage separation kettle. The twin-screw spiral freezer is used to perform liquid nitrogen low-temperature embrittlement on the Haematococcus pluvialis algae mud raw material. The inlet of the static mixer is connected to the outlet of the spiral freezer. The inlet of the three-stage series ultra-high pressure homogenizer is connected to the outlet of the mixer to perform ultra-high pressure homogenization and wall breaking on the low-temperature embrittled algae mud to obtain wall-broken algae powder. The inlet of the three-stage vacuum belt dryer is connected to the outlet of the three-stage series ultra-high pressure homogenizer to perform vacuum belt drying on the broken wall algae powder. Drying, the feed port of the twin-screw mixer is connected to the vacuum belt drying outlet of the broken wall algae powder, and each auxiliary material storage tank is added to the twin-screw mixer according to the formula ratio through a metering valve. The inlet of the spiral extrusion granulator is connected to the outlet of the twin-screw mixer for granulation. The vibration screening machine screens the particles to obtain high-porosity particles. The qualified particle outlet of the vibration screening machine is connected to the inlet of the first extraction kettle of the three-stage series extraction kettle through a closed pneumatic conveying system. The three-stage series extraction kettle is used to perform three-stage extraction on the high-porosity particles. The inlet of the four-stage separation kettle is connected to the CO2, astaxanthin, and entrainer mixed outlet of the third extraction kettle of the three-stage series extraction kettle for separating astaxanthin and entrainer.

Images