A method for extracting and purifying lutein extract based on a composite solvent system

Abstract

This invention discloses a method for extracting and purifying lutein extract based on a composite solvent system, specifically relating to the field of natural product separation and extraction. The method involves mixing a crude extract containing lutein esters from marigold with a first composite solvent system. This allows lutein esters, oils, and resinous impurities in the crude extract to enter the liquid phase. Waxes are then precipitated by lowering the system temperature, resulting in a dispersion system containing the precipitated waxes. The first composite solvent system consists of a first organic solvent and a second organic solvent. By first introducing lutein esters, oils, and resinous impurities into the liquid phase in the first composite solvent system, then allowing the waxes to precipitate and separate, and subsequently transferring the lutein esters to a lutein ester-enriched phase, lutein can be separated from major accompanying impurities before entering the saponification and purification processes. This relatively reduces the burden on subsequent processes and alleviates issues such as slow stratification, increased entrainment, and batch fluctuations.

Description

Technical Field

[0001] This invention relates to the field of natural product separation and extraction technology, and more specifically, to a method for extracting and purifying lutein extract based on a composite solvent system. Background Technology

[0002] In the production process of lutein extract from marigold extract, as part of the technology related to the preparation of chemical pharmaceutical raw materials, most of the existing processes are focused on increasing the amount of lutein transferred out and the content of the finished product. The common approach is to first extract the lutein esters along with the oily substances from the marigold raw material, and then gradually reduce the impurity content through processes such as saponification, washing, dewaxing, adsorption separation or solvent refining. Taking the production scenario of chemical pharmaceutical raw materials where marigold flower granules are continuously fed into the extraction and purification production line after pretreatment and subsequent processes are required to be continuously connected as an example, under the condition that the wax content, oil content and resin content of the raw materials vary with batch, and phase separation, saponification, washing and concentration are required in the subsequent process, the wax, oil and resin impurities carried in the crude extract will continue to enter the subsequent processing stage. In this situation, existing routes often exhibit slow stratification, thickening of the intermediate layer, stickiness of the saponification system, significant entrainment of the washing liquid, and large fluctuations in the color and content of the concentrated product. The burden on subsequent processes increases significantly with the increase in the amount of impurities introduced from the previous stage, making it difficult to meet the requirements for content stability and batch consistency in the preparation of chemical pharmaceutical raw materials. The fundamental reason is that when the target component enters the subsequent processing flow, impurities have already entered the main processing system simultaneously. The subsequent purification steps can only be carried out passively under high impurity load conditions, making it difficult to simultaneously take into account yield, content, and batch stability. The technical problem to be solved by this application is: how to separate lutein from waxes, oils and resinous impurities before it enters the subsequent extraction and purification process in the preparation of lutein extract from marigold extract, which is used as a raw material for chemical pharmaceuticals, thereby reducing the burden of subsequent saponification and purification and improving the stability of lutein extract preparation. Summary of the Invention

[0003] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for extracting and purifying lutein extract based on a composite solvent system. By pre-separating waxes, oils, and resinous impurities sequentially using a composite solvent system before lutein enters the subsequent saponification and purification processes, and transferring lutein esters into an enriched phase before saponification, phase inversion, washing, and concentration, the problems mentioned in the background art are solved.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for extracting and purifying lutein extract based on a composite solvent system, comprising: S1. The crude extract containing lutein esters from marigolds is mixed with a first composite solvent system, so that the lutein esters, oils, and resinous impurities in the crude extract enter the liquid phase, and the wax is precipitated by lowering the system temperature, resulting in a dispersion system containing the precipitated wax; wherein, the first composite solvent system consists of a first organic solvent and a second organic solvent, the first organic solvent is used to dissolve the oils, and the second organic solvent is used to reduce the viscosity of the system containing the crude extract containing lutein esters and keep the lutein esters dispersed in the liquid phase. S2. The dispersion system is subjected to solid-liquid separation to separate the waxy solid phase and retain the dewaxed liquid phase after the wax is removed. The dewaxed liquid phase contains lutein esters, oils and resinous impurities, and the waxy solid phase is the waxy component that has been removed from the crude extract containing lutein esters. S3. Add the second composite solvent system to the dewaxed liquid phase and perform liquid-liquid mixing and static separation to transfer lutein esters from the dewaxed liquid phase to the lutein ester enriched phase, while oil and resinous impurities remain in the oil impurity phase. The second composite solvent system consists of a third organic solvent and a fourth organic solvent. The third organic solvent is used to increase the solubility of lutein esters in the lutein ester enriched phase, and the fourth organic solvent is used to reduce the amount of oil entrained into the lutein ester enriched phase. S4. After separating the lutein ester enriched phase, the lutein ester enriched phase is mixed with the alcohol-alkali saponification solution to convert the lutein ester into free lutein. After saponification, a third composite solvent system is added to the saponification solution and allowed to stand for stratification, so that the free lutein is transferred into the lutein product phase, and the fatty acid salts, residual alkali, and polar impurities generated by saponification are transferred into the saponification by-product phase. The third composite solvent system is composed of a fifth organic solvent. After being added to the mixed system after saponification, the fifth organic solvent forms a two-phase stratification with the saponification solution containing alcohol, residual alkali, and fatty acid salts, and is used to transfer the free lutein from the saponification solution into the organic phase. S5. Wash the lutein product phase with water to remove residual alkali and residual saponification byproducts, and retain the washed organic phase. S6. The washed organic phase is desolvated and concentrated to remove the organic solvent and obtain lutein extract.

[0005] In a preferred embodiment, S1 includes the following steps: S1-1. Select a first organic solvent that has a dissolving effect on the oil in the crude extract containing lutein ester as the first component in the first composite solvent system. The first organic solvent is one or more of n-hexane, heptane, cyclohexane, and petroleum ether. First, add the first organic solvent to the crude extract containing lutein ester and mix it, so that the oil in the crude extract containing lutein ester enters the liquid phase mainly composed of the first organic solvent, and the resinous impurities are dispersed in the liquid phase along with the oil. S1-2. Add a second organic solvent to the liquid phase obtained in S1-1 as the second component in the first composite solvent system. The second organic solvent is selected from those that are miscible with the first organic solvent and have a viscosity-reducing effect on the crude extract containing lutein esters, and keep the lutein esters in the liquid phase. The second organic solvent is one or more of acetone, ethyl acetate, isopropanol, and ethanol. After adding the second organic solvent, continue mixing until there are no more undispersed agglomerates in the crude extract containing lutein esters, and obtain the mixture before the wax precipitation. S1-3. Cool the mixture obtained in S1-2 before the wax precipitates until solid wax precipitates in the system and continue stirring to allow the wax to precipitate from the liquid phase, while lutein esters, oils and resinous impurities remain in the unprecipitated liquid phase, thus obtaining a dispersion system containing precipitated wax.

[0006] In a preferred embodiment, step S2 includes the following steps: S2-1. The dispersion system is fed into the solid-liquid separation process at the system temperature at the end of S1. The liquid phase and solid phase are separated by filtration or centrifugation to obtain a primary separated liquid phase and a waxy filter cake. The primary separated liquid phase serves as the main liquid phase of the dewaxing liquid phase, and the waxy filter cake is a solid phase containing waxy components and entrained liquid phase. S2-2. The wax filter cake is washed with a first organic solvent, so that the lutein esters, oils and resinous impurities entrained in the wax filter cake enter the washing liquid, and the washing liquid is incorporated into the first separation liquid phase to obtain a dewaxed liquid phase. The wax filter cake forms a wax solid phase after washing. The wax solid phase is the wax component that no longer enters the liquid phase in the first composite solvent system and at the system temperature at the end of S1. S2-3. Define the combined liquid of the primary separation liquid and the washing liquid as the dewaxing liquid phase, and use the dewaxing liquid phase as the feed liquid phase of S3.

[0007] In a preferred embodiment, step S3 includes the following steps: S3-1. First, add a third organic solvent to the dewaxed liquid phase and perform the first liquid-liquid mixing. This allows the lutein esters in the dewaxed liquid phase to form a lutein ester transfer liquid phase along with the third organic solvent, while the oil and resinous impurities in the dewaxed liquid phase remain in the original liquid phase to form the initial oil impurity phase. The third organic solvent can be one or more of acetone, ethyl acetate, isopropanol, and ethanol. After the third organic solvent is added, no waxy solids will precipitate in the system, and the lutein ester transfer liquid phase will remain in a fluid state. S3-2. Add a fourth organic solvent to the system obtained in S3-1 and perform a second liquid-liquid mixing. This allows the fourth organic solvent to enter the initial oil and impurity phase and reduce the dispersion of oil and impurities in the lutein ester transfer liquid phase. At the same time, it forms a clear stratification interface between the lutein ester transfer liquid phase and the initial oil and impurity phase, resulting in a stratified mixing system. The fourth organic solvent is selected from water, an aqueous solution of ethanol with a mass fraction of 5% to 30%, or an aqueous solution of isopropanol with a mass fraction of 5% to 30%. The fourth organic solvent is added after the third organic solvent is added and the first liquid-liquid mixing is completed.

[0008] In a preferred embodiment, step S3 further includes the following steps: S3-3. After the mixture to be separated is allowed to stand and separate into layers, the lutein ester enriched phase and the oil impurity phase are separated. The separated oil impurity phase is then washed with a third organic solvent so that the lutein esters entrained in the oil impurity phase enter the wash liquid. The wash liquid is then incorporated into the lutein ester enriched phase and used as the feed liquid phase for S4.

[0009] In a preferred embodiment, step S4 includes the following steps: S4-1. The lutein ester enriched phase and the alcohol-alkali saponification solution are mixed in two parts. First, the first part of the total amount of alcohol-alkali saponification solution is added and stirred to form a homogeneous saponification system. Then, the remaining alcohol-alkali saponification solution is added to continue saponification. The alcohol-alkali saponification solution is prepared by one or more of methanol, ethanol, and isopropanol and one or two of sodium hydroxide and potassium hydroxide. The first part of the alcohol-alkali saponification solution is used to expand the lutein ester enriched phase and enter the saponification contact state. The remaining alcohol-alkali saponification solution is used to further convert the unconverted lutein ester into free lutein. S4-2. During the saponification process, the saponification system is sampled and the composition of lutein esters and free lutein is determined. When lutein esters are no longer detected in the sampling results, saponification is stopped and the mixed system after saponification is obtained. The sampling and determination are performed using either thin-layer chromatography or high-performance liquid chromatography.

[0010] In a preferred embodiment, step S4 further includes the following steps: S4-3. Add the fifth organic solvent to the mixture after saponification and allow it to stand for the first time to separate the lutein product phase and the saponification by-product phase. Then, use the fifth organic solvent to wash the saponification by-product phase and allow it to stand for the second time to separate the phase. Incorporate the organic phase obtained from the second standing separation into the lutein product phase obtained from the first standing separation. The fifth organic solvent is selected from one or more of methyl tert-butyl ether, methyl isobutyl ketone, and heptane.

[0011] In a preferred embodiment, step S5 includes the following steps: S5-1. After mixing the lutein product phase with the washing water, let it stand to separate the organic phase and the aqueous phase. Take the separated aqueous phase to determine its pH value, and use the separated organic phase as the feed liquid phase for the next water wash. The washing water used in each water wash is deionized water or purified water. S5-2. Repeat S5-1 until the pH of the aqueous phase obtained from the most recent separation is neutral and fatty acid salts are no longer detected in the aqueous phase obtained from this separation. Then, retain the corresponding organic phase as the washed organic phase.

[0012] In a preferred embodiment, step S6 includes the following steps: S6-1. The washed organic phase is subjected to desolventization under reduced pressure, the distilled organic solvent is collected and the concentrated liquid after desolventization is retained. During the desolventization process, the concentrated liquid is kept in a flowing state and desolventization is continued during the continuous outflow of the distillate. S6-2. After no more distillate flows out of the concentrate obtained in S6-1, continue to concentrate the concentrate under reduced pressure until the organic solvent content in a unit sample is lower than the control index of the finished lutein extract. Stop the concentration and discharge the product to obtain lutein extract.

[0013] The technical effects and advantages of this invention are as follows: 1. By first introducing lutein esters, oils and resinous impurities into the liquid phase in the first composite solvent system, then allowing the wax to precipitate and separate, and subsequently transferring lutein esters into the lutein ester enrichment phase, lutein can be separated from the main accompanying impurities before entering the saponification and purification process, thereby relatively reducing the burden on subsequent processes and alleviating slow stratification, increased entrainment and batch fluctuations. 2. By performing solid-liquid separation on a dispersion system containing precipitated waxes while maintaining a predetermined phase state, and by washing the wax filter cake with a first organic solvent, lutein esters, oils and resinous impurities can be recovered while removing the wax components. This reduces the risk of the target components being lost with the solid phase to a certain extent and improves the material integrity of the dewaxed liquid phase. 3. By adding a second composite solvent system consisting of a third organic solvent and a fourth organic solvent to the dewaxing liquid phase, lutein esters are transferred into the lutein ester enrichment phase and oil and resin impurities are retained in the oil impurity phase. This can relatively reduce the amount of oil entrained into the subsequent saponification system, thereby relatively inhibiting the phenomenon of stickiness in the saponification system, thickening of the intermediate layer, and increased washing burden in the subsequent process. 4. By mixing the lutein ester enrichment phase with the alcohol-alkali saponification liquid in two stages, and using a fifth organic solvent to transfer free lutein into the lutein product phase after saponification, and allowing fatty acid salts and residual alkali to enter the saponification by-product phase, the conversion of lutein ester and by-products can be carried out in a separate manner, which helps to relatively reduce the residue of saponification by-products in the target phase. 5. By repeatedly washing the lutein product phase with water, and using the pH and fatty acid salt detection results of the most recently separated aqueous phase as the stopping criteria, residual alkali and residual saponification by-products can be gradually removed, thereby relatively improving the purity of the material entering the desolventizing and concentration stage, and helping to improve the stability of the state in the subsequent concentration stage. 6. By first subjecting the washed organic phase to desolventizing under reduced pressure and then concentrating it under reduced pressure, and using the organic solvent content in a unit sample as the basis for discharge control, the organic solvent removal process can be connected with the finished product formation process, thereby providing relatively stable process support for the control of residual solvents, appearance, and batch consistency of lutein extract. Attached Figure Description

[0014] Figure 1 This is a flowchart of the method steps of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0016] Refer to the instruction manual appendix Figure 1 The present invention provides a method for extracting and purifying lutein extract based on a composite solvent system, comprising: S1. The crude extract containing lutein esters from marigolds is mixed with a first composite solvent system, so that the lutein esters, oils, and resinous impurities in the crude extract enter the liquid phase, and the wax is precipitated by lowering the system temperature, resulting in a dispersion system containing the precipitated wax; wherein, the first composite solvent system consists of a first organic solvent and a second organic solvent, the first organic solvent is used to dissolve the oils, and the second organic solvent is used to reduce the viscosity of the system containing the crude extract containing lutein esters and keep the lutein esters dispersed in the liquid phase. In this embodiment, the purpose of S1 is to first use the first composite solvent system to transfer the transferable components in the crude extract containing lutein esters into the liquid phase, and then to precipitate the waxes first through controlled cooling, thereby separating the lutein esters, oils, and resinous impurities that need to be retained and enter the main processing path from the waxes that need to be preferentially removed at the starting point of the process. This process is not a simple dissolution and cooling treatment, but is organized around the material state of the crude extract containing lutein esters when it enters S1, the synergistic effect of the first organic solvent and the second organic solvent, and the phase window between wax precipitation and the retention of the lutein ester liquid phase. Therefore, in specific execution, it is first determined that the crude extract containing lutein esters is in a pumpable or agitated flow state when it enters S1, and then the three consecutive actions of pre-dispersion with the first organic solvent, viscosity reduction and expansion with the second organic solvent, and low-temperature wax precipitation are completed in sequence, thereby forming a dispersion system containing precipitated waxes for use in S2. The function of S1-1 is to first establish a liquid phase dominated by the first organic solvent, allowing the oils and resinous impurities migrating with the oils in the crude lutein ester extract to enter the liquid phase first, creating conditions for the subsequent addition of the second organic solvent to form a developable continuous phase. The input material is the crude lutein ester extract formed after marigold extraction, preliminary slag removal, and partial removal of the previous extraction solvent, as well as the first organic solvent as the first component of the first composite solvent system. The crude lutein ester extract is preferentially controlled to be a flowable, oleoresin-like material before entering this step. If it is semi-solid or pasty at room temperature, it is first heated to a state where the material is flowable and can be continuously stirred by a stirrer before being added, to avoid local agglomeration affecting oil release. The first organic solvent is selected according to the oil and hydrophobic content of the crude lutein ester extract. One or more of n-hexane, heptane, cyclohexane, and petroleum ether are selected to meet the dissolution requirements of the components. When it is necessary to reduce the subsequent solvent removal load, the first organic solvent with a lower boiling range and compatibility with the subsequent second organic solvent is preferred. When it is necessary to improve the carrying capacity of the oil, the first organic solvent that improves the flowability of the crude extract is preferred. After the first organic solvent is added to the crude extract containing lutein esters, mechanical stirring is performed. The stirring method is preferably paddle or anchor stirring. The stirring intensity is controlled to form a whole circulation flow of the crude extract in the container and to prevent the continuous adhesion of paste to the stirring shaft surface. It is not limited by the simple speed value. As mixing proceeds, the oil in the crude extract containing lutein esters enters the liquid phase mainly composed of the first organic solvent, and resinous impurities are dispersed in the liquid phase along with the oil. In this application, resinous impurities refer to hydrophobic accompanying impurities that enter the liquid phase along with the oil in this step and remain in the oil impurity phase in subsequent S3. The mixing endpoint is not summarized by experience or visual inspection, but determined by the process state: when samples are taken from the upper, middle and lower parts of the container, and no independent paste lumps are found in the three sample liquids, and the surface of the stirrer no longer continuously carries out undeveloped agglomerates, the pre-dispersion of the first organic solvent is determined to be complete. If there are still paste lumps deposited at the bottom or agglomerates attached to the axial surface, the current temperature is maintained and stirring is continued. If necessary, the first organic solvent is added in batches until the oil enters the liquid phase and forms a main liquid phase that can continue to develop. The function of S1-2 is to introduce a second organic solvent into the main liquid phase obtained in S1-1, reducing the viscosity of the crude lutein ester extract system, keeping the lutein ester in the liquid phase and eliminating undispersed agglomerates, thereby obtaining a wax-free pre-precipitation mixture suitable for subsequent low-temperature wax precipitation; the input state is the liquid phase obtained in S1-1 with the first organic solvent as the main component, and the second organic solvent as the second component of the first composite solvent system; the second organic solvent is selected based on being miscible with the first organic solvent, having a viscosity-reducing effect on the crude lutein ester extract, and not causing premature precipitation of lutein ester from the liquid phase after its addition. The principle for selecting the second organic solvent is to use one or more of acetone, ethyl acetate, isopropanol, and ethanol. If the first organic solvent is hexane, heptane, or petroleum ether and the system viscosity is high, acetone or ethyl acetate is preferred as the second organic solvent. If it is desired to maintain good process continuity with the third organic solvent system in S3, isopropanol or ethanol can be preferred as the second organic solvent. The second organic solvent is introduced into the liquid phase obtained in S1-1 in stages, with stirring continued after each addition, so that the second organic solvent gradually enters the system and weakens the adhesion between the residual viscous components in the crude extract. Function; the control basis for adding in stages is not a preset ratio, but the change in the system's fluidity and agglomeration state after each addition. If undispersed agglomerates still exist after this addition, the next part of the second organic solvent is added. When the system has formed a continuous flowing liquid phase and no new large agglomerates appear, the addition is stopped. Here, "undispersed agglomerates" refers to the crude extract residual agglomerates that cannot be dispersed by the liquid phase under stirring, maintain an independent paste-like morphology after stirring stops, and continue to exist at the bottom of the container or on the surface of the stirrer. The operation endpoint is determined according to the following conditions: when the stirring is uniform... After homogenization, samples were taken from the upper, middle, and lower parts of the solution. No undispersed agglomerates were detected in any of the three samples, and the crude extract did not re-agglomerate after a short period of standing at room temperature. This indicates that the mixture before wax precipitation was obtained. If local turbidity deepens, viscosity increases suddenly, or local solidification occurs after the addition of the second organic solvent, it indicates that the addition was too fast or the local concentration change was too large. Stirring should be maintained to rehomogenize the system. If necessary, the first organic solvent should be added to restore the continuous liquid phase. Then, the amount of the second organic solvent should be reduced and added again to ensure that the lutein ester remains dispersed in the liquid phase and does not precipitate prematurely. The purpose of S1-3 is to convert the wax into a solid phase through controlled cooling, provided that the mixture has already formed a stable liquid phase before the wax precipitates, while keeping lutein esters, oils, and resinous impurities in the unprecipitated liquid phase. This results in a dispersion system containing precipitated wax, creating a clearly defined phase condition for solid-liquid separation in S2. The input material is the mixture obtained in S1-2 before the wax precipitates. In this application, the wax refers to the high-melting-point hydrophobic component that precipitates in solid form in the first composite solvent system after cooling in this step. Cooling is preferably carried out using jacketed heat exchange, coil heat exchange, or external circulation heat exchange. Stirring is maintained continuously during the cooling process to ensure uniform temperature distribution within the system and avoid localized overcooling that would cause lutein esters and wax to precipitate together. The stirring intensity is designed to maintain uniform solid-liquid suspension without forming a large amount of fine foam. The cooling rate is not fixed at a single value but is set according to the process objective of "wax precipitation first, then separation." When stable waxy solids begin to appear in the system, do not immediately proceed to S2. Instead, continue stirring and maintaining the temperature at the current or slightly lower temperature for a period of time to allow the waxes that have met the precipitation conditions to precipitate as completely as possible. Simultaneously, observe whether the liquid phase remains in a continuous flow state. The cooling endpoint is determined by two criteria: first, the waxy solids continue to exist in the system and no significant new solids precipitate after maintaining the current temperature; second, the liquid phase can still be continuously moved by the stirrer without forming a complete gel or a large-area static layer adhering to the walls. When this state is reached, it is determined that the waxes have precipitated from the liquid phase, while lutein esters, oils, and resinous impurities remain in the unprecipitated liquid phase. A dispersion system containing precipitated wax is obtained, and this dispersion system is directly fed into S2 at the current system temperature. If significant thickening of the liquid phase, abnormal increase in the stirrer load, or a large amount of non-wax precipitate in addition to wax occurs during the cooling process, it indicates that the cooling is too fast or the second organic solvent is insufficient. In this case, stop the cooling process, maintain stirring, and add an appropriate amount of the second organic solvent to restore the continuity of the liquid phase, and then slowly cool down again. If no wax solids precipitate after a long cooling period, first check whether the amount of the second organic solvent added in S1-2 is too high, and re-establish the phase window for preferential wax precipitation by adding the first organic solvent or moderately reheating and then slowly cooling down. Through the above processing, S1 achieves the following: first, a main liquid phase that allows oily and resinous impurities to enter is established; then, a second organic solvent is used to expand the crude extract containing lutein esters from a high-viscosity state to a controllable liquid phase state; finally, low-temperature conditions are used to precipitate the wax from this liquid phase first, thus forming a dispersion system containing the precipitated wax that can be directly separated in subsequent S2. The key control point of this step is not the single temperature value, time value, or ratio value itself, but the input crude extract state, the combination relationship between the first and second organic solvents, the degree of elimination of undispersed agglomerates, and the phase control of wax precipitation first without lutein ester precipitation. In practical applications: When the crude extract containing lutein esters is a marigold oil resin material that is free at room temperature, n-hexane can be added first and stirred to allow the oil and resin impurities to enter the liquid phase dominated by n-hexane. Then, acetone or ethyl acetate is added in portions until there are no more undispersed agglomerates in the system. Subsequently, the system is cooled by a jacket while stirring is maintained, so that the wax precipitates first while the lutein esters remain in the unprecipitated liquid phase, resulting in a dispersion system containing precipitated wax that can be directly filtered or centrifuged by S2.

[0017] S2. The dispersion system is subjected to solid-liquid separation to separate the waxy solid phase and retain the dewaxed liquid phase after the wax is removed. The dewaxed liquid phase contains lutein esters, oils and resinous impurities, and the waxy solid phase is the waxy component that has been removed from the crude extract containing lutein esters. In this embodiment, S2 receives the dispersion system containing precipitated wax obtained from S1. Its purpose is to stably remove the precipitated wax from the system while keeping lutein esters, oils, and resinous impurities in the liquid phase. Furthermore, it reduces lutein ester loss by recovering the entrained liquid in the solid phase, ensuring that the dewaxed liquid phase entering S3 maintains clear component definitions and the integrity of the material source. The core of this process is not simply separating the solid and liquid, but maintaining the distribution state between the waxy solid phase and the unprecipitated liquid phase formed at the end of S1. This prevents the wax from re-entering the liquid phase due to temperature rise, improper washing, or inappropriate separation path selection, or the loss of lutein esters entrained in the waxy filter cake with the solid phase. Therefore, the solid-liquid separation, filter cake washing, and the definition and destination of the dewaxed liquid phase are explained in detail below. The function of S2-1 is to separate the waxy solid phase from the unprecipitated liquid phase in the dispersion system, retaining a primary separation liquid phase dominated by the liquid phase, providing a basis for subsequent washing, recovery, and dewaxing liquid phase formation; the input material is the dispersion system obtained at the end of S1; the dispersion system enters this step at the same temperature as at the end of S1, without prior heating or prolonged storage at room temperature, to prevent the precipitated wax from re-dissolving back into the liquid phase; the dispersion system is fed into the solid-liquid separation process at the current system temperature; when the waxy solid phase in the dispersion system is flocculent, flaky, or needle-like and can form a continuous solid layer on the filter medium surface, filtration is used for separation, preferably plate and frame filtration, bag filtration, or vacuum filtration; when the waxy solid phase particle size is fine, the velocity through the filter medium is too slow, or there is significant liquid entrainment after the filter cake is compacted, centrifugal separation is used, preferably horizontal screw centrifugation or basket centrifugation; filtration or centrifugation Throughout the process, the material is maintained within the system temperature range at the end of S1. Equipment and pipelines are preferentially kept warm or operated at low temperatures to prevent the waxy solid phase from partially melting due to contact with high-temperature components. The separation operation is controlled by ensuring continuous liquid outflow without significant solid outflow. After separation, a primary separated liquid phase and a waxy filter cake are obtained. The primary separated liquid phase is the mainstream material and is stored as the main liquid phase for subsequent dewaxing. The waxy filter cake is a solid phase containing waxy components and entrained liquid phase, which may still contain lutein esters, oils, and resinous impurities. If the filtrate gradually changes from clear to significantly turbid during filtration, it indicates that the pore size of the filter medium is too large or the filter cake layer has not yet stabilized. The turbid filtrate from the previous stage should be refluxed and filtered again. If the discharge contains significant fine wax particles during centrifugation, the feed rate should be reduced or the separation time extended until the liquid and solid phases are separated and stabilized. The function of S2-2 is to utilize the first organic solvent to recover the retainable components entrained in the wax filter cake into the liquid phase, while simultaneously ensuring that wax components that no longer enter the liquid phase at the system temperature at the end of S1 remain in the solid phase, thus forming a clearly defined wax solid phase and a complete dewaxing liquid phase. The input states are the wax filter cake obtained from S2-1 and the primary separation liquid phase, as well as the same first organic solvent as in S1. The first organic solvent is chosen instead of other solvents because it has already formed the main liquid phase environment in S1 that has a dissolving effect on oils. Washing with the same solvent can prevent local reprecipitation, clumping, or increased entrainment on the surface of the waxy filter cake due to abrupt changes in the solvent system. The first organic solvent is added to the waxy filter cake for washing. Washing methods can include surface spraying, re-slurrying followed by filtration, or displacement washing in a centrifuge. When the waxy filter cake is loose and thin, spray washing is preferred; when the waxy filter cake is heavily compacted and the internal entrainment is difficult to release, re-slurrying followed by separation is preferred. During washing, the system temperature is maintained at the end of S1; washing is not heated to prevent the wax from re-entering the liquid phase. The amount of organic solvent added is controlled to ensure that the entrained liquid in the waxy filter cake is fully replaced without the solid phase re-dispersing after washing. The washing liquid is collected after washing and incorporated into the primary separation liquid phase. The resulting liquid phase retains lutein esters, oils, and resinous impurities, and is used as feed for subsequent S3. The solid phase after washing is defined as the waxy solid phase. In this application, the waxy solid phase is not arbitrary filter cake residue, but rather the waxy component that does not re-enter the liquid phase after washing in the first composite solvent system and at the system temperature at the end of S1. The washing endpoint is not described empirically but by process parameters. Performance Judgment: When washing with the first organic solvent, if the color of the newly obtained washing solution is significantly close to the color of the first organic solvent itself, and no longer significantly carries yellow to orange-yellow components compared to the previous washing solution, stop washing. If the last washing solution is still significantly yellow or orange-yellow, it indicates that lutein esters are still trapped in the waxy filter cake, and an additional wash should be performed for separation. If the waxy filter cake softens significantly, collapses, or is lost in large quantities with the washing solution during the washing process, it indicates that the washing intensity is too high or the local temperature rises. The washing flow rate should be reduced or the temperature should be restored before continuing washing. The function of S2-3 is to unify the liquid phase materials obtained from S2-1 and S2-2 and explicitly transfer them to S3, ensuring consistency in the feed boundary for subsequent liquid-liquid distribution. The input states are the primary separated liquid phase obtained from S2-1 and the washing liquid obtained from S2-2. The combined liquid formed after combining the two is defined as the dewaxed liquid phase, without any new intermediate name. This dewaxed liquid phase contains lutein esters, oils, and resinous impurities retained in the liquid phase after S1, as well as the same components recovered from the entrainment liquid of the waxy filter cake. The merging is preferably carried out under conditions that are the same as or close to the system temperature at the end of S1, and a short stirring is performed after merging to make the primary separated liquid phase and the washing liquid a homogeneous single liquid phase. Then, the dewaxed liquid phase is... The feed liquid phase of S3 is directly fed into the next step. If local turbidity, a small amount of new solids, or floating wax flakes appear after merging, the current temperature is maintained and the liquid is allowed to stand for observation. If the solids can settle or float and can be separated, they are incorporated into the wax solid phase and are not carried into S3. If new wax precipitation continues to occur in the liquid phase after merging, it indicates that the temperature control during the washing or merging process is unstable. The new solid phase should be separated again, and the system should be kept at the system temperature at the end of S1 before being transferred to S3. By this definition, the dewaxing liquid phase received by S3 is neither a single separated liquid phase nor an arbitrary washing liquid, but a complete feed liquid phase formed by the merging of the two, thereby ensuring that the material source, component boundaries, and dependencies between the preceding and following steps of S3 remain consistent. Through the above treatment, S2 separates the waxy solid phase from the unprecipitated liquid phase in the dispersion system obtained in S1, and recovers the lutein esters, oils, and resinous impurities entrained in the waxy filter cake into the liquid phase, ensuring that the dewaxing liquid phase entering S3 remains a continuous liquid phase with intact component sources. In this step, the system temperature at the end of S1 needs to be maintained, and the filtration or centrifugation method is selected based on the morphology and entrainment state of the waxy solid phase. The waxy filter cake is then washed and recovered using the first organic solvent. Finally, the combined liquid of the primary separation liquid and the washing liquid is defined as the dewaxing liquid. The wax precipitation result formed in S1 is transformed into a feed liquid phase that can be directly used in S3. In practical applications: when the wax in the dispersion system obtained by S1 exists as flocculent or flaky solids, a primary separation liquid phase and a wax filter cake can be obtained by filtration while maintaining the system temperature at the end of S1. The wax filter cake is then washed one to several times at low temperature with the same first organic solvent as S1. The washing liquid is incorporated into the primary separation liquid phase as the dewaxing liquid phase, and this dewaxing liquid phase is directly fed into S3 for the separation of the lutein ester enrichment phase and the oil impurity phase.

[0018] S3. Add the second composite solvent system to the dewaxed liquid phase and perform liquid-liquid mixing and static separation to transfer lutein esters from the dewaxed liquid phase to the lutein ester enriched phase, while oil and resinous impurities remain in the oil impurity phase. The second composite solvent system consists of a third organic solvent and a fourth organic solvent. The third organic solvent is used to increase the solubility of lutein esters in the lutein ester enriched phase, and the fourth organic solvent is used to reduce the amount of oil entrained into the lutein ester enriched phase. In this embodiment, the processing target of S3 is the dewaxed liquid phase obtained in S2. The purpose is to reorganize the lutein esters, oils, and resinous impurities that still coexist in the same liquid phase into two liquid phase pathways with different destinations. This allows the lutein esters to enter the lutein ester-enriched phase required for subsequent saponification, while the oils and resinous impurities remain in the oil impurity phase. This process involves introducing a third organic solvent to create a liquid phase environment in which lutein esters preferentially migrate, then using a fourth organic solvent to compress the dispersion of oils in the lutein ester transfer liquid phase and promote stable stratification. Finally, the entrained lutein esters are recovered through stratification separation and backwashing, ensuring that the material entering S4 has clear boundaries, a stable phase, and a complete source. Since the lutein ester-enriched phase and the oil impurity phase may be located in the upper or lower layer under different solvent combinations, each phase in this embodiment is defined according to component attributes rather than liquid layer position. When entering each specific step, the relative enrichment state of lutein esters, oils, and resinous impurities is used as the identification basis for sampling and detection. The function of S3-1 is to first use a third organic solvent to change the distribution environment of lutein esters in the dewaxing liquid phase, causing lutein esters to preferentially enter the liquid phase associated with the third organic solvent, while oily and resinous impurities remain in the original liquid phase, thus forming a two-liquid-phase system that can be further separated later. The input material is the dewaxing liquid phase obtained from S2. This dewaxing liquid phase is kept in the same liquid phase state as at the end of S2 before entering this step. If a small amount of new wax precipitates after standing, the new solids are separated before entering this step, without raising the temperature above the wax redissolution temperature, to avoid bringing the precipitated wax back into the liquid-liquid distribution process. The third organic solvent is mixed with the original liquid phase of the dewaxing liquid phase. The selection of acetone, ethyl acetate, isopropanol, and ethanol is based on the principle of prioritizing the entry of lutein esters into the transfer liquid phase after addition. When the proportion of the first organic solvent in the dewaxing liquid phase is high and the oil content is high, acetone or ethyl acetate is preferred to improve the carrying capacity of lutein esters in the transfer liquid phase. When an aqueous fourth organic solvent is to be used subsequently, isopropanol or ethanol is preferred to improve the stability of the subsequent two-phase recombination. The third organic solvent is added to the dewaxing liquid phase in stages, with a first liquid-liquid mixing performed after each addition. Mechanical stirring is preferred for mixing. The stirring intensity is controlled to ensure that the container forms an overall circulation without forming a continuous foam layer on the liquid surface. The determination of the state after adding a third organic solvent includes two aspects: First, no waxy solids precipitate in the system, that is, no new flaky, flocculent, or granular waxy solids are added to the liquid phase after stirring is stopped; second, the formed lutein ester transfer liquid phase remains in a fluid state, that is, the system can reform a mobile liquid layer after stirring is stopped, without the formation of non-flowing micelles, a monolithic gel layer, or a large-area static layer attached to the wall. After reaching the above state, samples are taken from two different locations for testing. The phase with a higher lutein ester content is defined as the lutein ester transfer liquid phase, and the other phase is relatively rich in oily and resinous impurities. Defined as the initial oily impurity phase; if wax re-precipitates after the addition of the third organic solvent, it indicates that the third organic solvent was added too quickly or the proportion of the first organic solvent in the system was excessively weakened. In this case, stop adding the third organic solvent, maintain stirring and add a small amount of the first organic solvent to stop the precipitation of the newly added wax, and then resume the phased addition of the third organic solvent; if the system does not precipitate wax after addition but becomes thickened as a whole and cannot reform a mobile liquid layer, reduce the amount added at one time and extend the mixing time each time until a lutein ester transfer liquid phase that neither precipitates wax nor remains in a mobile state is obtained; The function of S3-2 is to adjust the miscibility and component dispersion of the two phases, based on the lutein ester transfer liquid phase and the initial oil impurity phase formed in S3-1, using a fourth organic solvent. This reduces the entrainment of oil in the lutein ester transfer liquid phase and promotes a separable interface, thereby obtaining the desired layered mixing system. The input state is the two-liquid phase system obtained in S3-1, and the fourth organic solvent selected according to a predetermined path. The fourth organic solvent is selected from water, an aqueous solution of ethanol with a mass fraction of 5% to 30%, or an aqueous solution of isopropanol with a mass fraction of 5% to 30%. The selection rules are as follows: When the third organic solvent is acetone or ethyl acetate, and there is still significant miscibility between the two liquid phases after S3-1, water is preferred as the fourth organic solvent; when the third organic solvent is isopropanol or ethanol, and a thick intermediate layer is easily formed at the interface after water is added directly, the corresponding aqueous ethanol solution or aqueous isopropanol solution is preferred, and the layering is promoted by gradually increasing the water content. The fourth organic solvent is added after the third organic solvent has been added and the first liquid-liquid mixing is completed. It is not added simultaneously with the third organic solvent to avoid premature stratification before the system has formed a preferential migration state for lutein esters. The fourth organic solvent is also added in stages, followed by a second liquid-liquid mixing. After each addition, the mixture is first stirred, then allowed to stand briefly to observe interface changes. The control objective of the second liquid-liquid mixing is not simply to achieve rapid stratification, but to ensure that the fourth organic solvent preferentially enters the initial oily impurity phase and reduces the dispersion of oils in the lutein ester transfer liquid phase. At the end of this step, the following executable criteria should be met: after stirring is stopped and the system is allowed to stand, two identifiable liquid layers are formed, and the interface position no longer moves continuously during continued standing; simultaneously, the intermediate layer no longer thickens, and the interface position remains stable. When testing the sample solutions above and below the interface, lutein esters were mainly enriched in one phase, while oils were mainly enriched in the other, indicating the formation of a stratified mixture. If a stable interface could not be formed after adding the fourth organic solvent, and instead continuous emulsification or expansion of the intermediate layer occurred, the fourth organic solvent was added again according to the originally selected type, and the mixture was repeatedly mixed and allowed to stand. If the interlayer still did not converge after adding the fourth organic solvent, the third organic solvent was checked first for excessive addition. After restoring the continuity of the initial oil impurity phase by adding a small amount of the first organic solvent, the fourth organic solvent was added again in portions. If the fourth organic solvent was added too quickly, causing local abrupt stratification and carrying a large amount of oil into the lutein ester transfer phase, the amount added at one time was reduced and the standing time was extended each time until the interface was stable. The function of S3-3 is to separate the stratified mixing system into a lutein ester enriched phase for the next step and an oily impurity phase to be discharged. Lutein esters entrained in the oily impurity phase are recovered through a third organic solvent wash, ensuring that the feed liquid phase of S4 maintains lutein ester enrichment while minimizing the loss of target components with the oily impurity phase. The input state is the stratified mixing system obtained from S3-2. After the system is allowed to stand until the interface between the two liquid layers no longer changes, stratification is performed. Separation methods preferably include liquid separation, siphoning, or bottom valve discharge, with sampling locations avoiding the interface layer. After separation, samples are taken from both phases for testing. The phase with higher lutein ester content is defined as the lutein ester enriched phase, and the phase with higher oily and resinous impurity content is defined as the oily impurity phase. This definition is not subject to change. The upper or lower layer position is restricted; after the initial separation is completed, the oil and impurity phase is backwashed with a third organic solvent. The backwashing method preferably involves adding the third organic solvent in stages, then remixing and allowing it to stand for separation. The control objective of each backwash is to transfer the lutein esters entrained in the oil and impurity phase into the backwash solution, without bringing a large amount of oil back into the backwash solution. After backwashing, the phases are allowed to stand for separation, and the organic backwash solution with a higher lutein ester content is taken and incorporated into the lutein ester enriched phase. The stopping point for continuous backwashing is not limited by a preset number of times, but is determined by the recovery trend of lutein esters in the backwash solution: when the detection result of lutein esters in the subsequent backwash solution is significantly lower than that in the previous backwash solution, the backwashing is stopped. The combined liquid phase is used as the feed liquid phase of S4 and enters the saponification step while maintaining the current liquid phase state. If the interface layer is thick during stratification, collect the interface layer separately first. After standing, incorporate it into the lutein ester enriched phase or the oil impurity phase according to the detection results of lutein ester and oil, respectively, to avoid the interface layer being directly mixed into the S4 feed and increasing the saponification burden. If the oil impurity phase is still obviously yellow to orange-yellow after rewashing and the detection shows that it still contains a lot of lutein ester, continue to add a third organic solvent and repeat the rewashing. If new stratification occurs after the rewash liquid is incorporated into the lutein ester enriched phase, stir briefly to make it homogenized again. If necessary, add a small amount of third organic solvent before sending it into S4. Through the above processing, S3 transforms the coexistence of lutein esters, oils, and resinous impurities in the dewaxed liquid phase obtained in S2 into a two-phase distribution state where they enter the lutein ester enrichment phase and the oil impurity phase respectively according to their subsequent uses. The lutein esters entrained in the oil impurity phase are recovered into the feed liquid phase in S4. In this step, it is necessary to maintain the definition of each phase according to its component properties and avoid using the liquid layer position to replace the component determination. At the same time, a preferential migration environment for lutein esters is established by the third organic solvent, and the fourth organic solvent promotes the reduction of oil entrainment and the formation of interface stability. Then, the loss of target components is reduced by backwashing. Thus, the material boundary entering S4 is clear, the liquid phase composition is stable, and the dependency relationship between the preceding and following steps is closed. In practical applications: when the first organic solvent in the dewaxing liquid phase is n-hexane and the second organic solvent is acetone, acetone can be added to the dewaxing liquid phase in portions and a first liquid-liquid mixture can be performed to allow lutein esters to preferentially enter the lutein ester transfer liquid phase associated with acetone. Then, water or a low-concentration ethanol aqueous solution can be added in portions for a second liquid-liquid mixture to form a lutein ester enriched phase and an oil impurity phase. Subsequently, the oil impurity phase is washed back with acetone, and the wash liquid is incorporated into the lutein ester enriched phase as the feed liquid phase of S4.

[0019] S4. After separating the lutein ester enriched phase, the lutein ester enriched phase is mixed with the alcohol-alkali saponification solution to convert the lutein ester into free lutein. After saponification, a third composite solvent system is added to the saponification solution and allowed to stand for stratification, so that the free lutein is transferred into the lutein product phase, and the fatty acid salts, residual alkali, and polar impurities generated by saponification are transferred into the saponification by-product phase. The third composite solvent system is composed of a fifth organic solvent. After being added to the mixed system after saponification, the fifth organic solvent forms a two-phase stratification with the saponification solution containing alcohol, residual alkali, and fatty acid salts, and is used to transfer the free lutein from the saponification solution into the organic phase. In the implementation of S4, S4 receives the lutein ester enriched phase obtained in S3. The purpose is to first convert the lutein ester into free lutein, and then transfer the free lutein from the saponification system into the lutein product phase used for subsequent washing and desolvation. The fatty acid salts, residual alkali, and polar impurities formed during the saponification process are introduced into the saponification by-product phase. This process includes the stepwise addition of the alcohol-alkali saponification solution and the saponification process, the sampling and determination of the saponification endpoint, and the phase transfer and backwashing using a fifth organic solvent after saponification. The preparation state of the alcohol-alkali saponification solution, the sampling and detection aperture of the sample during the saponification process, the identification method of the lutein product phase and the saponification by-product phase, and the criteria for stopping the backwashing of the saponification by-product phase are all specifically defined in this implementation. This ensures that the lutein product phase output from S4 maintains a clear component assignment and a stable liquid phase state before entering S5. The function of S4-1 is to allow lutein esters to first enter a homogeneous saponification contact state after the lutein ester enriched phase has been formed and the impurity load has been relatively reduced, and then continue to promote the conversion of unconverted lutein esters to free lutein. This avoids the local high alkali concentration, local phase change, or uneven mixing caused by adding all the alcohol-alkali saponification liquid at once. The input materials are the lutein ester enriched phase obtained from S3 and used as the feed liquid phase of S4, and the pre-prepared alcohol-alkali saponification liquid. The alcohol-alkali saponification liquid is a homogeneous liquid formed by pre-dissolving one or two of sodium hydroxide and potassium hydroxide in one or more of methanol, ethanol, and isopropanol. If there are still undissolved solids after preparation, the supernatant should be taken after standing or filtered to remove the undissolved solids before use, so as to ensure that the alcohol-alkali saponification liquid with homogeneous composition enters the saponification step. The lutein ester enriched phase is placed in a reaction vessel equipped with stirring and temperature control capabilities. First, the first portion of the total amount of alcohol-alkali saponification solution is added and stirred. The amount of the first portion of alcohol-alkali saponification solution added is not predetermined in a fixed ratio, but is controlled to transform the original liquid phase of the lutein ester enriched phase into a homogeneous saponification system. That is, after addition and stirring, there are no longer independent lutein ester enriched phase clumps, local high-viscosity phases, or obvious stratification in the system, and the color and flow state of the sample solution are consistent when samples are taken from the upper, middle, and lower parts of the vessel, thus determining that a homogeneous saponification system has been formed. After the homogeneous saponification system is formed, the remaining alcohol-alkali saponification solution is added and saponification continues. The remaining alcohol-alkali saponification solution is used to further convert unconverted lutein esters into free lutein. Stirring is maintained during the continued saponification to keep the reaction system homogeneous and prevent the formation of local alkali enrichment zones. The saponification temperature is controlled within a range that maintains the solvent in the liquid phase, ensures continuous flow of the system, and prevents significant volatilization loss, based on the boiling point of the alcohol solvent in the alkali saponification solution and the stable state of the lutein system. The saponification time is not fixed in advance, but the sampling and testing results of S4-2 are used as the endpoint criterion. If the system shows obvious local turbidity, layering and thickening, or difficulty in forming a homogeneous saponification system after the first part of the alkali saponification solution is added, the stirring time is extended and the subsequent addition rate is reduced. If necessary, a small amount of the same alcohol solvent as the alkali saponification solution is added to restore the system to homogeneity before adding the remaining alkali saponification solution. If continuous adhesion to the wall, overall thickening, or difficulty in stirring occurs during the saponification process, the feeding rate is reduced and the current temperature is maintained to allow the system to return to a stirable and flowable state before continuing saponification. The function of S4-2 is to determine the point at which lutein esters have completed their conversion by continuously judging the composition of lutein esters and free lutein in the saponification system during the saponification process, and to use this point as the basis for stopping saponification and entering the phase inversion step; the input state is the saponification system formed and continuously reacting in S4-1; during the saponification process, samples are taken from the middle of the reaction vessel under stirring, avoiding the liquid surface and the adhesion area on the vessel wall to reduce sampling deviation; after sampling, the sample is pretreated to separate the analyte from the saponification matrix; the pretreatment method is to use the fifth organic solvent. The organic components in the sample are extracted with an agent or an organic solvent compatible with the fifth organic solvent, and the extract is used as the test sample; the detection method is either thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC); when using TLC, the test sample, lutein ester control sample, and free lutein control sample are spotted simultaneously, and the corresponding spot positions and color development are compared under the same developing conditions; when using HPLC, the test sample, lutein ester control sample, and free lutein control sample are detected under the same chromatographic conditions, and the corresponding peaks at retention times are compared; the judgment rule is: When the spots or peaks corresponding to lutein esters no longer appear in the test results, but the spots or peaks corresponding to free lutein still exist, it is determined that lutein esters are no longer detectable. At this point, saponification is stopped, and the mixed system after saponification is completed is obtained. If lutein esters are still detected, stirring is continued and saponification is carried out. Samples are taken again at subsequent time points for testing. The sampling interval is not limited to a fixed number of minutes, but is controlled by the progress of saponification. When the system changes rapidly in the early stage, the sampling interval can be shortened. When the endpoint is approached, the results of two consecutive tests are compared to determine whether residual lutein esters still exist. If the spots in the thin-layer chromatography test are severely tailed or the baseline fluctuates significantly in the high-performance liquid chromatography test, the test sample is re-extracted and purified before testing to avoid misjudgment caused by sample matrix interference. If multiple consecutive samples show that lutein esters have not decreased, the remaining alcohol-alkali saponification liquid in S4-1 is checked first to see if it is completely added and whether the saponification system is kept homogeneous before deciding whether to extend the saponification time. The function of S4-3 is to transfer free lutein from the saponified mixture into the organic phase using the fifth organic solvent after the conversion of lutein esters to free lutein. It also recovers the entrained free lutein to the lutein product phase through backwashing of the saponification byproduct phase, thus providing a feed liquid phase with clearly defined component boundaries for S5. The input materials are the saponified mixture obtained from S4-2 and the fifth organic solvent. The fifth organic solvent is selected from one or more of methyl tert-butyl ether, methyl isobutyl ketone, and heptane, and its selection is based on the addition of... After saponification, the mixed system can form two phases with the saponification liquid containing alcohol, residual alkali and fatty acid salts, and free lutein preferentially enters the organic phase. After adding the fifth organic solvent to the mixed system after saponification, it is mixed and then allowed to stand until the interface between the two liquid layers no longer changes, completing the first standing separation. After separation, samples of the two phases are taken to detect free lutein. The organic phase with higher free lutein content is defined as the lutein product phase, and the other phase is defined as the saponification by-product phase, which mainly contains fatty acid salts, residual alkali and polar impurities. Subsequently, the saponification by-product phase was backwashed using a fifth organic solvent. The backwashing method involved adding the fifth organic solvent to the saponification by-product phase, remixing, and then allowing it to stand for a second time to separate the layers. The organic phase obtained after the second standing separation contained free lutein transferred from the saponification by-product phase. This organic phase was incorporated into the lutein product phase obtained after the first standing separation. The stop point for backwashing was not limited to a fixed number of times, but was determined by the change in the detection rate of free lutein in the backwashed organic phase. When the detection rate of free lutein in the organic phase after the subsequent backwash was significantly lower than that after the previous backwash, the backwashing process was stopped. Stop further washing; if the interface layer is thick after the first settling and separation, collect the interface layer separately and continue to settling. After the interface layer separates again, combine it into the lutein product phase or saponification by-product phase according to the detection results of free lutein and fatty acid salts, to avoid direct introduction into S5; if a stable two phases cannot be formed after the addition of the fifth organic solvent, check whether the alcohol content in the mixed system after saponification is too high. If necessary, add the fifth organic solvent and extend the settling time until stable separation is obtained; the combined lutein product phase is kept in the organic phase state and directly sent to S5 for water washing; Through the above processing, S4 transforms the lutein ester enriched phase obtained in S3 from a liquid phase dominated by ester components into a lutein product phase dominated by free lutein, while retaining fatty acid salts, residual alkali, and polar impurities formed during saponification in the saponification by-product phase. At the same time, the loss of free lutein is reduced by backwashing the saponification by-product phase. In this step, it is necessary to keep the alcohol-alkali saponification liquid added in a homogeneous liquid state, mix it in stages according to the requirements for forming a homogeneous saponification system, use the detection result that lutein esters are no longer detectable as the basis for stopping saponification, and identify the lutein product phase and the saponification by-product phase according to the relative enrichment state of free lutein. In practical applications: When the lutein ester enriched phase is transferred from the acetone system to the saponification step, a homogeneous alcohol-alkali saponification solution formed by ethanol and potassium hydroxide can be prepared first. The first part of the alcohol-alkali saponification solution is added and stirred until the color and flow state of the sample solution are consistent throughout the system. Then, the remaining alcohol-alkali saponification solution is added to continue saponification. During the saponification process, after confirming that lutein esters are no longer detected by thin-layer chromatography or high-performance liquid chromatography, methyl tert-butyl ether or methyl isobutyl ketone is added to the mixed system after saponification. The system is allowed to stand and separate into layers to obtain the lutein product phase and the saponification by-product phase. The organic phase obtained after washing the saponification by-product phase with the fifth organic solvent is incorporated into the lutein product phase. The combined lutein product phase is then sent to S5 for water washing.

[0020] S5. Wash the lutein product phase with water to remove residual alkali and residual saponification byproducts, and retain the washed organic phase. In this specific embodiment, S5 receives the lutein product phase obtained from S4. The purpose of this treatment is to gradually remove residual alkali, fatty acid salts, and polar impurities that can enter the aqueous phase from the lutein product phase, while keeping free lutein in the organic phase. This ensures that the material entering S6 does not carry saponification residues that could affect the stability of desolvation and concentration. To this end, S5 is organized in the order of "contact between organic phase and washing water - settling and stratification - detection of aqueous phase - decision on whether to continue washing". The type of washing water, the determination of stratification after mixing, the detection method of the aqueous phase, and the basis for stopping washing all adopt the standards directly corresponding to the process state, without relying on additional test screening results. In step S5-1, the lutein product phase obtained in step S4 is first placed into a washing container equipped with stirring and settling conditions, and then washing water is added for mixing. Deionized or purified water is used as the washing water to avoid the introduction of exogenous inorganic salts and organic impurities into the system. The order of adding the lutein product phase and washing water is not strictly defined, but it should be based on the premise that two separateable liquid phases can be formed after addition. The mixing method is mechanical stirring or slow circulating mixing, with the mixing intensity controlled so that the two phases are in full contact and no continuously expanding emulsion layer forms after stirring stops. After mixing, the mixture is allowed to stand until the interface between the two liquid layers no longer changes. After separation, the organic phase and aqueous phase are separated, and the separated organic phase is retained... The resulting aqueous phase is used as the feed liquid phase for the next wash. The separated aqueous phase is used to determine the residual alkali and residual saponification byproducts carried out in this wash. The pH of the separated aqueous phase is measured using pH test paper or a pH meter. When using pH test paper, the state of the aqueous phase is determined by the acidic, neutral, and alkaline ranges corresponding to the color development. When using a pH meter, the state of the aqueous phase is determined by the range of the reading. If the interface layer is thick after standing, or if there is a significant interlayer between the organic phase and the aqueous phase, the interlayer is collected separately and allowed to stand for a while until it separates again before being added to the corresponding phase. If a large amount of organic phase is mixed in the aqueous phase and affects the pH measurement, the standing time is extended until the aqueous phase becomes clear before testing. In S5-2, the organic phase obtained from the previous separation is used as the feed liquid phase, and the processes of adding water for mixing, allowing the phase to settle and separate, and detecting the aqueous phase are repeated until the aqueous phase obtained from the most recent separation simultaneously meets both conditions, at which point the water washing is stopped. The first condition is that the aqueous phase obtained from this separation is in a neutral state after pH testing with pH paper or a pH meter. The second condition is that fatty acid salts are no longer detected in the aqueous phase obtained from this separation. The detection of fatty acid salts is performed using an acidification observation method, i.e., a portion of the aqueous phase obtained from this separation is taken and an acidification solution is added, which can be an aqueous solution of hydrochloric acid or sulfuric acid. If visible oil droplets, flocculent matter, or precipitate still precipitate in the aqueous phase after addition, it is determined that fatty acid salts are still detected in the aqueous phase obtained from this separation, and the next water washing is performed. If the aqueous phase remains clear after addition and no new oil droplets or flocculent matter appear, the process continues. If precipitation occurs, it is determined that fatty acid salts are no longer detectable in the aqueous phase obtained from this separation. When the aqueous phase obtained from the most recent separation meets both the conditions of neutrality and no further detection of fatty acid salts, the organic phase obtained from the separation corresponding to this aqueous phase is defined as the washed organic phase and is directly sent to S6. If the aqueous phase is close to neutral during continuous washing but fatty acids still precipitate after acidification, it indicates that there are still residual saponification byproducts in the organic phase entering the aqueous phase, and washing should continue. If fatty acids no longer precipitate after acidification, but the aqueous phase is still alkaline, it indicates that there are still residual alkalis in the organic phase, and washing should continue. If the pH change of the aqueous phase is not obvious after multiple consecutive washings, priority should be given to checking whether the lutein product phase contains saponification byproducts, and if necessary, the organic phase should be allowed to stand again to separate into layers, the bottom entrainment should be removed, and then washing should continue. After the above processing, the organic phase output from S5 after washing is the organic phase obtained after removing residual alkali and residual saponification by-products in the continuous water washing process. Its destination is clear and it is connected with the desolvation and concentration requirements of S6. The key control points of this process are: the washing water is always deionized water or purified water; the interface stability is used as the basis for stratification after each mixing; the organic phase obtained from each separation is retained in sequence and used as the feed liquid phase for the next water washing; when the water washing is stopped, the neutral state of the aqueous phase obtained from the most recent separation and the detection results of fatty acid salts are examined at the same time, so as to avoid judging the end of washing based on a single phenomenon. In practical applications: When the lutein product phase obtained in S4 is an organic phase containing methyl tert-butyl ether, deionized water can be added to the lutein product phase and stirred slowly. After standing and separating the layers, the aqueous phase is separated. First, the pH of the aqueous phase is measured. Then, a portion of the aqueous phase is added to hydrochloric acid solution to observe whether fatty acids precipitate. If the aqueous phase is still alkaline or fatty acids precipitate after acidification, the separated organic phase is used as the feed liquid phase for the next water wash and the process is repeated until the most recent aqueous phase is neutral and no fatty acids precipitate after acidification. Then, the organic phase corresponding to the aqueous phase is sent to S6 as the washed organic phase.

[0021] S6. The washed organic phase is desolvated and concentrated to remove the organic solvent and obtain lutein extract; In this specific embodiment, S6 receives the washed organic phase obtained in S5. The purpose of this treatment is to first continuously remove the organic solvent from the lutein system, and then further reduce the residual organic solvent while keeping the lutein in a flowable and concentrated state, until the lutein extract is discharged. This process is divided into two interconnected stages: the first stage is mainly characterized by continuous distillation of organic solvent, where the washed organic phase is subjected to desolventizing under reduced pressure and the distilled organic solvent is collected; the second stage continues to concentrate under reduced pressure after continuous distillation, so that the residual organic solvent in the concentrate continues to decrease and finally forms the lutein extract. Since the organic solvent used in the preceding steps of this application may be one or more of n-hexane, heptane, cyclohexane, petroleum ether, acetone, ethyl acetate, isopropanol, ethanol, methyl tert-butyl ether, methyl isobutyl ketone, and heptane, this step does not use a single boiling point as the control basis, but rather uses the liquid phase flow state, the distillate outflow state, and the organic solvent content in a unit sample as the basis for judgment and operation. In S6-1, the washed organic phase obtained in S5 is first sent to a desolventizing device equipped with depressurization, heating, and stirring functions for desolventization under reduced pressure. The purpose is to continuously remove the organic solvent that can be continuously distilled from the washed organic phase without causing local overheating, carbonization of the wall, or overall loss of flow in the lutein system, and to form a concentrated liquid that can be further concentrated. The input material is the washed organic phase. Before entering the desolventizing device, if there is still a small amount of water phase entrained at the bottom of the washed organic phase after standing, the entrained water phase is separated first before entering the desolventizing device to avoid sudden boiling or phase fluctuations caused by water entrainment during the desolventizing process. During desolventizing under reduced pressure, stirring is started first, and then the pressure inside the device is gradually reduced while the temperature of the jacket or heating surface is raised simultaneously, so that the organic solvent in the organic phase begins to vaporize and is collected as distilled organic solvent by condensation. The pressure and temperature settings are not preset with fixed values, but rather controlled by the principle that "the organic solvent can continuously vaporize and form a continuous distillate, and the concentrate maintains overall flow without forming a large-area stagnant layer adhering to the wall." "The concentrate maintains a flowing state" means that during the solvent removal process, the stirrer can continuously drive the liquid surface and the entire liquid to circulate, preventing the formation of a continuous, immobile, highly adhesive wall layer on the container wall, and ensuring that the concentrate flows out of the sampling port without forming a stagnant block during sampling. "Continuous distillate outflow" means that organic fractions can be continuously collected at the condenser end, rather than being interrupted immediately after a short drip. Desolvation is continuously performed during the continuous distillate outflow without switching to the final concentration state midway. As the solvent removal process progresses... Proceed to collect the distilled organic solvent and retain the concentrate after solvent removal. The collected distilled organic solvent can be stored separately according to the aforementioned solvent reuse rules and reused in the corresponding steps S1, S3, or S4 when the purity meets the requirements. If obvious boiling, rapid liquid surface rise, or foam entering the condensation system occurs at the beginning of decompression, it indicates that the pressure reduction is too fast or the heating is too strong. The pressure should be adjusted back or the heating intensity reduced first, and the decompression should continue after the liquid surface returns to stability. If local wall thickening, significant increase in stirring load, or overall weakening of circulation occurs in the concentrate during the solvent removal process, it indicates that the viscosity of the concentrate has increased. The solvent removal rate should be reduced first and stirring should be maintained to restore the system to a flowable state before continuing the operation. In S6-2, after the concentrate obtained in S6-1 no longer continuously flows out of distillate, the concentrate is further concentrated under reduced pressure. The purpose is to further reduce the residual organic solvent content based on the main solvent removal completed in the previous stage, and to stop concentration and discharge the product when the lutein extract's finished product control indicators are met. The input state is the concentrate obtained in S6-1. "No longer continuously flowing out of distillate" means that under the current pressure, temperature, and stirring conditions, only intermittent small drops appear at the condenser end, or there is no continuous distillate flow for a long time. At this point, the operation is no longer organized according to the main solvent removal stage, and the process transitions to the final concentration stage. In the final concentration stage, reduced pressure and stirring are maintained, and the pressure and heating intensity are adjusted according to changes in the concentrate's viscosity to ensure that the concentrate is always in a state that can be driven by the stirrer, while avoiding localized overheating due to over-concentration. Increased concentration can cause lutein to darken abnormally or adhere to the cell walls; during concentration, samples are taken per unit volume to test for organic solvent content; the same mass or volume of concentrate can be used per unit volume to ensure comparability of test results; the organic solvent content can be detected by gas chromatography or other methods suitable for residual organic solvent detection, and the control index for the finished lutein extract is the residual organic solvent control standard implemented when the finished product is released in this application; when the organic solvent content in the unit sample is lower than the control index for the finished lutein extract, the vacuum concentration is stopped and the product is discharged to obtain lutein extract; if the test results show that the organic solvent content in the unit sample is still higher than the control index for the finished product, the vacuum concentration is continued at the current or slightly lower pressure and samples are taken again for testing until the discharge conditions are met; If the concentrate is close to losing flow and the agitator is difficult to continuously drive during the final concentration process, but the test results still do not meet the finished product control indicators, then the heating intensity should be reduced and the holding time under the current reduced pressure should be extended to allow the residual organic solvent to continue to slowly move out, rather than using a sudden heating method to force concentration, so as to avoid local thermal instability of the lutein extract; when discharging, the material should be discharged in a warm and still flowable state to avoid difficulties in discharging or increased residue on the container wall due to increased viscosity after complete cooling; After the above processing, S6 gradually transforms the washed organic phase obtained in S5 from a mobile liquid phase containing a large amount of organic solvent into lutein extract with an organic solvent content that meets the finished product control requirements. Simultaneously, the collection of distilled organic solvent and the determination of the concentration endpoint are completed. This step requires continuous monitoring of three states: first, whether there is still continuous distillate flowing from the condenser during desolventizing; second, whether the concentrate remains flowable throughout the entire desolventizing and concentration process; and third, whether the organic solvent content per unit sample after final concentration is lower than the finished lutein extract control index. Only when these three states are satisfied in sequence can the lutein obtained from the discharge be successfully processed. Only then can the extract form a complete connection with the aforementioned steps; in practical applications: when the organic phase obtained after washing in S5 is an organic phase containing methyl tert-butyl ether and a small amount of residual ethanol, the organic phase can be first sent to a vacuum evaporator with stirring, the pressure is gradually reduced and the temperature is raised to the condenser end to continuously collect the distillate, while keeping the concentrate constantly driven by the stirrer; when there is no more distillate flowing out from the condenser end, continue to maintain the vacuum and stirring for final concentration, and test the residual organic solvent in the concentrate according to a uniform sampling amount until the test result is lower than the finished product control index of this batch of lutein extract, then stop the concentration and discharge the material to obtain lutein extract.

[0022] Working principle: This scheme revolves around the fate and processing sequence of various accompanying components during the preparation of lutein extract. First, the crude extract containing lutein esters is mixed with a first composite solvent system, allowing lutein esters, oils, and resinous impurities to enter the liquid phase. Then, the wax is precipitated and separated by cooling, resulting in a dewaxed liquid phase. Subsequently, a second composite solvent system is added to the dewaxed liquid phase, causing lutein esters to transfer to the lutein ester-rich phase, while oils and resinous impurities remain in the oil impurity phase. This process first completes the separation of lutein esters from the main phytochemicals. The process involves separating water impurities; then saponifying the lutein ester enriched phase to convert the lutein ester into free lutein, and transferring the free lutein into the lutein product phase using a fifth organic solvent, while fatty acid salts, residual alkali, and polar impurities enter the saponification by-product phase; finally, the lutein product phase is washed, desolventized, and concentrated to obtain lutein extract; the entire process is organized with the logic of reducing the processing burden of the next step by the previous step, so that waxes, oils, resinous impurities, saponification by-products, and target components are separated step by step; In scenarios where marigold extract continuously enters the purification production line, the crude extract typically contains lutein esters, oils, waxes, and resinous impurities. Directly saponifying and concentrating this mixture can easily lead to slow stratification, increased entrainment, heavier washing burden, and significant fluctuations in the final product. The practical application of this solution involves first removing the waxes from the liquid phase in the initial stage, then transferring the lutein esters from the liquid phase containing more oils and resinous impurities. Afterward, only the lutein ester-enriched phase is saponified, and the resulting free lutein is transferred separately into the lutein product phase. Finally, water washing and solvent removal are completed. This approach ensures a clearer composition of materials entering subsequent processes, and the saponification, washing, and concentration processes deal with a more homogeneous system, which helps maintain the continuity of the entire process and the stability of the lutein extract preparation process.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for extracting and purifying lutein extract based on a composite solvent system, characterized in that, include: S1. The crude extract containing lutein esters from marigolds is mixed with a first composite solvent system, so that the lutein esters, oils, and resinous impurities in the crude extract enter the liquid phase, and the wax is precipitated by lowering the system temperature, resulting in a dispersion system containing the precipitated wax; wherein, the first composite solvent system consists of a first organic solvent and a second organic solvent, the first organic solvent is used to dissolve the oils, and the second organic solvent is used to reduce the viscosity of the system containing the crude extract containing lutein esters and keep the lutein esters dispersed in the liquid phase. S2. The dispersion system is subjected to solid-liquid separation to separate the waxy solid phase and retain the dewaxed liquid phase after the wax is removed. The dewaxed liquid phase contains lutein esters, oils and resinous impurities, and the waxy solid phase is the waxy component that has been removed from the crude extract containing lutein esters. S3. Add the second composite solvent system to the dewaxed liquid phase and perform liquid-liquid mixing and static separation to transfer lutein esters from the dewaxed liquid phase to the lutein ester enriched phase, while oil and resinous impurities remain in the oil impurity phase. The second composite solvent system consists of a third organic solvent and a fourth organic solvent. The third organic solvent is used to increase the solubility of lutein esters in the lutein ester enriched phase, and the fourth organic solvent is used to reduce the amount of oil entrained into the lutein ester enriched phase. S4. After separating the lutein ester enriched phase, the lutein ester enriched phase is mixed with the alcohol-alkali saponification solution to convert the lutein ester into free lutein. After saponification, a third composite solvent system is added to the saponification solution and allowed to stand for stratification, so that the free lutein is transferred into the lutein product phase, and the fatty acid salts, residual alkali, and polar impurities generated by saponification are transferred into the saponification by-product phase. The third composite solvent system is composed of a fifth organic solvent. After being added to the mixed system after saponification, the fifth organic solvent forms a two-phase stratification with the saponification solution containing alcohol, residual alkali, and fatty acid salts, and is used to transfer the free lutein from the saponification solution into the organic phase. S5. Wash the lutein product phase with water to remove residual alkali and residual saponification byproducts, and retain the washed organic phase. S6. The washed organic phase is desolvated and concentrated to remove the organic solvent and obtain lutein extract.

2. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 1, characterized in that: S1 includes the following steps: S1-1. Select a first organic solvent that has a dissolving effect on the oil in the crude extract containing lutein ester as the first component in the first composite solvent system. The first organic solvent is one or more of n-hexane, heptane, cyclohexane, and petroleum ether. First, add the first organic solvent to the crude extract containing lutein ester and mix it, so that the oil in the crude extract containing lutein ester enters the liquid phase mainly composed of the first organic solvent, and the resinous impurities are dispersed in the liquid phase along with the oil. S1-2. Add a second organic solvent to the liquid phase obtained in S1-1 as the second component in the first composite solvent system. The second organic solvent is selected from those that are miscible with the first organic solvent and have a viscosity-reducing effect on the crude extract containing lutein esters, and keep the lutein esters in the liquid phase. The second organic solvent is one or more of acetone, ethyl acetate, isopropanol, and ethanol. After adding the second organic solvent, continue mixing until there are no more undispersed agglomerates in the crude extract containing lutein esters, and obtain the mixture before the wax precipitation. S1-3. Cool the mixture obtained in S1-2 before the wax precipitates until solid wax precipitates in the system and continue stirring to allow the wax to precipitate from the liquid phase, while lutein esters, oils and resinous impurities remain in the unprecipitated liquid phase, thus obtaining a dispersion system containing precipitated wax.

3. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 2, characterized in that: S2 includes the following steps: S2-1. The dispersion system is fed into the solid-liquid separation process at the system temperature at the end of S1. The liquid phase and solid phase are separated by filtration or centrifugation to obtain a primary separated liquid phase and a waxy filter cake. The primary separated liquid phase serves as the main liquid phase of the dewaxing liquid phase, and the waxy filter cake is a solid phase containing waxy components and entrained liquid phase. S2-2. The wax filter cake is washed with a first organic solvent, so that the lutein esters, oils and resinous impurities entrained in the wax filter cake enter the washing liquid, and the washing liquid is incorporated into the first separation liquid phase to obtain a dewaxed liquid phase. The wax filter cake forms a wax solid phase after washing. The wax solid phase is the wax component that no longer enters the liquid phase in the first composite solvent system and at the system temperature at the end of S1. S2-3. Define the combined liquid of the primary separation liquid and the washing liquid as the dewaxing liquid phase, and use the dewaxing liquid phase as the feed liquid phase of S3.

4. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 3, characterized in that: S3 includes the following steps: S3-1. First, add a third organic solvent to the dewaxed liquid phase and perform the first liquid-liquid mixing. This allows the lutein esters in the dewaxed liquid phase to form a lutein ester transfer liquid phase along with the third organic solvent, while the oil and resinous impurities in the dewaxed liquid phase remain in the original liquid phase to form the initial oil impurity phase. The third organic solvent can be one or more of acetone, ethyl acetate, isopropanol, and ethanol. After the third organic solvent is added, no waxy solids will precipitate in the system, and the lutein ester transfer liquid phase will remain in a fluid state. S3-2. Add a fourth organic solvent to the system obtained in S3-1 and perform a second liquid-liquid mixing. This allows the fourth organic solvent to enter the initial oil and impurity phase and reduce the dispersion of oil and impurities in the lutein ester transfer liquid phase. At the same time, it forms a clear stratification interface between the lutein ester transfer liquid phase and the initial oil and impurity phase, resulting in a stratified mixing system. The fourth organic solvent is selected from water, an aqueous solution of ethanol with a mass fraction of 5% to 30%, or an aqueous solution of isopropanol with a mass fraction of 5% to 30%. The fourth organic solvent is added after the third organic solvent is added and the first liquid-liquid mixing is completed.

5. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 4, characterized in that: S3 further includes the following steps: S3-3. After the mixture to be separated is allowed to stand and separate into layers, the lutein ester enriched phase and the oil impurity phase are separated. The separated oil impurity phase is then washed with a third organic solvent so that the lutein esters entrained in the oil impurity phase enter the washing solution. The wash liquid was incorporated into the lutein ester enrichment phase and used as the feed liquid phase for S4.

6. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 5, characterized in that: S4 includes the following steps: S4-1. The lutein ester enriched phase and the alcohol-alkali saponification solution are mixed in two parts. First, the first part of the total amount of alcohol-alkali saponification solution is added and stirred to form a homogeneous saponification system. Then, the remaining alcohol-alkali saponification solution is added to continue saponification. The alcohol-alkali saponification solution is prepared by one or more of methanol, ethanol, and isopropanol and one or two of sodium hydroxide and potassium hydroxide. The first part of the alcohol-alkali saponification solution is used to expand the lutein ester enriched phase and enter the saponification contact state. The remaining alcohol-alkali saponification solution is used to further convert the unconverted lutein ester into free lutein. S4-2. During the saponification process, the saponification system is sampled and the composition of lutein esters and free lutein is determined. When lutein esters are no longer detected in the sampling results, saponification is stopped and the mixed system after saponification is obtained. The sampling and determination are performed using either thin-layer chromatography or high-performance liquid chromatography.

7. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 6, characterized in that: S4 further includes the following steps: S4-3. Add the fifth organic solvent to the mixture after saponification and allow it to stand for the first time to separate the lutein product phase and the saponification by-product phase. Then, use the fifth organic solvent to wash the saponification by-product phase and allow it to stand for the second time to separate the phase. Incorporate the organic phase obtained from the second standing separation into the lutein product phase obtained from the first standing separation. The fifth organic solvent is selected from one or more of methyl tert-butyl ether, methyl isobutyl ketone, and heptane.

8. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 7, characterized in that: S5 includes the following steps: S5-1. After mixing the lutein product phase with the washing water, let it stand to separate the organic phase and the aqueous phase. Take the separated aqueous phase to determine its pH value, and use the separated organic phase as the feed liquid phase for the next water wash. The washing water used in each water wash is deionized water or purified water. S5-2. Repeat S5-1 until the pH of the aqueous phase obtained from the most recent separation is neutral and fatty acid salts are no longer detected in the aqueous phase obtained from this separation. Then, retain the corresponding organic phase as the washed organic phase.

9. The method for extracting and purifying lutein extract based on a composite solvent system according to claim 8, characterized in that: S6 includes the following steps: S6-1. The washed organic phase is subjected to desolventization under reduced pressure, the distilled organic solvent is collected and the concentrated liquid after desolventization is retained. During the desolventization process, the concentrated liquid is kept in a flowing state and desolventization is continued during the continuous outflow of the distillate. S6-2. After no more distillate flows out of the concentrate obtained in S6-1, continue to concentrate the concentrate under reduced pressure until the organic solvent content in a unit sample is lower than the control index of the finished lutein extract. Stop the concentration and discharge the product to obtain lutein extract.

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