Method for preparing lutein ester crystal

Abstract

The invention discloses a method for preparing lutein ester crystals, which belongs to the technical field of extract processing, and comprises the following steps: (1) adding a mixed solvent of inorganic base, alkane and fatty alcohol into lutein extract, and heating to carry out impurity fatty acid ester saponification reaction; (2) after saponification of the impurity fatty acid ester, carrying out solid-liquid separation to separate out a solvent layer so as to obtain an extract layer; (3) adding a mixed solvent into the extract layer, dissolving, stirring, cooling and crystallizing; and (4) after the crystallization is finished, filtering, washing and drying to obtain lutein ester crystals. According to the method for preparing the lutein ester crystal, the content and yield of the lutein ester crystal prepared by lutein extract crystallization can be effectively improved, the yield of the lutein extract with relatively low lutein ester content is particularly obviously improved, and the content of the prepared lutein ester crystal meets food-grade requirements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of extract processing, and particularly relates to a method for preparing lutein ester crystals from lutein extract crystals. BACKGROUND

[0002] Lutein is an oxygen-containing carotenoid, which is widely present in plants such as pumpkins, spinach, cabbage and marigold flowers. The content of lutein in marigold flowers is the highest. Recent researches show that the stability of free lutein in vitro is poor, and the free lutein is easily oxidized and degraded. The stability of lutein ester is obviously better than that of free lutein. It is also found that lutein ester is more easily absorbed by human bodies, and the lutein ester can be converted into free lutein in human bodies. The free lutein has the effects of antioxidation, elimination of free radicals, anticancer and reduction of the incidence of cardiovascular diseases.

[0003] In marigold flowers and other plants, the content of free lutein is low, and most of the lutein is modified by lauric acid, myristic acid and palmitic acid. The content of lutein palmitate, which is the highest among the lutein esters, is low. However, the total content of lutein esters in marigold extract is only 16-33%, and most of the rest is gum, fatty acid and polysaccharide, which greatly limits the yield of lutein ester crystallization and purification.

[0004] The content of lutein ester in lutein extract is closely related to the environmental temperature, growth cycle and harvesting node during the growth of marigold flowers. The unit content of lutein extract prepared from different marigold flowers is obviously different. The content yield of lutein ester crystals prepared from lutein extract with a relatively low content of lutein ester is lower.

[0005] Therefore, it is urgent to find a method for improving the content yield of lutein ester crystals, especially for lutein extract with a relatively low content of lutein ester.

[0006] Chinese patent CN201010557485.6 discloses an industrial method for preparing high-purity lutein ester from lutein oleoresin, dissolving lutein oleoresin in acetone solvent, filtering under pressure at different temperatures by cooling, and washing and drying to obtain lutein ester crystals. However, the process takes a long time, uses lutein extract with a lutein ester content of 40%, and the crystal content yield is about 65%, which is relatively low. Chinese patent CN200610026613.8 discloses a method for separating and purifying high-content lutein fatty acid ester from marigold oleoresin, dissolving marigold oleoresin in a mixed solvent of low-molecular alcohol and n-hexane, and then performing cooling crystallization, filtering, and then using n-hexane to perform temperature rising dissolution, cooling crystallization, filtering, washing, and drying to obtain lutein ester. The process uses temperature rising dissolution and cooling crystallization twice, the raw material lutein ester content is 22.7%-31.8%, the obtained lutein ester content is >80%, and the lutein ester content yield is between 68-71%, which still needs to be improved.

[0007] The above methods all use temperature rising dissolution and cooling crystallization process to prepare lutein ester crystals from lutein extract as raw material. Different methods use single solvent or mixed solvent to recrystallize lutein ester with different solvents and solvent ratios in order to improve the unit content and yield of lutein ester, but the above methods still cannot obtain ideal results in purity and yield. SUMMARY

[0008] The purpose of the present application is to provide a method for preparing lutein ester crystals from lutein extract crystallization, which provides a method for effectively improving the lutein ester crystallization content yield for raw materials with low lutein ester content.

[0009] A method for preparing lutein ester crystals, comprising the following steps:

[0010] Step S1, adding a mixed solvent of inorganic base, alkane and fatty alcohol to lutein extract, and performing impurity fatty acid ester saponification reaction by temperature rising;

[0011] Step S2, after the impurity fatty acid ester saponification is completed, performing solid-liquid separation to separate out the solvent layer and obtain the extract layer;

[0012] Step S3, adding an organic mixed solvent to the extract layer to dissolve and stir, and then cooling crystallization;

[0013] Step S4, filtering, washing, and drying after the crystallization is completed to obtain lutein ester crystals.

[0014] Further improvement of the technical scheme of the present application is that the inorganic base in step S1 is one of potassium hydroxide and sodium hydroxide, the alkane is one of n-hexane, cyclohexane, and n-pentane, and the fatty alcohol is one of methanol, ethanol, and isopropyl alcohol.

[0015] Further improvement of the technical scheme of the present application is that the amount of inorganic base in step S1 is 2%-6% of the weight of lutein extract; the weight-volume ratio kg / L of lutein extract to alkane is 1:1-3; the weight-volume ratio kg / L of lutein extract to fatty alcohol is 1:3-5; the fatty alcohol is 85%-95% methanol, isopropyl alcohol or ethanol aqueous solution.

[0016] Further improvement of the technical scheme of the present application is that the saponification reaction temperature in step S1 is 50-60℃, and the saponification time is 0.5-1h.

[0017] Further improvement of the technical scheme of the present application is that the mixed solvent in step S3 includes n-hexane and low-molecular alcohol containing 1-4 carbon atoms, and the low-molecular alcohol includes one or more of methanol, ethanol or isopropyl alcohol.

[0018] Further improvement of the technical scheme of the present application is that the volume ratio of n-hexane to low-molecular alcohol in the mixed solvent in step S3 is 1:2.5-4.

[0019] Further improvement of the technical scheme of the present application is that the mass-volume ratio kg / L of lutein extract in step S1 to the mixed solvent in step S3 is 1:10-16.

[0020] Further improvement of the technical scheme of the present application is that in step S3, the initial temperature of the cooling crystallization is 25-30℃, the temperature is lowered to 5-10℃ at a rate of 3-5℃ / h, and the temperature is kept for 2-3h.

[0021] Since lutein ester and other impurity fatty acid ester exist in lutein extract, and the properties of lutein ester and impurity fatty acid ester are close, it is a contradictory problem to improve the yield and consider the unit content of lutein ester in the crystallization process. Simply improving the crystallization weight yield will cause lutein ester and impurity fatty acid ester to be precipitated at the same time, the unit content of lutein ester crystal is not high, the obtained product is sticky and not loose, and even becomes sticky paste, which affects the subsequent application. And improving the unit content of lutein ester often needs multiple crystallization or relatively loose crystallization conditions, but this means that more lutein ester will remain in the system, and the crystallization weight yield is not high.

[0022] And since the properties of lutein ester and other fatty acid esters in the extract are very close, considering the principle of similar dissolves similar, the two types of substances are combined more closely, therefore, for lutein extract with relatively low lutein ester content, the content yield of lutein ester prepared by crystallization is lower than that of normal or high content lutein extract raw material.

[0023] In order to improve the content yield of lutein ester crystals prepared by crystallization of low-content lutein extract, the application constructs a specific mixed solvent system of inorganic alkali, alkane and fatty alcohol, so that the impurity fatty acid ester in the lutein extract is pre-saponified in the system and at a set temperature to generate fatty acid salt; in the construction of the saponification system of the impurity fatty acid ester, a certain proportion of n-hexane is added, which not only can increase the dissolution effect of the system compared with the traditional alkali-alcohol system, but also is beneficial to the separation of lutein ester and the impurity fatty acid ester, so that the saponification reaction of the impurity fatty acid ester is more rapid and complete.

[0024] Through the conditions set in the patent, the impurity fatty acid ester in the lutein extract is saponified, and the lutein ester does not participate in the reaction, and through solid-liquid separation, the part of the impurity fatty acid is removed, which not only improves the content of lutein ester in the raw material before crystallization of the lutein extract, but also removes the impurity fatty acid ester similar to the lutein ester, which is beneficial to the next step of crystallization.

[0025] Meanwhile, the application constructs a lutein ester cooling crystallization curve, optimizes the types and proportions of the lutein extract and the mixed solvent, and parameters such as the final crystallization temperature, so as to further improve the crystallization yield of lutein ester, and finally obtain lutein ester crystals with content that meets the food grade requirements and improved content yield.

[0026] The method of the application can improve the content yield of lutein ester crystals prepared from low-content lutein extract, and also considers the purity of lutein ester crystals, and the process is simple and beneficial to industrial application. DETAILED DESCRIPTION

[0027] The preferred embodiments of the application will be described in detail below with reference to the examples. It should be understood that the following examples are given only for the purpose of illustration and are not intended to limit the scope of the application. Those skilled in the art can make various modifications and replacements to the application without departing from the spirit and principles of the application.

[0028] In the following examples, the experimental methods are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained commercially or prepared according to conventional methods in the art unless otherwise specified.

[0029] In the application, the lutein extract refers to an oil extract rich in lutein ester obtained by extracting and concentrating marigold flowers or marigold flower granules as raw materials, which can be obtained commercially or prepared by methods known in the art. The preparation method is as follows: marigold flowers are dried and granulated, and n-hexane solvent is used for extraction, and the extract is concentrated to prepare lutein extract.

[0030] The total lutein ester content in lutein extract is generally 20%-34%, and the total lutein ester content in most lutein extracts is between 27% and 31%. The low-content lutein extract described in the patent has a total lutein ester content of 20%-27%.

[0031] In the present application, the total lutein ester refers to lutein monoester, lutein diester and zeaxanthin ester, specifically including lutein myristate, lutein palmitate monoester, lutein stearate monoester, lutein laurate-myristate, lutein myristate diester, lutein palmitate diester, lutein stearate diester, etc.

[0032] In industrial production, in order to facilitate operation, the lutein oleoresin (extract) can be first melted in a water bath dissolution tank and then transferred to a crystallization tank using vacuum negative pressure extraction, the temperature of the water bath is 65-70℃, and the time is 36-48 hours. The viscosity of the melted product is 5000-8000 mPa·s (test temperature is 65℃) to facilitate extraction.

[0033] In the present application, the total lutein ester content is tested by ultraviolet detection method, specifically: after the sample is dissolved in n-hexane, it is diluted to constant volume, the absorbance at a wavelength of 445 nm is detected, and the total lutein ester content in the sample is calculated according to the formula:

[0034]

[0035] In the formula: X-the content of total ester in the sample, %;

[0036] A-the actual absorbance of the sample solution;

[0037] K-the dilution multiple of the sample;

[0038] m-the mass of the sample, g;

[0039] 1394-the mass absorption coefficient of lutein ester at 445 nm.

[0040] The detection result is kept to two decimal places.

[0041] Example 1

[0042] The present embodiment provides a preparation method of lutein ester crystal, specifically as follows:

[0043] The commercially available 200 kg of lutein extract (total lutein ester content 22.01%) is packaged using an iron drum, and is placed in a 65°C water bath for 36 h (viscosity value of the melted extract is 6548 mPa·s). The lutein extract is pumped into a crystallization tank using vacuum negative pressure. 8 kg of potassium hydroxide is dissolved in 800 L of 90% ethanol solution, which is transferred into the crystallization tank. 400 L of n-hexane is added, and the saponification is stirred at 60°C for 1 h. After the saponification is completed, the solution layer is separated out. The remaining extract layer is added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature is lowered for crystallization. The temperature lowering crystallization process is as follows: the stirring speed is controlled at 60 rpm, and the temperature is lowered to 5°C at a rate of 2.5°C / h. The temperature is kept at 5°C for 3 h. After the crystallization is completed, a plate and frame filter is used to filter the material liquid at a filtration pressure of 0.5 MPa. The filter cake is washed twice using 400 L of the above-mentioned mixed solvent of n-hexane and isopropyl alcohol. The lutein ester crystals are obtained by drying at 55°C under a vacuum degree of -0.08 MPa. The weight yield of the lutein ester crystals is 45.84 kg, the total lutein ester content in the lutein ester crystals is 80.25% as detected, and the content yield is 83.56%.

[0044] Example 2

[0045] The present embodiment provides a preparation method of lutein ester crystals, which is specifically as follows:

[0046] The commercially available 200 kg of lutein extract (total lutein ester content 22.01%) is packaged using an iron drum, and is placed in a 65°C water bath for 36 h (viscosity value of the melted extract is 6548 mPa·s). The lutein extract is pumped into a crystallization tank using vacuum negative pressure. 8 kg of potassium hydroxide is dissolved in 800 L of 90% ethanol solution, which is transferred into the crystallization tank. 400 L of n-hexane is added, and the saponification is stirred at 60°C for 1 h. After the saponification is completed, the solution layer is separated out. The remaining extract layer is added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature is lowered for crystallization. The temperature lowering crystallization process is as follows: the stirring speed is controlled at 60 rpm, and the temperature is lowered to 5°C at a rate of 2.5°C / h. The temperature is kept at 5°C for 3 h. After the crystallization is completed, a plate and frame filter is used to filter the material liquid at a filtration pressure of 0.5 MPa. The filter cake is washed twice using 400 L of the above-mentioned mixed solvent of n-hexane and isopropyl alcohol. The lutein ester crystals are obtained by drying at 55°C under a vacuum degree of -0.08 MPa. The weight yield of the lutein ester crystals is 45.84 kg, the total lutein ester content in the lutein ester crystals is 80.25% as detected, and the content yield is 83.56%.

[0047] Example 3

[0048] The commercially available 200 kg of lutein extract (total lutein ester content 31.25%) was packaged using an iron drum, and was placed in a 70°C water bath for 36 h (viscosity value of the melted extract was 5460 mPa-s). The lutein extract was pumped into a crystallization tank using vacuum negative pressure, 6 kg of potassium hydroxide was dissolved in 800 L of 90% methanol solution, and was transferred into the crystallization tank. Then, 400 L of n-hexane was added, and the saponification was performed at 55°C for 0.5 h. After the saponification was completed, the solution layer was separated out, and the remaining extract layer was added with 2800 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3. The crystallization was started. The crystallization process was as follows: the stirring speed was controlled at 60 rpm, and the temperature was decreased to 5°C at a rate of 2.5°C / h. The temperature was maintained at 5°C for 2 h. After the crystallization was completed, the filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol. The filter cake was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 68.63 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 34.32%, and the total lutein ester content in the lutein ester crystals was 82.15% by detection. The content yield was 90.21%.

[0049] Comparative Example 1

[0050] This comparative example provides a preparation method of lutein ester crystals, which is as follows:

[0051] The commercially available 200 kg of lutein extract (total lutein ester content 22.01%) was heated and melted, and was pumped into a crystallization tank using vacuum negative pressure. Then, 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3 was added, and the crystallization was started. The crystallization process was as follows: the stirring speed was controlled at 60 rpm, and the temperature was decreased to 5°C at a rate of 2.5°C / h. The temperature was maintained at 5°C for 3 h. After the crystallization was completed, the filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol. The filter cake was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 38.11 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 19.06%, and the total lutein ester content in the lutein ester crystals was 75.45% by detection. The content yield was 65.32%.

[0052] Comparative Example 2

[0053] Commercially available 200 kg of lutein extract (total lutein ester content 31.25%) was heated and melted, and then vacuum negative pressure was used to extract the lutein extract into a crystallization tank. 2800 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3 was added, and cooling crystallization was started. The cooling crystallization process was as follows: the stirring speed was controlled at 60 rpm throughout the process, and the temperature was lowered to 5°C at a rate of 2.5°C / h, and the temperature was kept at 5°C for 2 hours. After the crystallization was completed, a plate and frame filter was used, the filtration pressure was 0.5 MPa, the filter material was filtered, 400 L of the above-mentioned mixed solvent of n-hexane and isopropyl alcohol was used to wash the filter cake twice, and 57.62 kg of lutein ester crystals were obtained after drying at 55°C and a vacuum degree of -0.08 MPa, with a lutein ester crystal yield of 28.81%. The total lutein ester content in the lutein ester crystals was 78.21%, and the content yield was 72.10%.

[0054] Comparative Example 3

[0055] Commercially available 200 kg of lutein extract (total lutein ester content 22.01%) was heated and melted, and then vacuum negative pressure was used to extract the lutein extract into a crystallization tank. 800 L of a 90% ethanol solution was added, and 8 kg of potassium hydroxide was dissolved in the solution, which was then transferred into the crystallization tank. Saponification was carried out at 60°C for 1 h under stirring, and after the saponification was completed, the solvent layer was separated out, and the remaining extract layer was added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and cooling crystallization was started. The cooling crystallization process was as follows: the stirring speed was controlled at 60 rpm throughout the process, and the temperature was lowered to 5°C at a rate of 2.5°C / h, and the temperature was kept at 5°C for 3 hours. After the crystallization was completed, a plate and frame filter was used, the filtration pressure was 0.5 MPa, the filter material was filtered, 400 L of the above-mentioned mixed solvent of n-hexane and isopropyl alcohol was used to wash the filter cake twice, and 43.35 kg of lutein ester crystals were obtained after drying at 55°C and a vacuum degree of -0.08 MPa, with a lutein ester crystal yield of 21.68%. The total lutein ester content in the lutein ester crystals was 78.51%, and the content yield was 77.32%.

[0056] Comparative Example 4

[0057] The 200 kg of commercially available lutein extract (total lutein ester content 22.01%) was heated and melted, and then vacuum negative pressure was used to extract the lutein extract into a crystallization tank. 8 kg of potassium hydroxide was dissolved in 800 L of 80% ethanol solution, transferred into the crystallization tank, and 400 L of n-hexane was added. The mixture was stirred at 60°C for 1 h for saponification. After saponification, the mixture was allowed to stand, and the solvent layer was separated out. The remaining extract layer was added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature was lowered for crystallization. The specific process of temperature lowering for crystallization was as follows: the stirring speed was controlled at 60 rpm, and the temperature was lowered to 5°C at a rate of 2.5°C / h. The mixture was kept at 5°C for 3 hours. After crystallization, a plate and frame filter was used for filtration at a filtration pressure of 0.5 MPa. The filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol, and was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 44.73 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 22.37%, and the total lutein ester content in the lutein ester crystals was 77.21% by detection, and the content yield was 78.46%.

[0058] Comparative Example 5

[0059] The 200 kg of commercially available lutein extract (total lutein ester content 22.01%) was packaged in an iron drum, and was soaked in a 65°C water bath for 36 h (the viscosity value of the melted extract was 6548 mPa·s). The lutein extract was extracted into a crystallization tank using vacuum negative pressure. 8 kg of potassium hydroxide was dissolved in 800 L of 90% ethanol solution, transferred into the crystallization tank, and 400 L of acetone was added. The mixture was stirred at 60°C for 1 h for saponification. After saponification, the mixture was allowed to stand, and the solvent layer was separated out. The remaining extract layer was added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature was lowered for crystallization. The specific process of temperature lowering for crystallization was as follows: the stirring speed was controlled at 60 rpm, and the temperature was lowered to 5°C at a rate of 2.5°C / h. The mixture was kept at 5°C for 3 hours. After crystallization, a plate and frame filter was used for filtration at a filtration pressure of 0.5 MPa. The filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol, and was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 41.74 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 20.87%, and the total lutein ester content in the lutein ester crystals was 79.25% by detection, and the content yield was 75.15%.

[0060] Comparative Example 6

[0061] The 200 kg of commercially available lutein extract (total lutein ester content 22.01%) was heated and melted, and then vacuum negative pressure was used to extract the lutein extract into a crystallization tank. 13 kg of potassium hydroxide was dissolved in 800 L of 90% ethanol solution, transferred into the crystallization tank, and 400 L of n-hexane was added. The mixture was stirred at 60°C for 1 h for saponification. After saponification, the mixture was allowed to stand, and the solvent layer was separated out. The remaining extract layer was added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature was lowered for crystallization. The specific process of temperature lowering for crystallization was as follows: the stirring speed was controlled at 60 rpm, and the temperature was lowered to 5°C at a rate of 2.5°C / h. The mixture was kept at 5°C for 3 h. After crystallization, a plate and frame filter was used for filtration at a filtration pressure of 0.5 MPa. The filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol, and was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 32.60 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 16.30%, and the total lutein ester content in the lutein ester crystals was 81.74% by detection, and the content yield was 60.53%.

[0062] Comparative Example 7

[0063] The 200 kg of commercially available lutein extract (total lutein ester content 22.01%) was heated and melted, and then vacuum negative pressure was used to extract the lutein extract into a crystallization tank. 8 kg of potassium hydroxide was dissolved in 800 L of 90% ethanol solution, transferred into the crystallization tank, and 700 L of n-hexane was added. The mixture was stirred at 60°C for 1 h for saponification. After saponification, the mixture was allowed to stand, and the solvent layer was separated out. The remaining extract layer was added with 2200 L of a mixed solvent of n-hexane and isopropyl alcohol at a ratio of 1:3, and the temperature was lowered for crystallization. The specific process of temperature lowering for crystallization was as follows: the stirring speed was controlled at 60 rpm, and the temperature was lowered to 5°C at a rate of 2.5°C / h. The mixture was kept at 5°C for 3 h. After crystallization, a plate and frame filter was used for filtration at a filtration pressure of 0.5 MPa. The filter cake was washed twice with 400 L of the mixed solvent of n-hexane and isopropyl alcohol, and was dried at 55°C under a vacuum degree of -0.08 MPa to obtain 41.76 kg of lutein ester crystals. The weight yield of the lutein ester crystals was 20.88%, and the total lutein ester content in the lutein ester crystals was 80.14% by detection, and the content yield was 76.03%.

Claims

1. A method for preparing lutein ester crystals, characterized in that: The following steps are involved: Step S1, adding a mixed solvent of an inorganic base, an alkane and a fatty alcohol to the lutein extract, and heating the mixture to perform a saponification reaction of the impurity fatty acid ester; Step S2: After the impurity fatty acid ester is saponified, solid-liquid separation is performed to separate the solvent layer to obtain an extract layer; Step S3, adding an organic mixed solvent to the extract layer to dissolve and stir, and cooling and crystallizing; Step S4: After the crystallization is completed, the lutein ester crystals are filtered, washed, and dried.

2. The method for preparing lutein ester crystals according to claim 1, wherein: The inorganic base described in step S1 is one of potassium hydroxide and sodium hydroxide, the alkane is one of n-hexane, cyclohexane and n-pentane, and the fatty alcohol is one of methanol, ethanol or isopropanol.

3. The method for preparing lutein ester crystals according to claim 2, wherein: In step S1, the amount of inorganic base used is 2%-6% of the weight of the lutein extract; the weight-volume ratio of the lutein extract to the alkane is 1:1-3 (kg / L); the weight-volume ratio of the lutein extract to the fatty alcohol is 1:3-5 (kg / L); and the fatty alcohol is an aqueous solution of 85%-95% methanol, isopropanol or ethanol.

4. The method for preparing lutein ester crystals according to claim 1, wherein: The saponification reaction temperature in step S1 is 50-60° C., and the saponification time is 0.5-1 h.

5. The method for preparing lutein ester crystals according to claim 1, wherein: The mixed solvent in step S3 includes n-hexane and a low-molecular alcohol containing 1 to 4 carbon atoms, wherein the low-molecular alcohol includes one or more of methanol, ethanol or isopropanol.

6. The method for preparing lutein ester crystals according to claim 5, wherein: The volume ratio of n-hexane to low molecular weight alcohol in the mixed solvent in step S3 is 1:2.5-4.

7. The method for preparing lutein ester crystals according to claim 1, wherein: The mass volume ratio of the lutein extract in step S1 to the mixed solvent in step S3 is 1:10-16 in kg / L.

8. The method for preparing lutein ester crystals according to claim 1, wherein: In step S3, the crystallization is carried out by cooling, with the initial temperature being 25-30°C, and the temperature is lowered to 5-10°C at a rate of 3-5°C / h, and kept at this temperature for 2-3h.

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