Preparation method of astaxanthin oil and prepared astaxanthin oil

Abstract

The invention relates to the technical field of preparation of natural extracts, in particular to a preparation method of astaxanthin oil and the prepared astaxanthin oil. According to the preparation method of the astaxanthin oil, provided by the invention, the wall breaking efficiency of the haematococcus pluvialis raw material is effectively improved, and the wall breaking loss of the astaxanthin is remarkably reduced; meanwhile, by means of the method, efficient separation of astaxanthin cis-trans isomers can be achieved, the astaxanthin oil with the trans-astaxanthin content accounting for 95% or above is finally obtained, and the total astaxanthin content is increased to 30% or above. According to the method, efficient enrichment of trans-astaxanthin in a natural product is achieved, the prepared astaxanthin oil product is free of peculiar smell and can serve as high-quality astaxanthin oil, and a high-quality raw material is provided for the field of functional food and medicine.

Description

Technical Field

[0001] The present invention relates to the technical field of natural extract preparation, in particular to a preparation method of astaxanthin oil and the prepared astaxanthin oil. Background Art

[0002] Astaxanthin is a terpene carotenoid with excellent coloring properties and strong biological activity. The linear portion of the astaxanthin molecule contains multiple double bonds, which are classified as cis-astaxanthin and trans-astaxanthin, depending on whether the double bonds are cis- or trans-configured. Trans-astaxanthin has an antioxidant effect 500 times that of vitamin E. Trans-astaxanthin accounts for 70%-80% of astaxanthin derived from Haematococcus pluvialis. To enhance the antioxidant capacity of astaxanthin, there is an urgent need to develop astaxanthin oil products with high trans-astaxanthin content.

[0003] The cell wall of Haematococcus pluvialis is composed of dense, multi-layered structures, reaching thicknesses of several microns. Astaxanthin is stored in an esterified state (monoester or diester) within intracellular liposomes, making direct extraction extremely inefficient. Patent application CN115073341A discloses a novel, highly efficient astaxanthin cell wall disruption method, utilizing ultrahigh-pressure homogenization and supercritical extraction to achieve a cell wall disruption rate exceeding 99%. However, the maximum astaxanthin yield is only 90%, with significant astaxanthin loss during the cell wall disruption process. Patent application CN114957076A discloses a process and apparatus for extracting astaxanthin from Haematococcus pluvialis, utilizing multiple freeze-drying and homogenization processes to achieve a cell wall disruption rate of 98%. However, the cell wall disruption process is cumbersome, making it difficult to commercialize. Patent application CN104480013A discloses a cell wall disruption method for Haematococcus pluvialis, utilizing freezing and ice crystallization combined with colloidal milling and multiple homogenization processes. This results in a relatively complex cell wall disruption process and a cell wall disruption rate of only 96%.

[0004] Furthermore, the trans-astaxanthin content in existing astaxanthin oil products still needs to be improved, and effectively separating cis-astaxanthin from trans-astaxanthin to increase the trans-astaxanthin content in the product is quite difficult. Therefore, it is necessary to develop an astaxanthin oil preparation method that can reduce astaxanthin cell wall loss and increase the proportion of trans-astaxanthin. Summary of the Invention

[0005] The invention provides a preparation method of astaxanthin oil and the prepared astaxanthin oil.

[0006] In order to reduce the loss of astaxanthin during the cell wall breaking process of raw materials and increase the content ratio of trans-astaxanthin in astaxanthin oil products, the present invention has developed a preparation method for astaxanthin oil. The method uses Haematococcus pluvialis as raw material and adopts a low-temperature ultrafine grinding and cell wall breaking-supercritical distillation extraction synergistic process system; first, under low-temperature protection conditions, the Haematococcus pluvialis is subjected to ultrafine grinding and cell wall breaking treatment, and the low-temperature environment enhances the brittleness of the cell wall, significantly improves the cell wall breaking efficiency, and reduces the cell wall breaking loss of astaxanthin; further, the raw material that has undergone cell wall breaking is subjected to supercritical distillation extraction and separation technology, and supercritical carbon dioxide extraction is combined with gradient pressure distillation treatment to achieve efficient separation of astaxanthin cis and trans isomers, thereby significantly increasing the content ratio of trans-astaxanthin in the prepared astaxanthin oil.

[0007] Specifically, the present invention provides the following technical solutions.

[0008] In a first aspect, the present invention provides a method for preparing astaxanthin oil, using Haematococcus pluvialis as a raw material, the method comprising: subjecting the Haematococcus pluvialis to a low-temperature ultrafine grinding and wall-breaking treatment, followed by supercritical carbon dioxide extraction and gradient pressure distillation; The gradient pressure distillation treatment includes three stages; the first stage distillation treatment is carried out at a pressure of 4~7MPa; the second stage distillation treatment is carried out at a pressure of 9~14MPa; the third stage distillation treatment is carried out at a pressure of 18~22MPa, and the trans-astaxanthin fraction is collected.

[0009] In the above-mentioned gradient pressure distillation process, the first stage removes fat-soluble impurities (free fatty acids) at a pressure of 4-7 MPa; the second stage separates cis-astaxanthin at a pressure of 9-14 MPa; and the third stage collects the trans-astaxanthin fraction at a pressure of 18-22 MPa (i.e., the fraction with a top pressure of 18-22 MPa is collected). The present inventors have discovered that the above-mentioned gradient pressure distillation process can effectively remove fat-soluble impurities from the extract obtained by supercritical carbon dioxide extraction, and can achieve efficient separation of cis- and trans-astaxanthin, resulting in a trans-astaxanthin-rich fraction, significantly increasing the proportion of trans-astaxanthin in the astaxanthin contained in the resulting astaxanthin oil.

[0010] Preferably, the gradient pressure distillation treatment includes three stages; the first stage distillation treatment is carried out at a pressure of 5~6MPa; the second stage distillation treatment is carried out at a pressure of 10~12MPa; the third stage distillation treatment is carried out at a pressure of 18~20MPa, and the trans-astaxanthin fraction is collected.

[0011] In the above method, the raw material is preferably Haematococcus pluvialis powder.

[0012] In the above method, the temperature of the first stage distillation treatment is 30-35°C, the temperature of the second stage distillation treatment is 35-40°C, and the temperature of the third stage distillation treatment is 40-45°C.

[0013] Preferably, the temperature of the first stage distillation treatment is 32-34°C, the temperature of the second stage distillation treatment is 37-39°C, and the temperature of the third stage distillation treatment is 42-44°C.

[0014] Preferably, the time for the first stage distillation treatment is 25-35 minutes, the time for the second stage distillation treatment is 30-50 minutes, and the time for the third stage distillation treatment is 90-155 minutes.

[0015] More preferably, the first stage distillation treatment lasts for 30-35 minutes, the second stage distillation treatment lasts for 30-50 minutes, and the third stage distillation treatment lasts for 100-155 minutes. In the above method, the low-temperature ultrafine pulverization and wall-breaking treatment is carried out at -20 to 0°C.

[0016] Compared with other wall-breaking methods, low temperature combined with ultrafine grinding to break the wall can significantly improve the wall-breaking efficiency of Haematococcus pluvialis. There is no need to use cumbersome multiple freezing or homogenization treatments, and the wall-breaking efficiency can be increased to more than 99%, which is beneficial to reduce the loss of astaxanthin during the wall-breaking process.

[0017] Preferably, the wall breaking temperature of the low-temperature ultrafine grinding and wall breaking treatment is -10~-5°C.

[0018] Preferably, the low-temperature ultrafine grinding and wall-breaking treatment comprises: mixing Haematococcus pluvialis with a filter aid and an antioxidant, and performing ultrafine grinding treatment at -20 to 0°C under nitrogen protection conditions.

[0019] Preferably, the crushing time is 5 to 20 minutes (more preferably 8 to 12 minutes).

[0020] Preferably, the flow rate of the nitrogen is 0.3-0.7 m³ / h.

[0021] Adding antioxidants during the low-temperature ultrafine grinding and cell-breaking process can inhibit the oxidative degradation of astaxanthin. The combination of low-temperature ultrafine grinding and cell-breaking with the introduction of antioxidants can reduce astaxanthin cell-breaking losses to less than 0.6%. Furthermore, antioxidants help inhibit the conversion of trans-astaxanthin to cis-astaxanthin during cell-breaking and extraction.

[0022] Preferably, the antioxidant is selected from at least one of tocopherol, carnosic acid, and tert-butylhydroquinone, and the added amount is preferably 0.1% to 1% of the mass of Haematococcus pluvialis.

[0023] Further preferably, the antioxidant is tocopherol or carnosic acid, and the added amount is 0.3% to 0.6% of the mass of Haematococcus pluvialis.

[0024] The purpose of adding filter aids during the low-temperature ultrafine grinding and wall breaking process is to increase the fluidity of the material during the grinding process, prevent the material from sticking to the wall, and improve the wall breaking efficiency.

[0025] Preferably, the filter aid is selected from at least one of silicon dioxide, perlite, and calcium carbonate, and the added amount is preferably 40% to 200% of the mass of Haematococcus pluvialis.

[0026] Further preferably, the filter aid is silicon dioxide or perlite; the preferred addition ratio is 60% to 100% of the mass of Haematococcus pluvialis.

[0027] During the low-temperature ultrafine grinding and wall-breaking process, nitrogen with a purity of ≥99.9% and an oxygen content of <0.1% is continuously introduced, which is conducive to more effectively preventing oxidative degradation and reducing the oxidative loss of astaxanthin.

[0028] In the above method, the pressure of the supercritical carbon dioxide extraction is 50-80 MPa, the temperature is 35-65° C., and the carbon dioxide flow rate is 300-500 L / h.

[0029] Preferably, the supercritical carbon dioxide extraction time is 2 to 5 hours.

[0030] Further preferably, the supercritical carbon dioxide extraction pressure is 65-75 MPa, the extraction temperature is 50-55° C., the carbon dioxide flow rate is 350-450 L / h, and the extraction time is 3-4 h.

[0031] The supercritical carbon dioxide extraction can be carried out in the kettle.

[0032] Preferably, the supercritical carbon dioxide extraction equipment is provided with 15 to 40 theoretical plates and a reflux ratio of 1 to 5.

[0033] Preferably, the number of theoretical plates is 20 to 30, and the reflux ratio is 2 to 4. Preferably, oil is used as an entrainer in the supercritical carbon dioxide extraction.

[0034] Preferably, the supercritical carbon dioxide extraction uses medium-chain triglycerides and / or safflower seed oil as an entrainer. The amount of the entrainer added is preferably 1-10‰ (preferably 4-8‰) of the mass of the Haematococcus pluvialis.

[0035] In the astaxanthin oil prepared by the above preparation method, the proportion of trans-astaxanthin in the total astaxanthin content (i.e., the total content of trans-astaxanthin and cis-astaxanthin) is ≥ 95%, and the total content of trans-astaxanthin and cis-astaxanthin is ≥ 30%. The above proportions are percentages by mass.

[0036] In a second aspect, the present invention provides astaxanthin oil prepared by the above-described preparation method.

[0037] Preferably, in the astaxanthin oil, the proportion of trans-astaxanthin in the total content of trans-astaxanthin and cis-astaxanthin is ≥ 95%, and the total content of trans-astaxanthin and cis-astaxanthin is ≥ 30%. Furthermore, the astaxanthin oil is odorless.

[0038] In a third aspect, the present invention provides the above-mentioned preparation method or the use of the astaxanthin oil in the preparation of food, medicine, cosmetics or feed.

[0039] The beneficial effects of the present invention include at least: the astaxanthin oil preparation method provided by the present invention can achieve a cell wall breaking efficiency of over 99% for Haematococcus pluvialis raw material, and the astaxanthin cell wall loss can be controlled to below 0.6%. Furthermore, the method can achieve efficient separation of astaxanthin cis and trans isomers, ultimately producing astaxanthin oil with a trans-astaxanthin content (the ratio of trans-astaxanthin to the total astaxanthin content) exceeding 95%, and the astaxanthin content is increased to over 30%. This method achieves efficient enrichment of trans-astaxanthin in natural products, and the resulting astaxanthin oil product is odorless and can be used as high-quality astaxanthin oil, providing a high-quality raw material for functional foods and pharmaceuticals. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] In the following examples and comparative examples, the trans-astaxanthin ratio refers to the mass ratio of trans-astaxanthin to the total astaxanthin content (i.e., the total content of trans-astaxanthin and cis-astaxanthin).

[0042] Example 1 This embodiment provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and cis-astaxanthin accounting for 14.7%) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0043] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃ condition, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), grinding time 10min, the wall breaking rate reached 99.9%, and the astaxanthin wall breaking loss was 0.45%.

[0044] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 70 MPa, a temperature of 52°C, a CO2 flow rate of 350 L / h, an entrainer of medium-chain triglycerides (5‰ addition amount), a theoretical plate number of 25, a reflux ratio of 2, and an extraction time of 3.5 h.

[0045] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 6 MPa and a temperature of 32 °C for 30 min; the second stage is to separate cis-astaxanthin at a pressure of 12 MPa and a temperature of 38 °C for 40 min; the third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 20 MPa and a temperature of 44 °C for 120 min.

[0046] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 31.5%, of which trans-astaxanthin accounted for 96.7%. The product was orange-red transparent oil with no irritating odor.

[0047] Example 2 This embodiment provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 4.50% and cis-astaxanthin accounting for 14.1%) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 8 kg of perlite filter aid, and 0.03 kg of carnosic acid (antioxidant).

[0048] (2) Low-temperature ultrafine grinding and wall breaking: Under -5°C conditions, nitrogen protection (nitrogen purity ≥ 99.9%, flow rate 0.6m³ / h), the grinding time is 12 minutes, the wall breaking rate reaches 99.8%, and the astaxanthin wall breaking loss is 0.55%.

[0049] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 65 MPa, a temperature of 55°C, a CO2 flow rate of 400 L / h, an entrainer of medium-chain triglycerides (added in an amount of 8‰), a theoretical plate number of 20, a reflux ratio of 2, and an extraction time of 3 h.

[0050] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 6 MPa and a temperature of 34 °C for 25 min. The second stage is to separate cis-astaxanthin at a pressure of 10 MPa and a temperature of 38 °C for 35 min. The third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 18 MPa and a temperature of 42 °C for 100 min.

[0051] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 30.8%, of which trans-astaxanthin accounted for 97.2%. The product was orange-red transparent oil with no irritating odor.

[0052] Example 3 This embodiment provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and cis-astaxanthin accounting for 14.7%) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0053] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃ condition, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), grinding time 10min, the wall breaking rate reached 99.7%, and the astaxanthin wall breaking loss was 0.41%.

[0054] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 75 MPa, a temperature of 50°C, a CO2 flow rate of 450 L / h, safflower seed oil as the entrainer (added amount of 4‰), a theoretical plate number of 30, a reflux ratio of 4, and an extraction time of 4 h.

[0055] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 5 MPa and a temperature of 33 °C for 35 min. The second stage is to separate cis-astaxanthin at a pressure of 11 MPa and a temperature of 37 °C for 30 min. The third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 19 MPa and a temperature of 43 °C for 155 min.

[0056] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 31.2%, of which trans-astaxanthin accounted for 96.8%. The product was orange-red transparent oil with no irritating odor.

[0057] Example 4 This embodiment provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and cis-astaxanthin accounting for 14.7%) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0058] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃ conditions, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), grinding time 10min, the wall breaking rate reached 99.8%, and the astaxanthin wall breaking loss was 0.43%.

[0059] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 68 MPa, a temperature of 54°C, a CO2 flow rate of 430 L / h, safflower seed oil as the entrainer (added amount of 4‰), a theoretical plate number of 24, a reflux ratio of 3, and an extraction time of 3.5 h.

[0060] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 6 MPa and a temperature of 32 °C for 30 min. The second stage is to separate cis-astaxanthin at a pressure of 12 MPa and a temperature of 39 °C for 50 min. The third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 18 MPa and a temperature of 43 °C for 110 min.

[0061] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 31.1%, of which trans-astaxanthin accounted for 96.9%. The product was orange-red transparent oil with no irritating odor.

[0062] Comparative Example 1 In this comparative example, a traditional cell wall breaking process was used to prepare astaxanthin oil using Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and a cis-astaxanthin content of 14.7%, the raw materials being the same as those in Example 1) as a raw material, comprising the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0063] (2) Ultrafine grinding and wall breaking: Under the condition of 10℃ and the grinding time of 20min, the wall breaking rate is only 94.1%, and the astaxanthin wall breaking loss reaches 5.8%.

[0064] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 70 MPa, a temperature of 52°C, a CO2 flow rate of 350 L / h, an entrainer of medium-chain triglycerides (5‰ addition amount), a theoretical plate number of 25, a reflux ratio of 2, and an extraction time of 3.5 h.

[0065] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 6 MPa and a temperature of 32 °C for 30 min; the second stage is to separate cis-astaxanthin at a pressure of 12 MPa and a temperature of 38 °C for 40 min; the third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 20 MPa and a temperature of 44 °C for 120 min.

[0066] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 20.4%, of which trans-astaxanthin accounted for 92.4%. The product was orange-red transparent oil with no irritating odor.

[0067] Comparative Example 2 In this comparative example, a solvent extraction process was used to prepare astaxanthin oil using Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and a cis-astaxanthin content of 14.7%, the raw materials being the same as those in Example 1) as a raw material, comprising the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0068] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃ conditions, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), the grinding time is 10min, the wall breaking rate reaches 99.9%, and the astaxanthin wall breaking loss is 0.43%.

[0069] (3) Solvent extraction: The broken algae powder in step (2) was extracted with ethyl acetate 4 times, stirring for 2 hours each time, the extraction temperature was 50°C, and 40L of extraction solvent was added each time.

[0070] (4) Concentration and removal of residual solvent: The extract obtained in step (3) is concentrated at 40° C. to remove residual solvent to obtain an astaxanthin oil product.

[0071] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 10.5%, of which trans-astaxanthin accounted for 80.4%. The product was orange-red transparent oil with a seaweed smell.

[0072] Comparative Example 3 This comparative example provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (astaxanthin content 5.50%, cis-form accounted for 14.7%, the raw material is the same as that in Example 1) as a raw material, comprising the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol antioxidant.

[0073] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), the grinding time is 10min, the wall breaking rate reaches 99.9%, and the astaxanthin wall breaking loss is 0.48%.

[0074] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 70 MPa, a temperature of 52°C, a CO2 flow rate of 350 L / h, an entrainer of medium-chain triglycerides (5‰ addition amount), a theoretical plate number of 25, a reflux ratio of 2, and an extraction time of 3.5 h.

[0075] (4) Distillation: The extract from step (3) is directly distilled at a pressure of 25 MPa and a temperature of 40°C for 120 min, and the fractions are collected to obtain the astaxanthin oil product.

[0076] Results: The astaxanthin oil product contained 22.4% of which trans-astaxanthin accounted for 84.7%. The product was orange-red transparent oil with a seaweed smell.

[0077] Comparative Example 4 This comparative example provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and a cis-astaxanthin content of 14.7%, the same as in Example 1) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0078] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃ conditions, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), the grinding time is 10min, the wall breaking rate reaches 99.7%, and the astaxanthin wall breaking loss is 0.52%.

[0079] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 70 MPa, a temperature of 52°C, a CO2 flow rate of 350 L / h, an entrainer of medium-chain triglycerides (5‰ addition amount), a theoretical plate number of 25, a reflux ratio of 2, and an extraction time of 3.5 h.

[0080] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 3 MPa and a temperature of 32 °C for 30 min. The second stage is to separate cis-astaxanthin at a pressure of 8 MPa and a temperature of 38 °C for 40 min. The third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 17 MPa and a temperature of 44 °C for 120 min.

[0081] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 24.5%, of which trans-astaxanthin accounted for 88.7%. The product was orange-red transparent oil with a seaweed smell.

[0082] Comparative Example 5 This comparative example provides a method for preparing astaxanthin oil, which uses Haematococcus pluvialis powder (with an astaxanthin content of 5.50% and a cis-astaxanthin content of 14.7%, the same as in Example 1) as a raw material, and comprises the following steps: (1) Raw material preparation: 10 kg of Haematococcus pluvialis powder, 6 kg of silica filter aid, and 0.05 kg of tocopherol (antioxidant).

[0083] (2) Low-temperature ultrafine grinding and wall breaking: Under -10℃, nitrogen protection (nitrogen purity ≥99.9%, flow rate 0.5m³ / h), the grinding time is 10min, the wall breaking rate reaches 99.5%, and the astaxanthin wall breaking loss is 0.48%.

[0084] (3) Supercritical carbon dioxide extraction: The broken algae powder from step (2) was added to the reactor, with a bottom pressure of 70 MPa, a temperature of 52°C, a CO2 flow rate of 350 L / h, an entrainer of medium-chain triglycerides (5‰), a theoretical plate number of 25, a reflux ratio of 2, and an extraction time of 3.5 h.

[0085] (4) Gradient pressure distillation: It is divided into three stages. The first stage is to remove free fatty acids at a pressure of 8 MPa and a temperature of 32 °C for 30 min. The second stage is to separate cis-astaxanthin at a pressure of 15 MPa and a temperature of 38 °C for 40 min. The third stage is to collect the trans-astaxanthin fraction (i.e., the astaxanthin oil product) at a pressure of 25 MPa and a temperature of 44 °C for 120 min.

[0086] Results: The total astaxanthin content (i.e. the total content of trans-astaxanthin and cis-astaxanthin) in the astaxanthin oil product was 28.5%, of which trans-astaxanthin accounted for 92.3%. The product was orange-red transparent oil with a seaweed smell.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing astaxanthin oil, characterized in that: The method uses Haematococcus pluvialis as raw material, comprising: subjecting the Haematococcus pluvialis to low-temperature ultrafine grinding and wall breaking, and then subjecting the algae to supercritical carbon dioxide extraction and gradient pressure distillation; The gradient pressure distillation treatment includes three stages; the first stage distillation treatment is carried out at a pressure of 4~7MPa; the second stage distillation treatment is carried out at a pressure of 9~14MPa; the third stage distillation treatment is carried out at a pressure of 18~22MPa, and the trans-astaxanthin fraction is collected.

2. The preparation method according to claim 1, characterized in that The temperature of the first stage distillation treatment is 30-35°C, the temperature of the second stage distillation treatment is 35-40°C, and the temperature of the third stage distillation treatment is 40-45°C; Preferably, the time for the first stage distillation treatment is 25-35 minutes, the time for the second stage distillation treatment is 30-50 minutes, and the time for the third stage distillation treatment is 90-155 minutes.

3. The preparation method according to claim 1 or 2, characterized in that The low-temperature ultrafine grinding and wall-breaking treatment is carried out at -20 to 0°C, preferably at -10 to -5°C.

4. The preparation method according to claim 3, characterized in that The low-temperature ultrafine grinding and wall-breaking treatment comprises: mixing Haematococcus pluvialis with a filter aid and an antioxidant, and performing ultrafine grinding treatment under nitrogen protection conditions; Preferably, the crushing time is 5 to 20 minutes; Preferably, the filter aid is selected from at least one of silicon dioxide, perlite, and calcium carbonate, and the added amount is preferably 40% to 200% of the mass of Haematococcus pluvialis; And / or, the antioxidant is selected from at least one of tocopherol, carnosic acid, and tert-butylhydroquinone, and the added amount is preferably 0.1% to 1% of the mass of Haematococcus pluvialis.

5. The preparation method according to any one of claims 1 to 4, characterized in that The supercritical carbon dioxide extraction pressure is 50-80 MPa, the temperature is 35-65°C, and the carbon dioxide flow rate is 300-500 L / h; Preferably, the supercritical carbon dioxide extraction time is 2 to 5 hours.

6. The preparation method according to claim 5, characterized in that The supercritical carbon dioxide extraction equipment is provided with 15 to 40 theoretical plates, and / or the reflux ratio is 1 to 5.

7. The preparation method according to any one of claims 1 to 6, characterized in that The supercritical carbon dioxide extraction uses oil as an entrainer; Preferably, the supercritical carbon dioxide extraction uses medium-chain triglycerides and / or safflower seed oil as entrainers; the added amount of the entrainer is preferably 1-10‰ of the mass of the Haematococcus pluvialis.

8. The preparation method according to any one of claims 1 to 7, characterized in that In the astaxanthin oil, the proportion of trans-astaxanthin in the total content of trans-astaxanthin and cis-astaxanthin is ≥95%, and the total content of trans-astaxanthin and cis-astaxanthin is ≥30%.

9. Astaxanthin oil prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the preparation method according to any one of claims 1 to 8 or the astaxanthin oil according to claim 9 in the preparation of food, medicine, cosmetics or feed.