A method for preparing food-grade antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal
Patent Information
- Application Number
- PCT/IB2026/057315
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-07-15
- Publication Date
- 2026-10-01
Smart Images
Figure IB2026057315_01102026_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] A Method for Preparing Food-Grade Antarctic Krill Oil by Dual-Concentration Ethanol Extraction and Low-Temperature Standing Impurity Removal
[0003] TECHNICAL FIELD
[0004] The present invention relates to the technical field of deep processing of aquatic resources, and specifically relates to a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal.
[0005] BACKGROUND ART
[0006] Antarctic krill is a small planktonic crustacean with enormous biomass reserves. Antarctic krill is rich in protein, chitin, astaxanthin, and unique phospholipid-type Omega-3 polyunsaturated fatty acids, wherein eicosapentaenoic acid (EP A) and docosahexaenoic acid (DHA) mainly exist in phospholipid form, which makes Antarctic krill oil superior to conventional triglyceride-type fish oil in terms of bioavailability.
[0007] At present, preparation methods for Antarctic krill oil mainly include organic solvent extraction, supercritical fluid extraction, and lower-alcohol extraction. Organic solvent extraction commonly uses nonpolar or low-polarity solvents such as n-hexane, petroleum ether, No. 6 solvent oil, cyclohexane, and ethyl acetate, which poses safety risks of solvent residues, and the desolventizing process requires relatively high temperatures, which easily causes oxidative degradation of polyunsaturated fatty acids and astaxanthin. Although supercritical carbon dioxide extraction gives a pure product without solvent residues, the equipment investment is huge and the operating cost is high, and the extraction efficiency for highly polar phospholipid lipids is relatively low, thereby limiting industrial application. Lower-alcohol extraction generally uses an ethanol aqueous solution as the extraction solvent. Ethanol is a solvent allowed for use in food processing, has the advantages of high safety and mild operating conditions, and is moreDESCRIPTION
[0008] suitable for preparing food-grade Antarctic krill oil.
[0009] However, when an existing ethanol extraction technology uses ethanol of a single concentration for one-time extraction, the process stability is insufficient. When ethanol of a relatively low concentration is used, polar phospholipid lipids can be extracted relatively sufficiently, but a large amount of water-soluble colloidal impurities such as proteins and polysaccharides are also dissolved out, resulting in increased viscosity of the extract, difficult solid-liquid separation, a significantly increased subsequent filtration load, and a relatively high proportion of separable insolubles, thereby affecting product purity and yield. When ethanol of a relatively high concentration is used, the polarity of the extraction system decreases, and the release of amphiphilic phospholipid lipids is not sufficiently complete, resulting in a relatively low total phospholipid content in the product.
[0010] Therefore, there is an urgent need in the art to develop a method that uses a food-grade ethanol aqueous solution as an extraction solvent, has clear and concise process steps and mild operating conditions, can effectively reduce the proportion of separable insolubles before filtration, and can stably obtain high-quality Antarctic krill oil, so as to meet the needs of industrial production of food-grade Antarctic krill oil.
[0011] SUMMARY OF THE INVENTION
[0012] In order to solve the problems in existing Antarctic krill oil preparation technologies that yield and product purity are difficult to balance when ethanol of a single concentration is used for extraction, the high contents of colloidal impurities and separable insolubles in the extract lead to a large subsequent filtration load, and some existing processes have solvent residue risks and cumbersome procedures due to the introduction of non-food-grade organic solvents or complex operations such as shear emulsification, countercurrentDESCRIPTION
[0013] extraction, and salting-out phase separation, the present invention provides a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal. The method uses Antarctic krill powder as the starting material. After low-temperature pulverization and sieving, primary extraction is first carried out with a 75% (v / v) ethanol aqueous solution, and secondary supplementary extraction is then carried out on the primary filter residue with a 90% (v / v) ethanol aqueous solution. The two extracts are combined and allowed to stand away from light at 8°C for impurity removal, followed by centrifugation, membrane filtration, reduced-pressure concentration, and nitrogen-purged desolventizing, so as to finally obtain a food-grade Antarctic krill oil finished product. Through gradient extraction with dual-concentration ethanol, phospholipid-type lipids and weakly polar lipids are sufficiently extracted stepwise, effectively improving product yield and total phospholipid content. Through the low-temperature standing impurity removal step, separable insolubles such as protein colloids and chitinous microparticles form flocculent precipitates and are efficiently removed, thereby significantly reducing the filtration load. Through mild operation throughout the whole process and nitrogen protection, lipid oxidation is effectively controlled, product quality is ensured, and the requirements for industrial production of food-grade Antarctic krill oil can be met.
[0014] To solve the above technical problems, the present invention provides the following technical solution: a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal, wherein the method comprises the following specific steps:DESCRIPTION
[0015] SI 00, taking Antarctic krill powder, placing the same in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder; by subjecting the Antarctic krill powder to low-temperature equilibration and low-temperature pulverization, the krill tissue is embrittled, which is conducive to cell wall rupture, while avoiding oxidative degradation of heat-sensitive components such as phospholipids and astaxanthin caused by frictional heating during pulverization;
[0016] S200, adding a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting under a constant temperature of 25°C for 2 h; after extraction is completed, separating by vacuum filtration to obtain a primary extract and a primary filter residue; and using the high polarity of the 75% (v / v) ethanol aqueous solution to disrupt the binding between phospholipids and proteins or polysaccharides, so that phospholipid-type lipids are fully dissolved into the extract;
[0017] S300, adding a 90% (v / v) ethanol aqueous solution to the primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting under a constant temperature of 35 °C for 2 h; after extraction is completed, separating by vacuum filtration to obtain a secondary extract; and using the low-polarity characteristic of the 90% (v / v) ethanol aqueous solution to effectively penetrate into the residual tissue of the primary filter residue and further extract the weakly polar lipids not yetDESCRIPTION
[0018] released therein, thereby realizing secondary recovery of residual lipids after the primary extraction;
[0019] S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract, and placing the combined extract in an 8°C constant-temperature environment away from light for standing for 8 h; under low-temperature conditions, protein-polysaccharide complexes, fine chitin particles, and other polymeric colloidal impurities originally present in a dissolved or suspended state in the extract gradually form large-particle-size flocculent precipitates, so that they can be efficiently separated and removed in the subsequent centrifugation step;
[0020] S500, transferring the combined extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade filter membrane having a membrane pore size of 0.45 pm to 1.0 pm to obtain a clarified filtrate; by the combined separation manner of centrifugation and membrane filtration, large-particle flocculent precipitates and fine suspended particles are removed successively, thereby ensuring that the feed liquid entering the concentration process has relatively high purity and reducing scaling and heat-transfer deterioration in the subsequent concentration process;
[0021] S600, transferring the clarified filtrate into a rotary evaporator and performing reduced-pressure concentration under light- shielding conditions at 42°C and a vacuum degree of -0.090 MPa until no distillate is generated, so as toDESCRIPTION
[0022] remove ethanol and water and obtain crude krill oil; through reduced-pressure evaporation at a relatively low temperature, ethanol and water are efficiently removed under mild conditions, while the light-shielding conditions protect photosensitive astaxanthin components from photodegradation, thereby retaining natural active substances in the oil to the greatest extent;
[0023] S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 35°C to 45°C for bubbling desolventizing treatment for 20 min to 60 min, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain a food-grade Antarctic krill oil finished product; high-purity nitrogen bubbling desolventizing further removes residual trace solvent and water, while the inert protective atmosphere of nitrogen effectively isolates oxygen, prevents oxidative rancidity of polyunsaturated fatty acids during filling and storage, and ensures oxidative stability of the finished oil.
[0024] Further, in SI 00, the moisture content of the Antarctic krill powder is not higher than 8.0%, and the temperature of the krill raw material powder during low-temperature pulverization is always maintained within the range of -5°C to 0°C. By controlling the moisture content of the raw material and the temperature during pulverization, pulverization efficiency and smooth sieving are ensured, while powder adhesion caused by excessive moisture and accelerated lipid oxidation caused by temperature rise are avoided.
[0025] Further, in S200 and S300, the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa. By controlling the vacuum degree for filtration, solid-liquid separation efficiency is ensured while avoiding turbidity ofDESCRIPTION
[0026] the filtrate caused by fine particles passing through the filter paper due to an excessively high vacuum degree.
[0027] Further, in S500, the food-grade filter membrane is one of a polypropylene membrane, a polytetrafluoroethylene membrane, and a polyethersulfone membrane, and the filtration pressure is controlled at 0.1 MPa to 0.3 MPa.
[0028] Further, in S600, the rotational speed of the rotary evaporator is controlled at 60 r / min to 80 r / min, and the evaporation flask is wrapped with aluminum foil throughout the concentration process to realize light shielding. By controlling the rotational speed, the feed liquid forms a uniform liquid film on the inner wall of the evaporation flask to increase the evaporation area and improve concentration efficiency, and the aluminum foil light- shielding wrapping effectively blocks the damaging effect of external light on the photosensitive active astaxanthin components.
[0029] Further, in S700, the nitrogen flow rate for nitrogen bubbling is controlled at 0.5 L / min to 1.0 L / min. By controlling an appropriate nitrogen flow rate, nitrogen forms uniform and fine bubbles in the crude krill oil, increasing the gas-liquid contact area to promote mass-transfer removal of residual solvent and water, while avoiding oil splashing or product loss caused by entrainment by nitrogen due to an excessively high flow rate.
[0030] Further, n-hexane, petroleum ether, No. 6 solvent oil, cyclohexane, and ethyl acetate are not used as extraction or extractive solvents throughout the method; instead, a food-grade ethanol aqueous solution is used as the only extraction solvent system.
[0031] Further, the method does not include a shear emulsification treatment step,DESCRIPTION
[0032] does not include a countercurrent extraction step, and does not include a salting-out phase separation refining step. By eliminating the above complex additional processes, the operation flow is simplified, equipment investment and production cost are reduced, and excessive oxidation that may be introduced by shear emulsification as well as product loss and wastewater discharge caused by salting-out phase separation are avoided.
[0033] Further, in S700, the food-grade Antarctic krill oil finished product has a total phospholipid content of 40.5% to 43.5%, an eicosapentaenoic acid content of 7.2% to 8.2%, a docosahexaenoic acid content of 3.6% to 4.2%, and a peroxide value not higher than 3.0 meq / kg.
[0034] Compared with the prior art, the method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal has the following beneficial effects:
[0035] — > First, the present invention uses a dual-concentration ethanol system composed of a 75% (v / v) ethanol aqueous solution and a 90% (v / v) ethanol aqueous solution to carry out gradient segmented extraction. Primary extraction is first performed at room temperature with 75% ethanol, and the filter residue is then supplementarily extracted with 90% ethanol, so that the extraction advantages of the two ethanol concentrations synergistically complement each other. The 75% ethanol aqueous solution has relatively high polarity and can efficiently disrupt the binding between phospholipids and proteins or polysaccharides, so that phospholipid-type lipids are fully dissolved into the extract, whereas the 90% ethanol aqueous solution has relatively low polarity and can effectively penetrate into the residual tissue of the primary filter residue toDESCRIPTION
[0036] further extract weakly polar lipids not yet released therein. The design of dual-concentration gradient extraction makes the extraction of total phospholipids, EPA, and DHA more sufficient and balanced, avoids the problems of increased extract viscosity and subsequent filtration difficulty caused by co-dissolution of a large amount of water-soluble colloidal impurities during extraction with ethanol of a single lower concentration, and also avoids the defects of insufficient phospholipid release and relatively low total phospholipid content in the product caused by insufficient system polarity during extraction with ethanol of a single higher concentration.
[0037] Second, after dual-concentration ethanol extraction, the present invention adds a low-temperature standing impurity removal step. The combined extract is placed in an 8°C constant-temperature environment away from light and allowed to stand for 8 h, so that protein-polysaccharide complexes, fine chitin particles, and other polymeric colloidal impurities originally present in a dissolved or suspended state in the extract gradually form large-particle-size flocculent precipitates. As a result, the purity of the feed liquid entering the membrane filtration step is greatly improved, the solid load of membrane filtration is significantly reduced, the service life of the filter membrane is extended, and the risks of membrane contamination and membrane clogging are also reduced.
[0038] Other advantages, objectives, and features of the present invention will be set forth in part in the following description, and in part will be apparent to those skilled in the art upon examination of the following, or may be learned from the practice of the present invention.
[0039] DESCRIPTION OF THE DRAWINGSDESCRIPTION
[0040] In order to more clearly describe the technical solutions in the embodiments of the present invention or in the prior art, the drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art may obtain other drawings according to these drawings without creative effort.
[0041] FIG. 1 is a step block diagram of a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal.
[0042] DETAILED DESCRIPTION
[0043] In order to further describe the technical means adopted by the present invention for achieving the intended inventive purpose and the effects thereof, the specific embodiments, structure, features, and effects of the present invention are described in detail below with reference to the drawings and preferred embodiments.
[0044] In order to improve the problems in existing Antarctic krill oil preparation technologies that yield and purity are difficult to balance when ethanol of a single concentration is used for extraction, the high contents of colloidal impurities and separable insolubles in the extract lead to a large subsequent filtration load, and some existing processes have solvent residue risks and cumbersome procedures due to the introduction of non-food-grade organic solvents or complex operations, the application scenarios involved in the present invention are first described. The present invention is mainly applied in the fields of deep processing of Antarctic krill, preparation of marine functional oils, and industrial production of food-grade Antarctic krill oil. In these scenarios, the traditional preparation method by one-time extraction with ethanol of a single concentration has the defects that, when ethanol of a relatively low concentration is used, a large amount ofDESCRIPTION
[0045] water-soluble colloidal impurities are co-dissolved, resulting in increased extract viscosity, difficult solid-liquid separation, and a proportion of separable insolubles before filtration as high as 0.68%; and when ethanol of a relatively high concentration is used, the insufficient polarity of the system results in insufficient phospholipid release, relatively low total phospholipid content, and unsatisfactory yield. By using a dual-concentration gradient extraction system composed of 75% (v / v) and 90% (v / v) ethanol aqueous solutions, adding an 8 °C low-temperature standing impurity removal step after extraction, and combining mild post-treatment processes of low-temperature reduced-pressure concentration and nitrogen-purged desolventizing, the present invention realizes efficient, stable, and high-quality preparation of food- grade Antarctic krill oil.
[0046] Unified Test Description
[0047] All Antarctic krill oil samples prepared in the examples and comparative examples of the present invention were subjected to performance testing by the following unified methods:
[0048] Yield determination: the yield was calculated as the percentage of the mass of the final Antarctic krill oil finished product to the mass of the starting Antarctic krill powder raw material, namely, the ratio of the mass of the Antarctic krill oil finished product to the mass of the starting Antarctic krill powder.
[0049] Determination of total phospholipid content: the determination was carried out with reference to SN / T 3851-2014, Determination of Phosphatidylcholine, Phosphatidylethanolamine, and Phosphatidylinositol in Export Foods by High-Performance Liquid Chromatography, or an equivalent method, and was expressed as the mass percentage of total phospholipids in the Antarctic krill oil finished product.
[0050] Determination of eicosapentaenoic acid (EPA) content: the gas chromatography method in GB 5009.168-2016, National Food Safety iiDESCRIPTION
[0051] Standard - Determination of Fatty Acids in Foods, was used for determination, and the result was expressed as the mass percentage of EPA in the Antarctic krill oil finished product.
[0052] Determination of docosahexaenoic acid (DHA) content: the gas chromatography method in GB 5009.168-2016, National Food Safety Standard - Determination of Fatty Acids in Foods, was used for determination, and the result was expressed as the mass percentage of DHA in the Antarctic krill oil finished product.
[0053] Determination of peroxide value: the titration method in GB 5009.227-2016, National Food Safety Standard - Determination of Peroxide Value in Foods, was used for determination, and the unit was meq / kg.
[0054] Determination of the proportion of separable insolubles before filtration: the combined extract or primary extract was taken and subjected to centrifugation under exactly the same conditions as those of the subsequent centrifugation step (4000 r / min, centrifugation for 10 min). The resulting separable sediment was collected, dried, and weighed, and converted into the percentage of the mass of the sediment relative to the mass of the starting Antarctic krill powder raw material.
[0055] Example 1
[0056] In this example, Antarctic krill powder having a moisture content of 6.5% was equilibrated at -5°C for 30 min, pulverized, and sieved. A 75% (v / v) ethanol aqueous solution was used for stirring extraction at 100 r / min under a constant temperature of 25 °C for 2 h to obtain a primary extract, and a 90% (v / v) ethanol aqueous solution was then used for supplementary stirring extraction at 100 r / min under a constant temperature of 35 °C for 2 h to obtain a secondary extract. The two extracts were combined and allowed to stand away from light at 8°C for 8 h for low-temperature impurity removal. After centrifugation at 4000 r / min for 10 min and pressure filtration through a 0.8 pm polypropylene membrane, the filtrate was concentrated under reducedDESCRIPTION
[0057] pressure at 42°C and -0.090 MPa away from light, and then subjected to nitrogen bubbling desolventizing at 40°C for 40 min, followed by filling under nitrogen and light-shielding conditions.
[0058] This example provides a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal. As shown in FIG. 1, the method comprises the following specific steps:
[0059] SI 00, taking 100 kg of Antarctic krill powder having a moisture content of 6.5%, placing the powder in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, controlling the temperature of the krill raw material powder to always remain within the range of -5 °C to 0°C during pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0060] S200, adding 500 L of a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 25 °C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0061] S300, adding 500 L of a 90% (v / v) ethanol aqueous solution to the primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting at a stirring speed of 100 r / min under a constant temperature of 35°C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a secondary extract;DESCRIPTION
[0062] S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract, and placing the combined extract in an 8°C constant-temperature environment away from light for standing for 8 h;
[0063] S500, transferring the combined extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polypropylene filter membrane having a membrane pore size of 0.8 pm, with the filtration pressure controlled at 0.2 MPa, to obtain a clarified filtrate;
[0064] S600, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 70 r / min, performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0065] S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 40°C for bubbling desolventizing treatment for 40 min, controlling the nitrogen flow rate at 0.8 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain a food-grade Antarctic krill oil finished product.
[0066] Performance Test Results
[0067] The performance indicators of the food-grade Antarctic krill oil finished product obtained in this example were as follows: yield 8.6%, total phospholipid content 42.1%, EPA content 7.8%, DHA content 3.9%, peroxide value 2.6 meq / kg, and proportion of separable insolubles before filtrationDESCRIPTION
[0068] 0.31%.
[0069] In this example, the dual-concentration gradient extraction manner of primary extraction with 75% (v / v) ethanol and secondary supplementary extraction with 90% (v / v) ethanol enabled the two ethanol concentrations to form a synergistic complementarity. The 75% ethanol efficiently extracted phospholipid-type lipids, and the 90% ethanol fully recovered weakly polar lipids remaining in the filter residue, thereby realizing a stable yield of 8.6% and a high total phospholipid content of 42.1%. By standing at a low temperature of 8 °C for 8 h and using the principle that temperature reduction causes colloidal particles to aggregate and settle, the proportion of separable insolubles before filtration was reduced to 0.31%. Through low-temperature operation below 42°C throughout the whole process, light-shielding protection, and nitrogen atmosphere coverage, oil oxidation was effectively controlled.
[0070] Example 2
[0071] In this example, 20 kg of Antarctic krill powder having a moisture content of 6.8% was equilibrated at -5°C for 30 min, pulverized, and sieved. Under the same process conditions as Example 1, including dual-concentration ethanol extraction, low-temperature standing impurity removal at 8 °C for 8 h, centrifugation at 4000 r / min for 10 min, pressure filtration through a 0.8 pm polypropylene membrane, light-shielded reduced-pressure concentration at 42°C and -0.090 MPa, and nitrogen-purged desolventizing at 40 °C for 40 min, the stability and repeatability of the present invention were verified at a smaller processing scale.
[0072] This example provides a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal, wherein the method comprises the following specific steps:
[0073] SI 00, taking 20 kg of Antarctic krill powder having a moisture content of 6.8%, placing the powder in an environment at -5°C for equilibration for 30DESCRIPTION
[0074] min, then performing low-temperature pulverization, controlling the temperature of the krill raw material powder to always remain within the range of -5 °C to 0°C during pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0075] S200, adding 100 L of a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 25 °C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0076] S300, adding 100 L of a 90% (v / v) ethanol aqueous solution to the primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting at a stirring speed of 100 r / min under a constant temperature of 35°C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a secondary extract;
[0077] S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract, and placing the combined extract in an 8°C constant-temperature environment away from light for standing for 8 h;
[0078] S500, transferring the combined extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polypropylene filter membrane having a membrane pore size of 0.8 pm, with the filtration pressure controlled at 0.2DESCRIPTION
[0079] MPa, to obtain a clarified filtrate;
[0080] S600, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 70 r / min, performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0081] S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 40°C for bubbling desolventizing treatment for 40 min, controlling the nitrogen flow rate at 0.8 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain a food-grade Antarctic krill oil finished product.
[0082] Performance Test Results
[0083] The performance indicators of the food-grade Antarctic krill oil finished product obtained in this example were as follows: yield 8.5%, total phospholipid content 41.8%, EPA content 7.7%, DHA content 3.8%, peroxide value 2.7 meq / kg, and proportion of separable insolubles before filtration 0.33%.
[0084] In this example, under process conditions substantially the same as those of Example 1, only the raw material batch and the processing scale were changed (from a 100 kg scale to a 20 kg scale), and the performance indicators of the resulting product were highly consistent with those of Example 1, indicating that the method of the present invention has good batch stability and scale adaptability and can meet the requirements of different raw material sources and production scales in industrial production.
[0085] Example 3DESCRIPTION
[0086] In this example, 50 kg of Antarctic krill powder having a moisture content of 7.2% was equilibrated at -5°C for 30 min, pulverized, and sieved, and the same dual-concentration ethanol extraction conditions as those in Example 1 were used. However, in step S500, a polytetrafluoroethylene filter membrane having a membrane pore size of 0.45 pm was used and the filtration pressure was controlled at 0.15 MPa; in step S600, the rotational speed of the rotary evaporator was controlled at 60 r / min; and in step S700, the nitrogen-purged desolventizing temperature was controlled at 35 °C, the treatment time was 60 min, and the nitrogen flow rate was controlled at 0.5 L / min. The robustness of the method of the present invention was verified by fine adjustment of some process parameters.
[0087] This example provides a method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal, wherein the method comprises the following specific steps:
[0088] SI 00, taking 50 kg of Antarctic krill powder having a moisture content of 7.2%, placing the powder in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, controlling the temperature of the krill raw material powder to always remain within the range of -5 °C to 0°C during pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0089] S200, adding 250 L of a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 25 °C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0090] S300, adding 250 L of a 90% (v / v) ethanol aqueous solution to theDESCRIPTION
[0091] primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting at a stirring speed of 100 r / min under a constant temperature of 35°C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a secondary extract;
[0092] S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract, and placing the combined extract in an 8°C constant-temperature environment away from light for standing for 8 h;
[0093] S500, transferring the combined extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polytetrafluoroethylene filter membrane having a membrane pore size of 0.45 pm, with the filtration pressure controlled at 0.15 MPa, to obtain a clarified filtrate;
[0094] S600, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 60 r / min, performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0095] S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 35°C for bubbling desolventizing treatment for 60 min, controlling the nitrogen flow rate at 0.5 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performingDESCRIPTION
[0096] aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain a food-grade Antarctic krill oil finished product.
[0097] Performance Test Results
[0098] The performance indicators of the food-grade Antarctic krill oil finished product obtained in this example were as follows: yield 8.4%, total phospholipid content 42.3%, EPA content 7.9%, DHA content 4.0%, peroxide value 2.5 meq / kg, and proportion of separable insolubles before filtration 0.30%.
[0099] In this example, while keeping the dual-concentration gradient extraction, low-temperature standing at 8 °C for 8 h, and reduced-pressure concentration at 42 °C unchanged, operating parameters such as membrane filtration pore size and material, rotary evaporator rotational speed, and nitrogen-purged desolventizing temperature and time were appropriately adjusted. The results show that, when the parameters changed, the product yield and key quality indicators remained stable, demonstrating the operating window and good adaptability of the present invention, which facilitates flexible adjustment in actual production according to equipment conditions and production requirements.
[0100] Comparative Example 1
[0101] In this comparative example, a single 75% (v / v) ethanol aqueous solution was used for one-time extraction (the total solvent amount was the same as in Example 1, namely 1000 L), and secondary supplementary extraction with 90% (v / v) ethanol was not carried out. The remaining steps (low-temperature standing at 8°C for 8 h, centrifugation at 4000 r / min for 10 min, pressure filtration through a 0.8 pm polypropylene membrane, light-shielded reduced-pressure concentration at 42°C and -0.090 MPa, and nitrogen-purged desolventizing at 40°C for 40 min) were exactly the same as those in Example 1, so as to verify the superiority of the dual-concentration gradient extraction of the present invention compared with extraction using ethanol of a singleDESCRIPTION
[0102] low concentration.
[0103] In this comparative example, a single 75% (v / v) ethanol aqueous solution was used for one-time extraction, and secondary supplementary extraction with 90% (v / v) ethanol was not performed. The specific steps were as follows:
[0104] SI 00, taking 100 kg of Antarctic krill powder of the same batch as that in Example 1 and having a moisture content of 6.5%, placing the powder in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0105] S200, adding 1000 L of a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 10 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 25 °C for 4 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0106] S300, transferring the primary extract into a sealed light-shielding container and placing the same in an 8 °C constant-temperature environment away from light for standing for 8 h;
[0107] S400, transferring the extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polypropylene filter membrane having a membrane pore size of 0.8 pm, with the filtration pressure controlled at 0.2 MPa, to obtain a clarified filtrate;
[0108] S500, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 70 r / min, performing reduced-pressure concentration under light-shielding conditions atDESCRIPTION
[0109] 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0110] S600, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 40°C for bubbling desolventizing treatment for 40 min, controlling the nitrogen flow rate at 0.8 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain an Antarctic krill oil finished product.
[0111] Performance Test Results
[0112] The performance indicators of the Antarctic krill oil finished product obtained in this comparative example were as follows: yield 7.8%, total phospholipid content 38.7%, EPA content 6.9%, DHA content 3.4%, peroxide value 3.4 meq / kg, and proportion of separable insolubles before filtration 0.68%.
[0113] In this comparative example, one-time extraction with a single 75% ethanol aqueous solution could effectively extract polar phospholipid lipids. However, because the ethanol concentration in the extraction system was relatively low and the proportion of water was relatively high, water-soluble colloidal impurities such as proteins and polysaccharides were dissolved out at the same time, resulting in increased extract viscosity and difficult solid-liquid separation, and the proportion of separable insolubles before filtration reached 0.68%. Meanwhile, because the total amount of lipids extractable during the one-time extraction process was limited, and some phospholipids were difficult to fully recover due to adsorption and wrapping by colloidal impurities, the product yield was only 7.8% and the total phospholipid content was only 38.7%. A relatively large amount of impuritiesDESCRIPTION
[0114] in the extract promoted oxidation reactions during subsequent concentration and desolventizing, increasing the peroxide value to 3.4 meq / kg, which fully indicates that one-time extraction with ethanol of a single low concentration cannot balance yield, purity, and oxidative stability.
[0115] Comparative Example 2
[0116] In this comparative example, a single 90% (v / v) ethanol aqueous solution was used for one-time extraction (the total solvent amount was the same as in Example 1, namely 1000 L), and primary extraction with 75% (v / v) ethanol was not carried out. The remaining steps (low-temperature standing at 8°C for 8 h, centrifugation at 4000 r / min for 10 min, pressure filtration through a 0.8 pm polypropylene membrane, light-shielded reduced-pressure concentration at 42°C and -0.090 MPa, and nitrogen-purged desolventizing at 40°C for 40 min) were exactly the same as those in Example 1, so as to verify the superiority of the dual-concentration gradient extraction of the present invention compared with extraction using ethanol of a single high concentration.
[0117] In this comparative example, a single 90% (v / v) ethanol aqueous solution was used for one-time extraction, and primary extraction with 75% (v / v) ethanol was not performed. The specific steps were as follows:
[0118] SI 00, taking 100 kg of Antarctic krill powder of the same batch as that in Example 1 and having a moisture content of 6.5%, placing the powder in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0119] S200, adding 1000 L of a 90% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 10 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 35 °C for 4 h; after extraction is completed, separating by vacuum filtration,DESCRIPTION
[0120] wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0121] S300, transferring the primary extract into a sealed light-shielding container and placing the same in an 8 °C constant-temperature environment away from light for standing for 8 h;
[0122] S400, transferring the extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polypropylene filter membrane having a membrane pore size of 0.8 pm, with the filtration pressure controlled at 0.2 MPa, to obtain a clarified filtrate;
[0123] S500, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 70 r / min, performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0124] S600, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 40°C for bubbling desolventizing treatment for 40 min, controlling the nitrogen flow rate at 0.8 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain an Antarctic krill oil finished product.
[0125] Performance Test Results
[0126] The performance indicators of the Antarctic krill oil finished product obtained in this comparative example were as follows: yield 8.0%, totalDESCRIPTION
[0127] phospholipid content 39.2%, EPA content 7.0%, DHA content 3.5%, peroxide value 3.2 meq / kg, and proportion of separable insolubles before filtration 0.60%.
[0128] In this comparative example, one-time extraction with a single 90% ethanol aqueous solution was used. Because the ethanol concentration in the extraction system was relatively high and the polarity was relatively low, the dissolution amount of water-soluble colloidal impurities such as proteins and polysaccharides was significantly lower than that in Comparative Example 1, and the proportion of separable insolubles before filtration was 0.60%. However, phospholipid molecules are amphiphilic, and the solubility of their polar head groups is limited in a high-concentration ethanol environment, resulting in a large amount of phospholipids still being retained in the filter residue and not extracted. The total phospholipid content of the product was only 39.2%, and the yield was only 8.0%. Meanwhile, the relatively high ethanol concentration and extraction temperature aggravated lipid oxidation to a certain extent, and the peroxide value was 3.2 meq / kg, which fully indicates that one-time extraction with ethanol of a single high concentration cannot fully recover phospholipid-type lipids and that the total phospholipid content of the product is difficult to meet high-quality requirements.
[0129] Comparative Example 3
[0130] This comparative example used exactly the same dual-concentration ethanol extraction conditions as Example 1 (primary extraction with 75% ethanol plus secondary supplementary extraction with 90% ethanol), but after combining the extracts, the impurity removal step of standing at 8°C for 8 h was not carried out. Instead, the combined extract was directly subjected to centrifugation at 4000 r / min for 10 min, pressure filtration through a 0.8 pm polypropylene membrane, light-shielded reduced-pressure concentration at 42°C and -0.090 MPa, and nitrogen-purged desolventizing at 40°C for 40 min. The remaining steps were exactly the same as those in Example 1, so as toDESCRIPTION
[0131] verify the effect of the 8 °C low-temperature standing impurity removal step of the present invention in reducing the proportion of separable insolubles before filtration.
[0132] In this comparative example, the 8°C low-temperature standing impurity removal step was not performed, and the specific steps were as follows:
[0133] SI 00, taking 100 kg of Antarctic krill powder of the same batch as that in Example 1 and having a moisture content of 6.5%, placing the powder in an environment at -5°C for equilibration for 30 min, then performing low-temperature pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;
[0134] S200, adding 500 L of a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting at a stirring speed of 100 r / min under a constant temperature of 25 °C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a primary extract and a primary filter residue;
[0135] S300, adding 500 L of a 90% (v / v) ethanol aqueous solution to the primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting at a stirring speed of 100 r / min under a constant temperature of 35°C for 2 h; after extraction is completed, separating by vacuum filtration, wherein the vacuum degree of the vacuum filtration is controlled at -0.06 MPa to -0.08 MPa; and after filtration, obtaining a secondary extract;
[0136] S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract; without standing away from light at 8 °C, directlyDESCRIPTION
[0137] transferring the combined extract into a centrifuge;
[0138] S500, centrifuging the combined extract at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade polypropylene filter membrane having a membrane pore size of 0.8 pm, with the filtration pressure controlled at 0.2 MPa, to obtain a clarified filtrate;
[0139] S600, transferring the clarified filtrate into a rotary evaporator, controlling the rotational speed of the rotary evaporator at 70 r / min, performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa, wrapping the evaporation flask with aluminum foil throughout the concentration process to realize light shielding, and concentrating until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;
[0140] S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 40°C for bubbling desolventizing treatment for 40 min, controlling the nitrogen flow rate at 0.8 L / min, maintaining the pressure in the desolventizing tank in a slightly positive pressure state, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain an Antarctic krill oil finished product.
[0141] Performance Test Results
[0142] The performance indicators of the Antarctic krill oil finished product obtained in this comparative example were as follows: yield 8.5%, total phospholipid content 41.6%, EPA content 7.7%, DHA content 3.8%, peroxide value 2.8 meq / kg, and proportion of separable insolubles before filtration 0.52%.
[0143] The extraction process in this comparative example was exactly the same as that in Example 1, except that the step of standing at 8°C for 8 h for low-temperature impurity removal was omitted after the combined extract wasDESCRIPTION
[0144] obtained. The test results show that, after the low-temperature standing step was omitted, the proportion of separable insolubles before filtration increased from 0.31% in Example 1 to 0.52%. In the extract that had not undergone low-temperature standing, protein-polysaccharide complexes, fine chitin particles, and other polymeric colloidal impurities existed in the form of fine suspended particles and were difficult to sediment effectively during direct centrifugation, increasing the risk of scaling during concentration and being unfavorable to long-term stable operation in industrial production. This fully verifies the effect of the 8 °C low-temperature standing impurity removal step of the present invention in reducing the proportion of insolubles before filtration and reducing the subsequent filtration load.
[0145] In order to intuitively compare the differences in product performance between the examples and the comparative examples of the present invention and clearly show the effects of the core technical features, the performance test results of all samples are summarized in Table 1 below:
[0146] Table 1: Comparison of Performance Test Results of Examples and Comparative Examples
[0147] Separable Total
[0148] EPA DHA Peroxide Insolubles Phospholipid
[0149] Sample Yield Content Content Value Before Content
[0150] No. (%) (%) (%) (meq / kg) Filtration (%)
[0151] (%)
[0152] Ex. 1 8.6 42.1 7.8 3.9 2.6 0.31
[0153] Ex. 2 8.5 41.8 7.7 3.8 2.7 0.33
[0154] Ex. 3 8.4 42.3 7.9 4.0 2.5 0.30
[0155] Comp.
[0156] 7.8 38.7 6.9 3.4 3.4 0.68 Ex. 1
[0157]
[0158] DESCRIPTION
[0159] Comp.
[0160] 8.0 39.2 7.0 3.5 3.2 0.60 Ex. 2
[0161] Comp.
[0162] 8.5 41.6 7.7 3.8 2.8 0.52 Ex. 3
[0163]
[0164] As can be seen from the test results in Table 1, the yields of the Antarctic krill oils prepared in the three examples of the present invention were all stable between 8.4% and 8.6%, the total phospholipid contents were stable between 41.8% and 42.3%, the EPA contents were stable between 7.7% and 7.9%, the DHA contents were stable between 3.8% and 4.0%, the peroxide values were all not higher than 2.7 meq / kg, and the proportions of separable insolubles before filtration were all not higher than 0.33%. The performance indicators of the batches were highly consistent. Compared with single 75% ethanol one-time extraction and single 90% ethanol one-time extraction, dual-concentration ethanol gradient extraction can synergistically exert the extraction advantages of the two ethanol concentrations, increasing the yield from 7.8%-8.0% to 8.5%-8.6% and the total phospholipid content from 38.7%-39.2% to 41.8%-42.3%, while reducing the proportion of separable insolubles before filtration from 0.60%-0.68% to 0.31%-0.33%, thereby achieving comprehensive improvement in yield, purity, and filtration stability. Compared with omitting the 8°C low-temperature standing impurity removal step, under exactly the same extraction process, this step significantly reduced the proportion of separable insolubles before filtration from 0.52% to 0.31%, fully proving that low-temperature standing realizes efficient impurity removal by promoting flocculation and sedimentation of colloidal particles.
[0165] In summary, by means of the combined process of dual-concentration ethanol gradient extraction, 8°C low-temperature standing impurity removal, low-temperature light-shielded reduced-pressure concentration, andDESCRIPTION
[0166] nitrogen-purged desolventizing, the present invention realizes efficient and stable preparation of food-grade Antarctic krill oil throughout the full chain from extraction to finished product.
[0167] The above descriptions are only preferred embodiments of the present invention and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art may make some alterations or modifications to equivalent embodiments by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. Any brief modifications, equivalent changes, and modifications made to the above embodiments according to the technical essence of the present invention without departing from the contents of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
CLAIMS1. A method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal, characterized in that the method comprises the following specific steps:SI 00, taking Antarctic krill powder, placing the same in an environment at -5 °C for equilibration for 30 min, then performing low-temperature pulverization, and after pulverization passing the powder through a 40-mesh standard sieve to obtain krill raw material powder;S200, adding a 75% (v / v) ethanol aqueous solution to the krill raw material powder, wherein the mass-to-volume ratio of the krill raw material powder to the ethanol aqueous solution is 1 kg: 5 L; stirring and extracting at a stirring speed of 80 r / min to 120 r / min under a constant temperature of 25°C for 2 h; and, after extraction is completed, separating by vacuum filtration to obtain a primary extract and a primary filter residue;S300, adding a 90% (v / v) ethanol aqueous solution to the primary filter residue, wherein the added amount of the 90% (v / v) ethanol aqueous solution is 1 kg: 5 L based on the initial mass of the krill raw material powder described in SI 00; stirring and supplementarily extracting at a stirring speed of 80 r / min to 120 r / min under a constant temperature of 35°C for 2 h; and, after extraction is completed, separating by vacuum filtration to obtain a secondary extract;S400, transferring all of the primary extract and the secondary extract into a sealed light-shielding container and mixing uniformly to obtain a combined extract, and placing the combined extract in an 8 °C constant-temperature environment away from light for standing for 8 h;S500, transferring the combined extract after standing into a centrifuge, centrifuging at 4000 r / min for 10 min, collecting an upper clear supernatant after centrifugation and discarding a lower precipitate, and pressure-filtering the supernatant through a food-grade filter membrane having a membrane pore size of 0.45 pm to 1.0 pm to obtain a clarified filtrate;CLAIMSS600, transferring the clarified filtrate into a rotary evaporator and performing reduced-pressure concentration under light-shielding conditions at 42°C and a vacuum degree of -0.090 MPa until no distillate is generated, so as to remove ethanol and water and obtain crude krill oil;S700, transferring the crude krill oil into a sealed desolventizing tank, introducing nitrogen with a purity of >=99.9% at 35°C to 45°C for bubbling desolventizing treatment for 20 min to 60 min, and after desolventizing is completed, performing aseptic filling under continuous nitrogen charging and light-shielding conditions to obtain a food-grade Antarctic krill oil finished product.
2. The method for preparing food- grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in SI 00, the moisture content of the Antarctic krill powder is less than 8.0%, and the material temperature during low-temperature pulverization is always controlled to be less than 0°C.
3. The method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in S200 and S300, the vacuum filtration is carried out by using a Buchner funnel together with qualitative filter paper, and the vacuum degree for filtration is controlled at -0.06 MPa to -0.08 MPa.
4. The method for preparing food- grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in S500, the food-grade filter membrane is one of a polypropylene membrane, a polytetrafluoroethylene membrane, and a polyethersulfone membrane, and the filtration pressure is controlled at 0.1 MPa to 0.3 MPa.
5. The method for preparing food-grade Antarctic krill oil byCLAIMSdual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in S600, the rotational speed of the rotary evaporator is controlled at 60 r / min to 80 r / min, and the evaporation flask is wrapped with aluminum foil throughout the concentration process to realize light shielding.
6. The method for preparing food- grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in S700, the nitrogen flow rate for nitrogen bubbling is controlled at 0.5 L / min to 1.0 L / min, and the pressure in the desolventizing tank is maintained in a slightly positive pressure state.
7. The method for preparing food-grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that n-hexane, petroleum ether, No. 6 solvent oil, cyclohexane, and ethyl acetate are not used as extraction or extractive solvents throughout the method.
8. The method for preparing food- grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that the method does not employ shear emulsification treatment, does not employ a countercurrent extraction device, and does not employ a salting-out phase separation refining step throughout the method.
9. The method for preparing food- grade Antarctic krill oil by dual-concentration ethanol extraction and low-temperature standing impurity removal according to claim 1, characterized in that, in S700, the food-grade Antarctic krill oil finished product has a total phospholipid content of 40.5% to 43.5%, an EPA content of 7.2% to 8.2%, and a DHA content of 3.6% to 4.2%.