A method for extracting low-arsenic krill oil from krill

Abstract

The present application relates to the field of food and chemical technology, and in particular to a method for extracting low-arsenic krill oil from krill, comprising (1) preparing a microemulsion system; (2) microemulsion cold extraction; (3) selective chelation and arsenic removal; (4) separation and purification; (5) quality stabilization; the selective affinity of the microemulsion system for lipids is strong, and the extraction rate is increased by 30-40% compared with the traditional solvent method; the selective chelation technology can reduce the arsenic content to below 0.1 mg / kg, which is much lower than the international standard limit (1 mg / kg); the whole process is operated at low temperature, and the retention rate of EPA and DHA is above 95%; biocompatible materials and green solvents - ethanol are used, thereby reducing the environmental impact; the microemulsion system has high stability, and the process is simple and easy to scale up.

Description

Technical Field

[0001] This invention relates to the fields of food and chemical technology, and in particular to a method for extracting low-arsenic krill oil from krill. Background Technology

[0002] Krill are small crustaceans that live in the world's oceans, with Antarctic krill being the most abundant and known as the "ruby of the sea." Krill oil is an important marine biological resource extracted from krill. It is characterized by its high content of omega-3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These components have important physiological activities in maintaining cardiovascular health, lowering blood lipids, anti-inflammatory and antioxidant effects, and improving cognitive function. Compared with traditional fish oil, the omega-3 fatty acids in krill oil are mainly in the form of phospholipids, resulting in higher bioavailability and less fishy or off-flavors, making it promising for applications and possessing high economic value in the food, health product, and pharmaceutical fields. With increasing health awareness and growing demand for the high-value utilization of marine biological resources, the development and utilization of krill oil has received increasing attention.

[0003] Currently, industrial extraction methods for krill oil mainly include traditional organic solvent extraction, enzyme-assisted extraction, supercritical CO2 extraction, and physical extrusion. Traditional organic solvent extraction uses solvents such as hexane and acetone. While the process is mature, it suffers from solvent residue risks, low efficiency, and environmental pollution. Enzyme-assisted extraction improves extraction efficiency, but enzyme preparations are expensive and reaction conditions require strict control. Supercritical CO2 extraction is environmentally friendly and efficient, but requires large equipment investments, complex operation, and high energy consumption. Physical extrusion is simple and direct, but has a low extraction rate and unstable product quality. Meanwhile, krill generally contains high concentrations of arsenic, which may enter the final product during oil extraction, affecting product safety and market acceptance. Current arsenic removal methods include activated carbon adsorption, chelation exchange, and membrane separation. However, these methods often suffer from incomplete arsenic removal, loss of active ingredients, complex processes, or high costs, making it difficult to simultaneously guarantee high arsenic removal rates and high quality.

[0004] The research and application of krill oil extraction and arsenic removal technologies face multiple challenges: On the one hand, existing extraction technologies struggle to balance extraction efficiency, product quality, and environmental friendliness, especially in achieving high-efficiency extraction while maintaining the integrity of ω-3 fatty acids; on the other hand, selectively removing toxic arsenic compounds without affecting the retention of beneficial components during arsenic removal is a major technical challenge. Furthermore, most existing technologies require high-temperature processing, which may lead to the oxidation or isomerization of unsaturated fatty acids, reducing product quality; and while some methods are effective, their complex equipment and processes make large-scale industrial production difficult. Therefore, developing a krill oil extraction and purification technology that can efficiently extract, deeply remove arsenic, fully retain nutrients, and is easily industrialized is of significant scientific and practical value for improving krill resource utilization, ensuring product quality and safety, and promoting the sustainable development of marine biological resources. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a method for extracting low-arsenic krill oil from krill, comprising the following steps:

[0006] (1) Preparation of microemulsion system: Biocompatible surfactant, auxiliary surfactant, ethanol and pure water are mixed in a predetermined ratio to form a transparent and uniform microemulsion system;

[0007] (2) Microemulsion cold extraction: The pretreated krill powder was mixed with the microemulsion system at a low temperature of 4-10℃ and extracted with ultrasound under nitrogen protection. The oil phase was then collected by temperature jump and centrifugation.

[0008] (3) Selective chelation to remove arsenic: A composite chelating agent composed of thiolated chitosan and tea polyphenols was prepared and reacted with the oil phase obtained in step (2) under weakly alkaline conditions. A trace amount of metal ions was added as a competitive substitute to complete the selective chelation of arsenic in the oil phase.

[0009] (4) Separation and purification: The chelated arsenic compounds were separated by ultrafiltration membrane, and further purified by column chromatography. The purified product was obtained by slow cooling crystallization.

[0010] (5) Quality stabilization: Microencapsulated antioxidants and molecular encapsulating agents are added to the purified product and vacuum-sealed under nitrogen protection.

[0011] Furthermore, the biocompatible surfactant is selected from phospholipids, polysorbate 80, or combinations thereof; the auxiliary surfactant is a medium-chain triglyceride; and the mass ratio of the biocompatible surfactant to the auxiliary surfactant is 1:1 to 1:3.

[0012] Furthermore, the ultrasound-assisted extraction employs an alternating pulse mode of 20-40 kHz with a power density of 30-40 W / cm². 2The extraction time is 20-60 minutes.

[0013] Furthermore, the temperature jump involves heating the mixture from 4-10°C to 20-30°C to trigger a microemulsion phase transition, followed by centrifugation at 4000-6000 rpm for 8-12 minutes.

[0014] Furthermore, the preparation method of thiolated chitosan is as follows: chitosan is dissolved in 1-2% acetic acid solution, mercaptoacetic acid and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) are added as condensing agents, the reaction is carried out for 3-5 hours, and after dialysis purification, it is freeze-dried.

[0015] Furthermore, the extraction method for tea polyphenols is as follows: using 50-70% ethanol or a mixed solvent of ethanol and propylene glycol, extract from green tea for 1-3 hours at 40-60℃, filter, concentrate, and then freeze-dry.

[0016] Furthermore, the mass ratio of thiolated chitosan to tea polyphenols in the composite chelating agent is 2:1 to 5:1; the trace metal ion is Zn. 2+ or Zn 2+ With Mg 2+ The combination of the ingredients has a concentration of 0.03-0.07%; the pH value is 7.5-8.5 under weakly alkaline conditions; the chelation reaction is carried out at 15-20℃ for 30-60 minutes.

[0017] Furthermore, the ultrafiltration membrane has a molecular weight cutoff of 8-12 kDa; the column chromatography uses silica gel as the stationary phase and a mixed solvent of n-hexane and ethyl acetate as the eluent; the cooling rate for slow cooling crystallization is 0.3-0.7 °C / min.

[0018] Furthermore, the microencapsulated antioxidant is prepared by spray drying of a mixture of rosemary extract, green tea polyphenols and vitamin E in a mass ratio of 1:1:1 to 1:3:1, with maltodextrin as the wall material, at a concentration of 0.03-0.07% (w / w); the molecular encapsulating agent is a β-cyclodextrin derivative at a concentration of 0.05-0.15% (w / w).

[0019] Furthermore, the yield is 12-15g / 100g krill meal, the arsenic content is less than 0.1mg / kg, the EPA content is 16-18% (accounting for total fatty acids), the DHA content is 9-11% (accounting for total fatty acids), the peroxide value is less than 0.7meq / kg, and the acid value is less than 0.5mgKOH / g.

[0020] The technical solution adopted in this invention includes the following steps:

[0021] Phase 1: Microemulsion Cold Extraction System

[0022] Preparation of microemulsion formulations:

[0023] The biocompatible surfactants (phospholipids, polysorbate 80) and the auxiliary surfactants (medium-chain triglycerides) were mixed in a 1:2 ratio.

[0024] Adding appropriate amounts of ethanol and pure water forms a transparent and homogeneous microemulsion system.

[0025] Low-temperature extraction process:

[0026] The krill samples were freeze-dried and ground to 100-200 mesh.

[0027] At 4°C, the microemulsion system was mixed with krill powder at a ratio of 10:1 (v / w).

[0028] Under nitrogen protection, ultrasonic treatment was performed for 30 minutes using an alternating pulse mode of 20-40 kHz, with the power density controlled at 30-40 W / cm². 2 ;

[0029] Phase separation and preliminary purification:

[0030] The mixture was heated from 4°C to 25°C to trigger a microemulsion phase transition.

[0031] Centrifuge at 5000 rpm for 10 minutes and collect the upper oil phase;

[0032] Repeat the temperature jump-centrifugation process twice to improve the extraction rate;

[0033] Phase Two: Selective Chelation Arsenic Removal Treatment

[0034] Chelating agent preparation:

[0035] Preparation of thiolized chitosan: Chitosan was dissolved in 1% acetic acid solution, mercaptoacetic acid was added, and EDC was used as a condensing agent. The reaction was carried out for 4 hours.

[0036] Extraction of tea polyphenols: Tea polyphenols were extracted from green tea using a 70% ethanol aqueous solution;

[0037] A composite chelating agent is prepared by mixing thiolized chitosan and tea polyphenols in a 3:1 ratio.

[0038] Chelation and arsenic removal process:

[0039] Adjust the pH of the oil phase obtained in the first stage to 7.8-8.2;

[0040] Add 0.05% zinc ions (ZnCl2);

[0041] At 15-20℃, add the chelating agent and mix with the oil phase, and react for 45 minutes;

[0042] Separation and purification:

[0043] S uses an ultrafiltration membrane with a molecular weight cutoff of 10 kDa to separate the chelated arsenic compounds;

[0044] Further purification was performed using silica gel column chromatography with hexane:ethyl acetate (95:5) as the eluent.

[0045] The purified oil phase was cooled from room temperature to 4°C at a rate of 0.5°C / min for crystallization purification.

[0046] Phase 3: Quality Stabilization Treatment

[0047] Antioxidant protection:

[0048] Mix rosemary extract, green tea polyphenols, and vitamin E in a 1:2:1 ratio;

[0049] Microencapsulated antioxidants were prepared using maltodextrin as the wall material.

[0050] Microencapsulated antioxidants were added to the oil phase at a concentration of 0.05% (w / w).

[0051] Product packaging:

[0052] Add β-cyclodextrin derivative at a concentration of 0.1% (w / w);

[0053] Vacuum-sealed under nitrogen protection and stored at 4°C;

[0054] The beneficial effects of this invention are:

[0055] Microemulsion systems exhibit strong selective affinity for lipids, increasing extraction rates by 30-40% compared to traditional solvent methods. Selective chelation technology can reduce arsenic content to below 0.1 mg / kg, far below the international standard limit (1 mg / kg). The entire process is conducted at low temperatures, achieving EPA and DHA retention rates of over 95%. The use of biocompatible materials and the green solvent ethanol minimizes environmental impact. Microemulsion systems also demonstrate high stability, simple processing, and ease of scale-up production. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a schematic diagram of the microemulsion cold extraction and selective chelation arsenic removal process according to an embodiment of the present invention;

[0058] Figure 2 This is a schematic diagram comparing the performance of microemulsion cold extraction with traditional methods in an embodiment of the present invention. Detailed Implementation

[0059] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0060] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0061] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0062] See Figure 1

[0063] Example 1: Krill oil extraction and arsenic removal under basic process parameters

[0064] 1.1 Preparation of Microemulsion Formulation

[0065] Phospholipids and polysorbate 80 are mixed in a 1:1 ratio, with a total amount of 5g.

[0066] 10g of medium-chain triglycerides

[0067] 20 mL of anhydrous ethanol

[0068] 65mL of pure water

[0069] The above components are mixed under magnetic stirring to form a transparent microemulsion system for later use.

[0070] 1.2 Krill Sample Pretreatment

[0071] 500g of Antarctic krill (Euphausia superba) was freeze-dried and then pulverized to 150 mesh. The arsenic content of the raw material was determined to be 5.2mg / kg.

[0072] 1.3 Cold extraction of microemulsions

[0073] Weigh 100g of processed krill powder and add it to 1000mL of microemulsion.

[0074] Mixing at 4°C under nitrogen protection

[0075] The treatment was performed using 30kHz ultrasound for 30 minutes at a power density of 35W / cm². 2

[0076] Heat the mixture to 25°C and let it stand for 15 minutes.

[0077] Centrifuge at 5000 rpm for 10 minutes and collect the upper oil phase.

[0078] Repeat the temperature jump-centrifugation process twice.

[0079] 1.4 Preparation of chelating agents

[0080] Preparation of thiolated chitosan: 2g chitosan was dissolved in 100mL of 1% acetic acid solution.

[0081] Add 1g of mercaptoacetic acid and 0.5g of EDC.

[0082] React at room temperature for 4 hours, dialyze for 48 hours, and freeze-dry.

[0083] Tea polyphenol extraction:

[0084] Add 10g of green tea powder to 100mL of 70% ethanol

[0085] Extraction in a 50℃ water bath for 1 hour

[0086] Filtration, vacuum concentration, freeze drying

[0087] Mix thiolized chitosan and tea polyphenol powder in a 3:1 ratio.

[0088] 1.5 Selective chelation arsenic removal

[0089] Take the oil phase obtained in step 1.3 and adjust the pH to 8.0.

[0090] Add 0.05% ZnCl2 solution

[0091] The composite chelating agent prepared in step 1.4 was added at a concentration of 1% (w / w).

[0092] The reaction was carried out at 18°C ​​for 45 minutes.

[0093] 1.6 Separation and Purification

[0094] The chelate products were separated using a 10 kDa ultrafiltration membrane.

[0095] Purification by silica gel column chromatography: eluent was n-hexane:ethyl acetate (95:5).

[0096] Crystallization by cooling at a rate of 0.5℃ / min

[0097] 1.7 Quality Stabilization

[0098] Mix rosemary extract, green tea polyphenols, and vitamin E in a 1:2:1 ratio.

[0099] Microencapsulated antioxidants were prepared using a spray drying method.

[0100] Microencapsulated antioxidant (0.05%, w / w) and β-cyclodextrin derivative (0.1%, w / w) were added and vacuum-sealed under nitrogen protection.

[0101] 1.8 Results Analysis

[0102] Product yield: 12.8g krill oil / 100g krill powder

[0103] Arsenic content: 0.09 mg / kg; EPA content: 16.2% (of total fatty acids)

[0104] DHA content: 9.8% (of total fatty acids)

[0105] Peroxide value: 0.6 meq / kg

[0106] Acid value: 0.4 mg KOH / g

[0107] Example 2: Krill oil extraction and arsenic removal using optimized microemulsion formulation

[0108] 2.1 Microemulsion Formulation Optimization

[0109] Phospholipids and polysorbate 80 were mixed in a 1:2 ratio, with a total amount of 6g.

[0110] 12g of medium-chain triglycerides

[0111] 15 mL of anhydrous ethanol

[0112] 67mL of pure water

[0113] 2.2 Krill Sample Pretreatment

[0114] Same as Example 1.

[0115] 2.3 Cold extraction of microemulsions

[0116] The basic steps are the same as in Example 1.

[0117] Adjust ultrasound parameters: Use an alternating pulse mode of 20-40kHz, switching frequencies every 5 seconds, and extend the extraction time to 40 minutes.

[0118] 2.4 Chelating Agent Optimization

[0119] The preparation method of thiolized chitosan is the same as in Example 1.

[0120] Improvements to tea polyphenol extraction methods:

[0121] Extraction was performed using a mixed solvent of 50% ethanol and 50% propylene glycol.

[0122] The extraction temperature was reduced to 40℃, and the extraction time was extended to 2 hours.

[0123] Mix thiolized chitosan and tea polyphenol powder in a 4:1 ratio.

[0124] 2.5-2.7 The remaining steps

[0125] Same as Example 1.

[0126] 2.8 Results Analysis

[0127] Product yield: 14.5g krill oil / 100g krill powder

[0128] Arsenic content: 0.06 mg / kg

[0129] EPA content: 16.8% (of total fatty acids)

[0130] DHA content: 10.2% (of total fatty acids)

[0131] Peroxide value: 0.5 meq / kg

[0132] Acid value: 0.3 mg KOH / g

[0133] Example 3: Low-temperature extended arsenic removal process

[0134] Steps 3.1-3.4

[0135] Same as Example 2.

[0136] 3.5 Optimization of Selective Chelation Dearsenic Removal

[0137] Take the oil phase obtained in step 2.3 of Example 2 and adjust the pH to 7.8.

[0138] Add 0.03% ZnCl2 solution and 0.02% MgCl2 solution.

[0139] The composite chelating agent prepared in step 2.4 of Example 2 was added, increasing the concentration to 1.5% (w / w).

[0140] The reaction was carried out at 15°C for 60 minutes.

[0141] 3.6-3.7 The remaining steps

[0142] Same as Example 2.

[0143] 3.8 Results Analysis

[0144] Product yield: 14.2g krill oil / 100g krill powder

[0145] Arsenic content: 0.04 mg / kg

[0146] EPA content: 17.1% (of total fatty acids)

[0147] DHA content: 10.5% (of total fatty acids)

[0148] Peroxide value: 0.4 meq / kg

[0149] Acid value: 0.3 mg KOH / g

[0150] Comparative Example

[0151] See Figure 2

[0152] Comparative Example 1: Traditional Hexane Extraction Method

[0153] Process steps

[0154] Take 100g of pretreated krill powder, add 500mL of n-hexane, and extract at room temperature with stirring for 2 hours.

[0155] Filtration, collection of filtrate

[0156] Extract twice

[0157] Combine the filtrates and recover the solvent by rotary evaporation.

[0158] Arsenic removal using activated carbon: Add 5% activated carbon, stir at room temperature for 2 hours, filter, and collect the filtrate.

[0159] Add 0.05% antioxidant (vitamin E)

[0160] Results Analysis

[0161] Product yield: 9.6g krill oil / 100g krill powder

[0162] Arsenic content: 0.85 mg / kg

[0163] EPA content: 12.8% (of total fatty acids)

[0164] DHA content: 7.6% (of total fatty acids)

[0165] Peroxide value: 2.8 meq / kg

[0166] Acid value: 1.2 mg KOH / g

[0167] Comparative Example 2: Supercritical CO2 Extraction Method

[0168] Process steps

[0169] Take 100g of pretreated krill powder and put it into the extraction tank.

[0170] Supercritical CO2 extraction conditions: 35 MPa, 50℃

[0171] Extraction time: 2 hours

[0172] Arsenic removal by adsorption using modified silica gel: through a column packed with modified silica gel.

[0173] Collect the product and add 0.05% of a mixed antioxidant (vitamin E and rosmarinic acid).

[0174] Results Analysis

[0175] Product yield: 11.2g krill oil / 100g krill powder

[0176] Arsenic content: 0.38 mg / kg

[0177] EPA content: 15.3% (of total fatty acids)

[0178] DHA content: 9.1% (of total fatty acids)

[0179] Peroxide value: 1.2 meq / kg

[0180] Acid value: 0.6 mg KOH / g.

[0181] The key metrics of the three embodiments of the present invention are compared with those of the two comparative examples, and the results are shown in the table below:

[0182] index Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Yield (g / 100g krill meal) 12.8 14.5 14.2 9.6 11.2 Arsenic content (mg / kg) 0.09 0.06 0.04 0.85 0.38 EPA content (%) 16.2 16.8 17.1 12.8 15.3 DHA content (%) 9.8 10.2 10.5 7.6 9.1 Peroxide value (meq / kg) 0.6 0.5 0.4 2.8 1.2 Acid value (mgKOH / g) 0.4 0.3 0.3 1.2 0.6

[0183] As can be seen from the table above, the microemulsion cold extraction and selective chelation arsenic removal process provided by this invention has significant advantages over traditional methods:

[0184] Extraction efficiency: Example 2 of the present invention achieved a yield of 14.5 g / 100 g, which is 51.0% higher than that of the conventional hexane extraction method (Comparative Example 1) and 29.5% higher than that of the supercritical CO2 extraction method (Comparative Example 2).

[0185] Arsenic content: Example 3 of the present invention showed the best arsenic removal effect, with an arsenic residue of only 0.04 mg / kg, which is 95.3% lower than Comparative Example 1 and 89.5% lower than Comparative Example 2, and far below the arsenic limit standard (1 mg / kg) for aquatic oils set by the Codex Alimentarius Commission.

[0186] EPA and DHA content: The EPA and DHA contents of Examples 1-3 of the present invention are all higher than those of Comparative Examples 1-2, indicating that the process of the present invention has a better protective effect on unsaturated fatty acids. In Example 3, the EPA and DHA contents reached 17.1% and 10.5%, respectively, which are 33.6% and 38.2% higher than those of Comparative Example 1, respectively.

[0187] Oxidative stability: The peroxide value and acid value of the product obtained by the process of this invention are significantly lower than those of the comparative example, indicating that the product has a low degree of oxidation and good stability. The peroxide value of Example 3 is 0.4 meq / kg, which is only 14.3% of that of Comparative Example 1.

[0188] This invention provides a krill oil extraction and purification process based on microemulsion cold extraction combined with selective chelation arsenic removal. By innovatively combining a temperature-sensitive microemulsion system with a bifunctional chelation system, it successfully solves the problems of low extraction efficiency, incomplete arsenic removal, and significant nutrient loss associated with traditional processes. This process not only improves the yield of krill oil and significantly reduces arsenic content, but also retains EPA and DHA, among other effective components, to the greatest extent possible, while the product exhibits excellent oxidative stability.

[0189] Furthermore, the process of this invention uses biocompatible materials and green solvents, avoiding the use of toxic and harmful substances, which aligns with the principles of green chemistry; the entire process operates at low temperatures, resulting in low energy consumption; and the process steps are simple, facilitating industrial-scale production. These characteristics give this invention broad application prospects in the field of high-value utilization of krill resources.

[0190] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0191] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for extracting low-arsenic krill oil from krill, characterized in that, Includes the following steps: (1) Preparation of microemulsion system: Biocompatible surfactant, auxiliary surfactant, ethanol and pure water are mixed in a predetermined ratio to form a transparent and uniform microemulsion system; (2) Microemulsion cold extraction: The pretreated krill powder was mixed with the microemulsion system at a low temperature of 4-10℃ and extracted with ultrasonic assistance under nitrogen protection. The oil phase was then collected by temperature jump and centrifugation. (3) Selective chelation to remove arsenic: A composite chelating agent composed of thiolated chitosan and tea polyphenols was prepared and reacted with the oil phase obtained in step (2) under weakly alkaline conditions. A trace amount of metal ions was added as a competitive substitute to complete the selective chelation of arsenic in the oil phase. (4) Separation and purification: The chelated arsenic compounds were separated by ultrafiltration membrane, and further purified by column chromatography. The purified product was obtained by slow cooling crystallization. (5) Quality stabilization: Microencapsulated antioxidants and molecular encapsulating agents are added to the purified product and vacuum-sealed under nitrogen protection.

2. The method according to claim 1, characterized in that, The biocompatible surfactant is selected from phospholipids, polysorbate 80, or combinations thereof; the auxiliary surfactant is a medium-chain triglyceride; the mass ratio of the biocompatible surfactant to the auxiliary surfactant is 1:1 to 1:

3.

3. The method according to claim 1, characterized in that, The ultrasonic-assisted extraction employs an alternating pulse mode of 20-40 kHz and a power density of 30-40 W / cm². 2 The extraction time is 20-60 minutes.

4. The method according to claim 1, characterized in that, The temperature jump is achieved by raising the mixture from 4-10°C to 20-30°C to trigger a microemulsion phase transition, followed by centrifugation at 4000-6000 rpm for 8-12 minutes.

5. The method according to claim 1, characterized in that, The preparation method of the thiolized chitosan is as follows: chitosan is dissolved in 1-2% acetic acid solution, mercaptoacetic acid and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) are added as condensing agents, the reaction is carried out for 3-5 hours, and after dialysis purification, it is freeze-dried.

6. The method according to claim 1, characterized in that, The extraction method of the tea polyphenols is as follows: using 50-70% ethanol or a mixed solvent of ethanol and propylene glycol, extract from green tea for 1-3 hours at 40-60℃, filter, concentrate, and then freeze-dry.

7. The method according to claim 1, characterized in that, The mass ratio of thiolized chitosan to tea polyphenols in the composite chelating agent is 2:1 to 5:1; the trace metal ions are Zn2+ or a combination of Zn2+ and Mg2+, with a concentration of 0.03-0.07%; the pH value under the weakly alkaline conditions is 7.5-8.5; the chelation reaction is carried out at 15-20℃ for 30-60 minutes.

8. The method according to claim 1, characterized in that, The ultrafiltration membrane has a molecular weight cutoff of 8-12 kDa; the column chromatography uses silica gel as the stationary phase and a mixed solvent of n-hexane and ethyl acetate as the eluent; the cooling rate of the slow cooling crystallization is 0.3-0.7 °C / min.

9. The method according to claim 1, characterized in that, The microencapsulated antioxidant is prepared by spray drying of a mixture of rosemary extract, green tea polyphenols and vitamin E in a mass ratio of 1:1:1 to 1:3:1, with maltodextrin as the wall material, at a concentration of 0.03-0.07% (w / w); the molecular encapsulating agent is a β-cyclodextrin derivative at a concentration of 0.05-0.15% (w / w).

10. The krill oil prepared by the method according to any one of claims 1-9, characterized in that: The yield is 12-15g / 100g krill powder, the arsenic content is less than 0.1mg / kg, the EPA content is 16-18% of the total fatty acids, the DHA content is 9-11% of the total fatty acids, the peroxide value is less than 0.7meq / kg, and the acid value is less than 0.5mgKOH / g.

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