Deodorized high-purity euphausia superba oil and encapsulation preparation method thereof

Abstract

The invention relates to the technical field of fishy smell removal treatment, in particular to a preparation method of fishy smell removed high-purity euphausia superba oil and an encapsulation preparation method of the fishy smell removed high-purity euphausia superba oil. The method comprises the following steps: firstly, carrying out antioxidant pretreatment on krill oil under the protection of nitrogen, and adding natural vitamin E and ascorbyl palmitate; removing fishy smell by adopting a series fixed bed system, filling a bifunctional silicon dioxide adsorbent and a gamma-cyclodextrin metal organic framework adsorbent in a specific sequence, adding chitosan-gallic acid / carboxyl betaine double-grafted microgel slurry at an outlet of a fixed bed 2, shearing, standing and filtering, and continuously passing through a subsequent bed layer. According to the method, fishy smell substances can be efficiently removed, nutritional ingredients such as phospholipid, EPA and DHA can be remarkably reserved, the peroxide value and the anisidine value are reduced, the product oxidation stability is high, the capsule dissolution behavior is stable, and the method is suitable for production of high-quality health care products.

Description

Technical Field

[0001] This invention relates to the field of deodorization technology, and in particular to a deodorized high-purity Antarctic krill oil and its encapsulation preparation method. Background Technology

[0002] Antarctic krill oil, a high-value functional oil, is rich in Omega-3 fatty acids (such as EPA and DHA) in the form of phospholipids, and its bioavailability has attracted much attention. However, its strong, distinctive fishy odor is a core obstacle restricting the product's market acceptance and high-end applications. This fishy odor is not caused by a single substance, but is the result of the complex interaction of multiple volatile compounds, mainly including volatile amines such as trimethylamine, small molecules of aldehydes and ketones produced by fat oxidation, and some free peptides. These substances have significant differences in molecular weight, polarity, and chemical activity, posing a great challenge to the deodorization process.

[0003] Currently used industrial deodorization methods, such as physical adsorption and high-temperature deodorization, have significant limitations when processing krill oil. Physical adsorption methods often employ broad-spectrum adsorbents such as activated carbon and silica gel, which, while capable of adsorbing some odor substances, lack sufficient selectivity. Phospholipid molecules are also polar and compete with small odor molecules for adsorption sites, resulting in the removal of large amounts of valuable phospholipids along with core nutrients such as EPA and DHA during the deodorization process. This leads to a significant decrease in product yield and the content of functional components.

[0004] High-temperature deodorization processes remove volatile components through steam distillation, which is effective for certain oils. However, the phospholipids and natural antioxidants in krill oil are extremely sensitive to heat. High-temperature treatment easily induces and accelerates oxidative rancidity of the oil, leading to increased peroxide values ​​and potentially generating new off-odor substances, thus deteriorating the overall stability of the oil. More importantly, high temperatures can damage the structure of phospholipids, affecting their functional activity, which contradicts the original intention of preserving the nutritional advantages of krill oil.

[0005] Furthermore, even with a multi-stage adsorption bed series process, ideal results are difficult to achieve without a precise design of the adsorbent characteristics and bed sequence. In existing technologies, the simple stacking of different adsorption beds often ignores the differences in adsorption kinetics among the odor components. If the bed sequence is not properly arranged, such as treating beds with excessive polarity or insufficient adsorption capacity first, the adsorbent in the first stage will quickly become saturated, causing subsequent beds to face high loads prematurely, resulting in penetration and a significant reduction in overall deodorization efficiency. Simultaneously, the repeated flow and contact of oils between multiple solid-phase interfaces is itself a potential oxidation-induced process, posing a threat to the long-term stability of the product.

[0006] In the productization stage, the encapsulation effect of the capsules directly impacts the user experience. If the deodorization is incomplete, residual fishy substances will gradually migrate through the gelatin shell during storage, causing the fishy smell to rebound. Simultaneously, poor compatibility between the oil core and the gelatin shell may lead to unstable capsule dissolution behavior, affecting the release of active ingredients. Current technologies struggle to achieve an ideal balance between deep deodorization, maximizing nutrient retention, ensuring oxidative stability, and guaranteeing the quality of the final product.

[0007] Therefore, developing a new method that can systematically solve the above-mentioned multidimensional problems has become a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] In view of this, the purpose of this invention is to propose a deodorized high-purity Antarctic krill oil and its encapsulation preparation method, so as to solve the problems of poor selectivity, easy oxidation and insufficient multi-level adsorption synergy of existing deodorization technology, which leads to serious loss of nutrients, decreased oxidation stability and unsustainable and incomplete deodorization effect of krill oil during the deodorization process.

[0009] To achieve the above objectives, the present invention provides a method for preparing deodorized high-purity Antarctic krill oil, comprising the following steps:

[0010] (1) Antioxidant pretreatment: Under nitrogen protection, natural vitamin E and ascorbate palmitate were added to the krill oil raw material, stirred at 25°C for 10 min, stirred at 50°C for 10 min and then cooled to obtain pretreated oil;

[0011] (2) Deodorization of the series system: The pretreated oil is fed through fixed bed 1 and fixed bed 2 in sequence at a feed rate of 800-1200g / h; microgel slurry is added at the outlet of fixed bed 2, sheared and dispersed for 3min and allowed to stand for 10-15min, and then filtered through a 10μm filter element and discharged through fixed bed 3, fixed bed 4 and fixed bed 5 in sequence.

[0012] Among them, fixed beds 1, fixed beds 3 and fixed beds 5 are filled with bifunctional silica adsorbents, and fixed beds 2 and fixed beds 4 are filled with γ-cyclodextrin metal-organic framework adsorbents.

[0013] The microgel slurry is composed of 30-70g of chitosan-gallic acid / carboxybetaine double-grafted microgel and 30-70g of ethanol; the system operates under nitrogen headspace protection.

[0014] Preferably, the amount of natural vitamin E added per 10,000g of krill oil raw material is 4-8g, and the amount of ascorbate palmitate added is 0.5-1.5g.

[0015] Preferably, the filling amount of the fixed beds is as follows per 10,000g of feed: 720-880g for fixed bed 1, 360-440g for fixed bed 2, 270-330g for fixed bed 3, 180-220g for fixed bed 4, and 90-110g for fixed bed 5.

[0016] Preferably, the preparation of the bifunctional silica adsorbent includes: treating the outer surface of a porous silica carrier with octyltriethoxysilane to form an oleophobic layer; first introducing 3-mercaptopropyltrimethoxysilane into the pores, then oxidizing it with 30wt% hydrogen peroxide, followed by reacting it with 3-(trihydroxysilyl)propylmethylphosphonic acid monosodium salt to introduce phosphonic acid groups, and then drying and prehydrating to obtain the adsorbent.

[0017] Preferably, the weight ratio of the porous silica carrier, octyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-(trihydroxysilyl)propylmethylphosphonic acid monosodium salt is 10:1:2:2.

[0018] Preferably, the chitosan-gallic acid / carboxybetaine double-grafted microgel is formed by in-situ grafting of chitosan and gallic acid with acylation grafted under the action of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride / N-hydroxysuccinimide (EDC / NHS), followed by grafting polymerization with carboxybetaine methacrylate under the initiation of ammonium persulfate and crosslinking with N,N′-methylenebisacrylamide. Finally, it is neutralized to pH 6.8-7.0 and freeze-dried.

[0019] Preferably, the weight ratio of chitosan, gallic acid, carboxybetaine methacrylate, and N,N′-methylenebisacrylamide is 100:30:15:1.

[0020] Preferably, the γ-cyclodextrin metal-organic framework adsorbent is obtained by adding ethanol dropwise to an aqueous solution of γ-cyclodextrin containing potassium hydroxide, allowing it to stand at 25°C for 24 hours to crystallize, washing with ethanol and vacuum drying at 45°C, and then pre-wetting with an aqueous solution containing glycerol.

[0021] Preferably, the weight ratio of potassium hydroxide to γ-cyclodextrin is 3:50.

[0022] Preferably, the heights of the fixed beds 1-5 are 270-330mm, 243-297mm, 180-220mm, 144-176mm and 180-220mm respectively, the column spacing is 300mm and the column inner diameter is 60mm.

[0023] Preferably, the fixed beds are connected in series by straight stainless steel rigid tubes.

[0024] Preferably, the amount of microgel slurry added is 60-140g per 10,000g of pretreated oil.

[0025] A method for encapsulating deodorized high-purity Antarctic krill oil includes the following steps: degassing the deodorized high-purity Antarctic krill oil three times at 25°C using alternating vacuum and nitrogen filling; preparing a gelatin / glycerol / purified water mass ratio of 100:30:70, dissolving the gelatin at 60°C, degassing under vacuum, and then maturing for 8 hours; casting a film with a thickness of 0.8 mm at 25°C and 40% relative humidity, quantitatively filling and sealing the film using a rotary die extrusion process, and then surface-drying and statically drying until the gelatin shell contains 7.1%-7.5% water.

[0026] The beneficial effects of this invention are:

[0027] This invention significantly reduces the fishy odor intensity of krill oil and effectively controls its oxidation process. By removing different fishy odor precursors in stages and in a targeted manner, the final product has a fresh and pure oil flavor. Simultaneously, this process effectively inhibits the formation of peroxides and the accumulation of secondary oxidation products during processing and storage, giving the oil excellent oxidative stability and extending its shelf life.

[0028] This invention achieves deep deodorization while efficiently preserving the functional nutrients in krill oil. In particular, the retention and loss of core active ingredients such as phospholipids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are reduced to extremely low levels, ensuring that the final product has high nutritional value and maintaining the inherent health benefits of krill oil.

[0029] This invention ensures the stability and continuity of the deodorization process by introducing a unique interface control mechanism between multi-stage processing units. This mechanism can dynamically capture odor components escaping from upstream units and provide buffer protection for subsequent units, avoiding drastic fluctuations in processing load and rapid failure of adsorbent materials. This makes the entire process more stable and reliable, resulting in high product quality uniformity.

[0030] This invention enhances the function of the adsorbent material by targeting the characteristics of the krill oil system. By endowing the adsorbent surface with special affinity properties, it can accurately distinguish and preferentially bind to target odor molecules, rather than large molecular nutrients such as phospholipids, thereby achieving efficient separation at the molecular level and greatly improving the selectivity of the deodorization process.

[0031] The deodorized krill oil product obtained by this invention exhibits good adaptability during the subsequent encapsulation process. The optimized oil and gelatin shell have excellent compatibility, and the resulting capsules show stable and reliable dissolution behavior. Furthermore, during long-term storage, they effectively inhibit the leaching of odorous substances and the intrusion of oxygen, ensuring that the final product has good sensory quality and storage stability. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1:

[0034] Step S1: Antioxidant Pretreatment

[0035] Add 4g of natural vitamin E (Kensing Covi-ox T-70 EU) to 10000g of krill oil raw material (AkerBioMarine, model Superba2, total phospholipid content 41.5%, EPA content 13.2%, DHA content 7.4%), stir at 25°C under nitrogen protection for 10 minutes, then add 0.5g of ascorbyl palmitate, stir at 50°C for 10 minutes to fully dissolve, and cool to 25°C to obtain pretreated crude krill oil;

[0036] Step S2: Preparation of γ-cyclodextrin metal-organic framework adsorbent

[0037] 1000g of γ-cyclodextrin was added to 2000g of water and stirred at 50°C for 30min. 60g of potassium hydroxide was added and stirred for 5min. 4000g of ethanol was added dropwise, and the mixture was allowed to stand at 25°C for 24h to crystallize. The mixture was then filtered and washed twice with 2000g of ethanol. The crystals were dried under vacuum at 45°C. A glycerol pre-wetting solution prepared with 200g of water and 1g of glycerol was then sprayed onto the surface of 800g of crystals. The mixture was sealed and allowed to stand for 12h to obtain the γ-cyclodextrin metal-organic framework adsorbent.

[0038] Step S3: Preparation of bifunctional silica adsorbent

[0039] 1500g of porous silica support (average particle size 150μm, average pore size 15nm) was mixed with 300g of polyethylene glycol 8000 and 300g of water, and rolled at room temperature for 30min. Then, 1500g of toluene and 150g of octyltriethoxysilane were added, and the mixture was refluxed at 70°C for 90min. The mixture was filtered, washed with ethanol, and vacuum dried at 60°C to obtain an oleophobic solid on the outer surface. The oleophobic solid was dispersed in a mixed solvent of 1500g of ethanol and 150g of water, and 300g of 3-mercaptopropyltrimethoxysilane was added. The mixture was refluxed at 110°C for 240min and filtered. 1000g of a 30wt% hydrogen peroxide aqueous solution was added, and the mixture was stirred at 25°C for 60min. The mixture was filtered, washed with water, and then added to 300g of 3- In a mixture of (trihydroxysilyl)propylmethylphosphonic acid monosodium salt and 600g of water, the mixture was rolled at 50°C for 120min, filtered, dried under vacuum at 60°C, and then atomized with 30g of water for pre-hydration before operation to obtain a bifunctional silica adsorbent.

[0040] Step S4: Preparation of chitosan-gallic acid / carboxybetaine double-grafted microgels

[0041] 100g of chitosan (95% deacetylation) was added to 2000g of 1wt% acetic acid aqueous solution and stirred at room temperature for 120min. Then, 30g of gallic acid, 5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 5g of N-hydroxysuccinimide were added and reacted at 25°C for 120min to obtain gallic acid-grafted chitosan. Then, 15g of carboxybetaine methacrylate, 2g of ammonium persulfate, and 1g of N,N′-methylenebisacrylamide were added and subjected to free radical in-situ graft polymerization at 60°C for 240min. The mixture was neutralized to pH 6.9, and small molecules were removed by ultrafiltration and freeze-dried to obtain chitosan-gallic acid / carboxybetaine double-grafted microgel.

[0042] Step S5: Assemble the fixed bed

[0043] Fixed bed loading and spacing: 720g of bifunctional silica adsorbent is loaded into fixed bed 1; 360g of γ-cyclodextrin metal-organic framework is loaded into fixed bed 2; 270g of bifunctional silica adsorbent is loaded into fixed bed 3; 180g of γ-cyclodextrin metal-organic framework is loaded into fixed bed 4; and 90g of bifunctional silica adsorbent is loaded into fixed bed 5. Nitrogen headspace protection is used. The height of fixed bed 1 is 270mm, fixed bed 2 is 243mm, fixed bed 3 is 180mm, fixed bed 4 is 144mm, and fixed bed 5 is 180mm. The columns are connected in series by stainless steel rigid tubes in a straight line, with a column spacing of 300mm and an inner diameter of 60mm.

[0044] Step S6: Run the fixed bed

[0045] 10,000g of pretreated crude krill oil was loaded into the feed tank, and the pump was started to feed at a constant rate of 800g / h. The feed was then passed through fixed bed 1 and fixed bed 2 in sequence. 30g of chitosan-gallic acid / carboxybetaine double-grafted microgel and 30g of ethanol were mixed and sheared and dispersed for 3min to form a microgel slurry. The slurry was then introduced into the mixing vessel through the outlet of fixed bed 2, and 60g of microgel slurry was added. The mixture was stirred for 3min and allowed to stand for 10min. The 10μm filter cartridges connected in series were started to filter the material and discharge it to the inlet of fixed bed 3. The feed was then continued through fixed beds 3, 4 and 5 at a rate of 800g / h. The resulting deodorized high-purity Antarctic krill oil was obtained.

[0046] Encapsulation process: 5000g of deodorized high-purity Antarctic krill oil was sealed under nitrogen at 25°C with 2.5g of natural vitamin E (Kensing Covi-ox T-70 EU) and 0.4g of ascorbate palmitate, and degassed by alternating vacuum and nitrogen filling three times; a gelatin sol was prepared: gelatin / glycerol / purified water = 100 / 30 / 70 (mass ratio), dissolved at 60°C, degassed under vacuum, and matured for 8 hours; a film thickness of 0.8mm was formed by casting at 25°C and 40%RH, and quantitative filling was carried out using a rotary die extrusion method, with a target fill weight of 500mg / capsule, and the capsules were sealed immediately; after demolding, the capsules were first surface-dried and then statically dried until the water content of the shell was 7.1%, thus obtaining encapsulated deodorized high-purity Antarctic krill oil.

[0047] Example 2:

[0048] Step S1: Antioxidant Pretreatment

[0049] Add 6g of natural vitamin E (Kensing Covi-ox T-70 EU) to 10000g of krill oil raw material (AkerBioMarine, model Superba2, total phospholipid content 41.5%, EPA content 13.2%, DHA content 7.4%), stir at 25°C under nitrogen protection for 10 minutes, then add 1g of ascorbyl palmitate, stir at 50°C for 10 minutes to fully dissolve, and cool to 25°C to obtain pretreated crude krill oil;

[0050] Step S2: Preparation of γ-cyclodextrin metal-organic framework adsorbent

[0051] 1000g of γ-cyclodextrin was added to 2000g of water and stirred at 50°C for 30min. 60g of potassium hydroxide was added and stirred for 5min. 4000g of ethanol was added dropwise, and the mixture was allowed to stand at 25°C for 24h to crystallize. The mixture was then filtered and washed twice with 2000g of ethanol. The crystals were dried under vacuum at 45°C. A glycerol pre-wetting solution prepared with 200g of water and 1g of glycerol was then sprayed onto the surface of 800g of crystals. The mixture was sealed and allowed to stand for 12h to obtain the γ-cyclodextrin metal-organic framework adsorbent.

[0052] Step S3: Preparation of bifunctional silica adsorbent

[0053] 1500g of porous silica support (average particle size 150μm, average pore size 15nm) was mixed with 300g of polyethylene glycol 8000 and 300g of water, and rolled at room temperature for 30min. Then, 1500g of toluene and 150g of octyltriethoxysilane were added, and the mixture was refluxed at 70°C for 90min. The mixture was filtered, washed with ethanol, and vacuum dried at 60°C to obtain an oleophobic solid on the outer surface. The oleophobic solid was dispersed in a mixed solvent of 1500g of ethanol and 150g of water, and 300g of 3-mercaptopropyltrimethoxysilane was added. The mixture was refluxed at 110°C for 240min and filtered. 1000g of a 30wt% hydrogen peroxide aqueous solution was added, and the mixture was stirred at 25°C for 60min. The mixture was filtered, washed with water, and then added to 300g of 3- In a mixture of (trihydroxysilyl)propylmethylphosphonic acid monosodium salt and 600g of water, the mixture was rolled at 50°C for 120min, filtered, dried under vacuum at 60°C, and then atomized with 30g of water for pre-hydration before operation to obtain a bifunctional silica adsorbent.

[0054] Step S4: Preparation of chitosan-gallic acid / carboxybetaine double-grafted microgels

[0055] 100g of chitosan (95% deacetylation) was added to 2000g of 1wt% acetic acid aqueous solution and stirred at room temperature for 120min. Then, 30g of gallic acid, 5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 5g of N-hydroxysuccinimide were added and reacted at 25°C for 120min to obtain gallic acid-grafted chitosan. Then, 15g of carboxybetaine methacrylate, 2g of ammonium persulfate, and 1g of N,N′-methylenebisacrylamide were added and subjected to free radical in-situ graft polymerization at 60°C for 240min. The mixture was neutralized to pH 6.8, and small molecules were removed by ultrafiltration and freeze-dried to obtain chitosan-gallic acid / carboxybetaine double-grafted microgel.

[0056] Step S5: Assemble the fixed bed

[0057] Fixed bed loading and spacing: 800g of bifunctional silica adsorbent is loaded into fixed bed 1; 400g of γ-cyclodextrin metal-organic framework is loaded into fixed bed 2; 300g of bifunctional silica adsorbent is loaded into fixed bed 3; 200g of γ-cyclodextrin metal-organic framework is loaded into fixed bed 4; and 100g of bifunctional silica adsorbent is loaded into fixed bed 5. Nitrogen headspace protection is used. The height of fixed bed 1 is 300mm, fixed bed 2 is 270mm, fixed bed 3 is 200mm, fixed bed 4 is 160mm, and fixed bed 5 is 200mm. The columns are connected in series by stainless steel rigid tubes in a straight line, with a column spacing of 300mm and an inner diameter of 60mm.

[0058] Step S6: Run the fixed bed

[0059] 10,000g of pretreated crude krill oil was loaded into the feed tank, and the pump was started to feed at a constant rate of 1,000g / h. The feed was then passed through fixed bed 1 and fixed bed 2 in sequence. 50g of chitosan-gallic acid / carboxybetaine double-grafted microgel and 50g of ethanol were mixed and sheared and dispersed for 3 minutes to form a microgel slurry. The slurry was then introduced into the mixing vessel through the outlet of fixed bed 2, and 100g of microgel slurry was added. The mixture was stirred for 3 minutes and allowed to stand for 12 minutes. The 10μm filter cartridge assembly connected in series was started to filter the material and discharge it to the inlet of fixed bed 3. The feed was then continued to pass through fixed beds 3, 4 and 5 at a rate of 1,000g / h. The resulting product was deodorized high-purity Antarctic krill oil.

[0060] Encapsulation process: 5000g of deodorized high-purity Antarctic krill oil was sealed under nitrogen at 25°C with 3g of natural vitamin E (Kensing Covi-ox T-70 EU) and 0.5g of ascorbyl palmitate, and degassed by alternating vacuum and nitrogen filling three times; a gelatinous sol was prepared: gelatin / glycerol / purified water = 100 / 30 / 70 (mass ratio), dissolved at 60°C, degassed under vacuum, and matured for 8 hours; a film thickness of 0.8mm was formed by casting at 25°C and 40%RH, and quantitative filling was carried out using a rotary die extrusion method, with a target fill weight of 500mg / capsule, and the capsules were sealed immediately; after demolding, the capsules were first surface-dried and then statically dried until the water content of the shell was 7.2%, thus obtaining encapsulated deodorized high-purity Antarctic krill oil.

[0061] Example 3:

[0062] Step S1: Antioxidant Pretreatment

[0063] Add 8g of natural vitamin E (Kensing Covi-ox T-70 EU) to 10000g of krill oil raw material (AkerBioMarine, model Superba2, total phospholipid content 41.5%, EPA content 13.2%, DHA content 7.4%), stir at 25°C under nitrogen protection for 10 minutes, then add 1.5g of ascorbyl palmitate, stir at 50°C for 10 minutes to fully dissolve, and cool to 25°C to obtain pretreated crude krill oil;

[0064] Step S2: Preparation of γ-cyclodextrin metal-organic framework adsorbent

[0065] 1000g of γ-cyclodextrin was added to 2000g of water and stirred at 50°C for 30min. 60g of potassium hydroxide was added and stirred for 5min. 4000g of ethanol was added dropwise, and the mixture was allowed to stand at 25°C for 24h to crystallize. The mixture was then filtered and washed twice with 2000g of ethanol. The crystals were dried under vacuum at 45°C. A glycerol pre-wetting solution prepared with 200g of water and 1g of glycerol was then sprayed onto the surface of 800g of crystals. The mixture was sealed and allowed to stand for 12h to obtain the γ-cyclodextrin metal-organic framework adsorbent.

[0066] Step S3: Preparation of bifunctional silica adsorbent

[0067] 1500g of porous silica support (average particle size 150μm, average pore size 15nm) was mixed with 300g of polyethylene glycol 8000 and 300g of water, and rolled at room temperature for 30min. Then, 1500g of toluene and 150g of octyltriethoxysilane were added, and the mixture was refluxed at 70°C for 90min. The mixture was filtered, washed with ethanol, and vacuum dried at 60°C to obtain an oleophobic solid on the outer surface. The oleophobic solid was dispersed in a mixed solvent of 1500g of ethanol and 150g of water, and 300g of 3-mercaptopropyltrimethoxysilane was added. The mixture was refluxed at 110°C for 240min and filtered. 1000g of a 30wt% hydrogen peroxide aqueous solution was added, and the mixture was stirred at 25°C for 60min. The mixture was filtered, washed with water, and then added to 300g of 3- In a mixture of (trihydroxysilyl)propylmethylphosphonic acid monosodium salt and 600g of water, the mixture was rolled at 50°C for 120min, filtered, dried under vacuum at 60°C, and then atomized with 30g of water for pre-hydration before operation to obtain a bifunctional silica adsorbent.

[0068] Step S4: Preparation of chitosan-gallic acid / carboxybetaine double-grafted microgels

[0069] 100g of chitosan (95% deacetylation) was added to 2000g of 1wt% acetic acid aqueous solution and stirred at room temperature for 120min. Then, 30g of gallic acid, 5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 5g of N-hydroxysuccinimide were added and reacted at 25°C for 120min to obtain gallic acid-grafted chitosan. Then, 15g of carboxybetaine methacrylate, 2g of ammonium persulfate, and 1g of N,N′-methylenebisacrylamide were added and subjected to free radical in-situ graft polymerization at 60°C for 240min. The mixture was neutralized to pH 7, and small molecules were removed by ultrafiltration and freeze-dried to obtain chitosan-gallic acid / carboxybetaine double-grafted microgel.

[0070] Step S5: Assemble the fixed bed

[0071] Fixed bed loading and spacing: 880g of bifunctional silica adsorbent is loaded in fixed bed 1; 440g of γ-cyclodextrin metal-organic framework is loaded in fixed bed 2; 330g of bifunctional silica adsorbent is loaded in fixed bed 3; 220g of γ-cyclodextrin metal-organic framework is loaded in fixed bed 4; and 110g of bifunctional silica adsorbent is loaded in fixed bed 5. Nitrogen headspace protection is used. The height of fixed bed 1 is 330mm, fixed bed 2 is 297mm, fixed bed 3 is 220mm, fixed bed 4 is 176mm, and fixed bed 5 is 220mm. The columns are connected in series by stainless steel rigid tubes in a straight line, with a column spacing of 300mm and an inner diameter of 60mm.

[0072] Step S6: Run the fixed bed

[0073] 10,000g of pretreated crude krill oil was loaded into the feed tank, and the pump was started to feed at a constant rate of 1200g / h. The feed was then passed through fixed bed 1 and fixed bed 2 in sequence. 70g of chitosan-gallic acid / carboxybetaine double-grafted microgel and 70g of ethanol were mixed and sheared and dispersed for 3min to form a microgel slurry. The slurry was then introduced into the mixing vessel through the outlet of fixed bed 2, and 140g of microgel slurry was added. The mixture was stirred for 3min and allowed to stand for 15min. The 10μm filter cartridges connected in series were started to filter the material and discharge it to the inlet of fixed bed 3. The feed was then continued to pass through fixed beds 3, 4 and 5 at a rate of 1200g / h. The resulting product was deodorized high-purity Antarctic krill oil.

[0074] Encapsulation process: 5000g of deodorized high-purity Antarctic krill oil was sealed under nitrogen at 25°C with 3.5g of natural vitamin E (Kensing Covi-ox T-70 EU) and 0.6g of ascorbate palmitate, and degassed by alternating vacuum and nitrogen filling three times; a gelatin sol was prepared: gelatin / glycerol / purified water = 100 / 30 / 70 (mass ratio), dissolved at 60°C, degassed under vacuum, and matured for 8 hours; a film thickness of 0.8mm was formed by casting at 25°C and 40%RH, and quantitative filling was carried out using a rotary die extrusion method, with a target fill weight of 500mg / capsule, and the capsules were sealed immediately; after demolding, the capsules were first surface-dried and then statically dried until the water content of the shell was 7.5%, thus obtaining encapsulated deodorized high-purity Antarctic krill oil.

[0075] Comparative Example 1:

[0076] The difference between Comparative Example 1 and Example 2 is that chitosan-gallic acid / carboxybetaine double-grafted microgel is not added in step S6 (i.e., the intercalation treatment of fixed bed 2 outlet-mixing vessel-microgel slurry-standing-10μm filter cartridge filtration is not performed); the other conditions are the same as in Example 2.

[0077] Comparative Example 2:

[0078] The difference between Comparative Example 2 and Example 2 is that the fixed bed sequence is only interchanged between fixed bed 1 and fixed bed 2, while the subsequent fixed bed sequence of fixed bed 3, fixed bed 4, and fixed bed 5 remains unchanged; the other conditions are the same as in Example 2.

[0079] Comparative Example 3:

[0080] The difference between Comparative Example 3 and Example 2 is that the outer surface oleophobication (octyltriethoxysilane) step was omitted when preparing the bifunctional silica adsorbent, and only the subsequent mercaptopropyl introduction, oxidation and phosphonic acid group modification steps were retained; the other conditions were the same as in Example 2.

[0081] Comparative Example 4:

[0082] The difference between Comparative Example 4 and Example 2 is that the γ-cyclodextrin metal-organic framework in the fixed bed was replaced with an equal mass of γ-cyclodextrin.

[0083] Comparative Example 5:

[0084] The difference between Comparative Example 5 and Example 2 is that: fixed bed 5 is removed, while the filling and height of the other fixed beds remain unchanged; the other conditions are the same as in Example 2.

[0085] Comparative Example 6:

[0086] The difference between Comparative Example 6 and Example 2 is that the carboxybetaine methacrylate in step S4 is replaced with an equal mass of ethyl methacrylate; the other conditions are the same as in Example 2.

[0087] Comparative Example 7:

[0088] The difference between Comparative Example 7 and Example 2 is that in step S2, instead of adding 300g of 3-(trihydroxysilyl)propylmethylphosphonic acid monosodium salt and 600g of water, 30g of water was directly atomized and sprayed as pre-hydration before operation; the other conditions were the same as in Example 2.

[0089] Performance testing:

[0090] Test Item 1: Peroxide Value (POV)

[0091] The procedure was performed according to Method II of GB 5009.227-2023: 5g of oil sample was weighed and placed in a stoppered conical flask. 30 mL of a dichloromethane-glacial acetic acid mixed solvent was added to dissolve the sample. 1 mL of potassium iodide test solution was added, and the sample was allowed to stand in the dark for 3 min. The solution was then titrated with 0.01 mol / L sodium thiosulfate standard solution to the starch endpoint. The titration was repeated twice, and the results are shown in Table 1.

[0092] Test item 2: Anisidine value (p-anisidine value)

[0093] Perform according to GB / T 24304-2024: Weigh 0.5g of oil sample, prepare 25mL with isooctane, take an equal volume and react with p-anisidine test solution for 10 min, measure the absorbance at 350nm, and calculate according to the standard formula; retain 0.1 for the result, and the results are shown in Table 1.

[0094] Test Item 3: Fatty Acid Composition and Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA)

[0095] According to the transesterification method in GB 5009.168-2016: 0.2 g of oil sample was weighed, and fatty acid methyl esters were prepared according to the standard. Gas chromatography was performed using a 60 m × 0.25 mm × 0.25 μm capillary column, with 1 μL injected (split 50:1), temperature programmed from 50 to 220 °C, and a flame ionization detector at 260 °C. Quantification was performed using the external standard method, and EPA, DHA, and total (mg / g) were reported separately. The results are shown in Table 1.

[0096] Test Item 4: Total Phospholipids (Total Phosphorus Conversion): According to GB / T 5537-2008: Weigh 0.2g of oil sample into a digestion tube, add 5.0mL of concentrated sulfuric acid, digest at 180-200℃ until the solution is clear, cool and make up to 50.0mL; take an appropriate amount of solution and add ammonium molybdate-ascorbic acid for color development, react at room temperature for 10min, measure the absorbance at 700nm, prepare a 0-2mg P / L curve with KH2PO4 as the external standard, convert the sample P content and calculate the total phospholipids according to phospholipid%=P%×25, n=3, the results are shown in Table 1.

[0097] Test Item 4: Sensory Scoring of Fishy Odor Intensity

[0098] In accordance with GB / T 10220-2012 and GB / T 10221-2021, 15 trained evaluators were organized to conduct a 9-point intensity scale (0 = no fishy smell, 9 = extremely strong fishy smell). Samples were randomly coded with three digits at 25℃. 1g of oil sample was placed in a 50mL odor cup, and the sample was smelled for 5s × 3 times before scoring. The average value was calculated, and the results are shown in Table 1.

[0099] Test item 5: Capsule dissolution

[0100] According to the "Pharmacopoeia 0931 Determination of Dissolution and Release (Method I, Basket Method)": the medium is 900 mL of water, the temperature is 37±0.5℃, and the rotation speed is 100 rpm; 6 tablets are taken from each batch, and samples are taken at 10, 20 and 30 min. The oil phase is extracted with an appropriate solvent and then weighed or quantified by UV / chromatography. The dissolution rate (%) at 30 min is calculated, and the results are shown in Table 1.

[0101] Table 1 Performance Test Results

[0102] Sample <![CDATA[Peroxide value / meq O2 / kg]]> Anisamine value EPA / mg / g DHA / mg / g Total EPA and DHA / mg / g Phospholipids / % Sensory intensity of fishy smell Dissolution rate (%) over 30 minutes Example 1 0.58 7.8 133.4 75.6 209.0 42.1 2.1 93.1 Example 2 0.42 5.6 134.7 76.1 210.8 42.8 1.6 95.3 Example 3 0.64 8.5 133.1 74.9 208.0 42.4 1.8 94.5 Comparative Example 1 0.89 17.9 132.2 73.4 205.6 41.1 3.8 92.5 Comparative Example 2 1.26 19.3 136.8 72.4 209.2 41.5 4.4 91.2 Comparative Example 3 0.74 15.2 123.7 70.1 193.8 39.6 4.2 90.8 Comparative Example 4 1.11 18.7 134.3 75.1 209.4 42.0 4.7 91.9 Comparative Example 5 0.97 12.9 134.0 75.0 209.0 42.2 3.5 93.6 Comparative Example 6 1.18 16.4 135.0 75.8 210.8 41.0 4.0 96.1 Comparative Example 7 1.04 14.8 132.8 74.0 206.8 40.8 3.9 92.1

[0103] Data Analysis:

[0104] As can be seen from the data in Examples 1-3 in Table 1, the Antarctic krill oil prepared by this invention achieves a balance of low oxidation, low fishy odor, and component retention in multiple key indicators. This reflects the synergistic effect of the bed sequence of first removing amines and then aldehydes, followed by further amine and aldehyde removal, and final polishing, as well as the spatial selectivity of oleophobic surface treatment and stratification of acidic sites within the pores. The intercalated chitosan-gallic acid / carboxybetaine double-grafted microgel constructs a transient trapping and interfacial antifouling barrier between the fixed beds, preventing secondary penetration of volatile amines and carbonyl groups into subsequent beds, while also reducing the co-adsorption of phospholipids, eicosapentaenoic acid, and docosahexaenoic acid. This results in a significant reduction in sensory fishy odor, simultaneous improvement in oxidation process indicators, and stable release during capsule dissolution. This comprehensive improvement is not a linear superposition of a single step, but rather a synergistic result of multiple materials and interfaces in the oil phase.

[0105] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, the fishy smell-related indicators in Comparative Example 1 increased, and the composition fluctuated more significantly. A possible reason is the absence of a chitosan-gallic acid / carboxylic acid betaine double-grafted microgel and a 10μm filter between fixed beds 2 and 3, leading to a higher instantaneous load on the subsequent fixed beds and easier adsorption penetration.

[0106] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, the flavor and stability of Comparative Example 2 are generally weaker. A possible reason is that after swapping the fixed bed 1 (bifunctional silica) and the fixed bed 2 (γ-cyclodextrin metal-organic framework), there was a mismatch in the staged adsorption, resulting in an unreasonable distribution of small molecule loading in the front end.

[0107] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, the composition of Comparative Example 3 continued to decline and the fishy smell was not adequately controlled. This may be because the bifunctional silica was not coated with octyltriethoxysilane to create an oleophobic outer surface, making it more prone to non-target co-adsorption, and its coordination with phosphonic acid groups was insufficient.

[0108] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, the flavor and oxidation-related indicators of Comparative Example 4 deteriorated simultaneously. This may be because the adsorption of small molecules in the oil phase became unstable without the use of the γ-cyclodextrin metal-organic framework, leading to increased penetration and accumulation.

[0109] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, the long-term stability and consistency of Comparative Example 5 decreased, and the fishy smell increased. The possible reason is the omission of the final treatment of the fixed bed 5, the lack of end polishing, and the incomplete removal of trace components.

[0110] As can be seen from the data in Table 1 for Example 2 and Comparative Example 6, Comparative Example 6 exhibits faster release but a decrease in flavor and stability, indicating a trade-off. This may be because the microgel did not incorporate carboxybetaine methacrylate, resulting in reduced interfacial regulation and transient capture capabilities of the interbed buffer.

[0111] As can be seen from the data in Table 1 for Example 2 and Comparative Example 7, the fishy smell of Comparative Example 7 was enhanced and accompanied by a decrease in selectivity. This may be because the bifunctional silica did not introduce phosphonic acid groups through the monosodium salt of 3-(trihydroxysilyl)propylmethylphosphonic acid, thus weakening its synergistic effect with the oleophobic coating of the outer surface.

[0112] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing deodorized high-purity Antarctic krill oil, characterized in that, Includes the following steps: (1) Antioxidant pretreatment: Under nitrogen protection, natural vitamin E and ascorbate palmitate were added to the krill oil raw material, stirred at 25°C for 10 min, stirred at 50°C for 10 min and then cooled to obtain pretreated oil; (2) Deodorization of the series system: The pretreated oil is fed through fixed bed 1 and fixed bed 2 in sequence at a feed rate of 800-1200g / h; microgel slurry is added at the outlet of fixed bed 2, sheared and dispersed for 3min and allowed to stand for 10-15min, filtered through a 10μm filter element and then discharged through fixed bed 3, fixed bed 4 and fixed bed 5 in sequence; Among them, fixed beds 1, fixed beds 3 and fixed beds 5 are filled with bifunctional silica adsorbents, and fixed beds 2 and fixed beds 4 are filled with γ-cyclodextrin metal-organic framework adsorbents. The microgel paste is composed of chitosan-gallic acid / carboxybetaine double-grafted microgel and ethanol in a weight ratio of 1:

1. The preparation of the bifunctional silica adsorbent includes: treating the outer surface of a porous silica carrier with octyltriethoxysilane to form an oleophobic layer; first introducing 3-mercaptopropyltrimethoxysilane into the pores, then oxidizing it with 30wt% hydrogen peroxide, followed by reacting it with 3-(trihydroxysilyl)propylmethylphosphonic acid monosodium salt to introduce phosphonic acid groups, and then drying and prehydrating to obtain the adsorbent. The chitosan-gallic acid / carboxybetaine double-grafted microgel was formed by acylation grafting of chitosan and gallic acid under EDC / NHS, followed by in-situ grafting polymerization of chitosan and carboxybetaine methacrylate under ammonium persulfate initiation and N,N′-methylenebisacrylamide crosslinking. Finally, it was neutralized to pH 6.8-7.0 and freeze-dried. The γ-cyclodextrin metal-organic framework adsorbent was obtained by adding ethanol dropwise to an aqueous solution of γ-cyclodextrin containing potassium hydroxide, allowing it to stand at 25°C for 24 hours to crystallize, washing with ethanol and drying under vacuum at 45°C, and then pre-wetting with an aqueous solution containing glycerol.

2. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The amount of natural vitamin E added per 10,000g of krill oil raw material is 4-8g, and the amount of ascorbate palmitate added is 0.5-1.5g.

3. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The loading amounts of the fixed beds, calculated per 10,000g of feed, are as follows: fixed bed 1: 720-880g, fixed bed 2: 360-440g, fixed bed 3: 270-330g, fixed bed 4: 180-220g, and fixed bed 5: 90-110g.

4. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The weight ratio of the porous silica carrier, octyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-(trihydroxysilyl)propylmethylphosphonic acid monosodium salt is 10:1:2:

2.

5. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The weight ratio of chitosan, gallic acid, carboxybetaine methacrylate, and N,N′-methylenebisacrylamide is 100:30:15:

1.

6. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The weight ratio of potassium hydroxide to γ-cyclodextrin is 3:

50.

7. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The heights of the fixed beds 1-5 are 270-330mm, 243-297mm, 180-220mm, 144-176mm and 180-220mm respectively, the column spacing is 300mm and the column inner diameter is 60mm.

8. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The fixed beds are connected in series by straight stainless steel rigid pipes.

9. The method for preparing deodorized high-purity Antarctic krill oil according to claim 1, characterized in that, The amount of microgel paste added is 60-140g per 10,000g of pretreated oil.

10. A method for encapsulating high-purity Antarctic krill oil after deodorization, comprising the following steps: The deodorized high-purity Antarctic krill oil was degassed three times at 25°C using alternating vacuum and nitrogen purging. A gelatinous sol with a gelatin / glycerol / purified water mass ratio of 100:30:70 was prepared, dissolved at 60°C, degassed under vacuum, and then matured for 8 hours. A film with a thickness of 0.8 mm was formed by casting at 25°C and 40% relative humidity. The film was quantitatively filled and sealed using a rotary die extrusion process. After surface drying, the film was statically dried until the water content of the gelatinous shell was 7.1%-7.5%. The deodorized high-purity Antarctic krill oil was obtained by the preparation method of deodorized high-purity Antarctic krill oil according to any one of claims 1-9.