Method for removing glycidyl ester in mixed tocopherol

Abstract

The invention belongs to the technical field of tocopherols, and particularly provides a method for removing glycidyl ester in mixed tocopherols, which comprises the following steps: 1) pre-treating a vegetable oil deodorized distillate, and then carrying out molecular distillation and chromatography to obtain a tocopherol crude product; and 2) uniformly mixing the crude tocopherol product and an adsorbent, carrying out adsorption treatment, and filtering, the adsorbent being prepared from polysaccharide gel and a composite metal doped material, and the composite metal doped material comprising a zinc-doped zirconium skeleton component. The removal method has the advantages of thorough removal of glycidyl ester and high efficiency.

Description

Technical Field

[0001] This application belongs to the technical field of tocopherols, and particularly relates to a method for removing glycidyl esters from mixed tocopherols. Background Art

[0002] Natural tocopherols are dextrorotatory isomers with physiological activity, so they have better biological activity and food safety than synthetic tocopherols. They are non-toxic and side-effect-free to the human body, easy to absorb, and have high nutritional value. Therefore, they are widely used in the fields of medicine, food, cosmetics, health products, etc. The sources of natural tocopherols in nature are very limited. Currently, the main source in the industrial production field is the by-products (deodorizer distillates) obtained from oil processing. However, the composition of deodorizer distillates is complex, and it is difficult to effectively extract high-purity natural tocopherols from deodorizer distillates by a single method. Therefore, it is often necessary to pre-treat the raw materials and then purify the tocopherols. Currently, the commonly used pre-treatment methods are mainly esterification and saponification methods, and the extraction processes mainly include solvent extraction, supercritical fluid extraction, distillation, adsorption, and ion exchange methods, etc. In addition, there are also some physical assistance means such as external ultrasonic assistance, microwave assistance, and magnetic fields.

[0003] After adopting the above separation and purification processes, most impurities such as free fatty acids in the tocopherol product can be removed, but a certain amount of glycidyl esters (GEs) will still remain. The toxicological data of glycidyl esters due to their genotoxicity and nephrotoxicity have been gradually disclosed. Currently, some institutions have set regulations and limits on the content of GEs in health products and infant foods. The control and removal technology of GEs in tocopherols has always been a hot and difficult issue in the industry. It is possible to optimize the deodorization conditions of vegetable oils by inhibiting and removing their precursor substances, controlling the content of monoglycerides, diglycerides, and chloride ions, appropriately reducing the deodorization temperature and shortening the deodorization time. And removal methods such as enzymatic hydrolysis, two-stage molecular distillation, and adsorption methods are used to reduce the content of GEs.

[0004] Among various removal methods, enzymatic hydrolysis has the risk of hydrolyzing triglycerides due to the participation of enzymes. In contrast, the adsorption method not only has advantages such as less investment and low energy consumption, but also can adsorb harmful components in oils such as polycyclic aromatic hydrocarbons and plasticizers. For example, the patent application document with the application publication number CN111233813A discloses a method for removing glycidyl esters from mixed tocopherols, which is to use the adsorption of the first-stage strong-base ion exchange resin and the second-stage strong-base ion exchange resin, and at the same time control low temperature to reduce the generation of glycidyl esters. This method is relatively cumbersome and costly.

[0005] Another example is "Study on the Removal of 3-Chloropropanol Esters and Glycidyl Esters in Fish Oil by Biosorbents" - Zhang Fang. The author used biochar-clay as an adsorbent to remove glycidyl esters, but the removal rate and stability are still low for food-grade tocopherol products. Therefore, how to develop a method with a high removal rate of glycidyl esters in tocopherol is an urgent problem to be solved. Summary of the Invention

[0006] In view of the above problems, in order to further improve the removal rate of glycidyl esters in tocopherol, the present application provides a method for removing glycidyl esters in mixed tocopherol.

[0007] The present application provides a method for removing glycidyl esters in mixed tocopherol, which includes the following steps: 1) Pretreat the vegetable oil deodorizer distillate, and then obtain crude tocopherol through molecular distillation and chromatography; 2) Take the crude tocopherol and the adsorbent, mix them evenly, conduct adsorption treatment, and then filter; the adsorbent is made of polysaccharide gel and composite metal-doped material; the composite metal-doped material includes a zinc-doped zirconium framework component.

[0008] Further, in step 1), the pretreatment is to conduct esterification treatment on the vegetable oil deodorizer distillate; and / or, in step 1), the vegetable oil is one of rapeseed oil, soybean oil, corn oil, olive oil, cottonseed oil, sunflower oil, and camellia oil; and / or, in step 1), the molecular distillation is respectively carried out for primary molecular distillation, secondary molecular distillation, and tertiary molecular distillation.

[0009] Further, in step 2), the adsorption treatment is carried out at a temperature of 70-85 °C for 30-45 min; and / or, in step 2), the polysaccharide gel is one or more of cellulose gel, cyclodextrin gel, and sodium alginate gel; and / or, in step 2), the composite metal-doped material is composed of a zinc-doped zirconium framework component and a calcium-magnesium co-deposition component in a mass ratio of 1:(0.5-0.65).

[0010] Further, the polysaccharide gel is prepared by a method including the following steps: A) Take deionized water, polysaccharide, and 3-aminophenylboronic acid, mix them evenly, and then add aldehyde-terminated polyethylene glycol and mix evenly to obtain an intermediate liquid; B) Add polyethyleneimine to the intermediate liquid, conduct ultrasonic oscillation, and obtain the product after aging and washing.

[0011] Further, in step A), the mass ratio of deionized water, polysaccharide, and 3-aminophenylboronic acid is 1:(0.15-0.2):(0.03-0.05); And / or, in step A), the polysaccharide is one or more of cellulose, cyclodextrin, and sodium alginate; And / or, in step A), the proportion of terminal aldehyde group polyethylene glycol in the intermediate liquid is 35-60 wt%.

[0012] Further, in step B), the molar ratio of the amino group of polyethyleneimine to the aldehyde group of terminal aldehyde group polyethylene glycol in the intermediate liquid is 1:(0.8-1); And / or, in step B), the Mw of polyethyleneimine is 400-1500.

[0013] Further, the zinc-doped zirconium framework component is prepared by the following steps: preparing a zinc-zirconium mixed solution, adding glacial acetic acid and 2,6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution and mixing evenly, heating and reacting, washing, drying, and calcining to obtain.

[0014] Further, the calcium-magnesium co-deposition component is prepared by including the following steps: preparing a calcium-magnesium mixed solution, adding triethylamine to the calcium-magnesium mixed solution, then dropping a sodium carbonate solution, then heating to remove triethylamine, centrifuging to separate to obtain a precipitate, washing and drying to obtain.

[0015] Further, the adsorbent is prepared by the method of the following steps: S1: Adding a hydrochloric acid buffer solution to the polysaccharide gel, and then adding a composite metal doping material and mixing evenly to obtain a mixed solution; S2: Dropwise adding a quaternary ammonium base solution to the mixed solution until neutral under continuous stirring, filtering, washing, and drying to obtain.

[0016] Further, the hydrochloric acid buffer solution includes the following raw materials: deionized water, concentrated hydrochloric acid, sodium chloride, and zinc chloride.

[0017] Compared with the prior art, the present application has the following beneficial effects: 1. The present application adopts a compound system of polysaccharide gel and composite metal doping material. On the one hand, through the capillary adsorption effect of the polysaccharide gel, the diffusion and adsorption effects of glycidyl ester on the surface and inside of the adsorbent are improved; on the other hand, through the intermolecular conjugation effect generated by the composite metal doping material, the enrichment and adsorption effect on glycidyl ester molecules are enhanced, promoting the adsorption of glycidyl ester.

[0018] 2. In the composite metal-doped material of the present application, the introduction of irregular nanoparticle-shaped calcium-magnesium co-deposited components can produce an interfacial adsorption effect on glycidyl ester molecules, thereby enhancing the removal rate of the adsorbent for glycidyl esters. In addition, due to the different adsorption rates of the polysaccharide gel and the composite metal-doped material for glycidyl esters, and the adsorbent is a structural system with the composite metal-doped material as the core and the polysaccharide gel as the shell, this can weaken the concentration polarization phenomenon generated during the glycidyl ester adsorption process to a certain extent, thereby obtaining a stable and efficient adsorption effect. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the adsorption stability test data of the adsorbents in Examples 1-3 and Control Groups 1-2 of the present application.

[0020] Figure 2 It is a schematic diagram of the hybrid formation process of the adsorbents in Examples 1-3 of the present application.

[0021] Figure 3 It is a schematic diagram of the appearance of the polysaccharide gel and the adsorbent in Example 3 of the present application.

[0022] Figure 4 It is a TEM image of the adsorbent in Example 1 of the present application.

[0023] Figure 5 It is a TEM image of the adsorbent in Example 2 of the present application.

[0024] Figure 6 It is a TEM image of the adsorbent in Example 3 of the present application. Detailed Embodiments

[0025] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0026] Through a large number of experimental studies, the present application has developed an adsorption system of a metal-doped material composite polysaccharide gel based on traditional inorganic adsorption materials such as clay, activated carbon, attapulgite, nano-silica, bentonite, and diatomite, starting from the adsorption characteristics of glycidyl ester molecules, greatly improving the removal rate of glycidyl esters.

[0027] Specifically, the present application provides a method for removing glycidyl esters in mixed tocopherols, including the following steps: 1) Pretreat the vegetable oil deodorizer distillate, and then obtain crude tocopherols through molecular distillation and chromatography; 2) Mix the crude tocopherol and the adsorbent evenly, conduct adsorption treatment, and then filter; the adsorbent is made of a polysaccharide gel and a composite metal-doped material; the composite metal-doped material includes a zinc-doped zirconium framework component.

[0028] Further, in step 1), the pretreatment is to conduct esterification treatment on the vegetable oil deodorizer distillate. And / or, in step 1), the vegetable oil is one of rapeseed oil, soybean oil, corn oil, olive oil, cottonseed oil, sunflower oil, and camellia oil. And / or, in step 1), the molecular distillation is to conduct primary molecular distillation, secondary molecular distillation, and tertiary molecular distillation separately.

[0029] In some specific embodiments, in step 1), the esterification treatment is to add a dehydrating agent and an immobilized lipase to the vegetable oil deodorizer distillate, mix evenly, slowly add methanol to conduct an esterification reaction to obtain an esterification solution, filter to recover the dehydrating agent and the immobilized lipase, let it stand and separate layers, take the upper layer liquid, wash it with water to remove the residual methanol and lipase, and finally conduct cold precipitation and crystallization.

[0030] In some specific embodiments, in step 1), the molecular distillation is to conduct primary molecular distillation, secondary molecular distillation, and tertiary molecular distillation separately. More preferably, the specific process of the primary molecular distillation is: preheating temperature 40 - 70°C, system pressure 0.1 Pa, heating wall temperature 80 - 100°C, scraper rotation speed 80 - 110 r / min, feed rate 5 - 7 mL / min; the specific process of the secondary molecular distillation is: preheating temperature 75 - 80°C, system pressure 0.1 Pa, heating wall temperature 120 - 150°C, scraper rotation speed 90 - 110 r / min, feed rate 3 - 5 mL / min; the specific process of the tertiary molecular distillation is: system pressure 0.1 Pa, heating wall temperature 160 - 240°C, scraper rotation speed 100 - 200 r / min, feed rate 2 - 6 mL / min. More preferably, under normal circumstances, when the specific process of the primary molecular distillation is preheating temperature 50°C, system pressure 0.1 Pa, heating wall temperature 90°C, scraper rotation speed 90 r / min, feed rate 6 mL / min; the specific process of the secondary molecular distillation is: preheating temperature 80°C, system pressure 0.1 Pa, heating wall temperature 150°C, scraper rotation speed 100 r / min, feed rate 5 mL / min; the specific process of the tertiary molecular distillation is: system pressure 0.1 Pa, heating wall temperature 200°C, scraper rotation speed 150 r / min, feed rate 4 mL / min, better experimental results can be obtained at this time.

[0031] Further, in step 2), the adsorption treatment is to conduct adsorption at a temperature of 70 - 85°C for 30 - 45 min. And / or, in step 2), the polysaccharide gel is one or more of cellulose gel, cyclodextrin gel, and sodium alginate gel; And / or, in step 2), the composite metal-doped material is composed of a zinc-doped zirconium framework component and a calcium-magnesium co-deposition component in a mass ratio of 1:(0.5 - 0.65).

[0032] In some specific embodiments, in step 2), the adsorption treatment is carried out at temperatures of 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C for 30 min, 32 min, 35 min, 36 min, 38 min, 40 min, 43 min, 45 min. More preferably, generally, in step 2), the adsorption treatment is carried out at 80°C for 40 min, and better experimental results can be obtained at this time.

[0033] In some specific embodiments, in step 2), the composite metal-doped material composed of a zinc-doped zirconium framework component and a calcium-magnesium co-deposition component can be in a mass ratio of 1:0.5, 1:0.51, 1:0.52, 1:0.53, 1:0.54, 1:0.55, 1:0.56, 1:0.57, 1:0.58, 1:0.59, 1:0.60, 1:0.61, 1:0.62, 1:0.63, 1:0.64, 1:0.65. Generally, in step 2), when the composite metal-doped material is composed of a zinc-doped zirconium framework component and a calcium-magnesium co-deposition component in a mass ratio of 1:0.55, better experimental results can be obtained.

[0034] Furthermore, the polysaccharide gel is prepared by a method including the following steps: A) Mix deionized water, polysaccharide, and 3-aminophenylboronic acid evenly, and then add aldehyde-terminated polyethylene glycol and mix evenly to obtain an intermediate solution; B) Add polyethyleneimine to the intermediate solution, ultrasonically vibrate, and obtain the product after aging and washing.

[0035] Furthermore, in step A), the mass ratio of deionized water, polysaccharide, and 3-aminophenylboronic acid is 1:(0.15 - 0.2):(0.03 - 0.05); And / or, in step A), the polysaccharide is one or more of cellulose, cyclodextrin, and sodium alginate; And / or, in step A), the proportion of aldehyde-terminated polyethylene glycol in the intermediate solution is 35 - 60 wt%.

[0036] In some specific embodiments, in step A), the mass ratio of deionized water, polysaccharide, and 3-aminophenylboronic acid can be 1:0.15:0.03, 1:0.16:0.03, 1:0.17:0.03, 1:0.18:0.03, 1:0.19:0.03, 1:0.20:0.03, 1:0.15:0.035, 1:0.16:0.035, 1:0.17:0.035, 1:0.18:0.035, 1:0.19:0.035, 1:0.20:0.035, 1:0.15:0.04, 1:0.16:0.04, 1:0.17:0.04, 1:0.18:0.04, 1:0.19:0.04, 1:0.20:0.04, 1:0.15:0.045, 1:0.16:0.045, 1:0.17:0.045, 1:0.18:0.045, 1:0.19:0.045, 1:0.20:0.045, 1:0.15:0.05, 1:0.16:0.05, 1:0.17:0.05, 1:0.18:0.05, 1:0.19:0.05, 1:0.20:0.05. More preferably, generally, in step A), when the mass ratio of deionized water, polysaccharide, and 3-aminophenylboronic acid is 1:0.15:0.05, or within a 5% floating range of this ratio, better experimental results can be obtained.

[0037] In some specific embodiments, generally, better results can be achieved when the polysaccharide is composed of cyclodextrin and sodium alginate. More preferably, the polysaccharide is composed of cyclodextrin and sodium alginate in a mass ratio of 1:(5 - 10). More preferably, when the polysaccharide is composed of cyclodextrin and sodium alginate in a mass ratio of 1:8, better experimental results can be obtained.

[0038] In some specific embodiments, in step A), the proportion of aldehyde-terminated polyethylene glycol in the intermediate solution can be 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%. Generally, in step A), when the proportion of aldehyde-terminated polyethylene glycol in the intermediate solution is 50wt%, and within about 5% fluctuation of this mass proportion, comparable and better experimental results can be obtained.

[0039] Further, in step B), the molar ratio of the amino group of polyethyleneimine to the aldehyde group of aldehyde-terminated polyethylene glycol in the intermediate solution is 1:(0.8 - 1); And / or, in step B), the Mw of the polyethyleneimine is 400 - 1500.

[0040] In some specific embodiments, in step B), the molar ratio of the amino group of polyethyleneimine to the aldehyde group of the aldehyde-terminated polyethylene glycol in the intermediate solution can be 1:0.8, 1:0.81, 1:0.82, 1:0.83, 1:0.84, 1:0.85, 1:0.86, 1:0.87, 1:0.88, 1:0.89, 1:0.9, 1:0.91, 1:0.92, 1:0.93, 1:0.94, 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1. Generally, in step B), a better experimental effect can be obtained when the molar ratio of the amino group of polyethyleneimine to the aldehyde group of the aldehyde-terminated polyethylene glycol in the intermediate solution is 1:1.

[0041] In some specific embodiments, in step B), the Mw of the polyethyleneimine can be 400, 600, 800, 1000, 1200, 1500. Generally, in step B), a better experimental effect can be obtained when the Mw of the polyethyleneimine is 600.

[0042] Further, the zinc-doped zirconium framework component is prepared by the following steps: Prepare a zinc-zirconium mixed solution, add glacial acetic acid and 2,6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution and mix evenly, heat and react, wash, dry, and calcine to obtain.

[0043] Further, the calcium-magnesium co-deposition component is prepared by including the following steps: Prepare a calcium-magnesium mixed solution, add triethylamine to the calcium-magnesium mixed solution, then dropwise add sodium carbonate solution, then heat to remove triethylamine, centrifuge to obtain a precipitate, wash and dry to obtain.

[0044] Further, the adsorbent is prepared by the method of the following steps: S1: Add a hydrochloric acid buffer solution to the polysaccharide gel, and then add the composite metal doping material and mix evenly to obtain a mixed solution; S2: Dropwise add a quaternary ammonium base solution to the mixed solution until it is neutral under continuous stirring, filter, wash, and dry to obtain.

[0045] Further, the hydrochloric acid buffer solution includes the following raw materials: deionized water, concentrated hydrochloric acid, sodium chloride, zinc chloride.

[0046] In some specific embodiments, the method for preparing the hydrochloric acid buffer solution is as follows: Weigh 29.25 g of sodium chloride and place it in a 500 mL beaker. Add approximately 200 mL of deionized water and stir until it completely dissolves. Then, accurately measure 0.84 mL of concentrated hydrochloric acid with a pipette and slowly add it to the above sodium chloride solution while stirring. Transfer the resulting solution to a 1000 mL volumetric flask, rinse the beaker and glass rod 2 - 3 times with a small amount of deionized water, transfer the rinsing solution to the volumetric flask as well, add deionized water to the volumetric flask up to the calibration line, shake well, and finally measure the pH value of the prepared buffer solution with a pH meter. According to the reading of the pH meter, fine-tune it with dilute hydrochloric acid or sodium hydroxide solution until pH = 4.0 is achieved.

[0047] Example 1 The method for removing glycidyl esters from the mixed tocopherols in this example includes the following steps: 1) Use the deodorized distillate of rapeseed oil as the reaction liquid and load it into a reaction vessel for pretreatment (esterification treatment). Add a dehydrating agent and Novozym 435 immobilized lipase (10000 U / g, dosage 0.6 wt%) to the reaction vessel and mix evenly. Slowly add methanol for esterification reaction at a stirring speed of 300 rpm to obtain an esterified liquid. The esterification temperature is 40°C, the molar ratio of alcohol to acid is 2:1, the reaction time is 6 h. Filter to recover the dehydrating agent and immobilized lipase, let it stand for stratification, take the upper layer liquid, wash it with water to remove residual methanol and lipase, and finally perform cold crystallization; Then subject the material liquid obtained after pretreatment to molecular distillation. Among them, the specific process of the first-stage molecular distillation is: preheating temperature 50°C, system pressure 0.1 Pa, heating wall temperature 90°C, scraper rotation speed 90 r / min, feeding speed 6 mL / min; the specific process of the second-stage molecular distillation is: preheating temperature 80°C, system pressure 0.1 Pa, heating wall temperature 150°C, scraper rotation speed 100 r / min, feeding speed 5 mL / min; the specific process of the third-stage molecular distillation is: system pressure 0.1 Pa, heating wall temperature 200°C, scraper rotation speed 150 r / min, feeding speed 4 mL / min; Then mix the material liquid obtained after molecular distillation with absolute ethanol, and the volume ratio of the material liquid to absolute ethanol is 3:1. Then pour it into a chromatography column (packed with porous styrene PA308 type basic anion resin, crosslinking degree 4%), let it stand, add absolute ethanol to desorb weakly adsorbed substances, collect the effluent, and then concentrate and recover ethanol at a temperature of 60°C; add acetic acid / ethanol solution again to desorb tocopherols, collect the effluent, and then concentrate and recover ethanol at a temperature of 60°C. Subject the obtained material liquid to chromatography again to obtain crude tocopherols; 2) Mix 500 g of crude tocopherol and 5 g of adsorbent evenly, conduct adsorption treatment, and then filter. The total tocopherol content in the mixed tocopherol product measured by high performance liquid chromatography-mass spectrometry is 95.8%, and the glycidyl ether content is 98 μg / kg.

[0048] The adsorbent is prepared by the following method: Take 50 g of polysaccharide gel, then add 20 g of composite metal doped material, mix evenly, freeze-dry and pulverize to obtain.

[0049] The polysaccharide gel is prepared by mixing deionized water and sodium alginate in a mass ratio of 1:0.15.

[0050] The composite metal doped material is a zinc-doped zirconium framework component, which is prepared by the following steps: Weigh 2.3 g of zirconium chloride and 1.08 g of zinc chloride and dissolve them in 200 mL of DMF, then prepare a zinc-zirconium mixed solution. Add 30 mL of glacial acetic acid and 2.16 g of 6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution and mix evenly. Heat to 120 °C and react for 24 h, wash with absolute ethanol, dry at 60 °C, and then calcine at 450 °C for 2 h to obtain.

[0051] Example 2 The method for removing glycidyl esters in the mixed tocopherol of this example includes the following steps: 1) Load the deodorized distillate of rapeseed oil as the reaction liquid into the reaction vessel for pretreatment (esterification treatment). Add a dehydrating agent and Novozym 435 immobilized lipase (10000 U / g, dosage 0.6 wt%) to the reaction vessel and mix evenly. Slowly add methanol for esterification reaction at a stirring speed of 300 rpm to obtain an esterified liquid. The esterification temperature is 40 °C, the molar ratio of alcohol to acid is 2:1, the reaction time is 6 h. Filter to recover the dehydrating agent and immobilized lipase, let it stand for stratification, take the upper layer liquid, wash with water to remove residual methanol and lipase, and finally conduct cold precipitation crystallization; Then subject the material liquid obtained after pretreatment to molecular distillation. Among them, the specific process of the first-stage molecular distillation is: preheating temperature 50 °C, system pressure 0.1 Pa, heating wall temperature 90 °C, scraper speed 90 r / min, feed rate 6 mL / min; the specific process of the second-stage molecular distillation is: preheating temperature 80 °C, system pressure 0.1 Pa, heating wall temperature 150 °C, scraper speed 100 r / min, feed rate 5 mL / min; the specific process of the third-stage molecular distillation is: system pressure 0.1 Pa, heating wall temperature 200 °C, scraper speed 150 r / min, feed rate 4 mL / min; Then, the feed liquid obtained after molecular distillation is mixed with absolute ethanol, and the volume ratio of the feed liquid to absolute ethanol is 3:1. Then, it is poured into a chromatography column (packed with porous styrene PA308 type alkaline anion resin, crosslinking degree 4%), and after standing, absolute ethanol is added to desorb weakly adsorbed substances. The effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C; acetic acid / ethanol solution is added again to desorb tocopherol, the effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C. The obtained feed liquid is chromatographed again to obtain crude tocopherol; 2) Take 500 g of crude tocopherol and 5 g of adsorbent, mix them evenly, perform adsorption treatment, and then filter. The total content of tocopherol in the mixed tocopherol product is measured to be 96.5% by high performance liquid chromatography-mass spectrometry (HPLC-MS), and glycidyl ether is not detected.

[0052] The adsorbent is prepared by the following method: S1: Add 100 mL of hydrochloric acid buffer solution (the preparation method is as described above) to 50 g of polysaccharide gel, and then add 20 g of composite metal doping material and mix evenly to obtain a mixed solution; S2: Dropwise add quaternary ammonium hydroxide solution to the mixed solution until it is neutral under continuous stirring, filter, wash, dry, and pulverize and grind to obtain the product.

[0053] The polysaccharide gel is prepared by the following method: A) Take 100 mL of deionized water, 15 g of polysaccharide, and 5 g of 3-aminophenylboronic acid, mix them evenly, and then add terminal aldehyde group polyethylene glycol, controlling the proportion of terminal aldehyde group polyethylene glycol in the intermediate liquid to be 50 wt%, and mix evenly to obtain an intermediate liquid; B) Add polyethyleneimine to the intermediate liquid, controlling the molar ratio of the amino group of polyethyleneimine to the aldehyde group of terminal aldehyde group polyethylene glycol in the intermediate liquid to be 1:1, perform ultrasonic oscillation, aging, and washing to obtain the product.

[0054] Among them, the polysaccharide is composed of cyclodextrin and sodium alginate in a mass ratio of 1:8. The Mw of polyethyleneimine is 600. The terminal aldehyde group polyethylene glycol is bis-terminal aldehyde group polyethylene glycol (CHO-PEG-CHO), and the Mv of the polyethylene glycol chain is 2000. The quaternary ammonium hydroxide solution is a 45 wt% tetrabutylammonium hydroxide solution.

[0055] The composite metal doping material is a zinc-doped zirconium framework component, which is prepared by the following steps: Weigh 2.3 g of zirconium chloride and 1.08 g of zinc chloride and dissolve them in 200 mL of DMF, and then prepare a zinc-zirconium mixed solution. Add 30 mL of glacial acetic acid and 2.16 g of 6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution and mix evenly. Heat to 120°C and react for 24 h, wash with absolute ethanol, dry at a temperature of 60°C, and then calcine at 450°C for 2 h to obtain the product.

[0056] Example 3 The method for removing glycidyl esters from mixed tocopherols in this embodiment includes the following steps: 1) Use rapeseed oil deodorizer distillate as the reaction liquid and load it into a reaction vessel for pretreatment (esterification treatment). Add a dehydrating agent and Novozym 435 immobilized lipase (10,000 U / g, dosage 0.6 wt%) into the reaction vessel and mix evenly. Slowly add methanol for esterification reaction at a stirring speed of 300 rpm to obtain an esterified liquid. The esterification temperature is 40 °C, the molar ratio of alcohol to acid is 2:1, the reaction time is 6 h. Filter and recover the dehydrating agent and immobilized lipase, let it stand for stratification, take the upper layer liquid, wash it with water to remove residual methanol and lipase, and finally carry out cold crystallization; Then subject the material liquid obtained after pretreatment to molecular distillation. Among them, the specific process of the first-stage molecular distillation is: preheating temperature 50 °C, system pressure 0.1 Pa, heating wall temperature 90 °C, scraper speed 90 r / min, feeding speed 6 mL / min; the specific process of the second-stage molecular distillation is: preheating temperature 80 °C, system pressure 0.1 Pa, heating wall temperature 150 °C, scraper speed 100 r / min, feeding speed 5 mL / min; the specific process of the third-stage molecular distillation is: system pressure 0.1 Pa, heating wall temperature 200 °C, scraper speed 150 r / min, feeding speed 4 mL / min; Then mix the material liquid obtained after molecular distillation with absolute ethanol, and the volume ratio of the material liquid to absolute ethanol is 3:1. Then pour it into a chromatography column (filled with porous styrene PA308 type basic anion resin, cross-linking degree 4%), let it stand, add absolute ethanol to desorb weakly adsorbed substances, collect the effluent, and then concentrate and recover ethanol at a temperature of 60 °C; add acetic acid / ethanol solution again to desorb tocopherols, collect the effluent, and then concentrate and recover ethanol at a temperature of 60 °C. Subject the obtained material liquid to chromatography again to obtain crude tocopherols; 2) Take 500 g of crude tocopherols and 5 g of adsorbent, mix them evenly, carry out adsorption treatment, and then filter. The total content of tocopherols in the mixed tocopherol product measured by high performance liquid chromatography-mass spectrometry is 97.1%, and glycidyl ether is not detected.

[0057] The adsorbent is prepared by the following method: S1: Add 100 mL of hydrochloric acid buffer solution (preparation method as described above) to 50 g of polysaccharide gel, and then add 20 g of composite metal doping material and mix evenly to obtain a mixed liquid; S2: Dropwise add quaternary ammonium base solution to the mixed liquid until it is neutral under continuous stirring, filter, wash, dry, and pulverize and grind to obtain it.

[0058] The polysaccharide gel is prepared by the following method: A) Take 100 mL of deionized water, 15 g of polysaccharide, and 5 g of 3-aminophenylboronic acid, mix them evenly, then add terminal aldehyde group polyethylene glycol, and control the proportion of terminal aldehyde group polyethylene glycol in the intermediate liquid to be 50 wt%, and mix evenly to obtain the intermediate liquid; B) Add polyethyleneimine to the intermediate liquid, control the molar ratio of the amino group of polyethyleneimine to the aldehyde group of terminal aldehyde group polyethylene glycol in the intermediate liquid to be 1:1, perform ultrasonic oscillation, and obtain it after aging and washing.

[0059] Among them, the polysaccharide consists of cyclodextrin and sodium alginate in a mass ratio of 1:8. The Mw of polyethyleneimine = 600. The terminal aldehyde group polyethylene glycol is bis-terminal aldehyde group polyethylene glycol (CHO-PEG-CHO), and the Mv of the polyethylene glycol-based chain = 2000. The quaternary ammonium base solution is a 45 wt% tetrabutylammonium hydroxide solution.

[0060] The composite metal-doped material consists of a zinc-doped zirconium skeleton component and a calcium-magnesium co-deposited component in a mass ratio of 1:0.55.

[0061] The zinc-doped zirconium skeleton component is prepared by the following steps: Weigh 2.3 g of zirconium chloride and 1.08 g of zinc chloride and dissolve them in 200 mL of DMF, then prepare a zinc-zirconium mixed solution. Add 30 mL of glacial acetic acid and 2.16 g of 6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution and mix evenly. Heat to 120 °C and react for 24 h. Wash with absolute ethanol, dry at 60 °C, and then calcine at 450 °C for 2 h to obtain it.

[0062] The calcium-magnesium co-deposited component is prepared by including the following steps: Weigh 2.2 g of calcium chloride and 0.19 g of magnesium chloride and add them to a mixed solvent containing 50 mL of ethanol and 10 mL of deionized water, mix evenly to obtain a calcium-magnesium mixed solution, then add 50 g of triethylamine to the calcium-magnesium mixed solution, then dropwise add a slightly excessive sodium carbonate solution, then heat to remove triethylamine, perform centrifugal separation to obtain a precipitate, and wash and dry it to obtain it.

[0063] Control Group 1 The method for removing glycidyl esters in the mixed tocopherols of this control group includes the following steps: 1) Take the deodorized distillate of rapeseed oil as the reaction liquid and load it into a reaction container for pretreatment (esterification treatment). Add a dehydrating agent and Novozym 435 immobilized lipase (10000 U / g, dosage 0.6 wt%) to the reaction container and mix evenly. Slowly add methanol at a stirring speed of 300 rpm for an esterification reaction to obtain an esterified liquid. The esterification temperature is 40 °C, the molar ratio of alcohol to acid is 2:1, the reaction time is 6 h, filter and recover the dehydrating agent and immobilized lipase, let it stand for stratification, take the upper layer liquid, wash it with water to remove the residual methanol and lipase, and finally perform cold crystallization; Then, the pretreated feed liquid is subjected to molecular distillation. Among them, the specific process of the first-stage molecular distillation is as follows: the preheating temperature is 50°C, the system pressure is 0.1 Pa, the heating wall temperature is 90°C, the scraper rotation speed is 90 r / min, and the feeding speed is 6 mL / min; the specific process of the second-stage molecular distillation is: the preheating temperature is 80°C, the system pressure is 0.1 Pa, the heating wall temperature is 150°C, the scraper rotation speed is 100 r / min, and the feeding speed is 5 mL / min; the specific process of the third-stage molecular distillation is: the system pressure is 0.1 Pa, the heating wall temperature is 200°C, the scraper rotation speed is 150 r / min, and the feeding speed is 4 mL / min; Then, the feed liquid obtained after molecular distillation is mixed with absolute ethanol, and the volume ratio of the feed liquid to absolute ethanol is 3:1. Then, it is poured into a chromatography column (packed with porous styrene PA308 type basic anion resin, crosslinking degree 4%), and after standing, absolute ethanol is added to desorb the weakly adsorbed substances. The effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C; acetic acid / ethanol solution is added again to desorb tocopherol, the effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C. The obtained feed liquid is chromatographed again to obtain crude tocopherol; 2) Take 500 g of crude tocopherol and 5 g of adsorbent (activated clay, model 1060FF), mix them evenly, perform adsorption treatment, and then filter. The total tocopherol content in the mixed tocopherol product measured by high performance liquid chromatography-mass spectrometry is 85.3%, and the glycidyl ether content is 1736 μg / kg.

[0064] Control Group 2 The method for removing glycidyl esters in the mixed tocopherol of this control group includes the following steps: 1) Load the deodorized distillate of rapeseed oil as the reaction liquid into a reaction vessel for pretreatment (esterification treatment). Add a dehydrating agent and Novozym 435 immobilized lipase (10000 U / g, dosage 0.6 wt%) to the reaction vessel and mix evenly. Slowly add methanol under a stirring speed of 300 rpm for an esterification reaction to obtain an esterified liquid. The esterification temperature is 40°C, the molar ratio of alcohol to acid is 2:1, the reaction time is 6 h. Filter to recover the dehydrating agent and immobilized lipase, let it stand for stratification, take the upper layer liquid, wash it with water to remove the residual methanol and lipase, and finally perform cold crystallization; Then, the pretreated feed liquid is subjected to molecular distillation. Among them, the specific process of the first-stage molecular distillation is as follows: the preheating temperature is 50°C, the system pressure is 0.1 Pa, the heating wall temperature is 90°C, the scraper speed is 90 r / min, and the feeding speed is 6 mL / min; the specific process of the second-stage molecular distillation is: the preheating temperature is 80°C, the system pressure is 0.1 Pa, the heating wall temperature is 150°C, the scraper speed is 100 r / min, and the feeding speed is 5 mL / min; the specific process of the third-stage molecular distillation is: the system pressure is 0.1 Pa, the heating wall temperature is 200°C, the scraper speed is 150 r / min, and the feeding speed is 4 mL / min; Then, the feed liquid obtained after molecular distillation is mixed with absolute ethanol, and the volume ratio of the feed liquid to absolute ethanol is 3:1. Then, it is poured into a chromatography column (packed with porous styrene PA308 type basic anion resin, cross-linking degree 4%), and after standing, absolute ethanol is added to desorb weakly adsorbed substances. The effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C; acetic acid / ethanol solution is added again to desorb tocopherol, the effluent is collected, and then ethanol is concentrated and recovered at a temperature of 60°C. The obtained feed liquid is chromatographed again to obtain crude tocopherol; 2) Take 500 g of crude tocopherol and 5 g of adsorbent, mix them evenly, perform adsorption treatment, filter to obtain a mixed tocopherol product. The total tocopherol content in the mixed tocopherol product is measured to be 88.2 by high performance liquid chromatography-mass spectrometry (HPLC-MS), and the glycidyl ether content is 518 μg / kg.

[0065] The adsorbent is a composite metal-doped material, specifically a zinc-doped zirconium framework component, which is prepared by the following steps: Weigh 2.3 g of zirconium chloride and 1.08 g of zinc chloride and dissolve them in 200 mL of DMF. Then, a zinc-zirconium mixed solution is prepared. 30 mL of glacial acetic acid and 2.16 g of 6-naphthalenedicarboxylic acid are added to the zinc-zirconium mixed solution and mixed evenly. The mixture is heated to 120°C and reacted for 24 h, washed with absolute ethanol, dried at a temperature of 60°C, and then calcined at 450°C for 2 h to obtain the product.

[0066] Performance testing 1. Adsorption stability test Take α-tocopherol with a purity of 98%, β-tocopherol with a purity of 98%, and γ-tocopherol with a purity of 98%, mix them evenly according to the mass ratio of 1:1:1, add glycidyl palmitate (purity 99%), and prepare a mixed tocopherol test solution (containing 5000 μg / kg of glycidyl palmitate).

[0067] Add the adsorbents of Examples 1-3 and Controls 1-2 (the addition amount is 1 wt%) to 100 g of the mixed tocopherol test solution, Adsorb at 105 °C for 90 min. During the adsorption process, take out and stir evenly every 10 min. After the adsorption is completed, calculate the adsorption rate, and perform desorption treatment on the adsorbent. Replace the test solution and repeat the test 10 times to observe the adsorption stability of the adsorbent. The test results are as Figure 1 shown.

[0068] 2. Take the polysaccharide gel of Example 3 (not dissolved in hydrochloric acid buffer solution) and the adsorbent (i.e., polysaccharide gel@composite metal-doped material). The hybridization formation process of the adsorbent is as Figure 2 shown, and the appearance is as Figure 3 shown. It can be seen that the polysaccharide gel doped with the composite metal-doped material re-solidifies, the crosslinking density increases, and the adsorption performance is enhanced.

[0069] 3. Take the adsorbents of Examples 1-3 for scanning electron microscopy test. The results are as Figures 4-6 shown ( Figure 4 is Example 1, Figure 5 is Example 2, Figure 6 is Example 3). It can be seen that the outer layer of the particles is wrapped with porous polysaccharide gel, and the inside is the composite metal-doped material, which has a higher adsorption and removal rate compared with traditional adsorption materials such as activated carbon and bentonite.

[0070] Although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present invention.

Claims

1. A method for removing glycidyl esters in mixed tocopherols, characterized in that: It includes the following steps: 1) Pretreat the vegetable oil deodorizer distillate, and then obtain crude tocopherol through molecular distillation and chromatography; 2) Take the crude tocopherol and the adsorbent, mix them evenly, conduct adsorption treatment, and then filter; the adsorbent is made of polysaccharide gel and a composite metal-doped material; the composite metal-doped material includes a zinc-doped zirconium framework component.

2. The method for removing glycidyl esters in mixed tocopherols according to claim 1, wherein: In step 1), the pretreatment is to conduct esterification treatment on the vegetable oil deodorizer distillate; And / or, in step 1), the vegetable oil is one of rapeseed oil, soybean oil, corn oil, olive oil, cottonseed oil, sunflower oil, and camellia oil; And / or, in step 1), the molecular distillation is to conduct primary molecular distillation, secondary molecular distillation, and tertiary molecular distillation respectively.

3. The method for removing glycidyl esters in mixed tocopherols according to claim 1, characterized in that: In step 2), the adsorption treatment is to adsorb at a temperature of 70 - 85 °C for 30 - 45 min; And / or, in step 2), the polysaccharide gel is one or more of cellulose gel, cyclodextrin gel, and sodium alginate gel; And / or, in step 2), the composite metal-doped material is composed of a zinc-doped zirconium framework component and a calcium-magnesium co-deposition component in a mass ratio of 1:(0.5 - 0.65).

4. The method for removing glycidyl esters in mixed tocopherols according to claim 3, characterized in that: The polysaccharide gel is prepared by a method including the following steps: A) Take deionized water, polysaccharide, and 3-aminophenylboronic acid, mix them evenly, and then add aldehyde-terminated polyethylene glycol, and mix evenly to obtain an intermediate solution; B) Add polyethyleneimine to the intermediate solution, conduct ultrasonic oscillation, and obtain it after aging and washing.

5. The method for removing glycidyl esters in mixed tocopherols according to claim 4, characterized in that: In step A), the mass ratio of deionized water, polysaccharide, and 3-aminophenylboronic acid is 1:(0.15 - 0.2):(0.03 - 0.05); And / or, in step A), the polysaccharide is one or more of cellulose, cyclodextrin, and sodium alginate; And / or, in step A), the proportion of aldehyde-terminated polyethylene glycol in the intermediate solution is 35 - 60 wt%.

6. The method for removing glycidyl esters in mixed tocopherols according to claim 4, characterized in that: In step B), the molar ratio of the amino group of polyethyleneimine to the aldehyde group of aldehyde-terminated polyethylene glycol in the intermediate solution is 1:(0.8 - 1); And / or, in step B), the Mw of polyethyleneimine is 400 - 1500.

7. The method for removing glycidyl esters in mixed tocopherols according to claim 3, characterized in that: The zinc-doped zirconium framework component is prepared by the following steps: Prepare a zinc-zirconium mixed solution, add glacial acetic acid and 2,6-naphthalenedicarboxylic acid to the zinc-zirconium mixed solution, mix evenly, heat and react, wash, dry, and calcine to obtain it.

8. The method for removing glycidyl esters in mixed tocopherols according to claim 3, characterized in that: The calcium-magnesium co-deposition component is prepared by a method including the following steps: Prepare a calcium-magnesium mixed solution, add triethylamine to the calcium-magnesium mixed solution, then dropwise add sodium carbonate solution, then heat to remove triethylamine, centrifuge to obtain a precipitate, and wash and dry to obtain it.

9. The method for removing glycidyl esters in mixed tocopherols according to any one of claims 1-8, characterized in that: The adsorbent is prepared by a method including the following steps: S1: Add a hydrochloric acid buffer solution to the polysaccharide gel, and then add the composite metal-doped material and mix evenly to obtain a mixed solution; S2: Dropwise add a quaternary ammonium base solution to the mixed solution until it is neutral under continuous stirring, filter, wash, and dry to obtain it.

10. The method for removing glycidyl esters in mixed tocopherols according to claim 9, characterized in that: The hydrochloric acid buffer solution includes the following raw materials: deionized water, concentrated hydrochloric acid, sodium chloride, and zinc chloride.

Images