Preparation method of diacylglycerol grease for inhibiting generation of 3-chloropropanediol ester based on controllable release type chloride ion shielding agent

Abstract

The invention belongs to the technical field of grease refining and functional grease preparation, and particularly relates to a preparation method of diacylglycerol (DAG) grease for blocking generation of 3-chloropropanediol ester (3-MCPDE) based on a controllable release type chloride ion shielding agent. According to the method provided by the invention, aiming at the problem that 3-MCPDE is easy to generate in a high-temperature distillation stage in a DAG production process, through reaction time sequence control and thermal triggering chlorine capture, and through capture of free chloride ions and 3-MCPD ester precursors in the high-temperature stage, a generation way is blocked, so that a high-purity, low-risk, safe and stable DAG grease product is obtained. The preparation process provided by the invention is stable and controllable, the adding time of the screening agent is definite, the accurate release time of the screening agent can be ensured, and enzyme catalysis is not interfered; all the used components are food-grade or biodegradable materials, the risk of chemical residues is avoided, and the trapping agent and the reaction product used in the invention are food-grade or biodegradable substances, so that chemical residues are effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of oil refining and functional oil preparation technology, specifically relating to a method for preparing diacylglycerol oil based on a controlled-release chloride ion shielding agent to block the formation of 3-chloropropanediol ester. Background Technology

[0002] 3-Chloropropanediol (3-MCPD) and its ester compounds (3-MCPDE) are listed as food contaminants of concern by international food safety agencies. 3-MCPD is metabolized in the body to form free radicals and apparent toxic substances; long-term intake may damage the kidneys and liver, and has potential carcinogenic and mutagenic effects. 3-MCPDE can be hydrolyzed in the body to release free 3-MCPD, and its food safety risks are closely related to residual 3-MCPDE from oil processing. The World Health Organization (WHO) and the European Food Safety Authority (EFSA) have set a daily acceptable intake (TDI) of approximately 0.8 μg / kg body weight / day for 3-MCPD.

[0003] Diacylglycerol (DAG), as a functional oil, has attracted much attention due to its ability to reduce triglyceride (TAG) accumulation, aid in weight management, regulate blood lipids, and reduce the risk of cardiovascular disease during metabolism. DAG is widely used in edible oils, fortified foods, and health foods; therefore, high-purity and high-safety DAG preparation processes have significant industrial value. However, free chloride ions (Cl-) are unavoidably present during the enzymatic preparation of DAG. - Residual chlorides or other compounds can lead to the formation of reactive hydroxyl compounds, such as monoacylglycerol (MAG), during enzymatic hydrolysis. To improve the purity of DAG, molecular distillation or high-temperature purification is required. However, MAG hydroxyl groups readily undergo nucleophilic substitution reactions with chloride ions at high temperatures to generate 3-MCPDEs, which are subsequently hydrolyzed under acidic or alkaline conditions to produce free 3-MCPDs. Therefore, high-temperature distillation, MAG accumulation, and residual chloride ions are the core risk points for 3-MCPD formation in the DAG preparation chain.

[0004] Chinese patent CN202210228726.5 discloses a method for removing glycidyl esters and 3-MCPD from natural vitamin E through activated carbon treatment, activated carbon acylation, and amination. The process is simple and easy to implement, and can reduce the content of glycidyl esters and the total amount of 3-MCPD / 3-MCPDE in high-purity vitamin E products by more than 85% and 88%, respectively. CN201910616771.6 provides a method for reducing 3-MCPDE in oils, including adding an alkaline catalyst when the oil is heated to a first temperature and passing an inert gas under non-vacuum conditions, which can ultimately control the 3-MCPD content to below 0.40 mg / kg. CN201610392375.6 discloses a method for heating a sample at 220–280 ℃ with the addition of trace amounts of iron ions for 30–50 minutes, which significantly reduces the 3-MCPDE content in oils.

[0005] Although these research findings provide rich theoretical and technological basis for the formation mechanism and control of 3-MCPD / 3-MCPDE, there are still several key shortcomings: for example, most studies focus on bulk raw materials such as palm oil or vegetable oil, while no research has been conducted on special oils with high DAG content, and these methods are not applicable to the formation process of DAG. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing diacylglycerol oils by blocking the formation of 3-chloropropanediol ester using a controllable-release chloride ion shielding agent. This method addresses the problem of 3-MCPDE easily forming during the high-temperature distillation stage of DAG production. By controlling the reaction sequence and thermally triggered chloride capture, free chloride ions and the 3-MCPD ester precursor are captured at high temperatures, blocking their formation pathway and thus obtaining a high-purity, low-risk, safe, and stable DAG oil product.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a diacylglycerol oil that blocks the formation of 3-chloropropanediol ester, comprising the following steps: (1) Raw material pretreatment: The raw oil is degummed by the citric acid-glycerol-phospholipase system to remove chloride salts, metal impurities and some polar impurities. After the reaction is completed, it is centrifuged to obtain low-chlorine clear oil. (2) Glycerol dehydrogenase reaction: Low-filtration oil, glycerol, immobilized lipase (Lipozyme RM IM) and immobilized monoglyceride lipase and a small amount of water are mixed and subjected to transesterification to obtain the reaction system; Simultaneously, immobilized monoglyceride lipase is added to selectively catalyze the conversion of MAG to DAG or glycerol, prevent the accumulation of MAG intermediates (MAG ≤ 2 wt%), and reduce the level of 3-MCPD precursor.

[0008] (3) Addition of controlled-release chloride ion shielding agent: Separate and immobilize the enzyme in the reaction system, add controlled-release chloride ion shielding agent after heating, and react with the temperature to obtain crude product; (4) Molecular distillation: Under a nitrogen protective atmosphere, the crude product is subjected to two-step molecular distillation to obtain DAG oil; (5) Post-processing: The DAG oil obtained after distillation is desolventized under vacuum to remove trace amounts of solvent residue; then filtered to obtain DAG oil products.

[0009] Preferably, in step (1), the raw material oil is soybean oil, rapeseed oil, or palm oil; in the citrate-glycerol-phospholipase system, the citrate concentration is 0.05–0.15 wt%; the glycerol addition is 3–6 wt%; the phospholipase (Phospholipase A1 or A2) addition is 0.05–0.1 wt% based on phospholipid content; and the water content is 1–3 wt%.

[0010] Preferably, in step (1), the degumming process is carried out at a temperature of 55–65°C and a stirring speed of 200–300 rpm for 30–45 min.

[0011] Preferably, in step (2), the molar ratio of low-filtration oil to glycerol is 1:1–3; the amount of immobilized lipase (Lipozyme RM IM, derived from Rhizomucor miehei) added is 5–10 wt% based on the total mass of the reaction system; the immobilized monoglyceride lipase accounts for 2–4% of the total mass of the reaction system; and the water content of the reaction system is controlled at 1–3 wt%.

[0012] Preferably, in step (2), the conditions for the transesterification reaction are: vacuum degree: –0.08 MPa, stirring speed: 200–250 rpm; reaction temperature: 55–80 ℃, reaction time: 4–6 h.

[0013] Preferably, in step (3), the reaction system is heated to 100-110℃; the amount of the shielding agent added is 0.2-0.5 wt% of the total mass of the system; the core of the shielding agent is thiourea, guanidine ethylamine or cysteine, and the shell is polyethylene glycol-polyamide copolymer.

[0014] Preferably, in step (3), the reaction is carried out by heating to 130–150 °C and maintaining it for 0.5–1 h.

[0015] Preferably, in step (4), the specific process of molecular distillation is as follows: first, light components are removed at 150–180 °C and 0.01–0.05 mbar; then, DAG oil is purified at 200–230 °C and 0.01–0.05 mbar; the flow rate of nitrogen is 30–40 mL / min.

[0016] Preferably, in step (5), the vacuum desolvation conditions are –0.095 MPa, 90–100 ℃, for 30 min.

[0017] This invention achieves systematic inhibition of 3-MCPD and 3-MCPDE throughout the entire process of DAG oil preparation by reducing chloride ions at the source, controlling intermediates, and using thermal triggering shielding. Firstly, this invention employs a citrate-glycerol-phospholipase synergistic system, which, through acid complexation, esterification, and enzymatic decomposition, simultaneously removes free chloride ions and organochlorine sources bound to phospholipids, thus weakening the chloride source basis for 3-MCPD formation at its source. Secondly, during the glycerolysis stage, 3-MCPD is mainly composed of MAG and Cl... - Esterification / substitution reactions occur at high temperatures. This invention introduces an immobilized monoglyceride lipase (2–4 wt%) to selectively catalyze the conversion of MAG to DAG, significantly reducing the steady-state concentration of MAG in the system (controlled to ≤2 wt%). After glycerolysis and before molecular distillation, a controllable-release chloride ion shielding agent is added when the system is heated to 100–110 °C. The shielding agent employs a thermally responsive polymer shell (such as polyethylene glycol-polyamide copolymer), which melts and decomposes at 120–150 °C, releasing core amine / guanidinyl / thiol compounds. The released active groups can add to free Cl⁻ or 3-MCPDE to form stable complexes, thereby dynamically capturing reactive chloride sources during high-temperature distillation (150–230 °C) and blocking the key reaction pathway for 3-MCPDE formation.

[0018] The beneficial effects of this invention are as follows: (1) The preparation method provided by the present invention can reduce the 3-MCPDE content of the prepared product by more than 90%, and the final 3-MCPD < 0.1 mg / kg; ensure the quality of DAG oil: the purity of DAG in the product is ≥ 60 wt%, and the color is light and the flavor is clear; (2) The preparation process provided by the present invention is stable and controllable, and the addition time of the shielding agent is clearly defined, which can ensure that the release timing is accurate and does not interfere with enzyme catalysis; and all the components used are food-grade or biodegradable materials, with no risk of chemical residues. The capture agent and reaction products used in the present invention are all food-grade or biodegradable substances, which effectively avoids chemical residues. Detailed Implementation

[0019] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0020] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0021] In some embodiments, the shielding agent used in this invention is prepared by the following method: (a) Preparation of the core solution: Add 40 g of glycerol and 10 g of cysteine ​​to a 500 mL beaker, and stir until completely dissolved. Then add 10 g of emulsifier and stir until homogeneous. Keep at room temperature and protected from light for later use.

[0022] (b) Preparation of PEG-PA: Polyethylene glycol (molecular weight 2000) and ε-caprolactam were mixed at a mass ratio of 75:25 and polymerized at 150 °C for 3 h to obtain polyethylene glycol-polyamide copolymer.

[0023] (c) Shell preparation: Add 50 g of deionized water to a 1 L beaker. Weigh 200 g of PEG-PA, add it to the water, and stir until homogeneous to form a polymer solution. Maintain the temperature at 25–30 °C to ensure complete dissolution of the polymer.

[0024] (d) Embedding and mixing: The amount of core solution prepared in step (a) is slowly added to the amount of shell solution prepared in step (c) and stirred until homogeneous to form a homogeneous dispersion.

[0025] Preferably, high-speed shearing (5000–8000 rpm, 1–2 min) can be used to obtain a uniform particle size distribution (5–20 μm).

[0026] (e) Drying into powder: Samples are prepared by freeze drying. The dispersion is poured into a tray, pre-frozen at -20 ℃ for 1–2 h, and freeze-dried for 24–48 h to obtain powder.

[0027] In some embodiments, cysteamine can be replaced with guanethidine or thiourea during the preparation of the core solution.

[0028] In some embodiments, the emulsifier is Tween 80, sodium dodecyl sulfate, etc.

[0029] The low-chlorine oil prepared by this invention is mainly composed of a mixture of triglycerides (TAG). In practical use, when added according to a molar ratio, this molar ratio is an approximate design value. This invention uses the average molecular weight (Mw) of the oil, approximately 860 g / mol (a commonly used value for palm oil), as the conversion basis.

[0030] Example 1 (1) Raw material pretreatment: Take 1 kg of refined palm oil, add citric acid, glycerol and phospholipase. In the system, the concentration of citric acid is 15 wt%; the amount of glycerol added is 5 wt%; the amount of phospholipase (Phospholipase A1) added is 0.1 wt%, based on the phospholipid content; the water content is 3 wt%, at 55 ℃; the reaction time is 45 min; the stirring speed is maintained at 300 rpm; after the reaction, centrifuge (3000 rpm, 10 min) to remove the lower colloid and aqueous phase to obtain low-chlorine clear oil; (2) Glycerol DAG desorption reaction: Low-chlorinated oil and glycerol were mixed in a molar ratio of 1:2, and then 8 wt% (based on the total mass of the reaction system) of immobilized lipase (Lipozyme RM IM) and 3 wt% of immobilized monoglyceride lipase were added. The water content was controlled at 3 wt%. The transesterification reaction was carried out under vacuum of -0.08 MPa, stirring speed of 200 rpm, and reaction temperature of 55–60℃ for 5 h. (3) Thermally responsive chloride ion shielding agent: After the glycerol hydrolysis reaction is completed and the immobilized enzyme is separated, the temperature is raised to 100-110℃. During this stage, the system is still a low water content, weakly polar oil phase environment.

[0031] Subsequently, a controlled-release chloride ion shielding agent (0.5 wt% of the total mass of the system) was added, and the temperature was further increased to 130–150 °C and maintained for 1 h, so that the shell decomposed thermally and released the active components.

[0032] (4) Molecular distillation: Two-step molecular distillation is adopted to remove light components at 150 °C and 0.05 mbar; high-purity DAG oil is purified at 200 °C and 0.05 mbar; nitrogen protection (40 mL / min) is used to prevent oxidation.

[0033] (5) Post-processing: The DAG oil obtained after distillation was desolventized under vacuum (-0.095 MPa, 90–100 ℃, 30 min) to remove trace solvent residues; then filtered (0.45 μm) to remove microcapsule shell residues and complex particles generated by the reaction, and finally DAG oil product was obtained. The DAG purity of the product was 63.7 wt%, the 3-MCPDE content was 0.08 mg / kg, and it had high transparency and pure flavor.

[0034] Comparative Example 1 Preparation of DAG oils by conventional enzymatic glycerol hydrolysis (1) Raw material pretreatment: Take 1 kg of refined palm oil, add 3% (w / w) glycerol, 0.2% phospholipase A1 and 2% citric acid solution (0.05 mol / L) at 60 ℃, stir and react for 30 min to remove gum and phospholipids, wash twice with hot water, and dehydrate under vacuum for later use.

[0035] (2) Glycerol hydrolysis reaction: The pretreated oil and glycerol were added to the reaction vessel at a ratio of TAG:glycerol = 1:2 (molar ratio), and immobilized lipase Lipozyme RM IM (8 wt%) was added. The reaction temperature was 65 ℃, the vacuum was -0.08 MPa, the stirring was 200 rpm, and the reaction was carried out for 6 h.

[0036] (3) Enzyme separation and molecular distillation: After the reaction is completed, filter to remove the enzyme, heat to 180–230 °C for molecular distillation, use nitrogen flow rate of 30 mL / min, and collect the main fraction.

[0037] The obtained DAG purity was 55.4 wt%, and the 3-MCPDE content was 0.96 mg / kg.

[0038] Comparative Example 2 (1) The raw material pretreatment is the same as in Example 1; (2) Glycerol DAG desorption reaction: Low-chlorinated oil and glycerol were mixed in a molar ratio of 1:2, and then 8 wt% (based on the total mass of the reaction system) of immobilized lipase (Lipozyme RM IM) was added. At the same time, immobilized monoglyceride lipase (3 wt%) was added. After stirring evenly, 1 wt% ethanolamine was added as a chlorine scavenger. The water content was controlled at 3 wt%. The transesterification reaction was carried out under vacuum of -0.08 MPa, stirring speed of 200 rpm, and reaction temperature of 55–60℃ for 5 h. (3) Molecular distillation: Two-step molecular distillation is adopted. Light components are removed at 150 °C and 0.05 mbar. High-purity DAG oil is purified at 200 °C and 0.05 mbar. Nitrogen protection (40 mL / min) is used to prevent oxidation.

[0039] (4) Post-processing: The DAG oil obtained after distillation was desolventized under vacuum (-0.095 MPa, 90–100 ℃, 30 min) to remove trace solvent residues; then filtered (0.45 μm) to remove microcapsule shell residues and complex particles generated by the reaction, and finally DAG oil product was obtained. The DAG purity of the product was 56.2 wt%, and the 3-MCPDE content was 0.48 mg / kg.

[0040] Comparative Example 3 (1) Raw material pretreatment: Take 1 kg of refined palm oil, add citric acid, glycerol and phospholipase. In the system, the concentration of citric acid is 15 wt%; the amount of glycerol added is 5 wt%; the amount of phospholipase (Phospholipase A1) added is 0.1 wt%, based on the phospholipid content; the water content is 3 wt%, at 55 ℃; the reaction time is 45 min; the stirring speed is maintained at 300 rpm; after the reaction, centrifuge (3000 rpm, 10 min) to remove the lower colloid and aqueous phase to obtain low-chlorine clear oil; (2) Glycerol DAG desorption reaction: Low-chlorinated oil and glycerol were mixed in a molar ratio of 1:2, and then 8 wt% (based on the total mass of the reaction system) of immobilized lipase (Lipozyme RM IM) and 3 wt% of immobilized monoglyceride lipase were added. Controlled-release chloride ion shielding agent (added at 0.5 wt% of the total mass of the system) was added, and the water content was controlled at 3 wt%. The transesterification reaction was carried out under vacuum of -0.08 MPa, stirring speed of 200 rpm, and reaction temperature of 55–60℃ for 5 h. (3) Molecular distillation: Two-step molecular distillation is adopted. Light components are removed at 150 °C and 0.05 mbar. High-purity DAG oil is purified at 200 °C and 0.05 mbar. Nitrogen protection (40 mL / min) is used to prevent oxidation.

[0041] (4) Post-processing: The DAG oil obtained after distillation was desolventized under vacuum (-0.095 MPa, 90-100 ℃, 30 min) to remove trace solvent residues; then filtered (0.45 μm) to remove microcapsule shell residues and complex particles generated by the reaction, and finally DAG oil product was obtained with a DAG purity of 46.7 wt%.

Claims

1. A method for preparing a diacylglycerol oil that blocks the formation of 3-chloropropanediol ester, characterized in that, Includes the following steps: (1) Raw material pretreatment: The raw oil is degummed by the citric acid-glycerol-phospholipase system to remove chloride salts, metal impurities and some polar impurities. After the reaction is completed, it is centrifuged to obtain low-chlorine clear oil. (2) Glycerol dehydrogenase reaction: Low-filtration oil, glycerol, immobilized lipase and immobilized monoglyceride lipase and a small amount of water are mixed and subjected to transesterification reaction to obtain the reaction system; (3) Addition of controlled-release chloride ion shielding agent: Separate and immobilize the enzyme in the reaction system, add controlled-release chloride ion shielding agent after heating, and react with the temperature to obtain crude product; (4) Molecular distillation: Under a nitrogen protective atmosphere, the crude product is subjected to two-step molecular distillation to obtain DAG oil; (5) Post-processing: The DAG oil obtained after distillation is desolventized under vacuum to remove trace amounts of solvent residue; then filtered to obtain DAG oil products.

2. The preparation method according to claim 1, characterized in that, In step (1), the raw material oil is soybean oil, rapeseed oil, corn oil or palm oil; in the citrate-glycerol-phospholipase system, the citrate concentration is 0.05–0.15 wt%; the glycerol addition is 3–6 wt%; the phospholipase addition is 0.05–0.1 wt% based on phospholipid content; and the water content is 1 wt%–3 wt%.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the degumming process is carried out at a temperature of 55–65℃ and a stirring speed of 200–300 rpm for 30–45 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of low-filtration oil to glycerol is 1:1–3; the amount of immobilized lipase added is 5–10 wt% based on the total mass of the reaction system; the immobilized monoglyceride lipase accounts for 2–4% of the total mass of the reaction system; and the water content of the reaction system is controlled at 1–3 wt%.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the conditions for the transesterification reaction are: vacuum degree: –0.08 MPa, stirring speed: 200–250 rpm; reaction temperature: 55–80 ℃, reaction time: 4–6 h.

6. The preparation method according to claim 1, characterized in that, In step (3), the reaction system is heated to 100-110℃; the amount of the shielding agent added is 0.2-0.5 wt% of the total mass of the system; the core of the shielding agent is thiourea, guanidine ethylamine or cysteine, and the shell is polyethylene glycol-polyamide copolymer.

7. The preparation method according to claim 1 or 6, characterized in that, In step (3), the reaction is carried out by heating to 130–150 °C and maintaining the temperature for 0.5–1 h.

8. The preparation method according to claim 1, characterized in that, In step (4), the specific process of molecular distillation is as follows: first, light components are removed at 150–180 ℃ and 0.01–0.05 mbar; then, DAG oil is purified at 200–230 ℃ and 0.01–0.05 mbar; the flow rate of nitrogen is 30–40 mL / min.

9. The preparation method according to claim 1, characterized in that, In step (5), the vacuum desolvation conditions are -0.095 MPa, 90–100 ℃, and treatment for 30 min.