A method for eliminating glycidyl esters in diglyceride vegetable oils

Abstract

This invention relates to the field of oil processing technology, specifically to a method for eliminating glycidyl esters in diglyceride vegetable oil. The method includes: Step 1: heating crude vegetable oil to 70-80°C and mixing it evenly with silica, then maintaining the temperature to obtain a first mixture; Step 2: reacting the first mixture, a diluted glycerol solution, and immobilized lipase in a vacuum environment to obtain a first reaction solution; Step 3: adding a polar solvent to the first reaction solution and then sequentially performing primary filtration, cooling, and secondary filtration to obtain diglyceride vegetable oil. This invention utilizes silica to adsorb impurities in crude vegetable oil, and reacts the silica-containing first mixture, the diluted glycerol solution, and the immobilized lipase in a vacuum environment, thereby lowering the reaction temperature and promoting the forward enzymatic hydrolysis of glycerol.

Description

Technical Field

[0001] This invention relates to the field of oil processing technology, and specifically to a method for eliminating glycidyl esters from diglyceride vegetable oils. Background Technology

[0002] Diacylglycerol (DAG) is a type of triglyceride in which one fatty acid is replaced by a hydroxyl group. DAG is a trace component of natural plant oils and an endogenous intermediate product of fat metabolism in the human body. Dietary DAG has the effects of reducing visceral fat, inhibiting weight gain, and lowering blood lipids, and has received much attention in recent years, finding wide application in various fields such as food, medicine, and chemicals (cosmetics).

[0003] The biggest difference between diglyceride edible oils and traditional edible oils lies in their high diglyceride content. The synthesis of diglycerides includes chemical and enzymatic methods. The chemical method primarily uses an alkaline catalyst to induce glycerol and oil to undergo glycerolysis. While the chemical method has a simple reaction route, is relatively quick, and inexpensive, it requires precise control of reaction conditions. Improper control of temperature, pH, and time can lead to side reactions that increase the content of impurities such as glycidyl esters, affecting not only the quality of the diglyceride edible oil but also posing a threat to human health. Enzyme catalysis is characterized by mild reaction conditions and high product yields. It mainly includes direct esterification, hydrolysis, alcoholysis, and glycerol hydrolysis. Direct esterification uses glycerol and fatty acids as raw materials to synthesize mono- and diglycerides under the action of a catalyst. Direct esterification has advantages such as high purity and high synthesis efficiency; however, glycerol and fatty acids generally come from the decomposition of triglycerides, resulting in relatively high raw material costs. Hydrolysis uses lipases to directly hydrolyze triglycerides. While the hydrolysis reaction is reversible, the degree of hydrolysis is difficult to precisely control, and this method readily generates monoglycerides and free triglycerides during diglyceride synthesis. Fatty acids and other byproducts result in poor reaction selectivity. Oil alcoholysis uses lipase to catalyze the reaction of lower alcohols and triglycerides to produce mono- and diglycerides. Alcoholysis typically requires the addition of large amounts of ethanol, leading to high raw material costs. Furthermore, ethanol is flammable and poses a high potential risk. Glycerolysis, on the other hand, utilizes the redistribution of fatty acid acyl groups between oil molecules and free glycerol molecules to synthesize mono- and diglycerides with specific structures. Glycerolysis does not result in mass loss and has lower costs. However, because glycerolysis is a reversible reaction, diglycerides in the substrate vegetable oil not only affect the degree of reaction but can also be converted into glycidyl esters under certain conditions. Summary of the Invention

[0004] To address the problem that diglycerides in the substrate vegetable oil can be converted into glycidyl esters under certain conditions during the enzyme-catalyzed synthesis of diglycerides, this invention provides a method for eliminating glycidyl esters in vegetable oils containing diglycerides. The method utilizes silica to adsorb impurities in the crude vegetable oil. A first mixture containing silica, a diluted glycerol solution, and an immobilized lipase are reacted in a vacuum environment. This process lowers the reaction temperature while promoting the forward enzymatic hydrolysis of glycerol.

[0005] The technical solution of the present invention is as follows: A method for eliminating glycidyl esters from diglyceride vegetable oils, comprising the following steps: Step 1: Heat the crude vegetable oil to 70-80℃ and mix it evenly with silica. Then, keep it at the temperature for a reaction to obtain the first mixture. Step 2: React the first mixture, the diluted glycerol solution, and the immobilized lipase in a vacuum environment to obtain the first reaction solution; Step 3: After adding a polar solvent to the first reaction solution, perform primary filtration, cooling, and secondary filtration in sequence to obtain diglyceride vegetable oil.

[0006] Furthermore, in step one, the mass of silica is 2%-3.5% of the mass of the crude vegetable oil. Silica can not only adsorb impurities in the crude vegetable oil, but also promote the enzymatic hydrolysis of glycerol towards the formation of diglycerides.

[0007] Furthermore, in step one, the heat preservation reaction time is 8-10 hours.

[0008] Furthermore, in step two, the concentration of the glycerol dilution is 50wt%-80wt%.

[0009] Furthermore, in step two, the immobilized lipase is either Lipozyme RM IM or Lipozyme TL IM.

[0010] Furthermore, in step two, the diluent for the glycerol is water and / or ethanol.

[0011] Furthermore, in step two, the mass ratio of the first mixture, the glycerol dilution, and the immobilized lipase is 3-12:1-2:0.015-0.03.

[0012] Furthermore, in step three, the polar solvent is methanol or ethanol.

[0013] Furthermore, in step three, the cooling temperature is -10 to 30°C. After adding a polar solvent to the first reaction solution, a primary filtration is performed to remove insoluble substances from the reaction system, yielding a crude product of diglyceride vegetable oil. Cooling the crude product of diglyceride vegetable oil facilitates the crystallization and precipitation of diglycerides, separating them from glycidyl esters.

[0014] Furthermore, it also includes step four, molecular distillation of the diglyceride vegetable oil.

[0015] The beneficial effects of this invention are as follows: This invention provides a method for eliminating glycidyl esters in diglyceride vegetable oil. Using crude corn oil, which has a wide availability and relatively high oil yield, as the starting material, the method involves heating the crude corn oil before the glycerol enzymatic hydrolysis reaction. This improves the fluidity of the crude corn oil and enhances the adsorption efficiency of silica for impurities in the crude corn oil. Furthermore, reacting a first mixture containing silica, a diluted glycerol solution, and immobilized lipase in a vacuum environment lowers the reaction temperature, increases the reaction rate, and promotes the forward progress of the glycerol enzymatic hydrolysis reaction. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0017] Example 1 A method for eliminating glycidyl esters from diglyceride corn oil includes the following steps: Step 1: Heat the crude corn oil to 70℃ and mix it evenly with silica. Then, keep the mixture at this temperature for 8 hours to obtain the first mixture. The mass of silica is 3.5% of the mass of the crude corn oil.

[0018] Step 2: The first mixture, the glycerol diluent, and the immobilized lipase were reacted in a vacuum environment at 60°C for 3.5 h to obtain the first reaction solution. The concentration of the glycerol diluent was 50 wt%, the diluent for the glycerol diluent was water, and the immobilized lipase was Lipozyme RM IM. The mass ratio of the first mixture, the glycerol diluent, and the immobilized lipase was 3:2:0.015.

[0019] Step 3: After adding ethanol to the first reaction solution, the mixture is subjected to primary filtration, cooling, and secondary filtration to obtain diglyceride corn oil. The cooling temperature is 30℃. The content of glycidyl esters in the diglyceride corn oil is 13 μg / kg.

[0020] Example 2 A method for eliminating glycidyl esters from diglyceride corn oil includes the following steps: Step 1: Heat the crude corn oil to 80℃ and mix it evenly with silica. Then, keep the mixture at this temperature for 8 hours to obtain the first mixture. The mass of silica is 2% of the mass of the crude corn oil.

[0021] Step 2: The first mixture, the glycerol diluent, and the immobilized lipase were reacted in a vacuum environment at 65°C for 2.5 h to obtain the first reaction solution. The concentration of the glycerol diluent was 80 wt%, the diluent for the glycerol diluent was ethanol, and the immobilized lipase was Lipozyme TL IM. The mass ratio of the first mixture, the glycerol diluent, and the immobilized lipase was 12:2:0.03.

[0022] Step 3: After adding ethanol to the first reaction solution, the mixture is subjected to primary filtration, cooling, and secondary filtration to obtain diglyceride corn oil. The cooling temperature is 10℃.

[0023] Step four: Molecular diglyceride corn oil is subjected to diglyceride distillation. The glycidyl ester content in the diglyceride corn oil is 8 μg / kg.

[0024] Example 3 A method for eliminating glycidyl esters from olive oil, comprising the following steps: Step 1: Heat the crude olive oil to 76℃ and mix it evenly with silica. Then, keep the mixture at this temperature for 8 hours to obtain the first mixture. The mass of silica is 2.6% of the mass of the crude olive oil.

[0025] Step 2: The first mixture, the glycerol dilution, and the immobilized lipase were reacted in a vacuum environment at 62°C for 3.0 h to obtain the first reaction solution. The concentration of the glycerol dilution was 70 wt%, the diluent for the glycerol dilution was ethanol, and the immobilized lipase was Lipozyme TL IM. The mass ratio of the first mixture, the glycerol dilution, and the immobilized lipase was 10:1:0.02.

[0026] Step 3: After adding ethanol to the first reaction solution, the mixture is subjected to primary filtration, cooling, and secondary filtration to obtain diglyceride olive oil. The cooling temperature is 22℃.

[0027] Step four: Molecular diglyceride olive oil is subjected to diglyceride distillation. The glycidyl ester content in the diglyceride olive oil is 7 μg / kg.

[0028] Example 4 A method for eliminating glycidyl esters from diglyceride rice bran oil includes the following steps: Step 1: Heat the crude rice bran oil to 78℃ and mix it evenly with silica. Then, keep the mixture at this temperature for 8 hours to obtain the first mixture. The mass of silica is 3% of the mass of the crude rice bran oil.

[0029] Step 2: The first mixture, the glycerol dilution, and the immobilized lipase were reacted in a vacuum environment at 65°C for 2.5 h to obtain the first reaction solution. The concentration of the glycerol dilution was 80 wt%, the diluent for the glycerol dilution was ethanol, and the immobilized lipase was Lipozyme RM IM. The mass ratio of the first mixture, the glycerol dilution, and the immobilized lipase was 5:1:0.018.

[0030] Step 3: After adding ethanol to the first reaction solution, the mixture is subjected to primary filtration, cooling, and secondary filtration to obtain diglyceride rice bran oil. The cooling temperature is 20℃.

[0031] Step four: Molecular diglyceride rice bran oil is subjected to diglyceride distillation. The glycidyl ester content in the diglyceride rice bran oil is 10 μg / kg.

[0032] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for eliminating glycidyl esters from diglyceride vegetable oils, characterized in that, Includes the following steps: Step 1: Heat the crude vegetable oil to 70-80℃ and mix it evenly with silica. Then, keep it at the temperature for a reaction to obtain the first mixture. Step 2: React the first mixture, the diluted glycerol solution, and the immobilized lipase in a vacuum environment to obtain the first reaction solution; Step 3: After adding a polar solvent to the first reaction solution, perform primary filtration, cooling, and secondary filtration in sequence to obtain diglyceride vegetable oil.

2. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step one, the mass of silica is 2%-3.5% of the mass of the crude vegetable oil.

3. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step one, the heat preservation reaction time is 8-10 hours.

4. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step two, the concentration of the glycerol dilution is 50wt%-80wt%.

5. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step two, the immobilized lipase is either Lipozyme RM IM or Lipozyme TL IM.

6. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step two, the diluent for the glycerol is water and / or ethanol.

7. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step two, the mass ratio of the first mixture, the glycerol dilution, and the immobilized lipase is 3-12:1-2:0.015-0.

03.

8. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step three, the polar solvent is methanol or ethanol.

9. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, In step three, the cooling temperature is -10 to 30°C.

10. The method for eliminating glycidyl esters in diglyceride vegetable oil as described in claim 1, characterized in that, It also includes step four, molecular distillation of diglyceride vegetable oil.