A method for separating organic chlorine and free fatty acid in rice bran crude oil

Abstract

This invention belongs to the field of rice bran oil refining technology, specifically relating to a method for separating organochlorines and free fatty acids from crude rice bran oil. The method includes: adding crude rice bran oil to a mixed solution for multi-stage countercurrent extraction, monitoring the content of organochlorines in the heavy phase during extraction; separating the heavy and light phases, concentrating the light phase, dissolving it in ether, then adding water and liquid alkali to remove residual acid value; finally, dewaxing, decolorizing, and deodorizing to obtain refined crude rice bran oil. This invention employs a specific water and alcohol mixed solution and a low-temperature multi-stage extraction process, which can simultaneously and efficiently remove organochlorines, free fatty acids, and monoglycerides from crude rice bran oil, significantly reducing the content of organochlorines and removing monoglycerides without generating secondary harmful substances. The process is mild and environmentally friendly, with controllable parameters, suitable for industrial-scale rice bran oil refining production, and can significantly improve product safety and added value.

Description

Technical Field

[0001] This invention belongs to the field of rice bran oil refining technology, specifically relating to a method for separating organochlorine and free fatty acids from rice bran oil. Background Technology

[0002] Crude rice bran oil is a high-quality edible oil extracted from rice bran. Rich in unsaturated fatty acids, oryzanol, vitamins, and other nutrients, it has broad application prospects in food processing and daily consumption. With consumers' increasing demands for food safety and quality, optimizing the refining process of crude rice bran oil has become a key research focus in the oil processing industry. Removing harmful impurities and regulating oil composition to improve product safety and stability are core technological requirements in the refining process.

[0003] During the production and processing of crude rice bran oil, it contains not only conventional impurities such as free fatty acids, monoglycerides, diglycerides, and gums, but also potentially organochlorine impurities due to pesticide use during cultivation and environmental contact during processing. These organochlorine impurities specifically refer to chlorinated pesticide impurities detectable by microcoulometric methods, distinct from inorganic chlorine and chloride ions. Organochlorine impurities are characterized by strong residues and potential health hazards; if not effectively removed, they will seriously affect the edible safety of crude rice bran oil. The presence of monoglycerides and diglycerides reduces the oxidative stability of crude rice bran oil, shortening its shelf life. Furthermore, they may react with other components during subsequent deodorization processes to generate additional harmful substances such as chloropropanol esters and glycidyl esters, further impacting product quality.

[0004] Currently, various technologies for treating common impurities have been developed in the field of oil refining. Among them, alcohol-water extraction is widely used for the separation and removal of some impurities in oils due to its advantages such as simple operation, easy solvent recovery, and environmental friendliness. Existing technologies, including relevant literature and patents, disclose technical solutions for separating free fatty acids, glycerol diesters, chloropropanol esters, and glycidyl esters from oils using alcohol-water extraction. By controlling the extraction conditions, the above impurities can be separated from triglycerides (the main active components of oils), thereby improving the purity of the oils.

[0005] However, existing alcohol-water extraction technology and other rice bran oil refining technologies have significant limitations: First, systematic research on the pollution problem of the aforementioned specific organochlorine impurities in rice bran oil has not been conducted domestically or internationally, and there is currently no clear removal method. Existing refining processes (such as deodorization and decolorization) cannot effectively reduce the content of these organochlorine impurities, leading to potential safety risks for the consumption of rice bran oil. Second, existing alcohol extraction technology only focuses on the removal of impurities such as free fatty acids and glycerol diesters, and does not mention the extraction and separation effect on monoglycerides, thus failing to achieve the synergistic removal of organochlorines and monoglycerides simultaneously. In addition, some existing technologies use deodorization processes to remove components such as monoglycerides, but the high-temperature environment of the deodorization process may cause organochlorines to undergo condensation reactions with monoglycerides and triglycerides, which not only reduces the efficiency of impurity removal but may also generate new harmful substances, affecting product safety.

[0006] Therefore, developing a refining technology that can simultaneously and efficiently remove organochlorines, monoglycerides, and some conventional impurities from crude rice bran oil, while ensuring safe operation and preventing secondary pollution, and solving problems such as the lack of organochlorine removal, poor separation of monoglycerides, and safety risks caused by high-temperature processing in existing technologies, has become a critical technological bottleneck that urgently needs to be overcome in the current field of crude rice bran oil refining. Summary of the Invention

[0007] Based on the above technical background, the main objective of this invention is to provide a method for separating organochlorine and free fatty acids from crude rice bran oil, so as to overcome the shortcomings of the prior art.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] This invention provides a method for separating organochlorine compounds and free fatty acids from crude rice bran oil, the method comprising the following steps: Step 1: Add crude rice bran oil to the mixed solution for multi-stage countercurrent extraction. During the extraction process, monitor the content of organochlorine in the heavy phase until the content of organochlorine in the heavy phase is less than 6 ppm, then separate the heavy phase and the light phase. Step 2: After concentrating the heavy phase, dissolve it in ether, then add water and liquid alkali simultaneously for neutralization. Finally, after dewaxing, decolorizing and deodorizing, refined rice bran crude oil is obtained.

[0010] Terminology Explanation: Multistage Countercurrent Extraction Multistage countercurrent extraction is a continuous and efficient liquid-liquid extraction process. Its core lies in the countercurrent flow of two phases (heavy phase and light phase) through multiple extraction stages, allowing impurities (organochlorine, free fatty acids, etc.) to gradually transfer from crude rice bran oil (heavy phase) to the mixed solution (light phase). The specific process, in conjunction with this invention, is as follows: Heavy phase: Crude rice bran oil (containing organochlorine, free fatty acids, triglycerides, etc.) has a high density and is used as the heavy phase.

[0011] Light phase: A mixed solution of water and alcohol (ethanol, isopropanol, propanol, etc.), with a lower density, used as an extractant.

[0012] Initial mixing: Add the crude rice bran oil and the mixed solution to the first stage of a multi-stage countercurrent extraction device (such as a mixing and clarification tank, extraction tower, etc.) in a certain proportion (e.g., a volume ratio of 1:1 or adjusted according to the process), so that the heavy phase and the light phase begin to come into contact.

[0013] After completing multi-stage countercurrent extraction: Heavy phase: This is crude rice bran oil, which has undergone multi-stage countercurrent extraction and has significantly reduced levels of organochlorine, free fatty acids, and monoglycerides. It is discharged from the end of the extraction equipment and enters step 2 for subsequent refining (concentration, ether dissolution, alkali washing, dewaxing, decolorization, and deodorization in sequence).

[0014] Light phase: This is a mixed solution enriched with organochlorines, free fatty acids, monoglycerides, and some alcohols and water. It is discharged from the beginning of the extraction equipment and can be distilled to recover the mixed alcohols for recycling.

[0015] The steps described above are described in detail below.

[0016] In step 1, the mixed solution is obtained by mixing water and alcohol, and the volume ratio of water to alcohol is (5-35):(65-95).

[0017] Preferably, the volume ratio of water to alcohol is 20:80.

[0018] The alcohol is selected from one or more of methanol, ethanol, isopropanol, and propanol.

[0019] Preferably, the alcohol is a mixed alcohol obtained by mixing ethanol, isopropanol and propanol.

[0020] More preferably, the alcohol is a mixed alcohol obtained by mixing ethanol, isopropanol and propanol in a volume ratio of (1-3):(2-4):1.

[0021] For example, the alcohol is a mixture of ethanol, isopropanol, and propanol in a volume ratio of 2:3:1. Experiments have shown that the type and amount of alcohol used affect the extraction effect. Using a mixture of ethanol, isopropanol, and propanol in the above volume ratio as an extractant is beneficial for improving the removal of organochlorines and monoglycerides from crude rice bran oil.

[0022] The multi-stage countercurrent extraction is a 4-8 stage countercurrent extraction.

[0023] Preferably, the multi-stage countercurrent extraction is a 6-stage countercurrent extraction.

[0024] The conditions for the multi-stage countercurrent extraction are as follows: the temperature of the multi-stage countercurrent extraction is 20-50℃, the stirring is carried out during the extraction process for 1-10 min, and the standing time is 5-20 min.

[0025] Preferably, the conditions for the multi-stage countercurrent extraction are as follows: the temperature of the multi-stage countercurrent extraction is 40°C, the stirring is carried out during the extraction process for 5 minutes, and the standing time is 10 minutes.

[0026] During the extraction process, the content of organochlorine in the heavy phase is monitored until the content of organochlorine in the heavy phase is <6 ppm, and then the heavy phase and light phase are separated.

[0027] The mixed alcohol in the light phase is separated and recovered. The recovered mixed alcohol is then added to the crude rice bran oil for multi-stage countercurrent extraction to complete the recovery and utilization of the mixed alcohol.

[0028] In step 2, the amount of diethyl ether added is 1 to 10 times the volume of the concentrated heavy phase.

[0029] Preferably, the amount of diethyl ether added is 5 times the volume of the concentrated heavy phase.

[0030] The liquid alkali is selected from one or more of the following: sodium hydroxide aqueous solution, sodium carbonate aqueous solution, and potassium hydroxide aqueous solution.

[0031] Preferably, the liquid alkali is a mixed solution of sodium hydroxide aqueous solution and sodium carbonate aqueous solution.

[0032] More preferably, the liquid alkali is obtained by mixing an aqueous solution of sodium hydroxide and an aqueous solution of sodium carbonate in a volume ratio of (4-6):1.

[0033] For example, the liquid alkali is obtained by mixing an aqueous solution of sodium hydroxide and an aqueous solution of sodium carbonate in a volume ratio of 5:1.

[0034] The beneficial effects of this invention are as follows: (1) This invention utilizes a mixed solution obtained by mixing a specific alcohol and water in a certain ratio, combined with a multi-stage countercurrent extraction process, to specifically address the problem that existing refining technologies cannot effectively remove organochlorine pesticide impurities detectable by microcoulometric methods from crude rice bran oil. After treatment using the method described in this invention, the organochlorine content in refined crude rice bran oil can be reduced to 2-5 ppm, far lower than the level of existing processes, and can be stably controlled below the safety threshold, significantly improving the edible safety and quality of crude rice bran oil.

[0035] (2) Compared with the limitations of existing technologies that only focus on the removal of a single impurity, this invention can simultaneously and efficiently separate organochlorines, free fatty acids, and monoglycerides, while also having a certain removal effect on diglycerides. Among them, monoglycerides are basically completely removed, and the removal rate of free fatty acids is significantly improved. This effectively avoids the risk of monoglycerides and diglycerides reacting with organochlorines in subsequent processing to generate secondary harmful substances such as chloropropanol esters and glycidyl esters, while extending the shelf life of the product and solving the problems of single impurity removal and easy secondary pollution in existing technologies.

[0036] (3) This invention employs a low-temperature multi-stage countercurrent extraction process, which avoids the problem of harmful substance generation caused by the high-temperature environment of traditional deodorization processes, and retains natural nutrients such as oryzanol in crude rice bran oil to the maximum extent. The selected mixed alcohols, ethers and other solvents are easy to recycle and reuse. The mixed solution and liquid alkali system used in this invention are environmentally friendly, and the entire process produces no toxic or harmful byproducts. The operation is safe and controllable, which is in line with the industry development trend of green chemical and food processing.

[0037] (4) This invention strictly limits the range of key process parameters, such as the ratio of mixed solutions, the number of multi-stage countercurrent extraction stages and temperature, stirring / standing time, and liquid alkali ratio. Furthermore, the extraction endpoint can be accurately controlled by monitoring the content of organochlorine in the heavy phase, resulting in strong process stability and good repeatability. All equipment used is conventional equipment in the oil processing field, requiring no additional investment in specialized equipment, making it easy to achieve large-scale promotion and application.

[0038] (5) The refined rice bran oil processed by this method has the characteristics of low organic chlorine, low chloropropanol esters, low glycidyl esters, and low monoglyceride, and the acid value meets the standard and the quality is uniform. At the same time, the extraction process has a good retention effect on nutrients such as oryzanol, which further enhances the nutritional value and added value of the rice bran oil. Attached Figure Description

[0039] Figure 1 A process flow diagram of the method described in this invention is shown. Detailed Implementation

[0040] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0041] A method for separating organochlorine compounds and free fatty acids from crude rice bran oil, the method comprising the following steps: Step 1: Mix water and alcohol in a volume ratio of (5-35):(65-95) to obtain a mixed solution. The alcohol is a mixture of ethanol, isopropanol, and propanol in a volume ratio of (1-3):(2-4):1. Add crude rice bran oil to the mixed solution for multi-stage countercurrent extraction. The conditions for multi-stage countercurrent extraction are: the temperature is 20-50℃, stirring is performed during the extraction process for 1-10 min, and the settling time is 5-20 min. Monitor the content of organochlorine in the heavy phase during the extraction process. When the content of organochlorine in the heavy phase is lower than 6 ppm, separate the heavy phase and the light phase. Separate and recover the mixed alcohol in the light phase. Add the recovered mixed alcohol back to the crude rice bran oil for multi-stage countercurrent extraction to complete the recovery and utilization of the mixed alcohol.

[0042] Step 2: After concentrating the heavy phase, add ether to dissolve it. The amount of ether added is 1 to 10 times the volume of the concentrated heavy phase. Then, water and liquid alkali are added simultaneously for neutralization. The liquid alkali is obtained by mixing sodium hydroxide aqueous solution and sodium carbonate aqueous solution in a volume ratio of (4 to 6): 1. Finally, after dewaxing, decolorization and deodorization, refined rice bran crude oil is obtained.

[0043] Example The present invention is further illustrated below with specific examples. These embodiments are merely illustrative and not intended to limit the scope of the invention. All raw materials used in the embodiments of the present invention are commercially available.

[0044] Example 1 like Figure 1 As shown, water and alcohol were mixed at a volume ratio of 20:80 to obtain a mixed solution. The alcohol was a mixture of ethanol, isopropanol, and propanol at a volume ratio of 2:3:1. Crude rice bran oil was added to the mixed solution for a 6-stage countercurrent extraction using a conventional multi-stage countercurrent extractor. The temperature of the countercurrent extraction was 40°C. Stirring was performed during the extraction process for 5 minutes, followed by a settling time of 10 minutes. The content of organochlorine in the heavy phase was monitored during the extraction process until it was <6 ppm. The heavy and light phases were then separated. The light phase contained 200–300 ppm of organochlorine, free fatty acids, monoglycerides, diglycerides, and oryzanol. The heavy phase contained 5 ppm of organochlorine, 85% triglycerides, 5–8% diglycerides, 5–10% free fatty acids, and 2% oryzanol. The mixed alcohol in the light phase is separated and recovered. The recovered mixed alcohol is then added back to the crude rice bran oil for multi-stage countercurrent extraction to complete the recovery and utilization of the mixed alcohol.

[0045] The heavy phase is concentrated and dissolved in diethyl ether, with the amount of ether added being 5 times the volume of the concentrated heavy phase. Then, water and liquid alkali are added to remove the remaining acid value. The amounts of water and liquid alkali added are sufficient to completely remove the remaining acid value. The liquid alkali is obtained by mixing sodium hydroxide aqueous solution and sodium carbonate aqueous solution in a volume ratio of 5:1. Finally, the oil undergoes conventional oil refining processes for dewaxing, decolorization, and deodorization to obtain refined crude rice bran oil with low levels of organochlorine compounds, low levels of chloropropanol esters, and low levels of glycidyl esters.

[0046] Example 2 Water and alcohol were mixed at a volume ratio of 5:65 to obtain a mixed solution. The alcohol was a mixture of ethanol, isopropanol, and propanol at a volume ratio of 1:2:1. Crude rice bran oil was added to the mixed solution for a four-stage countercurrent extraction using a conventional multi-stage countercurrent extractor. The temperature of the countercurrent extraction was 20°C. Stirring was performed during the extraction process for 10 min, followed by a settling time of 20 min. The content of organochlorine in the heavy phase was monitored during the extraction process until it was <6 ppm. The heavy and light phases were then separated. The light phase contained 200–300 ppm of organochlorine, free fatty acids, monoglycerides, diglycerides, and oryzanol. The heavy phase contained 5 ppm of organochlorine, 85% triglycerides, 5–8% diglycerides, 5–10% free fatty acids, and 2% oryzanol. The mixed alcohol in the light phase was separated and recovered. The recovered mixed alcohol was then added back to the crude rice bran oil for another multi-stage countercurrent extraction to complete the recovery and reuse of the mixed alcohol.

[0047] The heavy phase is concentrated and dissolved in diethyl ether, with the amount of ether added being three times the volume of the concentrated heavy phase. Then, water and liquid alkali are added to remove the remaining acid value. The amounts of water and liquid alkali added are sufficient to completely remove the remaining acid value. The liquid alkali is obtained by mixing sodium hydroxide aqueous solution and sodium carbonate aqueous solution in a volume ratio of 4:1. Finally, the oil undergoes conventional oil refining processes for dewaxing, decolorization, and deodorization to obtain refined crude rice bran oil with low levels of organochlorine compounds, low levels of chloropropanol esters, and low levels of glycidyl esters.

[0048] Example 3 Water and alcohol were mixed at a volume ratio of 35:95 to obtain a mixed solution. The alcohol was a mixture of ethanol, isopropanol, and propanol at a volume ratio of 3:4:1. Crude rice bran oil was added to the mixed solution and subjected to an 8-stage countercurrent extraction using a conventional multi-stage countercurrent extractor. The temperature of the countercurrent extraction was 50°C. Stirring was performed during the extraction process for 3 minutes, followed by a settling time of 5 minutes. The content of organochlorine in the heavy phase was monitored during the extraction process until it was less than 6 ppm. The heavy and light phases were then separated. The light phase contained 200–300 ppm of organochlorine, free fatty acids, monoglycerides, diglycerides, and oryzanol. The heavy phase contained 5 ppm of organochlorine, 85% triglycerides, 5–8% diglycerides, 5–10% free fatty acids, and 2% oryzanol. The mixed alcohol in the light phase was separated and recovered. The recovered mixed alcohol was then added back to the crude rice bran oil for multi-stage countercurrent extraction to complete the recovery and reuse of the mixed alcohol.

[0049] The heavy phase is concentrated and dissolved in diethyl ether, with the amount of ether added being 10 times the volume of the concentrated heavy phase. Then, water and liquid alkali are added to remove the remaining acid value. The amounts of water and liquid alkali added are sufficient to completely remove the remaining acid value. The liquid alkali is obtained by mixing sodium hydroxide aqueous solution and sodium carbonate aqueous solution in a volume ratio of 6:1. Finally, the oil undergoes conventional oil refining processes for dewaxing, decolorization, and deodorization to obtain refined crude rice bran oil with low levels of organochlorine compounds, low levels of chloropropanol esters, and low levels of glycidyl esters.

[0050] Example 4 The separation of organochlorine and free fatty acids in crude rice bran oil was carried out in a manner similar to that in Example 1, except that the alcohol was a mixture of ethanol and isopropanol in a volume ratio of 2:3.

[0051] Example 5 The separation of organochlorine and free fatty acids in crude rice bran oil was carried out in a manner similar to that in Example 1, except that the alcohol was a mixture of isopropanol and propanol in a volume ratio of 3:1.

[0052] Example 6 The separation of organochlorine and free fatty acids in crude rice bran oil was carried out in a manner similar to that in Example 1, except that the alcohol was a mixture of ethanol and propanol in a volume ratio of 2:1.

[0053] Example 7 The separation of organochlorine and free fatty acids in crude rice bran oil was carried out in a manner similar to that in Example 1, except that the alcohol was isopropanol.

[0054] Comparative Example Comparative Example 1 The separation of organochlorine and free fatty acids in crude rice bran oil was carried out in a manner similar to that in Example 1, except that the crude rice bran oil was added to a mixed solution for single-stage extraction.

[0055] Experimental Example Experimental Example 1: Test of Organochlorine and Glyceryl Monoester Content The contents of organochlorine compounds and monoglycerides in crude rice bran oil before and after extraction in Examples 1-7 and Comparative Example 1 were tested. The testing standard for organochlorine compounds was GB / T 5009.19-2008 "Determination of Multi-component Residues of Organochlorine Pesticides in Food", and the testing standard for monoglycerides was GB / T 46928-2025 HPSEC method. The test results are shown in Table 1.

[0056] Table 1. Content Tests for Organochlorines and Glyceryl Monoesters

[0057] As can be seen from Table 1, in Examples 1-7, the content of organochlorine after extraction was significantly reduced, and the content of organochlorine after deodorization was further reduced. Compared with Example 1, the decrease in organochlorine content after extraction in Examples 4-7 was less than that in Example 1, indicating that the type of alcohol has a significant impact on the extraction effect. The extraction effect of using a single alcohol or a mixture of two alcohols is lower than that of using a composite alcohol obtained by mixing ethanol, isopropanol, and propanol. When the alcohols are ethanol, isopropanol, and propanol mixed in a volume ratio of 2:3:1, the extraction effect is the best and most conducive to reducing the content of organochlorine after extraction.

[0058] Compared with Examples 1 to 3, the organochlorine content decreased the most after extraction in Example 1, indicating that the volume ratio of various alcohols in the complex alcohol has a significant impact on the content of organochlorine after extraction. When ethanol, isopropanol and propanol are mixed in a volume ratio of 2:3:1, the extraction effect is better and more conducive to reducing the content of organochlorine after extraction.

[0059] Compared with Example 1, Comparative Example 1 adjusted the extraction method to single-stage extraction. The reduction of organochlorine content after extraction in Comparative Example 1 was less than that in Example 1, indicating that the extraction method has a greater impact on the extraction effect of organochlorine in this invention. Using multi-stage countercurrent extraction is more conducive to efficiently reducing the organochlorine content in crude rice bran oil.

[0060] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for separating organochlorine compounds and free fatty acids from crude rice bran oil, characterized in that, The method includes the following steps: Step 1: Add crude rice bran oil to the mixed solution for multi-stage countercurrent extraction. During the extraction process, monitor the content of organochlorine in the heavy phase until the content of organochlorine in the heavy phase is less than 6 ppm, then separate the heavy phase and the light phase. Step 2: After concentrating the heavy phase, dissolve it in ether, then add water and liquid alkali simultaneously for neutralization. Finally, after dewaxing, decolorizing and deodorizing, refined rice bran crude oil is obtained.

2. The method according to claim 1, characterized in that, In step 1, The mixed solution is obtained by mixing water and alcohol, wherein the volume ratio of water to alcohol is (5-35):(65-95).

3. The method according to claim 1, characterized in that, In step 1, The alcohol is selected from one or more of methanol, ethanol, isopropanol, and propanol.

4. The method according to claim 3, characterized in that, In step 1, The alcohol is a mixture of ethanol, isopropanol and propanol.

5. The method according to claim 4, characterized in that, In step 1, The alcohol is a mixture of ethanol, isopropanol and propanol in a volume ratio of (1-3):(2-4):

1.

6. The method according to claim 1, characterized in that, In step 1, The multi-stage countercurrent extraction is a 4-8 stage countercurrent extraction; The conditions for the multi-stage countercurrent extraction are as follows: the temperature of the multi-stage countercurrent extraction is 20-50℃, the stirring is carried out during the extraction process for 1-10 min, and the standing time is 5-20 min.

7. The method according to claim 1, characterized in that, In step 2, The amount of diethyl ether added is 1 to 10 times the volume of the concentrated heavy phase.

8. The method according to claim 1, characterized in that, In step 2, The liquid alkali is selected from one or more of the following: sodium hydroxide aqueous solution, sodium carbonate aqueous solution, and potassium hydroxide aqueous solution.

9. The method according to claim 8, characterized in that, In step 2, The liquid alkali is a mixed solution of sodium hydroxide aqueous solution and sodium carbonate aqueous solution.

10. The method according to claim 9, characterized in that, In step 2, The liquid alkali is obtained by mixing sodium hydroxide aqueous solution and sodium carbonate aqueous solution in a volume ratio of (4-6):1.

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