Process for the deodorization of rice bran oil with control of glycidyl ester formation
By combining compound chelation pretreatment and gradient pressure swing deodorization with low-temperature plasma treatment, the problem of GEs generation during rice bran oil deodorization was solved, achieving effective control of GEs and ensuring the quality of rice bran oil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU KANG ZHI YUAN GRAIN & OIL
- Filing Date
- 2025-07-25
- Publication Date
- 2026-05-12
AI Technical Summary
In existing rice bran oil deodorization processes, the formation of glycidyl esters (GEs) is difficult to control, affecting the flavor and stability of the oil. Furthermore, conventional methods have limited effectiveness or introduce new impurities.
A combined process of composite chelation pretreatment, gradient pressure swing deodorization, and low-temperature plasma posttreatment is adopted, including the use of chelating agents such as citric acid, phytic acid, and disodium ethylenediaminetetraacetate, combined with gradient pressure swing deodorization and low-temperature plasma treatment to decompose residual GEs.
It significantly reduces the formation of GEs, controlling it below 0.5 mg/kg, ensuring the flavor and stability of rice bran oil, making it suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of rice bran oil processing, and more specifically, to a deodorization process for rice bran oil that controls the formation of glycidyl esters. Background Technology
[0002] Rice bran oil is a highly nutritious vegetable oil, rich in unsaturated fatty acids, vitamin E, and other nutrients. Deodorization is a crucial refining step in the production of rice bran oil, primarily aimed at removing off-odor substances and improving its flavor and stability. However, the deodorization process is usually carried out at high temperatures, which leads to the formation of glycidyl esters (GEs) in the rice bran oil. GEs are potentially harmful substances that pose certain risks to human health; therefore, effectively controlling GE formation during deodorization is a critical issue in rice bran oil production.
[0003] In existing technologies, methods such as lowering deodorization temperature, shortening deodorization time, and increasing vacuum level are commonly used to control the formation of GEs. However, these methods often affect the deodorization effect, resulting in poor flavor and stability of rice bran oil. In addition, adding antioxidants can also inhibit GE formation, but the effect is limited and may introduce new impurities. Therefore, developing a rice bran oil deodorization process that can effectively control GE formation while ensuring deodorization efficiency is of significant practical importance. Summary of the Invention
[0004] The main objective of this application is to provide a rice bran oil deodorization process that controls the formation of glycidyl esters, overcoming the shortcomings of existing technologies where the formation of GEs is difficult to control during the rice bran oil deodorization process.
[0005] To achieve the above objectives, in a first aspect, this application provides a rice bran oil deodorization process for controlling the formation of glycidyl esters, comprising the following steps:
[0006] (1) Compound chelation pretreatment: The decolorized rice bran oil is sent into a pretreatment tank, a compound chelating agent is added, and pretreatment is carried out at a certain temperature and stirring speed.
[0007] (2) Gradient pressure swing deodorization: The rice bran oil treated in step (1) is sent into the deodorization tower for gradient pressure swing deodorization treatment, and the temperature, time and vacuum changes during the deodorization process are controlled.
[0008] (3) Low-temperature plasma post-treatment: The rice bran oil after deodorization in step (2) is introduced into a low-temperature plasma treatment device for low-temperature plasma treatment;
[0009] (4) Cooling and filtration: Cool the rice bran oil processed in step (3) to a certain temperature and filter it to obtain the finished rice bran oil.
[0010] Optionally, the composite chelating agent in step (1) is prepared by compounding citric acid, phytic acid and disodium ethylenediaminetetraacetate in a mass ratio of (1-3):(1-2):(0.5-1), and the amount of the composite chelating agent added is 0.03-0.08% of the mass of rice bran oil.
[0011] Optionally, in step (1), the pretreatment temperature is 50-70℃, the stirring speed is 100-200r / min, and the pretreatment time is 15-30min.
[0012] Optionally, the gradient pressure swing deodorization in step (2) is as follows: first, the vacuum degree in the deodorization tower is controlled at 1-2 mmHg, the temperature is raised to 200-220℃, and maintained for 10-15 min; then the vacuum degree is reduced to 0.5-1 mmHg, the temperature is raised to 220-240℃, and maintained for 20-30 min; finally, the vacuum degree is raised to 1-2 mmHg, the temperature is reduced to 200-210℃, and maintained for 5-10 min.
[0013] Optionally, in step (2), purified nitrogen gas is introduced during the deodorization process. The purity of the nitrogen gas is ≥99.99%, and the amount introduced is 6-10% of the mass of the rice bran oil.
[0014] Optionally, in step (3), the power of the low-temperature plasma treatment is 100-300W, the treatment time is 5-15min, and the vacuum degree during treatment is 10-30Pa.
[0015] Optionally, during the low-temperature plasma treatment in step (3), an inert gas is introduced as a protective gas, wherein the inert gas is argon and the introduction rate is 0.5-2 L / min.
[0016] Optionally, in step (4), the cooling temperature is 30-40℃, and the filter is a ceramic membrane filter with a pore size of 0.2-0.5μm.
[0017] Optionally, before step (1), the moisture content of the decolorized rice bran oil is tested and controlled to be ≤0.1%. If the moisture content exceeds the standard, vacuum dehydration is performed with a vacuum degree of 5-10 mmHg, a temperature of 80-100℃, and a dehydration time of 20-30 min.
[0018] Optionally, in step (2), the deodorization tower is made of 316L stainless steel and the inner wall of the deodorization tower is coated with a nano titanium dioxide coating with a thickness of 5-10μm.
[0019] This invention provides a deodorization process for rice bran oil that controls the formation of glycidyl esters. Compared with the prior art, this invention adopts a compound chelation pretreatment step. The citric acid, phytic acid and disodium EDTA in the compound chelating agent can work synergistically to more effectively chelate metal ions in rice bran oil and reduce the catalytic effect of metal ions on the formation of glycidyl esters. Compared with a single chelating agent, the amount of glycidyl esters formed can be reduced by 20-30%.
[0020] Gradient pressure swing deodorization differs from conventional constant vacuum deodorization. By rationally adjusting the gradient of vacuum and temperature changes, it significantly shortens the residence time of oils at high temperatures while ensuring deodorization effectiveness, thus reducing the formation of grease (GEs). Compared with conventional deodorization processes, the amount of GEs generated can be reduced by 40-50%.
[0021] The low-temperature plasma post-treatment step utilizes the high-energy active particles of low-temperature plasma to decompose some of the residual GEs in the deodorized rice bran oil, further reducing the GEs content and controlling the GEs content in the final product to below 0.5 mg / kg.
[0022] The process of this invention is simple to operate, highly controllable, suitable for industrial production applications, and will not significantly affect the flavor and nutritional components of rice bran oil, thus ensuring the quality of rice bran oil. Detailed Implementation
[0023] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.
[0024] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0025] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate orientation or positional relationships. These terms are primarily used to better describe this application and its embodiments and are not intended to limit the indicated devices, elements, or components to having a specific orientation or to be constructed and operated in a specific orientation.
[0026] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.
[0027] In addition, the term "multiple" should mean two or more.
[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.
[0029] Example 1
[0030] A process for deodorizing rice bran oil to control glycidyl ester formation includes the following steps:
[0031] (1) Compound chelation pretreatment: The decolorized rice bran oil was sent to a pretreatment tank, and a compound chelating agent was added. The compound chelating agent was composed of citric acid, phytic acid, and disodium ethylenediaminetetraacetate in a mass ratio of 2:1.5:0.8, and the amount added was 0.05% of the mass of the rice bran oil. The pretreatment was carried out at 60℃ and a stirring speed of 150 r / min for 20 min.
[0032] The following are instructions regarding the compound chelation pretreatment:
[0033] Citric acid is a small tricarboxylic acid molecule (molecular weight 210.14 g / mol) containing three carboxyl groups (-COOH) and one hydroxyl group (-OH). It can form stable six-membered ring chelates with metal ions through its carboxyl groups (coordination bond energy approximately 40-50 kJ / mol). Its advantages lie in its good water solubility and rapid diffusion rate, enabling it to quickly capture free metal ions in the early stages of pretreatment (within 1-5 min), thereby reducing the concentration of active sites catalyzing the formation of GEs in the system.
[0034] Phytic acid (inositol hexaphosphate) is a natural organophosphate ester containing 6 phosphate groups (-PO(OH)) in its molecule, providing 12 potential coordination sites (6 hydroxyl oxygens and 6 phosphate oxygens), which can form polycyclic chelates with metal ions (coordination bond energy reaches 60-70 kJ / mol).
[0035] EDTA-2Na is a synthetic aminocarboxylic acid chelating agent containing two amino nitrogen groups and four carboxyl oxygen groups in its molecule. It can form stable 1:1 chelates with almost all metal ions through "nitrogen-oxygen" coordinated coordination (coordination bond binding energy 50-60 kJ / mol). Moreover, the chelates are not easily dissociated in a wide pH range (2-12) and at high temperatures (≤250℃) (pK value ≥10.0).
[0036] When the three chelating agents are combined, they achieve synergy through a progressive mechanism of "rapid capture - deep chelation - stable solidification". Citric acid (small molecule) rapidly diffuses to all parts of the oil phase to capture free metal ions, phytic acid (large molecule) specifically binds high-valence metal ions and forms a precipitated complex, and EDTA-2Na removes bound metal ions through displacement. The three together cover metal ions in different forms. The citric acid chelate rapidly reduces the activity of metal ions in the pretreatment stage, while the highly stable chelate of phytic acid and EDTA-2Na continues to play a role in the subsequent high-temperature deodorization stage to prevent the re-release of metal ions. Some polar groups of citric acid and EDTA-2Na can enhance the dispersibility of phytic acid in the oil phase, while the hydrophobic framework of phytic acid can promote the migration of EDTA-2Na to the oil-water interface and improve the chelation efficiency of metal ions adsorbed at the interface.
[0037] (2) Gradient Pressure Swing Deodorization: The rice bran oil treated in step (1) was fed into a deodorization tower made of 316L stainless steel with an 8μm thick nano-titanium dioxide coating on the inner wall. First, the vacuum in the deodorization tower was controlled at 1.5 mmHg, and the temperature was raised to 210℃ and maintained for 12 min. Then, the vacuum was lowered to 0.8 mmHg, and the temperature was raised to 230℃ and maintained for 25 min. Finally, the vacuum was raised to 1.5 mmHg, and the temperature was lowered to 205℃ and maintained for 8 min. Purified nitrogen gas was introduced as stripping gas during the deodorization process. The purity of the nitrogen gas was 99.99%, and the amount introduced was 7% of the mass of the rice bran oil. The gas in the deodorization tower was sampled and analyzed every 8 min. When the volatile matter content was ≤0.01%, the deodorization process for that stage was terminated early.
[0038] (3) Low-temperature plasma post-treatment: The rice bran oil deodorized in step (2) is introduced into a low-temperature plasma treatment device and treated for 10 min under the conditions of 200W power and 20Pa vacuum. Argon gas is introduced as a protective gas during the treatment, and the introduction rate is 1L / min.
[0039] (4) Cooling and filtration: The rice bran oil processed in step (3) is cooled to 35°C and filtered through a ceramic membrane filter with a pore size of 0.3 μm to obtain the finished rice bran oil.
[0040] The rice bran oil obtained in this example was found to have a GE content of 0.42 mg / kg, an acid value of 0.3 mg KOH / g, a peroxide value of 3 meq / kg, and a good flavor.
[0041] Example 2
[0042] A process for deodorizing rice bran oil to control glycidyl ester formation includes the following steps:
[0043] (1) The moisture content of the decolorized rice bran oil was tested and found to be 0.15%, which exceeded the standard. Vacuum dehydration was then performed at a vacuum degree of 8 mmHg, a temperature of 90℃, and a dehydration time of 25 min. The moisture content after dehydration was 0.08%.
[0044] (2) Compound chelation pretreatment: The dehydrated rice bran oil was sent to a pretreatment tank and a compound chelating agent was added. The compound chelating agent was composed of citric acid, phytic acid and disodium ethylenediaminetetraacetate in a mass ratio of 1:1:0.5, and the amount added was 0.03% of the mass of the rice bran oil. The pretreatment was carried out at 50℃ and a stirring speed of 100r / min for 15min.
[0045] (3) Gradient Pressure Swing Deodorization: The rice bran oil treated in step (2) is fed into a deodorization tower made of 316L stainless steel with a 5μm thick nano-titanium dioxide coating on the inner wall. First, the vacuum level inside the deodorization tower is controlled at 1 mmHg, and the temperature is raised to 200℃ and maintained for 10 min. Then, the vacuum level is reduced to 0.5 mmHg, and the temperature is raised to 220℃ and maintained for 20 min. Finally, the vacuum level is raised to 1 mmHg, and the temperature is reduced to 200℃ and maintained for 5 min. Purified nitrogen gas is introduced as stripping gas during the deodorization process. The purity of the nitrogen gas is 99.99%, and the amount introduced is 6% of the mass of the rice bran oil. The gas inside the deodorization tower is sampled and analyzed every 5 min. When the volatile matter content is ≤0.01%, the deodorization process for that stage is terminated early.
[0046] (4) Low-temperature plasma post-treatment: The rice bran oil deodorized in step (3) is introduced into a low-temperature plasma treatment device and treated for 5 minutes under the conditions of 100W power and 10Pa vacuum. Argon gas is introduced as a protective gas during treatment at a rate of 0.5L / min.
[0047] (5) Cooling and filtration: The rice bran oil processed in step (4) is cooled to 30°C and filtered through a ceramic membrane filter with a pore size of 0.2 μm to obtain the finished rice bran oil.
[0048] The rice bran oil obtained in this example was found to have a GEs content of 0.48 mg / kg, an acid value of 0.4 mg KOH / g, a peroxide value of 4 meq / kg, and a good flavor.
[0049] Example 3
[0050] A process for deodorizing rice bran oil to control glycidyl ester formation includes the following steps:
[0051] (1) The moisture content of the decolorized rice bran oil was tested and found to be 0.08%, which meets the requirements.
[0052] (2) Compound chelation pretreatment: The decolorized rice bran oil was sent to a pretreatment tank and a compound chelating agent was added. The compound chelating agent was composed of citric acid, phytic acid and disodium ethylenediaminetetraacetate in a mass ratio of 3:2:1, and the amount added was 0.08% of the mass of the rice bran oil. The pretreatment was carried out at 70℃ and a stirring speed of 200r / min for 30min.
[0053] (3) Gradient Pressure Swing Deodorization: The rice bran oil treated in step (2) is fed into a deodorization tower made of 316L stainless steel with a 10μm thick nano-titanium dioxide coating on the inner wall. First, the vacuum level inside the deodorization tower is controlled at 2 mmHg, and the temperature is raised to 220℃ and maintained for 15 min. Then, the vacuum level is reduced to 1 mmHg, and the temperature is raised to 240℃ and maintained for 30 min. Finally, the vacuum level is raised to 2 mmHg, and the temperature is reduced to 210℃ and maintained for 10 min. Purified nitrogen gas with a purity of 99.99% is introduced as stripping gas during the deodorization process, and the amount introduced is 10% of the mass of the rice bran oil. The gas inside the deodorization tower is sampled and analyzed every 10 min. When the volatile matter content is ≤0.01%, the deodorization process for that stage is terminated early. (4) Low-temperature plasma post-treatment: The rice bran oil deodorized in step (3) is introduced into a low-temperature plasma treatment device and treated for 15 minutes under the conditions of 300W power and 30Pa vacuum. Argon gas is introduced as a protective gas during the treatment, and the introduction rate is 2L / min.
[0054] (5) Cooling and filtration: The rice bran oil processed in step (4) is cooled to 40°C and filtered through a ceramic membrane filter with a pore size of 0.5 μm to obtain the finished rice bran oil.
[0055] The rice bran oil obtained in this example was tested and found to contain GEs content of 0.45 mg / kg, acid value of 0.35 mg KOH / g, peroxide value of 3.5 meq / kg, and good flavor.
[0056] Comparative Example
[0057] The conventional rice bran oil deodorization process involves the following steps:
[0058] (1) The decolorized rice bran oil was directly fed into the deodorization tower and deodorized for 30 minutes under the conditions of vacuum degree of 5 mmHg and temperature of 250℃. Ordinary nitrogen was introduced during the deodorization process, and the amount introduced was 8% of the mass of the rice bran oil.
[0059] (2) Cool the deodorized rice bran oil to 35°C and filter it with ordinary filter cloth to obtain the finished rice bran oil.
[0060] Experimental data comparison: Relevant indicators of the rice bran oil obtained in Examples 1-3 and the comparative example were tested, and the results are shown in the table below:
[0061]
[0062] Note: Flavor scores were determined by 10 professional evaluators using a blind tasting method, and the average score was taken; the higher the score, the better the flavor.
[0063] The experimental data above show that the rice bran oil obtained by using the process of the present invention in Examples 1-3 has a much lower content of GEs than the comparative example, and its acid value and peroxide value are better than those of the comparative example. It also has a lower content of volatile substances and a higher flavor score, which fully demonstrates that the process of the present invention can effectively ensure the quality of rice bran oil while controlling the generation of GEs.
[0064] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A process for deodorizing rice bran oil to control glycidyl ester formation, characterized in that, Includes the following steps: (1) Compound chelation pretreatment: The decolorized rice bran oil is sent to a pretreatment tank, a compound chelating agent is added, and pretreatment is carried out at a certain temperature and stirring speed. The compound chelating agent is composed of citric acid, phytic acid and disodium ethylenediaminetetraacetate in a mass ratio of (1-3):(1-2):(0.5-1). The amount of compound chelating agent added is 0.03-0.08% of the mass of rice bran oil. (2) Gradient pressure swing deodorization: The rice bran oil treated in step (1) is sent to the deodorization tower for gradient pressure swing deodorization. The temperature, time and vacuum changes during the deodorization process are controlled. The gradient pressure swing deodorization is as follows: First, the vacuum in the deodorization tower is controlled at 1-2 mmHg, the temperature is raised to 200-220℃ and held for 10-15 min; then the vacuum is reduced to 0.5-0.8 mmHg, the temperature is raised to 220-240℃ and held for 20-30 min; finally, the vacuum is raised to 1-2 mmHg, the temperature is reduced to 200-210℃ and held for 5-10 min. (3) Low-temperature plasma post-treatment: The rice bran oil after deodorization in step (2) is introduced into a low-temperature plasma treatment device for low-temperature plasma treatment. The power of the low-temperature plasma treatment is 100-300W, the treatment time is 5-15min, the vacuum degree during treatment is 10-30Pa, and an inert gas is introduced as a protective gas during the low-temperature plasma treatment. The inert gas is argon, and the introduction rate is 0.5-2L / min. (4) Cooling and filtration: Cool the rice bran oil processed in step (3) to a certain temperature and filter it to obtain the finished rice bran oil.
2. The process according to claim 1, characterized in that, In step (1), the pretreatment temperature is 50-70℃, the stirring speed is 100-200r / min, and the pretreatment time is 15-30min.
3. The process according to claim 1, characterized in that, In step (2), purified nitrogen gas is introduced during the deodorization process. The purity of the nitrogen gas is ≥99.99%, and the amount introduced is 6-10% of the mass of the rice bran oil.
4. The process according to claim 1, characterized in that, In step (4), the cooling temperature is 30-40℃, and the filtration uses a ceramic membrane filter with a pore size of 0.2-0.5μm.
5. The process according to claim 1, characterized in that, Before step (1), the moisture content of the decolorized rice bran oil is tested and controlled to be ≤0.1%. If the moisture content exceeds the standard, vacuum dehydration is performed. The vacuum degree is 5-10 mmHg, the temperature is 80-100℃, and the dehydration time is 20-30 min.
6. The process according to claim 1, characterized in that, In step (2), the deodorization tower is made of 316L stainless steel and the inner wall of the deodorization tower is coated with a nano titanium dioxide coating with a thickness of 5-10μm.