A refining method for comprehensively controlling nutrients and harmful substances in rice bran oil

Abstract

This invention belongs to the field of oil processing technology, specifically relating to a comprehensive refining method for controlling nutrients and harmful substances in rice bran oil. The comprehensive refining method for controlling nutrients and harmful substances in rice bran oil provided by this invention, through the selection of refining raw materials and the integrated design of processes such as hydration degumming, alkali refining deacidification, primary decolorization, physical deacidification, secondary decolorization, and low-temperature deodorization, forms a complete refining process for rice bran oil. This process enables the loss rate of oryzanol in the finished rice bran oil to be <15%, and the content of trichloropropanol esters and glycidyl esters to be lower than the EU standards (trichloropropanol ester content ≤2500μg / kg, glycidyl ester content ≤1000μg / kg), greatly improving the nutritional value of rice bran oil and effectively ensuring its nutritional value and quality safety, thus possessing good industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of oil processing technology, specifically relating to a refining method for comprehensively controlling nutrients and harmful substances in rice bran oil. Background Technology

[0002] With my country's economic development, consumer demand has gradually shifted from simply "eating enough" to "eating well." Rice is the world's second largest food crop, and the yield of rice bran, a byproduct of rice processing, is also considerable. Rice bran contains 12% to 23% oil, and the natural plant oil extracted from it is called rice bran oil. Because rice bran oil has a balanced and reasonable fatty acid composition (the ratio of oleic acid to linoleic acid is close to 1:1, with both accounting for nearly 80%), and contains abundant nutritionally active ingredients (such as oryzanol, phytosterols, and squalene), it possesses biological functions such as preventing cardiovascular disease and alleviating memory decline. Furthermore, it exhibits unique frying stability, making it suitable as a high-quality frying oil. Therefore, in recent years, rice bran oil has become increasingly popular among consumers, and market demand has been rising year by year.

[0003] Among the nutrients in rice bran oil, oryzanol is the most abundant, reaching 1.5%-2.9% in crude rice bran oil. As the most representative byproduct of rice bran oil, oryzanol possesses various physiological benefits, including lowering blood lipids, anti-oxidation, and improving nervous system disorders. Therefore, proper processing techniques should minimize oryzanol loss. Currently, traditional rice bran oil processing methods result in significant oryzanol loss. Furthermore, due to the long processing route, the quality of each step directly impacts the final product's quality. Before processing, crude rice bran oil typically has a dark color and high acid value, presenting challenges for refining. Improper processing techniques can lead to the production of large amounts of harmful factors such as trichloropropanol esters and glycidyl esters during processing, severely affecting product quality and food safety. Therefore, the urgent industry problem to be solved at this stage is: how to conduct scientific and reasonable rice bran oil processing in order to effectively improve the nutritional quality of the oil and reduce the content of harmful factors while reducing energy consumption, so as to meet the consumer market's demand for higher quality rice bran oil.

[0004] In existing technologies, some researchers have reduced the loss of oryzanol by improving the alkali refining and deacidification process of rice bran oil. For example, Chen Yuanshun et al. (Chen Yuanshun, Liu Yulan, Dong Ting et al. Study on the effect of alkali refining and deacidification process of rice bran mixed oil [J]. China Oils and Fats, 2014, 39(01):6-9) believe that the optimal alkali refining conditions are: alkali refining temperature 55℃, alkali solution mass fraction 11.06%, and mixed oil concentration 40%. Under these conditions, the loss rate of oryzanol is 64.22%. Although this method can reduce the loss of oryzanol, the degree of loss is still very high. Qu Yanfeng et al. (Qu Yanfeng, Han Qianyu, Li Shuzhen. Optimization of secondary alkali refining deacidification process for high-oryzanol rice bran oil [J]. Food Industry, 2021, 42 (08): 130-134) used a secondary alkali refining deacidification process, which can increase the retention rate of oryzanol to 89.8%. However, when the secondary alkali refining is implemented in the factory, an additional deacidification equipment is required, which increases the operating cost of the factory. The invention patent application with publication number CN102399630A uses adsorption deacidification, and the oryzanol content in the refined oil can reach more than 1%. However, due to the limitations of adsorbent cost and solid waste treatment, this method still cannot be industrialized. In addition, there are also relevant studies in the prior art on reducing the content of hazardous factors by improving the deodorization process. However, the deodorization process used by conventional methods is often at high temperature and high energy consumption, and the reduction of trichloropropanol esters and glycidyl esters is limited.

[0005] The above studies indicate that current rice bran oil refining methods often improve nutrient retention or reduce harmful substances from a single perspective, failing to simultaneously address the retention requirements of the nutrient oryzanol and the control requirements of harmful factors such as 3-MCPD and glycidyl esters. Therefore, they still cannot meet the industrial market's demand for more nutritious and safer grain oils. Thus, developing a novel rice bran oil refining method that balances nutrient retention and harmful substance control is of great significance for alleviating the insufficient self-sufficiency rate of edible oils and improving the nutritional value of edible oils and the quality of life for consumers. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, the present invention aims to provide a refining method for comprehensively controlling the nutrients and harmful substances in rice bran oil. By coordinating and controlling the entire refining process of rice bran oil, it can effectively reduce the loss of nutrients and the generation of harmful substances, solving the problem of the difficulty in controlling the generation of trichloropropanol esters and glycidyl esters in rice bran oil in the prior art. At the same time, it can meet the industrial demand for the retention of oryzanol in rice bran oil to prepare more nutritious grain oil.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A refining method for comprehensively controlling nutrients and harmful substances in rice bran oil includes the following steps:

[0009] (1) The rice bran raw material is leached with a solvent to obtain an leached mixed oil; the mass concentration of the oil in the leached mixed oil is 30%~40%;

[0010] (2) The leached mixed oil obtained in step (1) is subjected to hydration degumming, alkali refining and deacidification treatment in sequence, then centrifuged to remove impurities, then subjected to desolventizing treatment, and then washed with water to obtain deacidified oil;

[0011] In the alkaline refining and deacidification process, the actual amount of alkali added is 60% to 80% of the theoretical amount of alkali added; the desolventizing process is a two-stage evaporation desolventizing process; the first evaporation temperature of the two-stage evaporation desolventizing process is 55 to 65°C, and the second evaporation temperature is 80 to 90°C.

[0012] (3) The deacidified oil obtained in step (2) is dewaxed, and then decolorized, physically deacidified, and decolorized in sequence. Finally, it is deodorized at low temperature to obtain the refined finished rice bran oil.

[0013] The primary decolorization process involves using a decolorizing agent at a temperature of 100-105°C; the physical deacidification process takes place at 190-210°C for 10-30 minutes; the secondary decolorization process also uses a decolorizing agent at a temperature of 110-115°C; and the low-temperature deodorization process takes place at 210-220°C for 30-45 minutes. The nutrient is oryzanol; and the hazardous substances are trichloropropanol ester and glycidyl ester.

[0014] Furthermore, in this invention, the theoretical alkali addition amount has a conventional meaning understood by those skilled in the art. That is, theoretical alkali addition amount = 7.13 × 10 -4 ×m×AV; where m is the weight of the oil in g; AV is the acid value in mg / g.

[0015] As a preferred embodiment of the present invention, in step (1), the acid value of the rice bran raw material is 10~40mg / g.

[0016] As a preferred embodiment of the present invention, in step (1), the solvent is n-hexane.

[0017] As a preferred embodiment of the present invention, in step (2), the hydration degumming specifically involves: first adding 0.05%-0.2% by weight of reverse osmosis soft water containing citric acid to the leached mixed oil, then adding 5%-6% by weight of hot water at 55-65°C, and mixing and stirring for 10-20 minutes; the citric acid content in the reverse osmosis soft water is 40%-50%. In the present invention, the use of reverse osmosis soft water containing citric acid to assist sedimentation degumming improves degumming efficiency compared to the hot water degumming process containing phosphoric acid, and is also beneficial for removing chloride ions accumulated in the mixed oil.

[0018] As a preferred embodiment of the present invention, in step (3), the dewaxing is carried out by cooling crystallization; the dewaxing temperature is 5~20℃ and the time is 0.5~4h.

[0019] In a preferred embodiment of the present invention, in step (3), the decolorizing agent is one or more of activated clay, attapulgite, and activated carbon. More preferably, the decolorizing agent is a mixture of activated clay and activated carbon; the mass percentage of activated carbon in the mixture is 0.1% to 0.5%.

[0020] As a preferred embodiment of the present invention, in step (3), the decolorization time is 15-25 minutes, and the amount of decolorizing agent added is 1%-3% of the oil weight. More preferably, the decolorization pressure is 1k-5kPa.

[0021] As a preferred embodiment of the present invention, in step (3), the acid value of the oil is controlled to be 0.1~3mg / g after physical deacidification.

[0022] As a preferred embodiment of the present invention, in step (3), the time for secondary decolorization is 15-25 minutes, and the amount of decolorizing agent added is 3%-5% of the oil weight. More preferably, the pressure for secondary decolorization is 1k-6kPa.

[0023] The technical features and beneficial effects of this invention are as follows:

[0024] I. This invention directly uses the extracted mixed oil for refining, eliminating the need for prior solvent removal and saving the time and effort of this pre-solvent removal process. Furthermore, compared to extracted mixed oil obtained through prior solvent removal, the oil obtained by directly refining the extracted mixed oil produced in this invention has a lighter color. Therefore, subsequent excessive heat decolorization is unnecessary, which helps reduce the loss of the nutrient oryzanol during excessive decolorization and also helps reduce the content of trichloropropanol esters and glycidyl esters produced during heat decolorization.

[0025] Second, this invention strictly controls the actual amount of alkali added during the alkali refining and deacidification process, ensuring that the actual amount of alkali added is 60% to 80% of the theoretical amount. This control over the degree of chemical alkali refining effectively preserves oryzanol, and it can be directly implemented on a mixed oil production line without the need for additional equipment. Furthermore, this invention effectively coordinates alkali refining and deacidification with subsequent physical deacidification, reducing the difficulty and time required for physical deacidification, thereby further preventing the formation of trichloropropanol esters and glycidyl esters.

[0026] Third, this invention sets physical deacidification between primary and secondary decolorization, and effectively controls the processes of primary and secondary decolorization. On the one hand, the deacidification process can effectively reduce the acid value of oils and fats. On the other hand, the secondary decolorization process can effectively remove the harmful substances such as trichloropropanol esters and glycidyl esters produced by physical deacidification, thereby further reducing the content of harmful substances such as trichloropropanol esters and glycidyl esters in oils and fats.

[0027] Fourth, the present invention employs a lower temperature deodorization process, which works closely with the aforementioned secondary decolorization and physical deacidification processes to effectively control the content of trichloropropanol esters and glycidyl esters in the final product.

[0028] In summary, the refining method for comprehensively controlling nutrients and harmful substances in rice bran oil provided by this invention, through the selection of refining raw materials and the integrated design of processes such as hydration degumming, alkali refining deacidification, primary decolorization, physical deacidification, secondary decolorization, and low-temperature deodorization, forms a complete refining process for rice bran oil. This process ensures that the loss rate of oryzanol in the finished rice bran oil is less than 15%, and the content of trichloropropanol esters is less than 1100 μg / kg and the content of glycidyl esters is less than 1000 μg / kg, which are lower than EU standards. Therefore, this invention not only greatly improves the nutritional value of rice bran oil but also produces rice bran oil products with trichloropropanol ester and glycidyl ester content within EU limits, effectively guaranteeing the nutritional value and quality safety of rice bran oil, and has good industrial application value. Attached Figure Description

[0029] Figure 1 These are color images of the deacidified oils obtained by the refining methods of Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, the raw materials and methods involved in the following embodiments are all commercially available materials and conventional processes in the art.

[0031] Example 1

[0032] A refining method for comprehensively controlling nutrients and harmful substances in rice bran oil includes the following steps:

[0033] (1) Rice bran raw material was leached with n-hexane without solvent removal to obtain leached mixed oil. The acid value of the rice bran raw material was 15.4 mg / g; the mass concentration of oil in the leached mixed oil was 40%.

[0034] (2) The leached mixed oil obtained in step (1) is hydrated and degummed in sequence. Then, without separation, it is directly added to alkaline solution (22°Bé) for alkaline refining and deacidification treatment. The actual amount of alkali added in the alkaline refining and deacidification treatment is 63% of the theoretical amount of alkali added. After alkaline refining, the acid value of the oil is controlled to be 5.0 mg / g. After alkaline refining, the soap and gum impurities are removed by centrifugation. The supernatant is subjected to two-stage evaporation and solvent removal treatment. The first evaporation temperature is 60°C and the second evaporation temperature is 85°C. After solvent removal, it is washed with water until neutral to obtain deacidified oil.

[0035] Specifically, the hydration degumming process involves adding 0.1% of citric acid-containing reverse osmosis soft water (45% by weight of citric acid) to the leached mixed oil, followed by adding 5.52% of 60°C hot water and mixing for 15 minutes.

[0036] (3) Cool the deacidified oil obtained in step (2) to 15°C and dewax it for 2 hours. Then, perform a first decolorization, physical deacidification, and second decolorization treatment in sequence. Finally, perform a low-temperature deodorization treatment to obtain the refined finished rice bran oil.

[0037] The decolorization process involved two steps: First, a decolorizing agent (a mixture of activated clay and activated carbon, with activated carbon comprising 0.2 wt% of the oil by weight) was used at 105°C for 20 minutes under a pressure of 3 kPa. Second, physical deacidification was performed at 200°C for 15 minutes, resulting in an acid value of 0.5 mg / g. Third, a second decolorization process was conducted at 115°C for 20 minutes, using a decolorizing agent comprising 4% of the oil by weight (also a mixture of activated clay and activated carbon, with activated carbon comprising 0.2 wt% of the oil by weight). Finally, a low-temperature deodorization treatment was performed at 220°C for 40 minutes.

[0038] Example 2

[0039] A refining method for comprehensively controlling nutrients and harmful substances in rice bran oil includes the following steps:

[0040] (1) Rice bran raw material was leached with n-hexane without solvent removal to obtain leached mixed oil. The acid value of the rice bran raw material was 31 mg / g; the mass concentration of oil in the leached mixed oil was 30%.

[0041] (2) The leached mixed oil obtained in step (1) is sequentially hydrated and degummed. Then, without separation, it is directly added to alkaline solution (22°Bé) for alkaline refining and deacidification treatment. The actual amount of alkali added in the alkaline refining and deacidification treatment is 79.3% of the theoretical amount of alkali added. After alkaline refining, the acid value of the oil is controlled to be 6.0 mg / g. After alkaline refining, the soap and gum impurities are removed by centrifugation. The supernatant is subjected to two-stage evaporation and solvent removal treatment. The first evaporation temperature is 60°C and the second evaporation temperature is 85°C. After solvent removal, it is washed with water until neutral to obtain deacidified oil.

[0042] Specifically, the hydration degumming process involves adding 0.1% of citric acid-containing reverse osmosis soft water (45% by weight of citric acid) to the leached mixed oil, followed by adding 5.52% of 60°C hot water and mixing for 15 minutes.

[0043] (3) Cool the deacidified oil obtained in step (2) to 15°C and dewax it for 2 hours. Then, perform a first decolorization, physical deacidification, and second decolorization treatment in sequence. Finally, perform a low-temperature deodorization treatment to obtain the refined finished rice bran oil.

[0044] The decolorization process involved two steps: First, a decolorizing agent (a mixture of activated clay and activated carbon, with activated carbon comprising 0.2 wt% of the oil by weight) was used at 105°C for 20 minutes under a pressure of 3 kPa. Second, physical deacidification was performed at 200°C for 20 minutes, resulting in an acid value of 0.8 mg / g. Third, a second decolorization process was conducted at 115°C for 20 minutes, using a decolorizing agent comprising 4% of the oil by weight (again, a mixture of activated clay and activated carbon, with activated carbon comprising 0.2 wt% of the oil by weight). Finally, a low-temperature deodorization treatment was performed at 220°C for 40 minutes.

[0045] Comparative Example 1

[0046] A refining method for rice bran oil is provided, the refining process of which is basically similar to that of Example 1. The difference between the two is that in step (1): hexane is used to leach the rice bran raw material to remove part of the solvent and obtain the leachate mixed oil; the mass concentration of oil in the leachate mixed oil is 60%. In step (3): the secondary decolorization time is 40 min. The remaining steps and parameters are the same as in Example 1.

[0047] Comparative Example 2

[0048] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that: step (2) is: the actual amount of alkali added in the alkali refining and deacidification treatment is 100% of the theoretical amount of alkali added, and the acid value of the oil after alkali refining is 0.1 mg / g. The remaining steps and parameters are the same as in Example 1.

[0049] Comparative Example 3

[0050] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that: step (2) is: the actual amount of alkali added in the alkali refining and deacidification treatment is 93.6% of the theoretical amount of alkali added, and the acid value of the oil after alkali refining is 1 mg / g. The remaining steps and parameters are the same as in Example 1.

[0051] Comparative Example 4

[0052] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that: step (2) is: the actual amount of alkali added in the alkali refining and deacidification treatment is 102.3% of the theoretical amount of alkali added, and the acid value of the oil is controlled to be 0.3 mg / g after alkali refining. The remaining steps and parameters are the same as in Example 1.

[0053] Comparative Example 5

[0054] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that: step (3) is as follows: the deacidified oil obtained in step (2) is cooled to 15°C and dewaxed for 2 hours, then subjected to physical deacidification, primary decolorization, secondary decolorization, and finally low-temperature deodorization to obtain the refined finished rice bran oil. The physical deacidification, primary decolorization, secondary decolorization and other process steps and specific parameters are the same as in Example 1.

[0055] Comparative Example 6

[0056] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that: step (3) is: the deacidified oil obtained in step (2) is cooled to 15°C and dewaxed for 2 hours, and then subjected to physical deacidification and decolorization treatment in sequence. Decolorization is performed using a decolorizing agent (a mixture of activated clay and activated carbon, with activated carbon content of 0.2 wt%) accounting for 6% of the oil weight, the temperature of the second decolorization is 115°C and the time is 40 minutes, and finally a low-temperature deodorization treatment is performed to obtain the refined finished rice bran oil; the remaining steps and specific parameters are the same as in Example 1.

[0057] Comparative Example 7

[0058] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that in step (3): the temperature of the low-temperature deodorization treatment is 230°C and the time is 60 min; the remaining steps and specific parameters are the same as those in Example 1.

[0059] Comparative Example 8

[0060] A refining method for rice bran oil, the refining process of which is basically similar to that of Example 1, the difference being that in step (3): the temperature of the low-temperature deodorization treatment is 260°C and the time is 90 min; the remaining steps and specific parameters are the same as those in Example 1.

[0061] Test case

[0062] In this experiment, the deacidified oils obtained in step (2) of Example 1 and Comparative Example 1 were first tested for color. The appearance pictures of the colors of the two are as follows. Figure 1 As shown in Table 1, the color test was conducted using the Lovibond colorimetric method.

[0063]

[0064] Depend on Figure 1 As can be seen from Example 1 and Comparative Example 1 in Table 1, the oil obtained by directly refining the leached mixed oil has a lighter color, while the mixed oil obtained after removing some of the solvent has a darker color. Therefore, the present invention directly uses the leached mixed oil for refining, and there is no need for excessive thermal decolorization treatment afterward. However, if Comparative Example 1 wants to obtain oil that meets the color requirements, it still needs to undergo long-term thermal decolorization.

[0065] This experiment further tested the indicators of the refined rice bran oil obtained in Examples 1-2 and Comparative Examples 1-8 of the present invention. Color was tested using the Lovibond colorimetric method, and the integrated area was measured using a spectrophotometer to determine the absorption peak area of ​​the oil between 400-800 nm. The method for determining oryzanol content is as described in LS / T 6121.1-2017 "Determination of Oryzanol Content in Vegetable Oils by Spectrophotometry" (Grain and Oil Inspection). The content of 3-chloropropanol esters and glycidyl esters was tested using SN / T 5220-2019 "Determination of 3-Chloropropanol Ester and Glycidyl Ester in Exported Foods by Gas Chromatography-Mass Spectrometry". The results are shown in Table 2. "-" indicates that this test was not performed.

[0066]

[0067] As shown in Table 2, compared with Comparative Example 1, Examples 1 and 2 of the present invention exhibit a slightly darker color, a higher yellow value, a larger integrated area, and a lower content of oryzanol and a higher content of trichloropropanol ester. Furthermore, compared with Comparative Examples 2, 3, and 4, Examples 1 and 2 of the present invention show a significantly higher oryzanol retention rate. Moreover, compared with Comparative Examples 5 and 6, Examples 1 and 2 of the present invention have a lighter color, and the contents of trichloropropanol and glycidyl ester are significantly lower. Compared with Comparative Examples 7 and 8, Examples 1 and 2 of the present invention have a lighter color, and the contents of trichloropropanol and glycidyl ester are also significantly lower.

[0068] As can be seen from the above, the comprehensive refining method for controlling nutrients and harmful substances in rice bran oil provided by this invention, through the selection of refining raw materials and the comprehensive design of processes such as hydration degumming, alkali refining deacidification, primary decolorization, physical deacidification, secondary decolorization, and low-temperature deodorization, forms a complete refining process for rice bran oil. This process can reduce the loss rate of oryzanol in the finished rice bran oil to <15%, and reduce the content of trichloropropanol esters to less than 1100 μg / kg and glycidyl esters to less than 1000 μg / kg. This not only greatly improves the nutritional value of rice bran oil, but also produces rice bran oil products with trichloropropanol ester and glycidyl ester contents within the EU limits, effectively ensuring the nutritional value and quality safety of rice bran oil, and has good industrial application value.

[0069] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A refining method for comprehensively controlling nutrients and harmful substances in rice bran oil, characterized in that, Includes the following steps: (1) The rice bran raw material is leached with a solvent to obtain an leached mixed oil; the mass concentration of the oil in the leached mixed oil is 30%~40%; (2) The leached mixed oil obtained in step (1) is subjected to hydration degumming, alkali refining and deacidification treatment in sequence, then centrifuged to remove impurities, then subjected to desolventizing treatment, and then washed with water to obtain deacidified oil; In the alkaline refining and deacidification process, the actual amount of alkali added is 60% to 80% of the theoretical amount of alkali added; the desolventizing process is a two-stage evaporation desolventizing process; the first evaporation temperature of the two-stage evaporation desolventizing process is 55 to 65°C, and the second evaporation temperature is 80 to 90°C. (3) The deacidified oil obtained in step (2) is dewaxed, and then decolorized, physically deacidified, and decolorized in sequence. Finally, it is deodorized at low temperature to obtain the refined finished rice bran oil. The primary decolorization process involves using a decolorizing agent at a temperature of 100-105°C; the physical deacidification process takes place at 190-210°C for 10-30 minutes; the secondary decolorization process also uses a decolorizing agent at a temperature of 110-115°C; and the low-temperature deodorization process takes place at 210-220°C for 30-45 minutes. The nutrient is oryzanol; and the hazardous substances are trichloropropanol ester and glycidyl ester.

2. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to claim 1, characterized in that, In step (1), the acid value of the rice bran raw material is 10~40mg / g.

3. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to claim 1, characterized in that, In step (1), the solvent is n-hexane.

4. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to claim 1, characterized in that, In step (2), the hydration degumming specifically involves: first adding 0.05%-0.2% of reverse osmosis soft water containing citric acid to the leached mixed oil, then adding 5%-6% of hot water at 55-65°C, and mixing and stirring for 10-20 minutes; the citric acid content in the reverse osmosis soft water is 40%-50%.

5. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to any one of claims 1 to 4, characterized in that, In step (3), the dewaxing is performed using a cooling crystallization method; the dewaxing temperature is 5~20℃ and the time is 0.5~4h.

6. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to any one of claims 1 to 4, characterized in that, In step (3), the decolorizing agent is one or more of activated clay, attapulgite, and activated carbon.

7. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to any one of claims 1 to 4, characterized in that, In step (3), the decolorization time is 15-25 minutes, and the amount of decolorizing agent added is 1%-3% of the oil weight.

8. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to any one of claims 1 to 4, characterized in that, In step (3), the acid value of the oil is controlled to be 0.1~3mg / g after physical deacidification.

9. The refining method for comprehensively controlling nutrients and harmful substances in rice bran oil according to any one of claims 1 to 4, characterized in that, In step (3), the second decolorization time is 15~25 min, and the amount of decolorizing agent added is 3%~5% of the oil weight.

Images