Vegetable oil and refining method thereof

Abstract

The invention relates to vegetable oil and a refining method thereof. The refining method of the vegetable oil comprises the following steps: adding alkali liquor into a vegetable oil crude product for neutralization treatment and soap removal treatment to prepare soap-removed oil; the dosage of the alkali liquor is that the acid value of the soap-removed oil is 0.1 mg / g-0. 2mg / g; carrying out water washing and vacuum drying treatment on the soap-removed oil to prepare a first intermediate; adding a decolorizing agent and a silica-gel desiccant into the first intermediate for decolorizing treatment to prepare a second intermediate; carrying out deodorization treatment on the second intermediate, wherein the conditions are as follows: an adopted deodorization device comprises a plate tower and a packed tower; the second intermediate is firstly treated in the plate tower at the temperature of 220 DEG C to 230 DEG C for 35 minutes to 45 minutes, and then is treated in the packed tower at the temperature of 240 DEG C to 250 DEG C for 3 minutes to 7 minutes. The refining method of the vegetable oil can effectively reduce risk indexes such as trans-fatty acid, glycidyl ester and 3-chloropropanol ester in the vegetable oil so as to achieve the purposes of healthy oil use and safe oil use.

Description

Technical Field

[0001] This application relates to the technical field of edible oils, and particularly to a vegetable oil and a refining method thereof. Background Art

[0002] Currently, the refining process of edible vegetable oils generally requires vacuum deodorization under the conditions of relatively high temperature (245°C) and long deodorization time (90 minutes). This process can better ensure the refining quality indicators of edible vegetable oils (such as acid value, color, peroxide value, odor, etc.), but its safety risk indicators (such as trans fatty acids, glycidyl esters, 3-monochloropropane-1,2-diol esters) will be relatively high. However, in recent years, the industry has proposed more stringent limit standards for the safety risk indicator limits of edible vegetable oils, requiring that the trans fatty acid content ≤ 2% (zero trans fatty acids < 0.3%), the glycidyl ester content ≤ 1000 μg / kg, and the 3-monochloropropane-1,2-diol ester content ≤ 1250 μg / kg. Moreover, this limit standard only plays a guiding role in food safety and does not provide absolute guarantee. The traditional processing technology of edible vegetable oils often has the risk of exceeding the standard. Therefore, how to control the refining method of vegetable oils to achieve zero trans fatty acids and reduce the contents of glycidyl esters and 3-monochloropropane-1,2-diol esters is particularly important. Summary of the Invention

[0003] Based on this, this application provides a refining method of vegetable oil, which can effectively reduce the risk indicators such as trans fatty acids, glycidyl esters, and 3-monochloropropane-1,2-diol esters in vegetable oil, so as to achieve the purpose of healthy and safe use of oil.

[0004] In the first aspect of this application, a refining method of vegetable oil is provided, including the following steps:

[0005] Adding an alkali solution to the crude vegetable oil for neutralization treatment and de-saponification treatment to prepare de-saponified oil; the dosage of the alkali solution is such that the acid value of the de-saponified oil is 0.1 mg / g - 0.2 mg / g;

[0006] Performing water washing and vacuum drying treatment on the de-saponified oil to prepare a first intermediate;

[0007] Adding a decolorizing agent and a silica gel desiccant to the first intermediate for decolorization treatment to prepare a second intermediate; the decolorizing agent includes attapulgite clay;

[0008] Performing deodorization treatment on the second intermediate, and the conditions include: the deodorization device used includes a plate column and a packed column; the second intermediate is first in the plate column and treated with steam at 220°C - 230°C for 35 min - 45 min, and then in the packed column and treated with steam at 240°C - 250°C for 3 min - 7 min.

[0009] In one embodiment, in the neutralization treatment, an alkali solution is added to the crude vegetable oil and then stirred. The stirring rate is 60 rpm to 70 rpm, and the stirring time is 10 min to 30 min.

[0010] In one embodiment, the mass percentage of the decolorizing agent in the first intermediate is 0.5% to 1%.

[0011] In one embodiment, the mass percentage of the silica gel desiccant in the decolorizing agent is 10% to 30%.

[0012] In one embodiment, the packed column has at least one of the following characteristics:

[0013] (1) The height h of the structured packing layer satisfies: 4 m ≤ h < 5 m;

[0014] (2) The direct steam pipes at the bottom of the tower are arranged in a grid pattern, and the pipe spacing L is 20 cm to 60 cm;

[0015] (3) A flow-limiting orifice plate is provided at the direct steam inlet at the bottom of the tower, and the aperture R of the flow-limiting orifice plate is 7 mm to 10 mm.

[0016] In one embodiment, in the plate column, the length of the sealed barrier pipe between the tower layers is inserted from the upper layer into the vegetable oil liquid surface of the lower layer at 20 cm to 50 cm below.

[0017] In one embodiment, in the deodorization device, the plate column and the packed column adopt independent vacuum systems.

[0018] In one embodiment, the water or steam used in each step does not contain chloride ions.

[0019] In the second aspect of the present application, there is provided a vegetable oil prepared by the refining method described in the first aspect.

[0020] In one embodiment, the vegetable oil has at least one of the following characteristics:

[0021] (1) The trans fatty acid content < 0.3%;

[0022] (2) The glycidyl ester content < 300 μg / kg;

[0023] (3) The 3-monochloropropanediol ester content < 400 μg / kg.

[0024] The above-mentioned method for refining vegetable oil can effectively reduce risk indicators such as trans fatty acids, glycidol esters, and 3-monochloropropane-1,2-diol esters in vegetable oil by controlling the soapstock acid value in the neutralization treatment, using a decolorizing agent and silica gel desiccant in the decolorization treatment, and adopting a two-temperature deodorization process in the deodorization treatment, so as to achieve the purpose of healthy and safe use of oil. Brief Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of a deodorization device adopted in an example of this application. Detailed Description of the Embodiments

[0026] The following further details the vegetable oil and its refining method of this application in combination with specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of this application more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0028] As used herein, "one or more" and "at least one" refer to any one, any two, or any two or more of the listed items.

[0029] In this application, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumerative description and should be understood not to constitute a closed limitation on quantity.

[0030] In this application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open-ended technical solutions containing the listed features.

[0031] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0032] In this application, unless otherwise specified, the percentage content for solid-liquid mixing and solid-solid mixing refers to the mass percentage, and for liquid-liquid mixing, it refers to the volume percentage.

[0033] In this application, unless otherwise specified, the percentage concentration refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding the component.

[0034] In this application, unless otherwise specified, the temperature parameter allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0035] Room temperature in this application generally refers to 4°C to 30°C, preferably 20±5°C.

[0036] The annotations of "trans fatty acids", "glycidyl fatty acid esters (abbreviation, glycidyl esters)" and "chloropropanol esters" in this application are as follows:

[0037] (1) Trans fatty acids: The formation of trans fatty acids in edible oils mainly occurs during the deodorization process. High temperature and long-term heating of the active substances in vegetable oils are the main factors leading to the formation of trans fatty acids. Trans fatty acids can increase blood cholesterol levels and cause various harms. For example: 1) Reducing memory: Trans fatty acids have an inhibitory effect on a kind of cholesterol that can promote human memory; 2) Causing arteriosclerosis: Oils rich in trans fatty acids show the effect of promoting arteriosclerosis; 3) Causing thrombosis: Trans fatty acids have the effect of increasing blood viscosity and cohesion; 4) Affecting growth and development: Trans fatty acids can also be transported to the fetus through the placenta, and breastfed infants will passively ingest trans fatty acids due to their mothers' intake of margarine. Therefore, it is particularly important to reduce the content of trans fatty acids in vegetable oils. For high-quality infant formula foods, a higher "zero trans" requirement is put forward.

[0038] (2) Glycidyl fatty acid esters (GEs) are an esterification product of glycidol and fatty acids, mainly produced in the deodorization link of the oil refining process, and widely exist in refined vegetable oils and oil-based foods. Glycidyl esters mostly exist in edible oils in the form of esters. The glycidol produced during their lipid metabolism in the body is a genotoxic carcinogen, and glycidyl esters are also carcinogenic substances. Study the influencing factors for the formation of glycidyl esters in edible oils: including oil types, diglyceride content, refining process, heating temperature and time, and storage conditions.

[0039] (3) Chloropropanol esters are the esterification products of chloropropanol compounds and fatty acids. They are classified into 3-chloropropanol esters (3-MCPD esters), 2-chloro-1,3-propanediol esters (2-MCPD esters), 1,3-dichloro-2-propanol esters (1,3-DCP esters), and 2,3-dichloro-2-propanol esters (2,3-DCP esters) according to the types of chloropropanols. The 3-chloropropanol esters are detected in relatively high amounts in foods. Toxicological studies have shown that 3-chloropropanol esters and 3-chloropropanol have kidney, reproductive, and non-genotoxic effects, while glycidyl esters and glycidol are genotoxic carcinogens. Certain chlorine-containing compounds are the precursor substances for the formation of 3-chloropropanol esters. Oil crops will absorb chloride ions from chlorine-containing pesticide residues, organic fertilizer soil, and water during the growth process, and then convert them into reactive chlorine-containing compounds. These chlorine-containing compounds will react with glycerides during the oil refining process to form 3-chloropropanol esters.

[0040] Studies have found that glycidyl esters start to form at 200 °C and increase exponentially with the increase in temperature; when the content of diglycerides in vegetable oils reaches 3% - 4%, the correlation between the content of diglycerides and the formation amount of glycidyl esters is relatively significant. 3-Chloropropanol esters are formed in the temperature range of 160 °C - 200 °C, and higher temperatures have no effect on the formation amount. It is mainly necessary to limit the content of chloride ions in the oil. The formation mechanisms of 3-chloropropanol esters and glycidyl esters are different, and different measures need to be taken to inhibit their formation. And because of the different formation mechanisms, there is no significant correlation between the contents of 3-chloropropanol esters and glycidyl esters in the oil. The formation of trans fatty acids and glycidyl esters is easier than that of 3-chloropropanol esters. Because the formation of trans fatty acids and glycidyl esters is directly related to temperature and time (starting to form at 200 °C, and when the temperature reaches 230 °C, the formation rate increases significantly), and there is no significant correlation with the chlorine-containing compounds in the oil. The deodorization temperature in the oil refining process can be reduced to below 230 °C to inhibit the formation of trans fatty acids and glycidyl esters.

[0041] Based on this, optimizing the refining method of vegetable oils can reduce and control the generation of trans fatty acids, glycidyl esters, and 3-chloropropanol esters during the refining process of vegetable oils, thereby effectively controlling the safety risks of edible vegetable oils.

[0042] Some examples of this application provide a refining method for vegetable oils, including the following steps:

[0043] (1) Adding an alkali solution to the crude vegetable oil for neutralization treatment and de-saponification treatment to prepare de-saponified oil; the dosage of the alkali solution is such that the acid value of the de-saponified oil is 0.1 mg / g - 0.2 mg / g;

[0044] (2) Washing and vacuum drying the de-saponified oil to prepare a first intermediate;

[0045] (3) Add a decolorizing agent and silica gel desiccant to the first intermediate for decolorization treatment to prepare a second intermediate; the decolorizing agent includes attapulgite clay;

[0046] (4) Deodorize the second intermediate, and the conditions include: the deodorization device used includes a plate column and a packed column; the second intermediate is first treated in the plate column at 220°C to 230°C for 35 min to 45 min, and then in the packed column at 240°C to 250°C for 3 min to 7 min.

[0047] Without limitation, the vegetable oil includes soybean oil, sunflower oil or corn oil.

[0048] The crude vegetable oil is obtained by treating crude oil with phosphoric acid.

[0049] Further, in the neutralization treatment section of step (1):

[0050] One of the key control points in this section is: the addition amount of excess alkali. During the neutralization treatment, the addition of alkali solution has two main functions: one is to neutralize the phosphoric acid added in the previous process and the free fatty acids in the oil; another key function is to remove impurities such as phospholipids, metal ions, and pigments, that is, alkali refining and decolorization. Generally speaking, the color of the alkali-refined oil is about 30% lower than that before alkali refining. The principle mechanism is as follows: after adding alkali solution to the crude vegetable oil, the alkali reacts with phospholipids and oil to produce soapstock, and soapstock has an adsorption effect and can adsorb some solid pigments; another reason is the destruction of phenolic chromophore groups by alkali solution. Therefore, after adding a certain amount of alkali solution and thorough mixing and stirring, full mixing and adsorption decolorization can be achieved. The following Table 1 shows the dosage of the decolorizing agent (taking activated clay as an example) during subsequent decolorization treatment after traditional phosphoric acid degumming treatment (corresponding to the traditional phosphoric acid degummed oil in Table 1, that is, crude oil treated with phosphoric acid and hydrated degumming treatment) and alkali refining and decolorization (corresponding to the alkali-refined oil in Table 1, that is, crude oil treated with phosphoric acid and alkali neutralization treatment). It can be seen that the amount of clay required for alkali refining and decolorization is less than that for phosphoric acid degumming.

[0051] Table 1

[0052]

[0053] Calculation formula for the amount of lye added: The theoretical amount of lye to be added (g) = the weight of crude vegetable oil (kg) * acid value * 0.713. Generally, the over-alkali addition amount is 10% - 20% of the theoretical lye addition amount, and it is finally determined by the acid value of the deodorized oil separated by the deodorizing centrifuge on the production line. In some examples, the amount of the lye is such that the acid value (KOH) of the deodorized oil is 0.1 mg / g - 0.2 mg / g. Specifically, the acid value of the deodorized oil includes, but is not limited to: 0.1 mg / g, 0.11 mg / g, 0.12 mg / g, 0.13 mg / g, 0.14 mg / g, 0.15 mg / g, 0.16 mg / g, 0.17 mg / g, 0.18 mg / g, 0.19 mg / g, 0.2 mg / g, or the range between any two of the foregoing.

[0054] Industrial production operations have proven that when the acid value of the deodorized oil is lower than 0.1 mg / g, the refining yield of edible oil will be significantly reduced, which is not conducive to the operation of the enterprise. When the acid value of the deodorized oil is higher than 0.2 mg / g, it is not conducive to the alkali refining and decolorization in the neutralization treatment section, increases the addition amount of clay in the subsequent decolorization treatment section. More importantly, it increases the deodorization load in the deodorization treatment section, and higher deodorization temperature and deodorization time are required to meet the quality of other indicators of the refined finished oil, which is not conducive to reducing the content of trans fatty acids, glycidyl esters, and 3-chloropropanol esters. The amount of the lye is such that the acid value (KOH) of the deodorized oil is 0.1 mg / g - 0.2 mg / g, which can not only ensure the neutralization effect, but also ensure a high yield of the production line, and can also reduce the operation load of the deodorization system, meeting the industry demand for moderate processing.

[0055] Without limitation, the alkali in the lye can be NaOH and / or KOH, and it is generally used as a liquid lye with a mass concentration of 8% - 15% by adding water.

[0056] The second key control point in this section is: stirring time. After mixing the crude vegetable oil and the lye, high-intensity mixing and stirring for a certain time can make the materials fully mixed and better adsorbed and decolorized. In some examples, after adding the lye to the crude vegetable oil, stirring is carried out, the stirring rate is 60 rpm - 70 rpm, and the stirring time is 10 min - 30 min.

[0057] Further, in the deodorization treatment section of step (1): The neutralized crude vegetable oil is transported to a deodorizing centrifuge for oil-soap separation to obtain deodorized oil.

[0058] Further, in the water washing and vacuum drying process section of step (2), it can be operated according to traditional methods. Without limitation, it can include the following steps: adding hot water at 80°C to 100°C accounting for 4% to 7% of the weight of the de-saponified oil for water washing treatment, then heating up to 100°C to 120°C by steam heating, and carrying out vacuum dehydration drying under the condition of an absolute pressure vacuum of 80 mbar to 100 mbar.

[0059] Further, step (3) is the decolorization treatment section:

[0060] Activated clay is an adsorbent made from clay (mainly bentonite) as the raw material, treated by inorganic acidification or salts or other methods, and then rinsed with water and dried. It appears as a milky white powder, odorless, tasteless, non-toxic, and has a very strong adsorption property, capable of adsorbing colored substances and organic substances. Attapulgite clay is a food additive produced by a roasting process with attapulgite clay as the main raw material. It appears as an off-white powder, insoluble in water, oil, and organic solvents. Compared with similar products, it has the characteristics of good decolorization effect, fast filtration speed, and low residual oil rate. It is a new type of decolorization product with good performance and low price. Among them, activated clay has a high decolorization rate, but is relatively viscous, difficult to filter, and has a high residual oil; while attapulgite clay has a relatively lower decolorization rate, but has large particles, is easy to filter, and has a low residual oil.

[0061] It has been found through research that when activated clay is treated by methods such as acidification or salts, there will be chloride ions. In order to inhibit chloride ions, less or no activated clay can be added during the refining of vegetable oil, and the method of adding more attapulgite clay or using attapulgite clay alone is adopted to achieve a balance between production quality indicators and risk indicators. Preferably, the decolorizing agent includes attapulgite clay, and may also include activated clay; more preferably, the decolorizing agent is attapulgite clay.

[0062] After vacuum drying, the moisture content of the first intermediate is usually also in the range of 0.03% to 0.1%, that is to say, it still contains a certain amount of moisture. This small amount of moisture affects the decolorization efficiency of the decolorizing agent and also affects the vacuum load in the subsequent deodorization treatment section. When a small amount of moisture enters the deodorization device, under high-temperature conditions, water reacts with vegetable oil to generate hydrolysis reactions, more easily generating harmful substances such as fatty acids, trans-fatty acids, and glycidyl esters. Therefore, during the decolorization process, a silica gel desiccant needs to be incorporated into the decolorizing agent to fully dry and remove water from the oil to be decolorized (the first intermediate). In some examples, the mass percentage of the silica gel desiccant in the decolorizing agent is 10% to 30%. Specifically, the mass percentage of the silica gel desiccant in the decolorizing agent includes but is not limited to: 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30% or the range between any two of the foregoing.

[0063] In addition, in some of these examples, the mass percentage of the decolorizing agent in the first intermediate is 0.5% - 1%. Specifically, the mass percentage of the decolorizing agent in the first intermediate includes, but is not limited to: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or the range between any two of the foregoing.

[0064] Further, step (4) is a deodorization treatment section:

[0065] The deodorization treatment section is an important section that affects the content of trans fatty acids, glycidyl esters, and 3-chloropropanol esters, which are risk indicators of vegetable oil. On the one hand, this application improves the deodorization process, and on the other hand, it reforms the structure of the deodorization device.

[0066] 4.1 Improvement of the deodorization process:

[0067] The formation of trans fatty acids, glycidyl esters, and 3-chloropropanol esters is directly related to temperature. 3-chloropropanol esters are generally formed in the temperature range of 160°C - 200°C, while trans fatty acids and glycidyl esters start to be produced at 200°C, and when the temperature reaches 230°C, the production rate increases significantly. When steam distillation uses dechlorinated water vapor, the formation of 3-chloropropanol esters can be effectively inhibited.

[0068] While taking measures to reduce the content of trans fatty acids, glycidyl esters, and 3-chloropropanol esters, it is necessary to focus on the impact of these measures on the gas flavor, free fatty acid content, oxidative stability, nutrient content, and the removal of pollutants such as pesticides and mycotoxins in refined vegetable oil and its products. In addition, the problem of environmental pollution caused by taking these measures should also be comprehensively considered.

[0069] For the vegetable oil deodorization treatment section, it is necessary to ensure both the control of high-temperature deodorization on quality indicators (acid value, color, peroxide value, etc.) and the inhibition of high-temperature deodorization on risk indicators (trans fatty acids, glycidyl esters, and 3-chloropropanol esters). This is a relatively contradictory control point, so it is necessary to find an optimal balance control. Based on multiple industrial production tests and demonstrations, double-temperature deodorization in the refined deodorization treatment section can effectively and flexibly control the indicators of each parameter. The specific operating parameters are shown in Table 2 below:

[0070] Table 2

[0071]

[0072] In addition, the direct stripping steam required for this deodorization treatment is produced by evaporating dechlorinated water to ensure the stripping volume of the entire deodorization process. Since the plate column has a shorter residence time than the original process and several liquid levels are emptied, the direct stripping is also shut down accordingly. The overall consumption of stripping steam will be reduced compared to before, and the addition amount can be reduced from the original 0.8% to 0.5% (the ratio of steam volume to oil weight), achieving an energy-saving effect (the vacuum degree at the top of the deodorization tower is required to be no higher than 3 mbar). Moreover, the heat exchange efficiency of the workshop is greatly enhanced, and the natural consumption can be reduced by 0.4 m³ / ton of crude oil (i.e., reduced from the original 2.4 m³ / ton of crude oil to the current 2.0 m³ / ton of crude oil). More importantly, through this process method, zero trans fatty acids (trans fatty acid content < 0.3%) and lower contents of glycidol esters and 3-chloropropanol esters can be achieved. At the same time, by flexibly regulating the deodorization temperature and time, the refining yield can be increased by 0.2%, and most of the nutrients such as vitamin E and sterols can be retained in the refined vegetable oil, increasing the nutritional value of vegetable oil.

[0073] 4.2 Structural transformation of the deodorization device

[0074] The deodorization process operation is mainly reflected in three aspects: temperature, distillation time, and dechlorinated water steam distillation. Based on this, the structure of the deodorization device is transformed, and the transformation situation is shown in Table 3 below.

[0075] Table 3

[0076]

[0077] Without limitation, the structure of the deodorization device is as Figure 1 shown, including a plate column and a packed column. The crude vegetable oil (cold oil) is transported to the plate column through a pipeline and treated with water vapor at 225°C for 40 min, and the sealed barrier tube in the plate column is controlled to be inserted 30 cm below the liquid level of the next layer; then it is transported to the packed column and treated with water vapor at 245°C for 5 min. The height (h) of the structured packing layer in the packed column is controlled to be 4.5 m, the stripping steam at the bottom of the column is distributed in a grid pattern, the hole spacing L is 40 cm, and the aperture R of the orifice plate at the steam inlet is 8 mm; after the treatment in the packed column, the output is refined vegetable oil (hot oil). Among them, the plate column and the packed column adopt independent vacuum systems.

[0078] In addition, in some examples, the water or water vapor used in the above steps does not contain chloride ions. For example, the water used to prepare the lye, the water vapor used in the plate column and the packed column, etc. How can the precursor substance chloride ions that produce 3-chloropropanol esters be cut off? And the implementation results show that using deionized water without chloride ions as process water and direct steam water can effectively inhibit the increase in the content of 3-chloropropanol esters in refined vegetable oil.

[0079] In some other examples of the present application, there is provided a vegetable oil prepared by the refining method as described above.

[0080] Furthermore, the vegetable oil has at least one of the following characteristics:

[0081] (1) The trans-fatty acid content < 0.3%;

[0082] (2) The glycidyl ester content < 300 μg / kg;

[0083] (3) The 3-monochloropropane-1,2-diol ester content < 400 μg / kg.

[0084] For the experimental parameters not specified in the following specific examples, comparative examples, and investigation examples, the guidance given in the present application document shall be preferentially referred to. It is also possible to refer to the experimental manuals in the art or other experimental methods known in the art, or the experimental conditions recommended by the manufacturers.

[0085] The raw materials and reagents involved in the following specific examples, comparative examples, and investigation examples can be obtained commercially, or can be prepared by those skilled in the art according to known means.

[0086] Example 1

[0087] This example is a refining method for soybean oil, and the steps are as follows:

[0088] (1) Neutralization treatment and desaponification treatment:

[0089] Mix the crude soybean oil with an alkali solution (NaOH aqueous solution, mass concentration 10%), stir at a stirring rate of 68 rpm for 15 minutes, and then transport it to a desaponification centrifuge for desaponification treatment to prepare desaponified oil, with the acid value of the desaponified oil being 0.15 mg / g;

[0090] (2) Water washing and vacuum drying treatment:

[0091] Add hot water at 95 °C accounting for 5% of the weight of the desaponified oil to conduct water washing treatment on the desaponified oil, and then heat it up to 110 °C by steam heating. Under the condition of a vacuum degree of absolute pressure 90 mbar, conduct vacuum drying treatment to prepare the first intermediate.

[0092] (3) Bleaching treatment:

[0093] Mix the first intermediate with attapulgite clay and silica gel desiccant for deodorization treatment to prepare the second intermediate; wherein the dosage of attapulgite clay is 0.8% of the weight of the first intermediate oil, and the dosage of silica gel desiccant is 10% of the mass of attapulgite clay;

[0094] (4) Deodorization treatment

[0095] Transport the second intermediate to as Figure 1The deodorization treatment is carried out in the shown deodorization device. First, it is treated with steam at 225 °C for 40 min in the plate column, and then treated with steam at 245 °C for 5 min in the packed column. The vacuum degree is 2 mbar, and the stripping steam volume is 0.5%; the refined oil is obtained as output.

[0096] In all the above steps, all materials that come into direct contact with edible soybean oil need to be treated to remove chloride ions, such as the water for preparing the alkali solution, water washing, water steam, etc.

[0097] Example 2

[0098] This example is a refining method of soybean oil. The steps are the same as those in Example 1, and the main difference is that: the water and water steam used in each step are water and water steam without chloride ion removal.

[0099] Comparative Example 1

[0100] This comparative example is a refining method of soybean oil. The steps are the same as those in Example 1, and the main difference is that: in step (1), the dosage of the alkali solution is controlled so that the de-saponification acid value is 0.3 mg / g.

[0101] Comparative Example 2

[0102] This comparative example is a refining method of soybean oil. The steps are the same as those in Example 1, and the main difference is that: in the decolorization treatment of step (3), activated clay is used to replace attapulgite clay.

[0103] The refined oils of Examples 1 - 2 and Comparative Examples 1 - 2 are detected.

[0104] Testing method:

[0105] (1) Acid value: Tested according to "the first method of GB 5009.229 - 2016".

[0106] (2) Color and luster: Tested according to "Article 3.1 of GB / T 5009.37 - 2003".

[0107] (3) Trans fatty acids: Tested according to GB 5009.257 - 2016.

[0108] (4) Glycidyl esters: Tested according to ISO 18363 - 4:2021.

[0109] (5) 3 - Chloropropanol esters: Tested according to ISO 18363 - 4:2021.

[0110] The test results are shown in Table 4 below:

[0111] Table 4

[0112]

[0113] It can be seen that through the refining method of the examples, various indicators of the finished soybean oil can be well controlled. Under the condition of ensuring the quality indicators, the content of safety risk indicators (trans fatty acids, glycidyl esters, and 3-monochloropropane-1,2-diol esters) can be effectively reduced.

[0114] Investigation Example 1

[0115] This investigation example is for verifying the excessive addition of alkali in the neutralization treatment step of the soybean oil refining method.

[0116] The amount of excessive alkali added in the neutralization treatment section is reflected by the acid value of the soapstock. Generally, it is controlled between 0.05 - 0.5 mg / g of the acid value of the soapstock (KOH). According to the steps of Example 1, control the dosage of the alkali solution in step (1) to obtain samples with different acid values of the soapstock, and conduct subsequent decolorization treatment and deodorization treatment on this sample. The practical data is shown in Table 5 below.

[0117] Table 5

[0118]

[0119] Note: The crude oil is the crude product of soybean oil.

[0120] It can be seen from the above table that: the lower the acid value of the soapstock, the less clay needed to be added in the decolorization section, and both the temperature and time required in the deodorization section are reduced, and the same finished product quality index requirements can be achieved. Excessive addition of excessive alkali affects the production yield and is not conducive to enterprise operation; too little addition of excessive alkali increases the load on subsequent processing and is not conducive to controlling safety risk indicators. Therefore, it is more balanced to control the acid value of the soapstock at about 0.15 mg / g, the production is relatively stable, especially making full preparations for reducing the deodorization temperature and shortening the deodorization time in the deodorization section.

[0121] Investigation Example 2

[0122] This investigation example is for verifying the dechlorination treatment of the soybean oil refining method.

[0123] According to the steps of Example 1, use water for preparing the alkali solution, washing water, steam, etc. that have not undergone dechlorination treatment, and at the same time replace attapulgite clay with activated clay as the control group. The process results are compared as shown in Table 6 below:

[0124] Table 6

[0125]

[0126] It can be seen that reducing the chloride ion, which is the precursor of 3-monochloropropane-1,2-diol esters, can effectively inhibit its formation at high-temperature conditions. Since it is inevitable and impossible to remove the chloride ions that are present in the raw material soybeans due to pesticide spraying during the planting process or the presence of chloride ions in the growth soil, during the refining process, it is necessary to avoid newly added chloride ions and perform deodorization at low temperature and for a short time to reduce the formation of 3-monochloropropane-1,2-diol esters.

[0127] Investigation Example 3

[0128] This investigation example is to verify the deodorization treatment parameters of the refining method of soybean oil.

[0129] After investigating the effects of deodorization temperature and time on trans fatty acids, glycidyl esters, and 3-monochloropropane-1,2-diol esters during the deodorization treatment, the parameter settings and results are shown in Table 7 below:

[0130] Table 7

[0131]

[0132] Note: Combined tower: It means that the plate tower and the packed tower are integrated as a whole, and the material temperature is the same process temperature; Plate tower + Packed tower: It means two towers, and their process temperatures can be different and can be adjusted appropriately according to needs.

[0133] It can be seen that the deodorization process 4 scheme, that is, the operating parameters of Example 1, is a balanced value for the quality index and safety risk index of the refined soybean edible oil. That is, the oil to be deodorized is first heated to 225 °C and enters the plate tower. After a residence time of 40 minutes, it is then heated to 245 °C by a high-pressure boiler for high-temperature deodorization for 5 minutes. This equipment is a packed tower, which is characterized by a short residence time of the material and good stripping and distillation effects, and can meet the various quality indexes of soybean oil refining. The direct stripping steam required for this deodorization process is formed by evaporating dechlorinated water to ensure the stripping volume of the entire deodorization. Since the residence time in the plate tower is less than that of the original process and multiple liquid levels are emptied, the direct stripping is also shut down accordingly, and the overall stripping steam consumption will be reduced compared to before, and can be reduced from the original 0.8% to 0.5% addition amount (the ratio of steam volume to oil weight) to achieve the effect of energy saving. At the same time, through this process method, zero trans fatty acids (trans fatty acid content < 0.3%) and lower contents of glycidyl esters and 3-monochloropropane-1,2-diol esters can be obtained.

[0134] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0135] The above-described embodiments merely represent several implementation manners of the present application, facilitating the specific and detailed understanding of the technical solutions of the present application, but should not be construed as limiting the scope of patent protection of the application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A refining method of vegetable oil, characterized in that, It includes the following steps: Add an alkali solution to the crude vegetable oil for neutralization treatment and soapstock removal treatment to prepare de-soaped oil; the dosage of the alkali solution is such that the acid value of the de-soaped oil is 0.1 mg / g to 0.2 mg / g; Wash and vacuum dry the de-soaped oil to prepare a first intermediate; Add a decolorizing agent and silica gel desiccant to the first intermediate for decolorization treatment to prepare a second intermediate; the decolorizing agent includes attapulgite clay; Deodorize the second intermediate, and the conditions include: the deodorization device used includes a plate column and a packed column; The second intermediate is first in the plate column and treated with steam at 220°C to 230°C for 35 min to 45 min, and then in the packed column and treated with steam at 240°C to 250°C for 3 min to 7 min.

2. The refining method of vegetable oil according to claim 1, wherein In the neutralization treatment, after adding the alkali solution to the crude vegetable oil, stir, the stirring rate is 60 rpm to 70 rpm, and the stirring time is 10 min to 30 min.

3. The refining method of vegetable oil according to claim 1, characterized in that The mass percentage of the decolorizing agent in the first intermediate is 0.5% to 1%.

4. The refining method of vegetable oil according to claim 1, characterized in that, The mass percentage of the silica gel desiccant in the decolorizing agent is 10% to 30%.

5. The refining method of vegetable oil according to any one of claims 1 to 4, characterized in that, The packed column has at least one of the following characteristics: (1) The height h of the structured packing layer satisfies: 4 m ≤ h < 5 m; (2) The direct steam pipes at the bottom of the column are arranged in a grid pattern, and the pipe spacing is 20 cm to 60 cm; (3) A flow-limiting orifice plate is provided at the direct steam inlet at the bottom of the column, and the aperture R of the flow-limiting orifice plate is 7 mm to 10 mm.

6. The refining method of vegetable oil according to any one of claims 1 to 4, characterized in that, In the plate column, the length of the sealed barrier pipe between the tower layers is inserted from the upper layer to 20 cm to 50 cm below the liquid level of the vegetable oil in the lower layer.

7. The refining method of vegetable oil according to any one of claims 1 to 4, characterized in that In the deodorization device, the plate column and the packed column adopt independent vacuum systems.

8. The refining method of vegetable oil according to any one of claims 1 to 4, characterized in that, The water or steam used in each step does not contain chloride ions.

9. Vegetable oil prepared by the refining method according to any one of claims 1 to 8.

10. The vegetable oil according to claim 9, wherein, It has at least one of the following characteristics: (1) The trans fatty acid content < 0.3%; (2) The glycidyl ester content < 300 μg / kg; (3) The 3-monochloropropanediol ester content < 400 μg / kg.

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