A method for refining soybean oil

Abstract

The present invention provides a method for refining soybean oil, comprising sequentially deacidifying, decolorizing, and deodorizing the soybean oil. During the decolorization process, an activated clay composite comprising chitosan, polysilicate, and activated clay is used as a decolorizer. During the deodorization process, the deodorization temperature is controlled at 190-220°C. The present invention also provides a method for refining soybean oil, which effectively reduces the content of 3-MCPD esters and glycidyl esters in the soybean oil by modifying the decolorization adsorbent used in the oil refining process and adaptively controlling the deodorization temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of oil refining, in particular to a method for refining soybean oil. Background Art

[0002] In recent years, the safety risks of 3-MCPD and glycidyl esters (GEs) in oils and fats have begun to attract attention. Spanish scientists treated rapeseed oil contaminated with aniline with hydrochloric acid and detected the presence of 3-MCPD. Subsequently, reports on 3-MCPD in oily foods have emerged both domestically and internationally. Since 2004, high concentrations of 3-MCPD have been detected in a variety of edible oils and heat-processed oily foods, making 3-MCPD esters a hot topic in food safety. Similarly, glycidyl esters (GEs) are composed of an epoxy group formed by the dehydration condensation of two hydroxyl groups at the 1 and 2 positions of glycerol, and an ester group formed by the esterification of another hydroxyl group with a carboxylic acid. During the vegetable oil refining process, glycidyl esters are formed by the esterification of glycidol with free fatty acids. They are another contaminant in oils and fats and pose a potential carcinogenic risk.

[0003] Research has found that 3-MCPD esters and glycidyl esters in edible oils and fats are primarily produced during the oil refining process. For example, in the bleaching process, Ramli demonstrated that an acidic environment favors the formation of 3-MCPD esters. Studies by Hrncirik et al. and Freudenstein et al. also confirm this view. This is because the acid introduced by the acidic clay provides protons, allowing chloride ions to directly attack the protonated groups of the glycerol esters, ultimately forming 3-MCPD esters. BfR suggests that glycidyl esters may be formed during the deodorization stage of oil refining. Rudiger Weibaar verified this hypothesis by studying commercially available palm oil. While no glycidyl esters were detected in unrefined oils, their presence was found in oil samples subjected to simulated refining and deodorization. Furthermore, the formation of glycidyl esters was significantly affected by simulated deodorization temperatures of 210-250°C and deodorization times ranging from 3-6 hours.

[0004] Soybean oil, a common daily oil in my country, faces significant safety concerns regarding 3-MCPD esters and glycidyl esters. Therefore, controlling the content of 3-MCPD and glycidyl esters in soybean oil is crucial for protecting human health. Prior art indicates that the selection of decolorizing adsorbents during the refining process is crucial for removing 3-MCPD and glycidyl esters (GEs) from soybean oils and other oils, as well as temperature control during the deodorization process. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method for refining soybean oil. The method effectively reduces the content of 3-MCPD esters and glycidyl esters in soybean oil by modifying the decolorization adsorbent used in the oil refining process and adaptively controlling the deodorization temperature.

[0006] The present invention provides a method for refining soybean oil, comprising sequentially performing deacidification, decolorization and deodorization treatments on the soybean oil;

[0007] In the decolorization process, an activated clay complex is used as a decolorizer, and the activated clay complex comprises chitosan, polysilicate and activated clay; in the deodorization process, the deodorization temperature is controlled at 190-220°C.

[0008] Preferably, the activated clay composite comprises 2-8 parts of chitosan, 6-12 parts of polysilicate and 10-20 parts of activated clay in parts by weight.

[0009] Preferably, the chitosan is chitosan with a weight average molecular weight of 300,000-600,000 and a deacetylation degree greater than 85%; and the polysilicate is magnesium polysilicate or calcium polysilicate.

[0010] Preferably, the activated clay composite is obtained by adding activated clay and polysilicate into a chitosan colloidal solution, mixing the mixture, and drying the mixture.

[0011] Preferably, the "deacidification treatment of soybean oil" specifically includes: adding alkali solution to the soybean oil for alkali refining, and then adding hot water to wash and remove soap to complete the deacidification; preferably, the alkali solution is a sodium hydroxide solution with a concentration of 1-30wt%; further preferably, the temperature of the alkali refining is 85-95°C and the time is 20-30min.

[0012] Preferably, the "decolorization treatment of soybean oil" specifically includes: maintaining vacuum conditions, adding an activated clay complex to the soybean oil to react to complete decolorization; preferably, the amount of the activated clay complex added is 1-10wt% of the soybean oil; further preferably, the reaction temperature is 95-105°C and the reaction time is 30-40min.

[0013] Preferably, the "deodorizing soybean oil" specifically includes: using water vapor as a deodorizing medium, adding an acidic compound to the soybean oil for distillation to complete the deodorization; preferably, the acidic compound is one or more of citric acid, succinic acid or propionic acid; further preferably, the amount of the acidic compound is 0.01-0.1wt% of the soybean oil.

[0014] The vacuum degree of the deodorization treatment is not higher than 2000 Pa, and the time is 30-45 minutes.

[0015] The present invention provides refined soybean oil, which is prepared by the method.

[0016] Preferably, the 3-MCPD ester content in the refined soybean oil is lower than 0.2 ppm, and the glycidyl ester content is also lower than 0.2 ppm.

[0017] In the method for refining soybean oil of the present invention, a composite comprising chitosan, polysilicate, and activated clay is selected as a decolorizing adsorbent. Since the decolorizing adsorbent can effectively adsorb aldehyde compounds, peroxides, and colored substances in soybean oil, it can not only effectively reduce the impurity content in the oil, but also inhibit the formation of 3-MCPD esters and glycidyl esters, thereby having an unexpected effect on reducing the content of chloropropane esters and glycidyl esters. Subsequently, by regulating the temperature during the deodorization process, it is not only possible to ensure that the soybean oil is fully deodorized, but also to inhibit the formation of 3-MCPD esters and glycidyl esters under high temperature conditions. After the above-mentioned refining treatment, the content of 3-MCPD esters and glycidyl esters in the soybean oil can be controlled to below 0.2ppm. DETAILED DESCRIPTION

[0018] Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments. However, it should be clearly stated that these embodiments are provided for illustration only and are not to be construed as limiting the scope of the present invention.

[0019] Example 1

[0020] A method for refining soybean oil, comprising:

[0021] (1) Deacidification: Soybean crude oil was subjected to a conventional degumming process (specifically, the soybean crude oil was thoroughly mixed with 10% pure water by weight of the oil and 0.05% phosphoric acid solution (85 wt%) by weight of the oil, stirred for 15 min, and then centrifuged to obtain degummed crude oil. NaOH solution (15 wt%) was added to the degummed crude oil. The amount of alkali added was 7.13 × 10 -4 × oil weight × acid value × (1 + 20%), stir at 90 ° C for 30 minutes, centrifuge while hot to take the oil phase, then add hot water (85 ° C) with a content of 20wt% of the oil weight and mix and stir for 10 minutes, centrifuge and dry in vacuum at 90 ° C for 10 minutes to obtain deacidified crude oil;

[0022] (2) Decolorization: The deacidified crude oil was heated to 100° C., an activated clay compound (5% by weight of the oil) was added, and the mixture was stirred and kept warm for 30 min under a vacuum of 4 kPa. The activated clay compound was removed by centrifugation to obtain decolorized crude oil, wherein the activated clay compound was prepared by the following method: 15 parts by weight of chitosan powder (weight average molecular weight 400,000, degree of deacetylation greater than 85%) was dissolved in an acetic acid aqueous solution (2 wt%) to form a colloidal solution, and the mixture was heated to 50° C., and then 25 parts by weight of magnesium polysilicate and 45 parts by weight of activated clay were added. , ultrasonically mixing for 30 minutes, and then drying at 120° C. to obtain the activated white clay composite; here, the magnesium polysilicate is prepared by the following method: dissolving sodium silicate in water to obtain a water glass solution (0.5 mol / L), then slowly adding the water glass solution dropwise to hydrochloric acid (1 mol / L) until the pH = 2, standing and activating for 30 minutes, adding a magnesium sulfate (0.5 times the weight of sodium silicate) solution and mixing, standing and aging for 180 minutes to obtain a gel solution, drying the gel solution at 120° C., and grinding it into powder to obtain the magnesium polysilicate;

[0023] (3) Deodorization: The deacidified crude oil was heated to 210° C., and water vapor was introduced into the decolorized crude oil as a deodorizing medium. The temperature was maintained at a vacuum of 200 Pa for 40 min, during which the amount of water vapor introduced was 2.0% (w / w) relative to the oil sample. After cooling to 50° C., the vacuum was broken and the introduction of water vapor was stopped. The crude oil was then centrifuged to obtain refined soybean oil.

[0024] Example 2

[0025] A method for refining soybean oil, comprising:

[0026] (1) Deacidification: Soybean crude oil was subjected to a conventional degumming process (specifically, the soybean crude oil was thoroughly mixed with 10% pure water by weight of the oil and 0.05% phosphoric acid solution (85 wt%) by weight of the oil, stirred for 15 min, and then centrifuged to obtain degummed crude oil. NaOH solution (15 wt%) was added to the degummed crude oil. The amount of alkali added was 7.13 × 10 -4 × oil weight × acid value × (1 + 10%), stir at 95 ° C for 20 minutes, centrifuge while hot to obtain the oil phase, then add hot water (85 ° C) with a content of 20 wt% of the oil weight and mix and stir for 10 minutes, centrifuge and vacuum dry at 90 ° C for 10 minutes to obtain deacidified crude oil;

[0027] (2) Decolorization: The deacidified crude oil was heated to 95° C., an activated clay compound (1% by weight of the oil) was added, and the mixture was stirred and reacted for 40 min under a vacuum of 4 kPa. The activated clay compound was removed by centrifugation to obtain decolorized crude oil, wherein the activated clay compound was prepared by the following method: 15 parts by weight of chitosan powder (weight average molecular weight 600,000, degree of deacetylation greater than 85%) was dissolved in an acetic acid aqueous solution (2 wt%) to form a colloidal solution, and the mixture was heated to 50° C., and then 12 parts by weight of magnesium polysilicate and 37 parts by weight of activated clay were added. , ultrasonically mixing for 30 minutes, and then drying at 120° C. to obtain the activated white clay composite; here, the magnesium polysilicate is prepared by the following method: dissolving sodium silicate in water to obtain a water glass solution (0.5 mol / L), then slowly adding the water glass solution dropwise to hydrochloric acid (1 mol / L) until the pH = 2, standing and activating for 30 minutes, adding a magnesium sulfate (0.5 times the weight of sodium silicate) solution and mixing, standing and aging for 180 minutes to obtain a gel solution, drying the gel solution at 120° C., and grinding it into powder to obtain the magnesium polysilicate;

[0028] (3) Deodorization: 0.05 wt% of citric acid was added to the deacidified crude oil, and the temperature was raised to 220° C. Water vapor was introduced into the decolorized crude oil as a deodorizing medium. The temperature was maintained at a vacuum of 500 Pa for 30 minutes, during which the amount of water vapor introduced was 2.5% (w / w) relative to the oil sample. After cooling to 50° C., the vacuum was broken and the introduction of water vapor was stopped. The crude oil was then centrifuged to obtain refined soybean oil.

[0029] Example 3

[0030] A method for refining soybean oil, comprising:

[0031] (1) Deacidification: Soybean crude oil was subjected to a conventional degumming process (specifically, the soybean crude oil was thoroughly mixed with 10% pure water by weight of the oil and 0.05% phosphoric acid solution (85 wt%) by weight of the oil, stirred for 15 min, and then centrifuged to obtain degummed crude oil. NaOH solution (15 wt%) was added to the degummed crude oil. The amount of alkali added was 7.13 × 10 -4 × oil weight × acid value × (1 + 20%), stir at 85 ° C for 30 minutes, centrifuge while hot to take the oil phase, then add hot water (85 ° C) with a content of 20wt% of the oil weight and mix and stir for 10 minutes, centrifuge and vacuum dry at 90 ° C for 10 minutes to obtain deacidified crude oil;

[0032] (2) Decolorization: The deacidified crude oil is heated to 105° C., an activated clay compound (10% by weight of the oil) is added, and the mixture is stirred and kept warm for 30 min under a vacuum of 4 kPa. The activated clay compound is removed by centrifugation to obtain decolorized crude oil, wherein the activated clay compound is prepared by the following method: 10 parts by weight of chitosan powder (weight average molecular weight 300,000, degree of deacetylation greater than 85%) is dissolved in an acetic acid aqueous solution (2 wt%) to form a colloidal solution, and the mixture is heated to 50° C. and then 60 parts by weight of calcium polysilicate and 50 parts by weight of activated clay are added. soil, ultrasonically mixed for 30 minutes, and then dried at 120° C. to obtain the activated white clay composite; here, the calcium polysilicate is prepared by the following method: sodium silicate is dissolved in water to obtain a water glass solution (0.5 mol / L), and then the water glass solution is slowly added dropwise to hydrochloric acid (1 mol / L) until the pH is 2, and after standing for activation for 30 minutes, a calcium chloride solution (0.4 times the weight of sodium silicate) is added and mixed, and after standing for aging for 180 minutes, a gel solution is obtained, and the gel solution is dried at 120° C. and ground into powder to obtain the calcium polysilicate;

[0033] (3) Deodorization: The deacidified crude oil was heated to 190° C., and water vapor was introduced into the decolorized crude oil as a deodorizing medium. The temperature was maintained at a vacuum of 100 Pa for 45 minutes. During this period, the amount of water vapor introduced was 2.0% (w / w) relative to the oil sample. After cooling to 50° C., the vacuum was broken and the introduction of water vapor was stopped. The crude oil was then centrifuged to obtain refined soybean oil.

[0034] Comparative Example 1

[0035] A method for refining soybean oil, comprising:

[0036] (1) Deacidification: Soybean crude oil was subjected to a conventional degumming process (specifically, the soybean crude oil was thoroughly mixed with 10% pure water by weight of the oil and 0.05% phosphoric acid solution (85 wt%) by weight of the oil, stirred for 15 min, and then centrifuged to obtain degummed crude oil. NaOH solution (15 wt%) was added to the degummed crude oil. The amount of alkali added was 7.13 × 10 -4 × oil weight × acid value × (1 + 20%), stir at 90 ° C for 30 minutes, centrifuge while hot to take the oil phase, then add hot water (85 ° C) with a content of 20wt% of the oil weight and mix and stir for 10 minutes, centrifuge and dry in vacuum at 90 ° C for 10 minutes to obtain deacidified crude oil;

[0037] (2) Decolorization: The deacidified crude oil was heated to 100° C., activated clay (5% by weight of the oil) was added, and the mixture was stirred and reacted at a vacuum of 4 kPa for 30 min. The activated clay complex was removed by centrifugation to obtain decolorized crude oil.

[0038] (3) Deodorization: The deacidified crude oil was heated to 210° C., and water vapor was introduced into the decolorized crude oil as a deodorizing medium. The temperature was maintained at a vacuum of 200 Pa for 40 min, during which the amount of water vapor introduced was 2.0% (w / w) relative to the oil sample. After cooling to 50° C., the vacuum was broken and the introduction of water vapor was stopped. The crude oil was then centrifuged to obtain refined soybean oil.

[0039] Comparative Example 2

[0040] A method for refining soybean oil, comprising:

[0041] (1) Deacidification: Soybean crude oil was subjected to a conventional degumming process (specifically, the soybean crude oil was thoroughly mixed with 10% pure water by weight of the oil and 0.05% phosphoric acid solution (85 wt%) by weight of the oil, stirred for 15 min, and then centrifuged to obtain degummed crude oil. NaOH solution (15 wt%) was added to the degummed crude oil. The amount of alkali added was 7.13 × 10 -4 × oil weight × acid value × (1 + 20%), stir at 90 ° C for 30 minutes, centrifuge while hot to take the oil phase, then add hot water (85 ° C) with a content of 20wt% of the oil weight and mix and stir for 10 minutes, centrifuge and dry in vacuum at 90 ° C for 10 minutes to obtain deacidified crude oil;

[0042] (2) Decolorization: The deacidified crude oil was heated to 100° C., activated clay (5% by weight of the oil) was added, and the mixture was stirred and reacted at a vacuum of 4 kPa for 30 min. The activated clay complex was removed by centrifugation to obtain decolorized crude oil.

[0043] (3) Deodorization: The deacidified crude oil was heated to 230° C., and water vapor was introduced into the decolorized crude oil as a deodorizing medium. The temperature was maintained at a vacuum of 200 Pa for 40 min. During this period, the amount of water vapor introduced was 2.0% (w / w) relative to the oil sample. After cooling to 50° C., the vacuum was broken and the introduction of water vapor was stopped. The crude oil was then centrifuged to obtain refined soybean oil.

[0044] The refined soybean oils after treatment in Examples 1-3 and Comparative Examples 1-2 were characterized, and the results are shown in the following table:

[0045] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 3-MCPD ester, ppm 0.16 0.13 0.19 0.63 0.98 Glycidyl esters, ppm 0.12 ＜0.1 0.15 0.76 1.01

[0046] The 3-MCPD esters and glycidyl esters in the table were tested according to the method in GB 5009.191-2016 Determination of 3-MCPD and their fatty acid esters in foods. 3-MCPD and glycidyl esters in oils and fats were indirectly determined by acid hydrolysis and quantified by GC-MS using an isotopic internal standard.

[0047] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for refining soybean oil, characterized in that, The method comprises sequentially performing deacidification, decolorization and deodorization treatments on soybean oil; In the decolorization process, an activated clay compound is used as a decolorizer, and the activated clay compound comprises chitosan, polysilicate and activated clay; in the deodorization process, the deodorization temperature is controlled at 190-220°C; The activated clay composite is obtained by adding activated clay and polysilicate into a chitosan colloidal solution, mixing the mixture evenly, and then drying the mixture; the polysilicate is magnesium polysilicate or calcium polysilicate.

2. The method for refining soybean oil according to claim 1, wherein In parts by weight, the activated clay composite comprises 2-8 parts of chitosan, 6-12 parts of polysilicate and 10-20 parts of activated clay.

3. The method for refining soybean oil according to claim 1 or 2, characterized in that The chitosan has a weight-average molecular weight of 300,000 to 600,000 and a deacetylation degree greater than 85%.

4. The method for refining soybean oil according to claim 1 or 2, characterized in that The deacidification treatment of soybean oil specifically includes: adding alkali solution to the soybean oil for alkali refining, and then adding hot water for washing and removing soap to complete the deacidification.

5. The method for refining soybean oil according to claim 4, wherein The alkali solution is a sodium hydroxide solution with a concentration of 1-30 wt %; the temperature of the alkali refining is 85-95° C., and the time is 20-30 min.

6. The method for refining soybean oil according to claim 1 or 2, characterized in that: The decolorization treatment of soybean oil specifically includes: adding an activated clay complex to the soybean oil under vacuum conditions to react and complete decolorization.

7. The method for refining soybean oil according to claim 6, wherein: The addition amount of the activated clay compound is 1-10 wt% of the soybean oil; the reaction temperature is 95-105° C., and the reaction time is 30-40 minutes.

8. The method for refining soybean oil according to claim 1 or 2, characterized in that: The deodorization treatment of soybean oil specifically includes: using water vapor as a deodorization medium, adding acidic compounds into the soybean oil and performing distillation to complete the deodorization.

9. The method for refining soybean oil according to claim 8, wherein The acidic compound is one or more of citric acid, succinic acid or propionic acid; the amount of the acidic compound is 0.01-0.1 wt % of the soybean oil.

10. The method for refining soybean oil according to claim 9, characterized in that: The vacuum degree of the deodorization treatment is not higher than 2000 Pa, and the time is 30-45 minutes.

11. A refined soybean oil, characterized in that The invention is prepared by the method according to any one of claims 1 to 10.

12. The refined soybean oil according to claim 11, characterized in that The 3-MCPD ester content in the refined soybean oil is lower than 0.2 ppm, and the glycidyl ester content is also lower than 0.2 ppm.