A method for reducing the content of 3-chloropropanol esters and glycidyl esters in edible oils

Abstract

The present application relates to a kind of methods for reducing the content of 3-chloropropanol ester and glycidyl ester in edible oil, belongs to the technical field of edible oil production.The method described in the present application includes steps such as hydration degumming, alkali refining deacidification, adsorption and decolorization by composite adsorbent, distillation and deodorization.Using the method of the present application can significantly inhibit the increase of 3-chloropropanol ester and glycidyl ester content in oil during the deodorization process, and the content of 3-chloropropanol ester and glycidyl ester in the obtained edible oil is low, and lower than the European standard, which can effectively ensure the edible safety of edible oil.

Description

Technical Field

[0001] This invention belongs to the field of edible oil production technology and relates to a method for reducing the content of 3-chloropropanol esters and glycidyl esters in edible oils. Background Technology

[0002] Edible oil, also known as cooking oil, refers to animal or vegetable fats used in food preparation. It is liquid at room temperature. Due to factors such as raw material source, processing technology, and quality, most common edible oils are vegetable oils. Vegetable edible oils are an important source of nutrition for the human body and are often consumed directly or used as raw materials in food processing. The quality and safety of edible oils have always been a hot topic in the food industry. 3-Chloropropanol esters and glycidyl esters are oil contamination issues that have received widespread attention in recent years. These are hazardous components generated during oil processing in the presence of chlorine compounds, primarily under the high-temperature conditions of the processing. Reports both domestically and internationally indicate that 3-chloropropanol esters and glycidyl esters are widely present in oils, and in recent years, high concentrations of these esters have been detected in oils, indicating a significant contamination problem.

[0003] Literature reports that the deodorization process of corn oil has a significant impact on the content of 3-chloropropanol esters and glycidyl esters in the oil. Their content increases with increasing deodorization temperature and prolonged deodorization time. In unrefined natural oils and crude oils, the content of 3-chloropropanol esters and glycidyl esters is low or undetectable. However, the quality of raw materials affects the content of 3-chloropropanol esters and glycidyl esters in the oil. Furthermore, the formation of 3-chloropropanol esters and glycidyl esters in crude oils is related to the heat treatment conditions during the oilseed processing and the oil refining process. Summary of the Invention

[0004] The main objective of this invention is to provide a method for reducing the content of 3-chloropropanol esters and glycidyl esters in edible oils. Using this method, the content of 3-chloropropanol esters and glycidyl esters in edible oils can be significantly reduced, thus fully ensuring the safety of edible oils for consumption.

[0005] The present invention employs the following technical solutions to achieve the above objectives:

[0006] A method for reducing the content of 3-chloropropanol esters and glycidyl esters in edible oils specifically includes the following steps:

[0007] Step 1, hydration and degumming: Place the crude edible oil in a stirrer and heat it to 25-30℃. While stirring, add distilled water containing diosgenin at the same temperature and continue stirring for 20-30 minutes. Then heat it to 85-95℃ and continue stirring until the oil foot separates. Stop stirring 3-5 minutes later, let it stand and cool to room temperature, centrifuge for 20-25 minutes, and take the upper hydrated oil to obtain hydrated degummed oil for later use.

[0008] Step 2, alkali refining and deacidification: Add alkali solution to the hydrated degummed oil obtained in Step 1, heat to 90-95℃ while stirring, maintain constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, take the upper layer of alkali-refined semi-clean oil, heat to 90-95℃, add distilled water and wash 2-3 times; heat the washed oil to dehydrate and dry, to obtain alkali-refined deacidified oil for later use.

[0009] Step 3, adsorption and decolorization: The alkali-refined deacidified oil obtained in step 2 is heated to 90-95℃ under negative pressure and stirred to dehydrate. Then, the adsorbent is added and stirred evenly. The decolorization is carried out for 25-30 minutes. The oil and adsorbent mixture is centrifuged to separate the adsorbent, and the decolorized clean oil is obtained.

[0010] Step 4, distillation and deodorization: Place the decolorized clean oil obtained in step 3 into a deodorization device, heat the oil to 250-260℃ under vacuum, introduce steam, deodorize for 2 hours, turn off the steam, and cool to room temperature to obtain deodorized oil.

[0011] Furthermore, the mass fraction of diosgenin in step 1 is 8-10%.

[0012] Furthermore, in step 3, the amount of adsorbent used is 3-5% of the mass of the alkali-refined deacidified oil.

[0013] Furthermore, in step 3, the adsorbent is a modified chitosan-sodium alginate-clay composite adsorbent.

[0014] Furthermore, the preparation method of the adsorbent in step 3 is as follows:

[0015] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; soak the scallop shell powder in a 20-25% phosphoric acid solution for 6-8 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 500-600℃ for 2-3 hours; cool the calcined product to room temperature, add distilled water and mix well; then add chitosan, heat to 50-60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I.

[0016] Step B: Add distilled water at 40-50℃ to sodium alginate, stir until a viscous solution is formed under heat preservation, add calcium sulfite, mix well, dry, and pulverize to obtain product II.

[0017] Step C: Mix the obtained product I, product II, and bleaching clay to obtain the composite adsorbent.

[0018] Furthermore, in step A, the mass-to-volume ratio of scallop shell powder to distilled water is 1:(8-10) in kg / L.

[0019] Furthermore, in step A, the amount of chitosan added is 5-6 times the mass of scallop shell powder.

[0020] Furthermore, in step B, the mass ratio of sodium alginate to calcium sulfite is 1:(0.3-0.4).

[0021] Furthermore, in step C, the mass ratio of product I, product II, and clay is 1:(1-1.2):(2-3).

[0022] The present invention has the following beneficial effects:

[0023] This invention optimizes the edible oil production and refining process, effectively reducing the content of 3-chloropropanol esters and glycidyl esters in the oil, thus ensuring the safety of the edible oil. The method provided by this invention includes hydration and degumming with purified water containing diosgenin, followed by alkali refining and deacidification, adsorption and decolorization using a specific composite adsorbent, and finally deodorization to obtain the finished edible oil product. Using this method, the deodorization stage can significantly reduce the content of 3-chloropropanol esters and glycidyl esters, resulting in a significantly lower content compared to traditional refining processes. In the refining process, the inventors optimized the adsorbent, not using the traditional single bleaching clay adsorbent, but instead employing a modified chitosan-sodium alginate-bleaching clay composite adsorbent. During the chitosan modification process, biochar prepared from seashell powder was added, and calcium sulfite was added to the sodium alginate, increasing the adsorption capacity of the adsorbent and also enhancing its adsorption of chloride ions, thus reducing the chloride ion content in the oil and preventing an increase in 3-chloropropanol ester content due to the presence of chloride ions during deodorization. Furthermore, in the hydration and degumming stage, diosgenin was added to the purified water. Diosgenin can maintain the stability of the oil to a certain extent and reduce the formation of glycidyl esters. The various technical points in this invention work together to inhibit the content of 3-chloropropanol esters and glycidyl esters during the deodorization process in oil production. Attached Figure Description

[0024] Figure 1 Chloride ion content in edible oil samples in each implementation method;

[0025] Figure 2 : Content of 3-chloropropanol ester in edible oil samples in each embodiment;

[0026] Figure 3 : Glycidyl ester content of edible oil samples in each implementation method. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope of protection of the claims of this application.

[0028] Example 1

[0029] Preparation of composite adsorbents:

[0030] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 25% phosphoric acid solution for 6 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 600℃ for 2 hours; after cooling the calcined product to room temperature, add 10 L of distilled water and mix well; then add 6 kg of chitosan, heat to 60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I.

[0031] Step B: Add 50°C distilled water to 1 kg of sodium alginate, stir until a viscous solution is formed under heat preservation, add 0.3 kg of calcium sulfite, mix well, dry, and pulverize to obtain product II.

[0032] Step C: Mix 1 kg of product I, 1 kg of product II, and 2 kg of bleaching clay to obtain the composite adsorbent.

[0033] Edible oil refining:

[0034] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 2.108mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 3.162g of distilled water at the same temperature containing diosgenin (mass fraction of 10%), continue stirring for 20min, then heat to 95℃ and continue stirring until the oil foot separates. Stop stirring 3min after that, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0035] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.635 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (72.32 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and add distilled water at 15% of the oil mass each time for washing twice. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0036] Step 3, adsorption and decolorization: Heat 200g of alkali-refined deacidified oil to 95℃ under negative pressure and stir to dehydrate until no mist is visible on the oil surface. Then weigh 5% of the oil mass of the above-obtained composite adsorbent, stir evenly, decolorize for 25 minutes, centrifuge the oil and adsorbent mixture to separate the adsorbent, and obtain decolorized clean oil.

[0037] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0038] Example 2

[0039] Preparation of composite adsorbents:

[0040] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 20% phosphoric acid solution for 8 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 500℃ for 3 hours; cool the calcined product to room temperature, add 8 L of distilled water and mix well; then add 5 kg of chitosan, heat to 50℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I.

[0041] Step B: Add 1 kg of sodium alginate to 40°C distilled water, stir under heat until a viscous solution is formed, add 0.4 kg of calcium sulfite, mix well, dry, and pulverize to obtain product II.

[0042] Step C: Mix 1 kg of product I, 1.2 kg of product II, and 3 kg of bleaching clay to obtain the composite adsorbent.

[0043] Edible oil refining:

[0044] Step 1, hydration and degumming: Take 500g of crude peanut oil (its phospholipid content was determined to be 2.638mg / g), place it in a heated magnetic stirrer and heat it to 25℃. While stirring, add 3.957g of distilled water at the same temperature containing diosgenin (mass fraction of 8%), continue stirring for 30min, then heat to 85℃ and continue stirring until the oil foot separates. Stop stirring 5min after that, let it stand and cool to room temperature, centrifuge for 20min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0045] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (the crude peanut oil acid value calculated as KOH is 4.319 mg / g) and the excess alkali amount of 0.2% of the oil mass (67.39 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above, add the alkali solution while stirring, and simultaneously raise the temperature to 90°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Raise the temperature to 90°C, and add distilled water at 15% of the oil mass each time to wash 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0046] Step 3, adsorption and decolorization: 200g of alkali-refined deacidified oil is heated to 90℃ under negative pressure and stirred to dehydrate until no mist is visible on the oil surface. Then, 3% of the oil mass of the above-obtained composite adsorbent is weighed, stirred evenly, and decolorized for 30 minutes. The oil and adsorbent mixture is centrifuged to separate the adsorbent, and the decolorized clean oil is obtained.

[0047] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 250°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, then turn off the steam and cool the oil to room temperature to obtain the deodorized oil.

[0048] Example 3

[0049] Preparation of composite adsorbents:

[0050] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 20% phosphoric acid solution for 7 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 600℃ for 2 hours; after cooling the calcined product to room temperature, add 9 L of distilled water and mix well; then add 5.5 kg of chitosan, heat to 60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I;

[0051] Step B: Add 50°C distilled water to 1 kg of sodium alginate, stir until a viscous solution is formed under heat preservation, add 0.35 kg of calcium sulfite, mix well, dry, and pulverize to obtain product II.

[0052] Step C: Mix 1 kg of product I, 1.1 kg of product II, and 2.5 kg of clay to obtain the composite adsorbent.

[0053] Edible oil refining:

[0054] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction of 9%), continue stirring for 20min, then heat to 95℃ and continue stirring until the oil foot separates. Stop stirring 4min after that, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0055] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0056] Step 3, adsorption and decolorization: Heat 200g of alkali-refined deacidified oil to 95℃ under negative pressure and stir to dehydrate until no mist is visible on the oil surface. Then weigh 4% of the oil mass of the above-obtained composite adsorbent, stir evenly, decolorize for 30 minutes, centrifuge the oil and adsorbent mixture to separate the adsorbent, and obtain decolorized clean oil.

[0057] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0058] Comparative Example 1

[0059] Preparation of composite adsorbents:

[0060] Step A: Add 50°C distilled water to 1 kg of sodium alginate, stir until a viscous solution is formed under heat preservation, add 0.35 kg of calcium sulfite, mix well, dry, and pulverize to obtain product I;

[0061] Step B: Mix 1 kg of product I and 1.25 kg of bleaching clay to obtain the composite adsorbent.

[0062] Edible oil refining:

[0063] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction of 9%), continue stirring for 20min, then heat to 95℃ and continue stirring until the oil foot separates. Stop stirring 4min after that, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0064] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0065] Step 3, adsorption and decolorization: Heat 200g of alkali-refined deacidified oil to 95℃ under negative pressure and stir to dehydrate until no mist is visible on the oil surface. Then weigh 4% of the oil mass of the above-obtained composite adsorbent, stir evenly, decolorize for 30 minutes, centrifuge the oil and adsorbent mixture to separate the adsorbent, and obtain decolorized clean oil.

[0066] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0067] Comparative Example 2

[0068] Preparation of composite adsorbents:

[0069] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 20% phosphoric acid solution for 7 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 600℃ for 2 hours; after cooling the calcined product to room temperature, add 9 L of distilled water and mix well; then add 5.5 kg of chitosan, heat to 60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I;

[0070] Step B: Mix 1 kg of product I and 1.25 kg of bleaching clay to obtain the composite adsorbent.

[0071] Edible oil refining:

[0072] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction of 9%), continue stirring for 20min, then heat to 95℃ and continue stirring until the oil foot separates. Stop stirring 4min after that, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0073] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0074] Step 3, adsorption and decolorization: Heat 200g of alkali-refined deacidified oil to 95℃ under negative pressure and stir to dehydrate until no mist is visible on the oil surface. Then weigh 4% of the oil mass of the above-obtained composite adsorbent, stir evenly, decolorize for 30 minutes, centrifuge the oil and adsorbent mixture to separate the adsorbent, and obtain decolorized clean oil.

[0075] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0076] Comparative Example 3

[0077] Edible oil refining:

[0078] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction of 9%), continue stirring for 20min, then heat to 95℃ and continue stirring until the oil foot separates. Stop stirring 4min after that, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0079] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0080] Step 3, adsorption and decolorization: Heat 200g of alkali-refined deacidified oil to 95℃ under negative pressure and stir to dehydrate until no mist is visible on the oil surface. Then weigh 4% of the oil mass of white clay, stir evenly, and decolorize for 30 minutes. Centrifuge the oil and adsorbent mixture to separate the adsorbent, and the decolorized clean oil is obtained.

[0081] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0082] Comparative Example 4

[0083] Preparation of composite adsorbents:

[0084] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 20% phosphoric acid solution for 7 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 600℃ for 2 hours; after cooling the calcined product to room temperature, add 9 L of distilled water and mix well; then add 5.5 kg of chitosan, heat to 60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I;

[0085] Step B: Add 50°C distilled water to 1 kg of sodium alginate, stir until a viscous solution is formed under heat preservation, add 0.35 kg of calcium sulfite, mix well, dry, and pulverize to obtain product II.

[0086] Step C: Mix 1 kg of product I, 1.1 kg of product II, and 2.5 kg of clay to obtain the composite adsorbent.

[0087] Edible oil refining:

[0088] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature and continue stirring for 20min. Then heat it to 95℃ and continue stirring until the oil foot separates. Stop stirring after 4min, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0089] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0090] Step 3, adsorption and decolorization: 200g of alkali-refined deacidified oil is heated to 95℃ under negative pressure and stirred to dehydrate until no mist is visible on the oil surface. Then, 4% of the oil mass is weighed to obtain the above-mentioned composite adsorbent. Stir evenly and decolorize for 30 minutes. Centrifuge the oil and adsorbent mixture to separate the adsorbent, and the decolorized clean oil is obtained.

[0091] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0092] Comparative Example 5

[0093] Preparation of composite adsorbents:

[0094] Step A: Crush scallop shells, sieve them to obtain scallop shell powder; Soak 1 kg of scallop shell powder in a 20% phosphoric acid solution for 7 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 600℃ for 2 hours; cool the calcined product to room temperature, add 9 L of distilled water and mix well; then add 2 kg of chitosan and 2.5 kg of sodium alginate; heat to 60℃ and stir until viscous under heat preservation; cool, dry, and crush to obtain product I.

[0095] Step B: Mix 1 kg of product I and 1.25 kg of bleaching clay to obtain the composite adsorbent.

[0096] Edible oil refining:

[0097] Step 1, hydration and degumming: Take 500g of crude corn oil (its phospholipid content was determined to be 3.027mg / g), place it in a heated magnetic stirrer and heat it to 30℃. While stirring, add 4.54g of distilled water at the same temperature and continue stirring for 20min. Then heat it to 95℃ and continue stirring until the oil foot separates. Stop stirring after 4min, let it stand and cool to room temperature, centrifuge for 25min, and take the upper hydrated oil to obtain hydrated degummed oil.

[0098] Step 2, alkali refining and deacidification: The amount of alkali added for alkali refining and deacidification is the sum of the theoretical alkali addition amount calculated based on the crude oil acid value (4.062 mg / g of crude corn oil calculated using KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL). The mass fraction of the alkali solution used is 6.58%. Weigh 300 g of the hydrated degummed oil obtained above and add the alkali solution while stirring, simultaneously raising the temperature to 95°C. Maintain a constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, and take the upper layer of alkali-refined semi-clean oil. Heat it to 95°C, and each time add 15% of the oil mass of distilled water to wash it 3 times. After washing, heat the oil to dehydrate and dry it to obtain alkali-refined deacidified oil for later use.

[0099] Step 3, adsorption and decolorization: 200g of alkali-refined deacidified oil is heated to 95℃ under negative pressure and stirred to dehydrate until no mist is visible on the oil surface. Then, 4% of the oil mass is weighed to obtain the above-mentioned composite adsorbent. Stir evenly and decolorize for 30 minutes. Centrifuge the oil and adsorbent mixture to separate the adsorbent, and the decolorized clean oil is obtained.

[0100] Step 4, distillation and deodorization: Place 100g of the decolorized purified oil obtained above into a deodorization device, start the vacuum pump, and slowly heat the oil to 260°C when the system pressure is below 400Pa. Introduce steam, and maximize the ventilation volume and keep the flow rate constant without causing oil splashing. Deodorize for 2 hours, turn off the steam, and cool the oil to room temperature to obtain the deodorized oil.

[0101] Performance testing

[0102] The contents of chloride ions, 3-chloropropanol esters (3-MCPD esters), and glycidyl esters (GEs) in the oil samples from each step of the methods described in Examples 1-3 and Comparative Examples 1-5 were determined using conventional detection methods. The results are shown in the appendix. Figure 1-3 .

[0103] Existing literature indicates that the chloride ion content in edible oils affects the 3-MCPD ester content. In traditional refining processes, the steps before deodorization have little impact on 3-MCPD ester formation, as chloride ions are removed during the separation of oil residue, soap residue, and waste bleaching clay. The deodorization process is the main stage for 3-MCPD ester formation; while chloride ion levels decrease during this stage, the 3-MCPD ester content increases significantly. The reduction in chloride ion content during deodorization contributes to 3-MCPD ester formation. Furthermore, the content of glycidyl esters also increases significantly after deodorization in traditional processes.

[0104] Self-attached Figure 1 As can be seen, the chloride ion content in peanut oil or corn oil gradually decreases during the refining process, and the changes in chloride ion content are not significantly different in each implementation method. However, the attached document... Figure 2 The results show that the corn oil in Comparative Example 5, processed using a traditional refining process, exhibited a significant increase in 3-MCPD ester content after deodorization. Compared to before deodorization, the 3-MCPD ester content increased to 3.72 mg / kg, representing an increase of 1282.76%, consistent with the information disclosed in the literature. However, in the deodorized oil samples of Examples 1-3, the increase in 3-MCPD ester content was relatively small, all below 0.5 mg / kg. The methods used in Comparative Examples 1-4 differed from those in this invention (e.g., adsorbent preparation method, component addition, etc.), resulting in a significant increase in 3-MCPD ester content in the oil samples after deodorization, although the increase was smaller compared to that in Comparative Example 5.

[0105] Self-attached Figure 3 As can be seen, the glycidyl ester content decreases during the refining stage before deodorization, and there is basically no significant difference between the various implementation methods. However, after the deodorization stage, the glycidyl ester content in the oil sample of Comparative Example 5 increases significantly, which is consistent with the prior art. However, the increase in glycidyl ester content in the samples after deodorization in Examples 1-3 is not significant, with the increase being less than 1 mg / kg. In Comparative Examples 1-4, the increase in glycidyl ester content is more than 1 mg / kg, but the increase is smaller compared to Comparative Example 5.

[0106] Therefore, the method provided by this invention can effectively reduce the content of 3-chloropropanol esters and glycidyl esters in edible oils, ensuring the safety of edible oils for consumption.

Claims

1. A method for reducing the content of 3-chloropropanol esters and glycidyl esters in edible oils, characterized in that, Includes the following steps: Step 1, hydration and degumming: Place the crude edible oil in a stirrer and heat it to 25-30℃. While stirring, add distilled water containing diosgenin at the same temperature and continue stirring for 20-30 minutes. Then, raise the temperature to 85-95℃ and continue stirring until the oil foot separates. Stop stirring 3-5 minutes later, let it cool to room temperature, and centrifuge for 20-25 minutes. Take the upper layer of hydrated oil to obtain hydrated degummed oil for later use. The mass fraction of diosgenin in the distilled water at the same temperature is 8-10%. Step 2, alkali refining and deacidification: Add alkali solution to the hydrated degummed oil obtained in Step 1, heat to 90-95℃ while stirring, maintain constant temperature and stir until the oil and soap are clearly separated, then stop stirring, centrifuge, take the upper layer of alkali-refined semi-clean oil, heat to 90-95℃, add distilled water and wash 2-3 times; heat the washed oil to dehydrate and dry, to obtain alkali-refined deacidified oil for later use. Step 3, adsorption and decolorization: The alkali-refined deacidified oil obtained in step 2 is heated to 90-95℃ under negative pressure and stirred to dehydrate. Then, the adsorbent is added and stirred evenly. The decolorization is carried out for 25-30 minutes. The oil and adsorbent mixture is centrifuged to separate the adsorbent, and the decolorized clean oil is obtained. Step 4, distillation and deodorization: Place the decolorized clean oil obtained in step 3 into a deodorization device, heat the oil to 250-260℃ under vacuum, introduce steam, deodorize for 2 hours, turn off the steam, and cool to room temperature to obtain deodorized oil. In step 3, the adsorbent is a modified chitosan-sodium alginate-clay composite adsorbent; the preparation method of the adsorbent is as follows: Step A: Crush scallop shells, sieve them to obtain scallop shell powder; soak the scallop shell powder in a 20-25% phosphoric acid solution for 6-8 hours; calcine the soaked scallop shell powder in an oxygen-free environment at 500-600℃ for 2-3 hours; cool the calcined product to room temperature, add distilled water and mix well; then add chitosan, heat to 50-60℃, stir until viscous under heat preservation, cool, dry, and crush to obtain product I; the amount of chitosan added is 5-6 times the mass of the scallop shell powder. Step B: Add distilled water at 40-50℃ to sodium alginate, stir until a viscous solution is formed under heat preservation, add calcium sulfite, mix well, dry, and pulverize to obtain product II; the mass ratio of sodium alginate to calcium sulfite is 1:(0.3-0.4). Step C: Mix the obtained product I, product II, and bleaching clay to obtain the composite adsorbent; the mass ratio of product I, product II, and bleaching clay is 1:(1-1.2):(2-3).

2. The method as described in claim 1, characterized in that, In step 3, the amount of adsorbent used is 3-5% of the mass of the alkali-refined deacidified oil.

3. The method as described in claim 1, characterized in that, In step A of the adsorbent preparation method, the mass-volume ratio of scallop shell powder to distilled water is 1:(8-10) in kg / L.

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