Method for reducing content of 3-chloropropanol ester and glycidyl ester in edible oil

Abstract

The invention relates to a method for reducing the content of 3-chloropropanol ester and glycidyl ester in edible oil, and belongs to the technical field of edible oil production. The method comprises the steps of hydration degumming, alkali refining deacidification, adsorption decoloration by using a composite adsorbent, distillation deodorization and the like. By means of the method, the increase of the content of 3-chloropropanol ester and glycidyl ester in the oil in the deodorization link can be obviously inhibited, the content of 3-chloropropanol ester and glycidyl ester in the obtained edible oil is low and is lower than the European standard, and the edible safety of the edible oil can be effectively guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of edible oil production and relates to a method for reducing the contents of 3-chloropropanol ester and glycidyl ester in edible oil. Background Art

[0002] Edible oil, also known as "cooking oil", refers to animal or plant fats used in the process of making food. It is liquid at room temperature. Due to the source of raw materials, processing technology and quality, most common edible oils are plant oils. Plant cooking oils are an important source of nutrition for the human body and are often eaten directly or used as raw materials for food processing. The quality and safety of edible oils have always been a hot issue in the food industry. 3-chloropropanol esters and glycidyl esters are hot issues of oil pollution that have received widespread attention in recent years. 3-chloropropanol esters and glycidyl esters are a type of hazardous components generated by glycerol esters in the process of oil processing with the participation of chlorine compounds, and are mainly generated under high temperature conditions during the oil processing process. According to domestic and foreign reports, 3-chloropropanol esters and glycidyl esters are widely present in oils and fats. In recent years, higher concentrations of 3-chloropropanol esters and glycidyl esters have been detected in oils and fats, indicating that the pollution problem is more prominent.

[0003] Literature reports show that the deodorization process of corn oil has a great influence on the content of 3-chloropropanol esters and glycidyl esters in the oil, and their content increases with the increase of deodorization temperature and deodorization time. In unrefined natural oils and crude oils, the content of 3-chloropropanol esters and glycidyl esters is low or undetectable, but the quality of raw materials affects the content of 3-chloropropanol esters and glycidyl esters in oils, and the formation of 3-chloropropanol esters and glycidyl esters in crude oil is related to the heat treatment conditions of the oil-making process and the oil refining process. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for reducing the content of 3-chloropropanol ester and glycidyl ester in edible oil. The method can significantly reduce the content of 3-chloropropanol ester and glycidyl ester in edible oil, and fully ensure the edible safety of edible oil.

[0005] The present invention adopts the following technical solutions to achieve the above purpose: A method for reducing the content of 3-chloropropanol ester and glycidyl ester in edible oil, specifically comprising the following steps: Step 1, hydration degumming, placing the crude edible oil in a stirrer and heating it to 25-30°C, adding distilled water containing diosgenin at the same temperature thereto under stirring, continuing stirring for 20-30 minutes, then heating to 85-95°C, continuing stirring until the oil foot is separated, stopping stirring for 3-5 minutes, standing and cooling to room temperature, centrifuging for 20-25 minutes, taking the upper hydrated oil, and obtaining the hydrated degummed oil for standby use; Step 2, alkali refining and deacidification, add alkali solution to the hydrated degummed oil obtained in step 1, heat it to 90-95°C under stirring, keep stirring at constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil, heat it to 90-95°C, add distilled water to wash 2-3 times; the washed oil is heated to dehydrate and dry to obtain alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating the alkali-refined deacidified oil obtained in step 2 to 90-95°C under negative pressure and stirring for dehydration, then adding the adsorbent, stirring evenly, decolorizing for 25-30 minutes, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining the decolorized clean oil; Step 4, distillation and deodorization, the decolorized clean oil obtained in step 3 is placed in a deodorization device, the oil is heated to 250-260°C under vacuum, steam is introduced, deodorization is performed for 2 hours, the steam is turned off, and the temperature is cooled to room temperature to obtain deodorized oil.

[0006] Furthermore, the mass fraction of dioscin in step 1 is 8-10%.

[0007] Furthermore, the amount of the adsorbent used in step 3 is 3-5% of the mass of the alkali-refined deacidified oil.

[0008] Furthermore, the adsorbent in step 3 is a modified chitosan-sodium alginate-white clay composite adsorbent.

[0009] Furthermore, the preparation method of the adsorbent in step 3 is: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking the scallop shell powder in a phosphoric acid solution with a mass fraction of 20-25% for 6-8 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 500-600° C. for 2-3 hours, cooling the calcined product to room temperature, adding distilled water to mix, then adding chitosan, heating to 50-60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, adding 40-50°C distilled water to sodium alginate, stirring under heat preservation until a viscous solution is obtained, adding calcium sulfite, mixing, drying, and crushing to obtain product II; Step C, mixing the obtained product I, product II and white clay to obtain a composite adsorbent.

[0010] Furthermore, in step A, the mass-volume ratio of scallop shell powder to distilled water is 1:(8-10) in kg / L.

[0011] Furthermore, the amount of chitosan added in step A is 5-6 times the mass of scallop shell powder.

[0012] Furthermore, in step B, the mass ratio of sodium alginate to calcium sulfite is 1:(0.3-0.4).

[0013] Furthermore, in step C, the mass ratio of product I, product II and white clay is 1:(1-1.2):(2-3).

[0014] The present invention has the following beneficial effects: The present invention optimizes the edible oil production and refining process, effectively reduces the content of 3-chloropropanol ester and glycidyl ester in oil, and ensures the safety of edible oil. The method provided by the present invention includes hydration degumming with purified water containing dioscin, followed by alkali refining and deacidification, adsorption decolorization using a specific composite adsorbent, and finally deodorization to obtain a finished edible oil product. The method of the present invention can significantly reduce 3-chloropropanol ester and glycidyl ester in the deodorization link, and the content of 3-chloropropanol ester and glycidyl ester is significantly lower than that of the traditional refining process. In the refining process, the inventor optimized the adsorbent, and did not use the traditional single clay adsorbent, but used a modified chitosan-sodium alginate-clay composite adsorbent. In the process of modifying chitosan, biochar prepared from shell powder was added, and calcium sulfite was added to sodium alginate, which increased the adsorption of the adsorbent, and at the same time, it can also increase the adsorption of chloride ions and reduce the chloride ion content in oils and fats, thereby avoiding the increase in the content of 3-chloropropanol esters caused by the presence of chloride ions during the deodorization process; in addition, in the hydration degumming link, dioscin was added to the purified water in the present invention, and dioscin can maintain the stability of oils and fats to a certain extent and reduce the generation of glycidyl esters. The various technical points in the present invention cooperate with each other to jointly suppress the content of 3-chloropropanol esters and glycidyl esters in oil production deodorization. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : Chloride ion content in the edible oil sample in each embodiment; Figure 2 : The content of 3-chloropropanol ester in the edible oil sample in each embodiment; Figure 3 : Glycidyl ester content of edible oil samples in each embodiment. DETAILED DESCRIPTION

[0016] The present invention is further explained below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications to the present invention by those skilled in the art all fall within the scope of protection of the claims of this application.

[0017] Example 1 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 25% by mass phosphoric acid solution for 6 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 600° C. for 2 hours, cooling the calcined product to room temperature, adding 10 L of distilled water and mixing, then adding 6 kg of chitosan, heating to 60° C., stirring under heat preservation until viscous state, cooling, drying, and crushing to obtain product I; Step B, add 50°C distilled water to 1 kg of sodium alginate, stir under heat preservation until a viscous solution is obtained, add 0.3 kg of calcium sulfite, mix well, dry, and crush to obtain product II; Step C, mixing 1 kg of product I, 1 kg of product II and 2 kg of white clay to obtain a composite adsorbent.

[0018] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is determined to be 2.108mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 3.162g of distilled water at the same temperature containing diosgenin (mass fraction of 10%) under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated, stop stirring 3min, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the acid value of crude oil (the acid value of crude corn oil is 4.635 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (72.32 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring and raise the temperature to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass to wash twice; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 5% of the oil mass of the obtained composite adsorbent, stirring evenly, decolorizing for 25min, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0019] Example 2 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 20% by mass phosphoric acid solution for 8 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 500° C. for 3 hours, cooling the calcined product to room temperature, adding 8 L of distilled water to mix, then adding 5 kg of chitosan, heating to 50° C., stirring under heat preservation until viscous state, cooling, drying, and crushing to obtain product I; Step B, add 40°C distilled water to 1 kg of sodium alginate, stir under heat preservation until a viscous solution is obtained, add 0.4 kg of calcium sulfite, mix well, dry, and crush to obtain product II; Step C, mixing 1 kg of product I, 1.2 kg of product II, and 3 kg of white clay to obtain a composite adsorbent.

[0020] Edible Oil Refining: Step 1, hydration degumming, take 500g of peanut crude oil (the phospholipid content is determined to be 2.638mg / g), place it in a heating magnetic stirrer and heat it to 25°C, add 3.957g of distilled water at the same temperature containing diosgenin (mass fraction is 8%) under stirring, continue stirring for 30min, then heat it to 85°C, continue stirring until the oil foot is separated, stop stirring 5min, let it stand and cool to room temperature, centrifuge it for 20min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of crude peanut oil is 4.319 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (67.39 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring and raise the temperature to 90°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 90°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 90°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 3% of the oil mass of the obtained composite adsorbent, stirring evenly, decolorizing for 30min, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 250°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0021] Example 3 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 20% by mass phosphoric acid solution for 7 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 600° C. for 2 hours, cooling the calcined product to room temperature, adding 9 L of distilled water and mixing, then adding 5.5 kg of chitosan, heating to 60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, add 50°C distilled water to 1 kg of sodium alginate, stir under heat preservation until a viscous solution is obtained, add 0.35 kg of calcium sulfite, mix well, dry, and crush to obtain product II; Step C, mixing 1 kg of product I, 1.1 kg of product II, and 2.5 kg of white clay to obtain a composite adsorbent.

[0022] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction is 9%) under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated, stop stirring 4min, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass of the obtained composite adsorbent, stirring evenly, decolorizing for 30min, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0023] Comparative Example 1 Preparation of composite adsorbent: Step A, add 50°C distilled water to 1 kg of sodium alginate, stir under heat preservation until a viscous solution is obtained, add 0.35 kg of calcium sulfite, mix well, dry, and crush to obtain product I; Step B, mixing 1 kg of product I and 1.25 kg of white clay to obtain a composite adsorbent.

[0024] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction is 9%) under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated, stop stirring 4min, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass of the obtained composite adsorbent, stirring evenly, decolorizing for 30min, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0025] Comparative Example 2 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 20% by mass phosphoric acid solution for 7 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 600° C. for 2 hours, cooling the calcined product to room temperature, adding 9 L of distilled water and mixing, then adding 5.5 kg of chitosan, heating to 60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, mixing 1 kg of product I and 1.25 kg of white clay to obtain a composite adsorbent.

[0026] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction is 9%) under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated, stop stirring 4min, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass of the obtained composite adsorbent, stirring evenly, decolorizing for 30min, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0027] Comparative Example 3 Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature containing diosgenin (mass fraction is 9%) under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated, stop stirring 4min, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass of white clay, stirring evenly, decolorizing for 30 minutes, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0028] Comparative Example 4 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 20% by mass phosphoric acid solution for 7 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 600° C. for 2 hours, cooling the calcined product to room temperature, adding 9 L of distilled water and mixing, then adding 5.5 kg of chitosan, heating to 60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, add 50°C distilled water to 1 kg of sodium alginate, stir under heat preservation until a viscous solution is obtained, add 0.35 kg of calcium sulfite, mix well, dry, and crush to obtain product II; Step C, mixing 1 kg of product I, 1.1 kg of product II, and 2.5 kg of white clay to obtain a composite adsorbent.

[0029] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature thereto under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated 4min later, stop stirring, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass to obtain the above-obtained composite adsorbent, stirring evenly, decolorizing for 30 minutes, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0030] Comparative Example 5 Preparation of composite adsorbent: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking 1 kg of scallop shell powder in a 20% by mass phosphoric acid solution for 7 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 600° C. for 2 hours, cooling the calcined product to room temperature, adding 9 L of distilled water and mixing, then adding 2 kg of chitosan and 2.5 kg of sodium alginate, heating to 60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, mixing 1 kg of product I and 1.25 kg of white clay to obtain a composite adsorbent.

[0031] Edible Oil Refining: Step 1, hydration degumming, take 500g corn crude oil (the phospholipid content is measured to be 3.027mg / g), place it in a heating magnetic stirrer and heat it to 30°C, add 4.54g of distilled water at the same temperature thereto under stirring, continue stirring for 20min, then heat it to 95°C, continue stirring until the oil foot is separated 4min later, stop stirring, let it stand and cool to room temperature, centrifuge it for 25min, take the upper hydrated oil, and obtain hydrated degummed oil; Step 2, alkali refining and deacidification, the sum of the theoretical alkali amount calculated based on the crude oil acid value (the acid value of corn crude oil is 4.062 mg / g in terms of KOH) and the excess alkali amount of 0.2% of the oil mass (63.37 mL) is used as the alkali amount for alkali refining and deacidification. The mass fraction of the alkali solution used is 6.58%. Weigh 300g of the hydrated degummed oil obtained above, add alkali solution while stirring, and heat to 95°C. Keep stirring at a constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil and heat it to 95°C. Add distilled water at 15% of the oil mass each time to wash it 3 times; the washed oil is heated to dehydrate and dried to obtain the alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating 200g of alkali-refined deacidified oil to 95°C under negative pressure and stirring to dehydrate until no mist is seen on the oil surface, then weighing 4% of the oil mass to obtain the above-obtained composite adsorbent, stirring evenly, decolorizing for 30 minutes, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining decolorized clean oil; Step 4, distillation and deodorization, place 100g of the decolorized clean oil obtained above in a deodorization device, start the vacuum pump, slowly heat the oil to 260°C when the system pressure is below 400Pa, introduce steam, maximize the ventilation volume and keep the flow rate constant without causing oil splashing, deodorize for 2h, turn off the steam, and cool the oil to room temperature to obtain deodorized oil.

[0032] Performance Testing The contents of chloride ions, 3-chloropropanediol esters (3-MCPD esters) and glycidyl esters (GEs) in the oil samples of each step of the method described in Examples 1-3 and Comparative Examples 1-5 were determined by conventional detection methods. The results are shown in the attached Figure 1-3 .

[0033] Existing literature has disclosed that the chloride ion content in edible oil will affect the content of 3-MCPD esters. In the traditional refining process, the process before the deodorization stage has little effect on the formation of 3-MCPD esters. Chloride ions will be removed with the separation of oil feet, soap feet, and waste clay. The deodorization process is the main stage for the formation of 3-MCPD esters. Chloride ions are reduced in this stage, but the content of 3-MCPD esters will increase significantly. The reduction of chloride ion content in the deodorization stage contributes to the formation of 3-MCPD esters. In addition, the content of glycidyl esters in the traditional process will also increase significantly after the deodorization stage.

[0034] Self-attached Figure 1 It can be seen from the figure that the chloride ion content in peanut oil or corn oil will gradually decrease during the refining process, and the chloride ion content changes in each embodiment are not much different. Figure 2 It can be seen from the results that the corn oil in Comparative Example 5 is a traditional refining process. After the deodorization step, the content of 3-MCPD ester increases significantly. Compared with before deodorization, the content of 3-MCPD ester increases to 3.72 mg / kg, an increase of 1282.76%, which is consistent with the content disclosed in the literature. However, in the oil samples after deodorization in Examples 1-3, the increase in 3-MCPD ester content is small, and the increase is less than 0.5 mg / kg. The methods in Comparative Examples 1-4 are different from those in the present invention (such as the adsorbent preparation method, component addition, etc.). The content of 3-MCPD ester in the oil samples after the deodorization step increases significantly, but compared with the increase in Comparative Example 5, the increase is small.

[0035] Self-attached Figure 3 It can be seen that the glycidyl ester content shows a downward trend in the refining stage before deodorization, and there is basically no big difference between the various embodiments, but 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 glycidyl ester content in the samples of Examples 1-3 after deodorization does not increase significantly, and the increase is less than 1 mg / kg. The glycidyl ester content in Comparative Examples 1-4 increases by more than 1 mg / kg, but the increase is smaller than that in Comparative Example 5.

[0036] It can be seen that the method provided by the present invention can effectively reduce the content of 3-chloropropanol ester and glycidyl ester in edible oil, and ensure the edible safety of edible oil.

Claims

1. A method for reducing the content of 3-chloropropanol ester and glycidyl ester in edible oil, characterized in that: The following steps are involved: Step 1, hydration degumming, placing the crude edible oil in a stirrer and heating it to 25-30°C, adding distilled water containing diosgenin at the same temperature thereto under stirring, continuing stirring for 20-30 minutes, then heating to 85-95°C, continuing stirring until the oil foot is separated, stopping stirring for 3-5 minutes, standing and cooling to room temperature, centrifuging for 20-25 minutes, taking the upper hydrated oil, and obtaining the hydrated degummed oil for standby use; Step 2, alkali refining and deacidification, add alkali solution to the hydrated degummed oil obtained in step 1, heat it to 90-95°C under stirring, keep stirring at constant temperature until the oil and soap are obviously separated, stop stirring, centrifuge, take the upper alkali-refined semi-clean oil, heat it to 90-95°C, add distilled water to wash 2-3 times; the washed oil is heated to dehydrate and dry to obtain alkali-refined deacidified oil for use; Step 3, adsorption decolorization, heating the alkali-refined deacidified oil obtained in step 2 to 90-95°C under negative pressure and stirring for dehydration, then adding the adsorbent, stirring evenly, decolorizing for 25-30 minutes, centrifuging the oil and adsorbent mixture, separating the adsorbent, and obtaining the decolorized clean oil; Step 4, distillation and deodorization, the decolorized clean oil obtained in step 3 is placed in a deodorization device, the oil is heated to 250-260°C under vacuum, steam is introduced, deodorization is performed for 2 hours, the steam is turned off, and the temperature is cooled to room temperature to obtain deodorized oil.

2. The method according to claim 1, characterized in that The mass fraction of dioscin in step 1 is 8-10%.

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

4. The method according to claim 1, characterized in that The adsorbent in step 3 is a modified chitosan-sodium alginate-white clay composite adsorbent.

5. The method according to claim 4, characterized in that The preparation method of the adsorbent in step 3 is: Step A, crushing and sieving scallop shells to obtain scallop shell powder; soaking the scallop shell powder in a phosphoric acid solution with a mass fraction of 20-25% for 6-8 hours, calcining the soaked scallop shell powder in an oxygen-free environment at 500-600° C. for 2-3 hours, cooling the calcined product to room temperature, adding distilled water to mix, then adding chitosan, heating to 50-60° C., stirring in a heat preservation state until it becomes viscous, cooling, drying, and crushing to obtain product I; Step B, adding 40-50°C distilled water to sodium alginate, stirring under heat preservation until a viscous solution is obtained, adding calcium sulfite, mixing, drying, and crushing to obtain product II; Step C, mixing the obtained product I, product II and white clay to obtain a composite adsorbent.

6. The method according to claim 5, characterized in that The mass-volume ratio of scallop shell powder to distilled water in step A is 1:(8-10) in kg / L.

7. The method according to claim 5, characterized in that The amount of chitosan added in step A is 5-6 times the mass of the scallop shell powder.

8. The method according to claim 5, characterized in that The mass ratio of sodium alginate to calcium sulfite in step B is 1:(0.3-0.4).

9. The method according to claim 5, characterized in that In the step C, the mass ratio of product I, product II and white clay is 1:(1-1.2):(2-3).

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