Refining process of flaxseed oil with low glycidyl ester and low trichloropropanol ester

Abstract

The invention belongs to the field of flaxseed oil refining, and particularly discloses a low-glycidyl ester and low-trichloropropanol ester flaxseed oil refining process which comprises the steps of cleaning and impurity removal, cleaning and drying, shelling and color sorting, low-temperature pretreatment, cold-pressing oil extraction, degumming and deacidification refining, water washing and dehydration, decoloration, deodorization and the like. The microwave drying adopts segmented temperature control, cold-pressing oil extraction adopts a hydraulic cold pressing machine and centrifugal impurity removal, degumming and deacidification refining remove impurities by controlling the temperature, the water adding amount and the stirring speed, and water washing and dehydration pay attention to oil-water separation and low-temperature vacuum dehydration. Carclazyte or activated carbon is adopted for decoloration for adsorption, and steam distillation is carried out at low temperature and an antioxidant limonin aqueous solution is added for deodorization; the whole process aims at reducing the content of glycidyl ester and trichloropropanol ester and improving the quality of the linseed oil, further, the low-temperature pretreatment step is added, the content of glycidyl ester and trichloropropanol ester can be greatly reduced, and the step is simple and low in cost.

Description

Technical Field

[0001] The invention belongs to the field of linseed oil refining, and specifically discloses a refining process of low-glycidyl ester and low-trichloropropanol ester linseed oil. Background Art

[0002] In the food industry, flaxseed oil is highly favored because it is rich in α-linolenic acid (Omega-3) and a variety of nutrients beneficial to the human body, such as lignans and fiber. However, while traditional flaxseed oil refining processes pursue high yield and color stability, it is often difficult to effectively control harmful substances produced during the refining process, such as glycidyl esters (GE) and trichloropropane esters (3-MCPDE). These compounds may be generated during the high temperature, chemical treatment and enzymatic hydrolysis of oil refining, and pose potential risks to human health, such as affecting liver function and increasing the risk of cancer.

[0003] At present, the common linseed oil refining processes on the market mostly use high temperature refining, chemical deacidification and alkali refining methods. Although these methods can effectively remove impurities and free fatty acids in oils and fats, they can also lead to the increase of harmful substances such as GE and 3-MCPDE. In addition, the solvents and chemicals used in traditional processes may also remain in the oils and fats, further affecting the safety and quality of the products. Therefore, developing a refining process that can significantly reduce the content of GE and 3-MCPDE in linseed oil while retaining its nutritional components and good flavor has become one of the hot spots in the current food industry research. Summary of the invention

[0004] In order to solve the above problems, the present invention discloses a refining process of low-glycidyl ester and low-trichloropropanol ester linseed oil, aiming to effectively reduce the generation of GE and 3-MCPDE by optimizing various links in the refining process, such as low-temperature pretreatment, cold pressing oil extraction, physical degumming and deacidification, and low-temperature deodorization, while maintaining the nutritional components and flavor of linseed oil, so as to provide consumers with safer and healthier edible oils and fats.

[0005] The technical solution of the present invention is as follows:

[0006] A refining process of low glycidyl ester and low trichloropropanol ester linseed oil comprises the following steps:

[0007] 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers;

[0008] 2) Cleaning: Clean the flax seeds in shells;

[0009] 3) Microwave drying: using segmented microwave drying to make the shelled flax seeds in a suitable state for shelling;

[0010] 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels;

[0011] 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials;

[0012] 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 4-10° C. and humidity below 20% for 15-25 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE;

[0013] 7) Cold pressing oil: cold pressing is used to extract crude oil;

[0014] 8) Degumming and refining: Use hydration degumming method to remove phospholipid impurities while controlling temperature and stirring speed;

[0015] 9) Deacidification and refining: Use food-grade alkali solution to neutralize free fatty acids, control the alkali addition rate and stirring time, and avoid excessive reaction to produce by-products;

[0016] 10) Washing with water: add appropriate soft water at the operating temperature, control the amount of water added and the stirring speed to ensure effective washing without excessive emulsification;

[0017] 11) Dehydration: Use vacuum drying technology to remove moisture from oil at a lower temperature to prevent oxidation and pyrolysis caused by high temperature;

[0018] 12) Decolorization: Use white clay or activated carbon adsorbent to remove pigments and other oxides in the oil;

[0019] 13) Deodorization: Deodorization is performed at low temperature to reduce the formation of GE; at the same time, a proper amount of antioxidant limonin aqueous solution is added to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0020] Furthermore, in the above-mentioned refining process of low glycidyl ester and low trichloropropane ester linseed oil, in the step 3) microwave drying, the microwave drying comprises the following steps:

[0021] Set the microwave frequency to 2450±50MHz:

[0022] Stage 1: Control the microwave power to keep the temperature at 45-55°C for 5 minutes;

[0023] The second stage: control the microwave power to keep the temperature at 55-65°C for 3 minutes;

[0024] The third stage: Control the microwave power to keep the temperature at 80-90℃ for 2 minutes.

[0025] The above three stages are repeated until the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12% and the drying is completed.

[0026] Furthermore, in the refining process of the above-mentioned low-glycidyl ester and low-trichloropropanol ester linseed oil, the step 7) cold-pressing the oil comprises the following steps: using a hydraulic cold press, setting the pressure to 25-35 MPa, and pressing at room temperature to obtain linseed crude oil; centrifuging the obtained linseed crude oil at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant as the cold-pressed linseed crude oil.

[0027] Furthermore, in the above-mentioned refining process of low glycidyl ester and low trichloropropane ester linseed oil, the step 8) degumming and refining comprises the following steps:

[0028] Heat the crude oil to the hydration operating temperature of 80-85°C, slowly add 0.02-0.05 times the volume of the crude oil and 90-95°C water, add for 5-10 minutes, stir at 30-60rpm, after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge 5000-8000g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C.

[0029] Furthermore, in the above-mentioned refining process of low-glycidyl ester and low-trichloropropane ester linseed oil, the step 9) deacidification refining comprises the following steps: heating the crude oil to 70-80°C, determining the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, adding slowly and stirring evenly at a stirring speed of 60-100rpm, stirring and reacting for 20-40min until the emulsion and soap particles are obviously separated from the oil; standing and settling for 4-6h; separating the settled mixture using a centrifuge of 10000-15000g to remove phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C.

[0030] Furthermore, in the above-mentioned refining process of low-glycidyl ester and low-trichloropropane ester linseed oil, the step 10) water washing comprises the following steps: heating the oil temperature to 75-85°C, adding 0.05-0.1 times the volume of the oil volume of soft water at the same temperature, stirring and mixing at a speed of 10-20 rpm for 10-20 minutes, and then standing for 1-2 hours to separate the oil and water layers, and taking the oil layer for subsequent treatment.

[0031] Furthermore, in the above-mentioned refining process of low glycidyl ester and low trichloropropane ester linseed oil, the step 11) dehydration comprises the following steps: heating the oil temperature to 95-100° C., maintaining the vacuum degree not less than 700 mmHg, stirring at 30-40 rpm, and reducing the water content to below 3%.

[0032] Furthermore, in the above-mentioned refining process of low glycidyl ester and low trichloropropane ester linseed oil, the decolorization in step 12) comprises the following steps:

[0033] S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, the heating system is started to gradually increase the oil temperature to between 90 and 105°C.

[0034] To promote full contact and mixing between the adsorbent and the grease;

[0035] S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank;

[0036] S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil;

[0037] S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

[0038] Furthermore, in the above-mentioned refining process of low glycidyl ester and low trichloropropane ester linseed oil, the deodorization step 13) comprises the following steps:

[0039] I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment;

[0040] II. Steam distillation: under the above vacuum and temperature conditions, the volatile substances and bad odors in the oil are removed by steam distillation;

[0041] III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.05-0.1 times the volume;

[0042] IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The invention discloses a refining process of low-glycidyl ester and low-trichloropropane ester linseed oil. Through low-temperature pretreatment, cold-pressing oil extraction and low-temperature deodorization, the generation of harmful substances such as glycidyl ester (GE) and trichloropropane ester (3-MCPDE) in the refining process is effectively reduced, and the safety of the product is improved; the cold-pressing method is used to extract the oil, which avoids the damage of high temperature to the nutrients in the linseed oil, such as α-linolenic acid, lignans, etc., and retains the natural flavor and nutritional value of the oil; microwave drying adopts segmented temperature control, which can more efficiently remove the moisture inside the linseed shell, while saving energy and time. In addition, the vacuum drying technology also reduces the energy consumption in the dehydration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The present invention discloses a refining process flow chart of low-glycidyl ester and low-trichloropropanol ester linseed oil;

[0046] Figure 2 Comparison of shelling rates in Test Example 1;

[0047] Figure 3 is a comparison of the content of glycidyl ester (GE) μg / kg in Test Example 2;

[0048] Figure 4 This is a comparison of the content of trichloropropane ester (3-MCPDE) mg / kg in Test Example 2. DETAILED DESCRIPTION

[0049] like Figure 1 A refining process of low glycidyl ester and low trichloropropanol ester linseed oil shown comprises the following steps:

[0050] 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers;

[0051] 2) Cleaning: Clean the flax seeds in shells;

[0052] 3) Microwave drying: using segmented microwave drying, comprising the following steps:

[0053] Set the microwave frequency to 2450±50MHz:

[0054] Stage 1: Control the microwave power to keep the temperature at 45-55°C for 5 minutes;

[0055] The second stage: control the microwave power to keep the temperature at 55-65°C for 3 minutes;

[0056] The third stage: Control the microwave power to keep the temperature at 80-90℃ for 2 minutes.

[0057] After the above three stages are repeated, the drying is completed when the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12%, so that the flaxseed with shell is in a suitable state for shelling;

[0058] 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels;

[0059] 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials;

[0060] 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 4-10° C. and humidity below 20% for 15-25 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE;

[0061] 7) Cold pressing oil: using a hydraulic cold press, setting the pressure at 25-35 MPa, and pressing at room temperature to obtain flaxseed crude oil; centrifuging the flaxseed crude oil obtained above at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant as the cold pressed flaxseed crude oil;

[0062] 8) Degumming and refining: heat the crude oil to a hydration operating temperature of 80-85°C, slowly add 0.02-0.05 times the volume of the crude oil and 90-95°C water, add for 5-10 minutes, stir at 30-60rpm, and after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge at 5000-8000g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0063] 9) Deacidification and refining; heat the crude oil to 70-80°C, determine the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, add slowly and stir evenly at a stirring speed of 60-100rpm, stir and react for 20-40min until the emulsion and soap particles are obviously separated from the oil; let it stand for 4-6h; use a centrifuge of 10000-15000g to separate the settled mixture to remove phospholipid impurities,

[0064] The separation temperature of the centrifuge is 70-80°C;

[0065] 10) Washing with water; heat the oil to 75-85°C, add 0.05-0.1 times the volume of the oil in soft water at the same temperature, stir and mix at a speed of 10-20 rpm for 10-20 min, then let stand for 1-2 hours to allow the oil and water to separate, and take the oil layer for subsequent treatment;

[0066] 11) Dehydration: Heat the oil temperature to 95-100°C, maintain a vacuum of not less than 700 mmHg, stir at 30-40 rpm, and reduce the water content to below 3%;

[0067] 12) Decolorization:

[0068] S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, start the heating system to gradually increase the oil temperature to between 90 and 105°C to promote full contact and mixing between the adsorbent and the oil;

[0069] S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank;

[0070] S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil;

[0071] S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

[0072] 13) Deodorization:

[0073] I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment;

[0074] II. Steam distillation: Under the above vacuum and temperature conditions, volatile substances and bad odors in oils and fats are removed by steam distillation;

[0075] III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.05-0.1 times the volume;

[0076] IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0077] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] Example 1

[0079] A refining process of low glycidyl ester and low trichloropropanol ester linseed oil comprises the following steps:

[0080] 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers;

[0081] 2) Cleaning: Clean the flax seeds in shells;

[0082] 3) Microwave drying: using segmented microwave drying, comprising the following steps:

[0083] Set the microwave frequency to 2450±50MHz:

[0084] The first stage: control the microwave power to keep the temperature at 45°C for 5 minutes;

[0085] The second stage: control the microwave power to keep the temperature at 55°C for 3 minutes;

[0086] The third stage: control the microwave power to keep the temperature at 80°C for 2 minutes.

[0087] After the above three stages are repeated, the drying is completed when the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12%, so that the flaxseed with shell is in a suitable state for shelling;

[0088] 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels;

[0089] 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials;

[0090] 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 4° C. and humidity below 20% for 25 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE;

[0091] 7) Cold pressing oil: using a hydraulic cold press, setting the pressure at 25-35 MPa, and pressing at room temperature to obtain flaxseed crude oil; centrifuging the flaxseed crude oil obtained above at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant as the cold pressed flaxseed crude oil;

[0092] 8) Degumming and refining: heat the crude oil to a hydration operating temperature of 80-85°C, slowly add 0.02 times the volume of the crude oil at 90-95°C water, add for 5-10 minutes, stir at 30-60rpm, and after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge at 5000g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0093] 9) Deacidification and refining; heating the crude oil to 70-80°C, determining the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, adding slowly and stirring evenly at a stirring speed of 60-100 rpm, stirring and reacting for 20-40 minutes, until the emulsion and soap particles are obviously separated from the oil; standing and settling for 4-6 hours; separating the settled mixture using a centrifuge of 10000g to remove phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0094] 10) Washing with water; heat the oil to 75-85°C, add 0.05 times the volume of the oil in soft water at the same temperature, stir and mix at a speed of 10-20 rpm for 10-20 min, then let stand for 1-2 hours to allow the oil and water to separate, and take the oil layer for subsequent treatment;

[0095] 11) Dehydration: Heat the oil temperature to 95-100°C, maintain a vacuum of not less than 700 mmHg, stir at 30-40 rpm, and reduce the water content to below 3%;

[0096] 12) Decolorization:

[0097] S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, start the heating system to gradually increase the oil temperature to between 90 and 105°C to promote full contact and mixing between the adsorbent and the oil;

[0098] S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank;

[0099] S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil;

[0100] S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

[0101] 13) Deodorization:

[0102] I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment;

[0103] II. Steam distillation: under the above vacuum and temperature conditions, the volatile substances and bad odors in the oil are removed by steam distillation;

[0104] III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.05 times the volume;

[0105] IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0106] Example 2

[0107] A refining process of low glycidyl ester and low trichloropropanol ester linseed oil comprises the following steps:

[0108] 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers;

[0109] 2) Cleaning: Clean the flax seeds in shells;

[0110] 3) Microwave drying: using segmented microwave drying, comprising the following steps:

[0111] Set the microwave frequency to 2450±50MHz:

[0112] The first stage: control the microwave power to keep the temperature at 50°C for 5 minutes;

[0113] The second stage: control the microwave power to keep the temperature at 60°C for 3 minutes;

[0114] The third stage: control the microwave power to keep the temperature at 85°C for 2 minutes.

[0115] After the above three stages are repeated, the drying is completed when the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12%, so that the flaxseed with shell is in a suitable state for shelling;

[0116] 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels;

[0117] 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials;

[0118] 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 8° C. and humidity below 20% for 20 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE;

[0119] 7) Cold pressing oil: using a hydraulic cold press, setting the pressure at 25-35 MPa, and pressing at room temperature to obtain flaxseed crude oil; centrifuging the flaxseed crude oil obtained above at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant as the cold pressed flaxseed crude oil;

[0120] 8) Degumming and refining: heat the crude oil to a hydration operating temperature of 80-85°C, slowly add 0.04 times the volume of the crude oil with a temperature of 90-95°C, add for 5-10 minutes, stir at 30-60 rpm, and after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge at 6500g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0121] 9) Deacidification and refining; heating the crude oil to 70-80°C, determining the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, adding slowly and stirring evenly at a stirring speed of 60-100 rpm, stirring and reacting for 20-40 minutes, until the emulsion and soap particles are obviously separated from the oil; standing and settling for 4-6 hours; separating the settled mixture using a centrifuge at 12000g to remove phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0122] 10) Washing with water; heat the oil to 75-85°C, add 0.08 times the volume of the oil in soft water at the same temperature, stir and mix at a speed of 10-20 rpm for 10-20 min, then let stand for 1-2 h to separate the oil and water, and take the oil layer for subsequent treatment;

[0123] 11) Dehydration: Heat the oil temperature to 95-100°C, maintain a vacuum of not less than 700 mmHg, stir at 30-40 rpm, and reduce the water content to below 3%;

[0124] 12) Decolorization:

[0125] S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, start the heating system to gradually increase the oil temperature to between 90 and 105°C to promote full contact and mixing between the adsorbent and the oil;

[0126] S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank;

[0127] S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil;

[0128] S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

[0129] 13) Deodorization:

[0130] I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment;

[0131] II. Steam distillation: Under the above vacuum and temperature conditions, volatile substances and bad odors in oils and fats are removed by steam distillation;

[0132] III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.08 times the volume;

[0133] IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0134] Example 3

[0135] A refining process of low glycidyl ester and low trichloropropanol ester linseed oil comprises the following steps:

[0136] 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers;

[0137] 2) Cleaning: Clean the flax seeds in shells;

[0138] 3) Microwave drying: using segmented microwave drying, comprising the following steps:

[0139] Set the microwave frequency to 2450±50MHz:

[0140] Stage 1: Control the microwave power to keep the temperature at 55°C for 5 minutes;

[0141] The second stage: control the microwave power to keep the temperature at 65°C for 3 minutes;

[0142] The third stage: control the microwave power to keep the temperature at 90°C for 2 minutes.

[0143] After the above three stages are repeated, the drying is completed when the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12%, so that the flaxseed with shell is in a suitable state for shelling;

[0144] 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels;

[0145] 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials;

[0146] 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 10° C. and humidity below 20% for 15 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE;

[0147] 7) Cold pressing oil: using a hydraulic cold press, setting the pressure at 25-35 MPa, and pressing at room temperature to obtain flaxseed crude oil; centrifuging the flaxseed crude oil obtained above at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant as the cold pressed flaxseed crude oil;

[0148] 8) Degumming and refining: heat the crude oil to a hydration operating temperature of 80-85°C, slowly add 0.05 times the volume of the crude oil with a temperature of 90-95°C, add for 5-10 minutes, stir at 30-60 rpm, and after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge at 8000g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0149] 9) Deacidification and refining; heating the crude oil to 70-80°C, determining the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, adding slowly and stirring evenly at a stirring speed of 60-100 rpm, stirring and reacting for 20-40 minutes, until the emulsion and soap particles are obviously separated from the oil; standing and settling for 4-6 hours; separating the settled mixture using a centrifuge of 15000g to remove phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C;

[0150] 10) Washing with water; heat the oil to 75-85°C, add 0.05-0.1 times the volume of the oil in soft water at the same temperature, stir and mix at a speed of 10-20 rpm for 10-20 min, then let stand for 1-2 hours to allow the oil and water to separate, and take the oil layer for subsequent treatment;

[0151] 11) Dehydration: Heat the oil temperature to 95-100°C, maintain a vacuum of not less than 700 mmHg, stir at 30-40 rpm, and reduce the water content to below 3%;

[0152] 12) Decolorization:

[0153] S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, start the heating system to gradually increase the oil temperature to between 90 and 105°C to promote full contact and mixing between the adsorbent and the oil;

[0154] S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank;

[0155] S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil;

[0156] S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

[0157] 13) Deodorization:

[0158] I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment;

[0159] II. Steam distillation: Under the above vacuum and temperature conditions, volatile substances and bad odors in oils and fats are removed by steam distillation;

[0160] III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.1 times the volume;

[0161] IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

[0162] Comparative Example 1

[0163] This comparative example does not contain 3) microwave drying, but ordinary drying, and the rest is the same as Example 2.

[0164] Comparative Example 2

[0165] This comparative example does not contain 6) low temperature pretreatment, and the rest is the same as Example 2.

[0166] Test Example 1

[0167] The flaxseed dehulling rates of step (4) of comparative example 1 and examples 1-3 were compared.

[0168] The shelling rate refers to the percentage of the shell part successfully separated from the flax seeds after the shelling process to the total mass of the original flax seeds, that is, shelling rate = (mass of the shell / total mass of the original flax seeds) × 100%.

[0169] The results are shown in Table 1 and Figure 2 .

[0170] Flaxseed hulling rate (%) Example 1 64.2 Example 2 65.1 Example 3 64.6 Comparative Example 1 54.7

[0171] From the data in Table 1, it can be seen that the use of segmented microwave drying can greatly increase the shelling rate of flax seeds, improve the purity of subsequent flax seed oil extraction, and reduce the impurity treatment process.

[0172] Test Example 2

[0173] Comparing the glycidyl ester (GE) and trichloropropane ester (3-MCPDE) in the commercially available cooked linseed oil and the linseed oil finally obtained in Example 2 and Comparative Examples 1-2, the detection method is a mature method in the prior art.

[0174] Detection of glycidyl ester (GE): First, glycidyl ester is derivatized with N'N-diethyldithiocarbamate, and then the content of the derivatized product is determined by ultraviolet spectrophotometry or liquid chromatography ultraviolet detector. (EU standard limit 1000μg / kg).

[0175] The content of 3-MCPDE is directly detected by liquid chromatography-mass spectrometry (LC-MS) without destroying its molecular structure (the recommended limit value of 3-MCPDE by the American Oil and Fats Association is 2 mg / kg).

[0176] The results are shown in Table 2 and Figure 3 and Figure 4 shown.

[0177]

[0178] From the data in Table 2 above, it can be seen that the refining process of the present invention can reduce the glycidyl ester in linseed oil to 250 μg / kg, which is one-fourth of the EU standard and much lower than the content in commercial cold-pressed linseed oil. From the comparison between Comparative Example 2 and Example 2, since Example 2 uses 6) low-temperature pretreatment, the glycidyl ester (GE) content is only one-third of that in Comparative Example 2, indicating that the GE content can be effectively reduced by using only the above simple low-temperature pretreatment. From the perspective of the content of trichloropropane ester, it is also very similar to the situation of GE. The above treatment cost is low, the equipment requirements are low, and it is suitable for industrial promotion and application.

[0179] It can be seen from the above examples that the use of low-temperature pretreatment, cold-pressing oil extraction, physical degumming and deacidification, and low-temperature deodorization can effectively reduce the generation of GE and 3-MCPDE, while maintaining the nutritional components and flavor of flaxseed oil, providing consumers with safer and healthier edible oils.

[0180] The above are limited to several preferred embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A refining process for low glycidyl ester and low trichloropropane ester linseed oil, characterized in that: The following steps are involved: 1) Cleaning and removing impurities: Clean the harvested shelled flax seeds and remove stones, soil, plant stems and leaves through vibrating screens and stone removers; 2) Cleaning: Clean the flax seeds in shells; 3) Microwave drying: using segmented microwave drying to make the shelled flax seeds in a suitable state for shelling; 4) Shelling: Shelling the flax seeds with shells to obtain flax seed kernels; 5) Color sorting: Use a color sorter to screen out impurities and defective products in flax seed kernels to obtain flax seed kernel raw materials; 6) Low temperature pretreatment: The obtained flax seed kernel raw material is stored in an environment of 4-10° C. and humidity below 20% for 15-25 days for low temperature pretreatment to reduce the content of glycidyl ester GE and trichloropropanol ester 3-MCPDE; 7) Cold pressing oil: cold pressing is used to extract crude oil; 8) Degumming and refining: Use hydration degumming method to remove phospholipid impurities while controlling temperature and stirring speed; 9) Deacidification and refining: Use food-grade alkali solution to neutralize free fatty acids, control the alkali addition rate and stirring time, and avoid excessive reaction to produce by-products; 10) Washing with water: add appropriate soft water at the operating temperature, control the amount of water added and the stirring speed to ensure effective washing without excessive emulsification; 11) Dehydration: Use vacuum drying technology to remove moisture from oil at a lower temperature to prevent oxidation and pyrolysis caused by high temperature; 12) Decolorization: Use white clay or activated carbon adsorbent to remove pigments and other oxides in the oil; 13) Deodorization: Deodorization is performed at low temperature to reduce the formation of GE; at the same time, a proper amount of antioxidant limonin aqueous solution is added to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

2. A refining process for low glycidyl ester and low trichloropropane ester linseed oil according to claim 1, characterized in that: In the step 3) microwave drying, the microwave drying comprises the following steps: Set the microwave frequency to 2450±50MHz: Stage 1: Control the microwave power to keep the temperature at 45-55°C for 5 minutes; The second stage: control the microwave power to keep the temperature at 55-65°C for 3 minutes; The third stage: Control the microwave power to keep the temperature at 80-90℃ for 2 minutes. The above three stages are repeated until the moisture content of the flaxseed kernel inside the flaxseed shell is reduced to 8-12% and the drying is completed.

3. A refining process for low glycidyl ester and low trichloropropane ester linseed oil according to claim 1, characterized in that: The step 7) cold pressing the oil comprises the following steps: using a hydraulic cold press machine, setting the pressure to 25-35 MPa, pressing at room temperature to obtain flaxseed crude oil; centrifuging the obtained flaxseed crude oil at 6000-6500 r / min for 10-15 min, removing the precipitate, and taking the supernatant to obtain the cold pressed flaxseed crude oil.

4. A refining process for low glycidyl ester and low trichloropropane ester linseed oil according to claim 1, characterized in that: The step 8) degumming and refining comprises the following steps: Heat the crude oil to the hydration operating temperature of 80-85°C, slowly add 0.02-0.05 times the volume of the crude oil and 90-95°C water, add for 5-10 minutes, stir at 30-60rpm, after the phospholipid particles and the oil are obviously separated, let it stand and settle for 4-6 hours; use a centrifuge 5000-8000g to separate the settled mixture to remove the phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80°C.

5. A process for refining low glycidyl ester and low trichloropropane ester linseed oil according to claim 1, characterized in that: The step 9) deacidification and refining comprises the following steps: heating the crude oil to 70-80° C., determining the amount of alkali solution according to the content of free fatty acids in the oil and the required neutralization degree, slowly adding the alkali solution, stirring evenly at a stirring speed of 60-100 rpm, stirring and reacting for 20-40 minutes, until the emulsion and soap particles are obviously separated from the oil; standing and settling for 4-6 hours; separating the settled mixture using a centrifuge of 10000-15000g to remove phospholipid impurities therein, and the separation temperature of the centrifuge is 70-80° C.

6. A process for refining linseed oil low in glycidyl ester and trichloropropane ester according to claim 1, characterized in that: The step 10) water washing comprises the following steps: heating the oil temperature to 75-85° C., adding 0.05-0.1 times the volume of the oil in soft water at the same temperature, stirring and mixing at a speed of 10-20 rpm for 10-20 min, then standing for 1-2 h to separate the oil and water, and taking the oil layer for subsequent treatment.

7. A process for refining linseed oil low in glycidyl ester and trichloropropanol ester according to claim 1, characterized in that: The step 11) dehydration comprises the following steps: heating the oil temperature to 95-100° C., maintaining the vacuum degree not less than 700 mm Hg, stirring at a speed of 30-40 rpm, and reducing the water content to below 3%.

8. The refining process of low glycidyl ester and low trichloropropane ester linseed oil according to claim 1, characterized in that: The decolorization step 12) comprises the following steps: S1 Preheating and mixing: Pump the oil to be treated into the decolorizing tank, turn on the agitator for low-speed stirring, the stirring speed is 50-100rpm, and at the same time, start the heating system to gradually increase the oil temperature to between 90 and 105°C to promote full contact and mixing between the adsorbent and the oil; S2 adsorbent addition: When the oil temperature reaches the set value, slowly add the white clay or activated carbon adsorbent into the decolorization tank; S3 decolorization reaction: Under continuous stirring and constant temperature conditions, allow the adsorbent to fully contact the oil for 30-60 minutes, so that the adsorbent can fully absorb the pigments, oxides and other insoluble impurities in the oil; S4 Vacuum degassing: During the decolorization process, the vacuum system is turned on to reduce the pressure in the decolorization tank to remove volatile gases and trace moisture in the oil, further improving the quality of the oil.

9. A process for refining linseed oil low in glycidyl ester and trichloropropane ester according to claim 1, characterized in that: The step 13) of deodorization comprises the following steps: I. Low temperature operation: pump the linseed oil to be treated into the deodorization tower, turn on the vacuum system and control the amount of steam injected to form a negative pressure and temperature of 130-150℃ inside the equipment; II. Steam distillation: under the above vacuum and temperature conditions, the volatile substances and bad odors in the oil are removed by steam distillation; III. Antioxidant addition: During the deodorization process, a pre-prepared 5wt% citric acid aqueous solution was added to the oil 0.05-0.1 times the volume; IV. Cooling and collection: After deodorization and antioxidant treatment, the oil is quickly cooled to below room temperature through a cooling system for storage to obtain low glycidyl ester and low trichloropropanol ester linseed oil.

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