Processing method of flaxseed oil for removing bitterness and fishiness and efficiently retaining antioxidant nutrients flaxseed and oil processed thereby

Abstract

The application relates to the field of food processing, and discloses a processing method for removing bitterness and fishy smell from flaxseed oil and efficiently retaining antioxidant nutrients flaxseed oil and oil processed by the method, wherein the method comprises the following steps: (1) mixing flaxseed oil with a debittering agent to obtain debittered flaxseed oil; (2) sequentially performing water vapor conditioning treatment and deodorization treatment on the flaxseed oil to obtain deodorized flaxseed oil; wherein the temperature of the deodorization treatment is 45-100 DEG C higher than that of the water vapor conditioning treatment. The method can efficiently remove bitter and fishy substances in the flaxseed oil, reduce the loss of alpha-linolenic acid, flaxseed oil (containing tocopherol, PC-8 and polyphenol) and sterol in the flaxseed oil, improve the retention rate of alpha-linolenic acid, flaxseed oil and sterol in the flaxseed oil, and further improve the quality of the flaxseed oil.

Description

Technical Field

[0001] This invention relates to the field of food processing, specifically to a method for processing flaxseed oil to remove bitterness and fishy smell while efficiently retaining the antioxidant nutrient linoleic acid, and the processed oil thereof. Background Technology

[0002] Flax is one of the world's top ten oilseed crops. In China, it is mainly distributed in Northwest and North China, with Gansu and Ningxia being the main producing areas. It is the fourth largest oilseed crop after rapeseed, soybeans, and peanuts. Flaxseed oil is extracted from flaxseeds through pressing and is also known as linseed oil. Flaxseed oil contains a variety of functional active ingredients, such as alpha-linolenic acid, linoleic acid, vitamins, and linolenic acid lignans. Alpha-linolenic acid helps lower cholesterol and blood lipids, thereby reducing the risk of cardiovascular and cerebrovascular diseases; linolenic acid lignans have a preventive effect on estrogen-dependent diseases such as breast cancer, prostate cancer, premenstrual syndrome, and osteoporosis. Therefore, flaxseed oil is popular among the public.

[0003] However, due to factors such as the flaxseed oil extraction process and its fatty acid composition, existing flaxseed oil products generally have a bitter or fishy taste, which affects the eating experience.

[0004] CN116349739A discloses a method for preparing deodorized flaxseed oil. The method includes roasting flaxseeds at 190-250℃, grinding or ultra-finely pulverizing the roasted flaxseeds, adding boiling water and stirring, then pressing to obtain modified flaxseed meal. Finally, the modified flaxseed meal is mixed with refined flaxseed oil that has undergone degumming, deacidification, and deodorization treatment, and subjected to a high-temperature reaction to obtain flaxseed oil with no or low flaxseed odor. While this method can remove bitter substances, the removal rate of flaxseed odor substances is low, and the high-temperature treatment destroys the nutritional components in the flaxseed oil, especially the content of linolenic acid and α-linolenic acid.

[0005] CN105112157A discloses a method for debittering and removing the fishy smell from flaxseed oil. The method involves contacting flaxseed oil with a mixture of 5%-10% (oil weight) of dehulled flaxseed meal powder and 1%-3% (oil weight) of diatomaceous earth, and stirring for 3-5 hours. This method can remove the bitterness and fishy smell from flaxseed oil. However, it requires dehulling the flaxseeds and then cold-pressing the resulting flaxseed kernels to obtain the oil. This method results in the loss of flax lignans, reducing the quality of the flaxseed oil.

[0006] In summary, existing technologies for removing bitterness or fishy odor from flaxseed oil focus more on changes in the bitter or fishy substances in the oil, without understanding the changes in the nutrients. Some methods for removing bitterness and fishy odor can also cause an imbalance in the ratio of monounsaturated fatty acids (α-linolenic acid) and polyunsaturated fatty acids (linoleic acid) in flaxseed oil, as well as the loss of nutrients (such as linolenic acid and sterols), thus reducing the quality of flaxseed oil.

[0007] With rising living standards and increasing health awareness, the nutritional content of flaxseed oil has attracted growing attention. Therefore, there is an urgent need to find a method for preparing flaxseed oil that can effectively remove bitter and fishy odors while improving the nutritional content, thereby enhancing the quality of the flaxseed oil. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low removal rate of bitter and fishy substances in flaxseed oil and serious loss of nutrients (especially α-linolenic acid, linolenic acid, and sterols) in existing technologies. This invention provides a processing method for debittering and removing fishy substances from flaxseed oil while efficiently retaining the antioxidant nutrient linolenic acid, and the processed oil thereof. This method can efficiently remove bitter and fishy substances from flaxseed oil while improving the retention rate of α-linolenic acid, linolenic acid (including tocopherol, PC-8, and polyphenols), and sterols in flaxseed oil, thereby improving the quality of flaxseed oil.

[0009] To achieve the above objectives, the first aspect of the present invention provides a method for removing the fishy smell from flaxseed oil, wherein the method includes subjecting the flaxseed oil to steam conditioning and deodorizing treatment in sequence;

[0010] The deodorization treatment temperature is 45-100°C higher than the steam conditioning treatment temperature. A second aspect of the invention provides a method for removing bitterness and fishy odor from flaxseed oil, comprising the following steps:

[0011] (1) Mix flaxseed oil with a debittering agent to obtain debittered flaxseed oil;

[0012] (2) According to the method of the present invention, the debittered flaxseed oil is subjected to steam conditioning and deodorization treatment in sequence to obtain deodorized flaxseed oil.

[0013] A third aspect of the present invention provides flaxseed oil prepared by the method described herein.

[0014] Preferably, the flaxseed oil contains ≤6 μg / g of cyclic peptide E, ≤5 μg / g of fishy odor substances, ≥54 wt% of α-linolenic acid, ≥363 μg / g of tocopherol in linolenic acid, ≥170 μg / g of PC-8 in linolenic acid, ≥10 μg / g of polyphenols in linolenic acid, and ≥5260 μg / g of sterols.

[0015] Preferably, the flaxseed oil has the following characteristics: removal rate of cyclic peptide E ≥ 96%, removal rate of fishy substances ≥ 94%, retention rate of α-linolenic acid ≥ 99.5%, retention rate of tocopherol in linolenic acid ≥ 97%, retention rate of PC-8 in linolenic acid ≥ 97%, retention rate of polyphenols in linolenic acid ≥ 55%, and retention rate of sterols ≥ 95%.

[0016] Through the above technical solution, the present invention has achieved the following beneficial technical effects:

[0017] (1) The method of the present invention can efficiently remove bitter and fishy substances from flaxseed oil. In the preferred embodiment, the removal rate of cyclic peptide E and fishy substances (volatile aldehydes and ketones) is over 95%.

[0018] (2) The method of the present invention can maximize the retention of α-linolenic acid, linolenic acid and sterol in flaxseed oil, improve the retention rate of α-linolenic acid, linolenic acid and sterol in flaxseed oil, and thus improve the quality and applicability of flaxseed oil. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] In this invention, "deodorization" and "removal of fishy smell" both refer to the removal of fishy-smelling substances from oils and can be used interchangeably.

[0021] The first aspect of the present invention provides a method for removing the fishy smell from flaxseed oil, wherein the method includes subjecting the flaxseed oil to steam conditioning and deodorizing treatment in sequence;

[0022] The temperature of the deodorization treatment is 45-100°C higher than the temperature of the steam conditioning treatment.

[0023] Preferably, the temperature of the deodorization treatment is 45-85°C higher than the temperature of the steam conditioning treatment.

[0024] In this invention, the temperature difference between the deodorization treatment and the steam conditioning treatment meets the above-mentioned range, which can further enhance the removal effect of fishy substances (volatile aldehydes and ketones), thereby significantly reducing the content of fishy substances in flaxseed oil.

[0025] According to some embodiments of the present invention, the steam conditioning process involves contacting flaxseed oil with steam, wherein the mass ratio of flaxseed oil to steam is 100:(0.5-2).

[0026] Preferably, the mass ratio of the flaxseed oil to the water vapor is 100:(0.5-1).

[0027] In this invention, the increase in moisture content in the flaxseed oil after conditioning meets the above-mentioned range, which is more conducive to reducing the proportion of fishy substances (volatile aldehydes and ketones) in the oil and achieving a stronger removal effect of fishy substances (volatile aldehydes and ketones).

[0028] According to some embodiments of the present invention, the conditions for the steam conditioning treatment include: a temperature of 105-125°C, a pressure of 150-250 kPa, and a time of 5-20 min.

[0029] The inventors of this invention have discovered that, under low-temperature conditions, introducing steam into flaxseed oil for conditioning can further enhance the deodorizing effect, thereby improving the quality of the oil.

[0030] In this invention, there are no special requirements for the equipment used for steam conditioning, as long as it can fully mix flaxseed oil and steam, for example, it can be carried out in a conditioning tank.

[0031] According to some embodiments of the present invention, the deodorization treatment method includes single-temperature deodorization and / or dual-temperature deodorization. Single-temperature deodorization refers to deodorizing flaxseed oil at the same temperature; dual-temperature deodorization refers to the deodorization process of flaxseed oil including low-temperature deodorization and high-temperature deodorization. There is no particular limitation on the order of low-temperature deodorization and high-temperature deodorization. For example, flaxseed oil can be deodorized at low temperature first and then at high temperature, or it can be deodorized at high temperature first and then at low temperature.

[0032] Preferably, the conditions for single-temperature deodorization include: a temperature of 170-220℃, a time of 40-60 min, and a pressure of 50 Pa-300 Pa.

[0033] Preferably, the conditions for the dual-temperature deodorization include: a time of 45-60 minutes and a pressure of 50 Pa-300 Pa.

[0034] More preferably, the dual-temperature deodorization includes low-temperature deodorization and high-temperature deodorization, wherein the temperature of the low-temperature deodorization is 170-190°C, the temperature of the high-temperature deodorization is 15-50°C higher than the temperature of the low-temperature deodorization, and the time of the high-temperature deodorization is 5-15 minutes.

[0035] More preferably, the temperature of the low-temperature deodorization is 170-180°C, and the temperature of the high-temperature deodorization is 15-25°C higher than the temperature of the low-temperature deodorization.

[0036] A second aspect of the present invention provides a method for removing bitterness and fishy odor from flaxseed oil, wherein the method includes the following steps:

[0037] (1) Mix flaxseed oil with a debittering agent to obtain debittered flaxseed oil;

[0038] (2) According to the method of the present invention, the debittered flaxseed oil is subjected to steam conditioning and deodorization treatment in sequence to obtain deodorized flaxseed oil.

[0039] According to some embodiments of the present invention, the amount of the debittering agent used is 1.5wt%-3wt%, preferably 1.5wt%-2.5wt%, based on the mass of the flaxseed oil.

[0040] According to some embodiments of the present invention, the cumulative specific surface area of ​​the mesopores of the debittering agent accounts for 85%-100% of the cumulative specific surface area of ​​the pores of the debittering agent, preferably 90%-97%.

[0041] According to some embodiments of the present invention, the cumulative volume of the mesopores of the debittering agent accounts for 70%-85% of the cumulative volume within the pores of the debittering agent, preferably 75%-82%.

[0042] In this invention, the ratio of the cumulative specific surface area of ​​the mesopores of the debittering agent to the cumulative specific surface area of ​​the pores refers to the ratio of the specific surface area of ​​the pores with a diameter of 2nm-50nm to the specific surface area of ​​the pores with a diameter of 0nm-180nm; the ratio of the cumulative volume of the mesopores of the debittering agent to the cumulative volume of the pores refers to the ratio of the volume of the pores with a diameter of 2nm-50nm to the volume of the pores with a diameter of 0nm-180nm.

[0043] In this invention, when the pore structure of the debittering agent meets the above requirements, the debittering agent can efficiently adsorb small molecule substances, thereby significantly improving the adsorption capacity of the debittering agent for bitter small molecule compounds (cyclic peptide E), so that the debittering agent has a better debittering effect.

[0044] In this invention, there is no particular limitation on the type of debittering agent, as long as it possesses the aforementioned defined pore structure characteristics. Preferably, the debittering agent may be selected from at least one of activated clay, attapulgite, bentonite, activated carbon, and silica gel.

[0045] According to some embodiments of the present invention, the mixing conditions include a temperature of 95-115°C and a time of 30-60 min.

[0046] According to some embodiments of the present invention, the method further includes degumming and / or deacidifying the flaxseed oil before mixing with the debittering agent, so that the phosphorus content of the flaxseed oil is less than 10 ppm.

[0047] The inventors of this invention discovered that the phospholipids naturally present in flaxseed oil affect the adsorption effect of debittering agents on bitter substances in flaxseed oil, thus impacting the quality of the oil. Phospholipids in flaxseed oil can be divided into hydrated phospholipids and non-hydrated phospholipids. Hydrated phospholipids are removed using degumming processes, such as by heating water. Non-hydrated phospholipids cannot be directly removed by hydration but can be removed through deacidification processes, such as alkali refining to convert non-hydrated phospholipids into hydrated phospholipids. To ensure the effectiveness of the deacidification process in removing non-hydrated phospholipids, a water washing method is needed after alkali refining to enhance the removal effect.

[0048] Preferably, the degumming process includes: heating flaxseed oil to 60-80°C, adding water at the same temperature (the amount of water is 1wt%-2wt% of the mass of flaxseed oil), stirring for 10-30 minutes, separating the aqueous phase from the oil phase, thereby removing hydrophilic phospholipids from the flaxseed oil and obtaining degummed oil.

[0049] Preferably, the deacidification treatment method includes: adding an alkaline solution to flaxseed oil, wherein the amount of alkaline solution added (M) is calculated according to the formula M = 7.13 × 10⁻⁶. -4 ×G 油 ×AV 油 The calculation shows that G 油 AV represents the weight of flaxseed oil involved in the reaction. 油 The acid value of flaxseed oil before alkali refining is given; the mass concentration of the alkali solution is 6%-10%. To ensure the effective removal of non-hydrated phospholipids, a certain amount of superalkali can be added on the basis of the amount of alkali added in actual operation. The amount of superalkali is controlled at 0-20wt%. After alkali refining, the oil is centrifuged to remove the aqueous phase; the oil is heated to 85-95℃, and water at the same temperature is added (the amount of water is 3wt%-6wt% of the mass of flaxseed oil). The oil is washed for 10-30 minutes to separate the aqueous phase from the oil phase and obtain deacidified oil.

[0050] In this invention, the phosphorus content of flaxseed oil meets the above-mentioned range, and the phospholipid content in flaxseed oil is low. When flaxseed oil is mixed with the debittering agent, it will not clog the pores of the debittering agent. Bitter substances in flaxseed oil are more easily adsorbed by the debittering agent, and the removal effect of bitter substances is better.

[0051] In this invention, the steam conditioning and deodorization treatments in step (2) are the same as the treatment methods involved in the method described in this invention, and will not be repeated here.

[0052] According to some embodiments of the present invention, the method further includes dewaxing the deodorized flaxseed oil.

[0053] In this invention, the flaxseed oil, even after debittering and deodorizing treatments, still contains wax. This wax affects the oil's transparency and its digestibility, as well as its aroma and taste. Therefore, dewaxing the deodorized flaxseed oil yields an oil with better taste and higher quality.

[0054] Preferably, the dewaxing method includes mixing the deodorized flaxseed oil with a filter aid.

[0055] More preferably, the mass ratio of the deodorizing flaxseed oil to the filter aid is 100:(0.3-0.5).

[0056] More preferably, the filter aid is selected from at least one of diatomaceous earth, bentonite, and perlite.

[0057] More preferably, the mixing conditions include: a temperature of 4-8°C and a time of 10-20 hours.

[0058] A third aspect of the present invention provides flaxseed oil prepared by the method of the present invention.

[0059] Preferably, the flaxseed oil contains ≤6 μg / g of cyclic peptide E, ≤5 μg / g of fishy odor substances, ≥54 wt% of α-linolenic acid, ≥363 μg / g of tocopherol in linolenic acid, ≥170 μg / g of PC-8 in linolenic acid, ≥10 μg / g of polyphenols in linolenic acid, and ≥5260 μg / g of sterols.

[0060] Preferably, the flaxseed oil has the following characteristics: removal rate of cyclic peptide E ≥ 96%, removal rate of fishy substances ≥ 94%, retention rate of α-linolenic acid ≥ 99.5%, retention rate of tocopherol in linolenic acid ≥ 97%, retention rate of PC-8 in linolenic acid ≥ 97%, retention rate of polyphenols in linolenic acid ≥ 55%, and retention rate of sterols ≥ 95%.

[0061] In this invention, the fishy odor substance is the sum of volatile aldehyde and ketone small molecule compounds; linolenic acid refers to the general term for tocopherols and polyphenols, wherein tocopherols refer to the sum of tocopherol, tocotrienol, PC-8 (Plastochromanol-8, a natural compound with a similar structure to γ-tocopherol) and its series derivatives; polyphenols refer to the sum of free and bound polyphenols, including linolenic acid; sterols refer to the sum of free and esterified forms of 4-demethylsterol compounds (including sterols, steranols and sterenols).

[0062] In this invention, flaxseed is a commercially available product. Currently, the main flaxseed producing areas are Russia, Kazakhstan, Canada, and China, with a wide variety of varieties. Different manufacturers produce flaxseed with variations in origin or variety, resulting in differences in the polyphenol content. Consequently, the polyphenol content in flaxseed oil also varies. The inventors of this invention discovered that phenylalanine is a precursor for polyphenol synthesis, and the polyphenol content in flaxseed oil is related to the phenylalanine content in the flaxseed. When the phenylalanine content in flaxseed is greater than 1 wt%, the polyphenol content in the flaxseed oil is high; when the phenylalanine content in flaxseed is less than 1 wt%, the polyphenol content in the flaxseed oil is low. The method of the present invention does not have a particular limitation on the polyphenol content in flaxseed (or flaxseed oil). The method of the present invention can maximize the retention of polyphenols in flaxseed oil when treating flaxseed oil with different polyphenol contents, thereby improving the polyphenol retention rate. In particular, when the method of the present invention is used to treat flaxseed (or flaxseed oil) with low polyphenol content, the loss of polyphenols in the flaxseed oil is less and the polyphenol retention rate is higher.

[0063] According to a particularly preferred embodiment of the present invention, a method for removing bitterness and fishy odor from flaxseed oil is provided, the method comprising the following steps:

[0064] (1) Heat the flaxseed oil that has been degummed and deacidified to 100-110℃, add activated clay to the flaxseed oil, and debitter it for 30-60 minutes to obtain debittered flaxseed oil.

[0065] Among them, the cumulative specific surface area of ​​the mesopores of activated clay accounts for 90%-97% of the cumulative specific surface area of ​​the pores of activated clay, and the cumulative volume of the mesopores of activated clay accounts for 75%-85% of the cumulative volume of the pores of activated clay.

[0066] The amount of activated clay added is 1.5wt%-2wt% of the weight of deacidified linseed oil.

[0067] (2) Heat the debittered flaxseed oil to 110-120℃, and send water vapor into the conditioning tank. Control the pressure in the conditioning tank to 150-250kPa, and mix the debittered flaxseed oil with water vapor for 5-20 minutes to obtain the conditioning flaxseed oil.

[0068] The mass ratio of debittered flaxseed oil to water vapor is 100:0.5-1;

[0069] (3) The conditioned flaxseed oil is transferred to a deodorization tower and the fishy smell is removed by a dual-temperature deodorization process (first low temperature deodorization and then high temperature deodorization) to obtain deodorized flaxseed oil;

[0070] The deodorization time for dual-temperature deodorization is 50-60 minutes, the deodorization time for high temperature is 5-10 minutes, the temperature for low-temperature deodorization is controlled at 170-180℃, the temperature for high-temperature deodorization is 20℃-30℃ higher than the temperature for low-temperature deodorization, and the pressure of the deodorization tower is 100-200Pa.

[0071] (5) Add diatomaceous earth to the deodorized flaxseed oil, then cool it to 4-8℃ and keep it for 10-20 hours. After filtration, the finished flaxseed oil is obtained.

[0072] The mass ratio of flaxseed oil to diatomaceous earth is 100:(0.3-0.5).

[0073] The present invention will be described in detail below through embodiments.

[0074] Flaxseed 1 was purchased from Yiwu Shanbao Supply Chain Management Co., Ltd. The phenylalanine content of flaxseed 1 was 1.15%, and the flaxseed crude oil obtained after pressing flaxseed 1 (Preparation Example 1) had a high polyphenol content (89.9 μg / g).

[0075] Flaxseed 2 was purchased from Qingdao Dehui Marine Biotechnology Co., Ltd. The phenylalanine content of flaxseed 2 was 0.8%, and the polyphenol content of the crude flaxseed oil obtained after pressing flaxseed 2 (Preparation Example 2) was low (21.6 μg / g).

[0076] Activated clay, activated carbon, attapulgite, and bentonite were purchased from Huangshan Baiyue Activated Clay Co., Ltd., Chongqing Feiyang Environmental Protection Technology Co., Ltd., Jiangsu Shenlite Biotechnology Co., Ltd., and Zhangjiakou Saibei Chemical Co., Ltd., respectively.

[0077] The percentage of the total specific surface area of ​​the mesopores of the debittering agent to the total specific surface area of ​​the pores (%) = 100% × (specific surface area of ​​the pores with an internal diameter of 2nm-50nm in the debittering agent / specific surface area of ​​the pores with an internal diameter of 0nm-180nm in the debittering agent).

[0078] The percentage of the total volume of mesopores in the debittering agent to the total volume of pores (%) = 100% × (volume of pores with an internal diameter of 2nm-50nm in the debittering agent / volume of pores with an internal diameter of 0nm-180nm in the debittering agent).

[0079] The specific surface area of ​​the pores with an internal diameter of 0nm-180nm, the specific surface area of ​​the pores with an internal diameter of 0nm-180nm, the pore volume of the pores with an internal diameter of 2nm-50nm, and the pore volume of the pores with an internal diameter of 0nm-180nm were determined according to GB / T19587-2017 Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method.

[0080] The phosphorus content of degummed / deacidified flaxseed oil was determined using the method specified in GB 5009.87-2016 National Food Safety Standard - Determination of Phosphorus in Food - Method I - Molybdenum Blue Spectrophotometric Method.

[0081] The moisture content of degummed / deacidified linseed oil was determined according to the method of "Determination of Moisture Content in Chemical Products - Karl Fischer Method (General Method)" in GB / T 6283-2008, using a Metrohm (915KF) Karl Fischer moisture analyzer.

[0082] Unless otherwise specified, all materials are commercially available.

[0083] Preparation Example 1

[0084] Flaxseeds 1, which were roasted at 60℃ for 40 minutes, were cold-pressed in a screw press. After filtration, crude flaxseed oil was obtained, with a polyphenol content of 89.9 μg / g.

[0085] Preparation Example 2

[0086] Flaxseeds 2, which were roasted at 60℃ for 40 minutes, were poured into a screw press for cold pressing. After filtration, crude flaxseed oil was obtained, and the polyphenol content in the crude flaxseed oil was 21.6 μg / g.

[0087] Example 1

[0088] This embodiment illustrates the method used in this invention to remove bitterness and fishy smell from flaxseed oil.

[0089] (1) Degumming: Add hot water at the same temperature (the amount of hot water added is 1.5 wt% of the mass of the flaxseed oil) to the flaxseed oil heated to 75°C (Preparation Example 1), stir for 30 min and then separate the phospholipids to obtain degummed flaxseed oil.

[0090] (2) Deacidification: Add sodium hydroxide solution (sodium hydroxide solution mass concentration is 10%) to the above degummed flaxseed oil. The amount of sodium hydroxide solution added is 10wt% of the mass of degummed flaxseed oil. After the oil is alkali-refined, the soap foot is separated by centrifugation. The separation liquid is heated to 90℃. Then, 4wt% of the mass of degummed flaxseed oil is added to the separation liquid and washed with water for 10min to obtain deacidified flaxseed oil.

[0091] The phosphorus content of deacidified flaxseed oil is 3.2 ppm.

[0092] (3) Debittering: Heat the above deacidified flaxseed oil to 105℃, add activated clay to the deacidified flaxseed oil, and debitter for 30 minutes to obtain debittered flaxseed oil;

[0093] The debittered flaxseed oil contains 0.1 wt% moisture.

[0094] The amount of activated clay added is 2 wt% of the weight of deacidified flaxseed oil.

[0095] Among them, the cumulative specific surface area of ​​the mesopores of the activated clay accounted for 91.3% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of the activated clay accounted for 79.3% of the cumulative volume of the pores.

[0096] (4) Conditioning: After heating the debittered flaxseed oil to 115°C, transfer it to a conditioning tank and introduce water vapor into the conditioning tank (the mass ratio of debittered flaxseed oil to water vapor is 100:1). Control the pressure inside the conditioning tank to 200 kPa and mix the debittered flaxseed oil and water vapor thoroughly for 10 minutes to obtain conditioned flaxseed oil.

[0097] (5) Deodorization: The conditioned flaxseed oil is transferred to a deodorization tower and the fishy smell is removed by a dual-temperature deodorization process (first low temperature deodorization and then high temperature deodorization) to obtain deodorized flaxseed oil;

[0098] The temperature for low-temperature deodorization is controlled at 180℃ and maintained for 50 minutes, the temperature for high-temperature deodorization is controlled at 200℃ and maintained for 10 minutes, and the pressure of the deodorization tower is 200 Pa during the removal of fishy odor.

[0099] (6) Dewaxing: Add diatomaceous earth to the deodorized flaxseed oil, then cool it to 4°C and keep it for 10 hours. After filtration, the finished flaxseed oil A1 is obtained.

[0100] The amount of diatomaceous earth used is 0.5 wt% of the weight of the deodorizing flaxseed oil.

[0101] Example 2

[0102] This embodiment illustrates the method used in this invention to remove bitterness and fishy smell from flaxseed oil.

[0103] (1) Degumming: Add hot water at the same temperature (the amount of hot water added is 2 wt% of the mass of the flaxseed oil) to the flaxseed oil heated to 60°C (Preparation Example 1), stir for 30 min and then separate the phospholipids to obtain degummed flaxseed oil.

[0104] (2) Deacidification: Add sodium hydroxide solution (sodium hydroxide solution mass concentration is 6%) to the above degummed flaxseed oil. The amount of sodium hydroxide solution added is 15wt% of the mass of degummed flaxseed oil. After the oil is alkali-refined, the soap foot is separated by centrifugation. The separation liquid is heated to 95℃, and isothermal hot water of 6wt% of the mass of degummed flaxseed oil is added to the separation liquid. The mixture is washed with water for 15min to obtain deacidified flaxseed oil.

[0105] The phosphorus content of deacidified flaxseed oil is 5.7 ppm.

[0106] (3) Debittering: Heat the above deacidified flaxseed oil to 115°C, add a debittering agent (the mass ratio of activated clay and silica gel is 9:1) to the deacidified flaxseed oil, debitter for 40 minutes to obtain debittered flaxseed oil.

[0107] The debittered flaxseed oil contains 0.1 wt% moisture.

[0108] The amount of debittering agent added is 1.5 wt% of the weight of deacidified linseed oil;

[0109] Among them, the cumulative specific surface area of ​​the mesopores of the debittering agent accounts for 95.3% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of the debittering agent accounts for 83.6% of the cumulative volume of the pores.

[0110] (4) Conditioning: After heating the debittered flaxseed oil to 125°C, transfer it to a conditioning tank and introduce steam into the conditioning tank (the mass ratio of debittered flaxseed oil to steam is 100:0.5). Control the pressure inside the conditioning tank to 250 kPa and mix the debittered flaxseed oil and steam thoroughly for 5 minutes to obtain the conditioned flaxseed oil.

[0111] (5) Deodorization: The conditioned flaxseed oil is transferred to a deodorization tower and the fishy smell is removed by a single-temperature deodorization process to obtain deodorized flaxseed oil.

[0112] Among them, the temperature for single-temperature deodorization is controlled at 200℃ and maintained for 50 minutes, and the pressure of the deodorization tower is 250Pa during the removal of fishy odor;

[0113] (6) Dewaxing: Add diatomaceous earth to the deodorized flaxseed oil, then cool it to 8°C and keep it for 20 hours. After filtration, the finished flaxseed oil A2 is obtained.

[0114] The amount of diatomaceous earth used is 0.3 wt% of the weight of the deodorizing flaxseed oil.

[0115] Example 3

[0116] This embodiment illustrates the method used in this invention to remove bitterness and fishy smell from flaxseed oil.

[0117] (1) Degumming: Add hot water at the same temperature (the amount of hot water added is 1 wt% of the mass of the flaxseed oil) to the flaxseed oil heated to 80°C (Preparation Example 1), stir for 30 min and then separate the phospholipids to obtain degummed flaxseed oil.

[0118] (2) Deacidification: Add sodium hydroxide solution (8% by mass) to the above degummed flaxseed oil. The amount of sodium hydroxide solution added is 5 wt% of the mass of the degummed flaxseed oil. After the oil is alkali-refined, the soapstock is separated by centrifugation. The separation liquid is heated to 85°C. Then, 3 wt% of the mass of the degummed flaxseed oil is added to the separation liquid, and the mixture is washed for 15 min to obtain deacidified flaxseed oil.

[0119] The phosphorus content of deacidified flaxseed oil is 9.3 ppm.

[0120] (3) Debittering: Heat the above deacidified linseed oil to 95°C, add attapulgite to the deacidified linseed oil, and debitter for 60 minutes to obtain debittered linseed oil.

[0121] The debittered flaxseed oil contains 0.3 wt% moisture.

[0122] The amount of attapulgite added is 2 wt% of the weight of deacidified linseed oil;

[0123] Among them, the cumulative specific surface area of ​​the mesopores of attapulgite soil accounts for 87.9% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of attapulgite soil accounts for 75.1% of the cumulative volume of the pores.

[0124] (4) Conditioning: After heating the debittered flaxseed oil to 105°C, transfer it to a conditioning tank and introduce steam into the conditioning tank (the mass ratio of debittered flaxseed oil to steam is 100:1). Control the pressure inside the conditioning tank to 150 kPa and mix the debittered flaxseed oil and steam thoroughly for 20 minutes to obtain conditioned flaxseed oil.

[0125] (5) Deodorization: The conditioned flaxseed oil is transferred to a deodorization tower and the fishy smell is removed by a single-temperature deodorization process to obtain deodorized flaxseed oil.

[0126] The temperature for single-temperature deodorization is controlled at 220℃ and maintained for 60 minutes. During the removal of fishy odor, the pressure of the deodorization tower is 200 Pa.

[0127] (6) Dewaxing: Add diatomaceous earth to the deodorized flaxseed oil, then cool it to 6°C and keep it for 15 hours. After filtration, the finished flaxseed oil A3 is obtained.

[0128] The amount of diatomaceous earth used is 0.5 wt% of the weight of the deodorizing flaxseed oil.

[0129] Example 4

[0130] Following the method of Example 1, the difference is that the crude flaxseed oil is the crude oil obtained in Preparation Example 2, resulting in finished flaxseed oil A4.

[0131] Example 5

[0132] The method of Example 1 is followed, except that the degummed flaxseed oil is not deacidified and the phosphorus content of the degummed flaxseed oil is 6 ppm, resulting in the finished flaxseed oil A5.

[0133] Example 6

[0134] The method of Example 1 is different in that the cumulative specific surface area of ​​the mesopores of the activated clay accounts for 85.3% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of the activated clay accounts for 73.6% of the cumulative volume of the pores, thus obtaining the finished flaxseed oil A6.

[0135] Example 7

[0136] The method of Example 1 is different in that the cumulative specific surface area of ​​the mesopores of the activated clay accounts for 81.2% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of the activated clay accounts for 65.1% of the cumulative volume of the pores, thus obtaining the finished flaxseed oil A7.

[0137] Example 8

[0138] The method of Example 1 is different in that the cumulative specific surface area of ​​the mesopores of the activated clay accounts for 25.2% of the cumulative specific surface area of ​​the pores, and the cumulative volume of the mesopores of the activated clay accounts for 55.1% of the cumulative volume of the pores, thus obtaining the finished flaxseed oil A8.

[0139] Example 9

[0140] The method of Example 1 is followed, except that the amount of activated clay added is 3.5 wt% of the mass of deacidified flaxseed oil, and the finished flaxseed oil A9 is obtained.

[0141] Example 10

[0142] The method of Example 1 is different in that the mass ratio of debittered flaxseed oil to water vapor is 100:3, and the finished flaxseed oil A10 is obtained.

[0143] Example 11

[0144] The method of Example 1 is the same, except that the conditioning temperature is 140°C to obtain the finished flaxseed oil A11.

[0145] Example 12

[0146] The method of Example 1 is different in that the high-temperature deodorization temperature is 10°C higher than the low-temperature deodorization temperature, and the finished flaxseed oil A12 is obtained.

[0147] Example 13

[0148] The method of Example 1 is different in that the flaxseed oil is not debittered to obtain the finished flaxseed oil A13.

[0149] Comparative Example 1

[0150] The method of Example 1 is followed, except that the flaxseed oil is not conditioned but the low-temperature deodorization time is extended to 60 minutes. The total time for conditioning and low-temperature deodorization is the same as that of Example 1, and the finished flaxseed oil B1 is obtained.

[0151] Comparative Example 2

[0152] The method of Example 1 is different in that water vapor is not supplied in the conditioning tank to obtain the finished flaxseed oil B2.

[0153] Test Example 1

[0154] The contents of cyclic peptide E, fishy odor substances, α-linolenic acid, vitamin E, sterols and polyphenols in the crude flaxseed oil of Preparation Examples 1-2 and the finished flaxseed oil of the above examples and comparative examples were tested respectively (the results are shown in Table 1). The removal rates of cyclic peptide E and fishy odor substances and the retention rates of α-linolenic acid, vitamin E, sterols and polyphenols in the finished flaxseed oil were calculated.

[0155] The fishy smell refers to the sum of small molecule compounds of volatile aldehydes and ketones; linolenic acid refers to the sum of tocopherols and polyphenols, of which tocopherols refer to tocopherol, tocotrienols, PC-8 (Plastochromanol-8, a natural compound with a similar structure to γ-tocopherol) and their series of derivatives; polyphenols refer to the sum of free and bound polyphenols, including linolenic acid; sterols refer to the sum of free and esterified forms of 4-demethylsterol compounds (including sterols, steranols and sterenols).

[0156] The content of cyclic peptide E was determined according to the method in "Determination of Cyclic Peptide A and Cyclic Peptide E in Flaxseed Oil (Draft for Comments)" (Grain and Oil Inspection).

[0157] The content of fishy odor substances was determined according to the method of "T / CCOA 68-2023 Determination of Volatile Flavor Components in Edible Vegetable Oils by Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry".

[0158] The content of α-linolenic acid was determined according to the method of GB 5009.168-2016 National Food Safety Standard - Determination of Fatty Acids in Food - Third Method - Normalization Method.

[0159] The content of tocopherol was determined according to the method of GB 5009.82-2016 National Food Safety Standard - Determination of Vitamins A, D and E in Food (Second Method).

[0160] The content of PC-8 was determined according to the standard GB / T 26635-2011 "Determination of Tocopherol and Tocotrienol Content in Animal and Vegetable Oils by High Performance Liquid Chromatography".

[0161] The polyphenol content was determined according to the standard LS / T 6119-2017 Grain and Oil Inspection: Determination of Polyphenols in Vegetable Oils by Spectrophotometry.

[0162] The sterol content was determined according to the method of "GB / T 25223-2010 Determination of Sterol Composition and Total Sterol Content in Animal and Vegetable Oils by Gas Chromatography".

[0163] The removal rate of cyclic peptide E = 100% × (content of cyclic peptide E in crude flaxseed oil - content of cyclic peptide E in finished flaxseed oil) / content of cyclic peptide E in crude flaxseed oil.

[0164] The removal rate of fishy odor substances = 100% × (content of fishy odor substances in crude flaxseed oil - content of fishy odor substances in finished flaxseed oil) / content of fishy odor substances in crude flaxseed oil.

[0165] Retention rate of α-linolenic acid (%) = 100% × (α-linolenic acid content in the product / α-linolenic acid content in the crude oil).

[0166] Tocopherol retention rate (%) = 100% × (tocopherol content in product / tocopherol content in crude oil).

[0167] PC-8 retention rate (%) = 100% × (PC-8 content in product / PC-8 content in crude oil).

[0168] Polyphenol retention rate (%) = 100% × (polyphenol content in product / polyphenol content in crude oil).

[0169] Sterol retention rate (%) = 100% × (sterol content in product / sterol content in crude oil).

[0170] Table 1

[0171]

[0172]

[0173] A comparison of Examples 1-4 with Examples 5-13 shows that the flaxseed oil prepared by the preferred debittering and deodorizing method of the present invention has a higher removal rate of cyclic peptide E and fishy substances, and also a higher retention rate of α-linolenic acid, linolenic acid and sterols in the flaxseed oil, which further improves the quality and applicability of the flaxseed oil.

[0174] Compared with the examples, Comparative Example 1 did not undergo conditioning treatment, resulting in a decrease in the removal rate of fishy odor substances in the oil, while the retention rates of α-linolenic acid, linolenic acid, and sterols in the oil also decreased; in Comparative Example 2, no water vapor was transported during the conditioning treatment, resulting in a significant decrease in the removal rate of fishy odor substances in the oil.

[0175] In summary, this method can effectively remove bitter and fishy substances from flaxseed oil while reducing the loss of α-linolenic acid, linolenic acid, and sterols, thereby increasing the retention rate of α-linolenic acid, linolenic acid, and sterols in flaxseed oil and improving its quality.

[0176] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for removing the odour of linseed oil, characterized in that, The method includes subjecting flaxseed oil to steam conditioning and deodorization treatment in sequence; The temperature of the deodorization treatment is 45-100°C higher than the temperature of the steam conditioning treatment. The conditions for the conditioning treatment include: a temperature of 105-125℃, a pressure of 150-250kPa, and a time of 5-20min. The deodorization treatment method includes dual-temperature deodorization; the conditions for dual-temperature deodorization include: a time of 45-60 minutes and a pressure of 50 Pa-300 Pa; the dual-temperature deodorization includes low-temperature deodorization and high-temperature deodorization, the temperature of low-temperature deodorization is 170-190℃, the temperature of high-temperature deodorization is 15℃-20℃ higher than the temperature of low-temperature deodorization, and the time of high-temperature deodorization is 5-15 minutes; The steam conditioning process involves contacting flaxseed oil with steam, wherein the mass ratio of flaxseed oil to steam is 100:(0.5-2).

2. A method for removing the bitter and rancid taste of linseed oil, characterized in that, The method includes the following steps: (1) Mix flaxseed oil with a debittering agent to obtain debittered flaxseed oil; (2) The method according to claim 1 involves subjecting the debittered flaxseed oil to steam conditioning and deodorization treatment in sequence; The cumulative specific surface area of ​​the mesopores in the debittering agent accounts for 85%-100% of the cumulative specific surface area of ​​the pores in the debittering agent. The cumulative volume of the mesopores of the debittering agent accounts for 70%-85% of the cumulative volume of the pores of the debittering agent.

3. The method according to claim 2, wherein, Based on the mass of the flaxseed oil, the amount of the debittering agent is 1.5wt%-3wt%.

4. The method according to claim 2, wherein, The cumulative specific surface area of ​​the mesopores in the debittering agent accounts for 90%-97% of the cumulative specific surface area of ​​the pores in the debittering agent. And / or, the cumulative volume of the mesopores of the debittering agent accounts for 75%-85% of the cumulative volume of the pores of the debittering agent.

5. The method according to claim 2, wherein, The debittering agent is selected from at least one of activated clay, attapulgite, bentonite, activated carbon, and silica gel.

6. The method according to any one of claims 2-5, wherein, The conditions for mixing with the debittering agent include: a temperature of 95-115℃ and a time of 30-60 minutes.

7. The method according to any one of claims 2-5, wherein, The method further includes degumming and / or deacidifying the flaxseed oil before mixing it with the debittering agent, so that the phosphorus content of the flaxseed oil is less than 10 ppm.

8. The method according to claim 2, wherein, The method also includes dewaxing the deodorized flaxseed oil.

9. The method according to claim 8, wherein, The dewaxing method includes mixing deodorizing flaxseed oil with a filter aid.

10. The method according to claim 9, wherein, The mass ratio of the deodorizing flaxseed oil to the filter aid is 100:(0.3-0.5).

11. The method according to claim 9, wherein, The filter aid is selected from at least one of diatomaceous earth, bentonite, and perlite.

12. The method according to claim 9, wherein, The conditions for mixing with the filter aid include: a temperature of 4-8℃ and a time of 10-20h.

13. A flaxseed oil, characterized in that, The flaxseed oil is prepared by the method described in any one of claims 3-12.

14. The flaxseed oil according to claim 13, wherein, The flaxseed oil contains ≤6 μg / g of cyclic peptide E, ≤5 μg / g of fishy odor substances, ≥54 wt% of α-linolenic acid, ≥363 μg / g of tocopherol in linolenic acid, ≥170 μg / g of PC-8 in linolenic acid, ≥10 μg / g of polyphenols in linolenic acid, and ≥5260 μg / g of sterols.

15. The flaxseed oil according to claim 13, wherein, The flaxseed oil has the following properties: removal rate of cyclic peptide E ≥96%, removal rate of fishy substances ≥94%, retention rate of α-linolenic acid ≥99.5%, retention rate of tocopherol in linolenic acid ≥97%, retention rate of PC-8 in linolenic acid ≥97%, retention rate of polyphenols in linolenic acid ≥55%, and retention rate of sterols ≥95%.

Images