A method for efficiently separating solid fat from a polyunsaturated fatty acid oil

Abstract

The application provides a method for efficiently separating solid fat from polyunsaturated fatty acid oil, which comprises adding a small amount of inert substance into the polyunsaturated fatty acid oil, cooling and crystallizing, adding a certain amount of inert substance for stirring, filtering, obtaining clear polyunsaturated fatty acid oil, collecting filter cake, heating the collected filter cake, dissolving and filtering again, and recovering the filtrate, so as to obtain separated solid fat. Through the method, saturated and low-saturated fatty acid solid fat can be efficiently separated from the polyunsaturated fatty acid oil, winterization crystallization time is short, crystallization is complete, crystal separation is easy, and the phenomenon that part of the solid fat melts and re-enters the filtrate due to long separation and blowing dry time in the conventional process does not occur, so that the yield of the final product is as high as 96.3%-98.2%, and the polyunsaturated fatty acid oil after winterization treatment is clear, and no crystal is precipitated at 0 DEG C for 5 hours.

Description

Technical Field

[0001] This invention mainly describes a highly efficient process for separating solid fats from polyunsaturated fatty acid oils. Specifically, this invention involves adding a small amount of inert substance to the polyunsaturated fatty acid oil, stirring slowly, cooling and crystallizing, then adding the remaining inert substance, stirring, and filtering to obtain a clear polyunsaturated fatty acid oil. Simultaneously, the filter cake is collected, heated to dissolve, and then filtered again; the resulting filtrate is the solid fat. This process not only improves the clarity of the polyunsaturated fatty acid oil but also efficiently collects the solid fat. It is applicable to the winterization of mixtures of one or more polyunsaturated fatty acids, including fish oil (directly extracted ω-3 polyunsaturated fatty acids), algal oil (fermented ω-3 polyunsaturated fatty acids), linoleic acid, conjugated linoleic acid, linolenic acid, and arachidonic acid. It belongs to the field of biochemical engineering. Background Technology

[0002] As people pay more attention to their health, the public is increasingly consuming nutritional supplements, with polyunsaturated fatty acid (PUFA) products playing a significant role. Polyunsaturated fatty acids are fatty acids whose molecular structure contains at least two double bonds, and they exist in forms such as ethyl esters, methyl esters, glycerol esters, and free fatty acids.

[0003] Polyunsaturated fatty acids (PUFAs) are essential building blocks for metabolism, particularly in infant brain development. They are components of cell membranes, primarily functioning to maintain cell membrane fluidity, promote cholesterol esterification, lower cholesterol and triglycerides, reduce blood viscosity, and improve blood circulation. They also play a role in improving cognitive function and enhancing memory. The human body cannot synthesize PUFAs and must obtain them through diet.

[0004] Polyunsaturated fatty acids (PUFAs) are diverse, mainly including ω-3 polyunsaturated fatty acids (PUFAs), ω-6 polyunsaturated fatty acids (PUFAs), and ω-9 polyunsaturated fatty acids (PUFAs), such as α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), linoleic acid (LA), conjugated linoleic acid (CLA), gamma-linolenic acid (GLA), and arachidonic acid (AA). Among them, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the most well-known and accepted ω-3 polyunsaturated fatty acids, and their effects on improving and promoting human and animal health are the most significant. The molecular structures of some polyunsaturated fatty acids are as follows:

[0005]

[0006]

[0007] Polyunsaturated fatty acids are mainly derived from algae extracts and aquatic animal oils, with fish oil being a significant source. Due to the complex fatty acid composition of oils containing saturated, monounsaturated, and polyunsaturated fatty acids, these fatty acids have significantly different melting points. For example, saturated fatty acids such as C16:0, C18:0, and C20:0 solidify at around 10°C or even 20°C, while monounsaturated or diunsaturated fatty acids such as C16:2, C18:1, and C18:2 do not precipitate at 0°C, and polyunsaturated fatty acids such as C16:4, C18:3, C20:4, C20:5, and C22:6 remain clear below -10°C. Solid fats refer to saturated fatty acids such as C16:0, C18:0, and C20:0, and even low-saturation fatty acids such as C16:2, C18:1, and C20:1; these are substances with relatively high melting points.

[0008] Polyunsaturated fatty acids generally have good effects such as softening blood vessels and lowering triglycerides, while saturated fatty acids do not have these physiological functions. Therefore, most polyunsaturated fatty acids, especially functional polyunsaturated fatty acid oils such as fish oil and conjugated linoleic acid, are mainly used in dietary supplements. In the dietary supplement field, these polyunsaturated fatty acids are often taken in the form of transparent soft capsules, and from an appearance perspective, the contents of the soft capsules are required to be as transparent as possible. In the industrial production of polyunsaturated fatty acid-related products, the final product standards all have certain requirements for the clarity of the product, namely, a colorless to light yellow transparent liquid. Therefore, the industrial preparation process of polyunsaturated fatty acid products basically includes a winterization process. The main purpose is to remove the saturated components or the low-saturation components with fewer double bonds, i.e., solid fats, from the polyunsaturated fatty acids, thereby improving their physiological efficacy and maintaining their clarity.

[0009] Although they do not have physiological effects such as softening blood vessels or lowering cholesterol, saturated fatty acids or low-unsaturated fatty acids (containing 1-2 double bonds in their molecular structure) are still useful in supplementing animal fat and providing energy. They can be widely used in the food or animal feed industry, or in other industrial applications.

[0010] In industrial production, especially when preparing polyunsaturated fatty acid raw materials for soft capsules, the polyunsaturated fatty acids are generally winterized to remove saturated and low-saturation fatty acid components. This involves cooling the polyunsaturated fatty acids to 0°C or below and maintaining this temperature for a period of time, allowing fatty acids with a freezing point below 0°C to crystallize out. These crystallized fatty acids (solids) are then removed by filtration. During this process, ensuring sufficient crystallization of saturated or low-saturation components while minimizing the precipitation of polyunsaturated components to guarantee product yield, and effectively separating the crystallized saturated or low-saturation components (solids) from the non-crystallized polyunsaturated fatty acids are crucial operational steps.

[0011] For oils with a high proportion of medium and low carbon chain saturated fatty acid components (such as C12:0, C14:0, and C16:0), these medium and low carbon chain saturated fatty acids have high freezing points and are easy to crystallize and precipitate, resulting in coarser crystals. Therefore, they are easier to crystallize and easier to separate in subsequent crystallization processes. However, for oils with a low proportion of medium- and low-carbon chain saturated fatty acids and only a small amount of medium- and long-carbon chain low-saturated fatty acids (such as C18:1, C19:2, C20:1, C20:2, C21:1, C21:2, etc.), on the one hand, due to the limited number of seed crystals during the cooling crystallization process, a lower required crystallization temperature leads to difficulty in crystallization, slow crystallization, and sometimes even incomplete crystallization, failing to achieve the desired winterization crystallization effect. On the other hand, the subsequent crystallization separation process is more difficult, requiring long-term pressure filtration using plate and frame filters. To dry the filter cake, compressed air or nitrogen is used for prolonged purging. During this process, some crystals in the plate and frame filters dissolve due to the increased temperature and re-enter the unsaturated components, resulting in an unsatisfactory final winterization effect.

[0012] In addition, for these medium- and long-chain fatty acids containing only a small amount of low-saturated fatty acids, on the one hand, the number of crystals produced during winterization is small, and a filter cake with a fixed shape cannot be formed during pressure filtration. On the other hand, because the melting point of the low-saturated components is relatively low, they are easily remelted in the air, which leads to partial melting during plate and frame filtration. This results in incomplete discharge of the filter cake during filtration, with some adhering to the plate and frame filter cloth. This reduces the winterization effect and efficiency. The adhering low-melting-point components are easy to melt and enter the unsaturated fatty component filtrate of the next batch of winterized products, reducing the winterization efficiency. Moreover, the precipitated low-saturated component solids cannot be effectively reused, reducing the economic efficiency of the process.

[0013] In previous technologies, a large number of studies have focused on improving the winterization crystallization efficiency and separation efficiency of polyunsaturated fatty acids through process or equipment innovation.

[0014] CN12552198A discloses a secondary slow-cooling winterization process for fish oil and the filtration equipment used therein. By employing cooling and stirring, static crystal growth, and filtration to remove crystals, the high freezing point fish oil precipitation rate is achieved. The precipitated fish oil crystals are not easily remelted, and a relatively complex custom-designed device is used to separate the crystals. This device has a small filtration area, complex design, and low separation efficiency, particularly difficult for crystallizing and separating low-saturation crystalline components containing only a small amount of relatively low freezing point.

[0015] CN205501251A describes a simple device for winterization of fish oil, which achieves heating and dissolving, cooling and crystallizing, and winterization filtration of fish oil in the same tank. This device has to complete the heating, cooling and filtration processes in one set of equipment, with a small heat exchange area and filtration area, resulting in low efficiency, long operation time and poor practicality in production.

[0016] CN103740462B discloses a method for refining oils, which includes a desaturation process. This involves further heating and dissolving the degummed, deacidified, and deodorized oils in a winterization tank, followed by phased cooling and crystallization. After a prolonged crystal growth period, the oil is filtered through a winterization filter to obtain refined oil free of saturated oils. This process suffers from long crystal growth times, difficult filtration, and low production efficiency.

[0017] CN206529439U discloses a fish oil winterization, fractionation, crystallization, and crystal growth reaction vessel. By bubbling nitrogen gas during the winterization and crystallization process, it solves the problem of odor being difficult to escape during winterization, fractionation, and crystallization, and improves heat transfer efficiency. However, this equipment does not describe the separation process of crystallization and also has the disadvantages of slow separation speed and long separation time.

[0018] CN109897726A discloses a pressing process for extracting tea oil from tea seeds, including preliminary tea seed treatment, pressing, filtration, degumming, dewaxing, and deacidification. In the dewaxing process, a large amount of crystal-promoting and filtering agent is added at once, utilizing activated carbon and perlite to simultaneously promote crystal formation and aid filtration. The large amount of crystal-promoting agent added at once inevitably leads to excessive crystal precipitation. Many fatty acids that should not precipitate at the crystallization temperature are adsorbed onto the crystal-promoting agent, thus significantly reducing the yield of the final product.

[0019] In summary, previous winterization refining technologies for oils and fats had several shortcomings: First, low crystallization efficiency. This was particularly true for raw materials with low saturated fatty acid content, containing only small amounts of low-freezing-point low-saturated fatty acids. Due to the difficulty in crystal precipitation and the scarcity of seed crystals, winterization crystallization efficiency was even lower. Second, low separation efficiency of the precipitated crystals. Fatty acid solids are inherently difficult to separate. If the main components of these solids are low-saturated fatty acids, their low freezing point and small quantity make it difficult to achieve rapid and complete separation of the filtrate and solids during plate and frame filtration or other methods. Moreover, during prolonged separation, some low-freezing-point solids easily redissolve back into the filtrate, reducing the quality of the clarified liquid and winterization efficiency. Third, the large-scale, one-time addition of crystallizing and filter aids significantly reduced the yield of the final product. Fourth, the precipitated solids were not effectively recycled, resulting in poor economic viability. Summary of the Invention

[0020] In view of the shortcomings of previous technologies, it is necessary to find a method that can efficiently winterize and crystallize saturated and low-saturated fatty acids in oils and fats, and achieve efficient separation, and also enable the winterization results and the separated solid fats to be recycled, thereby enhancing economic efficiency.

[0021] To achieve the above objectives, this invention provides a method for efficiently separating solid fats from polyunsaturated fatty acid oils. Specifically, a small amount of inert solid powder is added to the polyunsaturated fatty acid oil before winterization. This small amount of inert solid powder acts as a seed crystal, facilitating the crystallization of saturated or low-saturated components in the oil during cooling and promoting crystal growth during crystal formation, thus overcoming the drawbacks of slow crystal precipitation and long crystal formation time. After crystal formation, a certain amount of inert substance powder is added. This inert solid powder acts as a filter aid during crystal separation, promoting efficient crystal separation and preventing crystals from remelting and entering the filtrate during prolonged filtration, which would reduce the winterization effect and efficiency of the final product. The filter cake obtained after filtration is reheated to dissolve, and then filtered again while hot. The resulting filtrate is the solid fat. The filter cake (inert solid powder) after solid fat separation can be reused.

[0022] The specific operating steps of the method described in this invention are as follows: a) Add a small amount of inert solid powder to the heated and melted polyunsaturated fatty acid oil, and stir evenly. The inert solid powder is selected from one or a mixture of several of activated carbon, activated clay, diatomaceous earth, and perlite; b) Cool and crystallize the polyunsaturated fatty acid oil in step a) to obtain a crystallization liquid; c) Add a certain amount of inert solid powder to the crystallization liquid in step b) and stir evenly to obtain a solid-liquid mixture; d) Filter the solid-liquid mixture in step c) to obtain a clear polyunsaturated fatty acid oil and a filter cake; e) Put the filter cake in step d) back into the reaction vessel and heat to dissolve to obtain a solid-liquid mixture containing inert solid powder; and f) Filter the solid-liquid mixture in step e) to obtain a molten solid fat filtrate and a filter cake containing inert solid powder.

[0023] Here, solid fats refer to the saturated and low-saturated fatty acid components in polyunsaturated fatty acid oils, such as C12:0, C14:0, C16:0, C18:1, C19:2, C20:1, C20:2, C21:1, C21:2, etc. These fatty acids have relatively higher freezing points than polyunsaturated fatty acids.

[0024] In a preferred embodiment of the method of the present invention, the polyunsaturated fatty acid oil is preferably selected from one or more mixtures of fish oil, algal oil, linoleic acid, conjugated linoleic acid, linolenic acid, and arachidonic acid. Preferably, the polyunsaturated fatty acid may exist in the form of methyl ester, ethyl ester, glycerol ester, or free fatty acid.

[0025] In a preferred embodiment of the method of the present invention, preferably, in step a), the melting temperature of the polyunsaturated fatty acid oil is 30-100°C. This ensures that the polyunsaturated fatty acid oil is completely clear and transparent. Preferably, in step a), before crystallization, the amount of inert solid powder added is 0.1-1.0% (w / w) of the mass of the polyunsaturated fatty acid oil.

[0026] In a preferred embodiment of the method of the present invention, preferably, in step b), the cooling crystallization temperature is -10℃ to 5℃. It is also preferred to maintain the temperature for 0.5-3.0 hours to allow crystal growth and form a crystalline liquid. Because a small amount of inert solid powder is present in the molten fatty acid oil, this powder acts as a seed crystal in a certain sense. Therefore, the saturated and unsaturated components (solid fats) in the fatty acid oil easily precipitate in crystalline form, and most of the precipitated solid fats are adsorbed onto the inert solid powder. Due to the presence of the inert powder, crystallization is not only easy to occur, but the crystal growth is also better, resulting in coarser crystals, which is beneficial for subsequent separation processes.

[0027] In a preferred embodiment of the method of the present invention, preferably, in step c), after the crystallization and growth process is completed, a certain proportion of inert solid powder is added to the crystallization liquid and stirred evenly. The amount of inert solid powder added is 0.5-4.0% (w / w) of the mass of the polyunsaturated fatty acid oil.

[0028] The crystallization solution with added inert solid powder is separated into solid and liquid phases using conventional methods such as plate and frame filtration, centrifugal filtration, or vacuum filtration. Due to the filtration-aiding effect of the inert solid material, solid-liquid separation is very easy. Conventional winterization crystallization methods without the addition of inert materials often require more than 10 hours, sometimes even around 24 hours, to achieve solid-liquid separation. In the later stages, large amounts of nitrogen or compressed air are needed to dry the residual liquid and oil in the crystals, resulting in unnecessary waste. Furthermore, during the prolonged filtration or drying process, some of the precipitated crystals remelt and re-enter the filtrate, significantly reducing the effectiveness of winterization crystallization. Using the process disclosed in this invention, the addition of inert solid powder results in coarser crystals that are adsorbed onto the inert powder medium in the early stages. Combined with the filtration-aiding effect of the inert powder, solid-liquid separation is much easier. Studies have shown that, under the same filtration area, the solid-liquid separation time is reduced by more than half compared to conventional methods, generally to around 3 hours. Moreover, only a small amount of nitrogen or compressed air is needed for drying in the later stages to obtain a relatively dry filter cake.

[0029] More importantly, the innovative batch addition of inert solid powder allows for the sufficient precipitation of low-saturation long-chain fatty acids (solid fats) without the precipitation of unwanted polyunsaturated fatty acids due to excessive seed crystals, thus preventing a decrease in the final product yield. Simultaneously, it improves the separation efficiency of solid fats. If a certain amount of inert solid powder is not added later, the inert solid powder added earlier as seed crystals will be insufficient to aid filtration. Conversely, if the inert solid powder is added all at once before cooling and crystallization, the final product yield will be significantly reduced. Therefore, depending on the fatty acid composition of the polyunsaturated fatty acids and the desired final product outcome, the batch addition of inert solid powder in a specific proportion can achieve unexpected results, improving solid fat removal efficiency while ensuring product yield.

[0030] In a preferred embodiment of the method of the present invention, preferably, in step e), the filter cake is re-added to the reaction vessel and heated to dissolve at a temperature of 40-100°C. After melting, the inert medium is dispersed in the molten solid resin.

[0031] The solid fat, containing an inert medium and in a molten state, is then filtered while hot to recover the solid fat from the filtrate. The filter cake serves as an inert medium. The recovered solid fat can be used for food, feed, or other industrial applications. The recovered filter cake, being an inert medium, can be stored under nitrogen and reused for the winterization crystallization of the next batch of fatty acid oils.

[0032] The method of this invention enables efficient separation of saturated and low-saturated fatty acid solids from polyunsaturated fatty acid oils. The process features a short winterization crystallization time, complete crystallization, and easy crystal separation. It avoids the phenomenon in conventional processes where prolonged separation and drying times lead to partial melting and re-entry of solids into the filtrate. This results in a high final product yield, and the winterized polyunsaturated fatty acid oil exhibits excellent clarity, with no crystal precipitation even after 5 hours at 0°C. The inert medium added during the process can be reused, generating no additional solid waste and demonstrating good environmental friendliness. Detailed implementation method:

[0033] The following examples further illustrate the present invention. These examples are only for illustrating the technical solutions of the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] 1500g of ethyl ester-type polyunsaturated fatty acid fish oil raw material (EPA 24.3%, DHA 6.9%, total polyunsaturated fatty acid content 34.2%, orange-red color) was dissolved at 65℃ for 0.5 hours, and then 7.5g of activated clay was added. The mixture was then cooled to winterize and crystallize, with the temperature lowered from 65℃ to -2.5℃ within 30 minutes, and the crystals were kept at this temperature for 20 minutes. Then, 45.0g of activated clay and 15g of activated carbon were added, and the mixture was stirred for another 0.5 hours.

[0036] The crystallization liquid containing activated clay and activated carbon was filtered through a plate and frame filter press. After 5 minutes, no obvious filtrate was visible. The filter cake was dried with nitrogen gas, and after 3 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 1461.2 g, with a yield of 97.3%.

[0037] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0038] After removing the plate and frame filter, the filter cake is in the form of a cake and is relatively dry. The filter cake is heated and stirred in a reaction vessel to 80°C to melt the solid resin. It is then filtered through the plate and frame filter and the filter cake is dried with nitrogen. 27.8g of filtrate (solid resin) is recovered. The filter cake can be reused in the next winterization process.

[0039] Comparative Example 2

[0040] Using the exact same raw materials as in Example 1, the solution was dissolved at 65°C for 0.5 hours. Winterization crystallization was then carried out by slow cooling, with the temperature reduced from 65°C to -2.5°C over 2.5 hours, and crystallization was maintained at this temperature for 2.0 minutes. Crystallization was performed using the plate and frame filter method as in Example 1. The filtration speed was slow; even after 3.0 hours, a small amount of filtrate still flowed out, and the filtrate became turbid later, indicating that a small amount of solid resin had remelted. After 3.5 hours, the plate and frame were removed; the amount of filter cake was small and could not be formed. 20 ml of the filtrate was taken and kept at 0°C for 5 hours; crystals precipitated at the bottom, indicating that the winterization effect was not ideal.

[0041] Comparative Example 3

[0042] Using the same raw materials as in Example 1, the mixture was dissolved at 65°C for 0.5 hours. 52.5g of activated clay and 15g of activated carbon were added, and the mixture was slowly cooled to allow for winterization crystallization. When the temperature was lowered from 65°C to -2.5°C within 2.5 hours, a large amount of crystals precipitated. The mixture was then kept at this temperature for 20 minutes to allow for crystal growth.

[0043] The crystallization liquid containing activated clay and activated carbon was filtered through a plate and frame filter press. After 8 minutes, no obvious filtrate was visible. The filter cake was dried with nitrogen gas, and after 5 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 1297.5 g, with a yield of 86.5%.

[0044] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0045] After removing the plate and frame filter, the filter cake is in the form of a cake and is relatively dry. The filter cake is heated and stirred in a reaction vessel to 80°C to melt the solid resin. It is then filtered through a plate and frame filter and the filter cake is dried with nitrogen. 117.8g of filtrate (solid resin) is recovered.

[0046] It is evident that although the obtained filtrate of 20 ml remained clear and transparent after being kept at 0°C for 5 hours, indicating a good winterization effect, the yield of the final product was relatively low.

[0047] Example 4

[0048] 2000g of triglyceride-type algal oil polyunsaturated fatty acid raw material (EPA 2.9%, DHA 25.3%, total polyunsaturated fatty acid content 30.4%, orange-red color) obtained by fermentation was dissolved at 30℃ for 1.5 hours, and 2g of perlite was added. The mixture was then cooled to winterization crystallization, and the temperature was lowered to -10.0℃ within 45 minutes, and the crystals were kept at this temperature for 30 minutes. 40g of diatomaceous earth was then added, and the mixture was stirred for another 0.5 hours.

[0049] The crystalline liquid containing diatomaceous earth and perlite was filtered using a centrifugal filter. After 6 minutes, no obvious filtrate was observed. The filter cake was dried with nitrogen gas, and after 4 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 1964.0 g, with a yield of 98.2%.

[0050] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0051] Stop the spun filter. The filter cake is cake-shaped and relatively dry. Heat and stir the filter cake in the reaction vessel to 40°C to melt the solid resin. Then filter it through a plate and frame filter and blow the filter cake dry with nitrogen. Recover 20.3g of filtrate (solid resin). The filter cake can be reused in the next winterization process.

[0052] Example 5

[0053] 3000g of free conjugated linoleic acid (69.7% purity) was dissolved at 100℃ for 1.0hr, and then 15g of activated clay and 15g of perlite were added. The mixture was then cooled to winterization crystallization, with the temperature reduced from 100℃ to 5℃ within 60 minutes, and the crystals were kept at this temperature for 45 minutes. Finally, 15g of activated clay and 60g of perlite were added, and the mixture was stirred for another 0.5 hours.

[0054] The crystalline liquid containing activated clay and perlite was filtered using a vacuum filter. After 4 minutes, no obvious filtrate was observed. The filter cake was dried with nitrogen gas, and after 3 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 2889.0 g, with a yield of 96.3%.

[0055] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0056] Stop filtration. The filter cake is cake-shaped and relatively dry. Heat and stir the filter cake in the reaction vessel to 100°C to melt the solid resin. Then filter under vacuum and blow the filter cake dry with nitrogen. Recover 87.4g of filtrate (solid resin). The filter cake can be reused in the next winterization process.

[0057] Example 6

[0058] 2800g of methyl arachidonic acid (58.3% content) was dissolved at 60℃ for 0.5 hours, and 3.0g of activated carbon was added. The mixture was then cooled to winterization crystallization, and the temperature was lowered to 2℃ within 60 minutes, and the crystals were kept at this temperature for 45 minutes. 14g of activated carbon was then added, and the mixture was stirred for another 0.5 hours until homogeneous.

[0059] The crystallizing liquid containing activated carbon was filtered using a vacuum filter. After 3 minutes, no obvious filtrate was observed. The filter cake was dried with nitrogen gas, and after 3 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 2741.2 g, with a yield of 97.9%.

[0060] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0061] Stop filtration. The filter cake is cake-shaped and relatively dry. Heat and stir the filter cake in the reaction vessel to 60°C to melt the solid resin. Then filter it under vacuum and blow the filter cake dry with nitrogen. Recover 35.4g of filtrate (solid resin). The filter cake can be reused in the next winterization process.

[0062] Example 7

[0063] 3500g of a mixture of triglyceride-type linolenic acid and linoleic acid (linolenic acid content 10.7%, linoleic acid content 35.6%) was dissolved at 80℃ for 0.45 hours, and then 10g of diatomaceous earth was added. The mixture was then cooled to winterization crystallization, and the temperature was lowered to -2.5℃ within 45 minutes, and the crystals were kept at this temperature for 45 minutes. Then, 45g of activated clay and 60g of perlite were added, and the mixture was stirred for another 0.5 hours until homogeneous.

[0064] The crystallized liquid containing diatomaceous earth, activated clay, and perlite was filtered through a filter press. After 5 minutes, no obvious filtrate was observed. The filter cake was dried with nitrogen gas, and after 4 minutes, no filtrate droplets flowed out. The filtrate was collected and weighed to be 3384.5 g, with a yield of 96.7%.

[0065] Take 20 ml of the filtrate and keep it at 0℃ for 5 hours. If it remains clear and transparent, it indicates that the winterization effect is very good.

[0066] Stop filtration. The filter cake is cake-shaped and relatively dry. Heat and stir the filter cake in the reaction vessel to 100°C to melt the solid resin. Then filter by pressure and blow the filter cake dry with nitrogen. Recover 48.9g of filtrate (solid resin). The filter cake can be reused in the next winterization process.

[0067] It should be stated that the above-described invention content and specific embodiments are intended to demonstrate the practical application of the technical solution provided by this invention and should not be construed as limiting the scope of protection of this invention. Those skilled in the art can make various modifications, equivalent substitutions, or improvements within the spirit and principles of this invention.

Claims

1. A method for efficiently separating solid fats from polyunsaturated fatty acid oils, the method comprising the following steps: a) Add a small amount of inert solid powder to the heated and melted polyunsaturated fatty acid oil and stir evenly. The inert solid powder is selected from one or a mixture of several of activated carbon, activated clay, diatomaceous earth, and perlite. The polyunsaturated fatty acid oil is selected from one or a mixture of fish oil, algal oil, linoleic acid, conjugated linoleic acid, linolenic acid, and arachidonic acid. Before crystallization, the amount of inert solid powder added is 0.1-1.0% (w / w) of the mass of the polyunsaturated fatty acid oil. b) The polyunsaturated fatty acid oil in which a small amount of the inert solid powder was added in step a) is cooled and crystallized at a temperature of -10℃ to 5℃ to obtain a crystallized liquid. c) Add a certain amount of the inert solid powder to the crystallization liquid in step b), and stir evenly to obtain a solid-liquid mixture; d) Filter the solid-liquid mixture from step c) to obtain a clear polyunsaturated fatty acid oil and filter cake; e) The filter cake from step d) is returned to the reactor and heated to dissolve, yielding a solid-liquid mixture containing inert solid powder; and f) Filter the solid-liquid mixture from step e) to obtain a molten solid filtrate and a filter cake containing inert solid powder.

2. The method as described in claim 1, wherein, The polyunsaturated fatty acids exist in the form of methyl esters, ethyl esters, glycerides, or free fatty acids.

3. The method as described in claim 1, wherein, In step a), the melting temperature of the polyunsaturated fatty acid oil is 30-100℃.

4. The method of claim 1, wherein, In step c), after crystallization, the amount of the inert solid powder added is 0.5-4.0% (w / w) of the mass of the polyunsaturated fatty acid oil.

5. The method of claim 1, wherein, In step e), the filter cake is returned to the reactor and heated to dissolve at a temperature of 40-100°C.

6. The method of claim 1, wherein, In steps d) and f), the filtration method is plate and frame filtration, centrifugal filtration or vacuum filtration.

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