Preparation method and application of medium-chain and long-chain fatty acid triglyceride

Abstract

The invention belongs to the technical field of functional grease preparation, and discloses a preparation method and application of medium-chain and long-chain fatty acid triglyceride. The preparation method comprises the following steps: taking mixed vegetable oil; adding water and heating to obtain an oil-water mixture; filling the immobilized lipase into a glass column with external circulating water heating for preheating; injecting the oil-water mixture from the upper part of the immobilized enzyme column to carry out enzyme hydrolysis reaction; collecting a hydrolyzed oil crude product, and separating free fatty acid; taking medium chain triglyceride, mixing, and injecting into the immobilized enzyme column for esterification reaction; and removing reaction by-products to obtain the medium and long chain fatty acid triglyceride rich in omega-3 / 6 / 9 equilibrium proportion. The product prepared by the method contains medium-chain fatty acid and long-chain fatty acid at the same time, the proportion of different fatty acids is more balanced, the health requirement of a human body on fatty acid intake is met, the immobilized enzyme column technology is used in a solvent-free system, the steps of lipase and oil separation are simplified, the service life of enzyme is remarkably prolonged, and the method is suitable for industrial production. The energy consumption and pollution emission are reduced, the production cost is reduced, and the modern industrial green development concept is met.

Description

Technical Field

[0001] This invention relates to the field of functional oil preparation technology, specifically to a method for preparing and applying medium- and long-chain fatty acid triglycerides. Background Technology

[0002] While oils and fats have wide applications in the food and industrial sectors, their natural triglyceride structure often limits their technical properties in certain specific applications. Medium- and long-chain fatty acid triglycerides are mixed triglycerides composed of medium-chain fatty acids (C6-C12) and long-chain fatty acids (C14 and above) combined with glycerol. Chemically, medium-chain fatty acids belong to saturated fatty acids, commonly including caprylic acid (C8:0), capric acid (C10:0), and lauric acid (C12:0). These fatty acids are characterized by rapid digestion and absorption and quick energy supply. Long-chain fatty acids are mostly ω-3, ω-6, and ω-9 unsaturated fatty acids, encompassing α-linolenic acid (C18:3), linoleic acid (C18:2), and oleic acid (C18:1), among others. Due to their unique structural characteristics, medium- and long-chain fatty acid triglycerides have shown broad application prospects in various fields such as nutrition and health, weight loss, sports supplementation, and medicine.

[0003] In existing technologies, the preparation of medium- and long-chain fatty acid triglycerides typically involves chemical and enzymatic methods, such as:

[0004] (1) Acid / Alcohololysis: Patent document CN111838676A uses lauric acid and palm stearin as substrates and a sn-1,3 position specific lipase as a catalyst for acidolysis. However, this method only targets the insertion site of a specific medium-chain fatty acid (lauric acid), while ignoring other medium-chain fatty acids (such as caprylic acid and capric acid). In addition, the synthesized product lacks ω-3, ω-6, ω-9 unsaturated fatty acids, so long-term intake cannot meet the body's needs for essential fatty acids; Patent document CN118516418A uses a dual imprinting of fatty acids and nonionic surfactants, and requires the use of high-concentration organic solvents (isopropanol concentration exceeding 70%). In industrial production, to remove these high-concentration organic solvents, corresponding equipment must be provided, which not only significantly increases production costs, but also places higher demands on the entire production process and its supporting facilities. Furthermore, this patent focuses only on the enrichment of ω-3 polyunsaturated fatty acids, while neglecting the content of ω-6 and ω-9 unsaturated fatty acids. Patent document CN105104583A describes a process where edible oil and medium-chain fatty acids are vacuum dehydrated, then a catalyst is added, and the reaction is carried out under nitrogen protection; subsequently, an alkane solvent is added to produce medium- and long-chain fatty acid oils. However, this process requires sophisticated equipment and is complex for industrial production, making it unsuitable for large-scale production.

[0005] (2) Transesterification reaction: Patent document CN 105087694A discloses a method for preparing medium- and long-chain triglycerides using a packed bed reactor. Through a simple transesterification reaction and subsequent ethanol extraction, a product containing no less than 75% medium- and long-chain fatty acid triglycerides is stably prepared. However, this method still relies on ethanol purification in the subsequent purification process, which increases the requirements for equipment and plant facilities. Patent document CN110885861A discloses a method for synthesizing medium- and long-chain triglycerides in a reverse micelle enzyme system. However, the reverse micelle system prepared in the early stage of this method is relatively complex and not conducive to industrial application. When purifying the final product, a large amount of water needs to be added and centrifuged, which not only generates a large amount of wastewater, but also the conditions such as centrifugation are not feasible in large-scale production. Patent document CN116376991A uses a co-solvent composed of choline chloride-urea, betaine-urea-water, betaine-lactic acid, or betaine-glucose-water to significantly improve the synthesis rate of medium- and long-chain fatty acid triglycerides through transesterification reaction. However, the products synthesized by this method have a relatively limited variety of unsaturated fatty acids and do not address the issue of a balanced fatty acid ratio in the synthesized products. Patent document CN109666541A utilizes lipase to graft long-chain fatty acid oils, separates and purifies them to remove some saturated fatty acids, and obtains medium- and long-chain fatty acid triglycerides through transesterification. However, the preparation process involves excessively long reaction times and high energy consumption, which is not conducive to industrial application.

[0006] (3) Esterification reaction: Patent document CN104988190A uses high-purity medium-chain fatty acids / esters, long-chain fatty acids / esters and glycerol as raw materials to prepare medium and long-chain fatty acid triglycerides through esterification reaction. However, this method has a high raw material cost and is not suitable for large-scale use; moreover, chemical catalysts (such as sulfuric acid, phosphoric acid, etc.) or solid acid catalysts are used in the preparation process, which makes the production process insufficient in terms of environmental protection and energy saving.

[0007] (4) Two-step method: Patent document CN112280810A uses alcoholysis to obtain glycerides rich in polyunsaturated fatty acids, and then uses esterification to react with medium-chain fatty acids, and finally obtains medium- and long-chain triglycerides after purification. However, this method only focuses on the content of polyunsaturated fatty acids in the final product, and does not consider the balance between polyunsaturated fatty acids (the ratio of ω-3 to ω-6) and the ratio with monounsaturated fatty acids in a more detailed way. In addition, an organic solvent (ethanol) is used and a traditional reaction vessel stirring method is adopted, which may have a certain impact on the lifespan of lipase. Patent document CN 111378701A obtains monoglycerides with a specific structure at the sn-2 position through enzymatic alcoholysis, and then obtains high-concentration monoglycerides rich in polyunsaturated fatty acids at the sn-2 position through solvent crystallization and extraction processes. This process is complicated and has a low extraction rate, which can easily cause a large loss of raw materials. Next, the purified sn-2 position fatty acid is esterified with high-purity medium-chain fatty acid, and then purified and extracted to obtain a medium-to-long-chain triglyceride with a specific structure (MLM type). The entire process is complex and cumbersome, and each step may result in raw material loss, leading to high production costs and making it unsuitable for large-scale production and widespread use.

[0008] (5) Other methods: Based on the physiological characteristics of newborns and the composition of colostrum, patent documents CN 109907126 A and CN 112219902 A further subdivided the relative content range of fatty acids in medium and long chain fatty acid edible oils and the distribution of fatty acids on the glycerol skeleton, which focused more on simulating breast milk and had limited application areas.

[0009] In summary, while acid / alcohololysis can pinpoint fatty acid insertion sites, it cannot simultaneously account for the types and ratios of medium-chain and long-chain fatty acids, and lacks ω-3 / 6 / 9 fatty acids, making it difficult to meet the body's long-term needs. Transesterification, although shortening reaction time, is complex, consumes significant amounts of wastewater and solvents, and is difficult to scale up for green production. Esterification, due to the use of chemical catalysts, suffers from high costs and low environmental friendliness, making it unsuitable for large-scale production. The current market demand for triglycerides containing both medium-chain fatty acids (for rapid energy supply) and long-chain unsaturated fatty acids (for nutritional health) is increasing, especially for fatty acid mixtures in specific balanced ratios (such as the ω-3 / ω-6 ratio), which current technologies cannot efficiently meet. Solvent use, wastewater discharge, and high-temperature reactions also put pressure on the environment during production.

[0010] Therefore, given the numerous problems existing in the preparation technology of medium and long chain fatty acid triglycerides in terms of production efficiency, product quality, environmental friendliness, and process complexity, there is an urgent need for innovative technologies to break through these limitations and develop green, efficient, and energy-saving new technologies for widespread application in the health, medical, and food fields. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying medium- and long-chain fatty acid triglycerides.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] In a first aspect, the present invention provides a method for preparing medium- and long-chain fatty acid triglycerides, comprising the following steps:

[0014] (1) Take a mixed vegetable oil; the mixed vegetable oil includes 20%-30% flaxseed oil by weight;

[0015] (2) Add water to the mixed oil and heat at 50℃-65℃ to obtain an oil-water mixture;

[0016] (3) Fill the immobilized lipase into a glass column heated by external circulating water and preheat the immobilized enzyme column;

[0017] (4) The oil-water mixture is injected from the top of the immobilized enzyme column at a flow rate of 3 mL / min-6 mL / min to carry out the enzymatic hydrolysis reaction; the crude hydrolyzed oil product is collected and the free fatty acids are separated.

[0018] (5) Take the free fatty acid and medium-chain triglyceride and mix them in a molar ratio of 1:2-4. Inject the resulting mixture into the immobilized enzyme column from top to bottom to carry out the esterification reaction.

[0019] (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, remove the by-products therein, and obtain medium- and long-chain fatty acid triglycerides rich in a balanced ratio of ω-3 / 6 / 9.

[0020] This invention provides a solvent-free method for preparing medium- and long-chain fatty acid triglycerides based on immobilized enzyme column technology. This method efficiently prepares functional triglycerides rich in a balanced ratio of medium- and long-chain fatty acids and ω-3 / 6 / 9 unsaturated fatty acids, resulting in a more balanced variety and ratio of medium- and long-chain fatty acids. Specifically, it includes:

[0021] a. Employing immobilized enzyme column technology: Immobilized enzyme columns can operate continuously, significantly extending enzyme lifespan, improving reaction efficiency, and reducing unit production costs. By precisely controlling reaction conditions, specific fatty acids (medium-chain and long-chain, saturated and unsaturated) can be directionally inserted into glycerol molecules, producing medium- and long-chain fatty acid triglycerides that are both functional and nutritional.

[0022] b. Balanced fatty acid ratio: The technical design emphasizes the ratio of ω-3 / 6 / 9 fatty acids and the high content of medium-chain fatty acids to meet the human body's health needs for a balanced intake of fatty acids and provide high-quality lipid raw materials for the nutrition and medical fields.

[0023] c. Green and environmentally friendly process: Low-temperature reaction and non-toxic solvent design reduce energy consumption and pollution emissions, conforming to the modern industrial green development concept. The simplified process facilitates large-scale production and reduces industrialization costs.

[0024] This invention not only overcomes the shortcomings of existing methods but also promotes the industrial application of medium- and long-chain fatty acid triglycerides, providing innovative products for the functional food, pharmaceutical, and sports nutrition markets. Furthermore, its environmentally friendly and energy-saving process advantages align with global sustainable development goals.

[0025] In a preferred embodiment of the method for preparing medium- and long-chain fatty acid triglycerides according to the present invention, in step (1), the mixed vegetable oil further includes at least two of soybean oil, corn oil, peanut oil, rapeseed oil, camellia seed oil, and maple seed oil.

[0026] In a preferred embodiment of the method for preparing medium- and long-chain fatty acid triglycerides according to the present invention, in step (3), the lipase is at least one of immobilized lipase Lipozyme TL IM, immobilized lipase RM IM, and immobilized lipase Lipozyme 435; the amount of lipase added is 2%-5% of the mass of the mixed vegetable oil; the preheating temperature is 50℃-65℃ and the time is 1h-2h.

[0027] In a preferred embodiment of the method for preparing medium- and long-chain fatty acid triglycerides according to the present invention, in step (4), the circulating water temperature of the immobilized enzyme column is set to 40℃-70℃, and the circulation reaction is carried out for 3h-8h; the separation is performed using molecular distillation, with an evaporation temperature of 150℃-200℃ and a vacuum degree of less than 10Pa. More preferably, the evaporation temperature is 180℃-190℃, and the vacuum degree is 6Pa-8Pa.

[0028] In a preferred embodiment of the method for preparing medium- and long-chain fatty acid triglycerides according to the present invention, in step (5), the flow rate of the top-down injection is 3 mL / min-6 mL / min.

[0029] As a preferred embodiment of the method for preparing medium- and long-chain fatty acid triglycerides according to the present invention, in step (6), the removal of byproducts is carried out by molecular distillation, with an evaporation temperature of 180℃-190℃ and a vacuum degree of 6Pa-8Pa.

[0030] Secondly, the present invention provides a medium- and long-chain fatty acid triglyceride, which is prepared by the method for preparing medium- and long-chain fatty acid triglycerides.

[0031] Thirdly, the present invention provides a nutritional preparation, characterized in that it comprises the aforementioned medium- and long-chain fatty acid triglycerides.

[0032] Fourthly, the present invention applies the preparation method of the medium- and long-chain fatty acid triglycerides, the medium- and long-chain fatty acid triglycerides, and the nutritional preparations to functional foods, pharmaceutical preparations, and sports nutrition products.

[0033] Compared with existing technologies, this invention prepares medium- and long-chain fatty acid triglycerides (MLCTs) in a solvent-free system by combining enzymatic hydrolysis and enzymatic transesterification, and employing a synergistic immobilized enzyme column system. The beneficial effects of this invention are as follows:

[0034] 1. Efficiency and economy

[0035] The enzymatic process employed in this invention significantly reduces enzyme usage to only 2%-5%, far lower than that of traditional processes, thus substantially reducing production costs. Simultaneously, the reaction temperature is relatively mild, controlled between 50℃ and 65℃, reducing energy consumption and aligning with the trend towards green chemistry.

[0036] 2. High product purity

[0037] By optimizing the synergistic effect of enzymatic hydrolysis and transesterification, the medium- and long-chain fatty acid triglycerides (MLCT) prepared by this invention can reach a content of 76.7%, and the content of medium-chain fatty acids in the product can reach 35.5%.

[0038] 3. Balanced fatty acid ratio

[0039] This invention achieves an ideal ratio of ω-3 / 6 / 9 unsaturated fatty acids in the product by controlling the combination of different raw oils and process conditions, thus meeting the human body's balanced needs for essential fatty acids. Simultaneously, the near-equilibrium ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids (1:1:1) significantly enhances the nutritional value and functionality of the final product.

[0040] 4. Strong process adaptability

[0041] This invention synthesizes medium- and long-chain triglycerides (MLCTs) with specific fatty acid compositions by selecting the type of enzyme and process conditions based on the feedstock oil. Different feedstock oils can be efficiently synthesized under the process conditions of this invention, demonstrating the wide applicability of this technology.

[0042] 5. Environmentally friendly

[0043] Because it uses a solvent-free system, this invention avoids the use of organic solvents, reduces environmental pollution, and simplifies subsequent separation and purification steps, thus meeting the requirements of sustainable development.

[0044] In summary, the method of this invention achieves balanced enrichment and transesterification of fatty acids under low-temperature conditions, preserving the functional activity and balanced ratio of ω-3 / 6 / 9 unsaturated fatty acids while increasing the content of medium- and long-chain fatty acids. Furthermore, the use of immobilized enzyme column technology in a solvent-free system simplifies the steps of lipase and oil separation, significantly extends enzyme lifespan, reduces energy consumption and pollution emissions, lowers production costs, and is simple, environmentally friendly, efficient, and suitable for large-scale industrial production, aligning with the modern industrial green development concept. Detailed Implementation

[0045] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified. Lipozyme Calb B, Lipozyme TL100L, Lipozyme 435, Lipozyme RM IM, Lipozyme TL IM, Palatase2000, and Eversa Transform were purchased from Novozymes; the detection of medium-chain triglycerides, long-chain fatty acid triglycerides, and medium- and long-chain fatty acid triglycerides was performed according to Q / HT0088S-2024; the detection of fatty acids was performed according to GB 5009.168.

[0047] Example 1: A method for preparing medium- and long-chain fatty acid triglycerides

[0048] (1) Mix flaxseed oil, corn oil and rapeseed oil in a mass ratio of 3:4:3 until the total amount is 1kg to obtain mixed oil;

[0049] (2) Add 0.4 kg of distilled water to the mixed oil, place it in a substrate container, and heat it at 50°C to obtain an oil-water mixture;

[0050] (3) Fill 40g of immobilized lipase RM IM into a glass column heated with external circulating water, preheat the immobilized enzyme column for 1 hour to ensure that the enzyme activity reaches the optimal state.

[0051] (4) The preheated oil-water mixture was injected into the top of the immobilized enzyme column at a flow rate of 3 mL / min using a peristaltic pump to carry out the enzymatic hydrolysis reaction; the circulating water temperature of the immobilized enzyme column was set to 50℃, and the circulation reaction was carried out for 6 hours. After the reaction was completed, the crude hydrolyzed oil product was collected, and the free fatty acids were separated by molecular distillation (evaporation temperature 180℃, vacuum degree 8Pa);

[0052] (5) The separated free fatty acids and medium-chain triglycerides were mixed at a molar ratio of 1:2.5, and the mixture was injected into the immobilized enzyme column from top to bottom at a flow rate of 3 mL / min using a peristaltic pump to carry out the esterification reaction.

[0053] (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, and remove byproducts such as free fatty acids in the crude product by molecular distillation (evaporation temperature 180℃, vacuum degree 8Pa) to obtain the final product.

[0054] The final product contains 6.2% medium-chain triglycerides, 75.3% medium- and long-chain triglycerides, 18.5% long-chain triglycerides, and 34.5% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids is 1:2:1.8, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids is 2:1:1.8. The high content of medium-chain fatty acids and the even distribution of each fatty acid significantly enhance the product's nutritional value and functionality.

[0055] Example 2: A method for preparing medium- and long-chain fatty acid triglycerides

[0056] (1) Mix flaxseed oil, soybean oil and rapeseed oil evenly in a mass ratio of 2.5:5.5:2, with a total volume of 1 kg, to obtain mixed oil;

[0057] (2) Add 0.5 kg of distilled water to the mixed oil, place it in a substrate container, and heat it at 55°C to obtain an oil-water mixture;

[0058] (3) Fill 50g of immobilized lipase TLIM into a glass column with external circulating water heating, and preheat the immobilized enzyme column for 1.5 hours to ensure that the enzyme activity reaches the optimal state.

[0059] (4) The preheated oil-water mixture was injected into the top of the immobilized enzyme column at a flow rate of 4 mL / min using a peristaltic pump to carry out the enzymatic hydrolysis reaction; the circulating water temperature of the immobilized enzyme column was set to 55℃, and the circulation reaction was carried out for 8 hours. After the reaction was completed, the crude hydrolysate was collected, and the free fatty acids were separated by molecular distillation (evaporation temperature 185℃, vacuum degree 6.5Pa);

[0060] (5) The separated free fatty acids and medium-chain triglycerides were mixed at a molar ratio of 1:2.8, and the mixture was injected into the immobilized enzyme column from top to bottom at a flow rate of 4 mL / min using a peristaltic pump to carry out the esterification reaction.

[0061] (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, and remove byproducts such as free fatty acids in the crude product by molecular distillation (evaporation temperature 185℃, vacuum degree 6.5Pa) to obtain the final product.

[0062] The final product contains 5.6% medium-chain triglycerides, 76.7% medium- and long-chain triglycerides, 17.7% long-chain triglycerides, and 35.1% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids is 1:2.1:1.5, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids is 2.4:1:2.2. The high content of medium-chain fatty acids and the even distribution of each fatty acid significantly enhance the product's nutritional value and functionality.

[0063] Example 3: A method for preparing medium- and long-chain fatty acid triglycerides

[0064] (1) Mix flaxseed oil, maple seed oil and camellia seed oil in a mass ratio of 2.5:6.5:2 until the total amount is 1 kg to obtain mixed oil;

[0065] (2) Add 0.6 kg of distilled water to the mixed oil, place it in a substrate container, and heat it at 60°C to obtain an oil-water mixture;

[0066] (3) Fill 30g of immobilized lipase Novozym 435 into a glass column heated with external circulating water, and preheat the immobilized enzyme column for 2 hours to ensure that the enzyme activity reaches the optimal state.

[0067] (4) The preheated oil-water mixture was injected into the top of the immobilized enzyme column at a flow rate of 5 mL / min using a peristaltic pump to carry out the enzymatic hydrolysis reaction; the circulating water temperature of the immobilized enzyme column was set to 60℃, and the circulation reaction was carried out for 4 hours. After the reaction was completed, the crude hydrolysate was collected, and the free fatty acids were separated by molecular distillation (evaporation temperature 190℃, vacuum degree 7Pa);

[0068] (5) The separated free fatty acids and medium-chain triglycerides were mixed in a molar ratio of 1:3. The mixture was injected into the immobilized enzyme column from top to bottom using a peristaltic pump at a flow rate of 5 mL / min to carry out the esterification reaction.

[0069] (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, and remove byproducts such as free fatty acids in the crude product by molecular distillation (evaporation temperature 190℃, vacuum degree 7Pa) to obtain the final product.

[0070] The final product contains 4.9% medium-chain triglycerides, 76.3% medium- and long-chain triglycerides, 18.8% long-chain triglycerides, and 35.5% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids is 1:2.1:2.9, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids is 1.4:1:1. The high content of medium-chain fatty acids and the even distribution of each fatty acid significantly enhance the product's nutritional value and functionality.

[0071] Example 4: A method for preparing medium- and long-chain fatty acid triglycerides

[0072] (1) Mix flaxseed oil, peanut oil and camellia seed oil in a mass ratio of 2:5.5:2.5 until they are evenly mixed, with a total volume of 1 kg, to obtain mixed oil;

[0073] (2) Add 0.8 kg of distilled water to the mixed oil, place it in a substrate container, and heat it at 65°C to obtain an oil-water mixture;

[0074] (3) Fill 20g of immobilized lipase RM IM and Novozym 435 in a mass ratio of 1:1 into a glass column heated with external circulating water, and preheat the immobilized enzyme column for 2 hours to ensure that the enzyme activity reaches the optimal state.

[0075] (4) The preheated oil-water mixture was injected into the top of the immobilized enzyme column at a flow rate of 6 mL / min using a peristaltic pump to carry out the enzymatic hydrolysis reaction; the circulating water temperature of the immobilized enzyme column was set to 65℃, and the circulation reaction was carried out for 3 hours. After the reaction was completed, the crude hydrolysate was collected, and the free fatty acids were separated by molecular distillation (evaporation temperature 185℃, vacuum degree 8Pa);

[0076] (5) The separated free fatty acids and medium-chain triglycerides were mixed at a molar ratio of 1:3.2, and the mixture was injected into the immobilized enzyme column from top to bottom at a flow rate of 6 mL / min using a peristaltic pump to carry out the esterification reaction.

[0077] (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, and remove byproducts such as free fatty acids in the crude product by molecular distillation (evaporation temperature 185℃, vacuum degree 8Pa) to obtain the final product.

[0078] The final product contains 5.3% medium-chain triglycerides, 76.1% medium- and long-chain triglycerides, 18.6% long-chain triglycerides, and 35.3% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids is 1:2:3.4, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids is 1.7:1.2:1. The high content of medium-chain fatty acids and the even distribution of each fatty acid significantly enhance the product's nutritional value and functionality.

[0079] The fatty acid distribution of the final products in Examples 1-4 above is shown in Table 1:

[0080] Table 1 Fatty acid content

[0081]

[0082]

[0083] Comparative Example 1: A method for preparing medium- and long-chain fatty acid triglycerides

[0084] Compared with Example 1, the only difference is that the mass ratio of flaxseed oil, corn oil and rapeseed oil is 1:4:3.

[0085] The final product contained 8.3% medium-chain triglycerides, 62.5% medium- and long-chain triglycerides, 29.2% long-chain triglycerides, and 34.12% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:6.7:4.4, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.5:0.9. Compared with Example 1, the final product had a lower content of medium- and long-chain triglycerides, and the distribution of fatty acids was unbalanced, significantly deviating from the optimal range. This resulted in a significant decrease in the nutritional value and functionality of the product, indicating a poor synthesis effect.

[0086] Comparative Example 2: A method for preparing medium- and long-chain fatty acid triglycerides

[0087] Compared with Example 1, the only difference is that the mass ratio of flaxseed oil, corn oil, and rapeseed oil is 5:4:3.

[0088] The final product contained 7.3% medium-chain triglycerides, 61.5% medium- and long-chain triglycerides, 31.2% long-chain triglycerides, and 34% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:6.2:4, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.5:0.9. Compared with Example 1, the final product had a lower content of medium- and long-chain triglycerides, and the distribution of fatty acids was unbalanced, significantly deviating from the optimal range. This resulted in a significant decrease in the nutritional value and functionality of the product, indicating a poor synthesis effect.

[0089] Comparative Example 3: A method for preparing medium- and long-chain fatty acid triglycerides

[0090] Compared with Example 2, the only difference is that the molar ratio of free fatty acids to medium-chain triglycerides is 1:1.5.

[0091] The final product contained 4.9% medium-chain triglycerides, 53.4% ​​medium- and long-chain triglycerides, 41.7% long-chain triglycerides, and 25% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2.3:1.9, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.7:1.3. Compared with Example 2, the addition of medium-chain triglycerides with a molar ratio of 1:1.5 to free fatty acids resulted in insufficient substrate for the esterification reaction. The reaction equilibrium could not effectively advance towards esterification, leading to a low degree of esterification, a significant decrease in the proportion of long-chain lipids in the target product, more byproduct residues, and poor synthesis results.

[0092] Comparative Example 4: A method for preparing medium- and long-chain fatty acid triglycerides

[0093] Compared with Example 2, the only difference is that the molar ratio of free fatty acids to medium-chain triglycerides is 1:4.5.

[0094] In the final product, the content of medium-chain triglycerides was 21.3%, medium- and long-chain triglycerides were 60.8%, long-chain triglycerides were 17.9%, medium-chain fatty acids were 42.2%, the ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2.5:1.5, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.3:0.7. Compared with Example 2, although the addition of medium-chain triglycerides with a molar ratio of 1:4.5 to free fatty acids could promote the esterification reaction, it also resulted in excessive unreacted medium-chain triglycerides remaining, leading to an imbalance in the composition ratio of the structural lipids in the final product, with medium-chain fatty acids reaching 42.2%, affecting the functional properties and stability of the final product, and resulting in poor synthesis effect.

[0095] Comparative Example 5: A method for preparing medium- and long-chain fatty acid triglycerides

[0096] Compared with Example 3, the only difference is that the flow rate of both the enzymatic hydrolysis and esterification reaction stages was adjusted to 1 mL / min.

[0097] In the final product, the content of medium-chain triglycerides was 21.3%, medium- and long-chain triglycerides were 45.9%, long-chain triglycerides were 32.8%, medium-chain fatty acids were 38.2%, the ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2.3:2.9, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.6:0.7. Compared with Example 3, although the final distribution ratio of each fatty acid was not significantly different, the low flow rate and long residence time of the material in the enzyme column led to local enzyme saturation, a shift in reaction equilibrium towards hydrolysis, significant side reactions, and decreased enzyme loading efficiency, which affected the enrichment of the target product, resulting in slower synthesis efficiency and higher synthesis costs.

[0098] Comparative Example 6: A method for preparing medium- and long-chain fatty acid triglycerides

[0099] Compared with Example 3, the only difference is that the flow rate of both the enzymatic hydrolysis and esterification reaction stages was adjusted to 15 mL / min.

[0100] In the final product, the content of medium-chain triglycerides was 12.8%, medium- and long-chain triglycerides was 49.6%, long-chain triglycerides was 37.6%, medium-chain fatty acids were 32.5%, the ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2.2:2.9, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.8:0.9. Compared with Example 3, although the final distribution ratio of each fatty acid was not significantly different, the contact time between the material and the enzyme was significantly insufficient due to the excessively high flow rate, resulting in incomplete reaction, low esterification degree, low synthesis rate of medium- and long-chain triglycerides, high residual fatty acid content in the product, deviation of the structural lipid composition from the design target, rough oil texture, and slightly greasy flavor.

[0101] Comparative Example 7: A method for preparing medium- and long-chain fatty acid triglycerides

[0102] Compared with Example 4, the only difference is that the oil-water mixture is heated to 40°C, the circulating water temperature of the immobilized enzyme column is also set to 40°C, and the hydrolysis and esterification reaction temperatures are both reduced to 40°C.

[0103] In the final product, the content of medium-chain triglycerides was 19.2%, medium- and long-chain triglycerides were 43.2%, long-chain triglycerides were 37.6%, medium-chain fatty acids were 37.3%, the ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2:3.2, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.6:0.6. Compared with Example 4, although the distribution ratio of each fatty acid was not significantly different, the reaction temperature was too low, the lipase activity was low, the composition ratio of each ester structure in the product deviated from the target ratio, the esterification efficiency was low, and the optimal synthesis effect could not be achieved.

[0104] Comparative Example 8: A method for preparing medium- and long-chain fatty acid triglycerides

[0105] Compared with Example 4, the only difference is that the oil-water mixture is heated to 80°C, the circulating water temperature of the immobilized enzyme column is also set to 80°C, and the hydrolysis and esterification reaction temperatures are both reduced to 80°C.

[0106] The final product contained 15.3% medium-chain triglycerides, 41.5% medium- and long-chain triglycerides, 43.2% long-chain triglycerides, and 36.2% medium-chain fatty acids. The ratio of ω-3 / 6 / 9 unsaturated fatty acids was 1:2.1:3.8, and the ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids was 1:0.7:0.6. Compared with Example 4, although the distribution ratio of each fatty acid was not significantly different, the enzyme activity decreased sharply in the later stage of the enzyme column reaction due to the excessively high reaction temperature, and some enzymes may have been thermally inactivated. The final product had a low degree of esterification, increased by-products, a slightly darker color, and a slightly burnt and bitter flavor.

[0107] The fatty acid distribution of the final products of Comparative Examples 1-8 above is shown in Table 2:

[0108] Table 3 Fatty acid content

[0109]

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing medium- and long-chain fatty acid triglycerides, characterized in that, Includes the following steps: (1) Take a mixed vegetable oil; the mixed vegetable oil includes 20%-30% flaxseed oil by weight; (2) Add water to the mixed oil and heat at 50℃-65℃ to obtain an oil-water mixture; (3) Fill the immobilized lipase into a glass column heated by external circulating water and preheat the immobilized enzyme column; (4) The oil-water mixture is injected from the top of the immobilized enzyme column at a flow rate of 3 mL / min-6 mL / min to carry out the enzymatic hydrolysis reaction; the crude hydrolyzed oil product is collected and the free fatty acids are separated. (5) Take the free fatty acid and medium-chain triglyceride and mix them in a molar ratio of 1:2-4. Inject the resulting mixture into the immobilized enzyme column from top to bottom to carry out the esterification reaction. (6) Collect the crude product of medium- and long-chain fatty acid triglycerides flowing out from the bottom of the immobilized enzyme column, remove the by-products therein, and obtain medium- and long-chain fatty acid triglycerides rich in a balanced ratio of ω-3 / 6 / 9.

2. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (1), the mixed vegetable oil also includes at least two of soybean oil, corn oil, peanut oil, rapeseed oil, camellia seed oil, and maple seed oil.

3. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (3), the lipase is at least one of immobilized lipase Lipozyme TL IM, immobilized lipase RM IM, and immobilized lipase Lipozyme 435; the amount of lipase added is 2%-5% of the mass of the mixed vegetable oil.

4. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (3), the preheating temperature is 50℃-65℃ and the time is 1h-2h.

5. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (4), the circulating water temperature of the immobilized enzyme column is set to 40℃-70℃, and the circulation reaction is carried out for 3h-8h; the separation is carried out by molecular distillation, with an evaporation temperature of 150℃-200℃ and a vacuum degree of less than 10Pa.

6. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (5), the flow rate of the top-down injection is 3 mL / min-6 mL / min.

7. The method for preparing medium- and long-chain fatty acid triglycerides according to claim 1, characterized in that, In step (6), the removal of byproducts is carried out by molecular distillation, with an evaporation temperature of 180℃-190℃ and a vacuum degree of 6Pa-8Pa.

8. A medium- to long-chain fatty acid triglyceride, characterized in that, It is prepared by the method for preparing medium- and long-chain fatty acid triglycerides according to any one of claims 1-8.

9. A nutritional preparation, characterized in that, Includes the medium- and long-chain fatty acid triglycerides as described in claim 8.

10. The preparation method of the medium- and long-chain fatty acid triglycerides according to any one of claims 1-8, the medium- and long-chain fatty acid triglycerides according to claim 8, and the nutritional preparation according to claim 9 are used in functional foods, pharmaceutical preparations, and sports nutrition products.

Images