A dag efficient enrichment method based on phase separation technology

Abstract

The application belongs to the technical field of oil separation and purification, and particularly relates to a DAG efficient enrichment method based on phase separation technology. The method provided by the application is as follows: differences in molecular polarity and interface behavior of DAG and TAG are utilized, so that the two substances show different phase selection paths in a system formed by a specific non-ionic surfactant and water, such as a gel phase / emulsion phase / microemulsion phase, and in particular, DAG is more likely to be combined with non-ionic surfactants such as Span 20 and PEG-35 castor oil, so as to be more left in the interface and the oil phase in the emulsion interior, while TAG is more likely to be left in the oil phase in the emulsion interior, so that DAG is relatively enriched in the upper emulsion phase, and high-efficiency separation and enrichment of DAG in DAG oil can be realized through a method of demixing and demulsification.

Description

Technical Field

[0001] This invention belongs to the field of oil separation and purification technology, and specifically relates to a highly efficient DAG enrichment method based on phase separation technology. Background Technology

[0002] Diacylglycerol (DAG), a natural functional component of oils and fats, has attracted widespread attention due to its functional properties in lowering blood lipids and reducing fat accumulation. However, the DAG content in natural oils and fats is usually less than 10%. To obtain high-content DAG products, industrial methods mainly employ enzymatic or chemical catalytic esterification reactions of glycerol and fatty acids, or selective hydrolysis of triglycerides (TAG) by lipases to prepare DAG. Regardless of the synthetic route used, the reaction products are mixtures containing DAG, unreacted TAG, monoglycerides (MAG), and free fatty acids (FFA). In particular, TAG and DAG have similar molecular structures and physicochemical properties; therefore, achieving efficient separation and enrichment of DAG and TAG under mild conditions remains a significant challenge.

[0003] Currently, the main purification methods for DAG include supercritical CO2 extraction, solvent crystallization, molecular distillation, and column chromatography. The core idea of ​​these methods is to separate DAG from components such as FFA, MAG, and TAG based on differences in volatility, solubility, polarity, or crystallization behavior. However, these methods still have limitations in terms of industrial applicability, isomer stability, and cost control.

[0004] Supercritical CO2 extraction typically uses CO2 as the separation medium under high pressure. It utilizes the differences in solubility of different lipid components in supercritical or liquid CO2 to selectively extract fatty acid esters, byproducts, or some low-polarity impurities from crude DAG products, thereby improving the purity of DAG. The main drawbacks of this method are high equipment investment and operating costs, high operating pressure, relatively long extraction cycle, and the purification rate is not advantageous.

[0005] Molecular distillation is currently the most widely used technique for DAG purification. Its basic principle is to separate FFA, MAG, DAG and TAG by utilizing the difference in volatility under high vacuum and short heating time. However, in the actual application of molecular distillation, there are problems such as easy boiling of liquid, high energy consumption and easy generation of risk factors (such as trichloropropanol ester and glycidyl ester) under high temperature conditions.

[0006] Column chromatography mainly relies on the polarity differences of DAG, MAG, TAG, and FFA on the stationary phase for adsorption-elution separation. This method is relatively cumbersome in terms of pretreatment steps and the entire purification cycle is time-consuming. Secondly, when scaled up for production, it will expose problems such as limited processing capacity and large reagent consumption. In addition, commonly used elution solvents and chromatography packing materials often do not meet the regulations and safety standards of the food industry, further limiting its application in actual production.

[0007] In summary, existing DAG separation and purification methods struggle to achieve a balance between low cost, high yield, high purity, and easy scale-up. Therefore, developing a green, efficient, and easily industrializable new DAG enrichment technology has significant industrial value.

[0008] Phase separation technology, also known as liquid-liquid phase separation technology, utilizes two immiscible or partially miscible solvent systems to achieve separation based on the difference in the partition coefficients of the target component in the two phases. This technology is characterized by mild operating conditions, low energy consumption, and ease of continuous operation, and has been widely used in fields such as biomacromolecules and natural product extraction. However, to date, there are no reports on its application for the efficient enrichment of DAG from TAG.

[0009] Based on this, the present invention proposes a method for efficiently enriching DAG from TAG using phase separation technology. By constructing a specific two-phase solvent system, the method utilizes the significant difference in the distribution behavior of DAG and TAG in the specific two-phase solvent system to achieve mild and efficient enrichment of DAG. Summary of the Invention

[0010] To address the above technical problems, this invention proposes a method for efficient enrichment of DAG based on phase separation technology, particularly a method for efficient separation and enrichment of DAG from TAG.

[0011] The present invention provides a DAG selective enrichment method driven by phase behavior differences. Specifically, it utilizes the differences in molecular polarity and interfacial behavior between DAG and TAG to make them exhibit different phase selection paths (gel phase / emulsion phase / microemulsion phase, etc.) in a mixed two-phase system formed by a specific nonionic surfactant and water. This allows DAG to be relatively enriched in a single phase, separating it from TAG and increasing the enrichment content of DAG.

[0012] The technical solution provided by this invention is as follows:

[0013] A highly efficient enrichment method for DAG based on phase separation technology is specifically described as follows: a surfactant and water are added to DAG oil to form a two-phase system. The DAG oil contains DAG and TAG. By utilizing the differences in molecular polarity and interfacial behavior between DAG and TAG, highly efficient enrichment of DAG in the DAG oil is achieved. The surfactant is a nonionic surfactant.

[0014] Preferably, the nonionic surfactant is selected from at least one of PEG-35 castor oil and Span 20.

[0015] Preferably, in the DAG oil, the mass percentage of DAG is ≥40%, and the remainder is TAG.

[0016] As a further preferred embodiment, in the DAG oil, DAG accounts for 40% of the oil's mass, with the remainder being TAG.

[0017] Preferably, the present invention enriches DAG in 40% DAG oil (wt%, with the remainder being TAG), wherein the mass ratio of 40% DAG oil: nonionic surfactant: water is 20~60: 2~10: 40~80.

[0018] As a further preferred embodiment, the present invention enriches DAG in 40% DAG oil (wt%, with the remainder being TAG), wherein the mass ratio of 40% DAG oil: nonionic surfactant: water is 25~55: 2~6: 40~75.

[0019] In this invention, 40% DAG oil is prepared by mixing 80% DAG oil with pure TAG oil in a 1:1 mass ratio. The oil is a common edible oil, including any one or a combination of several of corn oil, peanut oil, soybean oil, and rapeseed oil.

[0020] Furthermore, the efficient DAG enrichment method based on phase separation provided by this invention specifically includes the following steps:

[0021] S1 plots ternary phase diagrams of DAG, TAG, nonionic surfactant, and water respectively, and selects the difference points where DAG and TAG form different phases and the points near the phase interface to obtain the mass ratio of DAG, nonionic surfactant, and water corresponding to each point.

[0022] S2 involves mixing DAG oil with water and a nonionic surfactant according to the mass ratio selected in S1, stirring to carry out an emulsification reaction, and then allowing the mixture to stand after the reaction is complete. The system with a distinct stratified state is then selected.

[0023] S3 separates the system with obvious stratification obtained from S2, takes the upper emulsion for demulsification, centrifuges it, takes the supernatant, detects the DAG content in the supernatant, and compares and analyzes the DAG content to obtain the mass ratio corresponding to the system with the highest DAG content. This mass ratio is the optimal mass ratio of DAG oil to nonionic surfactant and water when enriching DAG from DAG oil.

[0024] S4 involves mixing DAG oil, nonionic surfactant, and water according to the optimal mass ratio obtained in S3, and then repeating the emulsification and demulsification operations of S2 to S3 to achieve efficient enrichment of DAG in DAG oil.

[0025] In the DAG high-efficiency enrichment method provided by the present invention, preferably, in step S2, the stirring speed is 450~550 rpm for 3~7 min.

[0026] Preferably, in step S3, NaCl solution is added to the upper emulsion, and demulsification is performed at a temperature of 90~98℃.

[0027] Preferably, in step S3, the mass fraction of the NaCl solution is 10%, and the volume ratio of the upper emulsion to the NaCl solution is 2~3:1.

[0028] Preferably, in step S3, the centrifugation rate is 9500~11000 rpm, and the centrifugation time is 5~7 min.

[0029] Furthermore, the present invention provides a DAG-based efficient enrichment method based on phase separation, comprising the following steps:

[0030] S1 plots ternary phase diagrams of DAG, TAG, nonionic surfactant, and water respectively, and screens out the difference points where DAG and TAG form different phases and the points near the phase interface, and obtains the mass ratio of DAG, nonionic surfactant, and water corresponding to each point.

[0031] S2 mixes 40% DAG oil, nonionic surfactant, and water according to the mass ratio selected in S1, and stirs the mixture at 510 rpm for 5 min. After the reaction is completed, the mixture is allowed to stand, and the system with obvious stratification is selected from the mixture.

[0032] S3 separates the system with obvious stratification obtained from S2, takes the upper emulsion, adds 1 / 3 to 1 / 2 volume of 10% NaCl solution to the upper emulsion, and demulsifies at 92 to 95°C until the emulsion changes from milky white to clear yellow. Centrifuge at 10,000 rpm for 5 to 6 minutes, take the supernatant, detect the DAG content in the obtained supernatant, and compare and analyze the DAG content to obtain the mass ratio corresponding to the system with the highest DAG content. This mass ratio is the optimal mass ratio of 40% DAG oil to nonionic surfactant and water when enriching DAG from DAG oil.

[0033] When the surfactant is PEG-35 castor oil, the optimal mass ratio of 40% DAG oil:PEG-35 castor oil:water is 50~54:4~6:40~45, and the most preferred mass ratio of the three is 52.94:5.88:41.18.

[0034] When the surfactant is Span 20, the optimal mass ratio of 40% DAG oil:Span 20:water is 25~28:2~3:68~72, and the most preferred mass ratio of the three is 26.47:2.94:70.59;

[0035] S4 involves mixing 40% DAG oil, a nonionic surfactant, and water according to the optimal mass ratio obtained in S3, and then repeating the emulsification and demulsification operations of S2 to S3 to achieve efficient enrichment of DAG in 40% DAG oil.

[0036] The present invention has the following advantages and effects compared with the prior art:

[0037] This invention utilizes the differences in molecular polarity and interfacial behavior between DAG and TAG to enable them to exhibit different phase selectivity pathways (gel phase / emulsion phase / microemulsion phase, etc.) in systems composed of specific nonionic surfactants and water. In particular, DAG is more likely to bind with nonionic surfactants such as Span 20 and PEG-35 castor oil, thus remaining more at the interface and in the oil phase inside the emulsion. TAG, on the other hand, is more likely to remain in the oil phase inside the emulsion, resulting in a relative enrichment of DAG in the upper emulsion phase. The efficient separation and enrichment of DAG in DAG oil can be achieved by demulsification after separation. However, in a two-phase system formed by nonionic surfactants such as Tween-20 and water, the selectivity difference between DAG and TAG is not significant, making it difficult to achieve efficient enrichment of DAG. Attached Figure Description

[0038] Figure 1This invention uses HPLC-RID to detect the peak times of three types of oils (TAG, DAG, MAG) and standard curves of DAG standards at different concentrations.

[0039] Figure 2 This is a schematic diagram illustrating the mechanism of the DAG high-efficiency enrichment method provided by the present invention;

[0040] Figure 3 Figure A shows the ternary phase diagram of TAG corn oil / PEG-35 castor oil / water in Example 1 of this invention, where the points marked in the red box are the differences in the formation of different phases by DAG and TAG; Figure B shows the ternary phase diagram of DAG corn oil / PEG-35 castor oil / water, where the points marked in the red box are the differences in the formation of different phases by DAG and TAG; Figure C shows the ternary phase diagram of DAG corn oil / PEG-35 castor oil / water, where the points marked in the red box are the points near the phase interface of DAG and TAG.

[0041] Figure 4 This is a gel state diagram formed under the mass system corresponding to some of the differences in Example 1 of the present invention;

[0042] Figure 5 The images show the morphology of the two-phase system obtained under different mass ratios in Example 1 of the present invention (left) and the demulsification effect of the upper emulsion of the layered system (right).

[0043] Figure 6 The enrichment content of DAG and the oil yield in the DAG corn oil / PEG-35 castor oil / water system in Example 1 of the present invention;

[0044] Figure 7 This is a screening diagram of the differences in the formation of different phases of DAG and TAG in the ternary phase diagram of DAG corn oil / Span 20 / water in Example 2 of the present invention;

[0045] Figure 8 The enrichment content of DAG and the oil yield in the 40% DAG corn oil / Span 20 / water system in Example 2 of the present invention;

[0046] Figure 9 The enrichment of DAG in three different vegetable oil systems in Example 3 of this invention is shown.

[0047] Figure 10 The ternary phase diagram of the DAG corn oil / Tween-20 / water system in Comparative Example 1 of this invention;

[0048] Figure 11 The enrichment content of DAG and the oil yield in the 40% DAG corn oil / Tween-20 / water system of Comparative Example 1 of this invention;

[0049] Figure 12 The graph shows the static stability of 80% DAG corn oil / water, 40% DAG corn oil / water, and TAG corn oil / water emulsions in Comparative Example 2 of this invention, as well as the DAG content in the upper layer after emulsification of 40% DAG corn oil / water. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0051] This invention uses high-performance liquid chromatography (HPLC) to determine the enrichment degree of DAG in oil, following the method specified in the national standard GB / T 26636-2011. The specific steps are as follows:

[0052] (1) Pretreatment of oil samples: First, place 40% DAG oil in a water bath and heat it at 70°C for 5~30 min (until the 40% DAG oil appears clear when observed with the naked eye). Then, accurately weigh 50 mg of oil sample from the heated oil, add 2 mL of THF and 0.1% BHT and shake to mix well. Let it stand for 5 min, and finally filter it with an organic filter membrane with a pore size of 1 μm for later use.

[0053] (2) Preparation of mobile phase: Accurately weigh 500 mL THF, add 0.1% BHT and mix well. Then filter with an organic filter membrane with a pore size of 0.22 μm, sonicate for 5 min and set aside for later use.

[0054] (3) High-performance liquid chromatography (HPLC) method: The HPLC column and detector used in this method are PLgel 100 Å, 7.5 × 300 mm, 5 µm and a refractive index detector (RID), respectively. The detector temperature is 35℃, the column oven temperature is 30℃, the flow rate is 0.8 mL / min, the injection volume is 10 μL, and the sample detection time is 20 min. Each sample is measured in triplicate, and the average value is taken.

[0055] In addition, HPLC-RID was used to detect the peak times of three oil (TAG, DAG, MAG) standards and different concentrations of DAG standards according to the above method, and standard curves were plotted, as shown below. Figure 1 As shown.

[0056] Example 1

[0057] Combination Figure 2 The preparation method of 40% DAG oil and the separation and enrichment mechanism of DAG are explained in this embodiment to illustrate the technical solution provided.

[0058] In this embodiment, 80% DAG corn oil (purchased from Heze Zhonghe Jianyuan Biotechnology Co., Ltd., model 89Z16B581, hereinafter the same) and TAG corn oil (purchased from Heze Zhonghe Jianyuan Biotechnology Co., Ltd., model 89Z16B581, hereinafter the same) were mixed at a mass ratio of 1:1 to prepare 40% DAG corn oil (containing 60% TAG corn oil). Utilizing the difference in molecular polarity at the interface between DAG and TAG—DAG having stronger surface activity and more easily forming a stable emulsion, while TAG tends to form a gel phase—emulsification treatment was used to spontaneously separate the two into different phases, thereby enriching DAG in the mixed oil.

[0059] It should be noted that since there is currently no high-purity 100% DAG oil in the industry, 80% DAG oil is used in this application instead of high-purity 100% DAG oil to draw the phase diagram.

[0060] The DAG high-efficiency enrichment method based on phase separation technology provided in this embodiment has the following specific steps:

[0061] S1 plotted ternary phase diagrams for DAG corn oil, TAG corn oil, PEG-35 castor oil (HLB between 13 and 14, a hydrophilic surfactant), and water, respectively. The differences in the formation of different phases by 40% DAG corn oil and 60% TAG corn oil, as well as the points near the phase interface, were screened out, and the mass ratios of DAG corn oil, PEG-35 castor oil, and water corresponding to each point were obtained.

[0062] like Figure 3 As shown, Figure 3 Figure A shows the ternary phase diagram of TAG corn oil / PEG-35 castor oil / water, where the points marked in the red boxes are the differences in the formation of different phases by DAG and TAG; Figure B shows the ternary phase diagram of DAG corn oil / PEG-35 castor oil / water, where the points marked in the red boxes are the differences in the formation of different phases by DAG and TAG; Figure C shows the ternary phase diagram of DAG corn oil / PEG-35 castor oil / water, where the points marked in the red boxes are the points near the phase interface between DAG and TAG.

[0063] Based on phase diagrams A and B, the differences between DAG and TAG corn oil were identified. Some of these differences resulted in systems exhibiting a distinct gel state (e.g., ...). Figure 4 That is, the selection differences between DAG and TAG in the system are not significant, therefore the inventors will not separate these differences separately, but only use 17 of them here. Figure 3 Taking the points within the red box as an example, the technical solution provided by this invention will be described. The mass ratios corresponding to 17 difference points are obtained, totaling 17 groups, as shown in Table 1.

[0064] Table 1. Differences in the formation of different phases by DAG and TAG and their corresponding mass ratios. 1 72.73 18.18 9.09 2 81.82 9.09 9.09 3 33.33 50.00 16.66 4 41.66 41.66 16.66 5 50.00 33.33 16.66 6 66.66 16.66 16.66 7 15.38 61.53 23.07 8 23.07 53.84 23.07 9 30.77 46.15 23.07 10 61.54 15.38 23.07 11 7.14 64.29 28.57 12 37.50 25.00 37.50 13 29.41 29.41 41.17 14 33.33 22.22 44.44 15 21.05 31.58 47.37 16 14.63 34.15 51.22 17 3.85 34.62 61.54

[0065] S2 mixes 40% DAG corn oil, PEG-35 castor oil, and water according to the 17 mass ratios selected in S1, and stirs at 510 rpm for 5 min to carry out emulsification reaction. After the reaction is completed, let it stand.

[0066] The state of the obtained reaction products is as follows: Figure 5 As shown in the middle left figure.

[0067] As shown in the figure, some of the obtained systems, even after standing, still exhibit an emulsion-gel phase, leaning more towards a gel phase. The reasons for this phenomenon are speculated to be: firstly, the difference points in the TAG / DAG phase diagram have a clear directional distribution: most are concentrated in the gel region and the vicinity of the gel / emulsion boundary, rather than within the individual phase regions; secondly, the TAG content in 40% DAG oil is approximately 60%, which diminishes the strong interfacial tension regulation ability of high-purity DAG systems, thus making it more prone to forming an emulsion-gel phase. This indicates that in a DAG / TAG mixed system, the two originally independent phase formation processes interact, ultimately forming a relatively stable single phase.

[0068] In addition, from Figure 5 The left figure also shows that some systems exhibit obvious stratification. The inventors further speculate that near the phase interface, the difference in phase behavior between DAG and TAG makes it easier for components to be distributed differently between different phases. DAG tends to participate in the construction at the interface, thus achieving DAG enrichment. Therefore, based on the above principle, the inventors measured the DAG content obtained from the stratification of the mass system corresponding to the points near the phase interface. A total of 12 point values ​​were obtained from 12 points near the phase interface. Figure 3 The mass ratios corresponding to the portion within the red box in Figure C are shown in Table 2 below.

[0069] Table 2. Points near the DAG / TAG interface and their corresponding mass ratios 1 53.33 13.33 33.34 2 60 6.67 33.33 3 50 12.5 37.5 4 56.25 6.25 37.5 5 47.06 11.76 41.18 6 52.94 5.88 41.18 7 44.44 11.12 44.44 8 50 5.56 44.44 9 42.11 10.53 47.37 10 47.37 5.26 47.37 11 39.02 9.76 51.22 12 43.90 4.88 51.22

[0070] S3 separated the system corresponding to 12 different mass ratios in S2, took the upper emulsion, added a 10% NaCl solution to the upper emulsion, the volume ratio of upper emulsion to 10% NaCl solution was 2.5:1, and reacted at 94℃ for 15-30 min. The demulsification effect of the emulsion was observed. After the emulsion changed from milky white to clear yellow, it was centrifuged at 10000 rpm for 6 min, and the supernatant was taken. Figure 5As shown in the right figure, the DAG content was determined by HPLC-RID. A 40% DAG oil (without surfactant or water) was used as a control group. The enrichment of DAG in the upper emulsion phase of the two-phase system obtained under different mass ratios after demulsification and the oil yield are shown in the figure. Figure 6 As shown in the figure, lowercase letters are used to compare different components within the same system. Different letters indicate significant differences (P<0.05), and the same applies below.

[0071] Figure 6 It can be seen that the DAG enrichment content of the upper emulsion of sample 6 (40% DAG corn oil:PEG-35 castor oil: water = 52.94:5.88:41.18) is much higher than that obtained under other ratios, increasing by about 17% compared with the control group. The oil yield (the ratio of the mass of oil obtained after demulsification in the upper emulsion to the mass of the initial input oil) is also relatively high, reaching 69.3%.

[0072] In step S4, 40% DAG corn oil, PEG-35 castor oil, and water are mixed according to the mass ratio selected in step S3. The emulsification and demulsification operations in steps S2 to S3 are repeated to achieve efficient enrichment of DAG in 40% DAG corn oil.

[0073] Example 2

[0074] A highly efficient DAG enrichment method based on phase separation technology differs from Example 1 in that Span20 (HLB=8.6, a hydrophobic surfactant) is used instead of PEG-35 castor oil. The specific operation of this example is as follows:

[0075] S1 plots a ternary phase diagram of DAG corn oil, Span 20, and water, and filters out the points of difference near the phase interfaces, such as... Figure 7 As shown in the red box, there are a total of 6 points, and the mass ratio of the three components corresponding to each point is obtained; see Table 3 below.

[0076] Table 3. Points near the DAG-TAG interface and their corresponding mass ratios 1 26.47 2.94 70.5 2 23.08 2.56 74.36 3 20 2.22 77.78 4 16.98 1.89 81.13 5 14.29 1.59 84.13 6 11.25 1.25 87.5

[0077] S2 mixes 40% DAG corn oil, Span 20, and water according to the mass ratio selected in S1, and stirs at 510 rpm for 5 min to carry out emulsification reaction. After the reaction is completed, the mixture is allowed to stand and separate into layers to obtain the corresponding two-phase systems at different mass ratios.

[0078] S3 separated the two-phase system corresponding to different mass ratios in S2, took the upper emulsion, and added a 10% NaCl solution (volume ratio of upper emulsion to 10% NaCl solution) to the upper emulsion (volume ratio of upper emulsion to 10% NaCl solution was 2.5:1). The reaction was carried out at 94℃ for 15-30 min, and the demulsification effect was observed. After the emulsion changed from milky white to clear yellow, it was centrifuged at 10000 rpm for 6 min, and the supernatant was taken. The DAG content was detected by HPLC-RID. 40% DAG corn oil (without added surfactant or water) was used as a control group. The enrichment of DAG and oil yield of the upper emulsion phase of the two-phase system obtained under different mass ratios after demulsification are shown in the figure below. Figure 8 As shown.

[0079] Figure 8 The results show that under the obtained six mass ratio systems, the enrichment rate of DAG was much higher than that of the control group. This indicates that good enrichment of DAG in 40% DAG corn oil can be achieved within this mass range. Among them, sample 6 (40% DAG corn oil: Span 20: water = 26.47: 2.94: 70.59) had the highest DAG content in the upper emulsion, reaching 66%, which was 26% higher than that of the 40% DAG corn oil control group, and the oil yield was as high as 64.2%.

[0080] In step S4, 40% DAG corn oil, Span 20, and water are mixed according to the optimal mass ratio selected in step S3 (40% DAG corn oil: Span 20: water = 26.47: 2.94: 70.59). Steps S2 to S3 are repeated to achieve efficient enrichment of DAG in 40% DAG corn oil.

[0081] Example 3

[0082] In this embodiment, three different vegetable oils (peanut oil, soybean oil, and rapeseed oil) were used in a 40% DAG system. Span 20 was added, and the mixtures were compounded according to a mass ratio of 40% DAG:Span 20:water = 28:3:69. Separation was performed according to the method in Example 1. A 40% DAG corn oil system (without added surfactants or water) was used as a control group. The results are as follows. Figure 9 As shown in the figure, DAG can be well separated from each vegetable oil, indicating that the selective enrichment of DAG by phase separation provided by this invention is not limited by the type of vegetable oil and has broad application potential.

[0083] Comparative Example 1

[0084] A highly efficient DAG enrichment method based on phase separation technology, differing from Example 1 in that Tween-20 (HLB=16.7, a hydrophilic surfactant) is used instead of PEG-35 castor oil. The specific operation of this comparative example is as follows:

[0085] S1 plots a ternary phase diagram of 40% DAG corn oil, Tween-20, and water, and filters out points with phase differences and points near phase interfaces, such as... Figure 10 As shown in the red box, there are a total of 12 points, and the mass ratio of the three components is obtained for each point.

[0086] S2 mixes 40% DAG corn oil, Tween-20, and water according to the mass ratio selected in S1, and stirs at 510 rpm for 5 min to carry out emulsification reaction. After the reaction is completed, the mixture is allowed to stand and separate into layers to obtain the corresponding two-phase systems at different mass ratios.

[0087] S3 separated the two-phase systems corresponding to different mass ratios (a total of 12 groups) in S2. The upper emulsion was taken, and a 10% NaCl solution was added to it at a volume ratio of 2.5:1 (upper emulsion:10% NaCl solution). The reaction was carried out at 94℃ for 15-30 min, and the demulsification effect was observed. After the emulsion changed from milky white to clear yellow, it was centrifuged at 10000 rpm for 6 min. The supernatant was taken, and the DAG content was detected by HPLC-RID. 40% DAG oil (without added surfactant or water) was used as a control group. The enrichment of DAG and oil yield of the upper emulsion phase of the two-phase system obtained under different mass ratios after demulsification are shown in the figure below. Figure 11 As shown.

[0088] Figure 11 The results show that, under the obtained 12 mass ratio systems, the overall enrichment rate of DAG was not as good as that of the control group. Even under the ratio of the 12th sample, its enrichment effect on DAG was only almost the same as that of the control group, far inferior to the separation effect of nonionic surfactants such as PEG-35 castor oil and Span 20. It can be seen that when using Tween-20, a nonionic surfactant, the distribution effect of DAG and TAG is not significantly different, making it difficult to achieve efficient enrichment of DAG.

[0089] Comparative Example 2

[0090] A highly efficient DAG enrichment method based on phase separation technology differs from Example 1 in that no surfactant is added in this comparative example; the oil-water mixture is directly constructed through homogenization. The specific operation of this comparative example is as follows:

[0091] 40% DAG corn oil, 80% DAG, and TAG were each mixed with water at a mass ratio of 1:2 and homogenized at 10,000 rpm for 1 min. After homogenization, the mixtures were left at room temperature for 0 h, 0.5 h, 1 h, 1.5 h, 2 h, 4 h, and 16 h, and the state at each time point was recorded by photograph. Subsequently, the emulsions of 40% DAG corn oil homogenized for 1 h, 2 h, and 4 h were demulsified, and the DAG content was measured.

[0092] Figure 12 It is evident that, without the addition of external surfactants, although some DAG can be obtained by homogenizing and forming an emulsion and undergoing a layering process, it is impossible to achieve efficient separation of DAG and TAG, nor is it possible to obtain a high content of DAG.

[0093] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A highly efficient enrichment method for DAG based on phase separation technology, characterized in that, A two-phase system is formed by adding a surfactant and water to DAG oil. The DAG oil contains DAG and TAG. By utilizing the differences in molecular polarity and interfacial behavior between DAG and TAG, the DAG in the DAG oil is efficiently enriched. The surfactant is a nonionic surfactant.

2. The DAG high-efficiency enrichment method as described in claim 1, characterized in that, The nonionic surfactant is selected from either PEG-35 castor oil or Span 20; in the DAG oil, the mass percentage of DAG is ≥40%, and the remainder is TAG.

3. The DAG high-efficiency enrichment method as described in claim 2, characterized in that, DAG in 40% DAG oil (wt%) was enriched, wherein the mass ratio of 40% DAG oil: nonionic surfactant: water was 20~60: 2~10: 40~80.

4. The DAG high-efficiency enrichment method as described in claim 3, characterized in that, The DAG in 40% DAG oil (wt%) is enriched, wherein the mass ratio of 40% DAG oil: nonionic surfactant: water is 25~55: 2~6: 40~75, and the oil includes any one or a combination of several of corn oil, peanut oil, soybean oil and rapeseed oil.

5. The DAG high-efficiency enrichment method as described in claim 1, characterized in that, The steps include the following: S1 plots ternary phase diagrams of DAG, TAG, nonionic surfactant, and water respectively, and screens out the difference points where DAG and TAG form different phases and the points near the phase interface, and obtains the mass ratio of DAG, nonionic surfactant, and water corresponding to each point. S2 involves mixing DAG oil with water and nonionic surfactants according to the mass ratio selected in S1, stirring to carry out an emulsification reaction, and then allowing the mixture to stand after the reaction is complete. The system with a clear stratified state is then selected from the mixture. S3 separates the system with obvious stratification obtained from S2, takes the upper emulsion for demulsification, centrifuges it, takes the supernatant, detects the DAG content in the supernatant, and compares and analyzes the DAG content to obtain the mass ratio corresponding to the system with the highest DAG content. This mass ratio is the optimal mass ratio of DAG oil to nonionic surfactant and water when enriching DAG from DAG oil. S4 involves mixing DAG oil, nonionic surfactant, and water according to the optimal mass ratio obtained in S3, and then repeating the emulsification and demulsification operations of S2 to S3 to achieve efficient enrichment of DAG in DAG oil.

6. The DAG high-efficiency enrichment method as described in claim 5, characterized in that, Stir at 450-550 rpm for 3-7 minutes in S2.

7. The DAG high-efficiency enrichment method as described in claim 5, characterized in that, In S3, NaCl solution is added to the upper emulsion, and demulsification is carried out at a temperature of 90~98℃.

8. The DAG efficient enrichment method as described in claim 7, characterized in that, In S3, the mass fraction of the NaCl solution is 10%, and the volume ratio of the upper emulsion to the NaCl solution is 2~3:

1.

9. The DAG high-efficiency enrichment method as described in claim 5, characterized in that, In S3, the centrifugation rate is 9500~11000 rpm, and the centrifugation time is 5~7 min.

10. The efficient DAG enrichment method as described in claim 1, characterized in that, The steps include the following: S1 plots ternary phase diagrams of DAG, TAG, nonionic surfactant, and water respectively, screens out the differences in the formation of different phases of DAG and TAG and the points near the phase interface, and obtains the mass ratio of DAG oil to nonionic surfactant and water under the corresponding conditions. S2 mixes 40% DAG oil, nonionic surfactant, and water according to the mass ratio selected in S1, and stirs the mixture at 510 rpm for 5 min. After the reaction is completed, the mixture is allowed to stand, and the system with obvious stratification is selected from the mixture. S3 separates the system with obvious stratification obtained from S2, takes the upper emulsion, adds 1 / 3 to 1 / 2 volume of 10% NaCl solution to the upper emulsion, and demulsifies at 92 to 95°C until the emulsion changes from milky white to clear yellow. Centrifuge at 10,000 rpm for 5 to 6 minutes, take the supernatant, detect the DAG content in the obtained supernatant, and compare and analyze the DAG content to obtain the mass ratio corresponding to the system with the highest DAG content. This mass ratio is the optimal mass ratio of 40% DAG oil to nonionic surfactant and water when enriching DAG from DAG oil. S4 involves mixing 40% DAG oil, a nonionic surfactant, and water according to the optimal mass ratio obtained in S3, and then repeating the emulsification and demulsification operations of S2 to S3 to achieve efficient enrichment of DAG in 40% DAG oil.

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