A method for improving the sustained release properties of medium-chain fatty acid triglycerides

Abstract

The present application belongs to the technical field of medium-chain fatty acid triglyceride performance improvement, and particularly relates to a method for improving the sustained-release performance of medium-chain fatty acid triglyceride. The method of the present application is to prepare the medium-chain fatty acid triglyceride into microcapsules to improve its sustained-release performance, so as to avoid the occurrence of diarrhea and intestinal gas and other intestinal diseases caused by excessive one-time intake stimulating the gastrointestinal tract. The specific operation is as follows: taking whey protein and inulin as the composite wall material, taking medium-chain fatty acid triglyceride as the core material, emulsifying under the action of the compounded emulsifier, and adopting the spray drying method to prepare into microcapsules, wherein the weight ratio of the whey protein to the inulin is 2.87:1. The prepared microcapsules have a microcapsule embedding rate of 96.25%, and the in-vitro simulated gastrointestinal tract digestion release rate is 84.53%, so that the release in the gastrointestinal tract is delayed. In addition, the addition of inulin in the microcapsule wall material can meet the needs of diabetic patients, and further provides the storage stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of medium-chain fatty acid triglyceride performance improvement, and particularly relates to a method for improving the sustained-release performance of medium-chain fatty acid triglyceride. BACKGROUND

[0002] Medium-chain fatty acid triglyceride (MCT) is composed of medium-chain glyceride fatty acids with a carbon chain length of 6-12. Since its structure is different from that of long-chain fatty acid triglyceride, and the molecular weight is small, the MCT is less dependent on bile salts and pancreatic enzymes after reaching the small intestine, and thus can be directly absorbed by the small intestinal villus epithelial cells, enter the liver through the hepatic portal vein for oxidation to provide energy, and almost cannot be accumulated in the liver, fat and other tissues, and has the effects of improving lipid metabolism, providing energy quickly, relieving fatigue and the like.

[0003] Studies have shown that food containing 5g of MCT can produce a food-induced thermogenic effect within 6 hours after a meal, can induce oxidation of accumulated fat in the body, consume fat in the body, and increase satiety, while also reducing protein consumption and protecting non-fat tissues such as muscle, so the MCT has strong "weight loss strength".

[0004] In addition, the energy of MCT is 8.3 kcal / g, and the energy of carbohydrates is 4 kcal / g, and such a high energy content of MCT does not affect the content of glucose and insulin in the body, and is quite friendly to diabetics.

[0005] However, the current application of MCT has the following problems:

[0006] Firstly, although MCT is a star in the fat industry, the amount of MCT consumed must be strictly controlled, and the single intake amount should not be too much. Generally, the intake amount of MCT in food is: 15-30 g / day for children, and 40-100 g / day for adults. If too much MCT is ingested at one time, since MCT can be rapidly digested by the body and rapidly hydrolyzed in the intestine, it is easy to cause an increase in the osmotic pressure in the intestine, and thus cause intestinal diseases such as diarrhea and flatulence. In addition, MCT crude oil mainly contains saturated fatty acids, which have a certain oxidation stability, but can also be oxidized when stored at a relatively high temperature, causing the product to deteriorate.

[0007] Therefore, in order to realize the utilization of MCT, the problem of rapid release of MCT in the body must be solved, and the sustained release of MCT in the gastrointestinal tract is achieved to achieve the effect of slow release and slow absorption. SUMMARY

[0008] In order to solve the above technical problems, the application provides a method for improving the sustained-release performance of medium-chain fatty acid triglyceride.

[0009] The MCT microcapsule with sustained-release performance provided by the application is ellipsoidal, smooth in surface, and has no adhesion, and the average particle size of the microcapsule is 489 nm.

[0010] In addition, the MCT microcapsule with good sustained-release performance prepared by the application comprises core material and composite wall material, wherein the core material is MCT, and the composite wall material is whey protein and inulin.

[0011] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0012] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0013] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0014] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0015] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0016] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0017] Preferably, the weight ratio of the core material to the composite wall material is 1:1.08.

[0018] The method for improving the sustained-release performance of medium-chain fatty acid triglyceride provided by the application is realized through the following technical solutions:

[0019] (1) The composite wall material is dissolved in distilled water at 50-80 DEG C, and constant temperature stirring is carried out for 10-30 min until the solution is uniform;

[0020] (2) MCT is added to the solution obtained in step (1), and then a compound emulsifier is added, and emulsification is carried out at 50-80 DEG C, and uniform stirring is continued, and an initial emulsion is formed;

[0021] (3) The initial emulsion obtained in step (2) is subjected to high-pressure homogenization and spray drying, and MCT microcapsules with sustained-release performance are obtained.

[0022] In the above steps, the complex emulsifier is a mixture of monoglyceride and sodium carboxymethyl cellulose, wherein the weight ratio of monoglyceride to sodium carboxymethyl cellulose is 1-3:1-3.

[0023] Preferably, the weight ratio of monoglyceride to sodium carboxymethyl cellulose is 1:1-3.

[0024] Preferably, the weight ratio of monoglyceride to sodium carboxymethyl cellulose is 1:1.

[0025] The complex emulsifier is added in an amount of 0.2-0.6 g / 100 mL.

[0026] Preferably, the complex emulsifier is added in an amount of 0.4 g / 100 mL.

[0027] The high-pressure homogenization is performed under the conditions of 30-50 Mpa and 1-3 times of homogenization.

[0028] Preferably, the high-pressure homogenization is performed under the conditions of 30-40 Mpa and 2 times of homogenization.

[0029] Preferably, the high-pressure homogenization is performed under the conditions of 40 Mpa and 2 times of homogenization.

[0030] The spray drying is performed at an inlet air temperature of 150-240 DEG C and a sample feeding speed of 10-18 mL / min.

[0031] Preferably, the spray drying is performed at an inlet air temperature of 140-190 DEG C and a sample feeding speed of 10-16 mL / min.

[0032] The present application provides a kind of MCT-containing microcapsule obtained by the method of the present application, and the application of the microcapsule in the prevention or treatment of diabetes products and its preparation, which is also the focus of the present application.

[0033] As is known to all, microcapsule technology is to use natural or synthetic material as wall material, and the core material is encapsulated by a certain method, so that the core material is isolated from the external environment and is not affected by the external environment, thereby improving the stability of the core material.

[0034] However, current research on microcapsule preparation mainly focuses on embedding rate and oil content, and the research on the properties of microcapsules is also concentrated on basic physical and chemical properties, and there is a lack of research on food ingredients specially for chronic disease patients with metabolic dysfunction such as obesity patients and diabetic patients in current microcapsule products; in addition, the in vitro simulated digestion release research of microcapsules is not mature, and the slow-release performance of microcapsules in the gastrointestinal tract needs to be improved.

[0035] Inulin is a low glycemic index fructose, which has gel properties. Adding inulin in the wall material can not only increase the compactness of the microcapsule shell, but also meet the needs of chronic disease patients such as diabetes and obesity; in addition, inulin has strong hygroscopicity and can bind free water, reducing water activity, delaying water evaporation in food, preventing product flavor change, and prolonging food shelf life and shelf life.

[0036] The present application provides a method for improving the slow-release performance of medium-chain fatty acid triglycerides, mainly by making MCT into microcapsules. The method not only converts liquid MCT into solid powder, but also achieves good slow-release effect, completely avoiding the gastrointestinal problems caused by excessive one-time intake of MCT, such as diarrhea and other phenomena.

[0037] In addition, the addition of inulin not only alleviates the evaporation of water in the capsule, prolongs the shelf life of the capsule, but also expands the application population of the microcapsule of the present application.

[0038] The present application has the following advantages:

[0039] (1) The present application provides a method for improving the slow-release performance of medium-chain fatty acid triglycerides in the gastrointestinal tract, i.e. by using MCT as the core material and inulin and whey protein as the composite wall material to make MCT into microcapsules, thereby improving the slow-release performance of MCT in the body and avoiding the problem of gastrointestinal discomfort caused by excessive one-time intake;

[0040] (2) The present application also provides a MCT microcapsule with good slow-release performance, which is ellipsoidal in shape, smooth in surface, and non-adhesive. The average particle size of the microcapsule is 489 nm, the solubility is strong, and the microcapsule is easily absorbed by the human body;

[0041] (3) The method of the present application only uses MCT and inulin as energy-providing substances, which can induce the oxidation of accumulated fat in the body, consume fat in the body, rapidly supplement the energy required by the body, and relieve fatigue; and the two substances themselves belong to low GI food materials, which will not affect the glucose and insulin content and metabolism of the body while providing energy, and are completely suitable for obesity patients, even for obesity patients and weight loss people with glucose metabolism dysfunction such as diabetes;

[0042] (4) The application alleviates the evaporation of water in the capsule by adding inulin, which is conducive to further prolonging the shelf life of the capsule and further improving the storage stability of the MCT microcapsule product;

[0043] (5) The application uses a spray drying method to embed the core material, which isolates the core material from the external environment, avoids external environmental interference, improves the stability of the core material, and is simple in process operation, low in cost and easy to realize large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a graph showing the influence of emulsification temperature on the embedding rate of MCT microcapsules;

[0045] Figure 2 is a graph showing the influence of spray drying inlet air temperature on the embedding rate of MCT microcapsules;

[0046] Figure 3 is a graph showing the influence of sample injection speed on the embedding rate of MCT microcapsules;

[0047] Figure 4 is a graph showing the influence of the ratio of complex wall material on the embedding rate of MCT microcapsules;

[0048] Figure 5 is a graph showing the influence of the ratio of core material to wall material on the embedding rate of MCT microcapsules;

[0049] Figure 6 is a graph showing the influence of the amount of wall material added on the embedding rate of MCT microcapsules;

[0050] Figure 7 is a graph showing the influence of the amount of emulsifier added on the embedding rate of MCT microcapsules;

[0051] Figure 8 is a graph showing the influence of the ratio of complex emulsifier on the embedding rate of MCT microcapsules;

[0052] Figure 9 is a graph showing the particle size distribution of MCT microcapsules;

[0053] Figure 10 is a scanning electron microscope image of MCT microcapsules;

[0054] Figure 11 is a differential scanning calorimetry graph of MCT microcapsules;

[0055] Figure 12 is a graph showing the change in POV value of MCT crude oil and MCT microcapsules in an accelerated storage experiment;

[0056] Figure 13 is a graph showing the change in acid value of MCT crude oil and MCT microcapsules in an accelerated storage experiment;

[0057] Figure 14 is a graph showing the change in oil retention rate of MCT microcapsules in an accelerated storage experiment;

[0058] Figure 15 is a graph of the cumulative release rate of the core material of the MCT microcapsules during in vitro simulated digestion;

[0059] Figure 16 is a model fitting curve of the release of the MCT microcapsules during in vitro simulated gastric fluid digestion;

[0060] Figure 17 is a model fitting curve of the release of the MCT microcapsules during in vitro simulated intestinal fluid digestion. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the present application, the present application will be further described in conjunction with specific embodiments.

[0062] Example 1

[0063] Take 14.21 g of the composite wall material, of which 3.67 g of inulin and 10.54 g of whey protein, dissolve in 100 mL of distilled water, and stir at a temperature of 60°C for 10-30 min until dissolved uniformly;

[0064] Then add the core material of carbon chain fatty acid triglyceride, with a core wall ratio of 1:1.08, then add 0.4 g of the compound emulsifier, which contains 0.2 g of monoglyceride and 0.2 g of sodium carboxymethyl cellulose, continue to emulsify at a temperature of 60°C, and continue to stir uniformly to form a primary emulsion;

[0065] Further homogenize the primary emulsion under high pressure, with a homogenization condition of 40 Mpa, 2 times, and then spray dry to obtain the MCT-containing microcapsules, with an inlet air temperature of 185.47°C and a sample feeding speed of 14.73 mL / min.

[0066] Example 2

[0067] Take 14 g of the composite wall material, of which 10.5 g of whey protein and 3.5 g of inulin, dissolve in 100 mL of distilled water, and stir at a temperature of 60°C for 10-30 min until dissolved uniformly, then add 14 g of the core material MCT, and then add the compound emulsifier, including 0.2 g of monoglyceride and 0.2 g of sodium carboxymethyl cellulose, emulsify at temperatures of 50°C, 55°C, 60°C, 65°C, and 70°C, respectively, to prepare microcapsules, and continue to stir uniformly to form a primary emulsion; further homogenize the primary emulsion under high pressure, with a homogenization condition of 40 Mpa, 2 times, and then spray dry to obtain the MCT-containing microcapsules, with an inlet air temperature of 185°C and a sample feeding speed of 15 mL / min.

[0068] The embedding rate of the obtained MCT microcapsules was determined, and the embedding rate at different emulsification temperatures is shown in Table 1.

[0069] The results are shown in Figure 1.

[0070] Table 1: Embedding rate of MCT product at different emulsification temperatures

[0071] Emulsification temperature (°C) Embedding rate (%) 50 91.88±0.17 55 93.68±0.06 60 95.08±0.06 65 94.54±0.08 70 93.87±0.10

[0072] As can be seen from Figure 1, as the emulsification temperature continuously increases, the microcapsule embedding rate also shows an upward trend. When the emulsification temperature reaches 60°C, the microcapsule embedding rate reaches a maximum, and as the temperature continues to rise, the embedding rate shows a downward trend. The possible reason is that too low emulsification temperature will cause incomplete emulsification, and the formed emulsion is not uniform, causing the spray drying instrument to be blocked, and too high temperature will also affect the stability of the emulsion, causing the embedding rate to decrease.

[0073] Example 3

[0074] Under the premise that the raw material ratio is the same as that of Example 2, the emulsification temperature is fixed at 65°C, the spray drying feed rate is 15 mL / min, and only the air inlet temperature of spray drying is changed, the air inlet temperature is 180°C, 183°C, 185°C, 187°C, and 190°C respectively to prepare microcapsules, and the embedding rate is determined, and the results are shown in Table 2 and Figure 2.

[0075] Table 2: Embedding rate of MCT product at different air inlet temperatures of spray drying

[0076] Spray drying inlet temperature (°C) Embedding rate (%) 180 90.16±0.13 183 92.21±0.08 185 94.63±0.15 187 93.61±0.11 190 92.68±0.15

[0077] As can be seen from Figure 2, as the air inlet temperature of spray drying continuously increases, the microcapsule embedding rate also increases, and when the air inlet temperature of spray drying reaches 185°C, the microcapsule embedding rate reaches a maximum, and after that, as the air inlet temperature increases, the embedding rate begins to gradually decrease.

[0078] Too low air inlet temperature of spray drying may cause incomplete drying, water content, and other problems, and too high temperature may cause the surface of the microcapsule to be concave, and even cause the formed microcapsule to be broken, affecting the embedding rate of the product.

[0079] Example 4

[0080] Under the premise that the ratio of each raw material is the same as that of Example 2, the emulsification temperature is fixed at 65°C, the inlet air temperature of spray drying is 185°C, and only the feed speed of spray drying is changed, which is set at 10 mL / min, 13 mL / min, 15 mL / min, 17 mL / min, and 20 mL / min respectively to prepare microcapsules, and the embedding rate is determined. The embedding rate results under each condition are shown in Table 3 and Figure 3 .

[0081] Table 3 MCT product embedding rate under different spray drying sample speeds

[0082] Spray drying sample speed (mL / min) Embedding rate (%) 10 90.89±0.19 13 92.93±0.14 15 94.53±0.17 17 91.66±0.17 20 89.65±0.14

[0083] As can be seen from Figure 3, as the spray drying sample speed increases, the product embedding rate also gradually increases, when the spray drying sample speed reaches 15 mL / min, the microcapsule embedding rate reaches the maximum, and further increasing the spray drying sample speed causes the embedding rate to decrease. When the spray drying feed speed is too low, it is easy to cause the nozzle of the spray dryer to be blocked, reducing the spray drying efficiency; while the sample speed is too high, it will cause incomplete spray drying, increase waste liquid, waste raw materials, and low efficiency.

[0084] Example 5

[0085] Take 14 g of composite wall material, and control the weight ratio of whey protein to inulin in the composite wall material to be 4:1, 3:1, 2:1, 1:1, and 1:2 respectively. Then the composite wall material is dissolved in 100 mL of distilled water, and stirred at 60°C for 10-30 min until it is uniformly dissolved. Add 14 g of core material MCT, 0.2 g of monoglyceride, and 0.2 g of sodium carboxymethyl cellulose, and emulsify at 60°C. The other process conditions are the same as those of Example 1 to prepare MCT-containing microcapsules, and the embedding rate of the microcapsules is determined. The results are shown in Table 4 and Figure 4.

[0086] Table 4 Effect of composite wall material composition ratio on microcapsule embedding rate

[0087] Whey protein: inulin (w / w) Embedding rate (%) 4:1 84.12±0.65 3:1 92.80±0.79 2:1 87.38±0.98 1:1 84.12±1.07 1:2 82.21±0.56

[0088] As can be seen from Figure 4, as the amount of inulin increases, the MCT microcapsule embedding rate shows a trend of first increasing and then decreasing, when the whey protein:inulin is 3:1, the MCT microcapsule embedding rate reaches the maximum, and then the embedding rate begins to decrease as the proportion of inulin continues to increase.

[0089] The addition of inulin in whey protein can form a dense shell structure with whey protein due to the small molecular weight of inulin itself and its gelation property. However, when the amount of inulin is too large, the viscosity of the emulsion is too large, which is not conducive to the later spray drying, resulting in a decrease in the embedding rate.

[0090] Example 6

[0091] The complex wall material 14 g, in which the weight ratio of whey protein to inulin is 3:1, is then dissolved in 100 mL of distilled water, and the complex wall material is stirred at a temperature of 60°C for 10-30 min until it is uniformly dissolved. The weight ratio of the core material MCT to the complex wall material is controlled to be 1:0.5, 1:1, 1:1.5, 1:2, and 1:2.5, respectively. Then, 0.2 g of monoglyceride and 0.2 g of sodium carboxymethyl cellulose are added. The other process conditions are the same as in Example 1. Microcapsules are prepared, and the embedding rate of the microcapsules is determined. The results are shown in Table 5 and Figure 5.

[0092] Table 5: Embedding rate of MCT microcapsules under different core-to-wall ratios

[0093] MCT: complex wall material (w / w) Embedding rate (%) 1:0.5 88.67±0.18 1:1 94.41±0.24 1:1.5 95.06±0.17 1:2 95.06±0.33 1:2.5 95.29±0.37

[0094] As can be seen from Figure 5, the embedding rate increases first and then gradually stabilizes with the increase in the amount of wall material. When the core-to-wall ratio is 1:1, the embedding rate of the MCT microcapsules reaches a maximum value. Thereafter, increasing the amount of wall material slightly increases the embedding rate, but the amplitude is small, which easily leads to waste of wall material.

[0095] Example 7

[0096] The amount of wall material is controlled to be 10 g, 12 g, 14 g, 16 g, and 18 g, respectively, and the weight ratio of whey protein to inulin is 3:1. The complex wall material is dissolved in 100 mL of distilled water, and the complex wall material is stirred at a temperature of 60°C for 10-30 min until it is uniformly dissolved. The same amount of MCT as the complex wall material is added. Then, 0.2 g of monoglyceride and 0.2 g of sodium carboxymethyl cellulose are added. The other process conditions are the same as in Example 1. Microcapsules are prepared, and the embedding rate of the microcapsules is determined. The results are shown in Table 6 and Figure 6.

[0097] Table 6: Embedding rate of MCT microcapsules under different amounts of wall material

[0098] Wall material addition amount (g / 100 mL) Embedding rate (%) 10 83.96±1.10 12 87.37±0.75 14 93.57±0.69 16 88.96±0.70 18 85.23±0.82

[0099] As can be seen from FIG. 6, the embedding rate increases first and then decreases with the increase of the amount of wall material. When the amount of wall material is 14 g, the embedding rate of the MCT microcapsule reaches the maximum value. When the amount of wall material continues to increase, the embedding rate begins to decrease. When the amount of wall material is too low, the moisture content in the microcapsule emulsion is large, and the microcapsule spray drying is not complete, and the embedding rate of the microcapsule is low. When the amount of wall material is too high, the viscosity of the emulsion increases, which is not conducive to homogenization and spray drying, resulting in a decrease in the microencapsulation efficiency, and the microcapsule product is easy to coking during spray drying, which affects the product quality, therefore the optimal amount of wall material is 14 g per 100 mL -1 .

[0100] Example 8

[0101] Take 14 g of composite wall material, and the weight ratio of whey protein to inulin is 3:1. Dissolve the composite wall material in 100 mL of distilled water, and stir at 60℃ for 10-30 min until it is uniformly dissolved. Add 14 g of medium-chain fatty acid triglyceride, and add 0.2 g of composite emulsifier per 100 mL -1 , 0.3 g of composite emulsifier per 100 mL -1 , 0.4 g of composite emulsifier per 100 mL -1 , 0.5 g of composite emulsifier per 100 mL -1 , and 0.6 g of composite emulsifier per 100 mL -1 , wherein the weight ratio of monoglyceride to sodium carboxymethyl cellulose in the composite emulsifier is 1:1, and the other process conditions are the same as in Example 1. Prepare the microcapsule, and measure the embedding rate of the microcapsule. The results are shown in Table 7 and FIG. 7.

[0102] Table 7: Embedding rate of MCT microcapsule under different amounts of emulsifier

[0103] Emulsifier addition amount (g / 100 mL) Embedding rate (%) 0.2 86.73±0.43 0.3 88.16±0.54 0.4 92.77±0.07 0.5 90.22±0.29 0.6 88.28±0.34

[0104] As can be seen from FIG. 7, when the amount of emulsifier is 0.4 g per 100 mL -1 , the embedding rate of the MCT microcapsule is the largest. When the amount of emulsifier continues to increase, the embedding rate begins to decrease. For the amount of emulsifier, too much emulsifier will also cause problems such as blockage during spray drying.

[0105] Example 9

[0106] Take the composite wall material 14 g, the weight ratio of whey protein to inulin is 3:1, dissolve the composite wall material in 100 g distilled water, constant temperature stirring at 60°C for 10-30 min until dissolved uniformly, add medium-chain fatty acid triglyceride 14 g, compound emulsifier 0.4 g, the weight ratio of monoglyceride to sodium carboxymethyl cellulose is 2:1, 3:2, 1:1, 1:2, 2:3 respectively, other process conditions are the same as example 1, microcapsules are prepared, and the embedding rate of the microcapsules is measured, and the results are shown in table 8 and figure 8.

[0107] Table 8 embedding rate of MCT microcapsules under different emulsifier ratio

[0108] Monoglyceride: sodium carboxymethyl cellulose (w / w) Embedding rate (%) 2:1 89.59±0.54 3:2 90.35±0.30 1:1 91.87±0.24 1:2 89.59±0.17 2:3 88.60±0.12

[0109] As can be seen from figure 8, the ratio between monoglyceride and sodium carboxymethyl cellulose has no obvious effect on the embedding rate of microcapsules, with the increase or decrease of sodium carboxymethyl cellulose, the embedding rate of functional oil microcapsules shows a trend of first rising and then falling, when the ratio of monoglyceride to sodium carboxymethyl cellulose is 1:1, the embedding rate of MCT microcapsules reaches the highest.

[0110] Example 10 (particle size analysis of microcapsules)

[0111] The MCT microcapsules with slow-release performance prepared in example 1 of the present application are used as experimental samples for determination.

[0112] (1) The particle size of microcapsules is one of the important indicators to measure its quality, the larger the particle size of microcapsules, the more difficult to dissolve, on the contrary, the smaller the particle size, the better the dissolution performance. The particle size of the MCT-containing microcapsules of the present application mainly distributes between 0.200um-5.000um, showing normal distribution, uniform distribution, and the average particle size is (0.489±0.000)um, as shown in figure 9.

[0113] (2) The surface structure of MCT microcapsules is analyzed by scanning electron microscope, and the results are shown in figure 10.

[0114] As can be seen from figure 10, the microcapsules are ellipsoidal, the surface is smooth, and there is no obvious adhesion, which shows that the embedding effect is good; part of the microcapsule surface is slightly concave, but there is no crack or hole, and the concave is caused by the instability of the machine in the process of spray drying.

[0115] (3) The MCT microcapsules are subjected to differential scanning calorimetry (DSC) scanning analysis, and the results are shown in figure 11.

[0116] From the figure, the phase transition starting temperature of whey protein and inulin is 101.48℃, 61.58℃ respectively, the endothermic peak is 128.99℃, 66.49℃ respectively, the phase transition starting temperature of MCT microcapsule is 133.19℃, the endothermic peak temperature is 147.58℃; before the phase transition starting temperature, the sample is in a glass state, the structure is stable, the phase transition temperature of MCT microcapsule is higher, which indicates that its thermal stability is better, and it can still maintain the structure integrity in the process of conventional heat processing.

[0117] Example 11 (determination of the embedding rate of MCT microcapsule)

[0118] The MCT microcapsule with sustained-release performance obtained by the preparation of Example 1 of the application is used as the experimental sample for determination.

[0119] (1) Determination of surface oil content

[0120] Accurately take 2 g of MCT microcapsule product into a conical flask, add 25 mL of petroleum ether and shake for 5 min, pour the mixed solution into a funnel and filter, and wash with 25 mL of petroleum ether, collect the filtrate in a dry round-bottom flask until the mass is constant, then rotary evaporate to dryness, and then place the round-bottom flask in a vacuum drying oven at 60℃ until the mass is constant. Weigh and calculate the surface oil content.

[0121] (2) Determination of total oil content

[0122] Accurately take 2 g of MCT microcapsule sample, add 10 mL of hydrochloric acid solution and mix well, place the flask in a 70℃ water bath and hydrolyze for 40 min, shake the flask every 10 min, cool to room temperature after hydrolysis. After cooling, add 10 mL of 95% ethanol and mix well, transfer to a separatory funnel, rinse the flask with a mixture of petroleum ether and ethyl ether, and let the solution stand in the separatory funnel until it separates into layers. Rotary evaporate to dryness, and the final residue is the total oil content in the microcapsule.

[0123] Example 12 (determination of basic indicators of MCT microcapsule)

[0124] The MCT microcapsule with sustained-release performance obtained by the preparation of Example 1 of the application is used as the experimental sample for determination.

[0125] (1) Moisture content determination refers to GB 590009.3-2160, using direct drying method;

[0126] (2) Solubility determination refers to the method of Ma Mingyue et al. with slight modification;

[0127] (3) MCT microcapsule bulk density determination: accurately take a certain amount of microcapsule sample in a dry and clean funnel with scale, determine its volume, and the ratio of mass and volume is the bulk density of the sample;

[0128] (4) MCT microcapsule angle of repose determination: take 5g of microcapsule sample, make it slowly slide through the funnel and naturally accumulate on the horizontal disc, measure the accumulation height and powder pile radius.

[0129] Angle of repose = arctan (h / r); h - accumulation height; r - powder pile radius

[0130] The basic index determination results of the MCT microcapsule containing MCT microcapsule are shown in Table 9.

[0131] Table 9 MCT microcapsule basic index determination results

[0132] Item Result Total oil content (%) 49.04±0.02 Embedding rate (%) 96.23±0.01 Moisture content (%) 2.02±0.04 Bulk density (g / cm3) 0.25±0.01 Angle of repose (°) 33.68±0.39 Solubility (%) 93.06±0.23

[0133] As can be seen from the table, the total oil content of the microcapsule is (49±0.02)%, the embedding rate is (96.23±0.01)%, the embedding effect is good; the moisture content of the microcapsule is (2.02±0.04)%, the moisture content is low, the drying is sufficient, and the mildew is not easy to occur; the bulk density is (0.25±0.01)%, the angle of repose is (33.68±0.39)%, the angle of repose is between 30-40°, which indicates that the sample has good fluidity, the solubility is (93.06±0.23)%, and the solubility is good.

[0134] Example 13 (MCT microcapsule storage stability)

[0135] The MCT microcapsule with sustained-release performance obtained by the preparation of Example 1 of the application was used as the experimental sample for determination.

[0136] (1) Determination of peroxide value (POV) in accelerated storage experiment

[0137] The MCT oil and the MCT microcapsule were simultaneously placed in a 60℃ oven for storage for 30d, and the sample POV value was determined every 5d, and the POV value determination method referred to GB 5009.227-2016.

[0138] The results of the POV value changes of MCT crude oil and MCT microcapsules are shown in Figure 12. As shown in Figure 12, the initial POV value of MCT crude oil is 0.60 mmol / kg, and the initial POV value of MCT microcapsules is 0.67 mmol / kg. The POV value increases by 0.07 mmol / kg after microencapsulation. The reason for the increase may be that the sample was exposed to air during the preparation process. In addition, the processes of constant temperature water bath, high pressure homogenization and spray drying also have a certain influence on the POV value of the microcapsules. After 30 days, the POV value of MCT crude oil increases to 3.50 mmol / kg, which is 2.90 mmol / kg higher than that 30 days ago. The POV value of MCT microcapsules increases to 2.30 mmol / kg, which is 1.63 mmol / kg higher than that 30 days ago.

[0139] (2) Acid value determination

[0140] The MCT oil and MCT microcapsules were simultaneously placed in a 60°C oven for storage for 30 days, and the acid value of the sample was determined every 5 days. The acid value determination method refers to GB5009.229-2016.

[0141] The acid value changes of MCT crude oil and MCT microcapsules are shown in Figure 13.

[0142] As shown in Figure 13, the initial acid value of MCT crude oil is 0.26 mg / g, and the initial acid value of MCT microcapsules is 0.30 mg / g. The acid value increases by 0.04 mg / g after microencapsulation. After 30 days, the acid value of MCT crude oil increases to 0.84 mg / g, which is 0.58 mg / g higher than that 30 days ago. The acid value of MCT microcapsules increases to 0.68 mg / g, which is 0.38 mg / g higher than that 30 days ago.

[0143] The POV value and acid value of MCT crude oil increase slowly compared with other oils and fats. Even at 60°C, the POV value and acid value change little. The main reason may be that MCT mainly contains saturated fatty acids, which have better oxidation stability than unsaturated fatty acids and are not easy to be oxidized. After 30 days, the POV value and acid value of MCT microcapsules are lower than those of MCT crude oil, indicating that the complex wall material has a protective effect on MCT oil embedding, which improves the oxidation stability of MCT microcapsules.

[0144] In addition, the National Food Safety Standard Vegetable Oil stipulates that the limit standards of POV value and acid value of edible vegetable oil are 9.85 mmol / kg and 3 mg / g, respectively. Researches prove that the POV value and acid value of the MCT-containing microcapsules prepared in the application still meet the limit standards after 30 days of accelerated oxidation.

[0145] (3) Oil retention rate determination

[0146] The MCT microcapsules were placed in a 60°C oven for storage for 30 days, and the surface oil content of the samples was determined every 5 days. The surface oil content determination was the same as in Example 9.

[0147] Oil retention rate = (m-m1) / (m-m0) x 100%

[0148] m—initial total oil content of the microcapsules; m1—immediate surface oil content of the microcapsules; m0—initial surface oil content of the microcapsules.

[0149] The oil retention rate results of the MCT microcapsules in the accelerated storage experiment are shown in Figure 14;

[0150] As is known, the oil retention rate of microcapsules is also one of the important indicators for measuring their storage stability. As can be seen from Figure 14, the oil retention rate of the MCT microcapsules showed a downward trend with the increase of storage time. This is because the compactness of the microcapsule wall material changes due to the influence of external temperature, air, moisture and other factors during storage, causing the oil embedded in the wall material to exude, resulting in a decrease in oil retention rate. However, the decrease in oil retention rate of the microcapsules was relatively slow, and the MCT oil retention rate decreased to 93.39% at 30 days, only decreasing by 6.61%. This indicates that the prepared MCT microcapsules have good storage stability at high temperatures, but long-term placement in a high-temperature environment should still be avoided during storage.

[0151] Example 14 (In vitro simulation of digestion of MCT microcapsules)

[0152] (1) The preparation of gastric juice and intestinal juice for in vitro simulation of digestion was slightly modified according to the method of Chew et al.

[0153] Simulated gastric juice: accurately weigh 2 g of sodium chloride, dissolve in 900 mL of deionized water, adjust the pH to 1.2 with HCl, then add 3.2 g of pepsin, and dilute to 1000 mL.

[0154] Preparation of intestinal juice: accurately weigh 0.68 g of potassium dihydrogen phosphate, dissolve in 900 mL of deionized water, adjust the pH to 6.8 with NaOH, add 10 g of trypsin, and dilute to 1000 mL; the prepared digestion solution is stored at 4°C.

[0155] (2) In vitro simulation of the digestion process: weigh 5 g of MCT microcapsules in 50 mL of gastric juice, stir at 100 r / min in a 37°C water bath for 2 h, take 5 mL of the mixed digestion solution every 30 min, and measure the core material release rate after enzyme inactivation; after 2 h of digestion in the gastric juice, adjust the pH to 6.8 with NaOH to inactivate pepsin, add 50 mL of intestinal juice, stir at 100 r / min in a 37°C water bath for 2 h, take 5 mL of the mixed digestion solution every 30 min, and measure the core material release rate after enzyme inactivation.

[0156] Determination of core material release rate: transfer the mixed digestion solution after enzyme inactivation into a separatory funnel, add 25 mL of petroleum ether for extraction, repeat the extraction three times, combine the organic phases, and remove the petroleum ether by rotary evaporation to obtain the oil as the core material released during the digestion process of MCT microcapsules.

[0157] Core material release rate = (m / m0) x 100%;

[0158] Wherein: m is the oil released during the digestion process; m0 is the total oil content of MCT microcapsules;

[0159] The results of the cumulative core material release rate of MCT microcapsules in the in vitro simulation of the digestion process are shown in Figure 15.

[0160] The MCT microcapsules in this test belong to simulated gastric juice digestion in the first 120 min, and the core material release rate of MCT microcapsules is 30.02%, mainly due to the preliminary hydrolysis of whey protein under the action of pepsin, but inositol is difficult to be decomposed in the gastric juice environment, and inositol itself has a certain gelatinous nature, which tightly combines with whey protein, preventing the specific combination between pepsin and protein, so that only a small number of microcapsule shells are broken in the acidic environment, and the core material release rate is relatively low.

[0161] In the subsequent 120 min, the MCT microcapsules enter the intestinal juice for digestion, and the core material release rate reaches 84.53%, which may be due to the fact that the intestinal juice contains trypsin, lipase, and amylase, which can not only decompose and digest proteins, fats, and starches, but also can destroy the force between sugars and proteins, causing the density of the microcapsule shell to decrease, and a large amount of core material to be released, thereby improving the release rate.

[0162] (3) Because of the different metabolic rates and food characteristics of each individual, the digestion time of different foods in different individuals varies greatly, so the digestion time of 2-3 h is usually selected for the stomach and intestinal stages of the digestion model.

[0163] The release kinetics of MCT microcapsules in artificial gastric juice and intestinal juice were analyzed, and the zero-order model, Ritger-peppas model, and Higuchi model were used for fitting, respectively. The fitting curves are shown in Figures 16-17, and the fitting equations and regression coefficients are shown in Table 10.

[0164] Table 10 Fitting equations and regression coefficients for the release of MCT microcapsules in artificial gastric juice and intestinal juice

[0165]

[0166] From Table 10 and Figures 16-17, by comparing the R2 of the three models for the in vitro simulated gastric juice and intestinal juice digestion process, the Ritger-peppas model R2>zero-order model R2>Higuchi model R2, so the release model of MCT microcapsules in both simulated gastric juice and intestinal juice digestion process belongs to the Ritger-peppas model.

[0167] In the simulated gastric juice digestion process, n=0.70, and in the simulated intestinal juice digestion process, n=0.60, both of which are within the range of 0.45-0.89, so whether in simulated gastric juice or intestinal juice, the release mechanism of MCT microcapsules belongs to the diffusion and matrix erosion synergy in the non-Fick diffusion process. The whole process can be summarized as follows: the MCT oil on the surface of the shell is first exposed to artificial gastric juice and intestinal juice and is dissolved and digested, and as the shell of the microcapsule is broken, the MCT oil inside the shell continuously diffuses outwards into the digestive juice until the release is complete, indicating that after MCT is microencapsulated, the release of oil is restricted by the shell structure, resulting in slow release and achieving sustained-release effect.

[0168] From the above data, it can be seen that after MCT is made into a product in the form of microcapsules, the release of MCT in the gastrointestinal tract can be delayed, achieving a sustained-release effect, thereby avoiding the gastrointestinal problems caused by direct consumption of MCT.

[0169] In summary, the final release rate of MCT microcapsules in the entire in vitro simulated gastric juice and intestinal juice digestion process reaches 84.53%, with good release performance and good sustained-release effect.

Claims

1. A method for improving the sustained-release properties of medium-chain fatty acid triglycerides, characterized by, The method comprises the following steps: Take 14.21 g of composite wall material, wherein 3.67 g of inulin and 10.54 g of whey protein are dissolved in 100 mL of distilled water, and stirred at a temperature of 60 DEG C for 10-30 min until uniformly dissolved; then add core material medium-chain fatty acid triglyceride, wherein the core wall ratio is 1:1.08, then add 0.4 g of compound emulsifier, wherein 0.2 g of monoglyceride and 0.2 g of sodium carboxymethyl cellulose are contained, continue to emulsify at a temperature of 60 DEG C, and continue to stir uniformly to form a primary emulsion; the primary emulsion is further subjected to high-pressure homogenization, the homogenization conditions are 40 Mpa, and the homogenization is performed twice, then spray drying is performed, and MCT-containing microcapsules are obtained, wherein the inlet air temperature of spray drying is 185.47 DEG C, and the sample feeding speed is 14.73 mL / min.

2. The medium-chain fatty acid triglyceride-containing microcapsules prepared according to the method of claim 1.

3. The medium-chain fatty acid triglyceride-containing microcapsules prepared according to the method of claim 1 are used for preparing drugs for preventing or treating diabetes.

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