Alpha-ethyl linolenate microcapsule and preparation method thereof

Abstract

The invention belongs to the technical field of microcapsules, and particularly relates to an alpha-ethyl linolenate microcapsule and a preparation method thereof. The invention provides an alpha-ethyl linolenate microcapsule which comprises a core material and a wall material, and the core material comprises alpha-ethyl linolenate; the wall material comprises soybean protein isolate, maltodextrin and microcrystalline cellulose; the mass ratio of the soybean protein isolate to the maltodextrin to the microcrystalline cellulose is (3: 1)-(1.2: 1); and the mass ratio of the core material to the wall material is 1: (2-3). The wall material composed of the soybean protein isolate, the maltodextrin and the microcrystalline cellulose is more effective in the aspect of enhancing the interface structure, so that the wall material has a better protection effect on unsaturated fatty acid.

Description

Technical Field

[0001] This invention belongs to the field of microencapsulation technology, specifically relating to an α-linolenic acid ethyl ester microcapsule and its preparation method. Background Technology

[0002] Alpha-linolenic acid (ALA) is a C-18n-3 polyunsaturated fatty acid with properties that regulate blood lipids, promote weight loss, lower blood pressure, prevent cardiovascular and cerebrovascular diseases, inhibit cancer, reduce inflammation, and have anti-aging effects. The human body lacks the ability to synthesize ALA, and its intake depends on a natural diet. Perilla seed oil contains over 60% ALA, higher than other ALA-rich oils such as flaxseed oil and sacha inchi oil.

[0003] The unsaturated nature of ALA makes it susceptible to oxidation and results in relatively low bioavailability in the human body. This necessitates the encapsulation of ALA by suitable carriers to enhance its antioxidant properties and bioactivity. Alpha-linolenate (AEL) exhibits better stability than ALA and shares similar physiological effects. Microencapsulation is the process of encapsulating micron-sized substances (wall material) within a coating on a polymer shell to protect the active compound (core material) from adverse environmental conditions, including strong light, oxygen, and high temperatures. It can also enhance the solubility and dispersion of fat-soluble components in aqueous solutions, improve texture and sensory perception, and reduce odor, thereby effectively expanding its potential applications in the food industry.

[0004] Various microencapsulation technologies have been studied, including spray drying, freeze drying, molecular encapsulation, and condensation. Among these, spray drying is the most widely used technology for encapsulating fat-soluble substances due to its low cost, high efficiency, and ease of industrial production. The encapsulation efficiency (EE) and function of spray-dried encapsulated unsaturated fatty acids mainly depend on the properties of the oil-in-water (O / W) emulsion and the selection of suitable wall materials.

[0005] Existing technology discloses a high-content α-linolenic acid microcapsule and its manufacturing method. This method uses sodium octenyl succinate starch as the single wall material to encapsulate and emulsify α-linolenic acid. However, because the sodium octenyl succinate starch solution is high-concentration and low-viscosity, the encapsulation rate is low. Increasing its dosage to achieve better encapsulation results in excessively low oil content in the microcapsules. Summary of the Invention

[0006] The purpose of this invention is to provide ethyl α-linolenic acid microcapsules and a method for their preparation. The ethyl α-linolenic acid microcapsules provided by this invention have a high encapsulation efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides ethyl α-linolenic acid microcapsules, comprising a core material and a wall material, wherein the core material comprises ethyl α-linolenic acid;

[0009] The wall material comprises soy protein isolate, maltodextrin, and microcrystalline cellulose; the mass ratio of soy protein isolate, maltodextrin, and microcrystalline cellulose is 3:1 to 1.2:1.

[0010] The mass ratio of the core material to the wall material is 1:2 to 3.

[0011] Preferably, the α-linolenic acid ethyl ester includes at least one of perilla α-linolenic acid ethyl ester and linolenic acid α-linolenic acid ethyl ester.

[0012] Preferably, the encapsulation rate of the α-linolenic acid ethyl ester microcapsules is 70-85%.

[0013] This invention also provides a method for preparing α-linolenic acid ethyl ester microcapsules as described above, comprising the following steps:

[0014] The wall material and water are mixed to obtain an aqueous phase;

[0015] The core material and emulsifier are mixed to obtain the oil phase;

[0016] The aqueous phase and oil phase are mixed and emulsified to obtain a crude emulsion;

[0017] The crude emulsion was homogenized and spray-dried sequentially to obtain the α-linolenic acid ethyl ester microcapsules.

[0018] Preferably, the temperature at which the wall material and water are mixed is 45–55°C; and the solid content of the aqueous phase is 6.3–7.1%.

[0019] Preferably, the emulsifier includes Tween-80, Span-80, and sodium caseinate; the mass ratio of Tween-80, Span-80, and sodium caseinate is 1:1:1.

[0020] The emulsifier is present at 1-2% of the core material mass.

[0021] Preferably, the process of mixing the aqueous phase and the oil phase is as follows: the oil phase is dripped into the aqueous phase under stirring conditions.

[0022] Preferably, the emulsification temperature is 45–60°C; the emulsification is carried out under stirring conditions, and the stirring time is 1–1.5 h.

[0023] Preferably, the homogenization rotation speed is 8000-10000 rpm and the time is 6-8 min.

[0024] Preferably, the conditions for spray drying include: an inlet air temperature of 180±5℃, an atomizer frequency of 60Hz, and a flow rate of 400~600mL / min.

[0025] This invention provides ethyl α-linolenic acid microcapsules, comprising a core material and a wall material. The core material comprises ethyl α-linolenic acid; the wall material comprises soy protein isolate, maltodextrin, and microcrystalline cellulose; the mass ratio of soy protein isolate, maltodextrin, and microcrystalline cellulose is 3:1 to 1.2:1; and the mass ratio of the core material to the wall material is 1:2 to 3.

[0026] This invention uses soy protein isolate, maltodextrin, and microcrystalline cellulose as wall materials. Soy protein isolate (SPI) possesses excellent film-forming properties and biocompatibility, effectively protecting the core material and preventing contact with the external environment. It is also inexpensive and widely available. Maltodextrin (MD) exhibits good solubility, dispersibility, thermal stability, and antioxidant properties. It is low-cost, safe, and harmless, and can improve the mechanical properties and stability of the microcapsule powder. Microcrystalline cellulose can form a dense and uniform membrane structure, effectively encapsulating the core material and preventing leakage or deterioration. The membrane formed by microcrystalline cellulose has a certain controlled-release capability, allowing for the slow release of the core material based on environmental conditions (such as pH and temperature). The wall material composed of soy protein isolate, maltodextrin, and microcrystalline cellulose is more effective in strengthening the interfacial structure, thus providing better protection for unsaturated fatty acids.

[0027] This invention also provides a method for preparing α-linolenic acid ethyl ester (AEL) microcapsules as described in the above-mentioned technical solution. This invention employs spray drying combined with emulsification technology for AEL microencapsulation. Simultaneously, the preparation process of AEL microcapsules is optimized through single-factor and response surface methodology experiments, and the influence of microencapsulation on the physicochemical properties of AEL is investigated. This invention is of great significance for the development of unsaturated fatty acid microcapsule powders and for improving their stability and functionality, as well as their potential applications in the food industry. Attached Figure Description

[0028] Figure 1 The effect of wall material ratio on the encapsulation efficiency of AEL microcapsules;

[0029] Figure 2 The effect of core-to-wall ratio on the encapsulation efficiency of AEL microcapsules;

[0030] Figure 3 The effect of homogenization time on the encapsulation efficiency of AEL microcapsules;

[0031] Figure 4 The effect of temperature on the encapsulation efficiency of AEL microcapsules;

[0032] Figure 5 In response to the curved surface 3D model and contour lines;

[0033] Figure 6 Here is a SEM image of the AEL microcapsules obtained in Example 5;

[0034] Figure 7 The particle size distribution of AEL microcapsules obtained in Example 5;

[0035] Figure 8 Fourier transform infrared spectroscopy analysis of the AEL microcapsules obtained in Example 5;

[0036] Figure 9 X-ray diffraction spectroscopy analysis of the AEL microcapsules obtained in Example 5;

[0037] Figure 10 Thermogravimetric analysis of the AEL microcapsules obtained in Example 5;

[0038] Figure 11 The simulated gastric and intestinal digestion curves of the AEL microcapsules obtained in Example 5 are shown.

[0039] Figure 12 The peroxide value curves of AEL and AEL microcapsules obtained in Example 5 after storage at 60°C for 13 days are shown. Detailed Implementation

[0040] This invention provides ethyl α-linolenic acid microcapsules, comprising a core material and a wall material, wherein the core material comprises ethyl α-linolenic acid;

[0041] The wall material comprises soy protein isolate, maltodextrin, and microcrystalline cellulose; the mass ratio of soy protein isolate, maltodextrin, and microcrystalline cellulose is 3:1 to 1.2:1.

[0042] The mass ratio of the core material to the wall material is 1:2 to 3.

[0043] In this invention, the α-linolenic acid ethyl ester preferably includes at least one of perilla α-linolenic acid ethyl ester and linolenic acid α-linolenic acid ethyl ester.

[0044] In this invention, the mass ratio of soy protein isolate, maltodextrin and microcrystalline cellulose is 3:1 to 1.2:1, specifically 3:1:1, 3:1.1:1 or 3:1.2:1.

[0045] In this invention, the mass ratio of the core material to the wall material is 1:2 to 3, specifically 1:2, 1:2.5 or 1:3.

[0046] In this invention, the encapsulation rate of the α-linolenic acid ethyl ester microcapsules is preferably 70-85%.

[0047] This invention also provides a method for preparing the α-linolenic acid ethyl ester microcapsules described in the above technical solution, comprising the following steps:

[0048] The wall material and water are mixed to obtain an aqueous phase;

[0049] The core material and emulsifier are mixed to obtain the oil phase;

[0050] The aqueous phase and oil phase are mixed and emulsified to obtain a crude emulsion;

[0051] The crude emulsion was homogenized and spray-dried sequentially to obtain the α-linolenic acid ethyl ester microcapsules.

[0052] This invention mixes wall material and water to obtain an aqueous phase.

[0053] In this invention, the mixing temperature of the wall material and water is preferably 45–55°C, specifically 45°C, 50°C, or 55°C; the mixing is preferably carried out under stirring conditions. This invention does not have a specific limitation on the stirring time, as long as the wall material is completely dissolved. In this invention, the solid content of the aqueous phase is preferably 6.3–7.1%, specifically 6.3%, 6.5%, 6.7%, 6.9%, 7.0%, or 7.1%.

[0054] This invention mixes the core material and the emulsifier to obtain an oil phase.

[0055] In this invention, the emulsifier preferably includes Tween-80, Span-80, and sodium caseinate; the mass ratio of Tween-80, Span-80, and sodium caseinate is preferably 1:1:1. In this invention, the mass of the emulsifier is preferably 1-2% of the core material mass, specifically 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, or 2.0%. In this invention, the mixing is preferably carried out under stirring conditions.

[0056] After obtaining the aqueous phase and the oil phase, the present invention mixes the aqueous phase and the oil phase and emulsifies them to obtain a crude emulsion.

[0057] In this invention, the preferred method for mixing the aqueous and oil phases is to add the oil phase dropwise into the aqueous phase under stirring conditions. In this invention, the emulsification temperature is preferably 45–60°C, specifically 45°C, 50°C, 55°C, or 60°C; the emulsification is preferably carried out under stirring conditions, and the stirring time is preferably 1–1.5 hours, specifically 1 hour, 1.2 hours, 1.3 hours, 1.4 hours, or 1.5 hours. In this invention, the total mass percentage (i.e., solids mass fraction) of the wall material and core material in the crude emulsion is preferably 10–12%, specifically 10%, 11%, or 12%.

[0058] After obtaining the crude emulsion, the present invention performs homogenization and spray drying on the crude emulsion in sequence to obtain the α-linolenic acid ethyl ester microcapsules.

[0059] In this invention, the preferred rotational speed for homogenization is 8000-10000 rpm, specifically 8000 rpm, 9000 rpm, or 10000 rpm; the preferred time is 6-8 min, specifically 6 min, 7 min, or 8 min.

[0060] In this invention, the preferred conditions for spray drying include: an inlet air temperature of 180±5℃, an atomizer frequency of 60Hz, and a flow rate of 400~600mL / min.

[0061] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0062] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0063] The characterization and testing involved in the following embodiments:

[0064] 1. Determination of embedding rate

[0065] (1) Calculation of surface oil and total oil

[0066] Surface oil content (W) s () indicates oil not encapsulated inside the wall material. Take 1g of microcapsule and place it in a 50mL centrifuge tube. Add 20mL of n-hexane and shake gently. Centrifuge at 4000rpm for 5min. Take the supernatant, filter it, and place it in a rotary evaporator flask. Evaporate at 50℃ until the n-hexane is completely removed to obtain the surface oil.

[0067] Total oil content (W) t The total oil is represented by the sum of the oil on the surface of the microcapsules and the oil in the microcapsule powder wall material. Accurately weigh 1g of microcapsules into a 50mL centrifuge tube, add 40mL of petroleum ether, stir magnetically at 50℃ for 1h, centrifuge at 4000rpm for 5min, filter the supernatant, and place it in a rotary evaporator flask for rotary evaporation at 50℃ until the petroleum ether is completely removed, thus obtaining the total oil.

[0068] (2) Calculation of embedding ratio

[0069] The encapsulation rate (D) is defined as the ratio of the amount of oil encapsulated inside the wall material to the total amount of oil in the microcapsules, and the calculation formula is shown in equation (1):

[0070]

[0071] 2. Structural characterization

[0072] (1) SEM analysis

[0073] The dried microcapsules were placed on the sample stage to ensure firm adhesion; the samples were sputter-coated with gold to a thickness of approximately 100 μm; the microstructure of the AEL microcapsules was observed and photographed by SEM at different magnifications under an accelerating voltage of 10 kV.

[0074] (2) Particle size analysis

[0075] The microcapsule sample to be tested was placed in a room temperature environment to allow it to be uniformly dispersed in distilled water. The particle size distribution of the microcapsules was measured using a laser particle size analyzer, and the obtained data were collected and analyzed.

[0076] (3) Fourier transform infrared spectroscopy (FTIR) analysis

[0077] Take an appropriate amount of dried microcapsules, mix them thoroughly with potassium bromide, and grind them evenly. Spread the mixed sample evenly on a tablet press and press it into a tablet. Scan the prepared potassium bromide tablet using a Fourier transform infrared spectroscopy (FTIR) spectrometer, with the scanning range set to 4000–400 cm⁻¹. -1 The scanning resolution was set to 4cm. -1 .

[0078] (4) X-ray diffraction (XRD) analysis

[0079] The crystal structure of the microcapsules was analyzed using X-ray diffraction. The sample was passed through a 100-mesh sieve, and a small amount was placed on the sample cap and pressed firmly. The voltage was set to 40.0 kV, the current to 30.0 mA, the scan rate to 2° / min, the scan range to 10°–80°, and the scan mode to continuous.

[0080] (5) Thermogravimetric analysis

[0081] Place an appropriate amount of microcapsules into a ceramic crucible. Set the temperature range to 25℃~600℃, the gas flow rate to 20mL / min, the heating rate to 10℃ / min, and nitrogen as the protective gas.

[0082] 3. In vitro sustained-release performance determination

[0083] (1) Simulated gastric fluid (SGF) release:

[0084] Prepare gastric and intestinal juices (see “Zhang Jiali, Zheng Jiexun, Ruan Fang, et al. Study on in vitro digestive properties of anthocyanin microcapsules and development of beverages [J]. Food and Fermentation Technology, 2024, 60(06):109-114”).

[0085] Weigh 2g of the microcapsule sample and dissolve it in 50mL of freshly prepared SGF solution. Adjust the pH to 1.20±0.05 with 1mol / L hydrochloric acid. Place the solution in a 37℃ constant temperature water bath and stir at 100r / min while simultaneously adding 0.2mol / L NaOH solution dropwise to maintain a constant pH. Record the NaOH consumption every 30 minutes until the reaction is complete. Calculate the acidity change based on the NaOH consumption to evaluate the digestive properties of the microcapsules in simulated gastric juice.

[0086] (2) Release of simulated intestinal fluid (SIF):

[0087] Weigh 2g of microcapsule sample and dissolve it in 50mL of freshly prepared SIF solution. Adjust the pH to 7.50±0.05 with 0.1mol / L sodium hydroxide solution. Place the solution in a 37.0℃ constant temperature water bath and stir at 100r / min while simultaneously adding 0.2mol / L sodium hydroxide solution dropwise to maintain a constant pH. Record the NaOH consumption every 30 minutes until the reaction is complete. Calculate the acidity change based on the NaOH consumption to evaluate the digestive characteristics of the microcapsules in simulated intestinal fluid.

[0088] (3) Determination of the percentage of free fatty acids

[0089] Based on the recorded NaOH volume, the release rate (R) of free fatty acids (FFAs) can be obtained, and the calculation formula is shown in equation (2):

[0090]

[0091] in:

[0092] a: Volume (L) of NaOH added to the core material for neutralization and release;

[0093] b: Molar concentration (mol / L) of sodium hydroxide solution;

[0094] c: Molecular weight of α-linolenic acid ethyl ester (g / mol);

[0095] d: Total weight (g) of lipids introduced into the reaction vessel.

[0096] 4. Determination of the oxidative stability of microcapsules

[0097] Extraction method of AEL from microcapsules: Weigh 5g of microcapsules, add 200mL of petroleum ether and mix for 4h. Stir the mixture with a magnetic stirrer for 2h. After stirring, filter the mixture and wash the filtrate three times with petroleum ether. Evaporate the oil-containing solvent phase at 60℃ and dry the residue to constant weight in a fume hood.

[0098] Peroxide value determination method: Microcapsules and AEL were placed in a brown bottle and stored at 60℃ for 13 days. 2g of microcapsules and 2g of AEL were taken every 3 days for determination. 2g of AEL sample was dissolved in a mixture of 30mL dichloromethane and glacial acetic acid (2:3, v / v), 1.0mL of saturated potassium iodide solution was added and shaken for 30s. The solution was placed in the dark for 3min, 100mL of deionized water was added, and titrated with 0.001mol / L NaS2O3, using 1% starch solution as an indicator, until the blue color disappeared. Peroxide value is expressed as mmol / kg. The PV calculation for embedded and unencapsulated AEL is shown in equation (3):

[0099]

[0100] in:

[0101] PV: Peroxide value of AEL, mmol / kg;

[0102] V: Sample titration volume, mL;

[0103] V0: Blank titration volume, mL;

[0104] C: Molar concentration of sodium thiosulfate solution, mol / L;

[0105] W: Weight of AEL, in g.

[0106] 5. Data Processing

[0107] All experiments were repeated three times, and results are expressed as mean ± standard deviation. Data analysis was performed using Microsoft Excel 2019; graphs were plotted using Origin 2021; and parameter optimization and analysis of variance for response surface experiments were performed using Design-Expert 8.0.6.

[0108] Example 1

[0109] Soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) were dissolved in deionized water and stirred at 50°C using a thermostatic magnetic stirrer until dissolved to prepare an aqueous phase with a solid content of 6.7%.

[0110] Weigh out the emulsifier (Tween-80, Span-80 and sodium caseinate in a mass ratio of 1:1:1) and add it to ethyl perilla α-linolenic acid (AEL). Stir until the emulsifier is dissolved to obtain the oil phase.

[0111] The oil phase was added dropwise to the aqueous phase using a dropper, while simultaneously stirring and emulsifying at 50°C. The oil and aqueous phases were thoroughly mixed and stirred for 1 hour to obtain a crude emulsion with a solids mass fraction of 10% and a core-to-wall ratio of 1:2.

[0112] The crude emulsion was transferred to a high-speed disperser and homogenized at 10,000 rpm for 8 min. The resulting emulsion was then spray-dried. The spray drying (SD) conditions were: inlet air temperature of 180±5℃, atomizer frequency of 60Hz, and flow rate of 400mL / min.

[0113] The effect of wall material ratios SPI:MD:MCC (3:3:1, 3:2:1, 3:1.5:1, 3:1.2:1, 3:1:1) on the encapsulation efficiency of microcapsule powder was verified.

[0114] Example 2

[0115] Soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) were dissolved in deionized water and stirred at 50°C using a thermostatic magnetic stirrer until dissolved to prepare an aqueous phase with a wall material ratio of SPI:MD:MCC of 3:1:1 and a solid content of 6.7%.

[0116] Weigh out the emulsifier (Tween-80, Span-80 and sodium caseinate in a mass ratio of 1:1:1) and add it to the perilla α-linolenic acid ethyl ester microcapsules (AEL). Stir until the emulsifier is dissolved to obtain the oil phase.

[0117] The oil phase was added dropwise to the aqueous phase using a dropper, while simultaneously stirring and emulsifying at 50°C to ensure thorough mixing of the oil and aqueous phases. The mixture was stirred for 1 hour to obtain a crude emulsion with a solid content of 10%.

[0118] The crude emulsion was transferred to a high-speed disperser and homogenized at 10,000 rpm for 8 min. The resulting emulsion was then spray-dried. The spray drying (SD) conditions were: inlet air temperature of 180±5℃, atomizer frequency of 60Hz, and flow rate of 400mL / min.

[0119] To verify the effect of core-to-wall ratio (1:1, 2:3, 1:2, 2:5, 1:3) on the encapsulation efficiency of microcapsule powder.

[0120] Example 3

[0121] Soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) were dissolved in deionized water and stirred at 50°C using a thermostatic magnetic stirrer until dissolved to prepare an aqueous phase with a wall material ratio of SPI:MD:MCC of 3:1:1 and a solid content of 6.7%.

[0122] Weigh out the emulsifier (Tween-80, Span-80 and sodium caseinate in a mass ratio of 1:1:1) and add it to the perilla α-linolenic acid ethyl ester microcapsules (AEL). Stir until the emulsifier is dissolved to obtain the oil phase.

[0123] The oil phase was added dropwise to the aqueous phase using a dropper, while simultaneously stirring and emulsifying at 50°C. The oil and aqueous phases were thoroughly mixed and stirred for 1 hour to obtain a crude emulsion with a solids mass fraction of 10% and a core-to-wall ratio of 2:5.

[0124] The crude emulsion was transferred to a high-speed disperser and homogenized at a speed of 10,000 rpm. The resulting emulsion was then spray-dried under the following conditions: inlet air temperature of 180±5℃, atomizer frequency of 60Hz, and flow rate of 400mL / min.

[0125] The effect of homogenization time (4 min, 6 min, 8 min, 10 min, 12 min) on the encapsulation rate of microcapsule powder was verified.

[0126] Example 4

[0127] Soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) were dissolved in deionized water and stirred at 50°C using a thermostatic magnetic stirrer until dissolved to prepare an aqueous phase with a wall material ratio of SPI:MD:MCC of 3:1:1 and a solid content of 6.7%.

[0128] Weigh out the emulsifier (Tween-80, Span-80 and sodium caseinate in a mass ratio of 1:1:1) and add it to the perilla α-linolenic acid ethyl ester microcapsules (AEL). Stir until the emulsifier is dissolved to obtain the oil phase.

[0129] The oil phase was added dropwise to the aqueous phase using a dropper, and the mixture was stirred and emulsified until the oil and aqueous phases were fully mixed and stirred for 1 hour to obtain a crude emulsion with a solid mass fraction of 10% and a core-to-wall ratio of 2:5.

[0130] The crude emulsion was transferred to a high-speed disperser and homogenized at 10,000 rpm for 6 min. The resulting emulsion was then spray-dried. The spray drying (SD) conditions were: inlet air temperature of 180±5℃, atomizer frequency of 60Hz, and flow rate of 400mL / min.

[0131] The effect of emulsification temperature (40℃, 50℃, 60℃, 70℃, 80℃) on the encapsulation efficiency of microcapsule powder was verified.

[0132] Verification results

[0133] 1. Composition analysis of microcapsule core material

[0134] As shown in Table 1, four components were detected in the microcapsule core material using gas chromatography. The microcapsule core material is mainly composed of unsaturated fatty acid ethyl esters, with ethyl linolenic acid being the main component, accounting for as high as 59.75% by volume, followed by ethyl linoleate at 31.52% by volume. Both of these components are beneficial to the human body. The saturated fatty acid ethyl esters accounted for only 8.87% by volume, a very low content.

[0135] Table 1. Composition Analysis of Microcapsule Core Material

[0136]

[0137] 2. Results of single-factor experiments in Examples 1-4

[0138] (1) Effect of wall material ratio on microcapsule embedding rate

[0139] from Figure 1 As shown in Table 2, decreasing the wall material ratio SPI:MD:MCC from 3:1.5:1 to 3:1.2:1 significantly improved the microcapsule encapsulation efficiency (P < 0.05). At wall material ratios of 3:1.2:1 and 3:1:1, the microcapsule encapsulation efficiencies were 72.77% and 73.32%, respectively, with no significant difference (P > 0.05). This wall material composition is more conducive to forming an effective encapsulation structure. Considering the synergistic effect, this invention determined the SPI:MD:MCC mass ratio to be 3:1:1.

[0140] Table 2. Effect of wall material ratio on microcapsule encapsulation efficiency

[0141]

[0142] (2) Effect of core-to-wall ratio on microcapsule embedding rate

[0143] from Figure 2 As shown in Table 3, when the core-to-wall ratio decreased from 1:1 to 2:5, the microcapsule encapsulation efficiency significantly increased from 52.22% to 78.38% (P < 0.05). When the core-to-wall ratio decreased from 2:5 to 1:3, the encapsulation efficiency decreased. With a decreasing core-to-wall ratio, the mass fraction of the wall material increases, which better encapsulates the core material, improving the encapsulation effect. However, when the core-to-wall ratio is too small, the stability of the emulsion deteriorates, the viscosity of the system increases, and it cannot effectively encapsulate the core material, leading to a decrease in the encapsulation efficiency.

[0144] Table 3. Effect of core-to-wall ratio on microcapsule encapsulation efficiency

[0145]

[0146] (3) Effect of homogenization time on microcapsule embedding rate

[0147] from Figure 3As shown in Table 4, the microcapsule embedding rate significantly increased when the homogenization time increased from 4 min to 6 min (P < 0.05). This may be because mechanical shear force during homogenization can improve the embedding effect to some extent. Conversely, the microcapsule embedding rate significantly decreased when the homogenization time increased from 6 min to 12 min (P < 0.05). This may be because excessively long homogenization times and strong shear forces can damage the structural integrity of the wall material, leading to a decrease in embedding rate.

[0148] Table 4. Effect of homogenization time on microcapsule embedding rate

[0149]

[0150] (4) Effect of temperature on microcapsule encapsulation efficiency

[0151] from Figure 4 As shown in Table 5, within a certain range, the encapsulation efficiency of the microcapsules initially increases and then decreases with increasing emulsification temperature. The highest encapsulation efficiency (79.60%) is achieved at an emulsification temperature of 50℃. At excessively low temperatures, SPI, MD, and MCC are difficult to dissolve fully, resulting in poor emulsification and low encapsulation efficiency. When the temperature exceeds 60℃, protein denaturation occurs, affecting the emulsification effect and worsening the encapsulation.

[0152] Table 5. Effect of temperature on microcapsule encapsulation efficiency

[0153]

[0154] 3. Response surface methodology

[0155] Based on the results of the single-factor experiments, three factors were selected: core-to-wall ratio, emulsification temperature, and homogenization time. Using the encapsulation rate as an indicator, a three-factor, three-level experiment was designed using the Box-Behnken method (Table 6) to determine the optimal process conditions for preparing α-linolenic acid microcapsules.

[0156] Table 6. Factors and levels in response surface methodology

[0157]

[0158] The response surface design experiments and results are shown in Table 7, and the analysis of variance is shown in Table 8.

[0159] Table 7. Experiments and Results of Response Surface Design

[0160]

[0161]

[0162] Table 8. Results of ANOVA and Significance Analysis

[0163]

[0164] By analyzing and integrating the data obtained from the response surface methodology, the regression equation between the embedding rate and the three independent variables—core-to-wall ratio, emulsification temperature, and homogenization time—was obtained: Y = 79.75 + 0.63A + 1.20B - 0.17C - 0.24AB - 0.13AC + 0.21BC - 3.68A 2 -8.58B 2 -3.38C 2 ;

[0165] The analysis of variance in Table 8 shows that the factors influencing the microcapsule embedding rate, from largest to smallest, are: emulsification temperature > core-to-wall ratio > homogenization time. Emulsification temperature has a highly significant effect on the embedding rate (p < 0.0001), while core-to-wall ratio has a significant effect (p < 0.01). The p-value of the regression model is < 0.0001, indicating that the regression model has a highly significant effect. The p-value for the lack-of-fit term is 0.1107 (p > 0.05), meaning the lack-of-fit term is not significant, indicating a high degree of fit between the equation and the experiment. The model's coefficient of determination R0 is... 2 =0.9976, R 2 The adj = 0.9944 indicates a high good fit of the regression equation, and R0 is high. 2 With correction factor R 2 The difference between adj is less than 0.2, which verifies that the regression equation and the experimental results have a high degree of consistency.

[0166] The response surface plot and contour plot drawn based on the above equations visually demonstrate the interactive effects of various factors on the embedding rate. Figure 5 It can be seen that the degree of influence of the interaction of various factors on the response value is in the order of AB>BC>AC. Among them, the interaction between A (core-to-wall ratio) and B (temperature) is the most significant, specifically manifested in the steepest response surface and the elliptical contour lines, indicating that the combination of these two factors has the most prominent impact on the embedding rate.

[0167] Based on regression analysis and response surface methodology (RSM) predictions, the optimal preparation process was determined to be a core-to-wall ratio of 2:5, an emulsification temperature of 50.68℃, and a homogenization time of 5.95 min, with a predicted AEL microcapsule encapsulation rate of 79.82%. To ensure experimental feasibility, the optimal conditions were adjusted to a core-to-wall ratio of 2:5, an emulsification temperature of 50.7℃, and a homogenization time of 6 min. The experiment was repeated three times for verification, yielding an AEL microcapsule encapsulation rate of 81.68%. The relative error compared to the theoretical value was 2.33% (<5%), indicating that the optimal preparation process conditions obtained through RSM optimization are reliable.

[0168] Example 5

[0169] Soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) were dissolved in deionized water (SPI:MD:MCC mass ratio of 3:1:1) and stirred at 50°C using a thermostatic magnetic stirrer until dissolved to prepare an aqueous phase with a solid content of 6.7%.

[0170] Weigh out the emulsifier (Tween-80, Span-80 and sodium caseinate in a mass ratio of 1:1:1) and add it to ethyl perilla α-linolenic acid (AEL). Stir until the emulsifier is dissolved to obtain the oil phase.

[0171] The oil phase was added dropwise to the aqueous phase using a dropper, while simultaneously stirring and emulsifying at 50.7°C to ensure thorough mixing of the oil and aqueous phases. The mixture was stirred for 1 hour to obtain a crude emulsion with a solids mass fraction of 10% and a core-to-wall ratio of 2:5.

[0172] The crude emulsion was transferred to a high-speed disperser and homogenized at 10,000 rpm for 6 min. The resulting emulsion was then spray-dried under the following conditions: inlet air temperature of 180±5℃, atomizer frequency of 60Hz, and flow rate of 400mL / min. AEL microcapsules were obtained.

[0173] Characterization results

[0174] (1) SEM analysis

[0175] Hollow spheres are a typical shape for spray-dried powders and are usually available in a variety of sizes. Figure 6 The image shows a SEM image of the microcapsules. Scanning electron microscopy (SEM) characterization results indicate that the prepared microcapsule particles are nearly spherical with a dense and intact capsule wall structure, without obvious cracks or pores. The microcapsule surface is rough with localized depressions, which may be due to the wall material undergoing solvent evaporation and curing shrinkage within a very short time during the high-temperature spray drying process, leading to an imbalance in the surface tension gradient and thus forming irregular depressions. This phenomenon is a common characteristic of high-temperature spray-dried microcapsule powder products.

[0176] (2) Particle size analysis

[0177] Figure 7 As shown in the microcapsule particle size distribution diagram, the average particle size D of the microcapsules is 5.91 μm, with uniform particle size and relatively concentrated distribution. The particle size of the microcapsules is mainly dispersed in the range of 1–33 μm, which meets the general production requirements for microcapsule particle size. Smaller particle size can increase the specific surface area, thereby enhancing the contact between the active ingredient and the carrier, improving the encapsulation efficiency, and increasing the solubility of the powder. Therefore, smaller particle size is very important for microcapsules.

[0178] (3) Fourier transform infrared spectroscopy (FT-IR) analysis

[0179] Figure 8For SPI, MD, MCC, SPI-MD-MCC, AEL and AEL microcapsules in 400-4000 cm⁻¹ -1 Infrared spectra within the wavenumber range. For SPI, MD, and MCC, the wavelength at 1655 cm⁻¹ is [missing value]. -1 The characteristic peaks in the vicinity are mainly attributed to olefin groups containing a C=C skeleton. Furthermore, the peaks at 3500–3200 cm⁻¹ are also significant. -1 The broad absorption peak at 2925 cm⁻¹ is due to the abundant -OH groups present in SPI, MD, and MCC. AEL is at 2925 cm⁻¹. -1 The characteristic peak at 1738 cm⁻¹ is caused by the stretching vibration of the =CH bond, while the peak at 1738 cm⁻¹ is caused by the stretching vibration of the =CH bond. -1 The sharp absorption peaks nearby are related to the ester groups in AEL.

[0180] By comparing the infrared spectra of microcapsules with those of SPI, MD, MCC, SPI-MD-MCC, and AEL, it can be found that the main characteristic peaks of SPI, MD, MCC, SPI-MD-MCC, and AEL are all present in the spectra of microcapsules, but the intensity is reduced. This allows us to determine the formation of the AEL microcapsule embedding structure.

[0181] (4) X-ray diffraction analysis

[0182] XRD analysis is crucial for determining the wall material and embedding conditions of microcapsules. Figure 9 The X-ray diffraction patterns of SPI, MD, MCC, SPI-MD-MCC, AEL, and AEL microcapsules are shown. SPI and MD show only broad peaks, indicating their amorphous structure. MCC exhibits a distinct peak near 2θ = 22.5°, indicating that MCC retains the type I structure characteristics of natural cellulose and is a polymorph with a β-type structure. Compared to the wall material, the characteristic peak of the AEL microcapsule at a diffraction angle of 2θ (19.20°) is slightly shifted, and there is a gap between peak sharpness and intensity. The peak of the microcapsule is narrower and its intensity is increased, indicating that the addition of AEL does not significantly change the position of the main diffraction peak, but it narrows the peak and increases its intensity. In summary, there is a high degree of compatibility between the core material and the wall material, and the embedding does not significantly damage the structure of the wall material.

[0183] (5) Thermogravimetric analysis

[0184] Figure 10Thermogravimetric analysis (TG) results for AEL, SPI-MD-MCC, and microcapsules are presented. The mass of each sample gradually decreased with increasing temperature. The TG curve for AEL was divided into two stages: the first stage was from 25 to 150℃, with a mass reduction of 10.92%; the second stage was from 150 to 300℃, with a dramatic weight loss of 73.25%. The TG curve for SPI-MD-MCC was also divided into two stages: the first stage was from 0 to 175℃, with a mass reduction of 7.40%; the second stage was from 175 to 500℃, with a mass loss of 80.97%. The total weight loss of the microcapsule powder was 80.00%. The first stage was from 0 to 179℃, with relatively moderate weight loss; the second stage was from 179 to 387℃, with a weight loss of 60.02%; and the third stage was from 387 to 600℃, with a weight loss of 10.34%.

[0185] The above analysis shows that the weight loss rate of the microcapsules falls between that of AEL and SPI-MD-MCC. Comparing the TG curves of the microcapsules and SPI-MD-MCC, their shapes are similar, and their initial and final degradation temperatures are close. However, due to the addition of AEL, the weight loss process of the microcapsules is faster than that of SPI-MD-MCC. This indicates that SPI-MD-MCC only has an encapsulation effect on AEL and does not change the physicochemical properties of either material. Furthermore, the microcapsule powder exhibits better thermal stability compared to AEL.

[0186] (6) Results of in vitro digestion and release experiments

[0187] To evaluate the in vitro release effect of the microcapsules, simulated digestion was used to test their stability and release behavior during gastrointestinal transit. The in vitro simulated digestion consisted of two parts: simulated gastric digestion and simulated intestinal digestion. Generally, food is digested in the stomach for 120 minutes, and then further digested in the small intestine for 240 minutes. Figure 11 As shown, during the first 120 minutes of gastric digestion, the microcapsules are entirely in the acidic environment of the stomach, and the microcapsule wall material has a controlling effect on the release of AEL (anti-inflammatory elutile) protein (AEL). The release rate of the core material is <15% after 120 minutes of digestion. During digestion in the small intestine from 120 to 360 minutes, due to trypsin degradation and a weakly alkaline environment, a large amount of the core material is released. By the end of 360 minutes, the microcapsules have released more than 85% of the core material.

[0188] (7) Oxidative stability of AEL

[0189] like Figure 12As shown, the peroxide values ​​of both samples increased with prolonged storage time, indicating that the degree of oil oxidation increased over time. The peroxide value of unencapsulated AEL increased significantly faster than that of encapsulated AEL, suggesting that unencapsulated AEL is more susceptible to oxidation. On day 13, the peroxide value of unencapsulated AEL (12.70 mmol / kg) was 1.78 times higher than that of encapsulated AEL (7.13 mmol / kg). These results demonstrate that microencapsulation improves the antioxidant capacity and storage stability of AEL.

[0190] This invention successfully prepared α-linolenic acid ethyl ester (AEL) microcapsules using soy protein isolate (SPI), maltodextrin (MD), and microcrystalline cellulose (MCC) as wall materials. Through single-factor experiments and response surface methodology, the optimal preparation conditions were determined to be: 10% solids content, a wall material ratio of 3:1:1, a core-to-wall ratio of 2:5, an emulsification temperature of 50.7℃, and a homogenization time of 6 min, achieving an encapsulation efficiency of 81.68%. Structural characterization showed that the AEL microcapsules were spherical with a particle size concentrated between 1 and 10 μm. FTIR and XRD analyses confirmed successful AEL encapsulation with no change in crystallinity. Thermogravimetric analysis indicated that the microcapsules exhibited superior thermal stability compared to AEL. In vitro digestion experiments showed that the release rate of the microcapsules was less than 15% within 120 min in simulated gastric juice, and more than 85% of the core material was released by the end of 360 min of digestion in simulated intestinal juice, demonstrating excellent sustained-release performance. After storage at 60°C for 13 days, AEL and AEL microcapsules were found to effectively slow down the oxidation process of AEL. This invention provides an effective method for the protection and application of AEL and has the potential for industrial application.

[0191] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A microcapsule of ethyl α-linolenic acid, characterized in that, It includes a core material and a wall material, wherein the core material includes ethyl α-linolenic acid; The wall material comprises soy protein isolate, maltodextrin, and microcrystalline cellulose; the mass ratio of soy protein isolate, maltodextrin, and microcrystalline cellulose is 3:1 to 1.2:

1. The mass ratio of the core material to the wall material is 1:2 to 3.

2. The α-linolenic acid ethyl ester microcapsules according to claim 1, characterized in that, The α-linolenic acid ethyl ester includes at least one of perilla α-linolenic acid ethyl ester and linolenic acid α-linolenic acid ethyl ester.

3. The α-linolenic acid ethyl ester microcapsules according to claim 1, characterized in that, The encapsulation rate of the α-linolenic acid ethyl ester microcapsules was 70-85%.

4. The method for preparing α-linolenic acid ethyl ester microcapsules according to any one of claims 1 to 3, characterized in that, Includes the following steps: The wall material and water are mixed to obtain an aqueous phase; The core material and emulsifier are mixed to obtain the oil phase; The aqueous phase and oil phase are mixed and emulsified to obtain a crude emulsion; The crude emulsion was homogenized and spray-dried sequentially to obtain the α-linolenic acid ethyl ester microcapsules.

5. The preparation method according to claim 4, characterized in that, The wall material and water are mixed at a temperature of 45–55°C; the solid content of the aqueous phase is 6.3–7.1%.

6. The preparation method according to claim 4, characterized in that, The emulsifiers include Tween-80, Span-80, and sodium caseinate; the mass ratio of Tween-80, Span-80, and sodium caseinate is 1:1:1; The emulsifier is present at 1-2% of the core material mass.

7. The preparation method according to claim 4, characterized in that, The process of mixing the aqueous phase and the oil phase is as follows: under stirring conditions, the oil phase is dripped into the aqueous phase.

8. The preparation method according to claim 4, characterized in that, The emulsification temperature is 45–60°C; the emulsification is carried out under stirring conditions, and the stirring time is 1–1.5 h.

9. The preparation method according to claim 4, characterized in that, The homogenization process is carried out at a rotation speed of 8000–10000 rpm for 6–8 minutes.

10. The preparation method according to claim 4, characterized in that, The conditions for spray drying include: an inlet air temperature of 180±5℃, an atomizer frequency of 60Hz, and a flow rate of 400~600mL / min.

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