A viscosity-controlled microfluidic fish oil microsphere, its preparation method and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGGUAN UNIV OF TECH
- Filing Date
- 2026-01-12
- Publication Date
- 2026-05-26
Smart Images
Figure CN122076334A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional food preparation technology, specifically relating to a microfluidic fish oil microsphere preparation method based on viscosity control and its application, particularly a technology that simultaneously optimizes the particle size, oxidative stability and digestion release behavior of ω-3 polyunsaturated fatty acid microspheres by controlling viscosity through oil phase compounding. Background Technology
[0002] Deep-sea fish oil is rich in long-chain ω-3 polyunsaturated fatty acids (ω-3 PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have various important physiological functions, including regulating blood lipids, anti-inflammation, and promoting the development of the nervous system. However, EPA and DHA molecules contain multiple unsaturated double bonds, making them highly susceptible to auto-oxidation under the influence of light, heat, and metal ions. This leads to a decrease in nutritional value and the production of a rancid odor, thus limiting their application in room-temperature foods. Traditional fish oil microcapsules often employ a "macro-emulsification-spray drying" process, resulting in a wide particle size distribution and interfacial structure that is easily affected by process fluctuations. They are prone to aggregation or rupture under changes in pH, salinity, and temperature, and the high-temperature spray process exacerbates thermal oxidation reactions.
[0003] Microfluidic droplet technology can precisely control parameters such as channel structure, phase viscosity, interfacial tension, and driving force at the micrometer scale to prepare monodisperse droplets with low coefficient of variation (≤5%), providing an ideal model for studying the relationship between "structure-stability / digestion behavior". While existing research shows that oil phase viscosity affects droplet formation frequency and volume, systematic studies on the coupling relationship between "viscosity-particle size-stability-digestion behavior" in real fish oil systems remain lacking. Furthermore, fish oil digestion behavior is jointly regulated by droplet size, interfacial composition, and internal viscosity; however, achieving a balance between particle size, viscosity, and interfacial structure to ensure both oxidative stability and digestibility requires further investigation. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes a microfluidic fish oil microsphere preparation method based on viscosity control. By compounding fish oil and castor oil to regulate the viscosity of the oil phase, the microsphere particle size, morphology, environmental stability, and digestion and release characteristics are systematically optimized, providing a theoretical basis and precise process parameters for the structured design of ω-3 PUFA functional foods.
[0005] The technical solution adopted in this invention is a method for preparing microfluidic fish oil microspheres based on viscosity control, comprising the following steps: (1) Preparation of oil phase: Concentrated fish oil and castor oil are mixed at a volume ratio of 10:0 to 4, and the mixture is left to stand in a water bath at 25 to 30°C for 20 to 40 minutes and intermittently inverted to mix, so as to obtain an oil phase with a dynamic viscosity of 3.4 to 15.2 mPa·s; (2) Preparation of continuous phase: Prepare a polyvinyl alcohol aqueous solution with a mass concentration of 2.5-3.5% and degas it to serve as the continuous phase; (3) Microfluidic preparation: A cross-shaped microfluidic chip is used, with the oil phase as the dispersed phase and the continuous phase as the continuous phase. The oil phase is injected into the chip under a constant inlet pressure, and the flow rate ratio of the water phase to the oil phase is controlled to be 15 to 45:1. The water-in-oil type fish oil microsphere emulsion is collected at the chip outlet. (4) In this step (1), by adjusting the proportion of castor oil added, the viscosity of the oil phase is varied in the range of 3.2 to 15.2 mPa·s, thereby precisely controlling the microsphere particle size to be 53.89 to 72.34 μm with a coefficient of variation ≤5%, and achieving controllable adjustment of oxidative stability and digestion release behavior.
[0006] Preferably, the concentrated fish oil in step (1) is deep-sea fish oil rich in EPA and DHA, wherein the mass fraction of EPA+DHA is ≥70%; the castor oil is analytical grade and has a dynamic viscosity of 200-300 mPa·s at 25°C.
[0007] Preferably, in step (1), the volume ratio of concentrated fish oil to castor oil is 10:0, 8:2 or 6:4, corresponding to a low viscosity oil phase of 3.47 mPa·s, a medium viscosity oil phase of 8.69 mPa·s or a high viscosity oil phase of 15.19 mPa·s.
[0008] Preferably, the degree of polymerization of the polyvinyl alcohol in step (2) is 1700-1800, the degree of alcoholysis is ≥98%, and the continuous phase needs to be degassed under vacuum for 10-20 minutes before being implanted into the chip.
[0009] Preferably, the cross-shaped microfluidic chip in step (3) has a glass-glass bonded structure with a channel depth of 50–200 μm and a hydrophilic surface treatment; the inlet pressure of the dispersed phase is 0.02–0.05 MPa, the inlet pressure of the continuous phase is 0.05–0.08 MPa; the oil phase flow rate is 20–25 μL / min, and the aqueous phase flow rate is 300–1000 μL / min.
[0010] Preferably, the fish oil microspheres obtained are stored for 15 days under pH 5-7 and 0-2% NaCl conditions, with an average particle size change rate ≤ ±5% and a coefficient of variation increase ≤ 2%; under pH 3 or pH 9 conditions, the particle size change rate of the high viscosity group microspheres is 30-50% lower than that of the low viscosity group.
[0011] Preferably, the fish oil microspheres obtained in step (3) are stored at 4-60°C for 12 days. The acid value of the high viscosity group is 20-40% lower than that of the low viscosity group, the reactant value of thiobarbituric acid is 25-35% lower, and the ABTS free radical scavenging rate is 10-15% higher.
[0012] Preferably, in an in vitro simulated small intestinal digestion experiment, the fish oil microspheres exhibit a significant sustained-release effect, with the low-viscosity group releasing 80-90% of free fatty acids and the high-viscosity group releasing 60-70% of free fatty acids after 120 minutes.
[0013] A viscosity-controllable fish oil microsphere has a particle size of 53.89–72.34 μm, a coefficient of variation of 3–5%, a regular spherical morphology, excellent oxidative stability under storage conditions of 4–60℃, and controllable digestion and release characteristics.
[0014] The application of a viscosity-controllable fish oil microsphere in functional foods, dietary supplements, and special medical foods achieves precise control over the bioavailability and release rate of EPA and DHA by regulating the viscosity of the oil phase.
[0015] The beneficial effects of this invention are: (1) This invention uses microfluidic technology combined with viscosity control strategy, which can control the particle size of fish oil microspheres within the range of 53.89~72.34 μm within 20 minutes, with a coefficient of variation ≤5%. Compared with the traditional spray drying method (the coefficient of variation is usually >15%), the particle size uniformity is improved by more than 3 times, and the process conditions are mild, without high temperature process, avoiding the thermal oxidation loss of ω-3 PUFA. (2) This invention achieves viscosity gradient control by compounding fish oil and castor oil, and can achieve precise adjustment of particle size under the same microfluidic conditions, without the need to replace the chip or adjust the flow rate over a large range. The process has good repeatability, is easy to operate, and is easy to scale up industrially. (3) After accelerated oxidation at 60℃ for 12 days, the acid value of the microspheres prepared by the high viscosity oil phase was 20-40% lower than that of the low viscosity group, and the TBARS value was 25-35% lower, and the oxidation stability was significantly improved. This is due to the fact that the high viscosity system reduces the migration rate of reactive oxygen species, and the small particle size microspheres have a large specific surface area but a denser interfacial protective layer, realizing the synergistic effect of "small particle size + high stability", breaking through the technical bottleneck of easy oxidation of small particle size in traditional understanding. (4) This invention achieves precise design of the digestion and release behavior of microspheres through viscosity control: low viscosity microspheres release quickly, with a free fatty acid release rate of 80-90% in 120 min, which is suitable for rapid supplementation scenarios; high viscosity microspheres exhibit slow release characteristics, with a release rate of 60-70%, which is suitable for long-term nutrient delivery and meets the nutritional needs of different groups.
[0016] (5) The microspheres prepared by this invention have a particle size change rate of ≤±5% after 15 days of storage under pH 5~7 and 0~2% NaCl conditions. They remain stable under temperature fluctuations of -8~40℃ and transportation bumps, which significantly reduces transportation and storage costs and extends the shelf life to more than 3 months. Attached Figure Description
[0017] Figure 1This is a schematic diagram of the cross-shaped microfluidic chip structure of the present invention and a comparison diagram of the necking behavior of oil phases of different viscosities at the T-shaped opening.
[0018] Figure 2 Box plots showing the particle size distribution of fish oil microspheres prepared from oil phases of three viscosities according to the present invention.
[0019] Figure 3 This is a curve showing the effect of different salt ion concentrations on the stability of microsphere size in this invention.
[0020] Figure 4 This is a curve showing the effect of different pH values on the stability of microsphere particle size in this invention.
[0021] Figure 5 The curves showing the changes in acid value and TBARS value of the microspheres under different temperature storage conditions according to the present invention.
[0022] Figure 6 This invention simulates the release curves of free fatty acids from microspheres of three different viscosities during small intestinal digestion. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0024] Raw materials and reagents used in this embodiment: Concentrated fish oil: EPA + DHA mass fraction of approximately 70%, sourced from, but not limited to, skipjack tuna oil. Example 1: Preparation of low-viscosity fish oil microspheres (1) Oil phase preparation: 10 mL of pure concentrated fish oil (without adding castor oil) was placed in a 25℃ water bath for 30 minutes to equilibrate, and the dynamic viscosity was measured to be 3.47 mPa·s; (2) Preparation of continuous phase: Weigh 3.0 g of polyvinyl alcohol and dissolve it in 100 mL of deionized water. Heat to 90 °C until completely dissolved. Cool to room temperature and then degas under vacuum for 15 minutes. (3) Microfluidic preparation: A cross-shaped glass microfluidic chip with a channel depth of 100 μm was used and treated with oxygen plasma for hydrophilicity. The oil phase was injected into the dispersed phase inlet at a pressure of 0.02 MPa, and the continuous phase was injected into the continuous phase inlets on both sides at a pressure of 0.06 MPa. The flow rate of the aqueous phase was controlled at 500 μL / min, the flow rate of the oil phase at 20 μL / min, and the flow rate ratio at 25:1. The oil-in-water fish oil microsphere emulsion was collected at the chip outlet. (4) Characterization: The average particle size of the prepared microspheres was 72.34±3.70 μm, with a coefficient of variation of 5.1%, and they were regular spherical.
[0025] Example 2: Preparation of medium-viscosity fish oil microspheres (1) Oil phase preparation: Concentrated fish oil and castor oil were mixed at a volume ratio of 8:2, with a total volume of 10 mL. The mixture was left to stand in a water bath at 25°C for 30 minutes and then intermittently inverted 5 times. The dynamic viscosity was measured to be 8.69 mPa·s. (2) Preparation of continuous phase: Same as in Example 1; (3) Microfluidic control equipment: The chip parameters are the same as in Example 1, and the water phase flow rate is adjusted to 600 μL / min, the oil phase flow rate is 22 μL / min, and the flow rate ratio is 27:1. (4) Characterization: The average particle size of the microspheres was 64.71±3.20 μm, the coefficient of variation was 4.9%, and the length of the necked liquid column was 379.08±0.72 μm, which was 10.1% shorter than that of Example 1.
[0026] Example 3: Preparation of high-viscosity fish oil microspheres (1) Oil phase preparation: Concentrated fish oil and castor oil were mixed at a volume ratio of 6:4, with a total volume of 10 mL. The mixture was left to stand in a 30℃ water bath for 35 minutes and intermittently inverted 6 times. The dynamic viscosity was measured to be 15.19 mPa·s. (2) Preparation of continuous phase: Same as in Example 1; (3) Microfluidic control equipment: The chip parameters are the same as in Example 1, and the water phase flow rate is adjusted to 750 μL / min, the oil phase flow rate is 25 μL / min, and the flow rate ratio is 30:1. (4) Characterization: The average particle size of the microspheres was 53.89±1.72 μm, the coefficient of variation was 3.2%, the length of the necked liquid column was 368.43±1.27 μm, which was 12.6% shorter than that of Example 1, and the particle size distribution was highly concentrated.
[0027] Example 4: pH stability test Take 5 mL of each of the fish oil microspheres prepared in Examples 1-3, and mix them with equal volumes of phosphate buffer solutions of different pH values (3, 5, 7, 9). Incubate at 25°C in the dark. Samples were taken after 15 days to determine the particle size. The results are shown in Table 1. Table 1. Average particle size change rate (%) of microspheres under different pH conditions pH 3 pH 5 pH 7 pH 9 Low viscosity group 9.2±0.8 5.1±0.5 4.8±0.6 8.5±0.7 Medium viscosity group 8.5±0.7 2.1±0.3 2.3±0.2 4.8±0.5 High viscosity group 3.1±0.2 1.2±0.1 1.5±0.2 2.9±0.3 Data shows that the high viscosity group exhibits the best particle size stability under extreme pH conditions, with a change rate more than 50% lower than that of the low viscosity group.
[0028] Example 5: Oxidative Stability Test The microspheres from Examples 1-3 were subjected to accelerated oxidation at 60°C for 0, 6, and 12 days, and the ABTS and DPPH scavenging rates were measured periodically. The results are shown in Table 2. Table 2. Changes in oxidation parameters after 12 days of accelerated oxidation at 60℃ ABTS DPPH low concentration medium concentration high concentration low concentration medium concentration high concentration 0 days <![CDATA[45.03±0.53 a ]]> <![CDATA[47.49±0.18 a ]]> <![CDATA[50.79±0.95 a ]]> <![CDATA[46.77±0.75 a ]]> <![CDATA[55.90±1.79 a ]]> <![CDATA[57.22±0.61 a ]]> 6 days <![CDATA[30.41±0.23 b ]]> <![CDATA[44.94±1.37 b ]]> <![CDATA[32.12±0.01 b ]]> <![CDATA[29.47±0.64 b ]]> <![CDATA[38.52±1.07 b ]]> <![CDATA[37.20±0.57 b ]]> 12 days <![CDATA[19.17±0.06 c ]]> <![CDATA[26.17±2.23 c ]]> <![CDATA[14.12±0.01 c ]]> <![CDATA[13.72±0.06 c ]]> <![CDATA[27.59±1.88 c ]]> <![CDATA[24.33±0.33 c ]]> Note: Different letters in the same column for the same temperature group indicate significant differences (p < 0.05). The acid value of the high viscosity group was 46.3% lower than that of the low viscosity group, the TBARS value was 36.6% lower, and the oxidative stability was significantly improved.
[0029] Example 6: In vitro digestion test Referring to the small intestine stage of the INFOGEST static in vitro digestion model, 10 mL of each of the microspheres from Examples 1-3 were mixed with an equal volume of simulated small intestinal fluid (containing 10 mM bile salts, 100 U / mL pancreatic lipase, pH 7.0), and shaken in a 37°C water bath. The pH was maintained constant using the pH-stat method, and the volume of NaOH consumed within 120 min was recorded and the FFA release rate was calculated. The results are as follows: Figure 6 As shown: The low viscosity group showed an FFA release rate of 65% within 30 minutes and a peak of 88% at 120 minutes; the medium viscosity group showed a release rate of 72% at 120 minutes; and the high viscosity group showed a sustained release with a release rate of 63% at 120 minutes, while maintaining the integrity of the microsphere structure, making it suitable for long-term nutrient delivery.
[0030] Comparative Example 1: Traditional High-Shear Emulsification Method 10 mL of concentrated fish oil was mixed with 100 mL of 3% PVA solution and emulsified at 10,000 rpm for 5 minutes using a high-speed shear mill. The resulting emulsion had a wide particle size distribution (D10~D90 of 45~185 μm) and a coefficient of variation of 18.7%. After oxidation at 60℃ for 12 days, the increase in acid value was 58% higher than that in Example 3, indicating that the traditional method has poor particle size controllability and insufficient stability.
[0031] Comparative Example 2: Single Fish Oil Microspheres (without castor oil) Similar to Example 1, microspheres were prepared using only pure fish oil. After storage at pH 3 for 15 days, the particle size change rate reached 9.2%, significantly higher than the 2.9% in Example 3, demonstrating that the addition of castor oil to regulate viscosity can significantly improve stability in extreme environments.
[0032] Application Example 1: Functional Beverage Additives Five mL of the high-viscosity microspheres (containing 1 g of fish oil) from Example 3 were added to 100 mL of a neutral plant protein beverage (pH 6.8). After UHT sterilization (135°C, 4 seconds), the beverage was stored at room temperature for 90 days. The microsphere particle size change rate before and after sterilization was <3%, the acid value at the end of the storage period was 1.85 mg KOH / g, and the DHA retention rate was >85%, indicating that the microspheres are suitable for liquid functional food systems.
[0033] Application Example 2: Special Medical Nutritional Supplements The low-viscosity microspheres from Example 1 were spray-dried (inlet air temperature 150°C, outlet air temperature 75°C) to obtain microcapsule powder. Packaged in 1 g servings, the recommended daily intake is 2 servings, providing 600 mg of EPA+DHA. Preclinical digestion experiments showed that the powder had a dissolution rate of >70% in simulated gastrointestinal fluid within 30 minutes, making it suitable for rapid postoperative nutritional supplementation.
[0034] In summary, this invention, through microfluidic technology combined with oil phase viscosity control, can prepare fish oil microspheres with precise controllable particle size, excellent stability, and adjustable digestion behavior under mild conditions, breaking through the technical bottleneck of traditional spray drying methods and providing an innovative solution for the efficient delivery of ω-3 PUFA.
[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing microfluidic fish oil microspheres based on viscosity control, characterized in that, Includes the following steps: (1) Preparation of oil phase: Concentrated fish oil and castor oil are mixed at a volume ratio of 10:0 to 4, and the mixture is left to stand in a water bath at 25 to 30°C for 20 to 40 minutes and intermittently inverted to mix, so as to obtain an oil phase with a dynamic viscosity of 3.4 to 15.2 mPa·s; (2) Preparation of continuous phase: Prepare a polyvinyl alcohol aqueous solution with a mass concentration of 2.5-3.5% and degas it to serve as the continuous phase; (3) Microfluidic preparation: A cross-shaped microfluidic chip is used, with the oil phase as the dispersed phase and the continuous phase as the continuous phase. The oil phase is injected into the chip under a constant inlet pressure, and the flow rate ratio of the water phase to the oil phase is controlled to be 15 to 45:
1. The water-in-oil type fish oil microsphere emulsion is collected at the chip outlet. (4) In this step (1), by adjusting the proportion of castor oil added, the viscosity of the oil phase is varied in the range of 3.2 to 15.2 mPa·s, thereby precisely controlling the microsphere particle size to be 53.89 to 72.34 μm with a coefficient of variation ≤5%, and achieving controllable adjustment of oxidative stability and digestion release behavior.
2. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, The concentrated fish oil in step (1) is deep-sea fish oil rich in EPA and DHA, wherein the mass fraction of EPA+DHA is ≥70%; the castor oil is analytical grade and has a dynamic viscosity of 200-300 mPa·s at 25°C.
3. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, In step (1), the volume ratio of concentrated fish oil to castor oil is 10:0, 8:2 or 6:4, which corresponds to a low viscosity oil phase of 3.47 mPa·s, a medium viscosity oil phase of 8.69 mPa·s or a high viscosity oil phase of 15.19 mPa·s.
4. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol in step (2) is 1700-1800, the degree of alcoholysis is ≥98%, and the continuous phase needs to be degassed under vacuum for 10-20 minutes before being injected into the chip.
5. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, The cross-shaped microfluidic chip in step (3) has a glass-glass bonded structure with a channel depth of 50–200 μm and a hydrophilic surface treatment; the inlet pressure of the dispersed phase is 0.02–0.05 MPa, the inlet pressure of the continuous phase is 0.05–0.08 MPa; the oil phase flow rate is 20–25 μL / min, and the water phase flow rate is 300–1000 μL / min.
6. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, The obtained fish oil microspheres were stored for 15 days at pH 5–7 and 0–2% NaCl, with an average particle size change rate of ≤±5% and a coefficient of variation increase of ≤2%. Under pH 3 or pH 9 conditions, the particle size change rate of the high viscosity group microspheres was 30–50% lower than that of the low viscosity group.
7. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, The fish oil microspheres obtained in step (3) were stored at 4-60℃ for 12 days. The acid value of the high viscosity group was 20-40% lower than that of the low viscosity group, the reactant value of thiobarbituric acid was 25-35% lower, and the ABTS free radical scavenging rate was 10-15% higher.
8. The method for preparing microfluidic fish oil microspheres based on viscosity control according to claim 1, characterized in that, In an in vitro simulated small intestinal digestion experiment, the fish oil microspheres showed a significant sustained-release effect, with the low-viscosity group releasing 80-90% of free fatty acids and the high-viscosity group releasing 60-70% of free fatty acids after 120 minutes.
9. A viscosity-controllable fish oil microsphere prepared by the method according to any one of claims 1 to 8, characterized in that, The microspheres have a particle size of 53.89–72.34 μm, a coefficient of variation of 3–5%, and a regular spherical shape. They exhibit excellent oxidation stability under storage conditions of 4–60℃ and have controllable digestion and release characteristics.
10. The application of the viscosity-controllable fish oil microspheres of claim 9 in functional foods, dietary supplements, and special medical foods, characterized in that, Precise control of the bioavailability and release rate of EPA and DHA can be achieved by adjusting the viscosity of the oil phase.