A method for preparing a water-in-water-in-oil pickering emulsion based on a water-in-water emulsion structure

Abstract

The present application belongs to the technical field of emulsion production and preparation, and more particularly relates to a method for preparing water-in-oil-in-water Pickering emulsion based on water-in-water emulsion structure. First, a water phase continuous phase with dispersed particle stabilizer is emulsified with a water phase dispersed phase to prepare a stable water-in-water Pickering emulsion, and then the water-in-water Pickering emulsion is further dispersed in an oil phase continuous phase as a dispersed phase to obtain an oil-in-water-in-water Pickering emulsion. The oil-in-water-in-water Pickering emulsion prepared by the present application is storage stable, and can be used as a delivery carrier to simultaneously deliver water-soluble and oil-soluble nutrients. The method of the present application is low-energy emulsification, does not require complex production equipment, does not require high-temperature and high-pressure treatment, is simple and easy to implement, has high process efficiency, and the emulsion particle size is controllable.

Description

Technical Field

[0001] This invention belongs to the field of emulsion production and preparation technology, and more specifically, relates to a method for preparing oil-in-water-in-water Pickering emulsions based on a water-in-water emulsion structure. Background Technology

[0002] Emulsions are colloidal systems consisting of two thermodynamically incompatible phases, where the dispersed phase exists as droplets within the other phase, and the droplet structure is maintained by stabilizers (particles, surfactants). They play a crucial role in the food and pharmaceutical industries as delivery carriers for active components. Dual emulsions, with their unique three-phase, dual-interface structure, can dissolve substances with different solubility properties in different phases, achieving co-encapsulation and delivery of multiple functional substances, controlling the release of active substances, and masking undesirable flavors of functional substances, thus possessing broad market application value.

[0003] Currently common multiple emulsions include oil-in-water-in-oil and water-in-oil-in-water emulsions. However, these emulsions have two oil-water interfaces, and the osmotic pressure difference between the solutions inside and outside the two interfaces makes multiple emulsions prone to demulsification and difficult to stably construct, limiting their industrial applications. There are few reports on the preparation of water-in-oil emulsions. In this emulsion system, only one oil-water interface exists, and the water-in-water emulsion prepared through a pre-contact aqueous two-phase system has no osmotic pressure difference, thus reducing the occurrence of emulsion instability.

[0004] The highly complex microstructure of water-in-oil emulsions necessitates stringent preparation conditions. Currently, the primary method for preparing water-in-oil emulsions is through microfluidic devices (CN108159976A; Stephan Brinkmann, MethodsX, 2021, 8, 101565). However, this method suffers from drawbacks such as excessively large emulsion particle sizes (greater than 50 micrometers), unstable emulsion structures leading to difficulties in collection and storage, and complex and expensive equipment. Therefore, the preparation of water-in-oil emulsions still faces numerous challenges. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing water-in-oil-in-water Pickering emulsions based on a water-in-water emulsion structure, which solves the technical problems of unstable emulsions and complex preparation devices obtained by existing technologies in preparing water-in-oil-in-water multi-interface emulsions.

[0006] To achieve the above objectives, the present invention provides a method for preparing a water-in-oil Pickering emulsion based on a water-in-water emulsion structure, comprising the following steps:

[0007] (1) After mixing the aqueous solutions of the first polymer system and the second polymer system, the water distribution ratio in the two polymer systems is different, that is, the water in the polymer system with weak water retention will migrate to the polymer system with strong water retention; after standing, phase separation occurs, and two phases with different volumes are obtained, in which the smaller phase is used as the aqueous dispersed phase and the larger phase is used as the aqueous continuous phase.

[0008] (2) The solid particle stabilizer is dispersed in the aqueous continuous phase, and then the aqueous dispersed phase is mixed with the aqueous continuous phase in which the solid particle stabilizer is dispersed and emulsified to prepare a water-in-water Pickering emulsion.

[0009] (3) The water-in-water Pickering emulsion is used as the dispersed phase and dispersed in the oil phase by shear emulsification to obtain an oil-in-water-in-water Pickering emulsion.

[0010] Preferably, in step (1), the first polymer system and the second polymer system each independently contain one or more water-soluble polymers, wherein the water-soluble polymers are selected from water-soluble synthetic macromolecules, water-soluble natural polysaccharides, and water-soluble proteins;

[0011] The absolute value of the difference between the solubility parameter of the water-soluble polymer in the first polymer system and the solubility parameter of the water-soluble polymer in the second polymer system relative to water is greater than 0.5.

[0012] The mass percentage concentration of the polymer in the aqueous solution of the first polymer system is 3% to 20%, and the mass percentage concentration of the polymer in the aqueous solution of the second polymer system is 3% to 20%.

[0013] The volume ratio of the aqueous solution of the first polymer system to the aqueous solution of the second polymer system is 1:1 to 1:10.

[0014] Preferably, the particle stabilizer in step (2) is a water-insoluble micro / nano particle, which is one or more of inorganic nanoparticles, organic nanoparticles, and inactivated microorganisms.

[0015] The mass of the solid particulate stabilizer accounts for 0.01% to 1.5% of the total mass of the aqueous continuous phase and the aqueous dispersed phase.

[0016] Preferably, the emulsification in step (2) is impingement flow shear emulsification or microfluidic emulsification; the emulsification temperature is 5–50°C;

[0017] More preferably, the emulsification is impingement emulsification, specifically: the aqueous continuous phase containing the particulate stabilizer is guided by the impingement flow to form two opposing fluids; the aqueous dispersed phase is added to the turbulent zone generated by the two opposing fluids in the impact region; and shear emulsification occurs in the turbulent zone by utilizing the shearing effect of the two opposing fluids to prepare a stable water-in-water Pickering emulsion.

[0018] Preferably, the oil phase in step (3) includes one or more of herbaceous or woody oils, and more preferably one or more of liquid paraffin, rapeseed oil, soybean oil, sunflower oil and tea seed oil.

[0019] Preferably, the oil phase in step (3) further contains an emulsifier, which is a small molecule surfactant and / or a solid particulate emulsifier, wherein the HLB value of the small molecule surfactant is 5-8; and the emulsifier accounts for 0.1-5 wt% of the mass of the oil phase.

[0020] Preferably, the small molecule surfactant emulsifier is a fatty acid or phospholipid emulsifier, and the solid particulate emulsifier is one or more of silica nanoparticles, ethyl cellulose nanoparticles, and natural food waxes.

[0021] Preferably, in step (3), the water-in-water Pickering emulsion is dispersed in the oil phase as a dispersed phase by mechanical stirring or membrane emulsification, wherein the oil phase is a continuous phase, to obtain the water-in-oil emulsion.

[0022] The water-in-water Pickering emulsion should have a particle size of 5-45 micrometers, more preferably 5-30 micrometers, and even more preferably 5-20 micrometers; the viscosity of the water-in-water Pickering emulsion should be less than or equal to 20 Pa·s, more preferably 1-10 Pa·s; and the volume ratio of the water-in-water Pickering emulsion to the oil phase should be 1:9 to 1:1.5.

[0023] Preferably, step (3) involves dispersing the water-in-water Pickering emulsion as a dispersed phase in the oil phase by mechanical stirring. Specifically, the water-in-water Pickering emulsion is added dropwise to the continuous oil phase as a dispersed phase, and the mechanical stirring speed is 300-5,000 rpm.

[0024] Preferably, in step (3), the water-in-water Pickering emulsion is used as the dispersed phase and dispersed in the oil phase by membrane emulsification. The membrane emulsification conditions are: microporous membrane pore size 1-20 micrometers, pore length 50-200 millimeters, emulsification pressure 50-900 kPa.

[0025] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0026] Beneficial effects:

[0027] (1) This invention provides a method for preparing a water-in-oil-in-water-in-water Pickering emulsion based on a water-in-water emulsion. First, an aqueous continuous phase containing a particulate stabilizer is emulsified with an aqueous dispersed phase to prepare a stable water-in-water Pickering emulsion. Then, this water-in-water Pickering emulsion is used as the dispersed phase and further dispersed in the oil phase (continuous phase) to obtain a water-in-oil-in-water Pickering emulsion. Compared to a water-in-oil-in-water emulsion system, the water-in-oil-in-water emulsion structure prepared by this invention contains two immiscible aqueous phases. By controlling the properties of the aqueous phases, the distribution ratio of water-soluble functional components in the two aqueous phases can be controlled, further improving its stability.

[0028] (2) The water-in-oil pickering emulsion prepared by the method of the present invention has good biocompatibility and a crossable water-water interface. Compared with water-in-oil emulsions prepared by microfluidics and other methods, in the method of the present invention, the two aqueous phases also undergo significant phase separation through blending contact before the emulsion is formed, thus the constructed water-in-oil pickering emulsion is more stable as an internal phase.

[0029] (3) The water-in-oil emulsion prepared by the method of this invention has a controllable particle size, and the particle size of the internal aqueous phase emulsion system is also controllable, exhibiting excellent physical stability. Therefore, the water-in-oil emulsion provided by this invention has wide applications in food, cosmetics, pharmaceuticals, and microbial reactors. The prepared water-in-oil Pickering emulsion is stable during storage and can be used as a delivery carrier to simultaneously deliver water-soluble and oil-soluble nutrients.

[0030] (4) The apparatus of the method described in this invention has a simple structure and is easy to scale up for industrial production. This emulsification method is a low-energy emulsification method, which does not require complex production equipment, high-temperature and high-pressure treatment, is simple and easy to implement, has high process efficiency, and the emulsion particle size is controllable. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for preparing water-in-oil Pickering emulsions based on water-in-water emulsions according to the present invention;

[0032] Figure 2 This is a typical phase diagram of the aqueous two-phase system for constructing a water-in-water emulsion in an embodiment of the present invention;

[0033] Figure 3 These are microscopic images of the water-in-water emulsion in Embodiment 3 of the present invention;

[0034] Figure 4 These are typical microscopic images of the water-in-oil emulsions prepared in the embodiments of the present invention. Content a is Example 3, content b is Example 4, content c is Example 5, and content d is Example 6.

[0035] Figure 5 This is a diagram of the water-in-oil emulsion prepared in Example 7 of the present invention by mechanical stirring (a), high-speed shearing (b), and membrane emulsification (c).

[0036] Figure 6 The images show photographs of the failure to form a water-in-oil emulsion under the conditions of Comparative Example 3 (Content a), and photographs of the water-in-oil emulsions in Examples 1 (Content b) and 6 (Content c) after one month of storage. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] This invention provides a novel method for preparing a water-in-oil pickering emulsion. The method first prepares a stable water-in-oil pickering emulsion (refer to patent document CN112210087A), then further disperses this water-in-oil pickering emulsion as a dispersed phase in an oil phase (external continuous phase) to obtain the water-in-oil pickering emulsion. The water-in-oil pickering emulsion comprises an aqueous continuous phase, an aqueous dispersed phase, and a solid particle stabilizer; it is an emulsion obtained by encapsulating the aqueous dispersed phase with an aqueous continuous phase emulsified using a solid particle stabilizer as an emulsifier. Both the aqueous continuous phase and the aqueous dispersed phase are aqueous solutions of water-soluble polymers, and they are immiscible. Furthermore, the oil phase, i.e., the external continuous phase, includes liquid oil and an emulsifier, which is a small molecule surfactant and / or a solid particle emulsifier.

[0039] This invention proposes a novel approach to preparing water-in-oil emulsions. First, a water-in-water emulsion is prepared, and then it is dispersed in an oil phase to obtain the water-in-oil emulsion. The stable construction of the water-in-water emulsion is crucial for the preparation of water-in-oil emulsions. Due to the extremely low interfacial tension and thick interfacial layer of water-in-water emulsions, they cannot be stabilized by surfactants, and phase separation and instability occur within hours or days. Therefore, their unstable nature significantly hinders the progress of research on water-in-oil emulsions. The applicant's prior patent application CN112210087A prepared various water-in-water Pickering emulsions that can maintain long-term stability. This invention, based on the previous preparation of Pickering water-in-water emulsions, has unique advantages in preparing water-in-oil emulsions. Furthermore, experiments revealed that the choice of oil phase and oil-water interface stabilizer significantly affects the effect of the external oil phase encapsulating the dispersed phase of the water-in-oil emulsion during the construction of the water-in-oil emulsion. Currently, there are few reports on the selection of the external oil phase in water-in-oil emulsions.

[0040] This invention provides a method for preparing water-in-oil, water-in-water Pickering emulsions based on a water-in-water emulsion structure, such as... Figure 1 As shown, it includes the following steps:

[0041] (1) After mixing the aqueous solution A of the first polymer system and the aqueous solution B of the second polymer system, the mixture is allowed to stand, resulting in phase separation and two phases of different volumes. The phase with smaller volume is taken as the aqueous dispersed phase, and the phase with larger volume is taken as the aqueous continuous phase. The first polymer system contains one or more water-soluble polymers, and the second polymer system contains one or more water-soluble polymers. The absolute value of the difference between the solubility parameter of the water-soluble polymer in the first polymer system relative to water and the solubility parameter of the water-soluble polymer in the second polymer system relative to water is greater than 0.5.

[0042] (2) The solid particle stabilizer is dispersed in the aqueous continuous phase, and then the aqueous dispersed phase is mixed with the aqueous continuous phase in which the solid particle stabilizer is dispersed and emulsified to prepare a water-in-water Pickering emulsion.

[0043] (3) The water-in-water Pickering emulsion is dispersed in the oil phase by shear emulsification to obtain an oil-in-water-in-water Pickering emulsion.

[0044] The prerequisite for constructing a stable water-in-oil emulsion in this invention is the construction of a water-in-water Pickering emulsion with suitable particle size and viscosity. Based on previous patent literature (CN112210087A), in order to obtain an aqueous dispersed phase and an aqueous continuous phase capable of phase separation when preparing a water-in-water Pickering emulsion, the following steps are necessary: ​​First, select suitable polymer types, i.e., the absolute value of the difference between the solubility parameter of the first water-soluble polymer relative to water and the solubility parameter of the second water-soluble polymer relative to water is greater than 0.5 (the solubility parameter can be obtained by looking up a table, or it can be preliminarily calculated according to theoretical parameters, or measured by conventional methods); second, it is necessary to experimentally determine the phase diagram of the mixing of the two polymer solutions (e.g., ...). Figure 2 According to the phase diagram, the phase separation region (the hollow icon region in the figure) is obtained, and then the concentration and volume ratio of the aqueous solution of the first polymer system and the aqueous solution of the second polymer system are controlled within a suitable range so that the two aqueous solutions can undergo phase separation.

[0045] In some embodiments, the water-soluble polymer used in the preparation of the water-in-water Pickering emulsion may refer to a water-soluble macromolecule with a relative molecular mass ranging from several thousand to several million, selected from water-soluble synthetic macromolecular polymers, water-soluble natural polysaccharides, and water-soluble proteins. The water-soluble synthetic macromolecular polymers include, but are not limited to, polyethylene glycol, polyvinyl alcohol, or polyethylene oxide; the water-soluble natural polysaccharides include, but are not limited to, starch, pullulan, dextran, chitosan, konjac glucomannan, dextrin, carrageenan, or guar gum; and the water-soluble proteins include, but are not limited to, gelatin, collagen, or casein. The absolute value of the difference between the solubility parameter of the first water-soluble polymer relative to water and the solubility parameter of the second water-soluble polymer relative to water is greater than 0.5. The mass percentage concentration of the polymer in the aqueous solution of the first polymer system is 3% to 20%, preferably 5% to 20%; the mass percentage concentration of the polymer in the aqueous solution of the second polymer system is 3% to 20%, preferably 5% to 20%; the volume ratio of the aqueous solution of the first polymer system to the aqueous solution of the second polymer system is 1:1 to 1:10; preferably 1:3 to 1:4, to obtain a continuous aqueous phase and a dispersed aqueous phase that undergo phase separation.

[0046] The particle stabilizer used in step (1) of this invention functions similarly to the emulsifier used in traditional emulsion preparation. If the particle stabilizer content is too low, it will not provide a stabilizing effect; if the content is too high, it will disrupt the stability of the two phases. In some embodiments of this invention, the mass fraction of the particle stabilizer in the aqueous continuous phase with dispersed particle stabilizer is 0.01% to 1.5%, preferably 0.5% to 1.1%. Any water-insoluble solid particle stabilizer capable of emulsifying and stabilizing can meet the preparation requirements of this invention. This solid particle stabilizer can be a solid particle stabilizer with a particle size range of 5 nanometers to 20 micrometers, or a fibrous solid particle stabilizer with a diameter between 5 nanometers and 5 micrometers. In some embodiments, the particle stabilizer is a water-insoluble micro / nano particle, which is one or more of inorganic nanoparticles, organic nanoparticles, and microorganisms. The organic nanoparticles include, but are not limited to, one or more of water-insoluble polysaccharide nanoparticles, protein nanoparticles, and lipid nanoparticles; for example, cellulose solid particles, polysaccharide / protein composite solid particles (e.g., cellulose / soy protein isolate solid particle complex), where polysaccharide / protein composite solid particles refer to water-insoluble complexes formed by physical or chemical modification of polysaccharides and proteins. The inorganic nanoparticles include, but are not limited to, one or more of calcium carbonate, silica, palladium, and graphene (e.g., graphene nanosheets); the microorganisms include, but are not limited to, inactivated yeast and other microorganisms.

[0047] In step (2) of this invention, the preferred emulsification method is the impingement flow method. When preparing a water-in-water Pickering emulsion, the selection of the specific impingement flow liquid for emulsification and how to stabilize the water-in-water emulsion system are crucial. Traditional impingement methods involve direct impact dispersion and emulsification between two phases, such as in oil-in-water or water-in-oil emulsions, where dispersion and emulsification are achieved directly through the impact of the aqueous and oil phases. In the impingement flow method used in this invention, the two impacting liquid phases are the same phase, i.e., a continuous phase, while the dispersed phase is added through a pipe between the surfaces of the two impacting continuous phases. Specifically, this invention utilizes impingement flow-assisted emulsification technology, first adding a particle stabilizer to the continuous phase, and then using the shearing effect of the impingement flow to generate a stable water-in-water Pickering emulsion in one step. The principle is that the continuous phase solution generates two opposing impacting fluids through the guiding effect of the internal components of the reactor, creating an annular liquid phase film in the intermediate region. The dispersed phase is then added through a conduit to a narrow, highly turbulent region constructed from two continuous phases. Shear emulsification occurs within this region, utilizing the shearing action of the two continuous phase impacting flows to generate a stable water-in-water Pickering emulsion in one step. Because the propellers in the upper and lower guide tubes mounted on the same shaft point in opposite directions, they provide strong shear forces in all directions at the impact surface of the annular liquid film. The force of these shear forces increases with decreasing jet diameter and increasing flow velocity, effectively dispersing and emulsifying the liquid. In some embodiments, the impacting flow device is a dual-nozzle impacting flow device with a jet diameter of 0.1-5 mm, preferably 0.2-3 mm; the flow velocity of the liquid ejected from the impact nozzles, i.e., the jet orifice, is 0.5-20 m / s, preferably 1.0-10 m / s. To enhance the emulsification effect, the impinging flow device includes two coaxial and oppositely arranged guide tubes. The guiding effect of the two guide tubes generates two opposing fluid streams. Each of the two guide tubes contains a propeller for controlling the direction of fluid movement, and the propellers in the two guide tubes rotate in opposite directions. An aqueous continuous phase containing a particulate stabilizer is injected into the impinging flow device, and the guiding effect of the two guide tubes generates two opposing continuous phase fluid streams.

[0048] Traditional mechanical stirring methods cannot effectively control the particle size distribution of water-in-water Pickering emulsions; high-pressure homogenization, due to excessive local ultrasonic field intensity, easily breaks macromolecular chains, causing degradation and disrupting the stability of the water-water interface. In the experimental process of this invention, traditional emulsification methods, including mechanical stirring and high-pressure homogenization, were used on the same system, but stable water-in-water Pickering emulsions could not be obtained. However, this invention utilizes impinging flow-assisted emulsification technology, introducing a particle stabilizer into the continuous phase beforehand, and adding the dispersed phase dropwise in the highly turbulent region formed by two colliding fluids. This one-step shear emulsification, leveraging the shearing effect of the impinging flow and the emulsifying effect of the particle stabilizer, successfully achieves stable preparation of water-in-water Pickering emulsions for water-soluble polymers, with controllable emulsion particle size. This process provides a strong guarantee for the construction of oil-in-water-in-water Pickering emulsions.

[0049] In some embodiments, the water-in-water Pickering emulsion prepared according to the present invention is used as the dispersed phase and dispersed in the oil phase (external continuous phase) by shear emulsification to obtain a water-in-oil Pickering emulsion. The oil phase is a continuous phase. In some embodiments, the oil phase in step (3) contains one or more of herbal or woody oils, preferably one or more of liquid paraffin, rapeseed oil, soybean oil, sunflower seed oil, and tea seed oil. In some embodiments, the oil phase also contains an emulsifier, which is a small molecule surfactant and / or a solid particulate emulsifier, more preferably a solid particulate emulsifier; the emulsifier accounts for 0.1-5 wt% of the mass of the oil phase. The small molecule surface emulsifiers include fatty acid emulsifiers, phospholipid emulsifiers, etc. Fatty acid emulsifiers include, but are not limited to, lauric acid, palmitic acid, polyglycerol ricinoleate, diethylene glycol monolaurate, etc.; phospholipid emulsifiers include, but are not limited to, lecithin, phosphatidylcholine, etc.; the solid particulate emulsifiers include, for example, silica nanoparticles, ethyl cellulose nanoparticles, natural food waxes, etc. Natural food waxes include, but are not limited to, beeswax, insect wax, palm wax, etc.

[0050] Experiments revealed that further requirements exist regarding the properties of the water-in-water pickering emulsion during the preparation of water-in-oil emulsions. In the embodiments of this invention, water-in-water pickering emulsions with a particle size range of 5-45 micrometers can be prepared. However, when the particle size of the water-in-water emulsion is greater than or equal to 50 micrometers, it cannot be encapsulated by the oil phase, thus preventing the formation of a water-in-oil emulsion. Therefore, when preparing water-in-oil emulsions using the water-in-water pickering emulsion according to the method of this invention, the particle size of the water-in-water pickering emulsion must be controlled to be less than 45 micrometers, for example, within the range of 5-45 micrometers, preferably 5-30 micrometers.

[0051] Step (3) The water-in-water Pickering emulsion is dispersed in the oil phase by mechanical stirring or membrane emulsification as the dispersed phase, and the oil phase is a continuous phase to obtain the water-in-oil emulsion; the volume ratio of the water-in-water Pickering emulsion to the oil phase is 1:9 to 4:6.

[0052] In some embodiments, step (3) involves dispersing the water-in-water Pickering emulsion as a dispersed phase in the oil phase by mechanical stirring. Specifically, the water-in-water Pickering emulsion is added dropwise to the continuous oil phase as a dispersed phase, and the mechanical stirring speed is 300-5,000 rpm, preferably 300-600 rpm.

[0053] In some embodiments, to control the emulsion particle size and improve particle size uniformity, membrane emulsification was used to disperse the aqueous phase dispersion (water-in-water Pickering emulsion) from step (3) into the oil phase continuous phase. The membrane emulsification conditions were: microporous membrane pore size 1-20 micrometers, pore length 50-200 millimeters, emulsification pressure 50-900 kPa. Preferably, the microporous membrane pore size was 5-10 micrometers, pore length 80-125 millimeters, emulsification pressure 200-300 kPa, and the batch-to-batch variation of the resulting water-in-oil emulsion particle size could be controlled within 6%. Experiments showed that when preparing water-in-oil emulsions using membrane emulsification, the viscosity of the water-in-water Pickering emulsion should be below 20 Pa·s, with a preferred viscosity of 1-10 Pa·s. When the viscosity of a water-in-water emulsion is too high, it is difficult to detach when passing through a microporous membrane, which will form a large group of water-in-water emulsion droplets that cannot be encapsulated by the oil phase, making it difficult to form a water-in-oil emulsion.

[0054] In step (3) of this invention, a water-in-water emulsion is dispersed as a dispersed phase in an oil phase. The oil phase contains an emulsifier, which can be a small molecule surfactant or a solid particulate emulsifier. Experiments have shown that when using a small molecule surfactant as an emulsifier, if its HLB value is too low, the emulsifier's emulsifying ability is too strong, and the emulsifier tends to be distributed within the oil phase rather than at the oil-water interface, making it difficult to construct a water-in-oil emulsion. The preferred HLB value range for the small molecule surfactant emulsifier is 5-8, more preferably 6-7.

[0055] In some preferred embodiments, ethyl cellulose nanoparticles, a solid particulate emulsifier, are used to stabilize the oil-water interface. Compared to small-molecule surfactants, solid particulate emulsifiers can be irreversibly adsorbed at the oil-water interface, stabilizing emulsion droplets by forming an elastic interfacial film. Furthermore, solid particles can reduce droplet collisions by enhancing steric hindrance and electrostatic repulsion between droplets, thereby improving emulsion stability. Additionally, compared to water-in-oil emulsions stabilized by small-molecule surfactants, water-in-oil emulsions stabilized by solid particulate emulsifiers have higher viscosity, thus exhibiting better physical stability. In some embodiments, small-molecule surfactants and solid particulate emulsifiers are simultaneously added to the oil phase to synergistically emulsify and stabilize the water-in-oil emulsion, resulting in an emulsion with smaller particle size and better physical stability.

[0056] In some preferred embodiments, natural food waxes such as beeswax, insect wax, and palm wax are used as stabilizers for water-in-oil emulsions. First, the mixed oil phase is heated until completely melted. Then, under mechanical stirring at room temperature, the water-in-water Pickering emulsion is added dropwise to the mixed oil phase containing natural waxes. During the cooling process, the natural waxes form wax crystals. Some of these crystals are adsorbed at the oil-water interface, while the remaining large number of wax crystals are distributed within the oil phase to form a crystal network. This increases the viscosity of the water-in-oil emulsion, hinders the movement and collision of emulsion droplets, and thus improves the stability of the water-in-oil emulsion.

[0057] In some embodiments, when natural food wax is used as an emulsifier, its concentration in the oil phase is 1-5 wt%. In preferred embodiments, the concentration of natural food wax emulsifier in the oil phase is 2-4 wt%. If the concentration of natural food wax is too low, the viscosity of the outer oil phase is low, and the physical stability of the resulting water-in-oil emulsion is relatively poor. If the concentration of natural food wax is too high, it may crystallize rapidly in the outer oil phase, forming a crystal network that solidifies the outer oil phase, thus preventing the formation of a water-in-oil emulsion.

[0058] Currently, although there are related patent reports on the research of water-in-oil emulsions, such as CN108159976A, which uses a special microfluidic device to prepare a water-in-oil emulsion based on polyethylene glycol and dextran aqueous solution as the aqueous two-phase and liquid paraffin as the oil phase, this emulsion is a type of emulsion stabilized by traditional small molecule surfactants. In the process of preparing this emulsion, the aqueous two-phase components are not subjected to contact treatment before emulsification, and the osmotic pressure of the aqueous dispersed phase and the aqueous continuous phase is unbalanced, which leads to the instability of the water-in-oil emulsion prepared by this method (see the attached figure of the patent document).

[0059] This invention, based on the characteristics and preparation process of water-in-oil emulsions, first prepares a water-in-oil pickering emulsion with a small particle size through impingement emulsification, achieving uniform and controllable particle size. Before preparing the water-in-oil pickering emulsion, the two aqueous solutions are first mixed to induce phase separation. The smaller volume fraction is then used as the dispersed phase, while the larger volume aqueous phase is used as the continuous phase. Furthermore, solid particles act as particle stabilizers, irreversibly adsorbing at the water-water interface to construct the water-in-oil pickering emulsion, further improving its stability. In this invention, the prepared water-in-oil pickering emulsion is dispersed into an oil phase containing an emulsifier through mechanical stirring or membrane emulsification, resulting in a simple method that facilitates large-scale preparation.

[0060] This invention uses a stable water-in-water Pickering emulsion as the dispersed phase and an oil phase as the external continuous phase to prepare a water-in-oil emulsion. The prepared water-in-oil emulsion has a particle size of 15-100 micrometers and exhibits good stability, maintaining its water-in-oil emulsion morphology even after one month of storage. In a preferred embodiment, its emulsification index is 50-100%. The water-in-oil emulsion prepared by this invention can be used for the co-encapsulation and delivery of various nutrients.

[0061] The following are specific examples:

[0062] Comparative Example 1

[0063] Weigh 10 grams of maltodextrin powder (molecular weight 3,000 Da, solubility parameter 25.1 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³) in 40 g of deionized water to prepare a 20% maltodextrin aqueous solution A.) 3 ) 0.5 Dissolve in 40g of deionized water to prepare a 20% (w / w) dextran aqueous solution B. Weigh 0.5g of glyceryl monostearate (HLB value 3.8) and add it to 49.5g of rapeseed oil to prepare the outer oil phase for later use.

[0064] Take 10 mL of maltodextrin aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.7% (w / w) of soybean protein isolate nanoparticles (Zeta potential -20 mV) to the continuous phase and mix thoroughly. Place the continuous phase containing the nanoparticle stabilizer inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 15 micrometers and a viscosity of 6.5 Pa·s.

[0065] Ten milliliters of the water-in-oil emulsion prepared above were transferred as the dispersed phase and added dropwise to 30 milliliters of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 25°C). The mixture was stirred continuously for 30 minutes to obtain the emulsion. Microscopic observation of the emulsion revealed that the system consisted of uniformly dispersed droplets, but did not exhibit a multiple emulsion morphology, and did not form a water-in-oil emulsion. Further testing revealed that when a drop of the product was added to water, the emulsion agglomerated without dispersing; conversely, when added to rapeseed oil, the emulsion dispersed rapidly. Therefore, the prepared emulsion was a single water-in-oil emulsion. The reason for this may be that the emulsifier used, glyceryl stearate, has an HLB value of 3.8, which has a very strong emulsifying effect on the formation of water-in-oil emulsions, thus favoring the formation of a single water-in-oil emulsion.

[0066] Comparative Example 2

[0067] Weigh 10 grams of maltodextrin powder (molecular weight 3,000 Da, solubility parameter 25.1 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³) in 40 g of deionized water to prepare a 20% maltodextrin aqueous solution A.) 3 ) 0.5 Dissolve in 40g of deionized water to prepare a 20% (w / w) dextran aqueous solution B. Weigh 0.5g of polyglycerol ricinoleate (HLB value 7.0) and add it to 49.5g of soybean oil to prepare the outer oil phase for later use.

[0068] Take 10 mL of maltodextrin aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. These two phases are then separated. The aqueous continuous phase is placed inside an impinging flow apparatus. Under the action of the flow guiding component, it passes through the nozzle of the apparatus, forming two opposing colliding fluid streams (the impinging nozzle diameter is 0.1 mm, the ejection velocity is 1 m / s, and the ambient temperature is 25℃). The dispersed phase is added to the turbulent zone formed by this impingement region, and emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 25 micrometers and a viscosity of 5.9 Pa·s.

[0069] Ten mL of the prepared water-in-water emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 25°C). Stirring was continued at 25°C for 30 minutes to obtain the emulsion. Microscopic observation of the freshly prepared emulsion revealed a typical, uniformly dispersed multiphase emulsion morphology, specifically a water-in-oil emulsion with a particle size of approximately 35 micrometers. However, after standing at room temperature for 3 hours, phase separation occurred within the aqueous two-phase emulsion system of the droplets, and the overall emulsion exhibited a Jauns emulsion morphology. This may be due to the absence of a solid particle stabilizer during the preparation of the water-in-water emulsion, leading to instability and preventing long-term stability of the final multiphase emulsion morphology. This experiment demonstrates that constructing a stable water-in-water Pickering emulsion is fundamental to the preparation of water-in-oil emulsions.

[0070] Comparative Example 3

[0071] Weigh 20 grams of maltodextrin powder (molecular weight 3,000 Da, solubility parameter 25.1 (Cal / cm³)). 3 ) 0.5 Dissolve maltodextrin in 30g of deionized water to prepare a 40% (w / w) maltodextrin aqueous solution A. Weigh 20g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve in 30g of deionized water to prepare a 40% (w / w) dextran aqueous solution B. Weigh 0.5g of polyglycerol ricinoleate and add it to 49g of rapeseed oil to prepare the outer oil phase for later use.

[0072] Take 10 mL of maltodextrin aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take both phases out separately. Add 0.7% (w / w) of soybean protein isolate nanoparticles (Zeta potential -20 mV) to the continuous phase and mix thoroughly. Place the continuous phase containing the nanoparticle stabilizer inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 3 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 50 micrometers and a viscosity of 6.5 Pa·s.

[0073] 10 mL of the water-in-water emulsion prepared above was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical stirring (stirring speed: 1,000 rpm; stirring temperature: 25°C). Stirring was continued for 30 minutes to obtain the emulsion. Microscopic observation of the emulsion revealed that the system consisted of uniformly dispersed droplets, but did not exhibit a multiple emulsion morphology, nor did it form a water-in-oil emulsion. Macroscopic observation of the system was also conducted. Freshly prepared emulsion was shaken and placed in a glass bottle; after 3 minutes, its macroscopic appearance was observed as follows. Figure 6 As shown in section a, the system rapidly separates into distinct oil and water layers. This may be because the polymer concentrations in both phases are high during the preparation of the water-in-water emulsion, resulting in lower impact velocities and less shear force from turbulence. Consequently, the resulting water-in-water emulsion has excessively large particle sizes, making it difficult for the oil phase to encapsulate them.

[0074] Example 1

[0075] Weigh 10 grams of maltodextrin powder (molecular weight 3,000 Da, solubility parameter 25.1 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³) in 40 g of deionized water to prepare a 20% maltodextrin aqueous solution A.) 3 ) 0.5 Dissolve in 40g of deionized water to prepare a 20% (w / w) dextran aqueous solution B. Weigh 0.5g of polyglycerol ricinoleate (HLB value 7.0) and add it to 49.5g of rapeseed oil to prepare the outer oil phase for later use.

[0076] Take 10 mL of maltodextrin aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.7% (w / w) of soybean protein isolate nanoparticles (Zeta potential -20 mV) to the continuous phase and mix thoroughly. Place the continuous phase containing the nanoparticle stabilizer inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 15 micrometers and a viscosity of 6.5 Pa·s.

[0077] Ten mL of the water-in-water emulsion prepared above was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 25°C). Stirring was continued for 30 minutes to obtain a water-in-oil emulsion. The obtained water-in-oil emulsion had a particle size of approximately 35 micrometers. After standing at room temperature for 1 hour, the emulsion exhibited rapid stratification instability and eventually reached a stable stratification state. A macroscopic photograph of this emulsion is shown below. Figure 6 As shown in content b, the emulsification index is 38%.

[0078] Example 2

[0079] Weigh 10 grams of polyethylene glycol powder (molecular weight 88,000 Da, solubility parameter 9.38 (Cal / cm³)). 3 ) 0.5 Dissolve the following in 40 grams of deionized water to prepare a 20% (w / w) polyethylene glycol aqueous solution A; weigh 10 grams of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 20% (w / w) dextran in 40g of deionized water to prepare a 20% (w / w) aqueous solution B; weigh 0.5g of diethylene glycol monolaurate (HLB value 6.1) and add it to 49.5g of soybean oil to prepare the outer oil phase for later use.

[0080] Take 10 mL of polyethylene glycol aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.7% (w / w) of bacterial cellulose nanocrystals (Zeta potential -37 mV) to the continuous phase and mix thoroughly. Place the continuous phase containing the solid stable particles inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1 m / s, ambient temperature 20℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 8 micrometers and a viscosity of 3.1 Pa·s.

[0081] Ten mL of the water-in-water emulsion prepared above was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 25°C). The mixture was stirred continuously for 30 minutes to obtain a water-in-oil emulsion. The obtained water-in-oil emulsion had a particle size of approximately 30 micrometers and an emulsification index of 45% after being left at room temperature for one month.

[0082] Example 3

[0083] Weigh 10 grams of polyethylene glycol powder (molecular weight 88,000 Da, solubility parameter 9.38 (Cal / cm³)). 3 ) 0.5 Dissolve the following in 40 grams of deionized water to prepare a 20% (w / w) polyethylene glycol aqueous solution A; weigh 10 grams of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 20% (w / w) dextran in 40g of deionized water to prepare a 20% (w / w) aqueous solution B; weigh 1g of ethyl cellulose and add it to 49g of soybean oil to prepare the outer oil phase for later use.

[0084] Take 10 mL of polyethylene glycol aqueous solution A and 40 mL of dextran aqueous solution B, mix them thoroughly, and allow them to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.7% (w / w) of bacterial cellulose nanocrystals (Zeta potential -37 mV) to the continuous phase and mix thoroughly. Place the continuous phase containing the solid stable particles inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1 m / s, ambient temperature 20℃). Add the dispersed phase to the turbulent zone formed by the impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. Its microscopic image is shown below. Figure 3As shown, the droplets are uniformly dispersed. The resulting emulsion has a particle size of approximately 8 micrometers and a viscosity of 3.1 Pa·s.

[0085] Ten mL of the water-in-oil emulsion prepared above was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:3) under mechanical shear conditions (shear rate: 5,000 rpm; shear time: 2 min). The mixture was stirred continuously for 10 min to obtain the emulsion. The microscopic image of the prepared water-in-oil emulsion is shown below. Figure 4 Content a presents a typical double emulsion structure, with an oil-in-water-in-water emulsion particle size of approximately 25 micrometers. After being left at room temperature for one month, the emulsification index is 78%. Compared to the oil-in-water emulsions stabilized by small molecule surfactants (polyglycerol ricinoleate and diethylene glycol monolaurate, respectively) in Examples 1 and 2, the oil-in-water emulsion stabilized by solid ethyl cellulose particles in this example exhibits better physical stability. This may be due to the irreversible adsorption of monoethyl cellulose nanoparticles at the oil-water interface, forming an interfacial film that enhances the steric hindrance and electrostatic repulsion interactions between emulsion droplets, reducing droplet collisions. Furthermore, compared to Examples 1 and 2, the emulsion prepared in this example has a higher viscosity value, thus exhibiting better physical stability.

[0086] Example 4

[0087] Weigh 10 grams of cold-water fish skin gelatin powder (molecular weight 300,000 Da, solubility parameter 23.8 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder in 40 g of deionized water to prepare a 20% (w / w) gelatin aqueous solution A; weigh 10 g of dextran powder (molecular weight 120,000 Da, solubility parameter 20.3 (Cal / cm³)). 3 ) 0.5 Dissolve 1 gram of beeswax in 40 grams of deionized water to prepare a 20% (w / w) dextran aqueous solution B; weigh 1 gram of beeswax and add it to 49 grams of rapeseed oil, heat at 75°C until the beeswax is completely dissolved, mix well, and prepare the outer oil phase for later use.

[0088] Take 10 mL of gelatin aqueous solution A and 30 mL of dextran aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Separate the two phases. Add 0.7% (w / w) of chitin nanocrystals (Zeta potential -30 mV) to the continuous phase. Place the continuous phase inside an impinging flow apparatus. Under the action of the flow guiding component, the continuous phase passes through the jet nozzle of the apparatus, forming two opposing colliding fluids (impinging nozzle diameter 0.1 mm, jet velocity 1.2 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by the impact, and emulsification is completed under the shearing action of the turbulence to prepare a water-in-water emulsion. The resulting emulsion has a particle size of approximately 15 micrometers and a viscosity of 4.5 Pa·s.

[0089] The external oil phase was heated to 75°C until completely dissolved. 20 mL of the prepared water-in-oil emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio 1:1.5) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 25°C). Stirring was continued for 5 hours (stirring speed: 300 rpm; stirring temperature: 25°C) to obtain a water-in-oil emulsion. The freshly prepared emulsion was observed under a microscope, and its microscopic image is shown below. Figure 4 As shown in content b, the emulsion system is a typical, uniformly dispersed multiple emulsion with a particle size of approximately 40 micrometers. After the above water-in-oil emulsion was left at room temperature for one month, it still exhibited a stable dual emulsion state with an emulsification index of 80%.

[0090] Example 5

[0091] Weigh 10 grams of cold-water fish skin gelatin powder (molecular weight 300,000 Da, solubility parameter 23.8 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder in 40 g of deionized water to prepare a 20% (w / w) gelatin aqueous solution A; weigh 10 g of dextran powder (molecular weight 120,000 Da, solubility parameter 20.3 (Cal / cm³)). 3 ) 0.5 Dissolve 2.5 g of beeswax in 40 g of deionized water to prepare a 20% (w / w) dextran aqueous solution B; weigh 2.5 g of beeswax and add it to 47.5 g of rapeseed oil, heat at 75°C until the beeswax is completely dissolved, mix well, and prepare the outer oil phase for later use.

[0092] Take 10 mL of gelatin aqueous solution A and 30 mL of dextran aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Separate the two phases. Add 0.7% (w / w) of chitin nanocrystals (Zeta potential -30 mV) to the continuous phase. Place the continuous phase inside an impinging flow apparatus. Under the action of the flow guiding component, the continuous phase passes through the jet nozzle of the apparatus, forming two opposing colliding fluids (impinging nozzle diameter 0.1 mm, jet velocity 1.2 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by the impact, and emulsification is completed under the shearing action of the turbulence to prepare a water-in-water emulsion. The resulting emulsion has a particle size of approximately 15 micrometers and a viscosity of 4.5 Pa·s. The external oil phase was heated to 75°C until completely dissolved. At room temperature, 20 mL of the prepared water-in-oil emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio 1:1.5) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 20°C). Stirring was continued for 5 hours (stirring speed: 300 rpm; stirring temperature: 25°C) to obtain the water-in-oil emulsion. Observation... Figure 4 The microscopic image of the water-in-oil emulsion shown in content c indicates that the emulsion system exhibits a typical multi-emulsion morphology with uniform dispersion and a particle size of approximately 30 micrometers. Compared to the water-in-oil emulsion prepared in Example 4, the water-in-oil emulsion prepared in this example has a smaller particle size. This is due to the increased beeswax concentration, which improves the coating rate of the emulsion droplets and thus reduces the particle size. After being placed at room temperature for one month, the above-mentioned water-in-oil emulsion still exhibits a stable double emulsion state with an emulsification index of 90%. Compared to the water-in-oil emulsion prepared in Example 4, the water-in-oil emulsion obtained in this example has a higher beeswax content in the outer oil phase, forming a denser lipid crystal network in the outer oil phase. This increases the viscosity of the emulsion, reduces the droplet collision frequency, and improves the stability of the emulsion.

[0093] Example 6

[0094] Weigh 10 grams of cold-water fish skin gelatin powder (molecular weight 300,000 Da, solubility parameter 23.8 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder in 40 g of deionized water to prepare a 20% (w / w) gelatin aqueous solution A; weigh 10 g of dextran powder (molecular weight 120,000 Da, solubility parameter 20.3 (Cal / cm³)). 3 ) 0.5Dissolve in 40g of deionized water to prepare a 20% (w / w) dextran aqueous solution B; weigh 2.5g of beeswax and 0.5g of ethyl cellulose powder and add to 47.5g of sunflower seed oil, heat at 75℃ until the beeswax is completely dissolved, mix all components, and prepare the outer oil phase for later use.

[0095] Take 10 mL of gelatin aqueous solution A and 30 mL of dextran aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Separate the two phases. Add 0.7% (w / w) of chitin nanocrystals (Zeta potential -30 mV) to the continuous phase. Place the continuous phase inside an impinging flow apparatus. Under the action of the flow guiding component, the continuous phase passes through the nozzle of the apparatus, forming two opposing colliding fluid streams (impinging nozzle diameter 0.1 mm, ejection velocity 1.2 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by the impact, and emulsification is completed under the shearing action of the turbulence to prepare a water-in-water emulsion. The resulting emulsion has a particle size of approximately 15 micrometers and a viscosity of 4.5 Pa·s. The external oil phase was heated to 75°C until completely dissolved. At room temperature, 20 mL of the prepared water-in-oil emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio 1:1.5) under mechanical stirring (stirring speed: 600 rpm; stirring temperature: 20°C). Stirring was continued for 5 hours (stirring speed: 600 rpm; stirring temperature: 25°C) to obtain a water-in-oil emulsion. The freshly prepared emulsion was observed under a microscope, and the image is shown below. Figure 4 As shown in content d, the emulsion system is a typical, uniformly dispersed multiple emulsion, with a particle size of approximately 28 micrometers. A macroscopic photograph of the emulsion after 30 days at room temperature is shown below. Figure 6 As shown in section c, the emulsion system did not exhibit stratification and remained an oil-in-water-in-water emulsion, thus demonstrating good physical stability. The emulsification index was 100%. Compared to the water-in-oil emulsion prepared in Example 5, the water-in-oil emulsion prepared in this example exhibits higher stability. This is because the addition of ethyl cellulose particles synergistically stabilizes the water-in-oil emulsion with the beeswax lipid particles.

[0096] Example 7

[0097] Weigh 10 grams of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 5 grams of hydroxypropyl methylcellulose powder (molecular weight 80,000 Da, viscosity 15 Pa·s, solubility parameter 18.3 (Cal / cm³) in 40 grams of deionized water to prepare a 20% (w / w) dextran aqueous solution A; weigh 5 grams of hydroxypropyl methylcellulose powder (molecular weight 80,000 Da, viscosity 15 Pa·s, solubility parameter 18.3 (Cal / cm³)). 3 ) 0.5Dissolve 10% hydroxypropyl methylcellulose in 45g of deionized water to prepare a 10% aqueous solution B of hydroxypropyl methylcellulose; weigh 2.5g of beeswax and 0.5g of ethyl cellulose powder and add them to 47.5g of sunflower seed oil, heat at 75℃ until the beeswax is completely dissolved, mix all the ingredients, and prepare the outer oil phase for later use.

[0098] Take 10 mL of dextran aqueous solution A and 40 mL of hydroxypropyl methylcellulose aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.5% (w / w) cellulose nanocrystals (Zeta potential -40 mV) to the continuous phase. Place the continuous phase inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 4 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 13 micrometers and a viscosity of 8 Pa·s.

[0099] The external oil phase was heated to 75°C until completely dissolved. 20 mL of the prepared water-in-oil emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio 1:1.5) under mechanical stirring (stirring speed: 300 rpm; stirring temperature: 25°C). Stirring was continued for 3 hours (stirring speed: 300 rpm; stirring temperature: 25°C) to obtain a water-in-oil emulsion. Figure 4 As shown in content a.

[0100] The external oil phase was heated to 75°C until completely dissolved. 20 mL of the prepared water-in-oil emulsion was transferred as the dispersed phase and added dropwise to 30 mL of the external oil phase under high-speed shearing conditions (shear rate: 5000 rpm; shearing time: 4 minutes; shearing temperature: 75°C) (dispersed phase to continuous phase volume ratio: 1:1.5). Magnetic stirring was continued for 3 hours (stirring speed: 300 rpm; stirring temperature: 25°C) to obtain the water-in-oil emulsion. Figure 4 As shown in content b.

[0101] At room temperature, 20 mL of the above water-in-water emulsion was dispersed into 30 mL of the external oil phase (dispersed phase to continuous phase volume ratio of 1:1.5) using a membrane emulsification device. The external oil phase was preheated to 75°C. The water-in-water emulsion, as the dispersed phase, was forced through a microporous membrane under nitrogen pressure. The droplets gradually increased in size at the end of the pores, and after reaching a certain size, they peeled off and entered the continuous phase of the flowing external oil phase. The membrane emulsification conditions were: microporous membrane pore size of 15 μm, pore length of 100 mm, emulsification pressure of 900 kPa, and emulsification temperature of 25°C.

[0102] Fluorescence micrographs of water-in-oil emulsions prepared by the above three methods are shown below. Figure 5 Dextran was stained with FITC-Dex dye. Content a: Emulsions prepared by mechanical stirring had a particle size of approximately 50 micrometers; Content b: Emulsions prepared by high-speed mechanical stirring had a particle size of approximately 30 micrometers; Content c: Emulsions prepared by membrane emulsification had a particle size of approximately 35 micrometers. Compared to water-in-oil emulsions prepared by mechanical stirring, water-in-oil emulsions prepared by membrane emulsification exhibit better monodispersity and a more uniform particle size distribution, thus allowing for better control over the emulsion morphology. All three methods of preparing water-in-oil emulsions demonstrated good physical stability; after being left at room temperature for one month, the emulsions still exhibited typical multi-emulsion morphology characteristics, and no stratification occurred.

[0103] Comparative Example 4

[0104] Weigh 10 grams of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 5 grams of hydroxypropyl methylcellulose powder (molecular weight 80,000 Da, viscosity 400 Pa·s, solubility parameter 18.3 (Cal / cm³) in 40 grams of deionized water to prepare a 20% (w / w) dextran aqueous solution A; weigh 5 grams of hydroxypropyl methylcellulose powder (molecular weight 80,000 Da, viscosity 400 Pa·s, solubility parameter 18.3 (Cal / cm³)). 3 ) 0.5 Dissolve 10% hydroxypropyl methylcellulose in 45g of deionized water to prepare a 10% aqueous solution B of hydroxypropyl methylcellulose; weigh 2.5g of beeswax and 0.5g of ethyl cellulose powder and add them to 47.5g of sunflower seed oil, heat at 75℃ until the beeswax is completely dissolved, mix all the ingredients, and prepare the outer oil phase for later use.

[0105] Take 10 mL of dextran aqueous solution A and 40 mL of hydroxypropyl methylcellulose aqueous solution B, mix them thoroughly, and allow them to stand to separate into two phases. The phase with the smaller volume is taken as the dispersed phase, and the phase with the larger volume is taken as the continuous phase. Take them out separately. Add 0.5% (w / w) cellulose nanocrystals (Zeta potential -40 mV) to the continuous phase. Place the continuous phase inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collide through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1.2 m / s, ambient temperature 25℃). Add the dispersed phase to the turbulent zone formed by this impact region. Emulsification is completed under the shearing action of the turbulence, preparing a water-in-water emulsion. The resulting emulsion has a particle size of approximately 22 micrometers and a viscosity of 20 Pa·s. At room temperature, 10 mL of the above water-in-water emulsion was dispersed into 40 mL of the external oil phase using a membrane emulsification device (dispersed phase to continuous phase volume ratio of 1:4). The water-in-water emulsion, as the dispersed phase, was forced through a microporous membrane under nitrogen pressure. The droplets gradually increased in size at the pore ends, eventually peeling off and entering the flowing external oil phase. The membrane emulsification conditions were: microporous membrane pore size of 20 μm, pore length of 100 mm, emulsification pressure of 100 kPa, and emulsification temperature of 25 °C. The results showed that a water-in-oil emulsion failed to form, and the system exhibited significant stratification, such as... Figure 6 As shown in content a. Compared with Comparative Example 4, in the preparation of the water-in-water emulsion, the viscosity of the water-soluble polymer hydroxypropyl methylcellulose used in Example 7 increased from 15 Pa·s to 400 Pa·s, resulting in a significant increase in the viscosity of the water-in-water emulsion prepared in this comparative example (20 Pa·s). This made it difficult for the water-in-water emulsion to detach when passing through the microporous membrane, forming larger droplets, which caused some difficulties in constructing the outer interface of the oil-in-water-in-water layer.

[0106] Example 8

[0107] Weigh 10 grams of polyethylene glycol powder (molecular weight 88,000 Da, solubility parameter 9.38 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder in 40 g of deionized water to prepare a 20% (w / w) polyethylene glycol aqueous solution A; weigh 10 g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 0.5 g of ethyl cellulose powder in 40 g of deionized water to prepare a 20% (w / w) dextran aqueous solution B; weigh 0.5 g of ethyl cellulose powder and add it to 49.5 g of sunflower seed oil to prepare the external oil phase for later use.

[0108] 10 mL of polyethylene glycol aqueous solution A and 30 mL of dextran aqueous solution B were mixed thoroughly and allowed to stand for phase separation. The phase with the smaller volume was taken as the dispersed phase, and the phase with the larger volume was taken as the continuous phase. Both phases were then removed. Chitosan nanocrystals with a mass percentage concentration of 0.6% (Zeta potential -30 mV) were added to the continuous phase. The continuous phase was placed inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collided through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1.2 m / s, ambient temperature 25℃). The dispersed phase was added to the turbulent zone formed by the impact, and emulsification was completed under the shearing action of the turbulence to prepare a water-in-water emulsion. The resulting emulsion had a particle size of approximately 9 micrometers and a viscosity of 3.7 Pa·s.

[0109] At room temperature, 5 mL of the above water-in-water emulsion was dispersed into 45 mL of the external oil phase using a membrane emulsification device (dispersed phase to continuous phase volume ratio of 1:9). The water-in-water emulsion, as the dispersed phase, was forced through a microporous membrane under nitrogen pressure. The droplets gradually increased in size at the pore ends, eventually peeling off and entering the flowing external oil phase. The membrane emulsification conditions were: microporous membrane pore size of 10 μm, pore length of 50 mm, emulsification pressure of 900 kPa, and emulsification temperature of 30 °C. The resulting water-in-oil emulsion had a particle size of approximately 30 μm and exhibited some stratification after one month at room temperature, with an emulsification index of 78%.

[0110] Example 9

[0111] Weigh 10 grams of polyethylene glycol powder (molecular weight 88,000 Da, solubility parameter 9.38 (Cal / cm³)). 3 ) 0.5 Dissolve 10 g of dextran powder in 40 g of deionized water to prepare a 20% (w / w) polyethylene glycol aqueous solution A; weigh 10 g of dextran powder (molecular weight 500,000 Da, solubility parameter 23.1 (Cal / cm³)). 3 ) 0.5 Dissolve 1 gram of ethyl cellulose powder in 40 grams of deionized water to prepare a 20% (w / w) dextran aqueous solution B; weigh 1 gram of ethyl cellulose powder and add it to 49 grams of sunflower seed oil to prepare the external oil phase for later use.

[0112] 10 mL of polyethylene glycol aqueous solution A and 30 mL of dextran aqueous solution B were mixed thoroughly and allowed to stand for phase separation. The phase with the smaller volume was taken as the dispersed phase, and the phase with the larger volume was taken as the continuous phase. Both phases were then removed. Chitosan nanocrystals with a mass percentage concentration of 0.6% (Zeta potential -30 mV) were added to the continuous phase. The continuous phase was placed inside an impinging flow apparatus. Under the action of the flow guiding component, two opposing fluid streams collided through the nozzle of the apparatus (impinging nozzle diameter 0.1 mm, ejection velocity 1.2 m / s, ambient temperature 25℃). The dispersed phase was added to the turbulent zone formed by the impact, and emulsification was completed under the shearing action of the turbulence to prepare a water-in-water emulsion. The resulting emulsion had a particle size of approximately 9 micrometers and a viscosity of 3.7 Pa·s.

[0113] At room temperature, 5 mL of the above water-in-water emulsion was dispersed into 45 mL of the external oil phase using a membrane emulsification device (dispersed phase to continuous phase volume ratio of 1:9). The water-in-water emulsion, as the dispersed phase, was forced through a microporous membrane under nitrogen pressure. The droplets gradually increased in size at the pore ends, eventually peeling off and entering the flowing continuous phase of the external oil phase. The membrane emulsification conditions were: microporous membrane pore size of 10 μm, pore length of 50 mm, emulsification pressure of 900 kPa, and emulsification temperature of 30 °C. The resulting water-in-oil emulsion had a particle size of approximately 15 μm. The higher emulsification pressure promoted the adsorption of ethyl cellulose at the oil-water interface, reducing the droplet size. After one month at room temperature, the above water-in-oil emulsion showed slight stratification, with an emulsification index of 93%. However, compared to Example 8, its stability was significantly improved, possibly because the increased amount of ethyl cellulose increased the viscosity of the continuous phase, hindering droplet movement and preventing emulsion instability.

[0114] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a water-in-oil, water-in-water Pickering emulsion based on a water-in-water emulsion structure, characterized in that, Includes the following steps: (1) After mixing the aqueous solutions of the first polymer system and the second polymer system, the water distribution ratio in the two polymer systems is different, that is, the water in the polymer system with weak water retention will migrate to the polymer system with strong water retention; after standing, phase separation occurs, and two phases with different volumes are obtained, in which the smaller phase is used as the aqueous dispersed phase and the larger phase is used as the aqueous continuous phase. (2) The solid particle stabilizer is dispersed in the aqueous continuous phase, and then the aqueous dispersed phase is mixed with the aqueous continuous phase in which the solid particle stabilizer is dispersed and emulsified to prepare a water-in-water Pickering emulsion. (3) The water-in-water Pickering emulsion is used as the dispersed phase and dispersed in the oil phase by shear emulsification to obtain a water-in-oil Pickering emulsion. In step (1), the first polymer system and the second polymer system each independently contain one or more water-soluble polymers, wherein the water-soluble polymers are selected from water-soluble synthetic macromolecules, water-soluble natural polysaccharides and water-soluble proteins; The absolute value of the difference between the solubility parameter of the water-soluble polymer in the first polymer system and the solubility parameter of the water-soluble polymer in the second polymer system relative to water is greater than 0.5 (Cal / cm). 3 ) 0.5 ; The mass percentage concentration of the polymer in the aqueous solution of the first polymer system is 3% to 20%, and the mass percentage concentration of the polymer in the aqueous solution of the second polymer system is 3% to 20%. The volume ratio of the aqueous solution of the first polymer system to the aqueous solution of the second polymer system is 1:1 to 1:

10. The solid particle stabilizer mentioned in step (2) is a water-insoluble micro / nano particle, which is one or more of inorganic nanoparticles, organic nanoparticles, and inactivated microorganisms; The emulsification in step (2) is impingement flow shear emulsification; The viscosity of the water-in-water Pickering emulsion in step (2) is 1-10 Pa·s; The oil phase in step (3) also contains an emulsifier, which is a small molecule surfactant and / or a solid particulate emulsifier, wherein the HLB value of the small molecule surfactant is 5-8; the emulsifier accounts for 0.1-5 wt% of the mass of the oil phase.

2. The method as described in claim 1, characterized in that, The mass of the solid particulate stabilizer accounts for 0.01% to 1.5% of the total mass of the aqueous continuous phase and the aqueous dispersed phase.

3. The method as described in claim 1, characterized in that, The emulsification temperature in step (2) is 5 ~ 50 ℃; The impinging flow shear emulsification specifically involves: forming two opposing fluid streams by guiding the continuous aqueous phase containing the particulate stabilizer through the impinging flow; adding the aqueous dispersed phase into the turbulent region generated by the two opposing fluid streams in the impact region; and utilizing the shearing effect of the two opposing fluid streams to conduct shear emulsification in the turbulent region to prepare a stable water-in-water Pickering emulsion.

4. The method as described in claim 1, characterized in that, The oil phase mentioned in step (3) includes one or more of herbaceous or woody oilseeds.

5. The method as described in claim 1, characterized in that, The oil phase mentioned in step (3) is one or more of liquid paraffin, rapeseed oil, soybean oil, sunflower oil and tea seed oil.

6. The method as described in claim 1, characterized in that, The small molecule surfactant emulsifier is a fatty acid or phospholipid emulsifier, and the solid particulate emulsifier is one or more of silica nanoparticles, ethyl cellulose nanoparticles, and natural food waxes.

7. The method as described in claim 1, characterized in that, Step (3) The water-in-water Pickering emulsion is dispersed in the oil phase by mechanical stirring or membrane emulsification as the dispersed phase, wherein the oil phase is a continuous phase, to obtain the water-in-oil emulsion; The water-in-water Pickering emulsion has a particle size of 5-45 micrometers; The volume ratio of the water-in-water Pickering emulsion to the oil phase is 1:9 to 1:1.

5.

8. The method as described in claim 7, characterized in that, Step (3) The water-in-water Pickering emulsion is dispersed in the oil phase by mechanical stirring. Specifically, the water-in-water Pickering emulsion is added dropwise to the continuous oil phase as the dispersed phase, and the mechanical stirring speed is 300-5,000 rpm.

9. The method as described in claim 7, characterized in that, Step (3) The water-in-water Pickering emulsion is used as the dispersed phase and dispersed in the oil phase by membrane emulsification. The membrane emulsification conditions are: microporous membrane pore size 1~20 micrometers, pore length 50-200 millimeters, emulsification pressure: 50-900 kPa.

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