Preparation method of long-term stable water-in-water emulsion

Abstract

The invention discloses a preparation method of a long-term stable water-in-water emulsion, and belongs to the technical field of water-in-water emulsions. Through the electrostatic repulsion effect of sodium caseinate and konjac glucomannan on the interface, the effect that the solid beverage can be stably stored for more than 30 days without exogenous particles and stored for 60 days according to the partial concentration ratio is achieved, and the solid beverage is far beyond the level of the prior art. According to the technology, a full-water-based system is adopted, nontoxic and biodegradable food-grade biopolymer materials are used as raw materials, the technology is environmentally friendly, simple and controllable, only conventional mixing is needed, complex molecular modification or a high-energy-consumption technology is not needed, and the technology has wide application prospects in the fields of food, medicine, cosmetics and the like which have strict requirements for purity.

Description

Technical Field

[0001] This invention relates to the field of water-in-water emulsion technology, and more particularly to a method for preparing a long-term stable water-in-water emulsion. Background Technology

[0002] Water-in-water (W / W) emulsions are a special type of emulsion system in which both phases are aqueous solutions, but are immiscible or partially separated. They are typically formed by two immiscible water-soluble polymers under specific conditions. Because they do not contain organic solvents, they hold significant promise for applications in food, cosmetics, pharmaceuticals, and biomaterials. However, water-in-water emulsions are inherently thermodynamically metastable systems, and their stability is primarily limited by factors such as low interfacial tension and weak interfacial film strength. This results in most existing water-in-water emulsions only being able to remain stable for a few hours to a few days, severely restricting their practical applications.

[0003] To improve stability, existing processes in this field mainly introduce particles (such as polymer latex, inorganic particles, cellulose nanocrystals, protein microgels, and bacterial cells) to form a physical barrier at the interface using the Pickering effect, thereby delaying phase separation or droplet coalescence. For example, Reference I (Carbohydrate Polymers, 2025, 348:122937) reports a technique for obtaining fibrous particles (Ovalbumin fibrils, OVAF) by heat treatment to regulate ovalbumin, thereby stabilizing a novel water-in-water emulsion based on a tara gum / branched starch system. The resulting dense interfacial layer allows the emulsion to remain stable for at least 5 days. Reference II (Food Hydrocolloids, 2022, 130:107698) reports a water-in-water emulsion composed of two incompatible water-soluble biopolymers (dextran and maltodextrin) and stabilized with bacterial cellulose (BC) nanofibers, which did not break down within 7 days. Reference III (FoodHydrocolloids, 2023, 141:108719) reported a novel water-in-water emulsion system constructed using hydroxypropylmethyl cellulose (HPMC) and maltodextrin (MD). Cellulose nanocrystals were used as particles, and when the concentration of cellulose nanocrystals was greater than 0.025 wt.%, the resulting water-in-water emulsion showed no phase separation within 30 days. Reference IV (International Journal of Biological Macromolecules, 2024, 262:130036) constructed a water-in-water emulsion system using whey protein isolate (WPI) and xanthan gum (XG), using liposomes as particles. The resulting emulsion remained stable for 12 days. In addition, reference V (The Royal Society of Chemistry, Microrheology and microstructure of water-in-water emulsions containing sodium caseinate and locust bean gum) reported the use of sodium caseinate and locust bean gum as two-phase water-in-water emulsions, but the emulsion in this system began to deform after about one day.

[0004] While the aforementioned methods can extend the stability time of emulsions to some extent, they cannot achieve long-term stability (≥30 days). Furthermore, they introduce problems such as the introduction of exogenous particles, reduced system purity, limited biocompatibility, increased costs, and complex subsequent processing. Specifically, the main drawback of existing processes is that when relying on exogenous solid particles or fibers as stabilizers, the emulsion system is not pure, easily affecting the safety, biocompatibility, or transparency of the final product. Pickering emulsions utilize the irreversible adsorption of solid particles at the oil-water interface, forming a dense physical barrier that prevents droplet aggregation. The Pickering stabilization mechanism has strict requirements on particle surface properties, size, and concentration, resulting in a complex preparation process and poor reproducibility. Moreover, the introduction of particle or fiber stabilizers can easily alter the rheological properties, taste, or active ingredient release behavior of the system, limiting its application in high-end fields.

[0005] In summary, achieving the preparation of water-in-water emulsions using a simple and controllable process, while meeting comprehensive performance requirements such as long-term stability, component purity, biocompatibility, and environmental friendliness, is of great significance for expanding the applications of water-in-water emulsions. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the purpose of this invention is to provide a method for preparing a water-in-water emulsion that does not rely on any exogenous solid particles or fiber stabilizers. Based on specific raw material selection and process design, the method achieves long-term stability of the emulsion and meets the requirements of simple preparation, pure composition, and good biocompatibility.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect of the present invention, a method for preparing a long-term stable water-in-water emulsion is provided, comprising the following steps: (1) Dissolve carboxymethyl konjac glucomannan (CMKGM) in water to obtain an aqueous solution of carboxymethyl konjac glucomannan; dissolve sodium caseinate (CAS) in water to obtain an aqueous solution of sodium caseinate; (2) Mix carboxymethyl konjac glucomannan aqueous solution with sodium caseinate aqueous solution, and control the mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system to be 2 wt.%~3 wt.%:1 wt.%~2 wt.% to obtain a long-term stable water-in-water emulsion.

[0008] Preferably, in step (1), the water includes deionized water or pure water.

[0009] In this invention, the source of carboxymethyl konjac glucomannan is not particularly limited. Those skilled in the art can use existing commercial products or obtain it in self-made form according to actual conditions and needs.

[0010] Preferably, in step (1), the preparation method of the carboxymethyl konjac glucomannan includes the following steps: Konjac glucomannan was dispersed in an aqueous ethanol solution, then an aqueous ethanol solution containing sodium hydroxide was added for alkalization, followed by the addition of bromoacetic acid and the reaction at room temperature. After the reaction was completed, hydrochloric acid was used for neutralization, and the liquid phase was then removed. The resulting solid was purified and dried to obtain carboxymethyl konjac glucomannan.

[0011] This process uses the mass concentration ratio between raw material components in the mixed system as the core limiting condition. Under the above ratio, when the dissolution purpose is met, the concentrations of the carboxymethyl konjac glucomannan aqueous solution and the sodium caseinate aqueous solution are not particularly limited, and those skilled in the art can select them according to actual conditions or needs.

[0012] Preferably, in step (2), the mixing is carried out by stirring or shearing.

[0013] More preferably, the stirring rate is 300~700 rpm and the stirring time is 10~40 min.

[0014] In a second aspect of the present invention, a long-term stable water-in-water emulsion is provided, which is prepared using the preparation method of the first aspect of the present invention.

[0015] Preferably, the long-term stable water-in-water emulsion achieves emulsion system stability based on discrete phase separation.

[0016] In a further preferred embodiment, in the long-term stable water-in-water emulsion, carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase.

[0017] Preferably, the long-term stable water-in-water emulsion does not separate into layers for ≥30 days when stored at room temperature.

[0018] In a third aspect of the invention, the application of the long-term stable water-in-water emulsion of the second aspect of the invention is provided, including: as a raw material for the preparation of food, medicine, and cosmetics.

[0019] The long-term stable water-in-water emulsion of the present invention has wide applicability in the field of emulsions. In practical applications, those skilled in the art can add auxiliary components, such as a small amount of electrolyte (sodium chloride, etc.) to adjust the ionic strength, or add a second polysaccharide to increase the viscosity of the continuous phase, based on the water-in-water emulsion of the present invention without affecting the purity of the system; alternatively, a third phase (such as an oil phase) can be introduced on the basis of the present invention to form a water-in-water-oil (W / W / O) multiple emulsion, thereby expanding the scope of application.

[0020] Based on the above technical solutions, the design concept and principle of this invention are as follows: This invention constructs a water-in-water emulsion using sodium caseinate and konjac glucomannan in a specific ratio as two phases. The core principle lies in the use of carboxymethylation to induce a negative charge in konjac glucomannan molecules, forming carboxymethyl konjac glucomannan. When the pH is higher than the isoelectric point of sodium caseinate, the electrostatic repulsion between carboxymethyl konjac glucomannan and sodium caseinate induces discrete phase separation in their mixture, forming a water-in-water emulsion. When carboxymethyl konjac glucomannan serves as the continuous phase in the water-in-water emulsion, its high viscosity inhibits the movement, flocculation, and aggregation of dispersed phase droplets, thus imparting extremely high stability to the water-in-water emulsion system.

[0021] Furthermore, the carboxymethyl konjac glucomannan and sodium caseinate system used in this invention exhibits good compatibility, with a negative mixing free energy, indicating that the system is in a single-phase stable region without significant liquid-liquid phase separation. After carboxymethylation modification, the konjac glucomannan molecules introduce a high density of carboxyl groups, becoming anionic. This significantly enhances the effective repulsion between the konjac glucomannan and the equally negatively charged sodium caseinate in the bulk phase, leading to an increase in the mixing enthalpy and a shift in the mixing free energy from negative to positive. This triggers the polymer-polymer type liquid-liquid phase separation and the formation of an aqueous two-phase system, which is the target of this invention. Simultaneously, in the heterogeneous region of the aqueous two-phase interface, local interactions between carboxymethyl konjac glucomannan and sodium caseinate cause selective adsorption, thereby reducing interfacial tension and enhancing interfacial viscoelasticity. Ultimately, a water-in-water emulsion with long-term stability is formed without relying on any added particles or surfactants.

[0022] Based on the above mechanism, the present invention achieves the preparation of water-in-water emulsions with long-term stability without relying on any added particles or surfactants.

[0023] It should be noted that existing technologies employ processes using carboxymethyl konjac glucomannan and proteins (Zhang Yiwen, Gu Chunye, Liu Xueling, et al. Ovalbumin-carboxymethyl konjac glucomannan complex-stabilized curcumin Pickering emulsion and its intestinal delivery performance [J]. Food Research and Development, 2024, 45(16):41-48.). Based on the above description, the stabilization mechanism of this invention is not the steric hindrance and mechanical barrier formed by the adsorption of Pickering effect particles at the interface, nor is the final structure a continuous phase containing a large number of discrete droplets encapsulated by particles. The two are substantially different in principle and structure, and should not be considered identical simply because existing technologies use similar raw materials. In summary, the raw material type and proportion parameters of this invention are based on a specific inventive concept and are not conventional technical choices in this field, nor are they the same as existing polysaccharide-protein systems.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention provides a method for preparing a long-term stable water-in-water emulsion. Through the electrostatic repulsion at the interface between sodium caseinate and konjac glucomannan, it achieves stable storage for over 30 days without the need for exogenous particles, and in some concentrations, storage for up to 60 days, far exceeding the level of existing technologies (typically <14 days). The process of this invention uses a fully water-based system, and its raw materials are non-toxic, biodegradable, food-grade biopolymers. It is environmentally friendly, simple, and controllable, requiring only conventional mixing without complex molecular modifications or high-energy-consuming processes. It has broad application prospects in fields with strict purity requirements, such as food, pharmaceuticals, and cosmetics. Attached Figure Description

[0025] Figure 1 The Fourier transform infrared spectroscopy (FTIR) of carboxymethyl konjac glucomannan used in the embodiments of the present invention is shown below. Figure 2 The appearance and microstructure changes of the long-term stable water-in-water emulsion prepared for the example during storage; the scale bar in the lower left corner of each sub-graph is 30 μm. Figure 3 The results show the microstructure characterization of different types of water-in-water emulsions; Figure 4 The results show the appearance of the emulsion after standing for 10 days; where a is the test result of Comparative Example 1 and b is the test result of Comparative Example 2. Figure 5 The results are shown in the microscopic observation of Comparative Example 4; Figure 6 The results of microscopic observation are for Comparative Example 5; Figure 7 The results of microscopic observation are for Comparative Example 6; Figure 8 The results are shown in the microscopic observation of Comparative Example 7; Figure 9 The results are shown in the microscopic observation of Comparative Example 8. Detailed Implementation

[0026] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0027] In the following embodiments: Carboxymethyl konjac glucomannan was prepared in the laboratory, and its preparation steps are as follows: A certain amount (10 g) of konjac glucomannan was dispersed in 2 volumes of 70% (v / v, the same below) ethanol aqueous solution and stirred for 30 min. Then, 5 volumes of 70% ethanol aqueous solution containing 1.25~2.5 mol / L sodium hydroxide were added for alkalization for 30 min. Bromoacetic acid was then added to make the concentration of bromoacetic acid in the whole system 0.25~0.5 mol / L (0.5 mol / L). The reaction was carried out at room temperature for 0~28 h (24 h). After the reaction was completed, the system was neutralized with hydrochloric acid (1 mol / L) to make the pH of the system 7. The liquid phase was removed by filtration. The solid was washed with 70%, 80%, and 95% ethanol aqueous solution in a gradient to remove residual ions. Finally, the solid was dried at 80 ℃ for 2 h to obtain carboxymethyl konjac glucomannan.

[0028] The prepared carboxymethyl konjac glucomannan was characterized by Fourier transform infrared spectroscopy, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that at 1590 cm -1 and 1410 cm -1 Two new spectral bands were clearly observed, corresponding to the asymmetric and symmetric stretching vibrations of the carboxyl group. These results confirm that carboxymethyl groups were successfully introduced into konjac glucomannan, and the target carboxymethyl konjac glucomannan was obtained.

[0029] Example 1 This embodiment provides a long-term stable water-in-water emulsion, prepared using the following method: (1) Weigh 1 g of carboxymethyl konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain carboxymethyl konjac glucomannan aqueous solution; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain sodium caseinate aqueous solution. (2) The aqueous solution of carboxymethyl konjac glucomannan and the aqueous solution of sodium caseinate were magnetically stirred for 30 min. The mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system was controlled to be 2 wt.%:1.5 wt.% to obtain a water-in-water emulsion with long-term stability, wherein carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase emulsion.

[0030] Example 2 This embodiment provides a long-term stable water-in-water emulsion, prepared using the following method: (1) Weigh 1 g of carboxymethyl konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain carboxymethyl konjac glucomannan aqueous solution; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain sodium caseinate aqueous solution. (2) The aqueous solution of carboxymethyl konjac glucomannan and the aqueous solution of sodium caseinate were magnetically stirred for 30 min. The mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system was controlled to be 2 wt.%:2 wt.% to obtain a water-in-water emulsion with long-term stability, wherein carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase emulsion.

[0031] Example 3 This embodiment provides a long-term stable water-in-water emulsion, prepared using the following method: (1) Weigh 1 g of carboxymethyl konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain carboxymethyl konjac glucomannan aqueous solution; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain sodium caseinate aqueous solution. (2) The aqueous solution of carboxymethyl konjac glucomannan and the aqueous solution of sodium caseinate were magnetically stirred for 30 min. The mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system was controlled to be 3 wt.%:1.5 wt.% to obtain a water-in-water emulsion with long-term stability, wherein carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase emulsion.

[0032] Example 4 This embodiment provides a long-term stable water-in-water emulsion, prepared using the following method: (1) Weigh 1 g of carboxymethyl konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain carboxymethyl konjac glucomannan aqueous solution; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain sodium caseinate aqueous solution. (2) The aqueous solution of carboxymethyl konjac glucomannan and the aqueous solution of sodium caseinate were magnetically stirred for 30 min. The mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system was controlled to be 3 wt.%: 2 wt.% to obtain a water-in-water emulsion with long-term stability, wherein carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase emulsion.

[0033] Comparative Example 1 This comparative example uses uncarboxymethylated konjac glucomannan and sodium caseinate as raw materials to prepare an emulsion using the following preparation method: (1) Weigh 1 g of konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain an aqueous solution of konjac glucomannan; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain an aqueous solution of sodium caseinate. (2) The konjac glucomannan aqueous solution and the sodium caseinate aqueous solution were magnetically stirred for 30 min. The mass concentration ratio of konjac glucomannan to sodium caseinate in the mixed system was controlled to be 0.5 wt.%:2 wt.% and 0.5 wt.%:3 wt.%, respectively, to obtain two emulsions.

[0034] Comparative Example 2 This comparative example uses carboxymethyl konjac glucomannan and sodium caseinate as raw materials to prepare an emulsion using the following preparation method: (1) Weigh 1 g of carboxymethyl konjac glucomannan, add it to 99 mL of deionized water, stir to dissolve it, and obtain carboxymethyl konjac glucomannan aqueous solution; weigh 10 g of sodium caseinate, add it to 90 mL of deionized water, stir to dissolve it, and obtain sodium caseinate aqueous solution. (2) The aqueous solution of carboxymethyl konjac glucomannan and the aqueous solution of sodium caseinate were magnetically stirred for 30 min. The mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system was controlled to be 0.5 wt.%:2wt.% and 0.5 wt.%:3 wt.%, respectively, to obtain two emulsions.

[0035] Comparative Example 3 Based on Example 1, this comparative example changed the mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system to 1 wt.%:3 wt.%, 1 wt.%:6 wt.%, and 1 wt.%:10 wt.%, respectively, and three emulsions were prepared accordingly.

[0036] Comparative Example 4 This comparative example uses other optional raw materials available in the art to prepare the emulsion, in addition to the specific design of this invention. The preparation method of this comparative example is basically the same as that of Example 1, except that the raw materials used are sodium caseinate and inulin, and the ratio of sodium caseinate to inulin is 2.5 wt.%: 5 wt.%.

[0037] Comparative Example 5 This comparative example uses other optional raw materials available in the art to prepare the emulsion, in addition to the specific design of this invention. The preparation method of this comparative example is basically the same as that of Example 1, except that the raw materials used are gelatin and fructooligosaccharides, and the ratio of gelatin to fructooligosaccharides is 2 wt.%:14 wt.%.

[0038] Comparative Example 6 This comparative example uses other optional raw materials available in the art to prepare the emulsion, in addition to the specific design of this invention. The preparation method of this comparative example is basically the same as that of Example 1, except that the raw materials used are inulin and soy protein isolate, with an inulin to soy protein isolate ratio of 6 wt.%:4 wt.%.

[0039] Comparative Example 7 This comparative example uses other optional raw materials available in the art to prepare the emulsion, in addition to the specific design of this invention. The preparation method of this comparative example is basically the same as that of Example 1, except that the raw materials used are carboxymethyl konjac glucomannan and gelatin, and the ratio of carboxymethyl konjac glucomannan to gelatin is 6 wt.%:0.5 wt.%.

[0040] Comparative Example 8 This comparative example uses other optional raw materials available in the art to prepare the emulsion, in addition to the specific design of this invention. The preparation method of this comparative example is basically the same as that of Example 1, except that the raw materials used are carboxymethyl konjac glucomannan and gelatin, and the ratio of carboxymethyl konjac glucomannan to gelatin is 6 wt.%:1 wt.%.

[0041] Test Example 1 In this test case, the long-term stable water-in-water emulsions with different proportions designed in the examples were placed at room temperature for 60 days. During this period, the appearance and microstructure of the emulsions were observed, and the results are as follows: Figure 2 As shown.

[0042] Figure 2The test results showed that the droplets of the emulsion tended to decrease in size with prolonged storage time. Within 30 days, no macroscopic phase separation was observed in any concentration of the emulsion. Microscopically, the emulsion droplets maintained their integrity and spherical shape, without any observed droplet fusion, formation of large aggregates, or network structures. Furthermore, at the optimal mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate (e.g., CMKGM:CAS = 3 wt.%: 1.5 wt.%), the emulsion could be stored for up to 60 days, significantly superior to existing technologies (typically <14 days).

[0043] Test Example 2 To investigate the effect of varying carboxymethyl konjac glucomannan to sodium caseinate concentration ratio on the emulsion, this test example used three emulsions from Comparative Example 3 as the research object. Sodium caseinate was stained with fluorescein isothiocyanate (FITC), and the different types of emulsions were observed using an inverted fluorescence microscope. The results are as follows: Figure 3 As shown.

[0044] Depend on Figure 3 It can be observed that the emulsion type changes with increasing sodium caseinate concentration, from sodium caseinate encapsulated by carboxymethyl konjac glucomannan, to a bicontinuous phase, and then to sodium caseinate encapsulated by carboxymethyl konjac glucomannan. These changes indicate that to achieve the desired structure, the proportions need to be controlled within the design range of this invention. Emulsion structures outside the design range differ significantly from those of this invention.

[0045] Test Example 3 This test example is used to study the effect of carboxymethylation treatment, and the stability of the emulsion system formed when the mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate is not the specific ratio of this invention.

[0046] Using the emulsions prepared in Comparative Examples 1 and 2 as the research objects, their appearance changes were observed after standing at room temperature for 10 days. The results are as follows: Figure 4 As shown. It should be noted that neither Comparative Example 1 nor Comparative Example 2 achieved the goal of long-term stability of the present invention. The 10-day period was chosen because it was intended to demonstrate the differences between Comparative Example 1 and Comparative Example 2. Extending the time period resulted in stratification in both. Figure 4 a represents the results of the emulsion in Comparative Example 1 after standing, with proportions from left to right corresponding to 0.5 wt.%: 2 wt.% and 0.5 wt.%: 3 wt.% respectively; Figure 4b shows the results of the emulsion in Comparative Example 2 after standing, corresponding to the ratios of 0.5 wt.%: 2 wt.% and 0.5 wt.%: 3 wt.% from left to right. In Comparative Example 1, the uncarboxymethylated konjac glucomannan did not show any stratification, while the carboxymethylated konjac glucomannan in Comparative Example 2 did separate from sodium caseinate.

[0047] The above results indicate that carboxymethylation of konjac glucomannan, without the specific raw material ratios of this invention, not only fails to improve stability but may even make the system more unstable. This phenomenon suggests that carboxymethylation itself does not necessarily bring positive effects; its effect is highly dependent on the synergistic effect of the system designed in this invention. Comparative Example 1 exhibited better stability than Comparative Example 2 at non-designed ratios, further revealing the complexity of the water-in-water emulsion system of this invention. Incorrect selection of raw material ratios may amplify the negative impacts of modification, but cannot infer that carboxymethylation is ineffective or unnecessary. Therefore, the judgment criterion should be based on whether the modified system is superior to the unmodified system at the specific ratios of this invention. Combining the test results of the embodiments in Test Example 1 of this invention, it can be seen that the stability effect of the embodiments is significantly better than that of the comparative examples, indicating that the design of this invention brings technical effects beyond expectations.

[0048] Test Example 4 This test example is based on microscopic observation of emulsions prepared using other optional raw materials and proportions available in the art for Comparative Examples 4-8. The results are as follows: Figures 5-9 As shown.

[0049] Depend on Figures 5-7 As can be seen from the images, the reason why the stable water-in-water emulsions of the present invention, which were not formed in Comparative Examples 4-6, may be that inulin and fructooligosaccharides have low molecular weights and are highly hydrated. Their mixing entropy with gelatin, sodium caseinate, and soy protein isolate is dominant, and the mixing free energy of the system is always negative, making it difficult to enter the liquid-liquid phase separation region. At the same time, these low molecular weight neutral polysaccharide molecules are highly hydrophilic and contain almost no hydrophobic structures, lacking effective interfacial adsorption capacity. They cannot form a stable structural layer at the aqueous two-phase interface, thus making it difficult to construct a stable water-in-water emulsion system.

[0050] according to Figure 8 , 9 The images show that gelatin and carboxymethyl konjac glucomannan have too strong a compatibility, making it difficult to establish sufficient bulk repulsion. Soy protein isolate is mainly composed of globular proteins, and its unfolding ability is weaker than that of sodium caseinate with random conformation. In aqueous two-phase systems, aggregation / flocculation or insolubility are more likely to occur rather than ideal liquid-liquid separation. Neither can simultaneously meet the two necessary conditions for the formation of water-in-water emulsions: phase separation and interfacial stability.

[0051] In summary, this invention achieves stable storage for over 30 days without the need for exogenous particles, and even up to 60 days for some concentrations, through the electrostatic repulsion effect of sodium caseinate and konjac glucomannan at the interface. This far surpasses the level of existing technologies (typically <14 days). The process of this invention uses a fully water-based system, and its raw materials are non-toxic, biodegradable, food-grade biopolymers. It is environmentally friendly, simple, and controllable, requiring only conventional mixing without complex molecular modifications or high-energy-consuming processes. It has broad application prospects in fields with strict purity requirements, such as food, pharmaceuticals, and cosmetics.

[0052] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a long-term stable water-in-water emulsion, characterized in that, Includes the following steps: (1) Dissolve carboxymethyl konjac glucomannan in water to obtain an aqueous solution of carboxymethyl konjac glucomannan; dissolve sodium caseinate in water to obtain an aqueous solution of sodium caseinate; (2) Mix carboxymethyl konjac glucomannan aqueous solution with sodium caseinate aqueous solution, and control the mass concentration ratio of carboxymethyl konjac glucomannan to sodium caseinate in the mixed system to be 2 wt.%~3 wt.%:1 wt.%~2 wt.% to obtain a long-term stable water-in-water emulsion.

2. The method for preparing a long-term stable water-in-water emulsion according to claim 1, characterized in that: In step (1), the water includes deionized water or pure water.

3. The method for preparing a long-term stable water-in-water emulsion according to claim 1, characterized in that, In step (1), the preparation method of the carboxymethyl konjac glucomannan includes the following steps: Konjac glucomannan was dispersed in an aqueous ethanol solution, then an aqueous ethanol solution containing sodium hydroxide was added for alkalization, followed by the addition of bromoacetic acid and the reaction at room temperature. After the reaction was completed, hydrochloric acid was used for neutralization, and the liquid phase was then removed. The resulting solid was purified and dried to obtain carboxymethyl konjac glucomannan.

4. The method for preparing a long-term stable water-in-water emulsion according to claim 1, characterized in that: In step (2), the mixing is carried out by stirring or shearing.

5. The method for preparing a long-term stable water-in-water emulsion according to claim 4, characterized in that: The stirring rate is 300~700 rpm, and the stirring time is 10~40 min.

6. A long-term stable water-in-water emulsion, characterized in that: It is prepared by any one of the preparation methods described in claims 1 to 5.

7. The long-term stable water-in-water emulsion according to claim 6, characterized in that: The long-term stable water-in-water emulsion achieves emulsion system stability based on discrete phase separation.

8. The long-term stable water-in-water emulsion according to claim 7, characterized in that: In the long-term stable water-in-water emulsion, carboxymethyl konjac glucomannan is the continuous phase and sodium caseinate is the dispersed phase.

9. The long-term stable water-in-water emulsion according to claim 6, characterized in that: The long-term stable water-in-water emulsion did not separate into layers for ≥30 days when stored at room temperature.

10. The application of a long-term stable water-in-water emulsion as described in any one of claims 6 to 9, characterized in that: It is used as a raw material in the preparation of food, medicine, and cosmetics.

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