A polysaccharide-stabilized high internal phase emulsion and its preparation method and application

Abstract

The present invention relates to a polysaccharide-stabilized high internal phase emulsion, a preparation method thereof and an application. The preparation method includes: dispersing any one of sodium carboxymethyl cellulose, sodium alginate and pectin in water or an aqueous solution, and after standing, formulating a solution with a mass percentage concentration of 0.05% to 3% and a pH < 5.2 as the water phase; subjecting the water phase and the oil phase prepared in S1 to shear mixing to obtain a high internal phase emulsion with an oil phase volume fraction of 74% to 88%. The present invention only needs to use polysaccharides (or polysaccharide derivatives) alone, without other surfactants or coagulants, and can efficiently prepare high internal phase emulsions through one-step shear dispersion, providing ideas for developing emulsifying stabilizers for novel high internal phase emulsions. The prepared oil-in-water high internal phase emulsion is green, safe, highly stable, has good gel properties and strong plasticity, has good thermal stability and temperature responsiveness, and has good application prospects in the fields of food, medicine, chemical engineering and biological engineering materials, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of emulsion preparation, and particularly relates to a high internal phase emulsion stabilized by polysaccharide substances, a preparation method thereof and an application thereof. Background Art

[0002] As a colloidal system with a high internal phase volume (internal phase volume fraction ≥ 74%) that can combine the dual characteristics of emulsion and gel, high internal phase emulsion has increasingly become a research frontier hotspot due to its excellent stability and outstanding functional properties. The formation and stabilization of high internal phase emulsion require the use of suitable emulsifying stabilizers. However, a large amount of surfactants or inorganic particles are usually used to stabilize high internal phase emulsion, and these components may have adverse effects on human health or the ecological environment, and cannot meet the demand for "clean label".

[0003] At present, it has been found that a small number of polysaccharides such as cellulose nanocrystals, carboxymethyl chitosan, and chitosan hydrochloride have excellent properties of stabilizing high internal phase emulsion alone. These polysaccharide-based high internal phase emulsions are more green, safe, environmentally friendly, cheap, easily available, simple and economical, and exhibit a series of outstanding functional properties such as high storage stability, thermal stability, temperature responsiveness, and plasticity. However, the exploration of polysaccharide-based emulsifying stabilizers is still relatively less at present. There is no literature report on whether other polysaccharides that are more diverse, cheap, easily available, and widely used in the food industry can be used alone to prepare high internal phase emulsion, and the performance of the emulsion prepared with them as stabilizers is also completely unknown. Therefore, it is of great significance to seek simple, green and low-cost polysaccharide-based emulsifiers for preparing high internal phase emulsion.

[0004] Sodium carboxymethyl cellulose typically performs thickening, film-forming, adhesive, moisture-retaining, colloid-protecting, emulsifying, and suspending functions, and is widely used in the petroleum, food, pharmaceutical, textile, and paper industries. Sodium alginate is a natural polysaccharide with safety, solubility, viscosity, thickening, gelling, and stability, and has been widely used in the food, textile, and pharmaceutical industries. Pectin exhibits excellent gelling and emulsifying properties and is widely used in the food, pharmaceutical, daily chemical, and textile industries. In short, sodium carboxymethyl cellulose, sodium alginate, and pectin are all common, green, and safe high-molecular-weight, chain-like polysaccharides. They are widely distributed in nature, highly abundant, inexpensive, readily available, and multifunctional. Their excellent solubility, emulsifying, and thickening properties make them widely used as raw materials or food additives in the food industry, particularly in common processed foods such as jams, jellies, cakes, and ice cream. However, research on the three polysaccharides mentioned above in emulsions has largely focused on traditional emulsions, specifically low internal phase emulsions, and their stabilization mechanisms have been largely attributed to pickering particles, primarily prepared by complexing with protein-based substances. Currently, there is no research on the ability of these three polysaccharides to independently stabilize high internal phase emulsions. The ability of these polysaccharides to independently stabilize high internal phase emulsions, as well as their corresponding emulsification and stabilization mechanisms, remain unclear. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and, for the first time, to study the feasibility of preparing a high internal phase emulsion using sodium carboxymethyl cellulose, sodium alginate, and pectin polysaccharides from different commercial sources as stabilizers, and to optimize the process parameters during the preparation process. At the same time, a high internal phase emulsion stabilized by polysaccharides is further developed, so that the high internal phase emulsion stabilized by polysaccharides has safety, gelation, and stability, thereby broadening its application field.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a method for preparing a polysaccharide-stabilized high internal phase emulsion, comprising the following steps:

[0008] S1: dispersing any one of sodium carboxymethyl cellulose, sodium alginate and pectin in water or an aqueous solution, and preparing a solution with a mass concentration of 0.05% to 3% and a pH of less than 5.2 as the aqueous phase after standing;

[0009] S2: The water phase and oil phase prepared in S1 are shear-mixed to obtain a high internal phase emulsion containing an oil phase volume fraction of 74% to 88%.

[0010] Further, in step S1, the mass percentage concentration of the sodium carboxymethyl cellulose solution is 0.05 - 3.0 wt%, and the pH is 0.5 - 5.2.

[0011] Further, the mass percentage concentration of the carboxymethyl cellulose solution is 1.0 wt%, and the pH is 2.0, 3.0 or 4.5.

[0012] Further, in step S1, the mass percentage concentration of the sodium alginate solution is 0.05 - 3.0 wt%, and the pH is 0.5 - 4.0.

[0013] Further, the mass percentage concentration of the sodium alginate solution is 1.0 wt%, and the pH is 2.3, 3.8.

[0014] Further, in step S1, the mass percentage concentration of the pectin solution is 0.05 - 3.0 wt%, and the pH is 0.5 - 4.2.

[0015] Further, the mass percentage concentration of the pectin solution is 1.0 wt%, and the pH is 1.3, 2.4 or 3.6.

[0016] It can be understood that the volume fraction of the oil phase contained in the high internal phase emulsion corresponds to the volume ratio of the water phase to the oil phase. For example, when the volume fraction of the oil phase is 87.5%, the volume ratio of the water phase to the oil phase is 1:7; when the volume fraction of the oil phase is 80%, the volume ratio of the water phase to the oil phase is 1:4; when the volume fraction of the oil phase is 75%, the volume ratio of the water phase to the oil phase is 1:3. For example, when the mass percentage concentration of the sodium carboxymethyl cellulose solution is 0.05 - 3.0 wt%, the addition amount of sodium carboxymethyl cellulose in the high internal phase emulsion containing 80% volume fraction of the oil phase is 0.01 - 0.6 wt% of the total system.

[0017] In the present invention, the mass percentage concentration refers to the concentration expressed as the percentage of the mass of the solute in the total mass of the solution, and the mass percentage concentration = (mass of solute / mass of solution) × 100%. Throughout the text, the unit "wt%" also represents the mass percentage concentration.

[0018] Further, in step S1, the aqueous solution is a sodium citrate buffer solution. When preparing the aqueous solutions of sodium carboxymethyl cellulose, sodium alginate, and pectin separately, either pure water or a common buffer solution in the acidic range can be used. For example, the acidic buffer solution can be a 5 mM citrate buffer solution with a pH of 3.0.

[0019] Further, when the water phase is an aqueous solution of sodium carboxymethyl cellulose, the pH range of the water phase is 0.5 - 5.2.

[0020] Further, when the water phase is an aqueous solution of sodium alginate, the pH range of the water phase is 0.5 - 4.0.

[0021] Further, when the aqueous phase is a pectin aqueous solution, the pH range of the aqueous phase is 0.5 to 4.2.

[0022] Further, when the aqueous phase is a sodium carboxymethyl cellulose aqueous solution, the CMC concentration can be as low as 0.05 wt%, and a milky white high internal phase emulsion with high stability, good gelation and plasticity can be efficiently and simply prepared through one-step shear dispersion.

[0023] Further, when the pectin source is high-ester pectin, the color of the aqueous solution is slightly turbid white, and the optimal pH for forming a high internal phase emulsion is 1.0 to 4.2.

[0024] Further, when the pectin source is low-ester apple pectin, the color of the aqueous solution is slightly turbid white, and the optimal pH for forming a high internal phase emulsion is 1.0 to 4.0.

[0025] Further, when the pectin source is low-ester citrus pectin, the color of the aqueous solution is slightly turbid yellow, and the optimal pH for forming a high internal phase emulsion is 0.5 to 3.0.

[0026] Further, the droplet diameters of the high internal phase emulsions formed by the aqueous solutions in different aqueous phases are all between 5 and 20 μm within the corresponding pH ranges.

[0027] Further, step S1 further includes adding a small amount of inorganic salt or acid-base regulator to the aqueous phase.

[0028] Further, the acid-base regulator is a commercially available hydrochloric acid or sodium hydroxide solution with an appropriate concentration, which is used to adjust the pH of the aqueous phase. It can be understood that a small amount of other inorganic salt ions or biomolecules such as proteins can also be introduced into the system of the present invention, and the above-mentioned inorganic salts, inorganic salt ions or proteins do not affect the function of sodium carboxymethyl cellulose, sodium alginate, and pectin in stabilizing the high internal phase emulsion.

[0029] Further, the dispersion time in step S1 is not less than 1 h, and the standing time is not less than 12 h.

[0030] Further, the dispersion time is not less than 2 h, and the standing time is not less than 18 h. The above setting of the dispersion time is to allow sodium carboxymethyl cellulose, sodium alginate, and pectin to be separately and fully dispersed in water or aqueous solution, and the setting of the standing time is to allow the polysaccharide substances to be fully hydrated.

[0031] Further, the dispersion temperature in step S1 is room temperature. Specifically, the standing temperature in step S1 is 4°C to 36°C. In some embodiments of the present invention, generally, the dispersion and standing operations can be carried out in a room temperature environment, and there is no need to ensure constant temperature and humidity storage conditions, and the operation is convenient and simple.

[0032] Further, the temperature of the standing in step S1 is refrigeration or room temperature.

[0033] Further, the oil phase in step S2 includes at least one of vegetable oil, cyclohexane, n-hexane, and n-dodecane.

[0034] Further, the vegetable oil includes at least one of soybean oil, peanut oil, linseed oil, blended oil, castor oil, and rapeseed oil.

[0035] Further, the vegetable oil is soybean oil.

[0036] Further, the conditions of the shear mixing in step S2 are shearing for 20 s to 90 s at 6000 rpm to 9000 rpm. Through the above shear mixing conditions, a high internal phase emulsion that is separately and stably prepared from sodium carboxymethylcellulose, sodium alginate, and pectin can be rapidly prepared in one step, and a high internal phase emulsion product with excellent performance can be obtained.

[0037] Further, step S2 further includes standing and separating layers after the shear mixing to remove the lower aqueous phase. In the present invention, when the volume fraction of the oil phase used during the preparation is lower than 74%, the excess water will be layered in the lower layer, and the emulsion obtained after removing the lower aqueous phase is still a high internal phase emulsion with an oil phase volume fraction of more than 74%.

[0038] Further, after the shear mixing, it is left standing at 4°C to 36°C, and the standing time is 2 h or more.

[0039] Further, after the shear mixing, it is left standing and separating layers at 4°C to 36°C, and the standing time is 2 h or more.

[0040] Further, the standing time is 12 h or more.

[0041] Further, the standing time is 2 d or more.

[0042] In certain embodiments of the present invention, when the standing time is greater than 2 d, the gel properties of the high internal phase emulsions separately and stably prepared from sodium carboxymethylcellulose and sodium alginate become more and more obvious. When standing for five months, there is still no oil leakage or demulsification phenomenon, and the gel properties are maintained well. However, due to the poor antibacterial property of pectin itself, the storage stability of the high internal phase emulsion prepared from pectin is relatively poor, and mildew and deterioration will occur after two weeks of storage.

[0043] In a second aspect, the present invention provides a high internal phase emulsion stabilized by a polysaccharide substance prepared by the above preparation method.

[0044] In a third aspect, the present invention provides the applications of the separately stable high internal phase emulsions of sodium carboxymethylcellulose, sodium alginate, and pectin prepared by any of the preparation methods described in the first aspect of the present invention. The specific applications are for the preparation of related products, including but not limited to: foods, pharmaceuticals, chemical and bioengineering materials, etc.

[0045] In a fourth aspect, the present invention provides a product made of the separately stable high internal phase emulsions of sodium carboxymethylcellulose, sodium alginate, and pectin prepared by any of the preparation methods described in the first aspect of the present invention. The above products include but not limited to: foods, pharmaceuticals, chemical and bioengineering materials, etc.

[0046] In a fifth aspect, the present invention provides the applications of sodium carboxymethylcellulose, sodium alginate, and pectin separately in the preparation of high internal phase emulsions or their products.

[0047] Further, the method for preparing the high internal phase emulsion is any of the preparation methods described in the first aspect of the present invention.

[0048] Further, in the above applications, the separately stable high internal phase emulsions of sodium carboxymethylcellulose, sodium alginate, and pectin are still very stable after being treated at 100 °C for 30 min.

[0049] Further, in the above applications, the separately stable high internal phase emulsions of sodium carboxymethylcellulose, sodium alginate, and pectin can be re-emulsified after freeze-thaw demulsification.

[0050] Further, in the above applications, the operation steps of freeze-thaw are: the high internal phase emulsion is placed in a -20 °C refrigerator and frozen for 24 h or longer (such as 3 months), and then transferred to a 25 °C constant temperature and humidity box and left standing for 4 h to achieve melting.

[0051] Further, in the above applications, the operation steps of re-emulsification are: the oil-water mixed system demulsified after freeze-thaw treatment is sheared and homogenized at 9000 rpm for 40 s.

[0052] Further, in the above applications, sodium carboxymethylcellulose, sodium alginate, and pectin are separately dispersed in water or an aqueous solution and formulated into a mass percentage concentration of 0.05 - 3.0 wt% after standing.

[0053] Further, in the above applications, the high internal phase emulsion can be used to prepare related products, including but not limited to: foods, pharmaceuticals, chemical and bioengineering materials, etc.

[0054] Further, in the above applications, the high internal phase emulsion can be used for temperature-responsive encapsulation, preservation, transportation, re-acquisition, etc. of active substances that are easily oxidized and degraded or perishable, toxic and harmful, flammable, explosive, or volatile organic liquids.

[0055] Compared with the prior art, the present invention adopting the above technical solutions has at least the following beneficial effects:

[0056] (1) For the first time, the present invention separately uses sodium carboxymethylcellulose or sodium alginate or pectin polysaccharide substances as emulsifying stabilizers to prepare high internal phase emulsions under acidic conditions, without adding other surfactants or inorganic particles. The above polysaccharide substances are green, environmentally friendly, non-toxic, biodegradable, and have high safety. Among them, sodium carboxymethylcellulose and sodium alginate also have certain antioxidant and antibacterial properties, which can effectively delay the oxidation of edible oil in the emulsion gel, facilitate the further processing and preservation of the system, and endow the emulsion gel with new functional activities.

[0057] (2) The preparation method of the present invention can efficiently and simply prepare high internal phase emulsions through one-step shearing and dispersion by a high-speed disperser. The equipment is simple, the cost is low, the energy consumption is low, the preparation process is simple and easy to operate, and the effect is good. At the same time, there is no need to adopt or combine other high-energy preparation means, such as high-pressure homogenization, ultrasonic treatment, secondary emulsification, concentration and other measures.

[0058] (3) The high internal phase emulsion prepared by the present invention is milky white and has strong gelation and good plasticity under suitable acidic pH conditions. In subsequent studies, based on the structural characteristics of the prepared high internal phase emulsion, it can be applied to different fields or aspects respectively. It can be used to prepare oil gels or as a template for functional materials, etc. Moreover, due to its strong gelation, it can be used for 3D or 4D printing of foods, loading drugs and assisting in the preparation of vaccines. Therefore, the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate or pectin polysaccharide substances has good application potential and development value, and can be applied to the development of various products in different fields.

[0059] (4) The high internal phase emulsion prepared by the present invention has high safety, strong stability, good gelation, strong plasticity, high thermal stability, and can be emulsified again after freeze-thaw demulsification. It has good temperature responsiveness and can realize temperature-responsive encapsulation, preservation, transportation, and re-acquisition of active substances that are easily oxidized and degraded or perishable, toxic and harmful, flammable, explosive or volatile organic liquids. This makes it have great development and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is the appearance diagram of the high internal phase emulsions prepared with dodecane as the oil phase and different concentrations of sodium carboxymethylcellulose and sodium alginate in an embodiment of the present invention; among them, in the figure, from left to right, the concentrations of sodium carboxymethylcellulose or sodium alginate are 2.5 wt.%, 1 wt.%, 0.5 wt.%, 0.25 wt.%, 0.1 wt.% respectively;

[0061] Figure 2Appearance (A, B, C) and plasticity demonstration (D, E) of self - supporting gel - like high - internal - phase emulsions stabilized with 1 wt% sodium carboxymethylcellulose or sodium alginate with n - dodecane as the oil phase in one embodiment of the present invention; among them, Figure F shows the results of rheological property measurements of high - internal - phase emulsions prepared separately with different concentrations of sodium carboxymethylcellulose or sodium alginate: the effect of shear frequency on the elastic modulus (G′, solid markers) and viscous modulus (G″, hollow markers) of high - internal - phase emulsions stabilized separately with different concentrations of sodium carboxymethylcellulose or sodium alginate.

[0062] Figure 3 Appearance diagrams of high - internal - phase emulsions prepared with pectin from different commercial sources and different concentrations with n - dodecane as the oil phase in one embodiment of the present invention; among them, for the samples in the figure from left to right, the concentrations of high - ester pectin, low - ester apple pectin, and low - ester citrus pectin are 2.5 wt.%, 1 wt.%, 0.5 wt.%, 0.25 wt.%, and 0.1 wt.% respectively.

[0063] Figure 4 Appearance diagrams of high - internal - phase emulsions prepared with sodium carboxymethylcellulose under different pH conditions in one embodiment of the present invention; among them, for the samples in the upper - layer pictures from left to right, the pH values are 0.5, 2.0, 3.6, 5.2, 6.2, 9.0, and 11.2 respectively; the lower - layer pictures are the corresponding optical microscope images and laser confocal microscope images of the high - internal - phase emulsion prepared at pH 3.6, where the scale bars in the figures are 50 μm and 10 μm respectively.

[0064] Figure 5 Appearance diagrams of high - internal - phase emulsions prepared with sodium alginate under different pH conditions in one embodiment of the present invention; among them, for the samples in the upper - layer pictures from left to right, the pH values are 0.5, 1.8, 3.0, 4.0, 5.0, 7.3, and 10.7 respectively; the lower - layer pictures are the corresponding optical microscope images and laser confocal microscope images of the high - internal - phase emulsion prepared at pH 3.0, where the scale bars in the figures are 50 μm and 15 μm respectively.

[0065] Figure 6 Appearance diagrams of high - internal - phase emulsions prepared with pectin under different pH conditions in one embodiment of the present invention; among them, for the samples in the upper - layer pictures from left to right, the pH values are 1.0, 2.0, 3.0, 4.2, 5.5, 8.5, and 10.9 respectively; the lower - layer pictures are the corresponding optical microscope images and laser confocal microscope images of the high - internal - phase emulsion prepared at pH 2.0, where the scale bars in the figures are 50 μm and 10 μm respectively.

[0066] Figure 7Appearance diagrams of high internal phase emulsion gels prepared separately from sodium carboxymethylcellulose, sodium alginate, and pectin with a mass concentration of 1.0 wt% in an embodiment of the present invention after heat treatment (A, sodium carboxymethylcellulose; B, sodium alginate; C, pectin). Detailed implementation manners

[0067] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0068] In the following embodiments, the experimental methods without specific conditions are usually determined according to national standards. The experimental materials without sources indicated in the following embodiments are all commercially available raw materials. The equipment used in each step in the following embodiments is all conventional equipment. If there is no corresponding national standard, it is carried out according to the general international standard, conventional conditions, or the conditions recommended by the manufacturer. Unless otherwise stated, all parts are by weight and all percentages are by mass percentage. Unless otherwise defined or explained, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention.

[0069] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but it is not limited to the present invention.

[0070] Embodiment 1

[0071] In this embodiment, a high internal phase emulsion stabilized by a polysaccharide substance was prepared. The specific process is as follows:

[0072] (1) Prepare aqueous solutions of sodium carboxymethylcellulose and sodium alginate with mass concentrations of 2.5 wt.%, 1 wt.%, 0.5 wt.%, 0.25 wt.%, and 0.1 wt.%, that is, dissolve a certain mass of the above two polysaccharide substances in pure water, gently stir at room temperature for 2 h to make them fully dispersed, refrigerate and place for more than 12 h to make them fully hydrated, and use the obtained polysaccharide aqueous solutions as the aqueous phase. Adjust the pH to 3.0 before use;

[0073] (2) Use n-dodecane as the oil phase, and mix the aqueous phase and the oil phase at a volume ratio of 1:4 under high-speed shearing. The shearing rate is 9000 rpm, and the shearing time is 30 s to obtain a high internal phase emulsion.

[0074] AsFigure 1 As shown, when the concentrations of the above two polysaccharides are 0.25 wt% or more, high internal phase oil-in-water emulsions with an inverted immobile oil phase volume percentage of 80% can be obtained. Among them, the high internal phase emulsion prepared from sodium carboxymethyl cellulose and sodium alginate did not show instability phenomena such as delamination, oil leakage, and demulsification after being stored at room temperature for five months, showing excellent storage stability. And there is no visible mildew or spoilage phenomenon to the naked eye, which may be closely related to the certain antibacterial and antioxidant properties of sodium carboxymethyl cellulose and sodium alginate.

[0075] The above-prepared high internal phase emulsion can load pigment substances ( Figure 2 A) and has good self-supporting performance and a gel-like appearance ( Figure 2 B and C of, B sodium carboxymethyl cellulose, C sodium alginate) and certain plasticity ( Figure 2 D and E of, D sodium carboxymethyl cellulose, E sodium alginate). From the experimental results, it can be seen that the high internal phase emulsion stabilized by a single polysaccharide substance under acidic conditions prepared in this example has the advantages of high stability, strong gelation, good self-supporting performance, and strong plasticity.

[0076] Analyze the rheological results of the above-prepared high internal phase emulsion. The viscoelastic changes of high internal phase emulsions stabilized by sodium carboxymethyl cellulose or sodium alginate with different concentrations were measured by a rheometer in the shear frequency mode. Figure 2 F shows the rheological property measurement results of high internal phase emulsions prepared when the mass concentrations of sodium carboxymethyl cellulose or sodium alginate are 2.5 wt% and 0.5 wt% respectively. The shear frequency sweep results with the strain fixed at 0.5% show that it has obvious viscoelasticity mainly dominated by elasticity (elastic modulus G′ > viscous modulus G″). The viscoelasticity of the prepared high internal phase emulsion is hardly affected by the shear frequency (0.1 Hz - 10 Hz), and the elastic modulus G′ increases with the increase in the concentration of the stabilizer. These results indicate that the high internal phase emulsions stabilized by sodium carboxymethyl cellulose or sodium alginate both have a very firm and force-resistant gel-like network structure, and the higher the concentration of sodium carboxymethyl cellulose or sodium alginate, the stronger the gelation of the high internal phase emulsion.

[0077] Example 2

[0078] In this example, a high internal phase emulsion stabilized by a polysaccharide substance was prepared. The specific process is as follows:

[0079] (1) Prepare aqueous solutions of commercially available high-ester pectin with mass concentrations of 2.5 wt.%, 1 wt.%, 0.5 wt.%, 0.25 wt.%, and 0.1 wt.%, as well as low-ester pectin from apple and citrus sources, that is, dissolve a certain mass of pectin substances from different sources in pure water, stir gently at room temperature for 2 h to disperse them fully, refrigerate and let stand for more than 12 h to hydrate them fully. The obtained apple and citrus pectin solutions are used as the aqueous phase, and the pH is adjusted to 2.5 before use;

[0080] (2) Using dodecane as the oil phase, mix the aqueous phase and the oil phase at a volume ratio of 1:4 under high-speed shearing. The shearing rate is 9000 rpm, the shearing time is 30 s, and let stand at 25 °C for 12 h. Stable high-internal-phase oil-in-water emulsions with 80% oil-phase volume percentage of high-ester pectin, low-ester apple pectin, and low-ester citrus pectin can be obtained ( Figure 3 A high-ester pectin, 3B low-ester apple pectin, 3C low-ester citrus pectin).

[0081] However, although pectin polysaccharides can form high-internal-phase emulsions with good gel properties, due to their poor antibacterial properties, the high-internal-phase emulsions prepared from pectin from three different commercial sources show unstable phenomena such as mildew after being placed at room temperature for two weeks. And as the storage time prolongs, the situation of mildew, spoilage, color change, and deterioration becomes more serious, and the high-internal-phase emulsion gradually thins and breaks.

[0082] Example 3

[0083] In this example, a high-internal-phase emulsion stabilized by a polysaccharide substance was prepared. The specific process is as follows:

[0084] (1) Prepare an aqueous solution of sodium carboxymethyl cellulose with a mass concentration of 1 wt%, that is, dissolve a certain mass of sodium carboxymethyl cellulose in pure water, stir gently at room temperature for 2 h to disperse it fully, refrigerate or let stand at room temperature for more than 12 h to hydrate it fully. The obtained sodium carboxymethyl cellulose solution is used as the aqueous phase, and the pH is adjusted to 0.5, 2.0, 3.6, 5.2, 6.2, 9.0, and 11.2 before use;

[0085] (2) Using dodecane as the oil phase, mix the aqueous phase and the oil phase at a volume ratio of 1:4 under high-speed shearing. The shearing rate is 8500 rpm, the shearing time is 50 s, and let stand at 25 °C for 12 h (the same experimental effect can be achieved under the condition of 4 °C to 36 °C), to prepare a high-internal-phase emulsion.

[0086] As Figure 4As shown in the upper figure, a carboxymethyl cellulose sodium-stabilized inverted immobile high internal phase water-in-oil emulsion with an oil phase volume percentage of 80% can be obtained under the condition of pH 0.5 - 5.2, and the appearance of the emulsion is a relatively uniform gel-like state. When the pH is above 5.2, a milky white flowing or even stratified emulsion is formed. At this time, carboxymethyl cellulose sodium is difficult to wrap all the oil phase, and obvious oil-water stratification appears in the system.

[0087] Respectively observed the microscopic internal structure of the emulsions prepared under different pH conditions through an optical microscope ( Figure 4 C) and a confocal laser scanning microscope ( Figure 4 B). Among them, Figure 4 The B-colored part is carboxymethyl cellulose sodium stained with a fluorescent white stain. It can be seen that carboxymethyl cellulose sodium uniformly wraps the surface of the oil droplets, and the oil droplets are dense and have a uniform particle size. From the results of this test experiment, it can be known that the carboxymethyl cellulose sodium-stabilized high internal phase emulsion prepared in this example is a water-in-oil type, and has the advantages of high stability and strong gelation. Analyzed the droplet size of the carboxymethyl cellulose sodium-stabilized high internal phase emulsions with different pH values prepared above, and found that when within the appropriate pH range for preparing the high internal phase emulsion, the droplet size of the formed high internal phase emulsion is 5 - 20 μm.

[0088] Example 4

[0089] In this example, a polysaccharide-stabilized high internal phase emulsion was prepared. The specific process is as follows:

[0090] (1) Prepared an aqueous sodium alginate solution with a mass concentration of 1 wt%, that is, dissolved a certain mass of sodium alginate in pure water, gently stirred at room temperature for 2 h to make it fully dispersed, and placed it at refrigerated temperature or room temperature for more than 12 h to make it fully hydrated. The obtained sodium alginate solution was used as the water phase, and the pH was adjusted to 0.5, 1.8, 3.0, 4.0, 5.0, 7.3, and 10.7 respectively before use;

[0091] (2) Using dodecane as the oil phase, the water phase and the oil phase were mixed at a volume ratio of 1:4 under high-speed shearing. The shearing rate was 9000 rpm, the shearing time was 40 s, and it was left to stand at 25 °C for 12 h (the same experimental effect can be achieved under the condition of a temperature of 4 °C - 36 °C), and a high internal phase emulsion was prepared.

[0092] As Figure 6 shown in the upper figure, a sodium alginate-stabilized inverted immobile high internal phase water-in-oil emulsion with an oil phase volume percentage of 80% can be obtained under the condition of pH 0.5 - 4.0, and the appearance of the emulsion is a relatively uniform gel-like state. When the pH is above 4.0, a milky white flowing or even stratified emulsion is formed. At this time, sodium alginate is difficult to wrap all the oil phase, and obvious oil-water stratification appears in the system.

[0093] Optical microscope ( Figure 5 C) and laser confocal microscopy ( Figure 5 B) Observation of the microscopic internal structure of the emulsions prepared under different pH conditions, Figure 5 The color-developing portion B is sodium alginate dyed with fluorescent white dye. It can be seen that sodium alginate is evenly wrapped on the surface of the oil droplets, and the oil droplets are dense and have uniform particle size. From the test experimental results, it can be seen that the sodium alginate-stabilized high internal phase emulsion prepared in this embodiment is an oil-in-water type, and has the advantages of high stability and strong gelation. The droplet size analysis of the sodium alginate-stabilized high internal phase emulsions of different pH values prepared above was conducted, and it was found that when the pH range for preparing the high internal phase emulsion is suitable, the droplet size of the high internal phase emulsion formed is 5 to 20 μm.

[0094] Example 5

[0095] This example prepares a polysaccharide-stabilized high internal phase emulsion, and the specific process is as follows:

[0096] (1) preparing 1 wt% aqueous solutions of high-ester pectin, low-ester apple pectin, and low-ester citrus pectin, i.e., dissolving a certain amount of pectin polysaccharide in pure water, stirring gently at room temperature for 1 h to fully disperse the pectin polysaccharide, and refrigerating or placing the solution at room temperature for more than 12 h to fully hydrate the solution. The resulting aqueous solution of pectin polysaccharide was used as the aqueous phase, and the pH was adjusted to 1.0, 2.0, 3.0, 4.2, 5.5, 8.5, and 10.9 before use;

[0097] (2) Using n-dodecane as the oil phase, the water phase and the oil phase were mixed at a volume ratio of 1:4 under high shear, with a shear rate of 9000 rpm, a shear time of 40 s, and allowed to stand at 25°C for 12 h (the same experimental effect can be achieved at a temperature of 4°C to 36°C) to prepare a high internal phase emulsion.

[0098] like Figure 6 As shown in the upper figure, under the condition of pH 1.0-4.2, an inverted, non-flowing, high internal phase oil-in-water emulsion with a pectin polysaccharide content of 80% by volume of the oil phase can be obtained, and the emulsion has a relatively uniform gel-like appearance. When the pH is above 4.2, a milky white, fluid and even stratified emulsion is formed. At this time, it is difficult for the pectin polysaccharide to encapsulate the entire oil phase, and the system shows obvious oil-water stratification.

[0099] The samples were examined by optical microscope ( Figure 6 C) and laser confocal microscopy ( Figure 6 B) Observation of the microscopic internal structure of the emulsions prepared under different pH conditions, Figure 6The B coloring part is pectin polysaccharide stained with fluorescent white stain. It can be seen that the pectin polysaccharide uniformly wraps the surface of the oil droplets, and the oil droplets are dense and have uniform particle sizes. From the results of this test experiment, it can be known that the high internal phase emulsion stabilized by pectin polysaccharide prepared in this example is an oil-in-water type, and has the advantages of high stability and strong gelation. Analyzing the droplet particle sizes of the high internal phase emulsions stabilized by pectin polysaccharides with different pH values prepared above, it is found that when within the appropriate pH range for preparing the high internal phase emulsion, the droplet particle sizes of the formed high internal phase emulsions are 5 - 20 μm.

[0100] Example 6

[0101] In this example, a high internal phase emulsion stabilized by a polysaccharide substance was prepared. The specific process is as follows:

[0102] (1) Aqueous solutions of sodium carboxymethylcellulose, sodium alginate, and pectin polysaccharide with a mass concentration of 1.0 wt% were respectively prepared, that is, a certain mass of the polysaccharide substance was dissolved in pure water, gently stirred at room temperature for 1.5 h to make it fully dispersed, refrigerated for more than 12 h to make it fully hydrated, and the resulting solution was used as the aqueous phase. The pH was adjusted to 3.0 before use.

[0103] (2) Using n-dodecane as the oil phase, the aqueous phase and the oil phase were mixed at a volume ratio of 1:4 under high-speed shearing. The shearing rate was 9000 rpm, and the shearing time was 30 s. After standing at 25 °C for 12 h, an inverted non-flowing high internal phase oil-in-water emulsion stabilized by the polysaccharide substance under acidic conditions with an oil phase volume percentage of 80% was obtained.

[0104] The thermal stability of the above-prepared high internal phase oil-in-water emulsion was measured. The prepared high internal phase emulsion was placed in a boiling water bath at 100 °C for 0.5 h, and then transferred to an ice-water bath for rapid cooling. It was found that the high internal phase emulsions stabilized by sodium carboxymethylcellulose, sodium alginate, or pectin were all resistant to high-temperature treatment and could still maintain their gel-like structures after high-temperature treatment, as Figure 7 shown (A, sodium carboxymethylcellulose; B, sodium alginate; C, pectin), so they have extremely high thermal stability.

[0105] The temperature responsiveness of the above-prepared high internal phase oil-in-water emulsion was measured. The prepared high internal phase emulsion was placed in a -20 °C refrigerator and frozen for 24 h, and then transferred to a 25 °C constant temperature and humidity chamber and allowed to stand for 4 h to achieve melting. It was found that the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate or pectin was not resistant to low temperature treatment and had poor freeze-thaw stability. A single freeze-thaw treatment could completely demulsify the above-prepared high internal phase emulsion. Then, the oil-water mixed system demulsified after the freeze-thaw treatment was sheared and homogenized at 9000 rpm for 30 s to verify whether re-emulsification could be achieved. It was found that the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate or pectin could be re-emulsified after freeze-thaw demulsification, that is, it had good temperature responsiveness. Moreover, this process of freeze-thaw demulsification and then re-shearing and emulsification could be repeated many times. This excellent temperature responsiveness endows it with great development and application value. For example, it can be used for temperature-responsive encapsulation, preservation, transportation, and re-acquisition of active substances that are easily oxidized and degraded or perishable, toxic and harmful, flammable, explosive, or volatile organic liquids.

[0106] (3) In addition, in subsequent research, based on the structural characteristics of the high internal phase emulsion, it can be applied to different aspects or fields. The milky white, highly gelling high internal phase emulsion prepared in this study can be used for further preparation of oleogels or as a template for functional materials, etc. Moreover, due to its strong gelability, it can be used for 3D printing or 4D printing of foods. Therefore, the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate or pectin has good application potential and development value and can be applied to the development of a variety of products in different fields. Among them, the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate remains very stable when stored for five months under normal temperature varying conditions of 4 °C to 36 °C, further expanding its application scope.

[0107] As can be seen from the above examples, the preparation method of the present invention is simple, green and environmentally friendly. The high internal phase emulsion prepared by sodium carboxymethylcellulose or sodium alginate or pectin under acidic pH conditions is a physical gel, without the generation of trans fatty acids, with good safety, high stability, strong plasticity, and good thermal stability and temperature responsiveness; among them, during the five-month storage process of the high internal phase emulsion prepared by sodium carboxymethylcellulose or sodium alginate, there is no visible mildew or spoilage phenomenon to the naked eye, no oil leakage or demulsification phenomenon, and its structure is very stable, giving full play to the emulsification stability and certain antibacterial properties of sodium carboxymethylcellulose and sodium alginate. Therefore, the high internal phase emulsion stabilized by sodium carboxymethylcellulose or sodium alginate or pectin has good application potential and development value and can be applied to fields such as food, medicine, chemical engineering, and biological engineering materials.

[0108] The above are only the preferred embodiments of the present invention, and thus do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polysaccharide-stabilized high internal phase emulsion, characterized in that, Comprising the following steps: S1: Disperse any one of sodium carboxymethylcellulose, sodium alginate, and pectin in water or an aqueous solution, and after standing, prepare a solution with a mass percentage concentration of 0.05% - 3% and pH < 5.2 as the aqueous phase; S2: Shear-mix the aqueous phase prepared in S1 and the oil phase to obtain a high internal phase emulsion with an oil phase volume fraction of 74% - 88%; Wherein, the droplet size of the high internal phase emulsion is all between 5 - 20 μm; Wherein, when the aqueous phase is a sodium carboxymethylcellulose aqueous solution, the pH range of the aqueous phase is 0.5 - 5.2; Wherein, when the aqueous phase is a sodium alginate aqueous solution, the pH range of the aqueous phase is 0.5 - 4.0; Wherein, when the aqueous phase is a pectin aqueous solution, the pH range of the aqueous phase is 0.5 - 4.2; Wherein, in step S2: The conditions for shear mixing are to shear at 6000 rpm - 9000 rpm for 20 s - 90 s; Wherein, in step S2: After shear mixing, stand for layering at 4°C - 36°C, the standing time is more than 2 h, and remove the lower aqueous phase.

2. The preparation method according to claim 1, characterized in that, In step S1: Add an inorganic salt or an acid-base regulator to the aqueous phase; and / or The dispersion time is not less than 1 h; and / or The standing time is not less than 12 h.

3. The preparation method according to claim 1, characterized in that, In step S2, the oil phase includes at least one of vegetable oil, cyclohexane, n-hexane, and n-dodecane.

4. A polysaccharide-stabilized high internal phase emulsion prepared by the preparation method according to any one of claims 1 - 3.

5. The application of sodium carboxymethylcellulose, sodium alginate, and pectin in the preparation of the high internal phase emulsion or its product as claimed in claim 4.

6. The application according to claim 5, wherein The high internal phase emulsion can be emulsified again after freeze-thaw demulsification.

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