A method for preparing a high internal phase emulsion stabilized only by proteins

Abstract

The application discloses a preparation method of a high internal phase emulsion stabilized only by proteins, which mixes a completely hydrated protein solution as a water phase with an oil phase, and controls the hydrodynamic characteristics of a shearing emulsification process to obtain the high internal phase emulsion stabilized only by proteins. The preparation method of the application can obtain the high internal phase emulsion stabilized only by food-grade proteins through one-step shearing emulsification without other measures. The prepared high internal phase emulsion has good gel characteristics, stability and high safety, and can be used as a substitute for partially hydrogenated vegetable oil and saturated fatty acids. Meanwhile, the method is simple in operation, low in preparation cost and suitable for large-scale industrial promotion.

Description

Technical Field

[0001] This invention relates to a method for preparing an emulsion, specifically a method for preparing a protein-stabilized high internal phase emulsion. Background Technology

[0002] Partially hydrogenated vegetable oils are widely used in the food industry; however, the hydrogenation process produces trans fatty acids, and excessive intake of these may increase the risk of cardiovascular and other diseases. Against this backdrop, finding alternatives to partially hydrogenated vegetable oils has become a pressing challenge for the modern food industry. High internal phase emulsions, possessing semi-solid viscoelasticity and stability, can mimic the texture characteristics of hydrogenated vegetable oils and are one potential alternative.

[0003] Emulsions formed by dispersing oil (dispersed phase) into water (continuous phase) through the addition of solid particles are also known as oil-in-water Pickering emulsions. The role of the solid particles is to form a physical barrier through near-irreversible adsorption at the oil / water interface, thus maintaining the stability of the emulsion. When the volume fraction of the oil phase... When the coefficient of thermal equilibrium (CPE) is greater than 0.74, the droplets compress against each other to form polyhedra, and the emulsion at this point is called a high internal phase emulsion. High internal phase emulsions are generally prepared using a step-by-step method, but this is accompanied by… The gradual increase in the internal phase can lead to a phase transition phenomenon that is detrimental to its formation. The "one-step method," which has emerged in recent years, is favored because it can suppress the occurrence of phase transitions. However, most studies suggest that this method has stringent requirements for the interfacial wettability of solid particles, requiring the three-phase contact angle (θ) of the interfacial particles to be close to 90°. It is known that most proteins have poor wettability in the oil phase (θ < 90°), therefore researchers often focus on adjusting the surface wettability of proteins through physical or chemical means. However, the cumbersome and complex process of surface modification limits the large-scale application and promotion of high internal phase emulsions in the food industry. In summary, currently disclosed patent technologies typically focus on the regulation of protein properties. Therefore, seeking simpler, lower-cost, and industrially applicable high internal phase emulsions is of great significance. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing a protein-stabilized high internal phase emulsion, which is prepared by controlling the dynamic characteristics of the fluid during shear emulsification.

[0005] Technical solution: The method for preparing protein-stabilized high internal phase emulsion described in this invention involves mixing a fully hydrated protein solution as the aqueous phase with an oil phase, and controlling the hydrodynamic characteristics of the shear emulsification process to directly obtain a protein-stabilized high internal phase emulsion.

[0006] The preparation method of the high internal phase emulsion stabilized by protein only, the completely hydrated protein solution is obtained by completely dissolving food-grade protein raw materials in distilled water through stirring, and then placing the protein solution in an environment of 2-8°C for more than 12 hours.

[0007] The preparation method of the high internal phase emulsion stabilized by protein only, the fluid dynamics characteristics in the shearing emulsification process are controlled, specifically referring to the flow of the fluid changing from turbulent flow to laminar flow.

[0008] The preparation method of the high internal phase emulsion stabilized by protein only, the food-grade protein used includes at least one of sodium caseinate, whey protein isolate, whey protein concentrate, soy protein isolate, collagen and gelatin.

[0009] The preparation method of the high internal phase emulsion stabilized by protein only, the concentration of the protein solution is 0.2%wt.-3.0%wt.

[0010] The preparation method of the high internal phase emulsion stabilized by protein only, the oil phase used includes at least one of soybean oil, sunflower oil, palm oil, corn oil, rapeseed oil and medium-chain triglyceride.

[0011] The preparation method of the high internal phase emulsion stabilized by protein only, in the mixture of the water phase and the oil phase, the volume fraction of the oil phase is 0.70-0.85.

[0012] The preparation method of the high internal phase emulsion stabilized by protein only, the device used for shearing is a shearing emulsifier with a stator-rotor structure, the shearing rate is 10000-13000 revolutions / minute, and the shearing time is 10-60 seconds.

[0013] The high internal phase emulsion stabilized by protein only is prepared by the preparation method of the protein-stabilized high internal phase emulsion.

[0014] The high internal phase emulsion stabilized by protein only is used as a partial replacement of partially hydrogenated vegetable oil and saturated fatty acid.

[0015] Advantages: Compared with the prior art, the present application has the following advantages: (1) The high internal phase emulsion stabilized by protein only can be obtained by the direct shearing emulsification method without using other measures. (2) In the present application, the fluid dynamics characteristics in the shearing emulsification process are controlled, so that the fluid changes from turbulent flow to laminar flow, thereby directly preparing the high internal phase emulsion stabilized by protein only without physical or chemical modification treatment of the protein. (3) The prepared high internal phase emulsion has good gel characteristics, stability and high safety. At the same time, the method is simple to operate, low in preparation cost and suitable for large-scale industrial promotion. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Schematic diagram of the preparation of high internal phase emulsions stabilized solely by proteins by modulating the hydrodynamic characteristics during the shear emulsification process of the present application;

[0017] Figure 2 High speed camera images of the shear emulsification process of high internal phase emulsions stabilized solely by proteins;

[0018] Figure 3 (a) Preferred regions of high internal phase emulsions stabilized by whey protein isolate, sodium caseinate and gelatin, respectively, (b) appearance images of high internal phase emulsions;

[0019] Figure 4 (a) Amplitude sweep rheological profiles of high internal phase emulsions stabilized by whey protein isolate at different concentrations (d) at different oil phase volume fractions, (b) Amplitude sweep rheological profiles of high internal phase emulsions stabilized by sodium caseinate at different concentrations (e) at different oil phase volume fractions, and (c) Amplitude sweep rheological profiles of high internal phase emulsions stabilized by gelatin at different concentrations (f) at different oil phase volume fractions;

[0020] Figure 5 (a) Influence of pasteurization and freeze-thaw treatment on the appearance of high internal phase emulsions stabilized by whey protein isolate, sodium caseinate and gelatin, respectively, (b) Rheological profiles of high internal phase emulsions stabilized by whey protein isolate, sodium caseinate and gelatin, respectively, during temperature sweep test. DETAILED DESCRIPTION

[0021] The following examples illustrate the present application. It should be understood that the examples described herein are merely illustrative of the present application and do not limit the application.

[0022] The experimental methods used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and instruments used are conventional unless otherwise specified and are available to those skilled in the art through commercial channels.

[0023] The preparation process of high internal phase emulsions stabilized solely by proteins according to the present application is as follows Figure 1 The protein solution is used as the water phase and the sunflower oil is used as the oil phase and they are mixed in advance, and then the shear emulsification is performed using an emulsifier with a stator-rotor structure. By screening different shear rates and oil phase volume fractions, when the shear rate is greater than 1000 rpm and the oil phase volume fraction is greater than 0.70, the turbulent kinetic energy generated by the shear is dissipated due to the formation of self-organizing droplet structures, thereby realizing the transition of the flow behavior of the fluid from turbulent flow to laminar flow, and finally successfully preparing high internal phase emulsions stabilized solely by proteins.

[0024] Example 1

[0025] Sodium caseinate was completely dissolved in distilled water at room temperature using a magnetic stirrer (stirring rate 500 r.p.m) at a concentration range of 0.2% wt. The sodium caseinate solution was then left in an environment of 2-8 °C for 12 h to ensure complete hydration of the protein. The sodium caseinate solution and sunflower oil were used as the aqueous and oil phases, respectively, and the sunflower oil was slowly injected into the aqueous phase. The mixture solution with a volume fraction of 0.8 was used as the example, while the mixture solution with a volume fraction of 0.5 was used as the control. The mixture solution was homogenized using a Flacktek FA25 high shear dispersing emulsifier at a shear rate of 10,000 rpm for 10 s. The fluid motion trajectories of the control and example during emulsification were captured using a high-speed camera as shown in Figure 2 The results show that when the volume fraction of the oil phase is 0.5, the fluid motion trajectories exhibit irregular turbulent flow. However, when the volume fraction of the oil phase is 0.8, the fluid motion trajectories change from turbulent flow to laminar flow, and a high internal phase emulsion stabilized only by protein is formed at this time.

[0026] Example 2

[0027] Whey protein isolate was completely dissolved in distilled water at room temperature using a magnetic stirrer (stirring rate 500 r.p.m) at a concentration range of 0.1-3.0% wt. The whey protein isolate solution was then left in an environment of 2-8 °C for 12 h to ensure complete hydration of the protein. The whey protein isolate solution and sunflower oil were used as the aqueous and oil phases, respectively, and the sunflower oil was slowly injected into the aqueous phase. The volume fraction of the oil phase at this time ranged from 0.70 to 0.95. The mixture solution was emulsified and homogenized using a Flacktek FA25 high shear dispersing emulsifier at a shear rate of 10,000 rpm for 10 s, and the preferred region of the high internal phase emulsion is shown in Figure 3 The results show that when the concentration of whey protein isolate ranges from 0.5 to 3.0% wt. and the volume fraction of the oil phase ranges from 0.70 to 0.85, a stable high internal phase emulsion can be obtained. In addition, according to the appearance diagram, the prepared high internal phase emulsion with a protein concentration of 1% wt. has good self-supporting and stability. The results are shown in Figure 4

[0028] Example 3

[0029] ​Sodium caseinate was completely dissolved in distilled water at room temperature using a magnetic stirrer (stirring rate 500 r.p.m) at a concentration range of 0.1 - 3.0% wt. The sodium caseinate solution was then left in an environment of 2-8°C for 12h to ensure complete hydration of the protein. The sodium caseinate solution and sunflower oil were used as the aqueous and oil phases, respectively, and the sunflower oil was slowly injected into the aqueous phase, at this point the volume fraction of the oil phase ranged from 0.70 to 0.95. The mixed solution was emulsified using a Frick FA25 high shear dispersing emulsifier at a shear rate of 10000 rpm for 10s, the preferred region of high internal phase emulsions is shown in Table 1. Figure 3 The results show that stable high internal phase emulsions were obtained at a sodium caseinate concentration range of 0.5 - 3.0% wt. and a volume fraction of the oil phase range of 0.70 - 0.85. Furthermore, from the appearance chart it can be seen that the high internal phase emulsion prepared with a protein concentration of 1% wt. had good self-supporting properties and stability. The sodium caseinate concentration was in the range of 0.2% wt - 3.0% wt and the volume fraction of the oil phase was in the range of 0.70 - 0.85, the results are shown in Table 2. Figure 4

[0030] Example 4

[0031] Gelatin was completely dissolved in distilled water at 60°C using a magnetic stirrer (stirring rate 500 r.p.m) at a concentration range of 0.1 - 3.0% wt. The gelatin solution was then left in an environment of 2-8°C for 12h to ensure complete hydration of the protein. The gelatin and sunflower oil were used as the aqueous and oil phases, respectively, and the sunflower oil was slowly injected into the aqueous phase, at this point the volume fraction of the oil phase ranged from 0.70 to 0.95. The mixed solution was emulsified using a Frick FA25 high shear dispersing emulsifier at a shear rate of 10000 rpm for 10s, the preferred region of high internal phase emulsions is shown in Table 4. Figure 3 The results show that stable high internal phase emulsions were obtained at a gelatin concentration range of 0.5 - 3.0% wt. and a volume fraction of the oil phase range of 0.70 - 0.85. Furthermore, from the appearance chart it can be seen that the high internal phase emulsion prepared with a protein concentration of 1% wt. had good self-supporting properties and stability. The gelatin concentration was in the range of 0.2% wt - 3.0% wt and the volume fraction of the oil phase was in the range of 0.70 - 0.85, the results are shown in Table 5. Figure 4

[0032] Example 5

[0033] Small amplitude oscillatory test stress sweeps were performed on the high internal phase emulsions in the preferred region of Example 2, Example 3 and Example 4, see Table 6. Figure 3 ​​The results show that in the range of stress less than 0.1%, the elastic modulus (G') of all the proteins is greater than the loss modulus (G"), which indicates that the rheological characteristics of the high internal phase emulsion exhibit the viscoelastic solid. When the stress reaches a certain point, G' rapidly decreases and G" first increases and then decreases, at this time, the high internal phase emulsion exhibits the characteristics of shear thinning. With the increase of the protein concentration, G' gradually increases, which indicates that the plasticity of the high internal phase emulsion is enhanced. Meanwhile, with the increase of the volume fraction of the oil phase, G' gradually increases, which also indicates that the plasticity of the high internal phase emulsion is enhanced. In addition, compared with the high internal phase emulsions stabilized by the other two proteins, the high internal phase emulsion stabilized by gelatin exhibits stronger plasticity.

[0034] Example 6

[0035] The high internal phase emulsions stabilized by proteins only prepared in Example 2, Example 3 and Example 4 are subjected to pasteurization, the pasteurization temperature is 65℃, and the pasteurization time is 30 min. The stability and rheological characteristics of the high internal phase emulsions after pasteurization are shown in Table 3. Figure 5 The results show that the pasteurization treatment has no obvious effect on the stability of the high internal phase emulsion. Meanwhile, the temperature scanning results at a fixed frequency (1.0 Hz) show that the high internal phase emulsions stabilized by different proteins have different rheological characteristics, but the high internal phase emulsion always exhibits viscoelastic characteristics during the temperature scanning process. The high internal phase emulsions based on whey protein isolate and sodium caseinate form more stable forms before and after heating, while the rheological characteristics of the high internal phase emulsion based on gelatin do not change obviously. In addition, the freeze-thaw cycle results show that the high internal phase emulsion stabilized by proteins should avoid frozen storage to destroy its stability.

[0036] In summary, the present application realizes the preparation of the high internal phase emulsion stabilized by food-grade proteins only by controlling the hydrodynamic characteristics in the shear emulsification process without physical or chemical modification treatment of the proteins. The operation method of the present application is simple, and the preparation cost is low. The prepared high internal phase emulsion is in a semi-solid form, has strong plasticity and stability. Meanwhile, all the raw materials used are food-grade, safe and have strong plasticity, so they can be used as substitutes for partially hydrogenated vegetable oil and saturated fatty acids. In addition, the high internal phase emulsion stabilized by proteins only can be pasteurized without affecting its stability, so it can save the storage cost. Therefore, the high internal phase emulsion stabilized by food-grade proteins only prepared by the present application can be widely used in the food industry field, and is also suitable for the fields of pharmaceuticals, chemical industry and biological engineering materials.

Claims

1. A method for preparing a high internal phase emulsion stabilized by proteins only, characterized in that, The fully hydrated protein solution is obtained by completely dissolving food-grade protein raw materials in distilled water through stirring, and then placing the protein solution in an environment of 2-8 ℃ for more than 12 h; the fluid dynamics characteristics of the shearing emulsification process are specifically the flow of fluid changing from turbulent flow to laminar flow; the volume fraction of the oil phase in the mixture of the water phase and the oil phase is 0.70-0.85; the shearing equipment is a shearing emulsification machine with a stator-rotor structure, the shearing rate is 10000-13000 rpm, and the shearing time is 10-60 s. The food-grade protein includes at least one of sodium caseinate, whey protein isolate, whey protein concentrate, soy protein isolate, collagen protein and gelatin.

2. The method of claim 1, wherein the high internal phase emulsion stabilized only by proteins is prepared by, The concentration of the protein solution is 0.5 %wt.-3.0 % wt.

3. The method for preparing a protein-stabilized high-internal-phase emulsion according to claim 1, characterized in that, The oil phase includes at least one of soybean oil, sunflower oil, palm oil, corn oil, rapeseed oil and medium-chain triglyceride.

4. The method of claim 1, wherein the high internal phase emulsion stabilized only by proteins is prepared by, The preparation method of the protein-stabilized high internal phase emulsion is prepared by any one of claims 1-4.

5. A high internal phase emulsion stabilized by proteins only, characterized in that, 6. The use of the protein-stabilized high internal phase emulsion of claim 5 in the preparation of substitutes for hydrogenated vegetable oil and substitutes for saturated fatty acids. ​

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