High-internal-phase emulsion ink material as well as preparation method and application thereof

Abstract

The invention relates to a high-internal-phase emulsion ink material as well as a preparation method and application thereof, and belongs to the technical field of preparation of emulsion ink materials. According to the preparation method of the high-internal-phase emulsion ink material, a soybean protein isolate solution is subjected to pulsed electric field treatment and then mixed with a polysaccharide solution to serve as a water phase, vegetable oil and bioactive substances are mixed to serve as an oil phase, finally, the water phase and the oil phase are mixed and then subjected to high-speed shearing, and the high-internal-phase emulsion ink material is prepared. The prepared high-internal-phase emulsion ink material has high stability after freeze-thaw storage and high retention rate of bioactive substances, can effectively embed the bioactive substances, better realizes slow release of the bioactive substances to achieve the purpose of targeted transport, improves the retention capacity of the emulsion to internal-phase substances under the freeze-thaw condition, and improves the stability of the ink material. The method has huge application prospects and development potential in the aspect of preparing the 3D printing functional food, and a new technical direction and technical support can be provided for the 3D printing functional food.

Description

Technical Field

[0001] The present invention relates to a high internal phase emulsion ink material, a preparation method thereof and an application, belonging to the technical field of emulsion ink material preparation. Background Art

[0002] 3D printing has been increasingly applied in the fields of medicine, healthcare and food industry. 3D printing allows highly customized foods, which can achieve enhanced nutritional components by precisely controlling the addition of bioactive substances to meet the dietary needs of individuals with allergies or dietary restrictions. As a two-phase system, high internal phase emulsions (HIPEs) are materials for preparing ink materials for 3D printing. However, freeze-thaw instability has always been the main problem in the application process of HIPEs. The freeze-thaw instability of HIPEs may cause the layers around individual oil droplets to rupture and allow the oil droplets to rapidly coalesce, resulting in the separation of HIPEs into the original aqueous and oil phases, which greatly destroys the encapsulation and utilization of bioactive substances retained in the emulsion.

[0003] Soybean protein isolate contains 20 essential amino acids, has high nutritional value and versatility, and has been widely used in the fields of food, cosmetics and medicine. Soybean protein isolate is easy to form protein particles of nanometer size, giving it unique advantages in delivering lipophilic nutrients. Moreover, the amphiphilicity (hydrophilicity and hydrophobicity) of soybean protein isolate enables it to diffuse and adsorb at the oil droplet interface during the emulsification process, thus stabilizing the emulsion interface. Although the emulsifying performance of soybean protein isolate has been recognized in a large number of studies, in the field of 3D printing, soybean protein isolate still fails to meet the requirements of high-emulsifying-performance proteins in actual food industrial production, resulting in very limited application scope. Therefore, when using soybean protein isolate alone as an emulsifier, it is generally necessary to improve its functional properties by means of modification, addition of polysaccharides, etc.

[0004] However, the research on stabilizing protein emulsion systems mainly focuses on: first forming a protein-polysaccharide mixed system and then preparing the emulsion, but the prepared emulsion often has problems such as low freeze-thaw stability and low retention rate of bioactive substances during the application process. Therefore, there is an urgent need to develop a preparation method for a new type of emulsion ink material with high freeze-thaw stability and high retention rate of active substances to comprehensively solve the above problems. Summary of the Invention

[0005] Aiming at the defects and deficiencies existing in the prior art, the purpose of the present invention is to provide a preparation method for a high internal phase emulsion ink material, which has a simple process, is suitable for industrial production, and the prepared ink material is a protein-based high internal phase emulsion, having high stability after freeze-thaw storage and high retention rate of bioactive substances.

[0006] The present invention also aims to provide a high internal phase emulsion ink material prepared by the above preparation method, which has high stability after freeze-thaw storage and a high retention rate of bioactive substances.

[0007] The present invention also aims to provide an application of the above high internal phase emulsion ink material.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A preparation method of a high internal phase emulsion ink material includes the following steps:

[0010] (1) Subject the soy protein isolate solution to pulsed electric field treatment, then add the polysaccharide solution and stir to mix, obtaining a protein-polysaccharide composite solution, and use the protein-polysaccharide composite solution as the aqueous phase; separately take a bioactive substance and mix it evenly with vegetable oil as the oil phase; wherein, the polysaccharide used in the polysaccharide solution is one of high methoxyl pectin, xanthan gum, and konjac glucomannan.

[0011] (2) Mix the aqueous phase and the oil phase, and then perform high-speed shearing to obtain the high internal phase emulsion ink material.

[0012] In one embodiment, in step (1), the process conditions of the pulsed electric field treatment are: the pulse intensity is 20 - 40 kV / cm, the pulse width is 40 - 60 μs, the pulse frequency is 0.8 k - 1.2 kHz, and the flow rate is 8 - 12 mL / min.

[0013] In one embodiment, in step (1), the rotation speed of the stirring and mixing is 300 - 500 r / min, and the stirring and mixing time is 1 - 3 h.

[0014] Considering further improving the stability of the emulsion ink material after freeze-thaw storage and the retention rate of bioactive substances, in one embodiment, in step (1), the mass concentration of the soy protein isolate solution is 30 - 50 mg / mL; the mass concentration of the polysaccharide solution is 15 - 25 mg / mL; the mixing volume ratio of the soy protein isolate solution to the polysaccharide solution is (0.8 - 1.2)∶(0.8 - 1.2).

[0015] In a further preferred embodiment, the mass concentration of the soy protein isolate solution is 40 mg / mL; the mass concentration of the polysaccharide solution is 20 mg / mL; the mixing volume ratio of the soy protein isolate solution to the polysaccharide solution is 1∶1; the polysaccharide used in the polysaccharide solution is high methoxyl pectin.

[0016] After the bioactive substance is embedded in the emulsion ink material, it will not significantly affect the particle size, microstructure, and 3D printing effect of the emulsion system. Therefore, the present invention does not particularly limit the type of bioactive substance. Those skilled in the art can make a conventional selection of the type of bioactive substance embedded in the emulsion ink material according to the functionality and nutritional requirements of 3D printed foods. In one embodiment, in step (1), the bioactive substance is one of curcumin, carotenoid, and astaxanthin; in the oil phase, the mass concentration of the bioactive substance is 0.05% - 0.2%, more preferably 0.1%.

[0017] The type of vegetable oil will not significantly affect the performance of the emulsion ink material of the present invention. Therefore, the present invention does not particularly limit the type of vegetable oil. Those skilled in the art can conventionally select a suitable type of vegetable oil. In one embodiment, in step (1), the vegetable oil is one of soybean oil, corn oil, and peanut oil.

[0018] In one embodiment, in step (2), the volume ratio of the aqueous phase to the oil phase is 1:(3 - 5). More preferably, the volume ratio of the aqueous phase to the oil phase is 1:4.

[0019] In one embodiment, in step (2), the rotation speed of the high-speed shearing is 10000 - 12000 r / min, and the time of the high-speed shearing is 3 - 6 min.

[0020] A high internal phase emulsion ink material prepared by the above preparation method.

[0021] An application of the above high internal phase emulsion ink material, as an ink material in 3D printing foods.

[0022] The technical solution of the present invention has the following advantages and beneficial effects:

[0023] The preparation method of the high internal phase emulsion ink material provided by the present invention first performs pulsed electric field treatment on the soy protein isolate solution, then mixes it with the polysaccharide solution as the aqueous phase, and separately mixes the vegetable oil and the bioactive substance as the oil phase. Finally, the aqueous phase and the oil phase are mixed and then subjected to high-speed shearing, thereby preparing the high internal phase emulsion ink material.

[0024] The above preparation method of the present invention has a simple process, is easy to control, and is suitable for industrial production. In the preparation process of the high internal phase emulsion of the present invention, a pulsed electric field is used to treat the soy protein isolate solution. Pulsed electric field (PEF) is a short-term electric treatment technology. Through PEF treatment, the present invention changes the secondary and tertiary structures of proteins, exposes more free amino groups, and enhances protein functions. At the same time, the free radicals generated by pulsed electric field treatment affect the interactions within protein molecules and change the ionic interactions of proteins to increase the apparent charge of proteins, promoting the interaction between proteins and polysaccharides to form complexes. Further, the polysaccharide selected in the present invention can charge the oil droplets in the system, increase the viscosity and stability of the emulsion, and can improve the emulsion stability by reducing the surface tension and increasing the viscosity, promoting the spontaneous formation of an emulsion with a smaller particle size under mechanical stirring. Finally, after forming the aqueous phase by combining soy protein isolate and polysaccharide, the present invention further combines it with oil, thereby obtaining a freeze-thaw resistant high internal phase emulsion with excellent viscoelastic properties and stronger stability.

[0025] Experiments have confirmed that the high internal phase emulsion ink material prepared by the present invention has high stability after freeze-thaw storage and a high retention rate of bioactive substances. It can effectively encapsulate bioactive substances, better achieve the slow release of bioactive components to achieve the purpose of targeted transport, and improve the retention ability of the emulsion for internal phase substances under freeze-thaw conditions. Therefore, the high internal phase emulsion ink material prepared by the present invention has great application prospects and development potential in the preparation of 3D printing functional foods, and can also provide new technical directions and technical support for 3D printing functional foods. Brief Description of the Drawings

[0026] Figure 1 It is the average particle size diagram of the emulsion ink materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention;

[0027] Figure 2 It is the laser confocal diagram of the emulsion ink materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention;

[0028] Figure 3 It is the 3D printing visual appearance diagram of the emulsion ink materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention;

[0029] Figure 4 It is the encapsulation rate result of curcumin in the emulsion ink materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention. Detailed Description of the Invention

[0030] To better understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that, without conflict, the features in the embodiments of the present invention can be combined with each other. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below. For those of ordinary skill in the art, other embodiments can also be obtained based on the provided embodiments without creative efforts.

[0031] In the following examples and comparative examples of the present invention, the soy protein isolate used is from the Shandong Yuwang brand. High-methoxyl pectin (esterification degree 62%) is from Davisco Foods, USA. Xanthan gum (USP grade) is from Shanghai Aladdin. Konjac glucomannan is from Shanghai Macklin Biochemical Co., Ltd. Curcumin is from Shanghai Aladdin. Other raw materials, etc., unless otherwise specified, are commonly used materials in the art that can be obtained through commercial channels.

[0032] In the following embodiments of the present invention, taking curcumin as an example, the encapsulation effect of the emulsion ink material and the retention rate of bioactive substances will be described. In other embodiments, those skilled in the art can make a conventional selection of the types of bioactive substances encapsulated in the emulsion ink material according to the functionality and nutritional requirements of 3D printed foods. For example, the bioactive substances encapsulated can also be carotenoids or astaxanthin.

[0033] Example 1

[0034] This example provides a high internal phase emulsion ink material, and its preparation method includes the following steps:

[0035] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place it in a 4°C refrigerator for hydration for 12 h, take it out and restore to room temperature to obtain a 40 mg / mL soy protein isolate solution. Separately, dissolve 2 g of high-methoxyl pectin in 100 mL of deionized water, stir at room temperature for 2 h, then place it in a 4°C refrigerator for hydration for 12 h to obtain a 20 mg / mL polysaccharide solution (high-methoxyl pectin solution).

[0036] (2) Pulse - electric - field - treat 20 mL of soy protein isolate solution with a concentration of 40 mg / mL, then add 20 mL of polysaccharide solution (high - methoxyl pectin solution) with a concentration of 20 mg / mL, and stir - mix at a speed of 350 r / min for 2 h to obtain a protein - polysaccharide composite solution, which is used as the aqueous phase. Among them, the process conditions of the pulse - electric - field treatment are: pulse intensity is 30 kV / cm, pulse width is 50 μs, pulse frequency is 1.0 kHz, and flow rate is 10 mL / min. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0037] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high - speed shearing at a speed of 12000 r / min for 3 min to obtain the high - internal - phase emulsion ink material of this example.

[0038] Example 2

[0039] This example provides a high - internal - phase emulsion ink material, and its preparation method includes the following steps:

[0040] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place it in a 4°C refrigerator for hydration for 12 h, take it out and restore to room temperature to obtain a 40 mg / mL soy protein isolate solution. Dissolve 2 g of xanthan gum in 100 mL of deionized water, stir at room temperature for 2 h, then place it in a 4°C refrigerator for hydration for 12 h to obtain a 20 mg / mL polysaccharide solution (xanthan gum solution).

[0041] (2) Pulse - electric - field - treat 20 mL of soy protein isolate solution with a concentration of 40 mg / mL, then add 20 mL of polysaccharide solution (xanthan gum solution) with a concentration of 20 mg / mL, and stir - mix at a speed of 350 r / min for 2 h to obtain a protein - polysaccharide composite solution, which is used as the aqueous phase. Among them, the process conditions of the pulse - electric - field treatment are: pulse intensity is 30 kV / cm, pulse width is 50 μs, pulse frequency is 1.0 kHz, and flow rate is 10 mL / min. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0042] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high - speed shearing at a speed of 12000 r / min for 3 min to obtain the high - internal - phase emulsion ink material of this example.

[0043] Example 3

[0044] This example provides a high - internal - phase emulsion ink material, and its preparation method includes the following steps:

[0045] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for hydration for 12 h. After taking it out and restoring to room temperature, a soy protein isolate solution with a concentration of 40 mg / mL is obtained. Dissolve 2 g of konjac glucomannan in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for hydration for 12 h to obtain a polysaccharide solution (konjac glucomannan solution) with a concentration of 20 mg / mL.

[0046] (2) Perform pulsed electric field treatment on 20 mL of the soy protein isolate solution with a concentration of 40 mg / mL, then add 20 mL of the polysaccharide solution (konjac glucomannan solution) with a concentration of 20 mg / mL, and stir and mix at a rotation speed of 350 r / min for 2 h to obtain a protein-polysaccharide composite solution, which is used as the aqueous phase; among them, the process conditions of the pulsed electric field treatment are: the pulse intensity is 30 kV / cm, the pulse width is 50 μs, the pulse frequency is 1.0 kHz, and the flow rate is 10 mL / min. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0047] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high-speed shearing at a rotation speed of 12000 r / min for 3 min to obtain the high internal phase emulsion ink material of this example.

[0048] Comparative Example 1

[0049] This comparative example provides an emulsion ink material, and its preparation method includes the following steps:

[0050] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for hydration for 12 h. After taking it out and restoring to room temperature, a soy protein isolate solution with a concentration of 40 mg / mL is obtained.

[0051] (2) Use the soy protein isolate solution obtained in step (1) as the aqueous phase. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0052] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high-speed shearing at a rotation speed of 12000 r / min for 3 min to obtain the emulsion ink material of this comparative example.

[0053] Comparative Example 2

[0054] This comparative example provides an emulsion ink material, and its preparation method includes the following steps:

[0055] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for 12 h of hydration. After taking it out and restoring to room temperature, a soy protein isolate solution with a concentration of 40 mg / mL is obtained. Dissolve 2 g of high-methoxyl pectin in 100 mL of deionized water, stir at room temperature for 2 h, and then place in a 4 °C refrigerator for 12 h of hydration to obtain a polysaccharide solution (high-methoxyl pectin solution).

[0056] (2) Add 20 mL of a polysaccharide solution (high-methoxyl pectin solution) with a concentration of 20 mg / mL to 20 mL of a soy protein isolate solution with a concentration of 40 mg / mL, stir and mix at a rotation speed of 350 r / min for 2 h to obtain a protein-polysaccharide composite solution, and use the protein-polysaccharide composite solution as the aqueous phase. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0057] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high-speed shearing at a rotation speed of 12000 r / min for 3 min to obtain the emulsion ink material of this comparative example.

[0058] Comparative Example 3

[0059] This comparative example provides an emulsion ink material, and its preparation method includes the following steps:

[0060] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for 12 h of hydration. After taking it out and restoring to room temperature, a soy protein isolate solution with a concentration of 40 mg / mL is obtained.

[0061] (2) Perform pulsed electric field treatment on 40 mL of a soy protein isolate solution with a concentration of 40 mg / mL to obtain a pulsed-treated soy protein isolate solution, and use it as the aqueous phase; among them, the process conditions of the pulsed electric field treatment are: the pulse intensity is 30 kV / cm, the pulse width is 50 μs, the pulse frequency is 1.0 kHz, and the flow rate is 10 mL / min. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0062] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high-speed shearing at a rotation speed of 12000 r / min for 3 min to obtain the emulsion ink material of this comparative example.

[0063] Comparative Example 4

[0064] This comparative example provides an emulsion ink material, and its preparation method includes the following steps:

[0065] (1) Dissolve 4 g of soy protein isolate in 100 mL of deionized water, stir at room temperature for 2 h, then place in a 4 °C refrigerator for 12 h of hydration. After taking it out and restoring to room temperature, a 40 mg / mL soy protein isolate solution is obtained. Dissolve 2 g of high-methoxyl pectin in 100 mL of deionized water, stir at room temperature for 2 h, and then place in a 4 °C refrigerator for 12 h of hydration to obtain a 20 mg / mL polysaccharide solution (high-methoxyl pectin solution).

[0066] (2) Add 20 mL of the polysaccharide solution (high-methoxyl pectin solution) with a concentration of 20 mg / mL to 20 mL of the soy protein isolate solution with a concentration of 40 mg / mL, stir and mix at a rotation speed of 350 r / min for 2 h to obtain a protein-polysaccharide composite solution; perform pulsed electric field treatment on the protein-polysaccharide composite solution. The process conditions of the pulsed electric field treatment are: pulse intensity is 30 kV / cm, pulse width is 50 μs, pulse frequency is 1.0 kHz, and flow rate is 10 mL / min. Take the protein-polysaccharide composite solution after pulsed electric field treatment as the aqueous phase. Separately, add curcumin to soybean oil and mix evenly to obtain the oil phase; the mass concentration of curcumin in the oil phase is 0.1%.

[0067] (3) Mix the aqueous phase and the oil phase at a volume ratio of 1:4, and then perform high-speed shearing at a rotation speed of 12,000 r / min for 3 min to obtain the emulsion ink material of this comparative example.

[0068] Test Example 1. Determination of the average particle size of the emulsion

[0069] Use a laser particle size analyzer Mastersizer3000 to measure the particle size (D 3,2 ) of the emulsion ink materials prepared in Examples 1-3 and Comparative Examples 1-4. The results are as Figure 1 shown.

[0070] It can be Figure 1 seen that there are significant differences in the particle size of the emulsion ink materials between the comparative examples and the examples, indicating that the addition of the polysaccharide solution and the change in pulsed electric field treatment will both affect the particle size of the emulsion. Compared with Comparative Examples 1-3, the particle size of the emulsions in Examples 1-3 is smaller, indicating that the emulsions prepared by adding the polysaccharide solution and applying pulsed electric fields have better stability. Compared with Comparative Example 4, the particle size of the emulsions in Examples 1-3 is smaller, indicating that the emulsion prepared by first using pulsed electric field treatment on the protein solution and then preparing the protein-polysaccharide composite solution has stronger stability.

[0071] Test Example 2. Analysis of the microstructure of the emulsion

[0072] The microstructures of the emulsion ink materials prepared by the methods of Comparative Examples 1-4 and Examples 1-3 were analyzed using a confocal laser scanning microscope (CLSM). The specific steps were as follows: 20 μL of 0.2% (w / w) nile red solution and 20 μL of 0.5% (w / w) nile blue solution were respectively added to the samples to stain lipids and proteins. The staining process lasted for 5 minutes. After staining, the excess staining solution was aspirated, the samples were covered with cover glasses, and observed under an objective lens at a magnification of 20 times. Staining and observation were carried out in a place away from light. Nile red and nile blue were observed at excitation and emission wavelengths of 488 / 543 nm and 561 / 613 nm, respectively. The confocal laser images of each emulsion ink material sample are as Figure 2 shown. Among them, green represents oil droplets and blue represents protein.

[0073] As can be seen from Figure 2 , compared with Comparative Examples 1-3, the droplets in the emulsion samples of Examples 1-3 of the present invention and Comparative Example 4 are closely packed and evenly distributed. Among them, the droplet size of Example 1 is smaller and more uniform. The decrease in the average particle size can shorten the distance between oil droplets, increase the interaction between oil droplets, and thus increase the stability of the emulsion.

[0074] Test Example III. 3D printing test

[0075] The emulsion ink materials prepared by Comparative Examples 1-4 and Examples 1-3 were used for 3D printing tests. Each sample to be tested was respectively filled into plastic syringes of the same specification, and cubes were printed at room temperature through a nozzle with an inner diameter of 0.84 mm, the extrusion speed was 5 mm / s, the filling rate was 90%, and the shape was a cube. All printed samples were photographed and recorded. The 3D printing visual appearance diagrams of each emulsion ink material sample are as Figure 3 shown.

[0076] As shown in Figure 3 , all emulsion ink materials can smoothly pass through the printing nozzle. However, there are differences in the accuracy and stability of the cubes formed after printing. The products printed by Comparative Example 1 showed phenomena such as multi-layer fusion, structural collapse, and insufficient self-supporting ability. Adding polysaccharides to the protein solution in Comparative Example 2 can improve the 3D printing properties of the protein emulsion to a certain extent, but the self-supporting ability of the sample is insufficient, and partial collapse still occurs. The texture profile of Comparative Example 3 was significantly improved, indicating that pulsed electric field treatment of the protein enhanced the adsorption of the protein at the oil-water interface, thus better stabilizing the emulsion. The products printed by Comparative Example 4 and Examples 1-3 showed good printing performance. In particular, the cube printed by Example 1 had the most precise geometric shape and recognizable printing texture. Therefore, first using pulsed electric field to treat the protein and then forming a composite solution with polysaccharides realized the cross-linking effect between emulsion droplets, formed a denser three-dimensional network structure, and could enhance the 3D printing properties of the protein emulsion.

[0077] Test Example 4: Measurement of Encapsulation Efficiency of Curcumin

[0078] This test was conducted to measure the encapsulation efficiency of curcumin. The test method was as follows: 0.2 g of the emulsion ink material samples prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were respectively mixed with 2 mL of n-hexane, and then centrifuged at 8000 rpm for 4 min to obtain free curcumin. The absorbance of the obtained supernatant was measured at 450 nm by a microplate reader, and the concentration of curcumin was measured through a standard curve. Encapsulation efficiency (%) = (1 - free curcumin / original curcumin concentration) × 100%. The test results of the encapsulation efficiency are as Figure 4 shown.

[0079] As can be seen from Figure 4 , compared with Comparative Examples 1 to 4, in the present invention, soy protein isolate was first treated by pulsed electric field and then formed a composite solution with polysaccharide as the aqueous phase. The prepared emulsion ink material had a better curcumin encapsulation efficiency (all reaching more than 85%), and among them, the curcumin encapsulation efficiency of Example 1 was the best (reaching 91.8%).

[0080] Test Example 5: Measurement of Freeze-Thaw Stability of Emulsion and Retention Rate of Curcumin

[0081] Test method for the freeze-thaw stability of the emulsion: The emulsion ink materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were respectively filled in 30 mL glass vials, placed at -22 °C for freezing for 24 h, and then taken out and thawed at 25 °C for 4 h. Such a cycle was carried out 3 times to conduct the freeze-thaw test. The mass of the emulsion was weighed before each freeze-thaw and recorded as m 0 (g), and the mass of the emulsion and the centrifuge tube after freeze-thaw was recorded as m 1 (g). The emulsion was centrifuged at 10000 g for 10 min, and after removing the leaked oil, the total mass of the emulsion and the centrifuge tube was recorded as m 2 (g). Oil loss (%) = (m 1 - m 2 ) / m 0 × 100%. The results of the freeze-thaw stability of the emulsion are shown in Table 1.

[0082] Method for measuring the retention rate of curcumin after freeze-thaw of the emulsion: The emulsion ink materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were respectively filled in 30 mL glass vials, placed at -22 °C for freezing for 24 h, and then taken out and thawed at 25 °C for 4 h. Such a cycle was carried out 3 times. Referring to the method in Test Example 4, the retention rate of curcumin in each emulsion sample was measured. The results of the retention rate of curcumin are shown in Table 2.

[0083] Table 1. Oil Loss Rates of Emulsions in Examples 1 to 3 and Comparative Examples 1 to 4 after Multiple Freeze-Thaws

[0084]

[0085] As can be seen from the results in Table 1, when Comparative Example 1 is compared with Comparative Example 2, adding polysaccharides can significantly improve the freeze-thaw stability of high internal phase emulsions. This may be because the freeze-thaw stability of HIPEs is related to the particle size. By comparing the comprehensive results of Examples 1-3 and Comparative Examples 1-4, it shows that the freeze-thaw stability of the high internal phase emulsions prepared by compounding soy protein isolate treated by pulsed electric field with polysaccharide solution is significantly improved. Because pulsed electric field can improve the surface charge of soy protein isolate, which can have a strong electrostatic interaction with the charge of polysaccharides to stabilize the solution, achieving smaller emulsion droplet sizes and minimizing aggregation, thereby improving the freeze-thaw stability.

[0086] Table 2. Curcumin retention rates of the emulsions in Examples 1-3 and Comparative Examples 1-4 after multiple freeze-thaw cycles

[0087]

[0088] As can be seen from the results in Table 2, compared with the emulsion ink materials prepared in Comparative Examples 1-4, the emulsions prepared in Examples 1-3 of the present invention can effectively retain curcumin. After three freeze-thaw cycles, the curcumin retention rate is still as high as 86.32% - 91.63%. Among them, the curcumin retention rate of Example 1 is the best. This may be because in Comparative Examples 1-3, the emulsion oil leakage situation is more serious. After oil leakage, more curcumin is directly in contact with oxygen, resulting in the oxidation and loss of curcumin.

[0089] Based on the above experimental results, it can be known that the high internal phase emulsion ink material prepared by the present invention has high stability after freeze-thaw storage and high retention rate of bioactive substances. It can effectively encapsulate bioactive substances, better achieve the slow release of bioactive components to achieve the purpose of targeted transport, and improve the retention ability of the emulsion for the internal phase substances under freeze-thaw conditions. Therefore, the high internal phase emulsion ink material prepared by the present invention has great application prospects and development potential in the preparation of 3D printing functional foods, and can also provide new technical directions and technical support for 3D printing functional foods.

[0090] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art can use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high internal phase emulsion ink material, characterized in that: The following steps are involved: (1) treating a soy protein isolate solution with a pulse electric field, then adding a polysaccharide solution and stirring and mixing to obtain a protein-polysaccharide composite solution, wherein the protein-polysaccharide composite solution is used as an aqueous phase; and mixing a bioactive substance with a vegetable oil to obtain an oil phase; wherein the polysaccharide used in the polysaccharide solution is one of high methoxy pectin, xanthan gum, and konjac mannan; (2) The water phase and the oil phase are mixed and then sheared at high speed to obtain a high internal phase emulsion ink material.

2. The method for preparing a high internal phase emulsion ink material according to claim 1, characterized in that: In step (1), the process conditions of the pulse electric field treatment are: pulse intensity of 20-40 kV / cm, pulse width of 40-60 μs, pulse frequency of 0.8 kV-1.2 kHz, and flow rate of 8-12 mL / min.

3. The method for preparing a high internal phase emulsion ink material according to claim 1, characterized in that: In step (1), the stirring and mixing speed is 300-500 r / min, and the stirring and mixing time is 1-3 h.

4. The method for preparing a high internal phase emulsion ink material according to claim 1, characterized in that: In step (1), the mass concentration of the soy protein isolate solution is 30-50 mg / mL; the mass concentration of the polysaccharide solution is 15-25 mg / mL; and the mixing volume ratio of the soy protein isolate solution to the polysaccharide solution is (0.8-1.2):(0.8-1.2).

5. The method for preparing a high internal phase emulsion ink material according to any one of claims 1 to 4, characterized in that: In step (1), the bioactive substance is one of curcumin, carotenoids, and astaxanthin; and the mass concentration of the bioactive substance in the oil phase is 0.05% to 0.2%.

6. The method for preparing a high internal phase emulsion ink material according to any one of claims 1 to 4, characterized in that: In step (1), the vegetable oil is one of soybean oil, corn oil and peanut oil.

7. The method for preparing a high internal phase emulsion ink material according to any one of claims 1 to 4, characterized in that: In step (2), the volume ratio of the water phase to the oil phase is 1:(3-5).

8. The method for preparing a high internal phase emulsion ink material according to any one of claims 1 to 4, characterized in that: In step (2), the rotation speed of the high-speed shearing is 10000-12000 r / min, and the time of the high-speed shearing is 3-6 min.

9. A high internal phase emulsion ink material prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the high internal phase emulsion ink material as claimed in claim 9, characterized in that: Application as ink material in 3D printed food.

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