Oxidation-resistant 3D printing ink based on citrus peel and printing method of oxidation-resistant 3D printing ink

Abstract

The embodiment of the invention discloses antioxidant 3D printing ink based on citrus pericarp and a printing method thereof, and the antioxidant 3D printing ink comprises freeze-dried citrus pericarp powder, cocoa butter and other vegetable oil in a ratio of (4-12g): (6-10mL): (0.5-4mL). The printing ink is good in printing forming performance.

Description

Technical Field

[0001] The invention relates to an antioxidant 3D printing ink based on citrus peel and a printing method thereof, belonging to the technical field of 3D printing. Background Art

[0002] As a fruit with the most extensive planting area and the highest yield in the world, citrus occupies a pivotal position in the global agricultural industry. Especially in China, citrus not only occupies a significant advantage in planting area, but also plays an indispensable role in daily consumption. However, in the process of daily consumption of citrus and deep processing, people often only focus on the use of pulp, and discard a large amount of peel as waste. This phenomenon has led to the generation of a huge amount of citrus peel waste, which in turn has caused considerable pressure on the ecological environment. It is worth noting that citrus peels contain rich polyphenol compounds, limonene, geraniol and other natural active substances. These ingredients not only have significant antioxidant properties, but also have strong antibacterial effects. Therefore, how to efficiently and innovatively recycle and reuse these precious peel resources has become an important issue that needs to be solved urgently.

[0003] In recent years, with the rapid development of science and technology, 3D printing technology has been widely used in many fields such as food processing, pharmaceutical manufacturing and materials science, opening up a new direction for the resource and high-value utilization of agricultural waste. However, in the specific application of citrus peels, most of the existing 3D printing technologies use pectin extracted from the peels and mixed with water as the raw material of printing ink. The disadvantage of this method is that the prepared printing ink has poor molding performance, and the extraction process of pectin is relatively complicated, which often leads to a large loss of valuable active ingredients in the peel. In addition, in order to improve the printability of the printing ink, it is usually necessary to add some colloidal additives, and the introduction of these additives may not only weaken the natural edibility of citrus peels, but also have an adverse effect on their health benefits. Therefore, how to explore a new process and technology that is simpler, more natural and can effectively give it good printing characteristics while ensuring that the natural functional components in citrus peels are retained to the maximum extent is still a key problem that needs to be overcome in this field. Summary of the invention

[0004] The present invention provides an antioxidant 3D printing ink based on citrus peel and a printing method thereof, which can effectively solve the above-mentioned problems.

[0005] The present invention is achieved in that:

[0006] An antioxidant 3D printing ink based on citrus peels comprises freeze-dried citrus peel powder, cocoa butter and other vegetable oils in a ratio of 4-12 g: 6-10 mL: 0.5-4 mL.

[0007] In some embodiments, the freeze-dried citrus peel powder is freeze-dried lemon peel powder or freeze-dried orange peel powder.

[0008] In some embodiments, the freeze-drying method of the freeze-dried citrus peel powder is: the citrus peel is chopped and quick-frozen with liquid nitrogen for 2-4 hours, then transferred to -85-75°C for freezing for 24-48 hours, and then freeze-dried for 24-48 hours, ground, and sieved with a 150-300 mesh sieve.

[0009] In some embodiments, the other vegetable oil is selected from at least one of soybean oil, corn oil, sunflower oil, olive oil, and peanut oil.

[0010] A printing method of the antioxidant 3D printing ink based on citrus peels comprises heating cocoa butter in a water bath at 40-65° C. to ensure that it is completely melted, adding freeze-dried citrus peel powder to the cocoa butter, and adding other vegetable oils; mixing them completely and evenly at a speed of 200-600 rpm, then filtering to remove impurities, and loading the obtained printing material into a 3D printing device for printing.

[0011] In some embodiments, the printing temperature of the printing is 33-35°C.

[0012] In some embodiments, the printing speed of the printing is 5-15 mm / s.

[0013] In some embodiments, the printed model has a size of 5-30 mm in length, 5-30 mm in width, and 5-30 mm in height.

[0014] In some embodiments, the printing nozzle diameter is 0.5-2 mm and the layer height is 0.2-1.6 mm.

[0015] A method for printing food.

[0016] The beneficial effects of the present invention are:

[0017] Compared with the printing ink prepared by mixing citrus peel powder with water in the traditional method, the printing ink prepared by mixing citrus powder with vegetable oil proposed in the present invention shows a significant improvement in printing forming performance. This new ink not only shows better stability and film-forming effect during the printing process, but also its application range has been greatly expanded to cover more diverse printing needs. In addition, due to its unique formula and excellent performance, the ink also shows great potential and value in commercial promotion, which can meet the market's growing demand for high-quality printing inks.

[0018] The present invention uses advanced freeze-drying technology to prepare citrus peel powder. This technology can retain the antioxidant active substances in the peel to the greatest extent, ensuring its effectiveness in subsequent applications. At the same time, the present invention innovatively uses a vegetable oil mixed system as a carrier, which not only helps to enhance the antioxidant activity of the citrus peel powder, but also enables it to be better dispersed and stabilized during the printing process. Through this unique combination of technologies, the printed product not only has a good appearance and texture, but is also rich in functional ingredients. It can be promoted and consumed as a functional food, providing consumers with healthy and value-added food options.

[0019] The implementation of the present invention has effectively promoted the resource utilization of discarded citrus peels, transforming the peels that were originally regarded as waste into products with high added value, greatly improving the efficiency of resource utilization. This innovation not only effectively reduces the pollution of the environment by discarded peels, but also provides strong support for environmental protection and sustainable development. Through this resource utilization method, the present invention has opened up a new path for agricultural waste treatment and circular economy development, has important social significance and economic value, and has made positive contributions to building a green and sustainable social environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The printed product image of freeze-dried lemon peel powder printing ink at different printing temperatures in Example 2.

[0022] Figure 2 These are the finished printed images of freeze-dried orange peel powder printing ink at different printing temperatures in Example 3.

[0023] Figure 3The following are the finished printed images of the freeze-dried lemon peel powder printing ink at different printing speeds according to Example 4.

[0024] Figure 4 These are the finished printed images of the freeze-dried orange peel powder printing ink at different printing speeds of Example 5.

[0025] Figure 5 This is a picture of the finished product of printing with different contents of freeze-dried lemon peel powder and different proportions of vegetable oil (soybean oil) printing ink according to Example 6.

[0026] Figure 6 This is a picture of the finished product of the printing ink with different contents of freeze-dried orange peel powder in Example 7.

[0027] Figure 7 This is a printability evaluation graph of the freeze-dried citrus peel powder of Example 8 in combination with cocoa butter or other vegetable oil (soybean oil) alone.

[0028] Figure 8 This is a printed product image of the freeze-dried lemon peel powder and freeze-dried orange peel powder mixed with different vegetable oils in Example 9.

[0029] Fig. 9 This is a diagram showing the antioxidant effect of the citrus peel powder printing ink of Example 10. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0031] The embodiment of the present invention provides an antioxidant 3D printing ink based on citrus peel, which is mainly composed of freeze-dried citrus peel powder, cocoa butter and other vegetable oils, and its specific ratio range is 4-12g freeze-dried citrus peel powder, 6-10mL cocoa butter and 0.5-4mL other vegetable oils. By using direct freeze-drying technology to treat citrus peels, the antioxidant active substances rich in peels, such as vitamin C, flavonoids, etc., can be retained to the maximum extent. Subsequently, a natural plant oil mixed system with antioxidant effects is used as a carrier to effectively dissolve, stabilize and further strengthen these active substances, especially for those oil-soluble components such as limonene, geraniol, etc., which can significantly improve their antioxidant efficacy.

[0032] In addition, the configured vegetable oil mixed system not only has good rheological and temperature-dependent properties, but also can give citrus peel powder excellent 3D printing properties under the conditions of appropriate 3D printing parameters, so that it exhibits good formability and stability during the printing process. This feature not only improves the printability of the ink, but also further expands the application scope of citrus peel powder in the field of 3D printing, such as for the production of functional foods, cosmetics packaging, etc.

[0033] Overall, this invention can retain the antioxidant activity of citrus peels to the greatest extent through scientific and reasonable formula design and process optimization, while significantly improving its 3D printing performance, providing a simple and reliable solution for the efficient utilization of citrus peel waste, with significant environmental and economic benefits.

[0034] In some specific implementation cases, the freeze-dried citrus peel powder mentioned mainly refers to citrus peel powder processed by freeze-drying technology, which may specifically include but not be limited to freeze-dried lemon peel powder or freeze-dried orange peel powder. Both powders are made by freeze-drying fresh lemon peel or orange peel to remove moisture while retaining its original flavor and nutrients, and finally making a fine powder product.

[0035] In some specific implementation cases, the preparation process of the freeze-dried citrus peel powder adopts the following detailed freeze-drying method: first, the fresh citrus peel is carefully chopped to ensure that its size is appropriate for subsequent operations; then, the chopped peels are quickly put into liquid nitrogen for quick freezing, and the quick freezing time is controlled between 2 and 4 hours to ensure that the cell structure inside the peel can be quickly and evenly frozen. Subsequently, the peels that have been quick-frozen by liquid nitrogen are transferred to a freezing environment maintained at a temperature of -85°C to -75°C, and continue to be deep-frozen for a duration of not less than 24 hours but not more than 48 hours to ensure that the moisture in the peel is completely solidified. After the deep freezing is completed, the peel is freeze-dried, and the drying time is also controlled between 24 and 48 hours to completely remove the moisture in the peel and form a dry peel. Finally, the dried peel is finely ground to make it into a fine powder, and the powder is carefully sieved using a sieve with an aperture of 150 to 300 meshes to obtain a uniform and fine freeze-dried citrus peel powder. This direct freeze-drying treatment method can maximize the retention of antioxidant active substances rich in citrus peels, ensuring that their efficacy is not lost in subsequent applications.

[0036] In some specific implementation cases, the other vegetable oils are selected from a variety of vegetable oils, including but not limited to at least one of soybean oil, corn oil, sunflower seed oil, olive oil and peanut oil. These different vegetable oils each have unique physical and chemical properties, which are closely related to the chemical composition and physical state of the vegetable oil itself. It is precisely because of the differences in these physical and chemical properties that they have a significant impact on the rheology of the printing ink in its application. Rheology refers to the flow and deformation ability of ink under different conditions, which is crucial for print quality and the stability of ink. Therefore, selecting the appropriate vegetable oil type plays an important role in optimizing the performance of the printing ink.

[0037] The embodiment of the present invention provides a specific printing method for an antioxidant 3D printing ink based on citrus peel. First, the cocoa butter is placed in a water bath at 40-65°C for heating treatment to ensure that it can be completely melted to a liquid state. Next, the citrus peel powder that has been pre-freeze-dried and ground into powder is gradually added to the melted cocoa butter, and an appropriate amount of other vegetable oils are added as needed to adjust the viscosity and fluidity of the ink. Then, a stirring device is used to fully stir the mixture at a speed of 200-600rpm to ensure that all ingredients can be evenly mixed to form a stable printing ink. After mixing evenly, impurities therein are removed by a filtering device to ensure the purity of the printing material. Finally, the filtered printing material is loaded into the 3D printing device, and the 3D printing operation is performed according to the preset parameters.

[0038] In some specific embodiments, the printing temperature used in the 3D printing process is set to 33-35°C. This temperature range can effectively ensure the fluidity of the printing ink and the stability of the printing molding.

[0039] In some embodiments, the printing speed of the 3D printing is controlled between 5-15 mm / s. This speed range can ensure both printing efficiency and fineness of printing quality.

[0040] In some embodiments, the size specifications of the printed model generated by the 3D printing are: the length range is between 5-30 mm, the width range is between 5-30 mm, and the height range is between 5-30 mm. Such a size range is suitable for the needs of various small antioxidant products.

[0041] In some embodiments, the nozzle diameter used in the 3D printing is set to 0.5-2 mm, and the layer height is controlled between 0.2-1.6 mm. Such nozzle diameter and layer height settings can ensure the fineness of the printing layers and the stability of the overall structure.

[0042] The method provided in the embodiment of the present invention is intended to print out a unique food. The production process of the food includes direct freeze-drying of citrus peels, a step that not only maximizes the natural edibility of the peels, but also effectively retains their inherent health benefits. Through this treatment method, the nutrients and active substances in the peels are fully retained, ensuring the nutritional value and health functions of the food. In addition, the method performs well in printing and molding, and can ensure that the printed food has a stable shape and uniform structure, thereby improving the overall quality and aesthetic appearance of the food. Overall, the present invention not only provides new ideas for food processing, but also brings consumers innovative food choices that are both healthy and delicious.

[0043] Example 1 Preparation of freeze-dried lemon peel powder printing ink and freeze-dried orange peel powder printing ink

[0044] Collect the discarded lemon peel, wash and chop it, and then freeze it in liquid nitrogen for 4 hours, then transfer it to a -80℃ refrigerator for 40 hours. Then, quickly move it to a freeze dryer for freeze drying for 36 hours. After that, grind it at 25,000 rpm for 15 minutes, and sieve the powder through a 200-mesh sieve to ensure that the peel is completely crushed, and finally obtain freeze-dried lemon peel powder. The same method is used to prepare freeze-dried orange peel powder.

[0045] The raw materials were prepared in a ratio of freeze-dried citrus peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:9:1. The cocoa butter was heated in a 55°C water bath to ensure that it was completely melted, and then the prepared freeze-dried ground peel powder and other vegetable oils were added one by one. The mixture was thoroughly mixed at a speed of 500 rpm, and then filtered to remove impurities to obtain freeze-dried lemon peel powder printing ink and freeze-dried orange peel powder printing ink. The ink was placed in a special printing tube and refrigerated for later use.

[0046] Example 2 Evaluation of Printing Temperature of Freeze-dried Lemon Peel Powder Printing Ink

[0047] The freeze-dried lemon peel powder printing ink prepared in Example 1 was used, and different printing parameters were set as follows:

[0048] Printing parameters 1: printing temperature 31°C, printing speed 10mm / s;

[0049] Printing parameters 2: printing temperature 34°C, printing speed 10mm / s;

[0050] Printing parameters 3: printing temperature 37°C, printing speed 10mm / s.

[0051] Take a cube (length: 20mm, width: 20mm, height: 20mm, filling density: 50%) as the printing model, set the nozzle diameter to 1mm, and the layer height to 0.5mm for printing.

[0052] Observe the appearance of each group of printed products, measure their actual sizes in length (X axis), width (Y axis) and height (Z axis), compare these measured values ​​with the target size set by the original model, and calculate the fidelity of each dimension, that is, fidelity = 1-(|measured value-target size| / target size)×100%. Fidelity reflects the degree of deviation between the actual printed size and the target size. The higher the fidelity, the more consistent the printed product is with the original model in terms of morphology, that is, the better the printing accuracy.

[0053] The experimental results are shown in Table 1 and Figure 1 shown.

[0054] Table 1 Printing fidelity of freeze-dried lemon peel powder printing ink at different printing temperatures

[0055]

[0056]

[0057] Note: a. There is a statistical difference compared with the 31℃ printing group, P<0.05; b. There is a statistical difference compared with the 34℃ printing group, P<0.05.

[0058] Since citrus peel powder does not have temperature variation, the melting point of freeze-dried citrus peel powder printing ink is mainly determined by the temperature variation characteristics of the vegetable oil mixture system. In order to explore the optimal printing temperature of the printing ink, we selected three temperatures of 31°C, 34°C, and 37°C, and conducted a cube printing experiment after heating the printing ink for the same time.

[0059] Figure 1 The results show that when the printing temperature is low (31°C, 34°C), the internal support of the printed products of freeze-dried lemon peel powder printing ink is better. This may be because at low temperatures, the melting degree of lemon peel printing ink is lower and it is closer to a semi-solid state, so the required curing time after stacking is shorter and the support is higher. When the printing temperature is higher (37°C), the lemon peel powder printing ink exists more in the form of fluid and requires a longer curing time, resulting in insufficient support in the middle stacking part, and the higher the layer height, the easier it is to collapse.

[0060] From the quantitative fidelity data (Table 1), at a printing temperature of 37°C, the Y-axis fidelity of the printed product of lemon peel powder printing ink is significantly lower than that at 31°C and 34°C, and the difference is statistically significant (P<0.05); in terms of Z-axis fidelity, the printed product at a printing temperature of 34°C is significantly better than that at 31°C and 37°C, and the difference is also statistically significant (P<0.05). In general, 34°C is the best printing temperature for freeze-dried lemon peel powder printing ink. At this temperature, the ink has moderate fluidity and support, and the printing accuracy of the X, Y, and Z axes is high.

[0061] Example 3 Evaluation of Printing Temperature of Freeze-dried Orange Peel Powder Printing Ink

[0062] The freeze-dried orange peel powder prepared in Example 1 was used for printing ink, and other operations were the same as in Example 2. The experimental results are shown in Tables 2 and Figure 2 shown.

[0063] Table 2 Printing fidelity of freeze-dried orange peel powder printing ink at different printing temperatures

[0064]

[0065] Note: a. There is a statistical difference compared with the 31℃ printing group, P<0.05; b. There is a statistical difference compared with the 34℃ printing group, P<0.05.

[0066] In the study of the printing temperature of freeze-dried orange peel powder printing ink, we found that when the printing temperature is too low (31°C), the orange peel powder printing ink is not completely melted, and the wire is prone to breakage during the printing process; when the printing temperature is too high (37°C), the ink melts too much, resulting in excessive liquid discharge during the printing process and uneven edges of the finished product ( Figure 2 ). Obviously, the finished product appearance is most ideal at a printing temperature of 34°C ( Figure 2 ). The quantitative fidelity data (Table 2) also showed that at a printing temperature of 34°C, the fidelity of the finished product of orange peel powder printing ink was significantly better than that of 31°C and 37°C in the Y-axis, and the fidelity of the Z-axis was significantly better than that of 31°C, and the differences were statistically significant (P<0.05). In summary, 34°C is the best printing temperature for freeze-dried orange peel powder printing ink, and it performs well in terms of the integrity and neatness of the finished product, as well as the printing accuracy of the X, Y, and Z axes.

[0067] Since food 3D printing mostly uses extrusion stacking printing and needs to undergo a qualitative change from non-Newtonian fluid to solid, the speed of printing will also affect the quality and accuracy of the printed product. Therefore, in subsequent experiments, we investigated the effect of different printing speeds on the printing state of citrus peel powder printing ink.

[0068] Example 4 Evaluation of Printing Speed ​​of Freeze-dried Lemon Peel Powder Printing Ink

[0069] Set the printing parameters as follows:

[0070] Printing parameters 1: Printing temperature 34°C, printing speed 10mm / s;

[0071] Printing parameters 2: printing temperature 34°C, printing speed 20mm / s;

[0072] Printing parameters 3: printing temperature 34°C, printing speed 40 mm / s.

[0073] Other operations are the same as in Example 2. The experimental results are shown in Table 3 and Figure 3 shown.

[0074] Table 3 Printing fidelity of freeze-dried lemon peel powder printing ink at different printing speeds

[0075]

[0076] Note: a. There is a statistical difference compared with the 10mm / s printing group, P<0.05

[0077] from Figure 3 It can be seen that the printing speed has a significant effect on the printing effect of freeze-dried lemon peel powder printing ink. As the printing speed increases, the collapse phenomenon in the middle of the printed product becomes more serious, and it is even difficult to form (40mm / s). The quantitative fidelity data (Table 3) show that when the printing speed is 10mm / s, the fidelity of the finished product of freeze-dried lemon peel powder printing ink on the Z axis is better than 20mm / s and 40mm / s, and the difference is statistically significant (P<0.05). At a printing speed of 10mm / s, the freeze-dried lemon peel powder printing ink has enough time to solidify, so that the support and integrity of the printed product are better, and the printing accuracy is also higher.

[0078] Example 5 Evaluation of Printing Speed ​​of Freeze-dried Orange Peel Powder Printing Ink

[0079] The freeze-dried orange peel powder prepared in Example 1 was used to print ink, and other operations were the same as in Example 4. The experimental results are shown in Tables 4 and Figure 4 shown.

[0080] Table 4 Printing fidelity of freeze-dried orange peel powder printing ink at different printing speeds

[0081]

[0082] Note: a. There is a statistical difference compared with the 10mm / s printing group, P<0.05; b. There is a statistical difference compared with the 20mm / s printing group, P<0.05

[0083] Likewise, for freeze-dried orange peel powder printing ink, printing speed has a significant impact on the integrity of the printed product. Figure 4 The results show that as the printing speed increases, the collapse in the middle of the printed product becomes more serious, especially when the printing speed reaches 40mm / s. At this time, the fidelity of the Y-axis and Z-axis is significantly lower than when the printing speed is 10mm / s and 20mm / s, and the difference is statistically significant (P<0.05) (see Table 4). Comprehensive analysis shows that when the printing speed is 10mm / s, the printed product of the freeze-dried orange peel powder printing ink shows higher integrity and accuracy.

[0084] Example 6 Evaluation of the printability of freeze-dried lemon peel powder ink

[0085] Taking freeze-dried lemon peel powder as an example, different raw material ratios are set as follows.

[0086] Control group 1: freeze-dried lemon peel powder (g): water (mL) = 4:10

[0087] Control group 2: freeze-dried lemon peel powder (g): water (mL) = 8:10

[0088] Experimental group 1: freeze-dried lemon peel powder (g): cocoa butter (mL): soybean oil (mL) = 4:9:1

[0089] Experimental group 2: freeze-dried lemon peel powder (g): cocoa butter (mL): soybean oil (mL) = 4:8:2

[0090] Experimental group 3: freeze-dried lemon peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:9:1

[0091] Experimental group 4: freeze-dried lemon peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:8:2

[0092] Printing inks were prepared according to the inventive method.

[0093] A cube (length: 20 mm, width: 20 mm, height: 20 mm, filling density: 50%) was used as the printing model, and the model was printed under the parameters of nozzle diameter of 1 mm, layer height of 0.5 mm, nozzle temperature of 34°C, and printing speed of 10 mm / s.

[0094] Observe the appearance of each group of printed products, measure their actual sizes in length (X axis), width (Y axis) and height (Z axis), compare these measured values ​​with the target size set by the original model, and calculate the fidelity of each dimension, that is, fidelity = 1-(|measured value-target size| / target size)×100%. Fidelity reflects the degree of deviation between the actual printed size and the target size. The higher the fidelity, the more consistent the printed product is with the original model in terms of morphology, that is, the better the printing accuracy.

[0095] The experimental results are shown in Table 5 and Figure 5 shown.

[0096] Table 5 Printing fidelity of freeze-dried lemon peel powder with different contents and vegetable oil printing ink with different proportions

[0097]

[0098] Note: a. There is a statistical difference with the group with lemon peel powder content of 0.8g / mL and cocoa butter: soybean oil = 9:1, P < 0.05

[0099] Figure 5 The results showed that the combination of freeze-dried lemon peel powder and water was in a solid state and could not be printed. The possible reason is that the cellulose content in lemon peel powder is high and its solubility in water is poor. In contrast, the invented freeze-dried lemon peel powder printing ink showed certain printing performance in each test formula. With the increase of lemon peel powder content and the proportion of soybean oil in the vegetable oil system, the printed products showed higher model stability and better formability. The fidelity test results (Table 5) further confirmed that when the freeze-dried lemon peel powder content was 0.8 g / mL and the cocoa butter / soybean oil ratio was 9:1, the freeze-dried lemon peel powder printing ink showed excellent printing effects, and the fidelity of each axis of the finished product was close to 100%, among which the Z axis had the highest fidelity, and the difference was statistically significant compared with other groups (P<0.05).

[0100] Example 7 Printability Evaluation of Freeze-dried Orange Peel Powder Ink

[0101] Taking freeze-dried orange peel powder as an example, different raw material ratios are set as follows.

[0102] Control group 1: freeze-dried orange peel powder (g): water (mL) = 4:10

[0103] Experimental group 1: freeze-dried orange peel powder (g): cocoa butter (mL): soybean oil (mL) = 4:9:1

[0104] Experimental group 2: freeze-dried orange peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:9:1

[0105] Experimental group 3: freeze-dried orange peel powder (g): cocoa butter (mL): soybean oil (mL) = 12:9:1

[0106] Printing inks were prepared according to the inventive method.

[0107] A cube (length: 20 mm, width: 20 mm, height: 20 mm, filling density: 50%) was used as the printing model, and the model was printed under the parameters of nozzle diameter of 1 mm, layer height of 0.5 mm, nozzle temperature of 34°C, and printing speed of 10 mm / s.

[0108] Observe the appearance of each group of printed products, measure their actual sizes in length (X axis), width (Y axis) and height (Z axis), compare these measured values ​​with the target size set by the original model, and calculate the fidelity of each dimension, that is, fidelity = 1-(|measured value-target size| / target size)×100%. Fidelity reflects the degree of deviation between the actual printed size and the target size. The higher the fidelity, the more consistent the printed product is with the original model in terms of morphology, that is, the better the printing accuracy.

[0109] The experimental results are shown in Table 6 and Figure 6 shown.

[0110] Table 6 Printing fidelity of printing inks with different contents of freeze-dried orange peel powder

[0111]

[0112] Note: a. There is a statistical difference with the group with orange peel powder content of 0.4g / mL, P<0.05; b. There is a statistical difference with the group with orange peel powder content of 0.8g / mL, P<0.05

[0113] Figure 6The results showed that the printing ink composed of freeze-dried orange peel powder and water had certain printing performance, but the support of its printed product was poor, and obvious deformation and collapse occurred. In contrast, the invented freeze-dried orange peel powder printing ink showed good printing formability under different orange peel powder content conditions. In particular, when the freeze-dried orange peel powder content was 0.8g / mL, the effect of the printing ink was most ideal, and the fidelity of its printed product on the X-axis and Y-axis was significantly better than that of 0.4g / mL and 1.2g / mL, and the difference was statistically significant (P<0.05) (see Table 6). The possible reason for this phenomenon is that the appropriate proportion of freeze-dried orange peel powder effectively improves the uniformity of the printing ink and ensures the smoothness and balance of the liquid output.

[0114] Example 8 Printability Evaluation of Freeze-dried Citrus Peel Powder and Single Vegetable Oil System

[0115] Experimental group 1: freeze-dried lemon peel powder (g): cocoa butter (mL) = 8:10

[0116] Experimental group 2: freeze-dried lemon peel powder (g): soybean oil (mL) = 8:10

[0117] Experimental group 3: freeze-dried orange peel powder (g): cocoa butter (mL) = 8:10

[0118] Experimental group 4: freeze-dried orange peel powder (g): soybean oil (mL) = 8:10

[0119] According to the specific methods and steps described in Example 1, the printing ink required for each group was carefully prepared. In order to ensure the accuracy and comparability of the experiment, a standardized cube model was selected as the printing object. The size of the model was 20 mm long, 20 mm wide, and 20 mm high, and the filling density was set to 50%. During the printing process, various parameters were strictly controlled, including the nozzle diameter being set to 1 mm, the layer height being 0.5 mm, the nozzle temperature being maintained at 34 ° C, and the printing speed being maintained at 10 mm / s. Through these fine parameter settings, the stability and consistency of the printing process were ensured.

[0120] After printing, the appearance of each group of printed products was carefully observed and analyzed. Figure 7 As shown in the figure, it can be clearly seen through comparative analysis that when freeze-dried lemon peel powder or freeze-dried orange peel powder is combined with cocoa butter alone, the integrity of the printed product is poor, which is specifically manifested in large-scale dislocation and structural disorder. This phenomenon may be due to the relatively fast solidification speed of cocoa butter, which leads to discontinuous ink discharge in the later stage of printing and even nozzle clogging. These factors work together to seriously affect the molding effect of the printed product.

[0121] When freeze-dried lemon peel powder or freeze-dried orange peel powder is combined with soybean oil alone, although the fluidity of the system is good, due to the lack of sufficient support, the printed product appears to be in a fluid state and does not have the required printing performance. This result shows that a single vegetable oil as a carrier is difficult to meet the comprehensive requirements of 3D printing for ink performance.

[0122] Obviously, the printing ink used in the present invention needs to reasonably combine freeze-dried citrus peel powder with cocoa butter and other vegetable oils to give full play to its excellent printability. In this composite system, the ink not only has suitable temperature-variability and can maintain stable performance at different temperatures, but also has good fluidity to ensure the smooth progress of the printing process. It is difficult to achieve an ideal 3D printing effect by relying solely on a single vegetable oil as a carrier. This discovery provides an important experimental basis for the further optimization and application of the present invention.

[0123] Example 9 Evaluation of the printability of freeze-dried citrus peel powder mixed with different vegetable oils

[0124] In addition to soybean oil, we also further investigated the actual printability of citrus peel powder inks prepared from a variety of natural vegetable oils such as corn oil, sunflower oil, and olive oil with cocoa butter. In order to systematically study and compare the effects of different vegetable oils on the printing effect of inks, we designed specific experimental groups, as described in detail below.

[0125] Experimental group 1: freeze-dried lemon peel powder (unit: g) was mixed with cocoa butter (unit: mL) and corn oil (unit: mL) in a specific ratio of 8:9:1.

[0126] Experimental group 2: freeze-dried lemon peel powder (unit: g) was also used, but it was mixed with cocoa butter (unit: mL) and sunflower seed oil (unit: mL) in the same ratio of 8:9:1.

[0127] Experimental group 3: Freeze-dried lemon peel powder (unit: g) was continued to be used, this time mixed with cocoa butter (unit: mL) and olive oil (unit: mL) in a ratio of 8:9:1.

[0128] Experimental group 4: freeze-dried orange peel powder (unit: g) was used and mixed with cocoa butter (unit: mL) and corn oil (unit: mL) in a ratio of 8:9:1.

[0129] Experimental Group 5: Freeze-dried orange peel powder (unit: g) was still used, but it was mixed with cocoa butter (unit: mL) and sunflower seed oil (unit: mL) in a ratio of 8:9:1.

[0130] Experimental Group 6: Freeze-dried orange peel powder (unit: g) was continued to be used, and this time it was mixed with cocoa butter (unit: mL) and olive oil (unit: mL) in a ratio of 8:9:1.

[0131] All experimental groups prepared the printing ink according to the method described in Example 1. In order to ensure the accuracy and comparability of the experimental results, we selected a unified printing model - a cube (specific dimensions: 20mm long, 20mm wide, 20mm high, and the filling density was set to 50%) for 3D printing. During the printing process, the nozzle diameter was set to 1mm, the layer height was 0.5mm, the nozzle temperature was controlled at 34℃, and the printing speed was set to 10mm / s. After the printing was completed, we carefully observed and analyzed the appearance of the printed products of each group.

[0132] The experimental results are as follows Figure 8 As shown, Figure 8 The data and images clearly show that freeze-dried lemon peel powder or freeze-dried orange peel powder inks prepared from three different vegetable oil mixed systems (i.e., a mixed system of cocoa butter and corn oil, a mixed system of cocoa butter and sunflower oil, and a mixed system of cocoa butter and olive oil) all show good 3D printing effects. Specifically, the finished product printed with the ink prepared from the cocoa butter and olive oil system has an exceptionally smooth surface, clear and even lines, and the overall printing effect is the most ideal; in contrast, the finished product printed with the ink prepared from the cocoa butter and corn oil system has slightly rough lines, uneven edges, and a relatively inferior printing effect; and the printing performance of the ink prepared from the cocoa butter and sunflower oil system is between the corn oil system and the olive oil system.

[0133] These significant differences are likely closely related to the physical and chemical properties of different vegetable oils, which directly affect the rheological properties of the printing ink, resulting in differences in printing effects. Overall, by adjusting and optimizing the vegetable oil mixing system, the citrus peel powder ink we prepared can still maintain good printability, which fully proves that the present invention has strong applicability and broad potential application prospects.

[0134] Example 10 Evaluation of the Antioxidant Properties of 3D Printing Inks

[0135] In order to comprehensively evaluate the antioxidant properties of lemon peel powder printing ink, we divided the experimental materials into the following different control groups and experimental groups. The specific groupings are as follows:

[0136] Control group 1: lemon peel powder prepared by conventional method was used as the basic reference sample.

[0137] Control group 2: lemon peel powder treated with freeze-drying technology, aimed at investigating the effect of freeze-drying process on antioxidant activity.

[0138] Control group 3: freeze-dried lemon peel powder was mixed with water in a specific ratio of freeze-dried lemon peel powder (g): water (mL) = 8:10 to evaluate the effect of water on antioxidant activity.

[0139] Experimental group 1: freeze-dried lemon peel powder was mixed with cocoa butter and soybean oil in a specific ratio of freeze-dried lemon peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:9:1, in order to explore the synergistic effect of vegetable oils on antioxidant activity.

[0140] Similarly, a similar group design was used to evaluate the antioxidant activity of orange peel powder printing ink, as follows:

[0141] Control group 1: Orange peel powder prepared by conventional method was used as the basic reference sample.

[0142] Control group 2: Orange peel powder treated with freeze-drying technology, aimed at investigating the effect of freeze-drying process on antioxidant activity.

[0143] Control group 3: freeze-dried orange peel powder was mixed with water in a specific ratio of freeze-dried orange peel powder (g): water (mL) = 8:10, in order to evaluate the effect of water on antioxidant activity.

[0144] Experimental group 1: Freeze-dried orange peel powder was mixed with cocoa butter and soybean oil in a specific ratio of freeze-dried orange peel powder (g): cocoa butter (mL): soybean oil (mL) = 8:9:1, in order to explore the synergistic effect of vegetable oils on antioxidant activity.

[0145] According to the method described in detail in Example 1, we prepared the above-mentioned groups of materials into corresponding printing inks, and used DPPH free radical scavenging method and total antioxidant capacity (T-AOC) detection methods to evaluate their antioxidant properties. DPPH is a stable purple nitrogen free radical molecule. When antioxidant substances react with it, it can be reduced to colorless or light yellow. The degree of color change is proportional to the antioxidant capacity, thereby intuitively reflecting the antioxidant effect. The T-AOC rule is a comprehensive evaluation method for examining the overall antioxidant capacity of a substance, and is particularly suitable for comparing the total oxidative capacity of different foods or formulas. By combining these two methods, we can comprehensively evaluate the antioxidant properties of citrus peel printing inks from two aspects: single antioxidant activity and overall antioxidant capacity.

[0146] The experimental results are as follows Fig. 9 shown. Fig. 9The data analysis results show that compared with lemon peel powder or orange peel powder prepared by conventional drying and grinding, pure lemon peel powder or orange peel powder prepared by freeze-drying showed significant advantages in antioxidant effect, and could more effectively scavenge DPPH free radicals and inhibit oxidation reactions. This difference was statistically significant (P<0.05). Traditional methods for preparing citrus peel powder usually involve heating and other mechanical operations, which may have a destructive effect on the active substances in the peel, especially the antioxidant components, resulting in a decrease in its antioxidant capacity. The freeze-drying method maximizes the protection of the antioxidant components in the peel by drying under low temperature conditions, so the prepared peel powder has stronger antioxidant capacity.

[0147] However, when these freeze-dried peel powders are mixed with water, due to the poor solubility and stability of the antioxidant components in the citrus peel powder in water, some active substances may be degraded or cannot be fully released, resulting in a significant weakening of its antioxidant capacity, and the DPPH scavenging rate and T-AOC are significantly reduced. Compared with the control group (pure freeze-dried powder), this difference is statistically significant (P<0.05). In contrast, the freeze-dried citrus peel powder printing ink invented by us showed stronger antioxidant capacity than the control group (pure freeze-dried powder). It can not only further scavenge more DPPH free radicals, but also significantly improve T-AOC. This difference is also statistically significant (P<0.05). This phenomenon may be related to the addition of vegetable oil, which not only improves the dispersibility and stability of the active substances in the peel powder, but also enhances the overall antioxidant effect because the vegetable oil itself has a certain antioxidant effect.

[0148] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An antioxidant 3D printing ink based on citrus peel, characterized in that: It includes freeze-dried citrus peel powder, cocoa butter and other vegetable oils, and the ratio is 4-12g:6-10mL:0.5-4mL.

2. The antioxidant 3D printing ink based on citrus peel according to claim 1, characterized in that: The freeze-dried citrus peel powder is freeze-dried lemon peel powder or freeze-dried orange peel powder.

3. The antioxidant 3D printing ink based on citrus peel according to claim 1, characterized in that: The freeze-drying method of the freeze-dried citrus peel powder is as follows: the citrus peel is chopped and then quickly frozen with liquid nitrogen for 2-4 hours, then transferred to -85--75°C for freezing for 24-48 hours, then freeze-dried for 24-48 hours, ground, and the powder is sieved using a 150-300 mesh sieve.

4. The antioxidant 3D printing ink based on citrus peel according to claim 1, characterized in that: The other vegetable oil is selected from at least one of soybean oil, corn oil, sunflower oil, olive oil and peanut oil.

5. A printing method of the antioxidant 3D printing ink based on citrus peel according to any one of claims 1 to 4, characterized in that: Heat the cocoa butter in a water bath at 40-65°C to ensure that it is completely melted, add the freeze-dried citrus peel powder to the cocoa butter, and add other vegetable oils; mix them thoroughly at a speed of 200-600rpm, then filter to remove impurities, and load the obtained printing material into the 3D printing equipment for printing.

6. The printing method according to claim 5, characterized in that: The printing temperature of the printing is 33-35°C.

7. The printing method according to claim 5, characterized in that: The printing speed of the printing is 5-15 mm / s.

8. The printing method according to claim 5, characterized in that: The printed model has a size of 5-30 mm in length, 5-30 mm in width, and 5-30 mm in height.

9. The printing method according to claim 5, characterized in that: The printing nozzle diameter is 0.5-2 mm, and the layer height is 0.2-1.6 mm.

10. A food printed by the method according to any one of claims 5 to 9.

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