A 3D printing ink for food and its preparation method

Abstract

The present invention relates to the field of food 3D printing, and discloses a food 3D printing ink and a preparation method thereof, comprising the following steps: soaking fish skin in a citric acid solution, washing with water, stirring, filtering and drying to obtain fish glue; adjusting the pH of the obtained fish glue to 7.5-8.5, mixing with an alkaline enzyme, and then dividing it into two parts, one part is microwave-treated for 10-15 min, and the other part is microwave-treated for 20-25 min. After microwave treatment, enzyme inactivation is carried out respectively, and then the supernatant is taken after centrifugation and freeze-dried to obtain fish gelatin hydrolysate; dissolving the fish gelatin hydrolysate and starch in water and allowing it to form a gel at room temperature. The present invention uses fish skin as a raw material, utilizes microwave processing to prepare fish gelatin hydrolysate, and after interacting with starch, a food 3D printing ink with high printing accuracy can be obtained, realizing the utilization of fish processing by-products.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D food printing, and in particular to a food 3D printing ink and a preparation method thereof. Background Art

[0002] Fish processing by-products are fish materials left over from primary processing during the fish production process. By weight, the proportion of these by-products is about 50wt% of the raw materials. Due to the high organic matter content, fish processing by-products are classified as certified waste and have higher treatment costs. This increases the waste treatment cost without value-added solutions.

[0003] 3D printing of food-grade materials provides novel and customized cooking products. A variety of edible materials can be used for 3D printing to create complex food structures. Carbohydrate-based materials are popular in this regard. However, there are some challenges in carbohydrate 3D printing, such as limited structural integrity, susceptibility to moisture absorption, and lack of nutritional value. Some researchers have proposed that mixing carbohydrates and proteins may be a solution. Approximately 50% (w / w) of the dry weight of seafood waste is protein. Therefore, applying fish processing by-products to the field of 3D food printing is beneficial to the development of the seafood industry.

[0004] In the prior art, there are studies on using surimi as a 3D printing material. For example, a preparation method and application of a surimi material for 3D printing disclosed in the patent with publication number CN109077256A uses fish meat as the main raw material and obtains a surimi material that can be used for 3D printing through five steps: raw material pretreatment, meat grinding, rinsing, dehydration, and surimi preparation. However, there is currently no research on how to use fish processing by-products to prepare an ink suitable for 3D printing. Summary of the Invention

[0005] The present invention is to overcome the above problems existing in the prior art, and provides a food 3D printing ink and a preparation method thereof. Using fish skin as the raw material, fish gelatin hydrolysate is prepared by microwave processing. After interacting with starch, a food 3D printing ink with high printing accuracy can be obtained, realizing the utilization of fish processing by-products.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a food 3D printing ink, comprising the following steps:

[0008] (1) Soak fish skin in a citric acid solution, wash it with water, stir, filter, and dry to obtain fish glue;

[0009] (2) Adjust the pH value of the obtained fish glue to 7.5 - 8.5, mix it with an alkaline enzyme, and then divide it into two parts. One part is microwave-treated for 10 - 15 min, and the other part is microwave-treated for 20 - 25 min. The microwave power during the treatment is 50 - 100 W; after microwave treatment, enzyme inactivation is carried out respectively, and then the supernatant is taken after centrifugation and freeze-dried to obtain fish gelatin hydrolysate;

[0010] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 40:60 - 60:40, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 - 15 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 - 25 min is 1:5 - 10.

[0011] The utilization of fish protein in fish processing by-products is crucial. Among different types of fish proteins, the extraction of fish gelatin from fish skin has attracted wide attention and is considered an important source of gelatin in addition to mammalian gelatin. Fish gelatin hydrolysate makes it easier for the body to absorb and digest amino acids, and its texture and better water solubility enable it to be more simply combined with daily diets. The present invention uses fish skin as a raw material to prepare fish glue, and then uses a microwave processing method to obtain fish gelatin hydrolysate. The treated fish gelatin hydrolysate combined with different proportions of starch can be used as 3D printing ink, deeply exploring the production of value-added from fish processing by-products, improving the economic value of fish processing by-products, being environmentally friendly, alleviating the problem of increasing costs for dealing with fish processing by-products, and also providing a new food-grade material for 3D printing.

[0012] The gel made only of starch has poor stability. In the present invention, the fish gelatin hydrolysate is combined with starch as 3D printing ink. The fish gelatin hydrolysate exhibits strong water-holding capacity. This enhanced water-retaining capacity inhibits the movement of water and provides a better solid gel structure with reduced viscosity; the interaction between carbohydrates and proteins can solve the disadvantages of limited structural integrity, water sensitivity, and lack of nutritional value of carbohydrates for 3D printing.

[0013] Meanwhile, the present invention utilizes microwave processing to prepare fish gelatin hydrolysates, which is more efficient compared to traditional hydrolysis methods. Since fish gelatin hydrolysates with different degrees of hydrolysis form gel networks with different structures when combined with starch, and the structure of the gel network affects the printing accuracy of 3D printing inks. An ideal 3D printing ink should have a balance of high storage elastic energy capacity and moderate viscosity (a high storage elastic energy capacity not only helps prevent excessive deformation or sagging of the printed structure during printing, but also enables a faster printing speed as the material can quickly recover its shape after extrusion; a certain viscosity of the 3D printing ink helps achieve better layer adhesion and smooth deposition of the ink, contributing to improved overall printing quality, but too high a viscosity makes it difficult to extrude through the nozzle of a 3D printer), facilitating layer-by-layer printing. Therefore, to ensure that the 3D printing ink has good printing performance, the present invention controls the degree of hydrolysis of fish gelatin by controlling the time of microwave treatment, mixes two fish gelatin hydrolysates with different degrees of hydrolysis, reacts with starch, so that the resulting gel structure can have both a high storage modulus (reflecting the ability of the material to store elastic energy) and a moderate loss modulus (related to the viscosity of the material), thereby obtaining a food 3D printing ink with high printing accuracy.

[0014] Preferably, the fish skin in step (1) is from lungfish.

[0015] Preferably, in step (1), the mass concentration of the citric acid solution is 0.2 - 0.3%, the mass-to-volume ratio of fish skin to the citric acid solution is 1g:3 - 5mL, and the soaking time of the fish skin in the citric acid solution is 12 - 24h.

[0016] Preferably, in step (1), the temperature during stirring is 60 - 70°C, and the stirring time is 6 - 8h.

[0017] Preferably, in step (1), the temperature during drying is 55 - 65°C, and the drying time is 40 - 60min.

[0018] Preferably, in step (2), the alkaline enzyme is alkaline protease; the volume fraction of the added alkaline enzyme is 1 - 3%.

[0019] Preferably, in step (2), the temperature during microwave treatment is 50 - 60°C.

[0020] Preferably, in step (2), the temperature for enzyme inactivation is -20 - -25°C, and the enzyme inactivation time is 5 - 10min.

[0021] Preferably, in step (2), the temperature during centrifugation is 0 - 4°C, the centrifugal force is 9000 - 11000×g, and the time is 10 - 20min.

[0022] Preferably, in step (3), the total mass of the fish gelatin hydrolyzate and the starch and the volume of water are in a ratio of 7-8 g:50 mL.

[0023] The present invention also provides a food 3D printing ink prepared by the above preparation method.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] (1) Using fish skin as the raw material, deeply exploring the production of value-added from fish processing by-products, improving the economic value of fish processing by-products, being environmentally friendly, and alleviating the problem of increasing costs for treating fish processing by-products;

[0026] (2) Combining the fish gelatin hydrolyzate with starch as the 3D printing ink, the interaction between carbohydrates and proteins can solve the disadvantages of limited 3D structural integrity of carbohydrates, being sensitive to moisture, and lacking nutritional value;

[0027] (3) Using the microwave processing method to prepare the fish gelatin hydrolyzate. Compared with traditional hydrolysis, microwave processing improves the efficiency of enzyme hydrolysis of fish skin gelatin while ensuring nutrition;

[0028] (4) Mixing two fish gelatin hydrolyzates with different degrees of hydrolysis and acting with starch, so that the obtained gel structure can have both high storage elastic energy and appropriate viscosity, thereby obtaining a food 3D printing ink with high printing accuracy. Description of the Drawings

[0029] Figure 1 It is the SEM image of the fish gelatin hydrolyzate in Example 1 of the present invention; where a is the untreated fish glue; b is the fish glue after microwave treatment for 10 min; c is the fish glue after microwave treatment for 20 min.

[0030] Figure 2 It is the physical image of the 3D printing ink of the present invention; where a is Comparative Example 1, b is Comparative Example 2, c is Example 1, d is Example 2, and e is Comparative Example 3.

[0031] Figure 3 It is the SEM image of the 3D printing ink of the present invention; where a is Comparative Example 1, b is Comparative Example 2, c is Example 1, d is Example 2, and e is Comparative Example 3.

[0032] Figure 4 It is the viscosity curve of the 3D printing ink of the present invention.

[0033] Figure 5 It is the relationship curve between the storage modulus and the angular frequency of the 3D printing ink of Example 1 and Comparative Examples 4 and 5 of the present invention.

[0034] Figure 6 It is the relationship curve between the loss modulus and the angular frequency of the 3D printing inks of Example 1 and Comparative Examples 4 and 5 of the present invention.

[0035] Figure 7 It is a physical picture of the product printed with the 3D printing ink in Example 1 of the present invention.

[0036] Figure 8 It is a physical picture of the product printed with the 3D printing ink in Comparative Example 4 of the present invention.

[0037] Figure 9 It is a physical picture of the product printed with the 3D printing ink in Comparative Example 5 of the present invention. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings and detailed implementation manners.

[0039] In the present invention, unless otherwise specified, all devices and raw materials can be purchased from the market or are commonly used in this industry. The methods in the following examples are conventional methods in this field unless otherwise specified.

[0040] General example:

[0041] A preparation method of a food 3D printing ink, comprising the following steps:

[0042] (1) Soak fish skin in a citric acid solution, wash it with water, stir, filter, and dry to obtain fish glue;

[0043] (2) Adjust the pH value of the obtained fish glue to 7.5 - 8.5, mix it with an alkaline enzyme, and then divide it into two parts. One part is microwave-treated for 10 - 15 min, and the other part is microwave-treated for 20 - 25 min. The microwave power during treatment is 50 - 100 W; after microwave treatment, enzyme inactivation is carried out respectively, and then the supernatant is taken after centrifugation and freeze-dried to obtain fish gelatin hydrolysate;

[0044] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 40:60 - 60:40, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 - 15 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 - 25 min is 1:5 - 10.

[0045] As a specific implementation manner, the fish skin in step (1) comes from lungfish.

[0046] As a specific implementation manner, the mass concentration of the citric acid solution in step (1) is 0.2 - 0.3%, the mass-volume ratio of the fish skin to the citric acid solution is 1 g:3 - 5 mL, and the soaking time of the fish skin in the citric acid solution is 12 - 24 h.

[0047] As a specific embodiment, the temperature during stirring in step (1) is 60 - 70°C, and the stirring time is 6 - 8 h.

[0048] As a specific embodiment, the temperature during drying in step (1) is 55 - 65°C, and the drying time is 40 - 60 min.

[0049] As a specific embodiment, the alkaline enzyme in step (2) is alkaline protease; the volume fraction of the added alkaline enzyme is 1 - 3%.

[0050] As a specific embodiment, the temperature during microwave treatment in step (2) is 50 - 60°C.

[0051] As a specific embodiment, the temperature for enzyme inactivation in step (2) is -20 - -25°C, and the time for enzyme inactivation is 5 - 10 min.

[0052] As a specific embodiment, the temperature during centrifugation in step (2) is 0 - 4°C, the centrifugal force is 9000 - 11000×g, and the time is 10 - 20 min.

[0053] As a specific embodiment, the mass ratio of the total of fish gelatin hydrolysate and starch to the volume of water in step (3) is 7 - 8 g:50 mL.

[0054] Example 1:

[0055] A method for preparing a food 3D printing ink, comprising the following steps:

[0056] (1) Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass - volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, stir vigorously at 65°C with a volume ratio of distilled water to citric acid solution of 1:1 for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60°C for 50 min to obtain fish glue.

[0057] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is treated by microwave for 10 min, and the other part is treated by microwave for 20 min, the microwave power during treatment is 60 W, and the temperature is 55°C; after microwave treatment, inactivate the enzyme at -20°C for 5 min, then centrifuge at 10000×g and 4°C for 15 min, take the supernatant, and obtain fish gelatin hydrolysate after freeze - drying.

[0058] The degree of hydrolysis (DH) of the obtained gelatin hydrolysate was determined by the following method: Dissolve 1.5 g of freeze-dried fish gelatin hydrolysate in deionized water to a volume of 50 mL; adjust the pH of the solution to 7.0 with 0.1 mol / L sodium hydroxide, add 10 mL of 38% (v / v) formaldehyde, and store at room temperature (25 °C) for 5 min; titrate at pH 8.5 with standard 0.1 mol / L sodium hydroxide, and calculate the number of free amino groups (FAGs) using the consumed volume; the total nitrogen (TN) in the sample was determined by the Kjeldahl method according to the standard procedure; as a result, the degree of hydrolysis of the fish gelatin hydrolysate obtained by microwave treatment for 10 min was 65.37%; the degree of hydrolysis of the fish gelatin hydrolysate obtained by microwave treatment for 20 min was 74.53%.

[0059] The microstructure of fish glue before and after microwave treatment was observed by SEM, as Figure 1 shown. The surface of the untreated fish glue presented an uneven, mountain-like topological structure ( Figure 1 a in); after 10 min of microwave treatment, this uneven surface became flat, with several indentations and holes ( Figure 1 b in); and after 20 min of microwave treatment, the number of such features increased ( Figure 1 c in).

[0060] (3) Dissolve fish gelatin hydrolysate and starch in water at a mass ratio of 40:60, and let it stand at room temperature to form a gel to obtain the food 3D printing ink. The physical picture is as shown in Figure 2 c of; the SEM picture is as shown in Figure 3 c of; among the fish gelatin hydrolysates, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:5; the mass ratio of the total mass of fish gelatin hydrolysate and starch to the volume of water is 7.5 g:50 mL.

[0061] Example 2:

[0062] A preparation method of a food 3D printing ink, comprising the following steps:

[0063] (1) Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of fish skin to citric acid solution is 1 g:4 mL; then wash it with distilled water, stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate in a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0064] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is treated by microwave for 10 min, and the other part is treated by microwave for 20 min. The microwave power during the treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0065] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 60:40, and let it stand at room temperature to form a gel to obtain the food 3D printing ink. The physical picture is as shown in Figure 2 d of Figure 3 d of; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:5; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0066] Example 3:

[0067] A method for preparing a food 3D printing ink, comprising the following steps:

[0068] (1) Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0069] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is treated by microwave for 10 min, and the other part is treated by microwave for 20 min. The microwave power during the treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0070] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 40:60, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:8; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0071] Example 4:

[0072] A method for preparing a food 3D printing ink, comprising the following steps:

[0073] (1) Select fresh Australian lungfish, take the fish skin, soak it in a 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, and stir vigorously at 65 °C in a ratio of 1:1 of distilled water to citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0074] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is microwave-treated for 10 min, and the other part is microwave-treated for 20 min. The microwave power during the treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0075] (3) Dissolve the fish gelatin hydrolysate and starch in water at a mass ratio of 40:60, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; among the fish gelatin hydrolysates, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:10; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0076] Example 5:

[0077] A method for preparing a food 3D printing ink, comprising the following steps:

[0078] (1) Select fresh Australian lungfish, take the fish skin, soak it in a 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, and stir vigorously at 65 °C in a ratio of 1:1 of distilled water to citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0079] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is microwave-treated for 15 min, and the other part is microwave-treated for 20 min. The microwave power during the treatment is 50 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0080] (3) Dissolve the fish gelatin hydrolyzate and starch in water at a mass ratio of 40:60, and let it stand at room temperature to form a gel, obtaining the food 3D printing ink; in the fish gelatin hydrolyzate, the mass ratio of the fish gelatin hydrolyzate obtained by microwave treatment for 15 min to the fish gelatin hydrolyzate obtained by microwave treatment for 20 min is 1:5; the volume ratio of the total mass of the fish gelatin hydrolyzate and starch to water is 7.5 g:50 mL.

[0081] Example 6:

[0082] A preparation method of a food 3D printing ink, comprising the following steps:

[0083] (1) Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, and stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0084] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the added volume fraction of alkaline protease is 2%; then divide it into two parts, one part is microwave-treated for 10 min, and the other part is microwave-treated for 25 min, and the microwave power during treatment is 100 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and obtain fish gelatin hydrolyzate after freeze-drying;

[0085] (3) Dissolve the fish gelatin hydrolyzate and starch in water at a mass ratio of 40:60, and let it stand at room temperature to form a gel, obtaining the food 3D printing ink; in the fish gelatin hydrolyzate, the mass ratio of the fish gelatin hydrolyzate obtained by microwave treatment for 10 min to the fish gelatin hydrolyzate obtained by microwave treatment for 25 min is 1:5; the volume ratio of the total mass of the fish gelatin hydrolyzate and starch to water is 7.5 g:50 mL.

[0086] Comparative Example 1:

[0087] A preparation method of a food 3D printing ink, comprising the following steps:

[0088] Dissolve starch in water, and let it stand at room temperature to form a gel, obtaining the food 3D printing ink; its physical diagram is as shown in Figure 2 a of Figure 3 a of

[0089] Comparative Example 2:

[0090] A preparation method of a food 3D printing ink, comprising the following steps:

[0091] (1) Select fresh Australian lungfish, take the fish skin, soak it in a 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, and stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with a cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0092] (2) Adjust the pH value of the obtained fish glue to 8.0 with a sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is treated by microwave for 10 min, and the other part is treated by microwave for 20 min. The microwave power during treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry it to obtain fish gelatin hydrolysate;

[0093] (3) Dissolve the fish gelatin hydrolysate and starch in water at a mass ratio of 20:80, and let it stand at room temperature to form a gel to obtain the food 3D printing ink. The physical picture is as shown in Figure 2 b of Figure 3 b of ; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:5; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0094] Comparative Example 3:

[0095] A preparation method of a food 3D printing ink, comprising the following steps:

[0096] (1) Select fresh Australian lungfish, take the fish skin, soak it in a 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, and stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with a cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0097] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; then divide it into two parts, one part is treated by microwave for 10 min, and the other part is treated by microwave for 20 min. The microwave power during the treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0098] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 80:20, and let it stand at room temperature to form a gel to obtain the food 3D printing ink. The physical picture is as shown in Figure 2 e in Figure 3 e as shown; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 min to the fish gelatin hydrolysate obtained by microwave treatment for 20 min is 1:5; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0099] Comparative Example 4:

[0100] A preparation method of a food 3D printing ink, comprising the following steps:

[0101] (1) Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of the fish skin to the citric acid solution is 1 g:4 mL; then wash it with distilled water, stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water and citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate in a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0102] (2) Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; treat it by microwave for 10 min, the microwave power during the treatment is 60 W and the temperature is 55 °C; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and freeze-dry to obtain fish gelatin hydrolysate;

[0103] (3) Dissolve the fish gelatin hydrolysate and starch in water according to a mass ratio of 40:60, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0104] Comparative Example 5:

[0105] A preparation method of a food 3D printing ink, comprising the following steps:

[0106] (1)Select fresh Australian lungfish, take the fish skin, soak it in 0.25 wt% citric acid solution for 12 hours, and the mass-volume ratio of fish skin to citric acid solution is 1 g:4 mL; then wash it with distilled water, stir vigorously at 65 °C in a ratio of 1:1 by volume of distilled water to citric acid solution for 7 hours, then filter with cotton cloth, and dry the filtrate with a vacuum evaporator at 60 °C for 50 min to obtain fish glue;

[0107] (2)Adjust the pH value of the obtained fish glue to 8.0 with sodium hydroxide solution, mix it with alkaline protease, and the volume fraction of the added alkaline protease is 2%; perform microwave treatment for 20 min, with a microwave power of 60 W and a temperature of 55 °C during the treatment; after microwave treatment, inactivate the enzyme at -20 °C for 5 min, then centrifuge at 10000×g and 4 °C for 15 min, take the supernatant, and obtain fish gelatin hydrolysate after freeze-drying;

[0108] (3)Dissolve the fish gelatin hydrolysate and starch in water at a mass ratio of 40:60, and let it stand at room temperature to form a gel to obtain the food 3D printing ink; the total mass of the fish gelatin hydrolysate and starch and the volume ratio of water is 7.5 g:50 mL.

[0109] It can be seen from Figure 3 that in the 3D printing ink made of pure starch in Comparative Example 1, the gel forms an irregular network, which contains large and uneven gaps ( Figure 3 a in). In contrast, in Comparative Example 2, adding 20% of fish gelatin hydrolysate forms a tighter and more regular network ( Figure 3 b in), and the density of the network increases with the increase of the added percentage of fish gelatin hydrolysate ( Figure 3 c and d in). In Comparative Example 3, no gaps in the network can be detected in the SEM image of the gel made of 80% fish gelatin hydrolysate ( Figure 3 e in).

[0110] Test the viscosities of the 3D printing inks obtained in the above examples and comparative examples, and the results are as shown in Figure 4 It can be seen from Figure 4 that when too much (Comparative Example 3) or too little (Comparative Examples 1 and 2) fish gelatin hydrolysate is added, the viscosity of the 3D printing ink will decrease.

[0111] Test the relationship between the storage modulus and loss modulus of the 3D printing inks obtained in Example 1 and Comparative Examples 4 and 5 above and the angular frequency, and the results are as shown in Figure 5 and Figure 6As shown. The storage modulus is related to the elastic behavior of the material. It measures the ability of the material to store elastic energy and return it when the applied stress is removed; a higher storage modulus indicates that the material can withstand deformation and stress without significant permanent deformation; this is beneficial for maintaining the shape fidelity of the printed layer; a high storage modulus not only helps prevent excessive deformation or sagging of the printed structure during printing, but also enables a faster printing speed as the material can quickly recover its shape after extraction. 3D printing materials with a low storage modulus result in poor layer adhesion. The loss modulus is related to the viscous behavior of the material, and for 3D printing inks, a moderate loss modulus is ideal as it provides a certain degree of viscosity during printing, which helps achieve better layer adhesion and smooth deposition of the ink, contributing to improving the overall printing quality; however, 3D printing inks with too high a loss modulus are too viscous, making it difficult to extrude through the 3D printer nozzle. An ideal 3D printing ink should have a balanced combination of a high storage modulus and a moderate loss modulus for easy layer-by-layer printing. From Figure 5 and Figure 6 it can be seen that the dosages of fish gelatin hydrolysates with different degrees of hydrolysis in Example 1 are within the scope of the present invention, and the prepared 3D printing inks have the best balance of these parameters; while in Comparative Example 4, only the fish gelatin hydrolysate treated by microwave for 10 min is used, and both the storage modulus value and the loss modulus are small; in Comparative Example 5, only the fish gelatin hydrolysate treated by microwave for 20 min is used, and the storage modulus value is small, which is not conducive to improving the 3D printing accuracy.

[0112] To verify the above conclusions, the present invention uses the 3D printing inks prepared in the above comparative examples and examples to print 2D and 3D shapes, as Figures 7 - 9 shown. It can be seen that the 3D printing ink with a balanced high storage modulus and moderate loss modulus in Example 1 exhibits good printing accuracy, while the 3D printing inks in Comparative Example 4 and Comparative Example 5 cannot obtain printing images with better accuracy.

[0113] Texture analysis was performed on the printed 3D products, and the results are shown in Table 1.

[0114] Table 1: Texture analysis results

[0115]

[0116] As can be seen from Table 1, the food printed with the 3D printing ink prepared by the method of the present invention in the examples has better texture characteristics compared to the food printed with the 3D printing ink in the comparative examples.

Claims

1. A method for preparing food 3D printing ink, characterized in that: The steps include: (1) soaking fish skin in a citric acid solution, washing it with water, stirring it, filtering it, and drying it to obtain fish glue; (2) adjusting the pH value of the obtained fish gelatin to 7.5-8.5, mixing with alkaline enzyme, and then dividing into two parts, one part is microwave-treated for 10-15 min, and the other part is microwave-treated for 20-25 min, and the microwave power during the treatment is 50-100 W; after microwave treatment, the enzymes are inactivated respectively, and then the supernatant is taken after centrifugation, and freeze-dried to obtain fish gelatin hydrolyzate; (3) Dissolving fish gelatin hydrolysate and starch in water at a mass ratio of 40:60 to 60:40, and leaving at room temperature to form a gel to obtain the food 3D printing ink; in the fish gelatin hydrolysate, the mass ratio of the fish gelatin hydrolysate obtained by microwave treatment for 10 to 15 minutes to the fish gelatin hydrolysate obtained by microwave treatment for 20 to 25 minutes is 1:5 to 10.

2. The method for preparing the food 3D printing ink according to claim 1, characterized in that: The fish skin described in step (1) comes from lungfish.

3. The method for preparing food 3D printing ink according to claim 1, characterized in that: The mass concentration of the citric acid solution in step (1) is 0.2-0.3%, the mass volume ratio of fish skin to citric acid solution is 1 g:3-5 mL, and the immersion time of fish skin in the citric acid solution is 12-24 h.

4. The method for preparing the food 3D printing ink according to claim 1 or 3, characterized in that: The stirring temperature in step (1) is 60-70° C. and the stirring time is 6-8 h.

5. The method for preparing food 3D printing ink according to claim 1, characterized in that: The drying temperature in step (1) is 55-65°C and the drying time is 40-60 minutes.

6. The method for preparing food 3D printing ink according to claim 1, characterized in that: The alkaline enzyme described in step (2) is alkaline protease; the volume fraction of the added alkaline enzyme is 1-3%.

7. The method for preparing food 3D printing ink according to claim 1, characterized in that: The temperature during the microwave treatment in step (2) is 50-60°C.

8. The method for preparing the food 3D printing ink according to claim 1 or 6, characterized in that: In step (2), the temperature for enzyme inactivation is -20 to -25°C, and the time for enzyme inactivation is 5 to 10 min; the temperature during centrifugation is 0 to 4°C, the centrifugal force is 9000 to 11000×g, and the time is 10 to 20 min.

9. The method for preparing food 3D printing ink according to claim 1, characterized in that: In step (3), the volume ratio of the total mass of fish gelatin hydrolysate and starch to water is 7-8 g:50 mL.

10. A food 3D printing ink, characterized in that: It is prepared using the preparation method described in any one of claims 1 to 9.

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