Application of composite modified starch-based Pickering emulsion in 3D printing of surimi

Abstract

The invention belongs to the technical field of food processing, and relates to an application of a composite modified starch-based Pickering emulsion in 3D printing of surimi. Through a composite modification strategy of OSA modification and ball milling, the obtained composite modified starch is smaller in particle size and stronger in particle flexibility, and can be rapidly adsorbed and arranged on an oil-water interface to form a compact interface film, so that the Pickering emulsion has excellent stability; the composite modified starch-based Pickering emulsion is added into surimi to serve as printing ink, so that the rheological property and the extrudability of the surimi can be remarkably improved, and the printing shape fidelity is improved; starch particles in the emulsion absorb water to swell and fill protein network pores, so that the network structure of the minced fillet gel is enhanced, the water binding capacity is remarkably improved, the cooking loss is reduced, and the gel strength and microstructure uniformity are improved.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology and relates to the application of a composite modified starch-based Pickering emulsion in surimi 3D printing. Background Technology

[0002] 3D printing is a collective term for a series of technologies that utilize computer-aided design to print various three-dimensional products from raw materials such as liquids, powders, or filaments according to a pre-defined shape model using a 3D printer. With the rapid development of 3D printing technology and continuous exploration of its applications, its application areas have expanded from traditional mold manufacturing to aerospace, medical biology, and food industries. Compared to traditional food production technologies, food 3D printing technology has significant advantages: it eliminates the need for machining or molds, directly generating objects of arbitrarily complex shapes based on computer graphics data, especially capable of manufacturing irregularly shaped structures that are difficult to achieve with traditional techniques; with proper design, it can significantly shorten the food research and processing cycle, reduce costs by simplifying production lines, and improve production efficiency, thus being considered a major driving force for the development of the food industry.

[0003] Despite the immense potential of 3D printing technology in the food industry, its widespread application remains limited by the core bottleneck of material selection. Suitable food materials for 3D printing must meet specific physical properties, often being liquid, paste-like, or powdered ingredients. This necessitates pre-processing common ingredients like fish, meat, and vegetables into a paste form, and ensuring they possess suitable viscosity, fineness, and rheological properties for printing. Surimi products, due to their unique elasticity, flavor, and plasticity, are widely used in various food processing applications. Furthermore, surimi systems naturally possess certain gel strength, viscosity, and rheological characteristics, which theoretically meet the material requirements for 3D food printing. Therefore, surimi has become a promising raw material for food 3D printing in current research. However, existing surimi materials still have significant drawbacks, exhibiting low printing accuracy and stability. Therefore, improving the molding performance and 3D printing adaptability of surimi by adjusting its formulation is of significant theoretical and practical importance for the development of 3D printing surimi systems. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing an application of a composite modified starch-based Pickering emulsion in surimi 3D printing. By preparing a unique composite modified starch-based Pickering emulsion and applying it to surimi, the 3D printing effect can be improved.

[0005] This invention provides an application of a composite modified starch-based Pickering emulsion in surimi 3D printing, wherein the composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

[0006] Octenyl succinic anhydride solution is formed by dissolving octenyl succinic anhydride in an organic solvent, such as one or more of methanol, ethanol, isopropanol, acetone, and tetrahydrofuran. Starch suspension is formed by dispersing starch in water, with the pH adjusted to 8.0–9.0 by adding alkali.

[0007] Preferably, the concentration of the octenyl succinic anhydride solution is 10-30 wt%, and the concentration of the starch suspension is 20-40 wt%.

[0008] Preferably, the octenyl succinic anhydride is 1 to 10 wt% of the starch weight.

[0009] Preferably, the octenyl succinic anhydride solution is added dropwise to the starch suspension over a period of 1 to 3 hours.

[0010] Preferably, the reaction in step S1 is carried out at 30~50°C for 1~8 h.

[0011] The reaction was terminated by adjusting the pH to 6.0-7.0 by adding acid to the starch suspension.

[0012] Preferably, in step S2, the ball milling parameters include: a ball-to-material ratio of 2 to 10:1, a ball milling speed of 100 to 800 rpm, and a ball milling time of 0.5 to 3 h. More preferably, the ball milling time is 2 h.

[0013] Preferably, the starch dispersion concentration in step S3 is 3-8 wt%.

[0014] Preferably, the vegetable oil is one or more of soybean oil, corn oil, and peanut oil.

[0015] Preferably, the volume ratio of starch dispersion to vegetable oil is 1:1 to 2.

[0016] Preferably, the application includes the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products.

[0017] Preferably, the fish raw materials include one or more of squid, octopus, cuttlefish, freshwater fish, and saltwater fish.

[0018] Preferably, the temperature of the entire pounding process is controlled below 10°C.

[0019] Preferably, the amount of salt added is 1 to 5 wt% of the fish raw material.

[0020] Preferably, the amount of the composite modified starch-based Pickering emulsion added is 5-20 wt% of the fish raw material. More preferably, the amount of the composite modified starch-based Pickering emulsion added is 10 wt% of the fish raw material.

[0021] Preferably, the 3D printing parameters include: nozzle inner diameter of 1~2 mm, nozzle height of 1.5~3.0 mm, infill density of 50~90%, moving speed of 20~40 mm / s, and infill pattern of linear or honeycomb type. More preferably, the infill density is 80% and the infill pattern is linear.

[0022] Preferably, 3D printing is performed at 20~30℃.

[0023] Preferably, the application further includes a curing step: placing the 3D surimi gel product in an electric oven and heating it at 130~160℃ for 8~15 minutes.

[0024] A second aspect of this invention provides a method for preparing a 3D surimi gel product, comprising the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products. The composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

[0025] A second aspect of this invention provides a method for preparing a 3D surimi gel product, comprising the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products. Place the 3D surimi gel product in an electric oven and heat at 130~160℃ for 8~15 minutes; The composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a composite modification strategy of OSA modification and ball milling, resulting in composite modified starch particles with smaller particle size and greater flexibility. These particles can be rapidly adsorbed and arranged at the oil-water interface to form a dense interfacial film, giving the Pickering emulsion excellent stability. When this composite modified starch-based Pickering emulsion is added to fish paste as a printing ink, it can significantly improve its rheological properties and extrudability, thereby enhancing the fidelity of printed shapes.

[0027] 2. The addition of composite modified starch-based Pickering emulsion optimizes the shear thinning characteristics of surimi ink and provides a suitable G' value, making the ink easy to extrude from the nozzle and able to quickly self-support, resulting in uniform and continuous printed lines. This significantly improves the accuracy and stability of 3D printing, avoiding defects such as broken lines, collapse, and discontinuous lines. In particular, it exhibits high clarity and good support for complex structures such as pumpkins and squids.

[0028] 3. The starch granules in the emulsion absorb water and swell, filling the pores of the protein network, which enhances the network structure of the surimi gel, significantly improves water retention, reduces cooking loss, and improves gel strength and microstructure uniformity. The uniform scattering effect of the emulsion droplets improves the whiteness of the finished product, makes the surface smoother, and makes the appearance more attractive, thus improving both taste and appearance quality.

[0029] 4. The 3D printing surimi gel prepared by this invention is further cured by heating in an electric oven, which can minimize deformation, improve the thermal stability of the printed product, and maintain the original printed structure.

[0030] 5. Without relying on molds and complex machining, the irregular structure of surimi products can be directly prepared through 3D printer, shortening the processing cycle of surimi products and improving production efficiency. At the same time, the emulsion raw materials are easy to prepare and the cost is controllable, taking into account both production efficiency and economy. Attached Figure Description

[0031] Figure 1 The image shows the layering of Pickering emulsions prepared from starch samples NS, OS, OBS-0.5, OBS-1, OBS-2, and OBS-3 in Example 1 after 30 days of storage.

[0032] Figure 2 The image shows a comparison of the emulsification index (EI) of Pickering emulsions prepared from starch samples NS, OS, OBS-0.5, OBS-1, OBS-2, and OBS-3 in Example 1 after 30 days of storage.

[0033] Figure 3 The graph shows the printing accuracy and printing stability of each group in Example 2.

[0034] Figure 4 The rheological properties (A), G' value (B), and G" value (C) of each group in Example 2 at different shear rates are shown.

[0035] Figure 5 This is a comparison chart of cooking loss and water retention of the 3D printed fish paste gel products in each group in Example 2.

[0036] Figure 6The diagram shows the breaking force, breaking distance (A), and gel strength (B) of the 3D-printed surimi gel products in each group in Example 2.

[0037] Figure 7 SEM images of the 3D-printed fish paste gel products from each group in Example 2.

[0038] Figure 8 The images show magnetic resonance imaging (MRI) images of the 3D-printed fish paste gel products from each group in Example 2.

[0039] Figure 9 The image shows the appearance of the cylindrical 3D surimi-printed products obtained with different emulsion addition amounts in Example 3.

[0040] Figure 10 The image shows the appearance of the 3D surimi-printed cubes with square grooves obtained by different emulsion addition amounts in Example 3.

[0041] Figure 11 The image shows the appearance of the pumpkin-shaped 3D surimi-printed products obtained by adding different amounts of emulsion in Example 3.

[0042] Figure 12 The image shows the appearance of the squid-shaped 3D surimi-printed products obtained by adding different amounts of emulsion in Example 3.

[0043] Figure 13 The image shows the appearance of the 3D surimi-printed products obtained with different filling patterns and different filling densities in Example 4.

[0044] Figure 14 The images show the appearance of the finished products after treatment under different ripening conditions in Example 5. Detailed Implementation

[0045] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, and includes both a and b. "Multiple" includes two, three, four, five, or more.

[0046] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0047] In the following examples and comparative examples, soybean oil was purchased from Yihai Kerry Arawana Holdings Co., Ltd. (Shanghai, China). Octenyl succinic anhydride (OSA) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. (Shanghai, China). Tapioca starch was purchased from SuayMak Mak Foods (Bangkok) Co., Ltd.

[0048] Planetary ball mill: QM-3SP2, Nanjing Laibu Technology Industry Co., Ltd.

[0049] High-speed disperser: T18 digital Ultra-Turrax, IKA Instruments GmbH, Germany.

[0050] Example 1: Study on the effect of different modification conditions on the properties of Pickering emulsion Preparation of modified starch: Cassava starch (NS) was dispersed in distilled water and stirred continuously to form a starch suspension with a concentration of 30 wt%. The suspension was heated to 40 °C in a water bath, and then 1 M NaOH solution was added to maintain the pH of the starch suspension at 8.3. Next, 20 wt% OSA solution (OSA dissolved in ethanol) was added dropwise to the starch suspension over approximately 2 hours (the amount of OSA added was 3 wt% of the weight of NS). The temperature was maintained, and the mixture was stirred for another 4 hours to complete the reaction. The reaction was terminated by adjusting the pH of the mixture to 6.5 with 1 M HCl. The mixture was centrifuged (6000 rpm, 10 min), then washed twice successively with anhydrous ethanol and deionized water, dried at 40 °C, and then ground into powder to obtain modified starch OS. Subsequently, OS was subjected to planetary ball milling. OS was placed in a planetary ball mill with a ball-to-material mass ratio of 4:1 and milled at a speed of 500 r / min for 0.5, 1, 2 and 3 hours respectively. The resulting composite modified starches were named OBS-0.5, OBS-1, OBS-2 and OBS-3 respectively.

[0051] Preparation of Pickering emulsion: NS, OS, OBS-0.5, OBS-1, OBS-2, and OBS-3 starch samples were dispersed in deionized water to prepare 5 wt% starch dispersions. These dispersions were then mixed with soybean oil at a volume ratio of 4:6 and homogenized using a high-speed disperser at 20,000 rpm for 3 minutes to obtain the Pickering emulsion.

[0052] Particle size determination The particle size distribution of starch was analyzed using a laser diffraction spectrometer (Mastersizer 2000, Malvern Instruments Ltd., Worcestershire, UK). NS, OS, OBS-0.5, OBS-1, OBS-2, and OBS-3 starch samples were suspended in anhydrous ethanol (0.01 g / mL) and homogenized using a vortex mixer. The refractive indices of water and the samples were set to 1.33 and 1.54, respectively. Particle size was expressed as a volume-weighted average particle size (D0). 4,3 The results are shown in Table 1.

[0053] Emulsion stability The newly prepared emulsion samples were stored at room temperature (25±1℃) for 30 days, and their phase separation and stratification were periodically assessed by visual observation. The emulsification index (EI) was calculated using the formula: EI = (H0 / H) × 100%, Where: H0 represents the height of the emulsion layer; H represents the total height of the sample in the container.

[0054] Table 1. Effects of modification conditions on starch particle size and relative crystallinity Different letters used to label the same parameter indicate significant differences (P<0.05).

[0055] As shown in Table 1, the particle size of the NS, OS, OBS-0.5, OBS-1, OBS-2, and OBS-3 starch samples showed a trend of first decreasing and then increasing. This trend may be due to the introduction of OSA groups during esterification, which reduces the attraction between starch particles, promotes dispersion, and thus reduces the particle size of aggregated particles. With increasing ball milling time, the D4,3 value gradually decreased, reaching its minimum at 2 hours of ball milling. This indicates that the mechanical impact and shear force generated by the grinding media disrupted the starch particles, breaking down amylopectin into smaller molecular weight components (mainly amylose), and the particle size further decreased with prolonged ball milling time. Interestingly, when the ball milling time was extended to 3 hours, the D4,3 value increased slightly. This may be due to the higher surface energy of the fine starch fragments, which re-aggregated under the drive of intermolecular forces such as hydrogen bonds, at which point the particle aggregation rate exceeded the rate of further fragmentation. These particle size changes are particularly important in Pickering emulsion systems, where smaller starch particles can improve emulsion formation because they can be adsorbed at the oil-water interface more quickly and effectively. In contrast, larger particles require a longer adsorption time and tend to form emulsions with larger droplet sizes, leading to decreased emulsion stability.

[0056] Photos of Pickering lotion stored from day 1 to day 30, as shown. Figure 1 As shown, the corresponding emulsification index (EI) is as follows: Figure 2As shown, unmodified NS could not form a stable emulsion system, likely due to its inherent hydrophilicity. On day 1 of storage, a semi-transparent water layer appeared at the bottom of the Pickering emulsions stabilized by OS, OBS-0.5, and OBS-1, indicating poor stability. As the ball milling time was extended to 2 and 3 hours, the EI gradually increased, reaching 100%, indicating a fully emulsified system. The additional ball milling treatment after esterification reduced the rigidity of the particles, enhanced their flexibility and deformability, while reducing the particle size and increasing the surface area. These properties enabled the particles to quickly adsorb and align at the oil-water interface, forming a dense hydrated film around the oil droplets, thereby enhancing the stability of the Pickering emulsion.

[0057] In summary, OBS-2 starch samples were used for subsequent 3D printing experiments.

[0058] Example 2: Study on the effect of different emulsion addition amounts on the performance of 3D surimi-printed products Preparation of 3D printing ink: Frozen squid was thawed at 4°C and cut into small pieces, then placed in a vacuum chopper and mashed. The temperature was controlled below 10°C. The mashing process included: pounding for 2 minutes without water, adding 2.5 wt% salt, chopping with salt for 2 minutes, adding 5 wt% soybean oil, and then adding 0 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt% Pickering emulsion (the Pickering emulsion prepared from the OBS-2 starch sample in Example 1). The mass percentages here represent the mass fraction of the emulsion, soybean oil, or salt relative to the squid. The moisture content was adjusted to 80% with ice water, and chopping was continued for 4 minutes to obtain the printing surimi ink, corresponding to the groups Oil, Control, 5%, 10%, 15%, and 20%.

[0059] Preparation of 3D surimi gel products: An ink cartridge containing surimi printing ink was loaded into the extrusion system of a 3D printer. Printing was carried out at ambient temperature (25℃). A cylinder (diameter d=25 mm, height h=10 mm) was selected as the geometry of the target surimi product. The printing parameters were set as follows: nozzle inner diameter 1.55 mm, nozzle height 2 mm, infill density 80%, moving speed 30 mm / s, and the infill pattern was linear.

[0060] The center height of the 3D surimi-printed product prepared above was measured, and the accuracy of the 3D printed product was calculated according to the formula. The center height of the printed sample was measured again after 2 hours, and the printing stability was calculated. The results are shown below. Figure 3Compared to the control group and the oil group, the emulsion group has higher precision and stability. This may be because the starch particles in the emulsion absorb water and swell, filling the gaps in the protein network and improving the shortcomings of fish paste ink in terms of low viscosity and poor stability of printed products.

[0061] Rheological properties are an important indicator affecting 3D printing inks and one of the core attributes influencing the quality of 3D printed products. The rheological properties of surimi inks with different emulsion addition amounts are shown below. Figure 4 As shown in (A), as the shear rate increased from 0.01 rad / s to 100 rad / s, all samples showed a decreasing trend in apparent viscosity, exhibiting the shear-thinning characteristics of emulsified surimi ink. This is due to the disruption and rearrangement of the original structure of the samples. This inherent shear-thinning characteristic generally facilitates the successful extrusion of ink from the nozzle and deposition onto the designed structure on the platform. The shear-thinning behavior ensures safe / easy swallowing during chewing. At the same shear rate, the Control group exhibited the highest apparent viscosity. The oil group followed, with viscosity values ​​gradually decreasing with the addition of emulsion, indicating a certain dilution effect on the surimi system with increasing emulsion content. This may be related to the lubricating effect of the oil components. Excessively high viscosity values ​​proved detrimental to ink passing through nozzles with smaller diameters; the printing accuracy and stability of the Control group were significantly lower than other groups.

[0062] To further understand the network structure of surimi ink, frequency scanning tests were performed on the surimi ink, and the G' and G" values ​​of all inks in the 0.1~100 angular frequency range were analyzed, such as... Figure 4 As shown in (B) and 4(C), the G' and G' values ​​of all inks exhibit a slight frequency dependence, indicating that their rheological properties are affected by the applied frequency. Generally, the higher the mechanical strength of a material, the better its self-supporting properties. However, some studies have shown that excessively high G' values ​​may also lead to phenomena such as ink breakage during printing, which is also detrimental to 3D printing. In the Control group, the ink mechanical strength is too high, indicating that it requires maximum extrusion pressure to begin flowing. This can also explain the discontinuous lines and incomplete finished products when printing complex shapes such as pumpkins and squid. In the Oil group, the ink mechanical strength is too low, resulting in poor support of the printed product, which is not conducive to 3D printing. Compared with the control group inks, the inks with added composite modified Pickering emulsion have higher G' values, and the values ​​increase with the amount of emulsion added. In previous experiments, inks with 10% emulsion addition significantly improved printing accuracy, indicating that ideal 3D printing inks should have a suitable G'.

[0063] Cooking loss and water retention refer to the ability of surimi gel to retain its own moisture, which are important properties of surimi gel and directly affect its texture, taste, and stability during storage. Cooking loss: Weigh the initial mass (M0) of the 3D printed sample. After aging, cool to 4°C and weigh the mass after cooking (M1). Cooking loss (%) = [(M0-M1) / M0]×100%. Water retention: Weigh the mass of the aged 3D printed gel sample before centrifugation (M3). Wrap the sample in filter paper and centrifuge at 8000 rpm for 10 min at 4°C. Weigh the mass of the sample after centrifugation (M4). Water retention (%) = M4 / M3×100%. Figure 5 As shown, the oil group exhibited the lowest water-holding capacity (WHC) and the highest cooking loss, possibly because the addition of liquid oil directly interferes with the protein interactions within the gel. Compared to the control and oil groups, the emulsion group showed higher water-holding capacity and lower cooking loss, with water-holding capacity initially increasing and then decreasing, while cooking loss showed the opposite trend. This may be because the emulsion enhances the network structure of the gel, thereby achieving stronger water-holding capacity. At an addition level of 10%, the 3D-printed fish paste product exhibited the lowest cooking loss and the best water-holding capacity.

[0064] The breaking force, breaking deformation, and gel strength of 3D-printed surimi gel products are as follows: Figure 6 As shown, the oil group showed a slight increase in breaking force and gel strength, but the change was not significant. With increasing emulsion content, both breaking force and gel strength initially increased and then decreased, indicating that the addition of emulsion improved the gelation properties of the 3D-printed surimi product. The emulsion group exhibited superior gelation properties compared to the oil group. The Pickering emulsion, stabilized by composite modified starch particles, demonstrated stability, reducing the likelihood of phase transitions in soybean oil during surimi chopping or heating due to external force or temperature increases. Specifically, when the emulsion content reached 10%, the highest breaking force, breaking distance, and gel strength were observed, with significant differences (p < 0.05).

[0065] The microstructures of 3D printing gels prepared with different emulsion addition amounts were photographed, and the results are as follows: Figure 7As shown, the formation of the microstructure depends on the orderly aggregation of myofibrillar proteins and the interactions between protein molecules. The blank control group and the oil group without emulsion exhibit a relatively coarse and loose microstructure with fewer pores, which corresponds to the results of fixed and free water, leading to low water-holding capacity. In the surimi gel group with emulsion, the gel network structure becomes denser. As the emulsion concentration increases, when the emulsion addition reaches 10%, the gel network structure becomes clearer, with smaller network pore sizes and a smoother surface. This may be because the emulsion reduces the interference of oil on the interactions between myofibrillar proteins during heating, improving the density and uniformity of the surimi gel network structure. The addition of emulsion has a positive impact on 3D printing surimi gels. However, with further increases in emulsion addition, the gel pore size increases, possibly because the encapsulation effect of surimi proteins on emulsion droplets is approaching its limit, and excessive emulsion filling can lead to the destruction of the gel network structure.

[0066] Moisture distribution reflects the degree of binding between surimi protein molecules and water molecules, thus indicating the fluidity of water within the sample. To clarify the effect of emulsion addition amount on the moisture content of the 3D-printed surimi gel product, P was used to... 21 P 22 P 23 The numbers represent bound water, fixed water, and free water in the samples. Fixed water had the highest content. The content of fixed water is usually related to water-holding capacity, and increased water-holding capacity promotes gel formation. Table 2 shows that the soybean oil group had little effect on the water distribution of the 3D surimi gel. Simultaneously, it was observed that the addition of the emulsion had an effect on P... 21 The changes in values ​​were not significant, indicating that the effect of the emulsion on the bound water content in the surimi gel was negligible. Compared with the control group, the free water content reached its lowest value when the emulsion addition reached 10%, with free water transforming into fixed water. This is because the Pickering emulsion itself has the ability to bind water molecules and inhibit water migration, indicating the formation of a denser gel network structure inside the 3D printed material. However, excessive emulsion weakens the water-binding ability of myofibril proteins, accelerating the conversion of bound water and fixed water into free water. This may be because the steric hindrance caused by the Pickering emulsion as a copolymer during gel formation reduces the formation of the protein network. In addition, at the same chopping time, excessive emulsion increases the risk of instability when mixed with surimi, causing the surimi network to be disturbed, resulting in larger pores and further promoting water flowability, which can be verified from the surimi microstructure.

[0067] Table 2. Moisture distribution of different samples .

[0068] Magnetic resonance imaging can provide in-depth insights into the proton density of a sample, such as... Figure 8As shown, high-intensity signals represent fixed or bound water, while low-intensity signals represent free water. Compared to the control and oil groups, the red areas increased in the 5% and 10% emulsion groups, indicating higher hydrogen proton density. This is because the addition of Pickering emulsion promotes the unfolding of myofibril protein structures, resulting in tighter protein-water binding and a denser gel network structure. With continued increase in emulsion addition, the yellow areas gradually increased, indicating that excessive emulsion led to reduced gel uniformity and deterioration of the network structure.

[0069] Color is a key factor for consumers when choosing aquatic products, especially the whiteness value of surimi gel. Table 3 shows the changes in L*, a*, b*, and whiteness of the gel samples after adding emulsion. After adding emulsion, the L* value of the samples increased, the b* value generally increased, but the a* value decreased. The enhanced light scattering after adding emulsion may affect the color of the gel. a* represents red-green hues, possibly because the addition of emulsion physically masks pigments, reducing the absorption and reflection of red light. Compared with direct oil addition, Pickering emulsion droplets, due to their smaller particle size, are more evenly distributed in the gel matrix, which is beneficial for enhancing light scattering and thus improving the whiteness of the sample. The whiteness increases with the increase of emulsion addition, from 79.91 to 81.06. With the increase of emulsion addition, the composite modified starch particles, which act as emulsion stabilizers, increase, which can appropriately improve the whiteness of the emulsion.

[0070] Table 3. L*, a*, b* and whiteness of different samples .

[0071] Example 3: Study on the effect of different emulsion addition amounts on the appearance of 3D surimi-printed products of different shapes The preparation of 3D printing ink is the same as in Example 2.

[0072] Preparation of 3D surimi gel products: A cartridge containing surimi printing ink was loaded into the extrusion system of a 3D printer. Printing was carried out at ambient temperature (25℃). The target surimi product geometries were selected as cylinder (diameter d=25 mm, height h=10 mm), square-grooved cube, pumpkin shape, and squid shape. The printing parameters were set as follows: nozzle inner diameter 1.55 mm, nozzle height 2 mm, infill density 80%, moving speed 30 mm / s, and linear infill pattern.

[0073] The printed finished products are as follows Figure 9-12As shown in the figure, in the control group, discontinuous ink extrusion was observed, resulting in incomplete printed products with numerous gaps and ink overflow. This may be because the ink in the control group has a higher viscosity, leading to filament breakage during printing and extrusion, causing material accumulation, sudden compression, and deposition collapse. Adding an appropriate amount of Pickering emulsion to the ink improved the printing performance of the squid surimi ink, resulting in printed products with higher support and more uniform line distribution. Overall, with an emulsion addition of 10%, the printed samples exhibited high clarity and line resolution.

[0074] Example 4: Studying the effects of different printing parameters Preparation of 3D printing ink: Frozen squid was thawed at 4°C and cut into small pieces. The pieces were then placed in a vacuum chopper and mashed. The temperature was controlled below 10°C. The mashing process included: pounding for 2 minutes without water, adding 2.5 wt% salt, chopping with salt for 2 minutes, adding 10 wt% Pickering emulsion (the Pickering emulsion prepared from the OBS-2 starch sample in Example 1). Here, the mass percentage represents the mass fraction of the emulsion, soybean oil, or salt relative to the squid. The moisture content was adjusted to 78% with ice water, and chopping continued for 4 minutes to obtain the surimi printing ink.

[0075] Preparation of 3D surimi gel products: A cartridge containing surimi printing ink was loaded into the extrusion system of a 3D printer. Printing was carried out at ambient temperature (25℃). A cylinder (diameter d=25 mm, height h=10 mm) was selected as the geometry of the target surimi product. The printing parameters were set as follows: nozzle inner diameter 1.55 mm, nozzle height 2 mm, infill densities of 20%, 50%, and 80%, and a moving speed of 30 mm / s. The infill patterns were: linear (samples named linear-20%, linear-50%, linear-80% according to different infill densities), Hilbert curve (samples named curve-20%, curve-50%, curve-80% according to different infill densities), and honeycomb (samples named honeycomb-20%, honeycomb-50%, honeycomb-80% according to different infill densities).

[0076] To investigate the effects of different printing parameters on emulsified squid surimi gel, the infill pattern and infill density during the 3D printing process were explored. The results are as follows: Figure 13 As shown: Selecting straight lines and honeycomb patterns for the print fill pattern, with fill densities of 50% and 80%, results in high print quality. When the fill pattern is a Hilbert curve, the print quality is low regardless of the fill density.

[0077] The textural properties of the 3D-printed surimi gel were tested after curing (the curing process included: curing the printed sample at 90 °C for 30 min in a calibrated constant-temperature water bath, ensuring complete immersion throughout to avoid uneven heating; immediately wiping the sample surface with filter paper to remove adhering moisture after curing, and cooling at 4 °C for later use). Table 4 shows the textural properties of the 3D-printed product with 10% composite modified starch-based Pickering emulsion after two extrusion cycles, under different infill patterns and infill rates. The 3D printing pattern design significantly affected the textural properties of the surimi gel product. As the infill percentage decreased, the hardness of the surimi product decreased accordingly; from an infill rate of 80% to 20%, the hardness decreased by 1.84–2.13 times. The results indicate that the infill percentage is directly proportional to the hardness. Chewability is related to hardness; in the current study, it was observed that chewiness is also directly proportional to the infill rate. The optimal textural properties were achieved when the infill rate was 80% and the infill pattern was linear.

[0078] Table 4. Texture properties of different samples in Example 4 .

[0079] Example 5: Study on the effect of different curing conditions on the appearance of 3D surimi-printed products Preparation of 3D printing ink: Frozen squid was thawed at 4°C and cut into small pieces. The pieces were then placed in a vacuum chopper and mashed. The temperature was controlled below 10°C. The mashing process included: pounding for 2 minutes without water, adding 2.5 wt% salt, chopping with salt for 2 minutes, adding 10 wt% Pickering emulsion (the Pickering emulsion prepared from the OBS-2 starch sample in Example 1). Here, the mass percentage represents the mass fraction of the emulsion, soybean oil, or salt relative to the squid. The moisture content was adjusted to 78% with ice water, and chopping continued for 4 minutes to obtain the surimi printing ink.

[0080] Preparation of 3D surimi gel products: An ink cartridge containing surimi printing ink was loaded into the extrusion system of a 3D printer. Printing was carried out at ambient temperature (25℃). A cylinder (diameter d=25 mm, height h=10 mm) was selected as the geometry of the target surimi product. The printing parameters were set as follows: nozzle inner diameter 1.55 mm, nozzle height 2 mm, infill density 80%, moving speed 30 mm / s, and the infill pattern was linear.

[0081] Product maturation: The 3D surimi gel product is subjected to heat treatment under one of the following conditions (1)-(5): (1) One-step heating: 90℃, 30min; (2) Two-step heating: 40℃, 40 min; 90℃, 30 min; (3) Electric oven heating: 150℃, 10min; (4) Microwave heating: 35s; (5) Steaming: 10 minutes.

[0082] The finished product after aging process looks like Figure 14 As shown. During heating, the fish paste proteins denature and intertwine to form a new protein network structure. During cooking, the gel absorbs moisture, and during microwave heating, the gel's internal temperature rises rapidly, causing the moisture to oriented and resulting in significant deformation of the original printed shape. The appearance and height of the oven-cured product are not significantly different from the uncooked fish paste printed sample. This is likely because the oven's heat is transferred from the outside to the inside, and the surface of the fish paste product easily forms a dry film due to moisture evaporation, resulting in minimal impact of heating conditions on deformation compared to other methods. Therefore, for 3D-printed fish paste gel products, using an electric oven for curing can maintain the product shape to the greatest extent.

[0083] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0084] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0085] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. The application of a composite modified starch-based Pickering emulsion in surimi 3D printing, wherein the composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

2. The application according to claim 1, characterized in that, The application includes the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products.

3. The application according to claim 2, characterized in that, The application also includes a curing step: placing the 3D surimi gel product in an electric oven and heating it at 130~160℃ for 8~15 minutes.

4. The application according to claim 1, characterized in that, The concentration of the octenyl succinic anhydride solution was 10–30 wt%, and the concentration of the starch suspension was 20–40 wt%. And / or, octenyl succinic anhydride is 1 to 10 wt% of starch weight; And / or, octenyl succinic anhydride solution is added dropwise to starch suspension over a period of 1 to 3 hours; And / or, the reaction in step S1 is carried out at 30~50℃ for 1~8 h; And / or, in step S2, the ball milling parameters include: a ball-to-material ratio of 2 to 10:1, a ball milling speed of 100 to 800 rpm, and a ball milling time of 0.5 to 3 h; And / or, the starch dispersion concentration in step S3 is 3~8 wt%; And / or, the vegetable oil is one or more of soybean oil, corn oil, and peanut oil; And / or, the volume ratio of starch dispersion to vegetable oil is 1:1~2.

5. The application according to claim 1, characterized in that, The ball milling time was 2 hours.

6. The application according to claim 2, characterized in that, Fish-based ingredients include one or more of squid, octopus, cuttlefish, freshwater fish, and saltwater fish; And / or, the temperature of the entire pounding process is controlled below 10℃; And / or, the amount of salt added is 1-5 wt% of the fish raw material; And / or, the amount of composite modified starch-based Pickering emulsion added is 5-20 wt% of the fish raw material.

7. The application according to claim 2, characterized in that, 3D printing parameters include: nozzle inner diameter of 1~2 mm, nozzle height of 1.5~3.0 mm, infill density of 50~90%, moving speed of 20~40 mm / s, and infill pattern of linear or honeycomb.

8. The application according to claim 2, characterized in that, The amount of composite modified starch-based Pickering emulsion added was 10 wt% of the fish raw material; The fill density is 80%, and the fill pattern is a straight line.

9. A method for preparing a 3D surimi gel product, characterized in that, Includes the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products. The composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

10. A method for preparing a 3D surimi gel product, characterized in that, Includes the following steps: After the fish raw material is chopped, it is placed in a vacuum chopper and pounded. The pounding process includes: pounding for 1 to 5 minutes without water, then adding salt and pounding for 1 to 5 minutes with salt, then adding composite modified starch-based Pickering emulsion and adjusting the moisture content to 70 to 85 wt%, and continuing to chop for 2 to 6 minutes to obtain printing fish paste ink. The printing fish paste ink is placed in an ink cartridge, loaded into the extrusion system of a 3D printer, and 3D printed to obtain 3D fish paste gel products. Place the 3D surimi gel product in an electric oven and heat at 130~160℃ for 8~15 minutes; The composite modified starch-based Pickering emulsion is prepared by a method comprising the following steps: S1. Add octenyl succinic anhydride solution dropwise into a starch suspension with pH 8.0~9.0, stir the reaction, adjust the pH to 6.0~7.0 to terminate the reaction, centrifuge, wash and dry the product to obtain octenyl succinic anhydride modified starch. S2. Octenyl succinic anhydride was ball-milled to obtain composite modified starch; S3. Disperse the composite modified starch in water to obtain a starch dispersion. Mix the starch dispersion with vegetable oil and homogenize at 10,000 to 30,000 rpm for 1 to 10 minutes to obtain a composite modified starch-based Pickering emulsion.

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