# Plant-Based Fish Analogs--A Review
## 4 Technologies Used for Plant-Based Fish and Meat Analogs Production
### 3D and 4D Printing  
A problematic aspect when obtaining plant analogs of animal products is providing them with an appropriate texture. Therefore, there is a need to find solutions that allow obtaining analogs with similar taste or nutritional properties and an appropriate structure, e.g., fish fillets. One way to achieve the right structure is to use 3D or 4D printing. Using 3D food printing enables the preparation of personalized food, with a complex structure, obtained layer by layer, according to programmed digital models created using computer-aided design/production software (CAD/CAM) [16; 112; 113]. Various 3D food printing techniques have been developed for creating stable three-dimensional products, such as extrusion-based printing, inkjet printing, bioprinting, and powder bed printing [113; 114]. However, the most commonly used in producing high-protein foods, i.e., meat and fish analogs, is extrusion-based printing, a fairly long-lasting food printing process, wherein fibrous meat or analog materials are extruded from a nozzle in order to form 3D structures [112; 115]. In the syringe injection process, the highly viscous protein solution is extruded through the moving nozzle of a thin syringe layer by layer to form a 3D product, e.g., a muscle-like structure [25]. Although bioprinting is under development, it is also accomplished through the usual three primary methods--jetting, lasers, and extrusion [116]. Research is underway using the binder jet technique, a powder printing technology in which a liquid binder is precisely deposited to agglomerate adjacent powder particles to build a 3D-printed structure. However, it is a difficult technique due to the swelling of protein raw materials during the process [112]. Swelling of the powder particles impairs the printing process. The wet layer appears above the surface, causing misalignment and breakage of structures upon application of the next layer of powder [117]. Research conducted by [PERSON] et al. [112] showed that the increasing binder content in printed food products resulted in greater sample consistency and that the protein content of dry powder blends had a significant impact on the elasticity of the final product. By adjusting the amount of binder deposited, as well as the addition of calcium caseinate to the dry powder mixtures, a wide range of textures was achieved, such as textures similar to crushed dough or elastic gum. It has been suggested that 3D printing can potentially reduce waste and energy in the food industry. For the production of meat and fish analogs with 3D printing technology, materials derived mainly from insects, plants, and cell cultures are used, which are tested for technological feasibility, environmental impact, and consumer acceptance. It is also possible to use industrial waste [113]. The 3D printing technology can be used not only to eliminate the sensory differences between meat from vegetable protein and real meat but also to adapt plant analogs to consumers' different preferences and needs. In addition, the printed 3D model should be durable and resistant to thermal cooking processes after printing. This is due to the need for heat treatment of finished products before consumption. Examples of 3D-printed products are steak analogs, fish fillets, or protein-rich snacks [112; 118; 119; 120]. An emerging and relatively unknown technology in the realm of food technology is 4D printing. The use of 4D printing is an additive manufacturing technique and is an extension of 3D printing. Furthermore, 4D printing is similar to 3D printing in design development and printing structures with a 3D printer [121; 122]. The main differences between 4D and 3D printing are smart design and smart materials, as 4D printed structures can change shape or function [123]. Food can change color, texture, flavor, and shape when influenced by various stimulants such as temperature and pH. Therefore, it saves space in the transport process or adjusting the printed materials to the customers' needs.