Development status of 3D printing technology for food

Abstract: 3D printing, also known as additive manufacturing, has been used in many fields, such as medical, construction, automobile industries and so on. In recent years, 3D printing technology of food has developed rapidly, as with the diversification of the 3D printing forms related to that. This paper introduced the working principle, application range, advantages, limitations and market application of the extrusion, powder binding deposition and inkjet 3D printing. The extrusion-based printing was the most popular system in food printing. The multi-axis stages used in extrusion-based food printing included Cartesian, Delta, Polar and Scara configurations. There were 3 extrusion mechanisms which were used to extrude liquid or semisolid materials. The extrusion mechanisms were syringe-based extrusion, air pressure driven extrusion and screw-based extrusion. According to varied temperature control, the current extrusion-based food printer could be classified into room temperature extrusion, hot-melt extrusion and hydrogel-forming extrusion. For food 3D printing, except for extrusion-based printing, powder binding deposition was another common system. This category could be divided into 3 sub-types: Selective Laser Sintering (SLS), Selective Hot Air Sintering and Melting (SHASAM) and Liquid Binding (LB), which have in common the powder deposition in bed. And 3 properties of food materials related to critical factors were suggested here for the rational design of 3D food structures. They were printability, applicability and post-processing of the food materials. The printability for extrusion-based 3D printing mainly referred to the rheology, thermal (melting point and glass transition temperature) and gel properties of materials. For the powder binding deposition, the printability mainly referred to the particle size distribution, bulk density, wettability and flow ability of materials. The applicability meant the stability of the designed shape in the 3D modeling, and whether the desired graphics could be obtained according to the predetermined program. Last, the post-processing refereed to the appearance stability of a printed product after baking, cooking and frying and this feature was related to the mechanical and thermodynamic properties of materials. At present, the factors restricting the development of food 3D printing technology were the limitations and liquidity of printing materials, the printing speed, the stability of the printed model and so on. Different materials had different effects on the processing characteristics of 3D printing. For extrusion-based printing, the gel property of starch could change the viscosity of paste material, thus affecting the printability and applicability of 3D printing. The material of rich cellulose might cause clogging of the nozzle, because of insufficient comminution, while fat could be used as a plasticizer or lubricant for materials. Different proteins had different effects on the rheological properties of paste materials, therefore, appropriate type and amount.of protein should be added to 3D printing material to change the flow characteristics according to the rheological characteristics of the demand. For powder binding deposition, the powder component was ideally bimodal or multimodal to allow for ease of spreading as well as to enhance adhesion. Smaller particles were filled in the middle of larger particles to form a more compact structure and reduce porosity. The D50 of materials was suitable between 20 microns and 100 microns. In the process of injection, the droplets of the binder needed to remain spherical, not towing and merging, and should keep a straight line at a certain speed, and fall accurately in a predetermined position. There was an urgent need that combined food 3D printing technology with food science and nutrition, in order to find a breakthrough in developing personalized products for different groups of people. First of all, according to the needs of the proportion of people's nutrition, we made recipes, and got the density of materials. Then, the volume needed for food was calculated according to the quality and the density of materials. Last, 3D modeling was made to get the nutritional customized food needed by the crowd. In summary, the food 3D printing would bring a new revolution to the food processing.