^a170Formation characteristics of 3D-printed food using sweet potato (Ipomoea batatas L.) starch gel

Al Kaxier Guzman Ancheta^1,2,3**, Hiroyuki Kozu², Takumi Umeda² , Marcos A. Neves⁴, Isao Kobayashi^2,5*

¹Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Ibaraki, Japan
²Institute of Food Research, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
³Department of Engineering Science, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, Laguna, Philippines
⁴Institute of Life and Environmental Sciences, University of Tsukuba, Japan
⁵School of Integrative and Global Majors, University of Tsukuba, Japan

Extrusion-based 3D food printing is a relatively new technology used to create intricate shapes layer by layer by precisely extruding a viscoelastic food material on a printing stage. The food material selected was sweet potato starch gel given that sweet potato starch is widely used as an ingredient in the food industry. However, the ability of gels to form intricate 3D shapes from initially extruded filaments has not been well studied. Therefore, this study aimed to investigate the effects of printing conditions on multilayer printing of sweet potato starch gel using an extrusion-based 3D food printer with different nozzle diameters.

We determined the printing conditions (i.e., moisture content of the gel, print temperature, print speed, and model filament width and height) appropriate for the precise extrusion of single filaments of sweet potato starch gel for each specified nozzle diameter of 1.5 mm and 4.0 mm. When 3D food printing of square prisms with a base area of 48 mm × 48 mm was performed using precisely extruded filaments, it was necessary to perform additional 3D printing modifications (i.e., nozzle clearances for the 1 ^st layer and succeeding layers, number of polygons per layer, and fill factor) for each nozzle diameter to improve the appearance of the 3D-printed material. As the number of layers increased, the lengths of the side of the top layer decreased gradually, whereas there was no significant difference between the lengths of the bottom layer side (Sp= 0.05). Consequently, the degree of flatness, which is the ratio of the length of the bottom layer to that of the top layer, increased linearly with the number of layers, illustrating the spreading of the hot gel in the top layer, whereas cooling and solidification occurred in the bottom layer.

Nevertheless, it is possible to create intricate 3D shapes using sweet potato starch gel following the selected printing conditions and recommended number of layers, which are 4 and 3 for the 1.5-mm and 4.0-mm nozzles, respectively, based on the results obtained from this study.