Analysis of Pumpkin Paste Printability for Screw-Based 3D Food Printer

Extrusion-based 3D food printers are the most widely used 3D food-printing machines. Among these, screw-based 3D food printers have insufficient knowledge of printability compared to other types of extrusion-based printers. This study aimed to analyze the extrudability and shape stability immediately after printing from the viewpoint of mechanics using a screw-based 3D food printer. A paste comprising pumpkin flakes and water was used as the model food ink. The results show that 3D printing can be stable in the flake content of 20.0-28.6 wt%. When the pumpkin flake content was 18.2 wt% or lower, the 3D-printed food was flattened, and when the flake content was 30.8 wt% or higher, the paste was difficult to extrude from the nozzle. The results suggest that extrudability is mainly affected by the loss tangent of the paste and the balance between the apparent viscosity and inner nozzle pressure. Moreover, the main factors for shape stability immediately after printing were Young's modulus and the balance between the stress applied to the printed food owing to its weight and the yield stress of the paste. Particularly, it was found that the screw-based 3D food printer has a unique characteristic in controlling extrudability compared to other extrusion-based printers because the inner nozzle pressure tends to fluctuate depending on the apparent paste viscosity. The findings of this study provide new fundamental insights into screw-based 3D food printers from viewpoints of fluid and structural mechanics.