Precise Extrusion of Sweet Potato (Ipomoea batatas L.) Starch Sol Filaments: Printability Analysis and Process Optimization

Three-dimensional (3D) food printing, a relatively new food-processing method, was explored using gelatinized sweet potato starch (SPS) as a food ink. Prior to the production of intricate 3D shapes, this study focused on the precise extrusion of filaments, specifically the optimization of the printing conditions for nozzle diameters of 1.5 and 4.0 mm to produce filaments with an acceptable appearance and size. The rheological and mechanical properties of the (SPS) sol were also determined to describe the extrudability and shape retention of the food materials. The optimization process employed the Response Surface Methodology (RSM) and a desirability function to generate mathematical models of the width and height of the filaments as functions of the moisture content, the print temperature, and the print speed. The generated mathematical models were used to determine the optimum printing conditions. Hence, for the 1.5 mm nozzle, the optimum condition was at 82% moisture content, 57 °C print temperature, and 10 mm/s print speed, with a desirability of 0.842. In contrast, for the 4.0 mm nozzle, the optimum condition was at 82.3% moisture content, 50 °C print temperature, and 5 mm/s print speed, with a desirability of 0.911. The optimized filaments are expected to be used in 3D food printing to create 3D shapes.