Extrusion-Based 3D Printing of Germinated Brown Rice Gel: Multi-Response Optimization of Process Parameters for Printing Fidelity and Hardness

Germinated brown rice (GBR) is a nutrient-dense whole grain, yet its coarse texture limits consumer acceptance. Three-dimensional (3D) food printing offers a promising strategy for structural reconstruction and value-added processing of GBR. This study investigated the effects of process parameters (nozzle movement speed, outer layer quantity, infill density, and nozzle diameter) on the printing fidelity and hardness of GBR gel. Single-factor experiments were conducted to determine reasonable parameter ranges, and response surface methodology was then used to model parameter interactions and optimize the process settings. In the single-factor tests, all four parameters significantly affected the two responses. Infill density and nozzle diameter were the dominant factors governing hardness, whereas printing fidelity was governed primarily by infill density, with nozzle diameter acting through significant quadratic and interaction effects. Numerical optimization identified the optimal settings as a nozzle movement speed of 25 mm/s, an outer layer quantity of 4, an infill density of 76%, and a nozzle diameter of 1.5 mm, achieving 94.64% printing fidelity and 314.16 g hardness with prediction errors below 2%. These findings establish a quantitative parameter framework for 3D food printing of this GBR gel and provide a reference for other cereal-based gel systems.