Integrating fiber modification and computer-vision evaluation to improve soybean meal for 3D food printing

Soybean meal has potential as a sustainable 3D-printing ingredient, but its high insoluble dietary fiber content limits gelation, extrusion, and overall printability. In parallel, the field lacks rapid, objective methods to quantify printability, as most assessments rely on subjective visual scoring or simplified extrusion tests that do not reflect practical printing performance. To address these challenges, a combined ball-milling and enzymatic-hydrolysis strategy was introduced to modify the fiber and improve printability. A computer-vision workflow was also implemented to quantitatively evaluate extrusion fluidity (Extrudability Index, EI) and shape fidelity (Surface Index, SI). Using a full factorial design, the effects of milling, solids concentration (25-35 %), and hydrolysis time (0-24 h) on rheology, fiber composition, and printing performance were systematically investigated. Results showed that the ball milling treatment significantly reduced the EI. Elevated solid concentration generally lowered the EI, SI, and the printability (Printability Index, PI), whereas enzymatic treatment, especially at higher solid concentrations (≥30 %), could mitigate this effect. Elevated soluble/insoluble dietary fiber increased storage modulus, loss modulus, and viscosity, hindering printability by reducing EI and SI, while ball milling partly counteracted it in the rheological properties, but did not significantly impact the PI. Enzymatic hydrolysis degraded non-gelling fibers, thereby enhancing EI, SI, and overall PI. The sample concentration, ball-milling treatment, and enzymatic hydrolysis significantly influenced the texture of printed products. Overall, this study links fiber modification to rheological behavior and printing outcomes, and demonstrates an operator-independent, high-throughput approach for evaluating and tuning plant-based 3D-printing inks.