Optimizing particle size for kudzu root-carrot-based inks: enhancing rheology, texture, and printability in 3D food printing

This study investigates the effects of particle-size on the 3D-printing characteristics of mixed inks formulated from freeze-dried kudzu root (Pueraria montana var. lobata (Willd.)), and carrot (Daucus carota L. subsp. sativus) powders, supplemented with soybean protein isolate and xanthan gum. The findings reveal that variations in particle size noticeably influence the ink microstructure, texture, and rheological properties. At kudzu root and carrot powder particle sizes ≤0.3 mm and ≤0.2 mm, respectively, ink hardness, viscosity, and storage modulus decrease, extrusion improves, but print precision and stability decline. Reducing the particle size improved printing accuracy but also increased the difficulty of extrusion. Inks with particle sizes ≤0.075 mm and ≤0.053 mm displayed intermittent extrusion and line breakage during printing, resulting in reduced precision. Among the formulations tested, the ink with a particle size ≤ 0.15 mm formed a stable, dense microstructure, yielding smooth lines and precisely defined surfaces on printed models such as pyramids, cubes, and caps. Pyramid models printed with ink using particle size ≤0.15 mm were measured using a ruler and SolidWorks software, showing precision levels of 98.85% and 99.53%, respectively. Furthermore, these printed models exhibited excellent stability over a 72 h period, maintaining dimensional accuracy with stability values of 98.12% and 98.01%.