Towards an understanding of the structuring mechanisms of 3D printed flour-based matrices

3D food printing with flour-based doughs remains challenging due to the complex interactions between starch, proteins, and dietary fibers in unfractionated raw materials. This study investigated the structural, rheological, and printing properties of six flour-based doughs (formulated with wheat, rye, rice, red kidney bean, lupin, and chia flours) subjected to a two-step pre-printing process at constant hydration. The doughs exhibited a wide viscosity range, from a few to several hundred Pa ⋅ s at 10 s − 1 , reflecting differences in structural organization. Back-extrusion measurements showed strong agreement with shear rheometry for estimating apparent viscosity ( r > 0 . 978 ), and proved useful for comparing the apparent viscosities of different products under similar flow conditions, particulary for materials that could not be reliably analyzed by conventional rheometry. Confocal microscopy revealed distinct structuring elements depending on flour type. This multi-scale approach allowed for the formulation of hypotheses regarding the rigidity of dispersed particles and their contribution to dough structure. Printability was governed by both viscosity and particle size. All extrudable doughs achieved a printing quality higher than 90%. The collapse of the red kidney bean-based printed structure was associated with lower stress values at the G ′ = G ′ ′ crossover, indicating insufficient structural strength. These results provide insight into the multi-scale factors controlling structure formation, flow behavior, and printing performance of flour-based doughs for extrusion-based 3D food printing. • Back extrusion is a valuable alternative to shear rheometry for estimating the apparent viscosities of pasty doughs (r ¿ 0.978). • Collapsing of the red kidney bean-based printed product was associated with lower stress values at the G ′ = G ′ ′ crossover. • The confocal microscopy observations highlighted the different structuring elements of the studied doughs. • The multi-scale approach used allows to formulate hypotheses about the rigidity of the dispersed elements.