Thermographic and rheological characterization of viscoelastic materials for hot-extrusion 3D food printing

Thermoreversible food materials are suitable for hot-extrusion 3D food printing (HE-3DFP) to customize food designs and enable on-demand food production. A challenge of HE-3DFP is to control the material phase transition such that it melts to allow flow and extrusion and rapidly solidifies afterwards to obtain stable printed structures. We here report on the use of thermal imaging to simultaneously monitor material cooling and deformation of common thermoreversible food materials during HE-3DFP. Thermographic and rheological measurements show that the structural deformation is driven by slow material cooling and prolonged printing time. The surface temperature of printed objects is a good indicator for structural stability. Solidification mechanisms such as cross-linking or strong particle jamming are required to prevent deformation in time (i.e. creep) during printing. Thus we recommend to set the printing temperature just above material's gelation temperature to ensure proper extrudability and structural stability of the printed foods.