Tailoring the rheology, structural stability and printability of pea protein–κ-carrageenan hydrogels with Tremella fuciformis polysaccharide for 3D food printing

Extrusion-based 3D food printing enables the manufacture of personalized foods with tailored shapes, rheology and nutritional profiles. However, plant-protein-based inks often suffer from weak gel networks, poor shape retention and limited post-printing stability. This study developed pea protein isolate (PPI)–κ-carrageenan (κC) composite hydrogels containing different concentrations of Tremella fuciformis polysaccharide (TFP; 0–2%, w/w) to improve their printability and physicochemical performance. The impact of TFP reinforcement on rheological and mechanical attributes, microstructure, molecular interactions, crystalline-amorphous organization, and thermal stability was investigated using 3D printing trials, rheometry, texture profile analysis, SEM, FTIR, X-ray diffraction, DSC, and TGA analysis. All hydrogel formulations exhibited shear-thinning behaviour, confirming their suitability for extrusion-based printing. TFP incorporation reinforced the viscoelastic network, enhanced rheological properties and improved printed shape fidelity compared with the PPI–κC control. Among the tested formulations, the hydrogel containing 1% TFP showed the best overall printing performance, characterized by continuous extrusion, smooth filament formation, good layer stacking, and improved structural integrity after printing. Rheological, structural, and molecular docking interaction analysis indicated that TFP promoted non-covalent interactions, mainly hydrogen bonding and electrostatic interactions, resulting in a more cohesive polymer network. FTIR analysis suggested secondary-structure rearrangement of PPI within the composite matrix, while XRD, TGA, and DSC analyses confirmed modified molecular ordering and enhanced thermal stability after TFP incorporation. Overall, these findings demonstrate that TFP is an effective natural polysaccharide for improving the printability and structural functionality of PPI–κC hydrogels, providing a promising strategy for developing sustainable, novel edible food ink for extrusion-based 3D food printing.