Formulation and Characterization of Fucoidan‐Based Hydrogels for 3D Printing Applications

Hydrogels based on algal polysaccharides have attracted increasing attention as inks for extrusion‐based 3D food printing. In this study, fucoidan (FU), extracted from Sargassum cymosum C. Agardh, was combined with sodium alginate (SA) and agar (AG) to develop a printable hydrogel formulation. Three formulations were prepared (1% FU, 1% AG, and 3% SA; 1% FU, 2% AG, and 2% SA; and 1% FU, 3% AG, and 1% SA) and characterized through rheological, physicochemical (zeta potential [ZP], hydrodynamic diameter [ D h ], and polydispersity index [PDI]), and structural analyses (attenuated total reflectance Fourier transform infrared spectroscopy [ATR‐FTIR] and scanning electron microscopy [SEM]). The polymer matrices were subjected to strand extrusion tests, followed by 3D printing of cubic models, which were evaluated for printing accuracy, physical stability, and texture. All formulations exhibited pseudoplastic non‐Newtonian behavior ( n < 1), with distinct gelation temperatures and satisfactory physical stability. The formulation containing equal concentrations of SA and AG showed promising results for ZP (−25.5 ± 2.47 mV), D h (3.70 ± 0.02 μm), and PDI (0.48 ± 0.11). Moreover, it exhibited the highest structural recovery (79.6%) and enhanced intermolecular interactions among carboxyl, sulfate, and hydroxyl groups. SEM micrographs revealed a lamellar microstructure, with pore formation at higher AG concentrations. Among the tested samples, the formulation containing 1% FU, 2% SA, and 2% AG showed superior printability during strand extrusion tests and 3D printing, producing structures with high accuracy, good physical stability, and a soft texture. These results demonstrate the potential of this combination of algal polysaccharides to develop hydrogels suitable for extrusion‐based 3D printing.