Microstructural, textural and rheological properties of food-grade bigel inks designed for 3D food printing

Bigels have emerged as promising edible inks for three-dimensional (3D) food printing due to their ability to combine both a hydrophilic and lipophilic phase within a single structured matrix. In this study, food-grade bigels were developed by mixing beeswax-sunflower oil oleogels with a composite gelatin–agar hydrogel on varying oleogel-to-hydrogel ratios (10-90%). The effects of composition on stability, color, microstructure, texture, rheological properties, thermal behavior and printability were investigated. All formulations formed stable, self-supporting bigels without visible phase separation. Microstructural analysis revealed a composition-dependent structure shifting from oleogel-in-hydrogel structures to bicontinuous networks, followed by phase inversion to hydrogel-in-oleogel systems as the oleogel content increased. All inks exhibited shear-thinning behavior and solid-like viscoelasticity (G΄>G΄΄). Increasing oleogel content led to a progressive increase in the yield point and reduced structural recovery. Thermal analysis identified one exothermic transition and two endothermic peaks associated with agar, gelatin and beeswax, respectively, confirming the biphasic nature of the systems. Printability evaluation using a hexagonal model showed that hydrogel-rich ink formulations exhibited significant deformation after deposition, whereas increasing oleogel content enhanced structural rigidity. Bigel inks with 60-70% oleogel exhibited the highest dimensional fidelity, indicating an optimal composition that balances extrudability and self-support during extrusion-based 3D printing. These findings demonstrate that phase composition controls the structural and functional properties of bigels and provide a basis for designing optimized bigel-based inks for 3D-printed food applications. • Food-grade bigels were developed as printable inks for extrusion-based 3D printing. • Oleogel-to-hydrogel ratio-controlled structure, rheology and printability of bigels. • All bigel formulations showed solid-like and shear-thinning behavior. • Bigel inks with 60–70% oleogel showed optimal dimensional fidelity after printing.