Formulation and Characterization of Edible Bigel Inks for Structuring Fat Alternatives in 3D-Printed Foods

Bigels (BGs) are promising biphasic systems for extrusion-based 3D food printing inks. In this study, BG inks were formulated by combining a 6% beeswax-4% monoglycerides oleogel (OG) with a 4% gelatin-1% guar gum hydrogel (HG). The BGs were formulated at OG:HG ratios of 10:90 up to 50:50. The effect of the OG:HG ratio on appearance, microstructure, extrusion, rheological and thermal characteristics was investigated to assess printability and shape fidelity. All formulations showed no signs of phase separation during storage, while changes in color were observed with increasing OG content, suggesting modifications in phase distribution and light-scattering behavior. Increasing the OG content induced a transition from OG-in-HG systems to a bicontinuous structure at a 50:50 ratio. All inks showed shear-thinning behavior (G' > G″) and viscoelastic properties suitable for 3D printing. BG with intermediate OG contents displayed moderate extrusion forces (7.27-9.00 N) and improved structural recovery (up to ≈60%), consistent with desirable printability and appropriate yield/flow points to ensure shape fidelity after deposition. Thermal analysis further confirmed the coexistence of OG and HG phases, ensuring structural integrity at printing temperature. These findings demonstrate the potential of BG as tunable, fat-reduced inks for 3D food structuring.