Physically structured emulsion-filled gels based on Euglena-xanthan depletion mixtures for 3D printing

The development of sustainable 3D-printable food systems requires soft materials that exhibit shear-thinning behavior during extrusion while maintaining structural integrity post-deposition. Here, we report a novel 3D-printable emulsion-filled gel system fabricated via in situ emulsification within a physically structured matrix formed by depletion interactions between Euglena gracilis biomass particles and xanthan gum (XG) polymers. Rheological analysis showed that these depletion interactions in aqueous dispersions produced weak colloidal gels with tunable viscoelasticity depending on the particle-to-polymer ratio. Incorporation of 40 wt% vegetable oil into the depletion mixtures through low-shear homogenization yielded stable, self-supporting emulsion-filled gels suitable for 3D printing. Interfacial measurements revealed that water-soluble components released from E. gracilis acted as endogenous emulsifiers, facilitating the formation and stabilization of finely dispersed oil droplets within the colloidal matrix. Large amplitude oscillatory shear (LAOS) measurements demonstrated that the embedded oil droplets contributed to increased gel strength and mechanical resilience, thereby enhancing extrudability and shape fidelity during 3D printing. This physically driven strategy eliminates the need for additional thermal or chemical treatments to produce gel matrix, providing a sustainable platform for developing functional, biocompatible soft materials suitable for personalized nutrition, advanced food structuring, and other edible applications.