Depletion attraction driven formation of Spirulina emulsion gels for 3D printing

3D printing has been applied to create nutritious foods with tailored textures for the elderly. However, the edible materials that possess the elastoplastic properties and shear-thinning behavior required for direct-write 3D printing are limited. In this study, we developed a simple approach to fabricate Spirulina emulsion gels as edible 3D printable material by exploiting depletion attraction between emulsion droplets. By controlling the volume ratio of continuous and oil phases, mixing highly viscous Spirulina slurry and vegetable oil could form selfstanding oil-in-water emulsion gels with elastoplastic rheological properties. Also, adding food polysaccharides into the continuous phase could act as depletants to drive the formation of emulsion gels. Autofluorescence spectroscopy and microscopy were employed to characterize the interfacial protein compositions of the emulsion, showing that phycobilisome (PBS) particles might play a dominant role in the formation of Spirulina emulsions. The depletion attraction could drive the adsorption of PBS particles onto the droplet interface, and the particle-armored droplets in the dispersed phase connected into a percolating droplet cluster, resulting in arrested dynamics and gelation. Overall, this novel approach can be applied by exploiting depletion attraction and opens up possibilities for using high-solids viscous food slurries to produce personalized 3Dprinted foods.