Liquid–liquid phase separation as a structuring tool for designing anisotropic food systems

Abstract

Liquid–liquid phase separation (LLPS) is a key mechanism in the formation of biomolecular condensates in cells and provides a versatile framework for structuring soft materials. In food systems, LLPS spans applications from droplet-based compartmentalisation (e.g., microencapsulation by complex coacervates and droplet microreactors) to flow-induced alignment strategies that generate anisotropic textures. This review examines the associative LLPS (coacervate dispersions), and segregative LPPS (aqueous two-phase systems) through the lens of deformation, relaxation and arrest. For coacervates, bulk viscosity is interpreted using deformable-droplet rheology. I then summarise the state of the art in coacervate-derived hydrogel fabrication. For segregative systems, polymer− demixing coupled with shear and controlled arrest enables alignment, string formation, and phase inversion prior to solidification. Across scales from single droplets to bulk flow, physics-based descriptors such as capillary number Ca, viscosity ratio λ, and Weissenberg number Wi, are linked to image-derived orientation metrics to connect in-flow deformation and droplet arrest to the final structure. The analysis delineates governing mechanisms, processing windows, and limitations that define when LLPS yields an aligned microstructure and fibrous texture under practical conditions.