Exploiting the Thermotropic Behavior of Hydroxypropyl Cellulose to Produce Edible Photonic Pigments

Hydroxypropyl cellulose (HPC) is a widely commercialized cellulose derivative. While it is typically used as a binder or stabilizer for foods and pharmaceuticals, it can also form a cholesteric liquid crystal in aqueous solution. Moreover, at high HPC concentrations this lyotropic and thermotropic mesophase is known to reflect structural color. However, it remains a challenge to retain this vibrant coloration into the solid state. Herein, by combining the emulsification of a HPC mesophase with drying at elevated temperature, solid microparticles are produced that can reflect color across the visible spectrum, from blue to green and red. This method provides a facile and scalable pathway to fabricate structurally colored, edible pigments, which can displace existing synthetic additives used in a wide range of foods and cosmetics.

Automated summary

Hydroxypropyl cellulose (HPC) is a widely used cellulose derivative that can form a cholesteric liquid crystal and exhibit structural color at high concentrations. By emulsifying the HPC mesophase and drying it at elevated temperature, solid microparticles reflecting color across the visible spectrum can be produced. This method provides a scalable pathway to fabricate structurally colored, edible pigments, which can replace synthetic additives used in various foods and cosmetics.