Edible cellulose-based colorimetric timer

A biocompatible and edible colorimetric timer is obtained by exploiting the dynamic colour changes of the cholesteric liquid crystalline mesophases of hydroxypropyl cellulose (HPC) in aqueous suspensions. The edible timer is encapsulated between semi permeable membranes made of shellac. The cholesteric organisation of the HPC provides vibrant colouration, while the shellac layers allow tuning of the evaporation rate of water from the mesophase, which results in a colour change. Due to the biocompatibility of the components and the direct read-out of the system, i.e. the colour change can be visually detected, and the developed timer can be implemented as a colorimetric sensor with potential to be used in food packaging, and as a smart labelling system.