Immobilization of anthocyanin (butterfly pea flower) and nanocrystalline cellulose-supported polysiloxane into delignified wood to monitor food freshness

Intelligent packaging has been applied to detect the spoilage of foodstuff, offering a colorimetric indication to safeguard individuals from environmental and biological hazards. Nevertheless, synthetic sensors are toxic, challenging to manufacture, expensive, and non-biodegradable. This study reports a simple strategy toward an eco-friendly colorimetric hardwood that changes color upon exposure to rotten foods. Transparent hardwood with halochromic features was prepared by infusing a combination of anthocyanin (AC)/potash alum nanoparticles (NPs) and maleic-modified cellulose nanocrystal (CNC)-integrated polysiloxane (PS) into delignified wood. The anthocyanin biomolecule was extracted from Clitoria ternatea L. The mechanical properties of polysiloxane were improved with the use of CNC as a reinforcement agent. Furthermore, CNC (6–12 nm in diameter) served as a dispersant mediator to avert the clustering of the AC/Al NPs (45–180 nm). In reaction to heightened food spoilage, the anthocyanin receptor exhibited a blueshift from 568 nm (purple) to 438 nm (transparent).