One stone, four birds: Deep eutectic solvents serve multiple functions in the development of flexible smart tag for monitoring the freshness of high-protein food

In this study, a facile “one stone, four birds” strategy was implemented to fabricate a flexible smart food packaging tag by incorporating purple potato extract obtained using deep eutectic solvents (DESs) into a polyvinyl alcohol (PVA)/gelatin (Gel) substrate. The favorable properties of DESs enabled them to serve four different important functions in tag development: anthocyanin extraction; mitigation of anthocyanin oxidation; as a plasticizer to increase the mechanical properties of the tag; and to enhance NH 3 sensitivity. The physicochemical, microstructural, and functional properties of the tag were characterized using various methods. Moreover, density-functional theory (DFT) was used to calculate the adsorption energies for NH 3 at multiple sites on the DES. The tag was employed to monitor the freshness of shrimp and fish, whereby it underwent conspicuous color changes during 10 h of storage, which enabled classification of the products as fresh, sub-fresh, or spoiled. Overall, the developed flexible smart tag shows significant potential for application in monitoring the freshness of high-protein food.