Polydiacetylene-based sensors to detect food spoilage at low temperatures†
Colorimetric gas sensors that detect early release of gases from food spoilage are of great importance in food safety and food conservation. Yet, such sensors are not broadly implemented as they are incompatible with food packaging and non-functional at the low temperatures at which food is stored. Here we report a low cost, highly sensitive ammonia sensor that can be easily incorporated into food packaging to monitor food spoilage at temperatures ranging between −20 °C and room temperature. To fabricate the film sensors, we polymerized self-assembled polydiacetylene vesicles stabilized with cellulose nanocrystals in chitosan matrix. By optimizing this fabrication process, we were able to increase the local concentration of polydiacetylene vesicles at the surface of the film, thus enhancing the operational temperature, response time, and sensitivity to ammonia. The polydiacetylene-based film sensors exhibited a distinctive blue-to-red colorimetric response after being exposed to spoiled meat, even at sub-zero temperatures.