Paper Sensors for Advanced Smart Packaging: Route to Detection on the Shelf and in Real Ambient

Smart packaging technologies have been increasingly developed to monitor and control food spoilage, ensuring food safety and quality throughout the supply chain. In this work, we consider a flexible, low-cost sensor based on hygroscopic properties of cellulose fibers for the detection of water-soluble gases produced from the degradation of amino acids in protein-rich food like fish and meat. Ammonia and ammonia-related compounds such as dimethylamine and trimethylamine have gained increasing attention as volatile markers of the spoilage process, but owing to the complexity of a food matrix, technology validation requires testing with odors released by food samples instead of individual or a few marker compounds. Here, we realized carbon electrodes by aerosol jet printing (AJP), with subsequent annealing at room temperature by flash lamp annealing (FLA), necessary to avoid cellulose substrate damaging. Subsequently, the sensors were tested in real environment with codfish filet and cross-checked with conventional microbiological tests to assess the reaching of edibility threshold of the fish at room temperature. The sensors lodged in the food package were compared with sensors lodged in the reference package containing distilled water. The developed technology confirmed that it is possible to monitor fish degradation along the reaching and overpassing of the edibility threshold (mean sensors’ relative response is 50% at $10^{{7}}$ CFU/g) after 11 h at $25~^{\circ }$ C, with a low-cost disposable device that can be integrated into food packaging.