Polysaccharide-based screen-printed colorimetric sensor for amines detection in packaged fish

Generic expiration dates continue to serve as freshness indicators for highly perishable foods such as fish. In fact, "best before" dates are a prediction of the estimated limit of safe quality. Therefore, they do not provide real-time information of the fish freshness, resulting in an inaccurate assessment of its quality. In this work a colorimetric ink was developed to produce screen-printable and cost-effective paper and plastic sensors with high sensitivity to volatile amines, produced during fish spoilage. The pH-responsive ink was obtained by integrating anthocyanins in a polysaccharide matrix containing water-soluble chitosan and starch. The ratio between both polysaccharides was studied and it was shown that starch content up to 4 % provides the ink with the suitable viscosity to be screen-printed, leading to the production of saturated uniform sensors. To evaluate the long-term stability of the sensor, the optimal storage conditions were studied, revealing that humidity- and oxygen-free atmospheres were the most adequate to preserve color for 28 days. When exposed to different concentrations of trimethylamine, both plastic- and paper-printed sensors underwent noticeable color changes. Therefore, this polysaccharide-based sensor offers a promising alternative to conventional expiration dates, with screen-printing enabling scalable fabrication for sustainable food waste mitigation.