Non-destructive visual detection of fresh food spoilage

Two coumarin derivatives SWJT-33 and SWJT-34 were synthesized as probes for the detection of cadaverine (Cad). Among them, SWJT-34 exhibits high selectivity and low detection limits for Cad using fluorescence or UV-vis spectrum. The detection limits for Cad were calculated to be 0.018 μM by fluorescence spectrum and 0.34 μM by UV-vis spectrum, which was much lower than those of most of reported probes. The probe could realize colorimetric and ratiometric detection of Cad because an aza-Michael addition reaction occurred between SWJT-34 and Cad to form the Schiff base compound as a product. In addition, SWJT-34 could be fabricated as portable test strips for the selective detection of Cad in vapor, and the corresponding detection limits were calculated to be 1.88 ppm in the fluorescent mode and 57 ppm in UV-vis mode, respectively. Additionally, these test strips could be used to test the freshness of Rottweiler shrimp and pork at different temperatures.