A gas-phase colorimetric sensor for the detection of amine spoilage products in packaged fish

In this work, the design and application of a colorimetric amine sensor is detailed. The sensor consists of a pH indicator dye immobilised within a rugged, gas-permeable polymer film. The visual transition can be monitored quantitatively using a custom-built LED probe, or qualitatively with the human eye (i.e. using a colour code). Incorporation of several indicator dyes allows the monitoring of pH over an extended range and the sensor also has many potential applications in gas phase analysis (6 ppm LOD for ammonia). In this case, the sensor has been tailored to monitor TVB-N (total volatile basic nitrogen) spoilage products in the headspace of packaged fish. As the fish spoils, a colour change results as the TVB-N compounds shift the pH to higher values. This provides a non-invasive and simple method of rapidly detecting spoilage of produce inside sealed packaging. In trials to date, the sensor response has been found to mirror the progress of microbial spoilage.