A semiconducting metal-oxide array for monitoring fish freshness

An array of semiconducting metal-oxide (SMO) chemiresistive sensors can quantitatively measure the freshness of Atlantic salmon (Salmo salar), haddock (Melanogrammus aeglefinus), and Atlantic cod (Gadus morhua). A variety of SMO films were tested, including films containing oxides of copper and tin, and commercially available tin-based SMO films. Analytical testing of the fish samples was performed in conjunction with SMO sensor testing of the volatile gases emitted from the degrading fish. Testing included the use of a sensory evaluation panel and tests incorporating amine colorimetric methods, pH analyses, and bacterial aerobic and anaerobic plate counts. Sensory analysis, trimethylamine (TMA) content, pH, and aerobic and anaerobic plate counts provided results that correlated well with each other and with SMO sensor results. A radial basis function (RBF) neural network was designed and used to classify the day of fish degradation (1–15) from the SMO sensor array response.