Chemometric differentiation of sole and plaice fish fillets using three near-infrared instruments

Fish species substitution is one of the most common frauds all over the world, as fish identification can be very challenging for both consumers and experienced inspectors in the cases of fish sold as fillets. Along the fishery production chain, one of the most vulnerable food chains [1], species replacement can often occur [2–4]: indeed, the difficulties in distinguishing among different species may generate a “grey area” in which mislabelling can occur. Thus, the development of fast and reliable tools able to detect such frauds in field is of crucial importance. In this study we focused on the distinction between two flatfish species largely available on the market, namely the Guinean sole (Synaptura cadenati) and European plaice (Pleuronectes platessa), which are very similar looking. Fifty fillets of each species were analysed using three near-infrared (NIR) instruments: the handheld SCiO (Consumer Physics), the portable MicroNIR (VIAVI), and the benchtop MPA (Bruker). Exploratory principal component analysis (PCA, [5]) models and classification partial least squares–discriminant analysis (PLS-DA, [6]) models were built using the spectral datasets, and all three instruments provided very good results, showing high accuracy in classification: 94.1 % for the SCiO and MicroNIR portable instruments, 90.1 % for the MPA benchtop spectrometer. The good classification results of the approach combining NIR spectroscopy, and simple chemometric classification methods suggest great applicability directly in the context of real-world marketplaces, as well as in official control plans.