Mid-infrared spectroscopy as a new tool for the evaluation of fish freshness

Frozen fish usually have a much lower market price than fresh fish, hence, adulteration could occur. This paper focuses on the use of mid-infrared (MIR) spectroscopy combined with chemometric tools to determine whether fish has been frozen-thawed. A total of twenty-four fish samples (fresh fish (n = 12) and frozen-thawed fish (n = 12)) were investigated. The principal component analysis and the factorial discriminant analysis were applied to the three spectral regions in the MIR of 3000-2800 cm(-1), 1700-1500 cm(-1) and 1500-900 cm(-1). Within the 1500-900 cm(-1) spectral region, correct classification (CC) of 100% and 75% was observed for the calibration and validation spectra, respectively. Improved classification was obtained from the 3000-2800 cm(-1) spectral region, with CC of 100% and 87.5% of the calibration and validation spectra, respectively. It can be concluded that the 3000-2800 cm(-1) and 1500-900 cm(-1) spectral regions may provide useful fingerprints allowing the differentiation between fresh and frozen-thawed fish. These regions can be considered as a reliable indicator of fish freshness.