Mid-infrared spectroscopy enabled rapid differentiation between fresh and frozen–thawed Sevruga (Acipenser stellatus) samples presenting different raw quality.

Freezing is the most commonly used technology to preserve the quality of fish and extend its shelf-life. The fish subjected to freezing and thawing processes could be sold as unfrozen ones. In this study, the ability of mid-infrared spectroscopy (MIR) to differentiate between fresh Sevruga (Acipenser stellatus) samples (F) kept up to 13 days at 4 °C from: (i) frozen–thawed (2 weeks at − 20 °C), then refrigerated up to 10 days at 4 °C (F-T R), and (ii) refrigerated up to 13 days at 4 °C, then frozen–thawed (2 weeks at − 20 °C) (R F-T) Sevruga samples was investigated. The application of factorial discriminant analysis (FDA) to the concatenated three spectral regions in the MIR (3000–2800 cm−1, 1700–1500 cm−1 and 1500–900 cm−1) allowed to distinguish clearly between samples according to their storage time, regardless of the quality of raw Sevruga samples since correct classification rate amounting to 92.16% was obtained. The electrophoresis analysis indicated that proteins undergo oxidation and degradation during storage impacting their secondary structure. For example, the level of the α-helix for Sevruga samples aged 1 day was 11.93%, 12.13%, and 11.83% for respectively F, F-T R, and R F-T groups that decreased throughout storage attaining on days 10 amounts of 11.90%, 11.70%, and 11.76%, respectively. It could be concluded that MIR spectroscopy could be used as a rapid screening tool to discriminate rapidly between fresh and frozen–thawed Sevruga fish, since 92.16% of correct classification was obtained. [ABSTRACT FROM AUTHOR]