Low content of saturated fats and cholesterol and high content of polyunsaturated fatty acids (PUFA) makes fish an indispensable element of a healthy diet. On the other hand, its high moisture content and weak muscle tissue does not allow the long-term storage. Freezing is the most commonly applied preservation method used for extending the shelf life of fish. Improper practices of freezing and thawing, results with undesirable textural and functional changes, which mostly cannot be realized by consumers. Enzymatic and chemical changes as well as dielectric properties of fish samples were monitored in many studies in order to differentiate fresh and frozen-thawed fish samples. Fourier-transform infrared spectroscopy, impedance spectroscopy and near infrared spectroscopy are frequently used novel technologies with the advantages like rapidness and on-site usability.<br/>As one of the vibrational methods, which gives structural information and requires no sample preparation Raman spectroscopy is used in the present study in order to differentiate fresh and frozen-thawed fish samples. Unlike the reported studies, relatively short freezing (24h) and thawing (12h) periods were used in the present study. By using the advantage of its high sensitivity, very little changes in the lipid structure, which occurred during the very short storage periods, were monitored using Raman spectroscopy. Collected Raman data was analyzed by using Principal Component Analysis (PCA). Developed PCA models allowed us to obtain a successful differentiation between fresh, once frozen-thawed and twice frozen-thawed fish samples. Gas chromatography (GC) was used as reference method and fatty acid composition of fish samples were determined by GC analysis. A correlation was established between the results of GC and Raman spectroscopy in terms of changes in the lipid structure.

Evaluating Raman spectroscopic data by using principal component analysis to determine the freshness of fish samples

251st National Meeting (2016)

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