ATR-FTIR and raman spectroscopies associated with chemometrics for lipid form evaluation of fish oil supplements: A comparative study

Omega-3 fatty acids (FAs) are mainly available as triacylglycerols (TAGs) and ethyl esters (EEs) in fish oil supplements, and it is known that EEs are less bioavailable than TAGs in the human body. This study applied attenuated total reflectance with Fourier transform infrared (ATR-FTIR) and Raman spectroscopies associated with chemometrics to evaluate the supplements’ lipid form. Representative products were first characterized by reference chromatographic methods. Subsequently, principal component analysis (PCA) and partial least square discriminant analysis were performed in the spectral wavenumber ranges 1700–1780 (ATR-FTIR) and 1720–1770 cm–1 (Raman). TAGs and EEs were clearly distinguished along PC1 by employing both techniques, but a higher explained variance was obtained by ATR-FTIR. The prediction of TAG and EE fish oil samples was also better using ATR-FTIR (R2 = 0.99 versus 0.95 for Raman). However, both models correctly classified 100% of the samples, which indicates the suitability of these approaches to be used in quality control laboratories aiming for fish oil lipid form evaluation.