Oil and Fat Classification by FT-Raman Spectroscopy

One hundred and thirty-eight edible oil and fat samples from 21 different sources, either vegetable (Brazil nut, coconut, corn, high oleic sunflower, olive oil, peanut, palm, palm kernel, rapeseed, soybean, sunflower, etc.) or animal (butter, hydrogenated fish, and tallow) have been analyzed. The spectral features of the most noteworthy bands are studied, and their correlations with the amount of fatty acids quantified by gas chromatography are presented. Principal component analysis is applied to classify the set of samples by their level of unsaturation saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA). The most remarkable MUFA and PUFA oil sources are independently classified by applying stepwise linear discriminant analysis to the Raman shifts selected by their correlation with fatty acids or structural assignments. The results show that FT-Raman spectra not only have information of the degree of unsaturation but also of the balance among the amounts of SFA, MUFA, and PUFA. The scattering intensities near different Raman shifts (3013, 1663, and 1264 cm-1) show high correlations with the fatty acid profile determined by gas chromatography. Keywords: Oils and fats; FT-Raman spectroscopy; chemometrics