Use of chromatography, spectroscopy and chemometrics for evaluation of cold-pressed oils

The recent increase in imitation and adulteration in food requires the control of cold-pressed oils in the market. The cold-pressed oils of these seeds (coconut, Nigella sativa, , flaxseed, sesame seed) contain essential fatty acids and the fatty acids and sterol compositions are the most essential features that distinguish these oils. Chromatography and spectroscopy methods were applied in this study. Fingerprints of four reference materials obtained from coconut, black cumin, flaxseed, and sesame were determined using FTIR and Raman spectroscopy, and their fatty acids and sterol compositions were determined using GC-FID. The spectroscopic and chromatographic results of 20 cold-pressed oils supplied from the market were compared with these reference oils. Results showed differences in the values of sterol and fatty acid compositions between the reference oils and the oils supplied from the market. In the Raman and FTIR spectroscopy method, spectra describing the chemical structure of oils as fingerprints were obtained, and these spectra supported the differences in GC-FID results. The study results show that the chromatographic and spectroscopic methods are references for each other and provide information about whether the oils offered for sale in the market differ from reference oils and each other.