Purity assessments of major vegetable oils based on δ¹³C values of individual fatty acids

The fatty acid compositions and δ 13 C values of the major fatty acids of more than 150 vegetable oils were determined to provide a database of isotopic information for use in the authentication of commercial maize oil. After extraction of oils from seeds, nuts or kernels, and methylation, fatty acid compositions were determined by capillary gas chromatography. All compositions were within the ranges specified by the Codex Alimentarius. Gas chromatography combustion‐isotope ratio mass spectrometry was employed to determine the δ 13 C values of the major fatty acids of the oils. A large number of pure maize oils and potential adulterant oils from various parts of the world were studied to assess the sources of variability in δ 13 C values. Such information is vital to establishing the compound specific isotope technique as a reliable means of assessing vegetable oil purity. Variability in δ 13 C values was related to the geographical origin of the oil, year of harvest, and the particular variety of oil. This suggests that the ultimate δ 13 C values of fatty acids are determined by a combination of environmental and genetic factors.