The authenticity of vegetable oils consumed in Slovenia and Croatia was
investigated by carbon isotope analysis of the individual fatty acids by
the use of gas chromatography-combustion-isotope ratio mass spectrometry
(GC/C/IRMS), and through carbon isotope analysis of the bulk oil. The
fatty acids from samples of olive, pumpkin, sunflower, maize, rape,
soybean, and sesame oils were separated by alkaline hydrolysis and
derivatized to methyl esters for chemical characterization by capillary
gas chromatography/mass spectrometry (GC/MS) prior to isotopic analysis.
Enrichment in heavy carbon isotope (C-13) of th, bulk oil and of the
individual fatty acids are related to (1) a thermally induced
degradation during processing (deodorization, steam washing, or
bleaching), (2) hydrolytic rancidity (lipolysis) and oxidative rancidity
of the vegetable oils during storage, and (3) the potential blend with
refined oil or other vegetable oils. The impurity or admixture of
different oils may be assessed from the delta C-13(16:0) VS. delta
C-13(18:1) covariations. The fatty acid compositions of Slovenian and
Croatian olive oils are compared with those from the most important
Mediterranean producer countries (Spain, Italy, Greece, and France).