Authentication of vegetable oils by bulk and molecular carbon isotope analyses with emphasis on olive oil and pumpkin seed oil

The authenticity of vegetable oils consumed in Slovenia and Croatia was inv estigated by carbon isotope analysis of the individual fatty acids by the u se of gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/I RMS), 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 ester s for chemical characterization by capillary gas chromatography/mass spectr ometry (GC/MS) prior to isotopic analysis. Enrichment in heavy carbon isoto pe (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 blen d with refined oil or other vegetable oils. The impurity or admixture of di fferent 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).