CHARACTERIZATION OF OLIVE OIL BY CARBON-ISOTOPE ANALYSIS OF INDIVIDUAL FATTY-ACIDS - IMPLICATIONS FOR AUTHENTICATION

The fatty acids of olive oils of distinct quality grade from the most important European Union (EU) producer countries were chemically and i sotopically characterized. The analytical approach utilized combined c apillary column gas chromatography-mass spectrometry (GC/MS) and the n ovel technique of compound-specific isotope analysis (CSIA) through ga s chromatography coupled to a stable isotope ratio mass spectrometer ( IRMS) via a combustion (C) interface (GC/C/IRMS). This approach provid es further insights into the control of the purity and geographical or igin of oils sold as cold-pressed extra virgin olive oil with certifie d origin appellation. The results indicate that substantial enrichment in heavy carbon isotope (C-13) of the bulk oil and of individual fatt y acids are related to (1) a thermally induced degradation due to deod orization or steam washing of the olive oils and (2) the potential ble nd with refined olive oil or other vegetable oils. The interpretation of the data is based on principal component analysis of the fatty acid s concentrations and isotopic data (delta(13)C(oil), delta(13)C(16:0), delta(13)C(18:1)) and on the delta(13)C(16:0) vs delta(13)C(18:1) cov ariations. The differences in the delta(13)C values of palmitic and ol eic acids are discussed in terms of biosynthesis of these acids in the plant tissue and admixture of distinct oils.