Seven isomeric hydrocarbons were detected in the volatile fraction of three samples of virgin olive oil. Chemical ionization mass spectrometry was used to assign the molecular formulas. Their structures were confirmed by comparison of retention time and mass spectral data with those of a synthetic sample obtained by pentene radical coupling. A final characterization of each chromatographic peak was done by means of a chiral capillary column to distinguish the optically active compounds from the isomers without chiral centers. For the quantitation the recovery factor in the oily matrix during the extraction of the volatile fraction was obtained using a related chemical, the commercially available beta-citronellene. On the basis of the previous literature and the present experiments a tentative rationalization of the involved biochemical pathway is proposed.
Adulteration of olive oils can be detected by comparison of the
13C/12C ratios as obtained
subsequently
by high-resolution gas chromatography (HRGC) and isotope ratio mass
spectrometry (IRMS). In
δ13C values determined for the aliphatic alcoholic
fraction of pomace oil, the adulterant was
significantly more negative than those of virgin and refined olive
oils. Quantitative analysis of
isoprenoids and methylsterols isolated from each grade of olive oil
supports the decreasingly negative
values of 13C/12C ratios for the better grades
of olive oil. These results have turned out to be a
good
tool for detecting adulteration of olive oil with the cheaper pomace
olive oil, even down to a 5%
level.
Keywords: Carbon stable isotopes; olive oil; adulteration; aliphatic
alcohols; waxes
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