Abstract
The usefulness of fatty acid profiles established by direct infusion mass spectrometry (DIMS) as a tool to discriminate between seven genetic varieties of Tunisian extra virgin olive oils (EVOOs) was evaluated in this work. Moreover, the discrimination of EVOOs from the genetic varieties Chemchali, Fouji, and Zarrazi, characterized with different maturity indices, was also studied. For DIMS, EVOO samples were diluted with an 85: 15 propanol/methanol (v/v) mixture containing 40 mM ammonia and directly infused into the mass spectrometer using a syringe pump. The establishment of ratios of the peak abundances of the free fatty acids followed by linear discriminant analysis was employed to predict both genetic variety and maturity index. In all cases, an excellent resolution between all category pairs was achieved, which demonstrated that fatty acid profiles are a good marker of both genetic variety and maturity index of EVOOs.
Practical applications: As EVOO quality can be affected by different parameters, such as cultivar and maturity index, among others, it is necessary to develop analytical methods able to verify EVOO quality, and also to control its origin as olive oil producers have to include in their manufactured products the cultivar (monovarietal oils) from which the oil was obtained. Currently, almost all the research related to Tunisian EVOOs has been mainly focused on the improvement and characterization of the two main cultivars (Chetoui and Chemlali). Thus, to diversify Tunisian olive oil resources and improve the quality of olive oil produced in Tunisia, research on additional cultivars needs to be conducted. Thus, the present method could be used as an authentication tool for olive oil industry to asses both cultivar and maturity index of Tunisian EVOO, which could be extended to EVOO from all around the world.