Classification of Tunisian extra virgin olive oils according to their genetic variety and maturity index using fatty acid profiles established by direct infusion mass spectrometry

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 (Ch etoui 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.

A review: role of mass spectrometry in the quality and authenticity identification of olive oil

“…And through the characteristic fingerprints of different characteristic components, three kinds of oils are identified and distinguished. Fatty acid profiles, based on DIMS combined with linear discriminant analysis, were successfully established, which can be used for EVOO maturity and variety classification (Abdallah et al ., 2016). The different compositions of ESI spray solvents would affect the resolution and detection of sample compound composition.…”

Application of an electronic tongue for Tunisian olive oils’ classification according to olive cultivar or physicochemical parameters

“…Concerning the cultivar assessment of Tunisian olive oils, several works can be found in the literature, based on traditional analytical techniques coupled with different multivariate statistical approaches. Abdallah et al [12] used fatty acid data obtained by direct infusion mass spectroscopy to classify Tunisian EVOO according to their genetic variety (Chemchali, Chemlali, Dhokar, Jemri, Fouji, Zalmati and Zarrazi) and maturity index. The results showed that olive oils could be correctly classified (100%) according to olive cultivar based on linear discriminant analysis (LDA) models.…”

“…To overcome difficulties concerning the direct potentiometric analysis of olive oil, the evaluation was performed in hydroethanolic extracts supposedly rich in polar compounds, which contents are highly dependent on the olive cultivar [14,15,29]. Indeed, olive oils produced from a single olive cultivar (monovarietal oils) have specific physical and biochemical characteristics [12]. The potential response of the E-tongue towards polar compounds of olive oils was further checked by determining the sensitivities of each sensor towards standard solutions of chemical compounds related to sensory attributes perceived in olive oils, namely, aldehydes, esters and alcohols.…”