Geographical origin discrimination of “Ntopia” olive oil cultivar from Ionian islands using volatile compounds analysis and computational statistics

Abstract

The aim of the present study was to characterize the aroma profile of olive oil of the “Ntopia” (local) cultivar from the Ionian islands (Zakynthos, Kefalonia, Leukada, and Kerkyra) (Greece), and investigate whether specific volatile compounds could be considered as indicators of olive oil geographical origin, using computational statistics. In this context, 137 olive oil samples were subjected to headspace solid phase microextraction coupled to gas chromatography/mass spectrometry using the internal standard method. Computational statistics on the semi-quantitative data of olive oil samples, as rapid machine learning algorithms, showed that specific volatile compounds could be used as indicators of geographical origin of olive oil of the “Ntopia” cultivar, among the four main Ionian islands. Volatile compounds such as ethanol, pentanal, 2,4-dimethylheptane, 3,7-dimethyl-1,3,6-octatriene (E), 2,5-dimethylnonane, 1-hexanol, 6-methyl-5-hepten-2-one, octanal, dl-Limonene, acetic acid hexyl ester and dodecane could aid to the geographical origin discrimination of “Ntopia” olive oil cultivar when two (Zakynthos and Kefalonia) or four (Zakynthos, Kefalonia, Leukada and Kerkyra) Ionian islands are subjected to statistical analysis. The discrimination rate using the cross-validation method was 100% and 85.7%, respectively. These results were further evaluated using training and holdout partitions, during which a comparable classification rate was obtained. Supplementary Information The online version contains supplementary material available at 10.1007/s00217-021-03863-2.

A Study on the Clustering of Extra Virgin Olive Oils Extracted from Cultivars Growing in Four Ionian Islands (Greece) by Multivariate Analysis of Their Phenolic Profile, Antioxidant Activity and Genetic Markers

“…However, their samples came from geographical locations which are distant and probably have different climates. In the present study, all four islands are classified as “Csa” (hot dry-summer climates) according to the Köppen–Geiger climate classification system, as previously described in Eriotou et al [ 31 ]. Therefore, the present study provides stronger evidence for the association between cultivar and secoiridoid concentration for the Ionian Island cultivars.…”

“…Inclusion in the study was based on the selection criteria described in our previous work [ 31 ]. Briefly, 103 extra virgin olive oil (EVOO) samples were extracted from hand-picked olive fruits sp.…”

“…The rationale for this a priori sub-categorization is based on research on Italian and Spanish cultivars, showing that cultivated ancient trees are genetically distinct from cultivated younger trees [ 32 ]. Region, climate conditions, and cultivar information have been previously described [ 31 ].…”

“…Only mechanical methods were used to obtain olive oil in the laboratory. In brief, olives were crushed, pitted, ground, and malaxed for 30 min, as previously described [ 31 ]. Caution was taken so that the temperature during malaxation was always below 27 °C.…”

“…Consequently, there has been an increase in the implementation of multivariate statistical methods on multiple biochemical and biophysical numerical data to identify which characteristics could serve as quality and composition identity “markers” between EVOOs from cultivars of different origin. In a previous study by our group, it was shown that discrimination of olive oil by geographical origin was possible by implementing multivariate analyses on the volatile compound profiles of olive oils extracted from the Ntopia cultivars from four different Ionian Islands [ 31 ]. The aim of the present study is first to characterize the differences of individual secoiridoid derivative levels between the olive oil samples from cultivars grown on four Ionian Islands and to determine cultivar-specific phenolic profiles.…”