Study of the Cultivar−Composition Relationship in Sicilian Olive Oils by GC, NMR, and Statistical Methods

Abstract

The aim of this research is to find if there is direct evidence relating the fatty acid composition of olive oils to specific cultivars grown within a well-limited geographical region. To group olive oils according to their own cultivars,(13)C high-field nuclear magnetic resonance (NMR) and gas chromatography (GC) were used to analyze 60 extra virgin olive oils from the same Italian region (southwestern Sicily) obtained from four monovarietal cultivars. The (13)C NMR spectrum provides information about glycerol triesters of olive oils, i.e., about the acyl composition of major components and about the fatty acids' positional distribution on the glycerol moiety. GC gives the complete fatty acid profile of olive oil samples. Selection of NMR and GC peaks on the basis of their sensitivity to the different cultivars was performed by using multivariate analysis of variance (MANOVA). Principal component analysis, tree clustering analysis, multidimensional scaling (MDS), and linear discriminant analysis (LDA) were then performed on the MANOVA-selected peaks. Results obtained from (13)C NMR and GC techniques combined with the multivariate statistical procedure are in good agreement and prove the usefulness of fatty acids analysis to group the monovarietal olive oils belonging to the same cultivars. Grouping of olive oils according to their cultivars occurs for particular (13)C resonances all belonging to fatty chains in the sn 1,3 position of the glycerol moiety.

Characterization of several hazelnut (Corylus avellana L.) cultivars based in chemical, fatty acid and sterol composition

“…When comparing the fatty acid profile of olive oils from different countries [43][44][45] with the one herein reported for hazelnuts, they seem to be slightly different since in olive oil the second and third major fatty acids are always palmitic and linoleic acids, while in hazelnut oils this order is the inverted one. Consequently, total SFA content in hazelnuts is lower than in olive oils.…”

Chemometric Analysis of Croatian Extra Virgin Olive Oils from Central Dalmatia Region

“…17 There have been numerous studies over the years, attempting to establish a link between composition and geographical origin using a variety of instrumental analytical techniques, generally coupled with multivariate data analysis. [18][19][20][21][22][23] In particular, FTIR spectroscopy was shown to be an effective tool in the characterization, geographical classification [24][25][26] or authentication of vegetable oils. 27 Advancement of Fourier transform infrared spectroscopy with attenuated total reflectance sampling (ATR) enables both qualitative and quantitative analysis of different edible oils.…”

A robust clustering approach for NMR spectra of natural product extracts

“…To qualify solutions obtained from MDS, it was originally proposed that STRESS values below 0.05 were excellent, values between 0.05 and 0.10 were satisfactory and values between 0.1 and 0.15 were marginally acceptable. 60 In another study, 38 the STRESS values <0.05 represented an excellent representation with no prospect of misinterpretation of the model, whereas MDS analysis with stress values >0.3 would be treated with caution, as the points were close to being placed arbitrarily in two-dimensional ordination space. 61 In this study, only 2D solutions were analyzed, although solutions in higher dimensional space always lower the STRESS value, but one loses the visual advantage of a two-dimensional representation.…”