Chemometric Discrimination of the Geographical Origin of Three Greek Cultivars of Olive Oils by Stable Isotope Ratio Analysis.

Maria Tarapoulouzi,Theodoros Varzakas,Panagiotis Katsaris,Vasiliki Skiada,Sofia Agriopoulou,Charis R Theocharis,Catherine Rébufa,Sevastianos Roussos,David Psomiadis

doi:10.3390/foods10020336

Abstract

Α stable isotope ratio mass spectrometer was used for stable isotope ratio (i.e., δ13C, δ18O, and δ2H) measurements, achieving geographical discrimination using orthogonal projections to latent structures discriminant analysis. A total of 100 Greek monovarietal olive oil samples from three different olive cultivars (cv. Koroneiki, cv. Lianolia Kerkyras, and cv. Maurolia), derived from Central Greece and Peloponnese, were collected during the 2019–2020 harvest year aiming to investigate the effect of botanical and geographical origin on their discrimination through isotopic data. The selection of these samples was made from traditionally olive-growing areas in which no significant research has been done so far. Samples were discriminated mainly by olive cultivar and, partially, by geographical origin, which is congruent with other authors. Based on this model, correct recognition of 93.75% in the training samples and correct prediction of 100% in the test set were achieved. The overall correct classification of the model was 91%. The predictability based on the externally validated method of discrimination was good (Q2 (cum) = 0.681) and illustrated that δ18O and δ2H were the most important isotope markers for the discrimination of olive oil samples. The authenticity of olive oil based on the examined olive varieties can be determined using this technique.

Highlights

Olive oil plays an important role in the diet in Greece as well as in other Mediterranean countries
A series of criteria and standards associated with the genetic variety, the geographical origin, and the quality grade have been established by the European Union (EU) so as to offer both fair trade in the olive sector as well as safety and protection guarantees for consumers [7,8]
The isotope ratio mass spectrometry (IRMS) technique is a well-established method for determining the authenticity of olive oil [14,25,26,27,28,29]

Summary

Introduction

Olive oil plays an important role in the diet in Greece as well as in other Mediterranean countries. Deliberate mislabeling of lower commercial-grade olive oils or even mislabeling by a false declaration of origin may occur [6]. The IRMS technique is a well-established method for determining the authenticity of olive oil [14,25,26,27,28,29]. Chemometrics and discriminant analysis are important tools for food authenticity. The first goal of this research study was the achievement of a preliminary discrimination of the above-mentioned Greek monocultivar olive oils according to olive cultivar by applying a multivariate analysis to the IRMS measurements. The second goal was to produce a robust model capable of identifying any adulteration of unknown olive oils in Greece regarding cultivar and geographical origin. The first group (training set) was used for the adjustment of the model parameters and the second group (test set) was used for the estimation of generalization error [50]

Sampling

IRMS Analysis

Statistical Analysis

Stable Isotope Analysis of Olive Oils

Chemometric Discrimination of Olive Oils

Conclusions