Abstract
The knowledge of the isotopic composition of virgin olive oil (VOO) allows the evaluation of authenticity and geographical origin, being an important tool against fraud. This study aimed to assess if VOOs produced in three Mediterranean regions could be discriminated on the basis of multivariate statistical analysis of geoclimatic and isotopic data. A total of 138 geo-referenced VOO samples from Portugal, France and Turkey from two different cultivation years were collected. The isotopic composition (δ13C, δ2H and δ18O) of VOOs was obtained using an elemental analyzer coupled to an isotope ratio mass spectrometer (EA-IRMS). One-way analysis of variance for δ13C, δ2H and δ18O showed some significant differences either between crop years or geoclimatic conditions. Based on multiple regression analyses using meteorological and geographical parameters, a meteoric water line for olive oil from Portugal, France and Turkey, in two harvest years, were created to assess the impact of climate change on their δ2H and δ18O values. Principal component analysis and Linear Discriminant Analysis, used to sort samples according to geoclimatic origin, performed best for French and Portuguese olive oils. In light of the results, multivariate isotopic analysis of VOO samples may discriminate not only between geoclimatic regions but also among cultivation years.
Highlights
Traceability of olive oils is still a popular research topic, addressed in many different ways, including exploring the benefits of different analytical tools due to the increased demand for an effective analytical methodology that can verify the geographic origin of olive oils
The stable isotope ratio analysis (SIRA) is based on the fact that the stable isotope content of bio-elements reflects the geo-climatic characteristics of the area of production [13] and was initially performed in bulk analysis
Value ranging between −30.6 and −27.8 milli Urey (mUr), and −30.6 and −27.7 mUr for 2016 and 2017, respectively. These isotopic values are in accordance with those reported by Gumus et al [9] for olive oils from western Turkey
Summary
Traceability of olive oils is still a popular research topic, addressed in many different ways, including exploring the benefits of different analytical tools due to the increased demand for an effective analytical methodology that can verify the geographic origin of olive oils. Olive oil stable isotope ratio analysis (SIRA), either in bulk, using Isotope Ratio Mass. The SIRA is based on the fact that the stable isotope content of bio-elements reflects the geo-climatic characteristics of the area of production [13] and was initially performed in bulk analysis. In the case of olive oil, bulk δ13 C, δ18 O and δ2 H determinations allowed the differentiation among different geographic origins, at least in some cases. With innovations in this analytical technique that allow the study of stale isotopes in specific compounds, like fatty acids, or volatile compounds, more detailed information can be retrieved allowing improvement in geographical discrimination
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