**4. Conclusions**

The results of this work showed that the pistachio oil samples of the variety "Aegina" were within the limits set by the specific standards in terms of high quality. The oil yields of the samples from the two harvest seasons (2017, 2018) were found to be similar, while statistically significant differences were evident for the antioxidant capacity and the R-value between pistachio oil samples, from different years of harvesting. These differences might be attributed to agroclimatic factors, such as different agricultural practices, average temperature, and rainfall from year to year. The FTIR spectroscopy succeeded to classify pistachio oil samples according to the differences which are related to quality parameters, particularly described by the antioxidant capacity, and the R-value. The developed method is fast, accurate, non-destructive, with no excessive sample preparation, and has the additional advantage of not requiring the use of large quantities of solvents, being especially suitable for the screening of large number of samples. Furthermore, the present results provide evidence that the FTIR method could be a promising discriminating tool against fraud related to plant-derived oils, through the use of quality parameters as indicators. *Molecules* **2020**, *25*, x FOR PEER REVIEW 17 of 19 differences were evident for the antioxidant capacity and the R-value between pistachio oil samples, from different years of harvesting. These differences might be attributed to agroclimatic factors, such as different agricultural practices, average temperature, and rainfall from year to year. The FTIR spectroscopy succeeded to classify pistachio oil samples according to the differences which are related to quality parameters, particularly described by the antioxidant capacity, and the R-value. The developed method is fast, accurate, non-destructive, with no excessive sample preparation, and has the additional advantage of not requiring the use of large quantities of solvents, being especially suitable for the screening of large number of samples. Furthermore, the present results provide evidence that the FTIR method could be a promising discriminating tool against fraud related to plant-derived oils, through the use of quality parameters as indicators. **Author Contributions: C**onceptualization, C.S.P., L.V., and M.G.; methodology, C.S.P and M.G.; formal

**Author Contributions:** Conceptualization, C.S.P., L.V., and M.G.; methodology, C.S.P and M.G.; formal analysis, L.V., D.A., and A.M.; investigation, L.V., D.A., and A.M.; data curation, L.V., D.A., and A.M.; writing—original draft preparation, L.V. and M.G.; writing—review and editing, L.V., M.G., and C.S.P. All authors have read and agreed to the published version of the manuscript. analysis, L.V., D.A., and A.M.; investigation, L.V., D.A., and A.M.; data curation, L.V., D.A., and A.M.; writing—original draft preparation, L.V. and M.G.; writing—review and editing, L.V., M.G., and C.S.P. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding.

**Funding:** This research received no external funding. **Acknowledgments:** This research work was supported by the Hellenic Foundation for Research and

**Acknowledgments:** This research work was supported by the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no. 1313). Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no. 1313).

**Conflicts of Interest:** The authors declare no conflict of interest. **Conflicts of Interest:** The authors declare no conflict of interest.

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**Sample Availability:** Samples of the compounds are available from the authors.

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