Editor's Note
This research suggests the importance of isotope analysis to the differentiation of Argan forest products and demonstrates relationships between environmental conditions and the plant organic materials’ isotopic composition. The results indicate that the isotopic composition of plant organic material from different regions may to some degree be predictable. The results could help assure the traceability of Moroccan Argan oil and contribute to the added value of the Protected Geographical Indication label of these products.
March 2020
Forensic Chemistry
DOI: https://doi.org/10.1016/j.forc.2019.100198

Argan oil is obtained from the fruits of the Argan tree ( Arganiaspinosa ), an endemic species from south-western Morocco. Oil is extracted from Argan seeds through a traditional or a semi-automated process. In the case of edible oils, seeds are roasted before extraction, but when the oil is used for cosmetics, no seed roasting is required. Several cooperatives and private enterprises are established in south-west Morocco producing and commercializing edible and Cosmetic Argan oil. The identification of the geographical origin of Argan oils is attracting great interest from consumers and producers since it may be used as a criterion for guaranteeing quality and authenticity. Stable isotope techniques can provide useful information on the origin of food products. For these reasons the natural abundance isotopic ratios of Carbon, Oxygen and Nitrogen were measured using isotope ratio mass spectrometry (IRMS) for samples (cosmetics oil, seed) produced between July and August 2012 in different Moroccan cooperatives with certified PGI (protected geographical indication) label and organic certification, representing five provenances in the southwest part of Morocco. These provenances are distinct on a Geographical, hydrological and climatic level: Essaouira, Agadir Idaou Tanane, chtouka Ait Baha, Taroudant and Tiznit.

IRMS was selected as a reliable technique to characterise the stable carbon and oxygen isotope ‘fingerprints' of Moroccan Protected Geographical Indication (PGI) Argan oils and nitrogen isotope analysis of the Agan nut. Moreover, it demonstrated relationships between environmental parameters and the isotopic composition of plants coming from geographically distinct areas. The results obtained in this study indicate that it is possible to differentiate Argan oil producing areas, which can be associated with regional (cooperatives), and promote and protect the quality and commercial value of this important Moroccan plant product.

Graphical abstract

Distribution of δ 13 C (‰) values in the Argan tree according to principal geographical area (Essaouira, Agadir Ida ou tanane, Chtouka-Ait baha, Taroudant and Tiznit). Diagrams of δ 18 O values origin of the samples argan oil collected in different region (Essaouira (Es), Agadir (Ag), Ait Baha Tafraout (A. Baha), Taroudant (Tar), and Tiznit (Tiz) of the Shoutern Moroccan basin.
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