Quality and origin assessment of pistachio nuts by using X-ray fluorescence spectroscopy and chemometrics

Food counterfeiting is an emerging problem worldwide and the increasing consumption of fake products has brought food safety into major focus. In recent years, several analytical approaches were developed to prevent food counterfeiting. Among them, X-ray Fluorescence spectroscopy (XRF) is emerging as a fast and simple screening tool for food elemental analysis, with important applications in the agri-food sector. The present work explores the feasibility of using portable XRF device to verify the quality and the geographical origin of pistachio samples coming from different growing areas of Sicily (Italy), including pistachio samples form Bronte and Raffadali districts, recognized by the European Union with the Protected Designation of Origin (PDO) label. The XRF spectra and the yields extracted for the main identified elements were compared with each other by using Principal Component Analysis (PCA). Statistical analysis highlighted that pistachio samples clustered into distinct groups accordingly with their territory of origin, having a different elemental profile. Among the elements, K and Ca appear to act as discriminant markers, followed by Rb and Fe. Potassium mainly characterized the samples originating from Agrigento and Messina, whereas Ca, Rb and Fe the pistachio seeds harvested in Catania. Based on these results, the elemental composition detectable through XRF analysis could be used as a fingerprint to disentangle foodstuffs of different origin and to hinder the occurrence of food counterfeits concerning the branded products, in support of the traceability system. The possibility of assessing quality and traceability quickly, easily and in-situ, gives solid perspectives for a large-scale application of the XRF technique at all stages of the food chain.