Traceability of foods by near- and mid-infrared spectroscopy

Introduction: The problem of verifying labelling compliance of value-added food products is of particular concerns for European control authorities and consumers. From the quality control standpoint, the main problem of authenticating the “Designated Origin” of a foodstuff is that the labelling relies on paper auditing procedures only and not on analytical data. Therefore, the possibility of setting up analytical procedures able to trace the origin of foodstuff is of capital importance. In this study, near- and mid- infrared spectroscopies coupled to chemometrics are used to build an analytical protocol to authenticate the origin of two high value-added food products: extra virgin olive oil and pistachios. Materials and Methods: Two food matrices were considered in this study, extra virgin olive oils and pistachios. As far as the olive oil case is concerned, attention was focused on the possibility of authenticating PDO oils from Sabina (Italy) so a set of about 30 samples was collected from local producers. At the same time, a set of about 50 samples from other geographical origins were collected. All samples were analyzed by NIR (in transmission mode) and MIR (by ATR) spectroscopies and the results were analyzed by chemometric discriminant (PLS-DA) and class-modeling (SIMCA) techniques. On the other hands, pistachio seeds from different origins (Sicily, Middle East) were analyzed by NIR spectroscopy (reflectance) only. Effect on the results of the way samples are presented (whole seed or ground) was also investigated. Spectral data were then analyzed by chemometrics to build classification models by SIMCA and PLS-DA. Results and Discussion: In the case of olive oils, both NIR and MIR data allowed an accurate traceability of Sabina oils with respect to oils from a different origin. SIMCA models resulted in high sensitivity and specificity and PLS-DA provided a high classification rate (>93%) as evaluated on an external validation set. Promising results were obtained also in the case of pistachios for which the built models allowed in many cases to correctly trace the origin of the food. Additionally, the analysis of whole seeds seems to give results comparable to those obtained on ground samples. Conclusion: NIR (and MIR) spectroscopy coupled to chemometrics appears to be a valuable technique to authenticate and trace the origin of foodstuff, providing a fast (and, in the case of NIR, in most cases non invasive) outcome.