Authentication of PDO/PGI olive oils using NMR and isotopic fingerprinting

ALONSO-SALCES, R. M.; MORENO-ROJAS, J. M.; HOLLAND, M. V.; RENIERO, F.; GUILLOU, C.; HÉBERGER, K.

Praga (República Checa)

Simposio; 3rd International Symposium on Recent Advances in Food Analysis; 2007

Institute of Chemical Technology Prague, IAEA and RIKILT of the University of Wageningen

Food authenticity and food traceability are of great concern to the consumer, food processor, retailer and regulatory bodies. For instance, one authenticity issue of increasing importance is geographical origin, with some selected products permitted to be marketed using a Protected Designation of Origin (PDO), Protected Geographical Indication (PGI) or Traditional Specialty Guaranteed (TSG) label on the basis of their area of production [Regulation (EEC) No 2081/92]. Extra-virgin olive oil is one of these high value protected agricultural products. The European Commission has already registered in the “Register of protected designations of origin and protected geographical indications” 95 PDO and PGI olive oils, produced in Spain, Italy, Greece, Portugal, France and Slovenia. However, given the financial benefits associated with such labels, it is very likely that economic fraud occurs (e.g. labelling a non-PDO product as a PDO one, adulteration with olive oils that do not fulfil the PDO requirements). Therefore, validated methods to guarantee the authenticity and traceability of PDO and PGI olive oils are necessary to protect both the consumer and the producer from illicit practices in this sector.   Within the European Union, the quality control of olive oils is usually performed applying methods described in the EC Regulation 656/95. The problem of authentication of olive oils with respect to their geographical origin has been studied using various analytical approaches such as NMR (1H, 13C, 31P), NIR spectroscopy, IRMS, LC-MS, and GC-MS [1-4]. However, most of these have considered only a limited number of samples and geographical areas. NMR and isotopic fingerprinting methods seem particularly promising in this context. Indeed, isotopic and NMR methods are used in support of EU policies concerning the origin of agricultural products. These methods can be used to provide objective analytical parameters in order to develop a European system for protecting foodstuffs produced according to certain quality standards such as those of a PDO, PGI or TSG against fraud.   Different approaches are being studied in our laboratory for the determination of the geographical origin of extra-virgin olive oils: i) Multivariate analysis of 1H-NMR profiles of olive oils; ii) Multivariate analysis of 1H-NMR profiles and isotopic measurements (1H, 13C and 18O) of olive oils; and iii) Multivariate analysis of 1H-NMR profiles of the unsaponifiable fraction of olive oils. In the two first proposals, i) and ii), olive oils are dissolved in deuterated chloroform for NMR analysis. In the third approach, the unsaponifiable fraction of olive oil is obtained by a standard procedure, and then dissolved in deuterated chloroform prior to NMR analysis. NMR spectra are produced by a high throughput NMR method and the isotopic measurements of 1H, 13C and 18O are performed by IRMS. The data provided by these spectroscopic techniques are analysed by unsupervised and supervised pattern recognition techniques in order to achieve classification models for the authentication of olive oils labelled “as of designated origin”.   To this aim, MAST in collaboration with other partners (TRACE project (http://www.trace.eu.org), and scientific contacts) has collected a statistically significant number of authentic PDO and PGI extra-virgin olive oils from EU and non EU countries (716 samples) during two seasons, 2005 and 2006. In 2005, we collected olive oils from Italy (226 (63 from Liguria), Spain (72), Greece (43), Turkey (14) and France (9); whereas in 2006 samples were from Italy (252 (79 from Liguria), Spain (38), Greece (46), France (10) and Cyprus (6). Moreover, Stazione Sperimentale dei Oli e Grassi (Milan, Italy) provided us with 94 samples of unsaponifiable fractions of extra-virgin olive oils from Italy, Spain, Greece, Tunisia, Turkey and Syria.   The analytical data of such a large number of samples and from such an extensive range of geographical origins has allowed us to study many aspects of olive oils. In this sense, classification models were developed for the authentication of olive oils of a certain PDO, e.g. “Riviera Ligure” (Liguria, Italy) in order to distinguish them from the oils of other protected origins (Objective of the TRACE project supported by the Food and Quality Priority of the EU Framework VI research programme); the geographical characterization of olive oils at the national level; and the geographical characterization of Italian olive oils at the regional level. The contribution of these results will considerably strengthen our ability to protect both the consumer and the producer in the ongoing fight against fraud in the food sector.