The potential of SNP‐based PCR‐RFLP capillary electrophoresis analysis to authenticate and detect admixtures of Mediterranean olive oils

Abstract

Authentication and traceability of extra virgin olive oil is a challenging research task due to the complexity of fraudulent practices. In this context, the monovarietal olive oils of Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI) require new tests and cutting edge analytical technologies to detect mislabeling and misleading origin. Toward this direction, DNA-based technologies could serve as a complementary to the analytical techniques assay. Single nucleotide polymorphisms are ideal molecular markers since they require short PCR analytical targets which are a prerequisite for forensic applications in olive oil sector. In the present study, a small number of polymorphic SNPs were used with an SNP-based PCR-RFLP capillary electrophoresis platform to discriminate six out of 13 monovarietal olive oils of Mediterranean origin from three different countries, Greece, Tunisia, and Lebanon. Moreover, the high sensitivity of capillary electrophoresis in combination with the DNA extraction protocol lowered the limit of detection to 10% in an admixture of Tsounati in a Koroneiki olive oil matrix.

Application of an electronic tongue for Tunisian olive oils’ classification according to olive cultivar or physicochemical parameters

“…In this work, the feasibility of applying a potentiometric electronic tongue with cross-sensitivity lipid membranes to discriminate Tunisian olive oils according physical-chemical parameters and sensory attributes used to classify olive oils according to their quality (i.e., extra virgin (EVOO), virgin (VOO) and lampante (LOO) olive oils) [2,3]. However, due to their commercial high value, EVOO are quite prone to frauds, namely by deliberate addition of less expensive olive oils [4]. Thus, in the last years a huge effort has been carried out to characterize olive oils namely those produced in Tunisia from autochthonous olive cultivars (e.g., Chemchali, Chemlali, Chétoui, Oueslati, Sahli, Zarrazi, Zarzis, etc.)…”

“…[1,[5][6][7][8], aiming to set authentication biomarkers that could help minimize the risk of frauds. Some works reported the capability of discriminating EVOO according to the geographical origin (i.e., different regions in the same country or different countries), using different analytical techniques and chemometric tools [4,9,10]. In addition, Hassine et al [11] carried out a chemical and sensorial characterization and preference mapping of autochthonous (Chetoui, Oueslati, Chemlali and Zalmati) and introduced (Arbequina) olive oil cultivars in Tunisia showing that based on those profiles it was possible to differentiate the VOO according to olive variety and geographical origin.…”

Recent developments in olive (Olea europaea L.) genetics and genomics: applications in taxonomy, varietal identification, traceability and breeding

“…While SSRs are usually the most frequently used DNA markers in these studies, the use of SNPs has been suggested based on the following criteria: (1) as the DNA recovered from processed food is usually highly degraded, SNPs provide the advantage of enabling genotyping with shorter DNA fragments (Uncu et al 2015); (2) SNPs are abundant in both coding and non-coding regions of a genome, allowing an easy discrimination of related genotypes. Bazakos et al (2012Bazakos et al ( , 2016, using SNPs markers residing in restriction sites, associated with PCR-RFLP capillary electrophoresis, could discriminate both olive cultivars and the corresponding monovarietal oil from Greece and from different Mediterranean countries (Tunisia and Lebanon), eventually evidencing admixtures at the limit of 10%. Kalogianni et al (2015) reported on the first multiplex SNP genotyping assay for olive oil cultivar identification.…”

“…Up to now, specific molecular and genomic studies on this topic in olive are scarce. Bazakos et al (2016) investigated the molecular responses of olive leaves and roots to salinity using next generation sequencing technology. In this study, many differentially expressed genes related to salt tolerance were found, and in leaf transcripts corresponding to glutathione reductase, superoxide dismutase and proline dehydrogenase were identified.…”

Capillary Electrophoresis Based on Nucleic Acid Detection as Used in Food Analysis

“…A single nucleotide polymorphism (SNP)‐based PCR‐RFLP‐CE assay was also developed to identify the varietal origin of olive oils; 5 SNPs were sufficient to discriminate 9 of the 10 tested varieties (Bazakos and others ). Moreover, the detection limit for an admixture of Tsounati to a Koroneiki olive oil matrix was reduced to 10% (Bazakos and others ). Hernández‐Chávez and others () developed PCR‐CGE‐LIF to detect chicken/turkey meat in heat‐treated pork meat mixtures.…”