Varietal tracing of virgin olive oils based on plastid DNA variation profiling.

Marga Pérez-Jiménez,Gabriel Dorado,Guillaume Besnard,Pilar Hernandez,Turgay Unver

doi:10.1371/journal.pone.0070507

Abstract

Olive oil traceability remains a challenge nowadays. DNA analysis is the preferred approach to an effective varietal identification, without any environmental influence. Specifically, olive organelle genomics is the most promising approach for setting up a suitable set of markers as they would not interfere with the pollinator variety DNA traces. Unfortunately, plastid DNA (cpDNA) variation of the cultivated olive has been reported to be low. This feature could be a limitation for the use of cpDNA polymorphisms in forensic analyses or oil traceability, but rare cpDNA haplotypes may be useful as they can help to efficiently discriminate some varieties. Recently, the sequencing of olive plastid genomes has allowed the generation of novel markers. In this study, the performance of cpDNA markers on olive oil matrices, and their applicability on commercial Protected Designation of Origin (PDO) oils were assessed. By using a combination of nine plastid loci (including multi-state microsatellites and short indels), it is possible to fingerprint six haplotypes (in 17 Spanish olive varieties), which can discriminate high-value commercialized cultivars with PDO. In particular, a rare haplotype was detected in genotypes used to produce a regional high-value commercial oil. We conclude that plastid haplotypes can help oil traceability in commercial PDO oils and set up an experimental methodology suitable for organelle polymorphism detection in the complex olive oil matrices.

Highlights

The virgin olive oil is obtained by mechanical pressing the fruits of the olive trees (Olea europaea L.), and has not undergone any chemical refinement, which is strictly forbidden by law
Loci 10 and 11, along with microsatellites 27, 51, 38 and 46 have shown a good performance, with an -scored pattern, allowing discriminating five out of the six haplotypes on DNA isolated from olive oils, in agreement with the results previously described for olive trees [30]
We have found that different unwanted compounds as polyphenols and polysaccharides may co-precipitate in the process of olive oil extraction, depending on the olive tree variety

Summary

Introduction

The virgin olive oil is obtained by mechanical pressing the fruits of the olive trees (Olea europaea L.), and has not undergone any chemical refinement, which is strictly forbidden by law. The olive oil consumption is growing outside the traditional olive tree grove areas (Mediterranean Basin), including America, Asia and Australasia (non-traditional-producer countries such as the United States, Mexico, Brazil, Argentina, Peru, Australia and China; FAO 2012, ,http://faostat.fao.org.). Such expansion is mainly due to the recognition of the dietetic properties of olive oil, as source of healthy fatty acids and micronutrients (antioxidants like phenolic compounds, vitamin E, carotenes, etc)

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Conclusion