Newly Characterized Wild Olive Trees Produce Healthy, Quality Oil

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Spanish researchers have published a study that will delight both chefs and spectroscopists—olive oil produced from recently identified and characterized wild olive trees boasts sensorial, physicochemical and stability characteristics that are within the values set by the International Olive Council.

Like wine and meat, olive oil can easily be manipulated. In fact, according to the National Consumer's League, roughly 50% of extra virgin oil oil is fraudulent. Expensive to produce, fraudsters will mix a small amount of olive oil with other kinds of low-quality oils, such as hazelnut oil. Scientific instrument manufactures have risen to the challenge of identification over the years, debuting equipment and developing advanced spectroscopic methods that can quickly and reliably verify the quality of olive oil.

In addition to fraud, in 2013, the bacteria Xylella Fastidiosa, which infects and kills olive trees, gained a foothold in Italy, before spreading to France, Germany, Ibiza, Portugal, Israel and Spain by 2019. Still rebounding from the effects of the bacteria, researchers made an interesting discovery on the Medes Islands in the Mediterranean Sea—they identified a wild albino ivory-white olive tree.

While the wild olive tree (Olea europaea L. var Sylvestris) is the ancestor of the modern olive tree (Olea europaea L. subsp. europaea), it has barely been used in the food industry. In fact, researchers say this study, published in Antioxidants, represents the first approach to the characterization of wild ivory-white olive trees.

“As white fruits, they have unique features [including] a high content in phenolic elements that could have had an effect within the required parameters by the European Union,” explained study author Rosa Lamuela, a professor of food sciences of the University of Barcelona.

However, that turned out not to be the case. The researchers collected fruits from the trees, sowing their seeds in a greenhouse before planting them in an orchard. Seven out of the 78 seedling trees (12%) produced ivory-white fruits. In fall 2018, the fruit was harvested, pressed into olive oil and subsequently analyzed using an array of techniques, including liquid chromatography tandem mass spectrometry (LC-MS/MS), as well as triple-quadruple mass spectrometry.

Results indicated the following characteristics were within regulatory levels: fatty acid composition, pigment and color, phenolic compounds and oxidative stability. Additionally, the oil passed a “sensorial analysis” by eight trained testers on the Catalan Official Olive Oil Tasting Panel.

According to Lamuela, the phenolic profile of the wild olive tree is what sets it apart from all other olive trees. She attributes this to the very specific geological environment found on the Medes Islands—hydric stress, salinity and wind included.

“The phenolic profile of the oil is higher than the one described in a genotype of wild olives in Algeria. The genotype is one of the main agronomic factors responsible for the chemical and organoleptic footprint of the olive oil strongly contributing in its qualitative and nutritional characteristics,” she said. “This is why we might be in front of genotypes that could be used for food purposes and in programs for the improvement of the traditional olive tree.”

The study is part of a biodiversity program aimed at preventing loss of genetic diversity. The researchers said they will continue to assess the trees’ genetic variability and examine future potential applications.

“Protected areas such as the Medes Islands can help maintain the biodiversity of species and food, such as virgin olive oil. In the future, new studies should be promoted to improve the conservation of wild olive trees, the selection of genotypes with other sensory characteristics better adapted to certain environmental conditions, and the use of genetic material for reproductive purposes,” concluded study co-author Anna Vallverdú-Queralt.

Photo: The organoleptic properties of olive oil from white olive trees are similar to those varieties from cultivated olive trees. Credit: Antonia Ninot/IRTA