Effect of postharvest methyl jasmonate treatment on fatty acid composition and phenolic acid content in olive fruits during storage

[Background]: The nutritional effects of both table olives and olive oil are attributed not only to their fatty acids but also to antioxidant phenolics such as phenolic acids. Delays in oil processing usually result in undesirable oxidation and hydrolysis processes leading to formation of free fatty acids. These alterations create the need to process oil immediately after olive harvest. However, phenolic content decreases drastically during olive storage resulting in lower quality oil. In the present study we propose postharvest methyl jasmonate treatment as a mean to avoid changes in fatty acid composition and losses of phenolic acids during olive storage. [Results]: Contents of fatty acids and phenolic acids were estimated in methyl jasmonate treated olives throughout 30-day storage, as compared with those of untreated olives. Significant decreases of saturated fatty acids were observed in treated samples whereas increases of oleic, linoleic and linolenic acids were respectively measured (i.e. from 50.8% to 64.5%, from 7.2% to 9.1% and from 1.5% to 9.3%). Also, phenolic acid contents increased significantly in treated olives. Particularly, increases of gallic acid from 1.35 to 6.29 mg kg, chlorogenic acid from 9.18 to 16.21 mg kg, vanillic acid from 9.61 to 16.99 mg kg, caffeic acid from 5.12 to 12.55 mg kg, p-coumaric acid from 0.96 to 5.31 mg kg and ferulic acid from 4.05 to 10.43 mg kg were obtained. [Conclusion]: Methyl jasmonate treatment is proposed as an alternative postharvest technique to traditional methods to guarantee olive oil quality when oil processing is delayed and olive fruits have to necessarily to be stored.
The authors thank the Comunidad Autónoma of Madrid (Spain) and European funding from FEDER program (research project S2013/ABI-3028, AVANSECAL-CM) for financial support. Dra. Gema Flores acknowledges CSIC for her JAE-Doc.