Análisis no dirigido del aceite esencial de las variedades de mandarino Clemenules y Clemenpons

Abstract

[EN] The fruits belonging to the clementine varieties Clemenules and Clemenpons, are of great commercial interest. They are morphologically indistinguishable, since they have a very similar size, weight, diameter, ratio diameter/height, size of the rind, colour, juice yield and absence of seeds. Their harvesting period is also very similar, although, in the case of the Clemenpons variety, it begins a bit earlier. The present study focuses on the metabolomic analysis of the volatile compounds that make up the essential oil of flavedo from the fruits of both clementine varieties, with the aim of identifying differences between both kinds of oil that may distinguish both types of fruits. The oil extraction of both varieties was done by using the Clevenger distillation system, from samples taken during the whole harvesting period, in two different harvesting periods and in two independent plots. Subsequently, these oils were analysed by using gas chromatography coupled to mass spectrometry. Afterwards, a non-directed analysis of all volatile compounds found in chromatograms and multivariate statistical studies (PCA and PLS-DA) were conducted. That enabled the identification of quantitative differences among the volatile profiles of both varieties, that is to say, both oil kinds showed the same compounds, but in a different concentration. In the end, we tried to identify the volatile compounds responsible for these differences by studying their mass spectra and their chromatographic properties (retention time). Fifteen compounds, all of them belonging to the terpenic type, were found in a higher concentration in the flavedo of fruits belonging to the variety Clemenpons than in fruits belonging to the variety Clemenules. Ten of them were monoterpenes (C10), three of them were hydrocarbons (3-carene, α-terpinene and γ- terpinene), and the other seven were oxygenated. Only three of those seven compounds were clearly identified: trans-carveol and α-terpinyl acetate. The other five compounds were sesquiterpenes (C15), among them, α-humulene and α-sinensal. In the same way, the essential oil of the variety Clemenules had a higher level of aliphatic compounds of a chain superior to 7 carbon atoms, such as 1-octanol alcohol and dodecanal aldehyde. As a conclusion, this study proves that the essential oils of flavedos belonging to the varieties Clemenules and Clemenpons present significative differences that enable the identification of the fruits of both varieties, which cannot be distinguish from a morphological point of view.

[ES] Las variedades de mandarino Clemenules y Clemenpons son muy similares desde el punto de vista fisiológico, morfológico y agronómico, siendo su única diferencia el tiempo de la maduración óptima del fruto. Basándonos en una tradición agrícola que diferenciaba ambas variedades por el aroma de su corteza, abordamos un estudio de los compuestos responsables de dicho aroma en ambas variedades. El estudio metabolómico no dirigido de los componentes del aceite esencial de estas variedades usando la plataforma analítica metabolómica (cromatografía de gases acoplada a espectrometría de masas) ha permitido diferenciar ambas variedades.