Control of olive cultivar irrigation by front-face fluorescence excitation-emission matrices in combination with PARAFAC
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Due to their antioxidant properties, biophenolic compounds from vegetables and derived products are very demanded by the consumers. The olive fruit pulp is rich in these compounds, and, in this paper, the influence of irrigation on the levels of these compounds has been investigated. Methanolic extracts from olive paste samples submitted to different irrigation treatments were analyzed by front-face fluorescence. Excitation-emission matrices, recorded as a set of emission spectra in the range 290-450 nm, and in the excitation range of 240-290 nm, were analyzed by means of Parallel Factor Analysis (PARAFAC). The loadings and scores corresponding to three components were obtained. In the same samples, polyphenols were also analyzed by chromatography. High correlations were found between the first component PARAFAC scores and epicatechin (R = 0.856) and catechin plus epicatechin concentrations (R = 0.873), second component scores and oleuropein (R = 0.892, only when epicatechin concentration is lower than 0.55 mg/L) and the third component scores and vanillic acid concentrations (R = 0.877). The representation of the two first PARAFAC component scores allowed discriminate between the different irrigation treatments. Polyphenol concentrations obtained by both methods were analyzed statistically by ANOVA and Duncan's multiple test. The obtained results showed significant differences between the irrigation treatments.