Combination of fluorescence excitation emission matrices in polar and non-polar solvents to obtain three- and four- way arrays for classification of Tempranillo grapes according to maturation stage and hydric status.
Department of Analytical Chemistry, Faculty of Sciences, University of Extremadura, Avda. de Elvas S/N, 06006 Badajoz, Spain; Research Institute on Water, Climate Change and Sustainability (IACYS), University of Extremadura, 06006 Badajoz, Spain. Electronic address: [Email]
The applicability of front-face excitation-emission fluorescence spectroscopy to compare grape water extracts of two consecutive sampling dates, corresponding with two maturation stages, and subjected to full irrigation and non-irrigation, was carried out. The decomposition of the obtained three way grape samples was initially analyzed by means of parallel factor analysis (PARAFAC). A tentative identification of fluorophores was done by matching PARAFAC score values with HPLC measurements. It was found that the first PARAFAC component was highly correlated with the sum of concentrations of catechin and epicatechin. The decomposition of the three way fluorescence data by linear discriminant analysis (LDA)-PARAFAC and LDA-unfolding partial least squares (U-PLS) allowed to discriminate between the first and the second maturation stage. The incorporation of an additional mode to the data, achieved by a diethyl ether extraction, giving rise to a four-way excitation-emission-solvent-samples data set, allowed to differentiate between irrigated and non-irrigated samples with the same assayed algorithms. As far as we know, the use of four-way data arrays for classification issues has been reported for the first time.
