Geographical discrimination of grapevine leaves using fibre optic fluorescence data and chemometrics. Determination of total polyphenols and chlorophylls along different vegetative stages

Auto fluorescence of grapevine leaves has been employed to discriminate vineyards from two different geographical regions and to quantify the amount of total polyphenols and chlorophylls. For that, fluorescence spectroscopy with an optical fibre was used on samples of grapevine leaves (previously freeze-dried) and excitation-emission matrices were collected. Two spectral regions were analysed independently: one with excitation wavelengths from 279 to 372 nm and emission wavelengths from 384 to 496 nm, and the second with excitation between 390 and 585 nm and the emission between 654 and 756 nm. Firstly, an exploratory analysis was performed with parallel factor analysis (PARAFAC) to extract useful information from the data (scores and loadings). The obtained scores were used to perform a linear discriminant analysis (LDA) model for the classification of samples according to its geographical region. A total of 95% of correct predictions were obtained in the validation samples. Moreover, the PARAFAC scores of the components used in each model were analysed along the vegetative stage and a clear evolution with time has been observed. The quantification of total polyphenols and chlorophylls was also carried out with unfolded partial least squares (U-PLS) and N-way partial least squares (N-PLS). Good correlation coefficients (for the validation set) were obtained for both parameters and similar results were achieved with both algorithms (0.82 (U-PLS) and 0.76 (N-PLS) for total polyphenol and 0.83 (U-PLS) and 0.82 (N-PLS) for total chlorophylls).

Automated summary

This study uses auto fluorescence of grapevine leaves to discriminate vineyards from different geographical regions and quantify total polyphenols and chlorophylls. Fluorescence spectroscopy with PARAFAC analysis is used to extract useful information and perform linear discriminant analysis for classification. Unfolded partial least squares and N-way partial least squares are used for the quantification of total polyphenols and chlorophylls. The results show that these methods can accurately discriminate vineyards from different regions and determine the content of total polyphenols and chlorophylls.