Front-face fluorescence spectroscopy in combination with parallel factor analysis for profiling of clonal and vineyard site differences in commercially produced Pinot Noir grape juices and wines

The applicability of using front-face fluorescence spectroscopy to compare profiles of commercially produced New Zealand Pinot Noir grape juice and wine samples from closely related vineyard sites and different grapevine clones was assessed by monitoring eleven batches of grape juices (different sites and clones) during the commercial winemaking process (pre-fermentation, pre-barrelling, barrelled wines). Deconvolution of the recorded fluorescence excitation-emission matrices was carried out using parallel factor analysis (PARAFAC) and the scores plots thereof showed sample groupings on the basis of clone and indicated chemical differences based on vineyard site, winemaking and barrel properties. The four components revealed by the PARAFAC models had their excitation/emission maxima at 278/360 nm, 260/390 nm, 278/315 nm and 320/415 nm, respectively and were tentatively assigned to multiple fluorophore contributions of tryptophan and hydroxyl benzoic acid derivatives (vineyard site discrimination), caffeic acid (clone discrimination), catechin and tyrosol related fluorophores (winemaking based discrimination). The applied methods after further validation have potential to be used as a rapid way to screen grape juices and wines and to provide winemakers with information on the potential quality of their wine.