Grape quality assessment by chemical markers, prototyping a quality index from multivariable analysis

Mestrado em Engenharia de Viticultura e Enologia - Instituto Superior de AgronomiaGrape-Wine quality is a very complex concept that depends on the interaction of different factors such as the maturity of the grape and the management of the operations in the vineyard and in the cellar. Grape composition is critical to achieving a quality wine. A hundred and sexteen grape samples from Cabernet Sauvignon vineyards were collected in Chile. Chemical grape composition through traditional analyses such as °Brix, pH and nitrogen, GC-MSMS aroma anlyses and spectrophotometric and HPLC polyphenolic compounds analyses were measured. A sensorial evaluation of wines produced in standard conditions from the grapes in analysis was carried out by a panel-taste of experts selected by Concha y Toro company. The data were compared and correlation analyses of Pearson and Spearman and regression analyses were carried out using statistical instruments such as Excel, Rstudio and Statgraphics. Several chemical parameters (assimilable nitrogen, tannins, anthocyanins, isobutil-methoxypirazines) were relevant for the overall quality assessment and the influence of external factors (valley of provenance, trellis system, vines age) and productivity on the concentration of these parameters was significant. The chemical composition of the grape (focused on the significant parameters) was revealed as an objective tool able to predict the correct harvest time and the quality of the grapesN/