The development of phytochemical constituents in Girgentina : a study in relation to local oenology and viticulture

Abstract

The development of the phytochemical constituents of the local indigenous grape variety Girgentina was studied. The aim of this study was to compare the development of these properties with foreign varieties and thus discover its true relative potential, as well as determining an ideal harvest date. Primarily, the titratable acidity, brix, pH, berry weight and total polyphenol content via Folin Ciocalteu test were monitored. The identification of the glucose: fructose ratio via uHPLC was also tested for and it was determined that Girgentina is a high glucose variety and not a high fructose one. Twelve different polyphenols, which are either determinants of colour or play a role in the organoleptic features, were also subjected to uHPLC analysis. Myricetin and Myricetin-3-O-glucoside were absent in Girgentina and the isomers of coumaric acid were found to be at a low concentration with a mean value throughout the study of 2.821mg/kg for the cis- isomer and 5.550mg/kg for the trans- isomer. The volatile terpenoid content was also tested for and it was signficantly high when compared to other varieties since it reached a mean value of 2.504mg/l. The different tests used for this study were performed individually on the skins, seeds and pulp of Girgentina, the idea behind this was to understand the development of the constituents in each part of the grape so that local winemakers could adapt certain oenological techniques that would enable them to produce a second to none bottle of wine from the indigenous variety.