Proposal for a New Model for Evaluation of Wine Oxidation

This PhD thesis investigates the wine oxidation phenomenon through the study of selected parameters directly or indirectly related to its occurrence. Firstly, a simulation of real wine shipping was performed. It was found that the wine phenolic composition and antioxidant activity did not change, when considering a white wine packed with different packages commercially available. Their volatile composition did not differ as well, when comparing it to the wines analyzed before the shipping process. In another study, organic and biodynamic Sangiovese wines –from two different vintages and fermented with two conditions, then bottled with three synthetic closures with different permeability – were monitored through a medium-term storage. The aim was to verify the hypothesis that closures with different permeability could significantly affect the composition of wines. It was possible to apply a model for oxygen consumption within the wines and to verify that, in general, the antioxidant activity of wines increased with time, along with polymeric fraction. The same medium-term storage was applied to a Sangiovese biodynamic wine in which had its pH changed. For data elucidation, mathematical modelling was applied to the data of SO2 and the results indicated that, in general, there was no difference in the chemical and sensorial parameters of the wines studied. Moreover, a study conducted with oenological tannins were performed, to better elucidate their complex chemistry, as to elaborate screening methods for the industry proceeding the better evaluation of them. With the use of chemometrics, a fast screening method for the classification of oenological tannins was developed. Finally, the study of anthocyanins and the co-pigmentation process was approached regarding how this phenomenon occurs and the factors in which are involved in it as how the resulting wine color is changed.