Vinificação com a casta Aragonez na presença de produtos alternativos de madeira. Efeitos na composição química e análise sensorial do vinho

Mestrado em Viticultura e Enologia - Instituto Superior de AgronomiaThe main species of oak wood that are oenological recognized as quality, showing a great chemical composition to be in contact with wine, are French (Quercus petraea) and American (Quercus alba). Aging wine in oak barrels brings wine changes of colour, structure and especially in aroma, because during this time different reactions occur among phenolic compounds. However, these processes take a long time, delaying the moment of wines to be insert on the market. So, winemakers have been looking for alternatives that could accelerate this process, obtaining more economic wines with oak characteristics „„similar‟‟ to wines aged in barrels for several months. Therefore, winemakers have the possibility to choose alternative products (chips, staves, cubes, powder, etc.) of good quality and cheaper than oak barrels. The aim of this study was to evaluate how oak alternatives can influence the chemical composition and the sensory analysis of Aragonez wines, when introduced during alcoholic fermentation. The study involved two wines, wine M where the alcoholic fermentation occurred with the French and American oak alternatives together, and wine T (control) that fermented without the addition of alternative. The different parameters studied in each wine were analyzed in four different samples (bleeding (S) at the end of alcoholic fermentation (AF) at the end of malolactic fermentation (MLF) and the month of May (MAY), 2011). It is not always performed for the four samples, all the analysis to physico-chemical parameters considered. The parameters analyzed showed that the wine with oak alternatives (wine M) proved to be slightly different from the control wine (wine T). From the standpoint of color, the intensity of both wines did not show significant differences. The tonality for the two wines showed an increase over time with predominance of yellow tones in relation to red tones. Over time, the profile of the monomeric anthocyanin pigments changed by the interaction of these polymers ((-)- epicatechin and (+)-catechin) with colorless phenolic compounds, which may explain the decrease observed for anthocyanins. The concentration of non-flavonoid phenols decreases for both wines, and wine M presented a higher concentration of anthocyanins and proanthocyanidins, as expected. The power tanning showed lower value for the wine M. This, related to the higher concentration of polymeric pigments in this wine, confirms a sense of “softer tannins” in the presence of oak alternatives.In the wine that had contact with oak wood it was found that there is slightly higher values of low molecular weight procyanidins. This can be explained by contact with oak or by depolymerization of more polymerized proanthocyanidins. The results obtained for the concentration of proanthocyanidins were very similar for the two wines under study and for the two main procedures, separation and determination of proanthocyanidins according to their degree of polymerization and the caracterisation of proanthocyanidins by acid-catalysed depolymerisation in the presence of toluene-α-thiol followed by reversed-phase HLPC analysis. In terms of sensory analysis, the panel of tasters did not make a clear choice for a specific wine, however the quality as a sub parameter of taste, stood out with some differences, and the wine with oak alternative was rated better than control wine