Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.5/3328
Título: Oxidação da matéria corante em vinhos tintos. O efeito de diferentes quantidades de oxigénio
Autor: Bento, Marco Paulo Magalhães Azoia
Orientador: Laureano, Olga
Palavras-chave: wine
wine colour
phenolic compounds
matéria corante
composição fenólica
Data de Defesa: 2010
Editora: ISA
Resumo: In recent years the production of red wine has become increasingly sophisticated. Wine is considered one of the most complex beverages and the end product is subjected to several biological and physicochemical processes. Wine consists of a broad spectrum of flavours, aromas and other organoleptic properties. Phenolic compounds are important contributors to the chemical reactions that take place in wine and the resulting complexity (Fulcrand et al., 2006; Ribereau-Gayon et al., 2000). The colour of a red wine is mainly due to the extraction of monomeric anthocyanins from grape skins during fermentation. These pigments are influenced by malolactic fermentation and can participate in polymerisation reactions to form polymeric pigments, which are more stable to sulphur dioxide bleaching and changes in pH than monomeric anthocyanins. The formation of these complexes can be enhanced by the presence of oxygen. However, it is still unclear how much oxygen a wine is capable to consume, but it is suggested that it is more beneficial if applied after alcoholic fermentation (Singleton, 1999). This work aims to determine the influence of oxygen on wine phenolic composition and determine its impact on the evolution of the colour during the maturation of the wine when in contact with different concentrations of oxygen. For this purpose an experimental device was fitted with two different wines. Was carried out two test with a control and two different concentrations of oxygen, a concentrations of 3 mg / L O2 (C-3), in order to simulate a racking down and 6 mg / L O2 (C -6), simulating a racking over applied at once in a discontinuous mode and another on a continuous mode in order to simulate a micro-oxygenation. For all the general parameters studied (pH, SO2, volatile acidity, total acidity, fixed acidity, alcohol level, reduncing sugars and density) the wines do not appear that there are important variations, although levels of SO2 in wine should be checked regularly because the addition of oxygen can lead to a decrease of SO2, which may increase the potential for microbiological contamination, an increase of volatile acidity, which can lead to undesirable flavors in the wine. In relation to phenolic compounds is observed a small decrease in all treatments during the test. Colour intensity was influenced differently by the addition of oxygen for the different experiments performed. In all cases oxygenation led to an increase in colour intensity, compared to control and there is a greater increase in the intensity of colour in wine that led higher concentrations of oxygen especially in micro-oxygenation treatment.Total anthocyanins showed in both studies a decrease and this decreased is a little higher in the treatments that have suffered major applications of oxygen, while the colored anthocyanins increased in wines with higher concentrations of oxygen compared to control. The evolution of total pigments has shown a decrease during the study period, being this decrease higher in the wines where it applied oxygen, while the development of polymeric pigments and the rate of polymerization denote an increase during the test, whit higher results in wines with higher concentrations of oxygen. In both trials there is a common tendency to decrease the levels of proanthocyanidins during the test, but the treatments with higher concentrations of oxygen have a greater tendency for a decreasing of the total levels of proanthocyanidin. Regarding to the degree of polymerization (mDP) results are a bit inconclusive, since treatments with application of oxygen diverge in both studies. The wines were tasted after ten weeks of treatment and the overall appreciation of wines by sensory analysis, we can observe that the panel of judges did not register differences between the control and the treatments with application of oxygen, with one remarkable exception of decreased herbaceous flavor in the modalities with higher concentrations of oxygen in the wine Trincadeira + Touriga Nacional. However, this study shows the oxygen can be applied successfully to promote favorable changes in red wine. The addition of oxygen used during the wine aging can lead to distinguishable differences between control and oxygenated wines. Obviously, more research on oxygenation in wine as well as the effect of oxygen on the composition of red wine in general, should be performed.
Descrição: Mestrado em Viticultura e Enologia - Instituto Superior de Agronomia
URI: http://hdl.handle.net/10400.5/3328
Aparece nas colecções:BISA - Dissertações de Mestrado / Master Thesis

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