Caracterização bioquímica do aroma de uvas sujeitas a medidas de mitigação do efeito das alterações climáticas na Região Demarcada do Douro
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2019-03-21
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A produção de vinho na Região Demarcada do Douro é afetada, positivamente e negativamente, por fatores extrínsecos a esta. Um dos fatores que condicionam a produção são as condições de mitigação presentes na região. Assim, e com recurso a aplicações foliares, os produtores tentam contornar esta problemática. Assim, o objetivo principal desta dissertação centrou-se na avaliação do efeito das aplicações foliares de silicato de potássio e de silicato de alumínio na composição aromática e metálica do mosto dos bagos das uvas das castas Touriga Nacional e Touriga Franca de um ensaio realizado na Quinta do Orgal no Douro Superior. Para alcançar os objetivos propostos foram analisados os precursores de aroma e os compostos voláteis da fração ligada do mosto das uvas das castas Touriga Nacional e Touriga Franca usando a técnica de microextração em fase sólida acoplado à cromatografia em fase gasosa. Foram também analisados diferentes catiões no mosto dos bagos das duas castas com papel importante no vinho, nomeadamente o cálcio, o magnésio e o potássio. Foi ainda analisada a concentração de alumínio no extrato das películas e no vinho. Relativamente à análise da concentração dos precursores de aroma podemos concluir que o mosto da casta Touriga Franca apresenta valores superiores aos do mosto da casta Touriga Nacional, apesar das condições de mitigação verificadas nesta região. Na análise da composição volátil da fração ligada no mosto apenas identificamos ésteres etílicos, sendo eles, o hexanoato de etilo, o octanoato de etilo, o nonanoato de etilo e o dodecanoato de etilo.
Wine growing in the Douro Demarcated Region is affected, positively and negatively, by factors extrinsic to it. One of the factors that puts constraints on the production is the mitigating conditions present in the region. Thus, by resorting to foliar applications, the growers attempt to get around this problem. The main objective of this dissertation, then, is focused on the evaluation of the effect of the foliar applications of potassium silicate and aluminium silicate on the aromatic and metallic composition of the must of the berries of grapes of the Touriga Nacional and Touriga Franca varieties in a trial conducted at Quinta do Orgal in the Upper Douro. To achieve the proposed objectives, an analysis was made of the aroma precursors and the volatile compounds of the bound fraction of the grape must of the Touriga Nacional and Touriga Franca varieties, using the technique of microextraction in solid phase coupled with chromatography in the gaseous phase. Analyses were also made of different cations in the must of berries of the two varieties with an important role in the wine, specifically, calcium, magnesium, and potassium. The concentration of aluminium in the extract of the skins and in the wine was also analysed. In relation to the analysis of the concentration of the aroma precursors, we can conclude that the must of the Touriga Franca variety presents values higher than those of the Touriga Nacional variety. In the analysis of the volatile composition of the bound fraction of the must, we only identified ethyl esters, which were ethyl hexanoate, ethyl octanoate, ethyl nonanoate, and ethyl dodecanoate.
Wine growing in the Douro Demarcated Region is affected, positively and negatively, by factors extrinsic to it. One of the factors that puts constraints on the production is the mitigating conditions present in the region. Thus, by resorting to foliar applications, the growers attempt to get around this problem. The main objective of this dissertation, then, is focused on the evaluation of the effect of the foliar applications of potassium silicate and aluminium silicate on the aromatic and metallic composition of the must of the berries of grapes of the Touriga Nacional and Touriga Franca varieties in a trial conducted at Quinta do Orgal in the Upper Douro. To achieve the proposed objectives, an analysis was made of the aroma precursors and the volatile compounds of the bound fraction of the grape must of the Touriga Nacional and Touriga Franca varieties, using the technique of microextraction in solid phase coupled with chromatography in the gaseous phase. Analyses were also made of different cations in the must of berries of the two varieties with an important role in the wine, specifically, calcium, magnesium, and potassium. The concentration of aluminium in the extract of the skins and in the wine was also analysed. In relation to the analysis of the concentration of the aroma precursors, we can conclude that the must of the Touriga Franca variety presents values higher than those of the Touriga Nacional variety. In the analysis of the volatile composition of the bound fraction of the must, we only identified ethyl esters, which were ethyl hexanoate, ethyl octanoate, ethyl nonanoate, and ethyl dodecanoate.
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Dissertação de Mestrado em Bioquímica
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Uvas , compostos aromáticos , metais , mitigação , Touriga Nacional , Touriga Franca