New thoughts about red winemaking using the Portuguese emblematic red grape variety Touriga Nacional growing in Lisbon

Mestrado em Engenharia de Viticultura e Enologia (Double degree) / Instituto Superior de Agronomia. Universidade de Lisboa / Faculdade de Ciências. Universidade do Porto

Touriga Nacional is one of the most important grapes variety in Portugal. It is used to create varied type of wine due to the high polyphenols content, the characteristic aroma and the good sugar accumulation. By one hand, consumer ask for sustainable wine, with a low content of alcohol; by the other hand, a slice of consumer ask for deeply coloured and astringent wines. The work lead to better understand chemical phenomena in wines obtained by Vitis Vinifera Sativa “Touriga Nacional”. The work differentiates a “standard protocol” by an “AEB Protocol” and study difference between two vinification methods with the support of laboratory analysis that are focused in the study of phenols compounds, colour and aroma. A study of two different wine obtained by Touriga Nacional grapes was carried out. The work lead to better understand efficiency of some oenological products used as pectic enzymes, yeast and their supplies, exogenous tannins (both hydrolysable and condensed). The wines were subjected to a maceration post fermentation of fifteen days. In order to evaluate differences, in a part of must oenological product named above wasn’t added (Control), while another part was processed with oenological products addition (Treatment). Both wines were subjected to maceration of 15 days. The finished wines were bottled and analysed in laboratory, with a particular focus on chromatic and phenolic characteristics (CIE-Lab analysis, phenolic concentration, pigments and their polymerization). The data obtained suggested that the use of pectolytic enzymes, exogenous tannins, yeast and their supplies can effectively modify important oenological parameters as colour intensity, tonality, anthocyanins concentration (and their polymerization), pigments and phenols. CIELab data suggested that differences can’t be found with naked eyes, by the way several study must be done, especially regarding aging. The results show that the use of specific oenological products, applied in different vinification phases, can effectively modify wines chemical composition, by increasing phenolic composition, colour intensity and polymerized pigments but with a reduction in anthocyanins and tonality. Each analysis was performed in triplicate and a comparison T-test (independent trial), after a variance study was carried out. More study should be done in the next years, especially using independent replicates of vinification and the same vinification procedure

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