Caracterização bioquímica de uvas da Região Demarcada do Douro
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2019-09-18
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A Região Demarcada do Douro é caracterizada por um clima tipicamente mediterrâneo, contudo, as alterações climáticas têm cada vez mais uma influência na fisiologia e fenologia da videira, assim como na composição das uvas e na qualidade do vinho, sendo que os fatores que mais afetam esta cultura são: a radiação solar, a temperatura, o vento, a precipitação, a humidade e as características hídricas do solo. Para combater estes fatores negativos que afetam a vitivinicultura, são tomadas algumas medidas de mitigação tais como a aplicação foliar de caulino e silicato de potássio. Este trabalho teve como objetivo o estudo do perfil antociânico e da composição fenólica das diferentes partes dos bagos de duas castas tintas, Touriga Nacional e Touriga Franca, sujeitas ao tratamento com caulino e silicato de potássio. Este estudo foi realizado com amostras colhidas na Quinta do Orgal, situada em Vila Nova de Foz Côa. Os bagos são provenientes de uma vinha ao alto, situada numa encosta virada a norte em solo maioritariamente xistoso. Os compostos fenólicos totais, taninos totais e antocianinas totais foram quantificados por métodos espectrofotométricos. Por HPLC foram identificadas e quantificadas as antocianinas monoméricas. Os bagos da casta Touriga Franca sujeitos a tratamento com caulino são os que apresentaram uma maior concentração de compostos fenólicos totais. Enquanto que na casta Touriga Nacional, os que apresentam uma concentração superior de compostos fenólicos totais são os bagos tratados com silicato de potássio a 0,01%. No que diz respeito ao teor de taninos totais, os bagos da casta Touriga Nacional, sujeitos ao tratamento com silicato de potássio a 0,05% apresentaram a maior concentração. Na casta Touriga Franca, verificou-se que as amostras controlo apresentaram uma maior concentração de taninos totais, no entanto, entre ambos os tratamentos aplicados, o que apresentou um maior teor destes compostos foram os bagos tratados com caulino. Por fim, os bagos que apresentam um teor superior de antocianinas foram os bagos da casta Touriga Franca sujeitos a tratamento com silicato de potássio a 0,05%. O mesmo se verificou para os bagos da casta Touriga Nacional tratados com silicato de potássio a 0,1%. De um modo geral, a quantidade de antocianinas totais aumentou nos bagos sujeitos ao tratamento foliar. Contudo, o teor compostos fenólicos totais, antocianinas totais e de taninos totais à data da vindima não são significativamente diferente entre os diferentes ensaios quer para a casta Touriga Nacional quer para a casta Touriga Franca. Os resultados obtidos permite-nos afirmar que os tratamentos foliares aplicados à videira com o objetivo de a proteger das secas severas e da elevada exposição solar, não afetam a qualidade dos bagos e consequentemente dos vinhos que daí resultam.
The Douro Demarcated Region is characterized by a typically Mediterranean climate. Climate changes influenced increasingly the physiology and phenology of grapevine, as well as the grape composition and consequently the wine quality. The factors that more affect this crop are: solar radiation, temperature, wind, rainfall, moisture and soil water characteristics. To overcome these negative factors in the viticulture, some mitigation measures are taken, such as the foliar application of kaolin and potassium silicate. The objective of this work was to study the anthocyanin profile and the phenolic composition of the different parts of the berries from two grape varieties, Touriga Nacional and Touriga Franca, subject to treatment with kaolin and potassium silicate. This study was carried out in the Quinta do Orgal, located in Vila Nova de Foz Côa. The berries come from a vineyard, located on a slope facing north in mostly schist soil. Total phenolic compounds, total tannins and total anthocyanins, were quantified by spectrophotometric methods. Monomeric anthocyanins were identified and quantified by HPLC. The Touriga Franca grape variety berries subjected to treatment with kaolin are those that presented a higher concentration of total phenolic compounds. In the Touriga Nacional grape variety, the highest concentration of total phenolic compounds are in the berries treated with 0.01% potassium silicate. Regarding the total tannin content, the berries from Touriga Nacional grape variety, treated with 0.05% potassium silicate, presented the highest concentration. In the Touriga Franca grape variety, it was verified that the control samples presented a higher concentration of total tannins, however, between the two treatments applied, the highest content of these compounds was in the grape berries treatment with kaolin. Finally, the berries that present a higher anthocyanins are those from Touriga Franca grape variety treatment with 0.05% potassium silicate. The same was true for the Touriga Nacional grape variety treated with 0.1% potassium silicate. In general, the amount of total anthocyanins increased in the berries with foliar treatments. However, total phenolic compounds, total anthocyanins and total tannins at harvest are not significantly different between the different treatment for both the Touriga Nacional and Touriga Franca grape varieties. The results obtained allow to state that the leaf treatments applied to the vine to protect it from severe droughts and high sun exposure do not affect the quality of the berries and consequently the resulting wines.
The Douro Demarcated Region is characterized by a typically Mediterranean climate. Climate changes influenced increasingly the physiology and phenology of grapevine, as well as the grape composition and consequently the wine quality. The factors that more affect this crop are: solar radiation, temperature, wind, rainfall, moisture and soil water characteristics. To overcome these negative factors in the viticulture, some mitigation measures are taken, such as the foliar application of kaolin and potassium silicate. The objective of this work was to study the anthocyanin profile and the phenolic composition of the different parts of the berries from two grape varieties, Touriga Nacional and Touriga Franca, subject to treatment with kaolin and potassium silicate. This study was carried out in the Quinta do Orgal, located in Vila Nova de Foz Côa. The berries come from a vineyard, located on a slope facing north in mostly schist soil. Total phenolic compounds, total tannins and total anthocyanins, were quantified by spectrophotometric methods. Monomeric anthocyanins were identified and quantified by HPLC. The Touriga Franca grape variety berries subjected to treatment with kaolin are those that presented a higher concentration of total phenolic compounds. In the Touriga Nacional grape variety, the highest concentration of total phenolic compounds are in the berries treated with 0.01% potassium silicate. Regarding the total tannin content, the berries from Touriga Nacional grape variety, treated with 0.05% potassium silicate, presented the highest concentration. In the Touriga Franca grape variety, it was verified that the control samples presented a higher concentration of total tannins, however, between the two treatments applied, the highest content of these compounds was in the grape berries treatment with kaolin. Finally, the berries that present a higher anthocyanins are those from Touriga Franca grape variety treatment with 0.05% potassium silicate. The same was true for the Touriga Nacional grape variety treated with 0.1% potassium silicate. In general, the amount of total anthocyanins increased in the berries with foliar treatments. However, total phenolic compounds, total anthocyanins and total tannins at harvest are not significantly different between the different treatment for both the Touriga Nacional and Touriga Franca grape varieties. The results obtained allow to state that the leaf treatments applied to the vine to protect it from severe droughts and high sun exposure do not affect the quality of the berries and consequently the resulting wines.
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Dissertação de Mestrado em Bioquímica
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Touriga Nacional , Touriga Franca