Characterisation of the aroma components of clonal grapes and wines from Aragonez and Trincadeira Vitis vinifera L. cultivars
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2008
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A grande variabilidade e diversidade dos vinhos tintos produzidos em Portugal provenientes de castas nacionais Vitis vinifera L. justificam a sua caracterização aromática e físico-química. Essa caracterização, tem por objectivos, preservar a qualidade e a tipicidade dos vinhos de diferentes regiões, bem como, contribuir para aprofundar o conhecimento de castas que proliferam no mundo vitivinícola. Além disso, a caracterização do aroma de vinhos clonais apresenta um interesse inegável para a indústria vitivinícola, devido à importância que assume nos diversos aspectos qualitativo, produtivo e financeiro.
De entre algumas centenas de compostos voláteis pertencentes a diversas famílias químicas e existentes em diferentes gamas de concentração, apenas uma parte contribui efectivamente para o aroma, aumentando a sua intensidade e complexidade no vinho. O conhecimento sobre a identidade e a concentração de tais compostos é fundamental para uma melhor compreensão do seu papel no aroma do vinho. Esta abordagem deverá ser complementada com a análise sensorial descritiva, para que se possa obter uma visão mais abrangente do aroma dos vinhos e da apreciação da sua qualidade.
O programa Português de Selecção Clonal, criado em 1978, cujos objectivos são os de conhecer e seleccionar as melhores castas, visando aumentar a qualidade dos vinhos produzidos em Portugal, possui actualmente diversos clones certificados que são cultivados por viticultores. As castas Aragonez e Trincadeira estão entre as oito variedades tintas mais plantadas em Portugal, encontrando-se já certificados 7 e 6 clones, respectivamente.
O conhecimento sobre as relações entre o papel individual de cada composto odorante e o papel global dos compostos responsáveis pelo aroma, são metas específicas a alcançar, de modo a ser possível realizar a escolha dos melhores clones para produzir vinhos de elevada qualidade.
Este estudo teve como objectivo, contribuir para a caracterização dos componentes do aroma de vinhos tintos clonais e dos respectivos mostos e uvas, das castas Aragonez e Trincadeira Vitis vinifera L
O desenvolvimento e a aplicação de um método de cromatografia em fase gasosa – olfactometria (GC-O), designado método de intensidade posterior, permitiu, pela primeira vez, estabelecer os perfis odorantes de cada casta e, simultaneamente, diferenciar os vinhos clonais de ambas as castas e os mostos dos clones de Aragonez. Assim, em todos os vinhos clonais foram detectados diversos compostos odorantes, tendo apresentado intensidades médias mais elevadas: o ácido 3-metilbutanóico, o 2-feniletanol, o Furaneol™ e o 4-vinilguaiacol. A quantificação de alguns compostos odorantes utilizando a cromatografia em fase gasosa acoplada ao detector de ionização de chama (GC-FID) encontrados nos vinhos clonais e respectivos mostos e uvas, demonstrou a existência de diversas diferenças estatísticas entre os clones.
Os compostos Furaneol™ e homofuraneol, caracterizados com os descritores de odor a açúcar queimado (tipo caramelo) e algodão doce, foram identificados nos vinhos clonais de Aragonez e Trincadeira bem como nas fracções livres e ligadas dos mostos de Aragonez, indicando a sua origem varietal.
Demonstrou-se por GC-O, GC-FID e análise sensorial descritiva que o ano de vindima apresentou uma influência relevante nos vinhos clonais da casta Trincadeira. A análise discriminante linear aplicada aos dados obtidos, revelou a existência de algumas variáveis discriminantes que poderão ser utilizadas para se obter uma correcta classificação dos vinhos clonais provenientes das duas vindimas em estudo.
Os atributos de aroma, adocicado, herbáceo, animal, frutos secos, frutos vermelhos, especiarias e madeira, utilizados pelo painel sensorial, foram úteis para a obtenção do perfil de aroma dos vinhos clonais de Aragonez e de Trincadeira.
A não quantificação de compostos monoterpénicos e a escassez de norisoprenóides em C13 nas uvas e nos mostos são indicadores de que as castas Aragonez e Trincadeira podem ser classificadas como castas neutras.
A informação obtida por GC-O e pela análise sensorial descritiva sugere uma elevada utilidade destas “ferramentas sensoriais” para o controlo da qualidade dos vinhos.
The large variability and diversity of red wines produced in Portugal with Portuguese Vitis vinifera L. cultivars fully justify their chemical and aroma characterisation. The objectives of this characterisation are to preserve the quality and tipicity of the wines from different regions and to contribute to the deeper knowledge of grape varieties in the world. Furthermore, the characterisation of the aroma of clonal wines is of undeniable interest to the winemaking industry, due to its productive, financial and qualitative aspects. Among hundreds of volatile compounds of distinct classes and a wide range of concentrations present in red wines, only a part contribute effectively to the aroma, enhancing the intensity and complexity of the wine flavour. Knowing the identity and the concentration of such compounds in wines is crucial for a better understanding of their role in defining wine aroma. This approach should be complemented with descriptive sensory analysis in order to give an overview of the aroma of wines and appreciation of the general quality of wines. The Portuguese Clonal Selection Program was created in 1978 with the objectives of getting to know and select our best varieties of grapes and to increase the quality of wines produced in Portugal. Nowadays it has several certified clones commonly used by grape-growers. Aragonez and Trincadeira are among the eight more planted red grape varieties in Portugal and respectively seven and six clones of both cultivars have already been certified. The knowledge of the relationships between the individual role of each odourant compound and the global role of the overall aroma compounds are specific targets that we need to know in order to be able to choose the best clones to produce the best wines. The aim of this study was to contribute for the characterisation of the aroma of distinct clonal red wines, musts and grapes, from Vitis vinifera L. cultivars Aragonez and Trincadeira. The development and application of a gas chromatography-olfactometry (GC-O) posterior intensity method allowed, for the first time, the establishment of the odourant profiles of each cultivar and, simultaneously, the differentiation of the clonal wines among Aragonez and Trincadeira varieties and clonal musts from Aragonez. Several odourant compounds were detected, having the highest average intensities in all clonal wines: 3-methylbutanoic acid, 2-phenylethanol, Furaneol™, and 4-vinylguaiacol. The quantification by gas chromatography-flame ionization detector (GC-FID) of some of the odourant compounds found in the clonal wines as well as those found in musts and grapes showed several statistical differences among clones Furaneol™ and homofuraneol, described with a burnt sugar (caramel-like) and candy-cotton odour descriptors, were identified in Aragonez and Trincadeira clonal wines as well as in both free and bound fractions of Aragonez musts, indicating their grape-derived origin. Vintage had a significant influence on Trincadeira clonal wines, as was demonstrated by GC-O, GC-FID and by descriptive sensory analysis. Stepwise linear discriminant analysis applied to data obtained from the previous analyses revealed some discriminating variables that can be used to obtain a correct classification of the clonal wines from the two distinct vintages. The aroma attributes sweet, herbaceous, animal, dried fruits, red fruits, spicy and woody, used by the sensory panel, were useful in obtaining the aroma profile of the Aragonez and Trincadeira clonal wines. The inexistence of quantified monoterpenic compounds and the poorness in C13-norisoprenoids found in musts and grapes indicated that Aragonez and Trincadeira can be classified as neutral cultivars. The information obtained by GC-O and descriptive sensory analysis suggested the usefulness of these “sensory tools” for controlling wine quality.
The large variability and diversity of red wines produced in Portugal with Portuguese Vitis vinifera L. cultivars fully justify their chemical and aroma characterisation. The objectives of this characterisation are to preserve the quality and tipicity of the wines from different regions and to contribute to the deeper knowledge of grape varieties in the world. Furthermore, the characterisation of the aroma of clonal wines is of undeniable interest to the winemaking industry, due to its productive, financial and qualitative aspects. Among hundreds of volatile compounds of distinct classes and a wide range of concentrations present in red wines, only a part contribute effectively to the aroma, enhancing the intensity and complexity of the wine flavour. Knowing the identity and the concentration of such compounds in wines is crucial for a better understanding of their role in defining wine aroma. This approach should be complemented with descriptive sensory analysis in order to give an overview of the aroma of wines and appreciation of the general quality of wines. The Portuguese Clonal Selection Program was created in 1978 with the objectives of getting to know and select our best varieties of grapes and to increase the quality of wines produced in Portugal. Nowadays it has several certified clones commonly used by grape-growers. Aragonez and Trincadeira are among the eight more planted red grape varieties in Portugal and respectively seven and six clones of both cultivars have already been certified. The knowledge of the relationships between the individual role of each odourant compound and the global role of the overall aroma compounds are specific targets that we need to know in order to be able to choose the best clones to produce the best wines. The aim of this study was to contribute for the characterisation of the aroma of distinct clonal red wines, musts and grapes, from Vitis vinifera L. cultivars Aragonez and Trincadeira. The development and application of a gas chromatography-olfactometry (GC-O) posterior intensity method allowed, for the first time, the establishment of the odourant profiles of each cultivar and, simultaneously, the differentiation of the clonal wines among Aragonez and Trincadeira varieties and clonal musts from Aragonez. Several odourant compounds were detected, having the highest average intensities in all clonal wines: 3-methylbutanoic acid, 2-phenylethanol, Furaneol™, and 4-vinylguaiacol. The quantification by gas chromatography-flame ionization detector (GC-FID) of some of the odourant compounds found in the clonal wines as well as those found in musts and grapes showed several statistical differences among clones Furaneol™ and homofuraneol, described with a burnt sugar (caramel-like) and candy-cotton odour descriptors, were identified in Aragonez and Trincadeira clonal wines as well as in both free and bound fractions of Aragonez musts, indicating their grape-derived origin. Vintage had a significant influence on Trincadeira clonal wines, as was demonstrated by GC-O, GC-FID and by descriptive sensory analysis. Stepwise linear discriminant analysis applied to data obtained from the previous analyses revealed some discriminating variables that can be used to obtain a correct classification of the clonal wines from the two distinct vintages. The aroma attributes sweet, herbaceous, animal, dried fruits, red fruits, spicy and woody, used by the sensory panel, were useful in obtaining the aroma profile of the Aragonez and Trincadeira clonal wines. The inexistence of quantified monoterpenic compounds and the poorness in C13-norisoprenoids found in musts and grapes indicated that Aragonez and Trincadeira can be classified as neutral cultivars. The information obtained by GC-O and descriptive sensory analysis suggested the usefulness of these “sensory tools” for controlling wine quality.
Descrição
Tese de Doutoramento em Ciências Alimentar
Palavras-chave
Vinhos tintos clonais , Mostos , Compostos odorantes , Controlo de qualidade , Clonal red wines , Musts , Odourant compounds