António Manuel Jordão

Professor Adjunto

Instituto Politécnico de Viseu. Escola Superior Agrária. Departamento das Indústrias Agro-Alimentares, Quinta da Alagoa – Estrada de Nelas, 3500-606 VISEU

Sumário. Com o objectivo de aprofundar o conhecimento sobre o potencial da madeira de carvalho pertencente à espécie Quercus pyrenaica Willd. (proveniente da região do Gerês, Portugal), com vista ao fabrico de barricas utilizadas na conservação dos vinhos, procedeu-se à quantificação dos teores em taninos elágicos (vescalagina, castalagina, roburina D, roburina E e grandinina), ácido elágico e em alguns compostos voláteis (furfural, 5-hidroximetilfurfural, cicloteno, furaneol, cis e trans b-metil-g-octalactona, guaiacol, metil-guaiacol, eugenol, isoeugenol, vanilina e siringaldeído) presentes.

Os valores dos compostos estudados para a espécie Quercus pyrenaica Willd., foram comparados com os valores quantificados para os mesmos compostos nas duas espécies de madeira de carvalho mais utilizadas na indústria de tanoaria em Portugal, o Quercus alba L. e o Quercus petraea Liebl., oriundas dos Estados Unidos da América e da França, respectivamente. Os resultados obtidos, permitiram constatar a existência de valores similares em taninos elágicos entre as espécies Quercus pyrenaica Willd. e Quercus petraea Liebl., tendo ambas as espécies apresentado valores mais elevados destes compostos relativamente à espécie Quercus alba L.. No que diz respeito aos teores em compostos voláteis quantificados, as espécies Quercus alba L. e Quercus petraea Liebl. evidenciaram valores significativamente mais elevados destes compostos comparativamente aos valores quantificados na espécie Quercus pyrenaica Willd.

Ellagitannins and Volatile Compounds Content from Quercus pyrenaica Willd. Oak Wood Species Used in Cooperage Industry

Abstract. Thepurpose of this paper is to deepen knowledge of the potential of Quercus pyrenaica Willd. wood (found in the Gerês region, Portugal), with the aim of producing casks to wine ageing. The contents of ellagitannin (vescalagin, castalagin, roburin D, roburin E and grandinin), ellagic acid and some volatile compounds (furfural, hydroxymethyl-5-furfural, furaneol, cis and trans b-methyl-g-octalactones, guaiacol, methyl-guaiacol, eugenol, isoeugenol, vanillin and syringaldehyde) were measured.

The values of the compounds studied for Quercus pyrenaica Willd., were compared to values found for the same compounds in the two oak species most widely used in cooperage, Quercus alba L. and Quercus petraea Liebl., found in the United States of America and France, respectively. Similar amounts of ellagitannins were found between Quercus pyrenaica Willd. and Quercus petraea Liebl.. Both species were found to have higher levels of ellagitannins than Quercus alba L.. As for the contents of volatile compounds, Quercus alba L. and Quercus petraea Liebl. were found to have significantly higher levels of these compounds compared to those found in Quercus pyrenaica Willd.

Key words: Quercus pyrenaica; Quercus alba; Quercus petraea; volatile compounds; ellagitannins

Teneurs en Ellagitanins et Composés Volatils Présentés dans le Bois de Chêne de l'Espèce Quercus pyrenaica Willd. utilisé dans la Tonnellerie

Les valeurs des composés analysés pour l'espèce Quercus pyrenaica Willd. ont été comparées aux valeurs quantifiées pour les mêmes composés dans les deux espèces de bois de chêne plus utilisées dans l'industrie de la tonnellerie, le Quercus alba L. et le Quercus petraea Liebl., en provenance des États-Unis et de la France, respectivement. Les résultats obtenus ont permis de constater l'existence de valeurs semblables de ellagitanins entre les espèces Quercus pyrenaica Willd. et Quercus petraea Liebl., les deux espèces ayant présenté des valeurs plus élevées que l'espèce Quercus alba L.. En ce qui concerne les teneurs de composés volatils, les espèces Quercus alba L. et Quercus petraea Liebl. ont mis en exergue des valeurs bien plus élevées en termes de ces composés en comparaison avec les valeurs quantifiées de l'espèce Quercus pyrenaica Willd.

Mots clés: Quercus pyrenaica; Quercus alba; Quercus petraea; composés volatils; ellagitanins

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Entregue para publicação em Dezembro de 2006

Aceite para publicação em Janeiro de 2007