Advisor(s)
Abstract(s)
Resumo
O presente trabalho avalia e compara a composição
química do folhelho branco e tinto, proveniente de castas
típicas da região do Dão. A análise química mostra que o
folhelho é constituído essencialmente por celulose,
hemiceluloses, proteínas e extratáveis em água. Os compostos
solúveis em água são constituídos principalmente por açúcares
monoméricos (glucose e frutose) e por uma mistura complexa
de hemiceluloses. A celulose do folhelho branco e tinto foi
avaliada por difração de raios-X (DRX) e verificou-se que se
trata de celulose I com um grau de cristalinidade de 66,1 e
72,8%, no folhelho tinto e branco, respetivamente. O teor de
celulose no folhelho branco (12,5%) é bastante inferior
quando comparado com o do folhelho tinto (20,8%). Os
métodos espectroscópicos, nomeadamente RMN CP/MAS de 13C, permitiram verificar a presença de material ceroso e
cuticular em ambos os folhelhos. Os extratáveis em
diclorometano dos folhelhos são constituídos maioritariamente
por ácidos gordos e terpenos.
Abstract The present study evaluates and compares the chemical composition of white and red grape skins, from grapes of the typical caste Dão region. Chemical analysis shows that grape skins are constituted essentially by cellulose, hemicelluloses, and water extractable proteins. Water-soluble compounds consist primarily of monomeric sugars (glucose and fructose) and of a complex mixture of hemicelluloses. The structure of cellulose from white and red grape skins was evaluated by X-ray diffraction (DRX) and found to be cellulose I polymorph with a crystallinity degree of 66.1 and 72.8% for red and white grape skin celluloses, respectively. The content of cellulose in white grape skins (12.5%) is significantly lower when compared to that in red grape skins (20.8%). Spectroscopic methods, as 13C CP/MAS NMR, allowed the detection of waxy material in both cuticular tissues of grape skins. Dichloromethane extracts of grape skins consist mostly of fatty and triterpenic acids.
Abstract The present study evaluates and compares the chemical composition of white and red grape skins, from grapes of the typical caste Dão region. Chemical analysis shows that grape skins are constituted essentially by cellulose, hemicelluloses, and water extractable proteins. Water-soluble compounds consist primarily of monomeric sugars (glucose and fructose) and of a complex mixture of hemicelluloses. The structure of cellulose from white and red grape skins was evaluated by X-ray diffraction (DRX) and found to be cellulose I polymorph with a crystallinity degree of 66.1 and 72.8% for red and white grape skin celluloses, respectively. The content of cellulose in white grape skins (12.5%) is significantly lower when compared to that in red grape skins (20.8%). Spectroscopic methods, as 13C CP/MAS NMR, allowed the detection of waxy material in both cuticular tissues of grape skins. Dichloromethane extracts of grape skins consist mostly of fatty and triterpenic acids.
Description
Keywords
Folhelho de uva branca Folhelho de uva tinto Celulose Açúcares neutros Extratáveis em diclorometano Extractives in dichloromethane White grape skins Red grape skins Cellulose Neutral sugars
Citation
Mendes, Joana; Lopes, Sónia; Prozil, Sónia; Evtuguin, Dmitry & Cruz‐Lopes, Luísa (2014). Caracterização Química do Folhelho Branco e do Folhelho Tinto Proveniente de Castas Típicas da Região do Dão. Millenium, 46 (janeiro/junho). Pp. 19‐32.