Percorrer por autor "Carvalho, Maria João"
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- Chemical constituents of Euphorbia hyberna L. (Euphorbiaceae)Publication . Ferreira, Ana Margarida V. D.; Carvalho, Maria João; Sequeira, Miguel M.; Silva, Artur M. S.; Carvalho, Luís H. M.Chemical investigation of the aerial part and the roots of Euphorbia hyberna L. subs. hyberna. resulted in the isolation and identification of four triterpenoids (3�-O-octadecanoyllupeol (1), glut-5-en-3�-ol (2), 24-methylenecicloartan-3�-ol (3) and cicloart-23-ene-3�,25-diol (6)) along with the phenolic compounds ellagic acid (4) and 3,30 -di-O-methylellagic acid (7). Although these are all known compounds, this is the first report of their isolation from this plant. Their structures were elucidated on the basis of spectral methods, including 2D NMR experiences, and confirmed by comparing with the literature data.
- Evaluation of wine colour under accelerated and oak-cask ageing using CIELab and chemometric approachesPublication . Carvalho, Maria João; Pereira, Vanda; Pereira, Ana C.; Pinto, João L.; Marques, José C.The present study aims to analyse the evolution of colour and browning of fortified wines submitted to oak and accelerated ageing induced by temperature, both traditional ageing processes of Madeira wines. These wines were follow ed during the first 2 years of ageing and were simultaneously compared to aged reference samples, in order to disclose if accelerated ageing favours the wine evolution. The data anal ysis approaches followed two strategies: the first one was based on the monitoring of wine colour parameters based on CIELab methodology, while the second strategy adopted an untargeted approach, taking advantage of all wine information comprised on the UV-vis spectrum. CIELab results indicated that the greatest variation (up to 92 %) occurs during the vinification, since it was observed that wines produced from the same grape variety (Tinta Negra) acquired different char acteristics already on the vinification processes. All wines tend to approach the reference samples during ageing, with the lowest ΔE* value obtained for Malvasia submitted to canteiro at 2 years of ageing (3.29 units). Sweet Tinta Negra wines, previously submitted to estufagem, presented the most pronounced colour change associated with ageing. The multi variate principal component analysis (PCA) model was built with aged reference samples to evaluate how young wines acquire the reference wine’s characteristics and revealed that accelerated ageing increases colour evolution and favours the homogeneity of Malvasia wines.
- Multiparameter optical monitoring of Madeira winePublication . Pereira, Vanda; Marques, José Carlos; Carvalho, Maria João; Chen, Monchu; Sol, Ricardo; Novo, Catarina; Bilro, Lúcia; Antunes, Paulo; Alberto, Nélia; Pinto, João LemosMadeira wine vinification process has been most ly empiric and requiring further studies. The present paper describes the existing pilot plant facility in Madeira Univer sity, with the installed controlled systems and safety devices. An advanced multi-parameter platform for real time moni toring and interactive data visualization is described and its potential use demonstrated.