Percorrer por autor "Silva, M. C. M."
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- Changes in free monoterpenol content in vinho verde and model wines during ageingPublication . Rogerson, F. S. S.; Silva, M. C. M.
- Defining the uniqueness of monovarietal wines from native portuguese varieties of vitis viniferaPublication . Guedes, P.; Pina, C.; Santos, C.; Santos, S.; Vasconcelos, I.; Silva, M. C. M.; Hogg, T.
- Defining the uniqueness of monovarietal wines from native portuguese varieties of Vitis viniferaPublication . Guedes, P.; Pina, C.; Santos, C.; Vasconcelos, I.; Silva, M. C. M.; Hogg, T.; Cabral, L.; Vieira, M.; Pessanha, M.; Soares Franco, J. M.Studies have been carried out on red and white monovarietal wines vinified during the 1995, 1996 and 1997 harvests. The essential aim being to evaluate sensory quality, correlate it with chemical analytical data and relate these to the various winemaking options available. Hence selective native varieties from the Douro, Dao, Bairrada and Vinhos Verdes regions have been studied and the analytical / sensorial data correlated to such factors as grape maturation and maceration regime. Results are presented illustrating the quality effects of variety / winemaking practice combinations, both in terms of analytical data (sensory and chemical) and taster preferences.
- Enzymatic enhancement of the free monoterpenol content of a Portuguese wine from a single, native grape variety; “Trajadura”Publication . Rogerson, F. S. S.; Grande, H. J.; Silva, M. C. M.Three important monoterpene aroma releasing activities contained in an Aspergillus niger preparation were investigated for effects of pH, alcohol, SO2, temperature and concentration of glucose. Application of the enzyme preparation during microvinification or wine maturation of a Portuguese white wine from Trajadura grapes, increased monoterpene content roughly 2-fold and 3-fold respectively.
- Industry / university collaboration in product focussed oenological research in Portugal - the SOGRAPE / UCP ESB partnership 1995 - 1998Publication . Guedes, P.; Pina, C.; Santos, C.; Santos, S.; Vasconcelos, I.; Silva, M. C. M.; Hogg, T.
- Multiple imputation and maximum likelihood principal component analysis of incomplete multivariate data from a study of the ageing of portPublication . Ho, P.; Silva, M. C. M.; Hogg, T. A.A multivariate data matrix containing a number of missing values was obtained from a study on the changes in colour and phenolic composition during the ageing of port. Two approaches were taken in the analysis of the data. The first involved the use of multiple imputation (MI) followed by principal components analysis (PCA). The second examined the use of maximum likelihood principal component analysis (MLPCA). The use of multiple imputation allows for missing value uncertainty to be incorporated into the analysis of the data. Initial estimates of missing values were firstly calculated using the Expectation Maximization algorithm (EM), followed by Data Augmentation (DA) in order to generate five imputed data matrices. Each complete data matrix was subsequently analysed by PCA, then averaging their principal component (PC) scores and loadings to give an estimation of errors. The first three PCs accounted for 93.3% of the explained variance. Changes to colour and monomeric anthocyanin composition were explained on PC1 (79.63% explained variance), phenolic composition and hue mainly on PC2 (8.61% explained variance) and phenolic composition and the formation of polymeric pigment on PC3 (5.04% explained variance). In MLPCA estimates of measurement uncertainty is incorporated in the decomposition step, with missing values being assigned large measurement uncertainties. PC scores on the first two PCs after multiple imputation and PCA (MI+PCA) were comparable to maximum likelihood scores on the first two PCs extracted by MLPCA.