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Publications

Publications by Nelson Machado

2017

FTIR chemometrical approach for clonal assessment: Selection of <i>Olea europaea</i> L. optimal phenotypes from cv. Cobrancosa

Authors
Machado, M; Machado, N; Gouvinhas, I; Domínguez Perles, R; Barros, AIRNA;

Publication
JOURNAL OF CHEMOMETRICS

Abstract
Fourier transform infrared spectroscopy has been applied in tandem with multivariate statistical approaches, with the prospect of developing a methodology for the prediction of interesting traits in distinct clones of “Olea europaea L.” For this purpose, the infrared spectra of either the drupes or the corresponding olive oils of 6 distinct clones of the Cobrançosa cultivar, in 2 ripening stages (semi-ripe and ripe), have been registered resorting to an attenuated total reflection accessory. These clones were previously evaluated with respect to antioxidant activity and olive oil yield, while multivariate analyses, namely, partial least squares regression and discriminant analysis have been applied to the spectral data collected to obtain a prediction model for the assessment of these traits in distinct clones through the infrared spectra. This methodology leads to minimal erroneous classification rates in the validation procedure of 3.9% and 6.3% for olives and olive oils, respectively, using the first derivative of the spectra. Thus, the suitability of this methodology for the assessment of different clones has been shown with visible benefits for a time consuming and costly process such as clonal selection. Furthermore, this procedure might be extended for other cultivars or different species once proper calibration models are attained for each matrix. Copyright © 2017 John Wiley & Sons, Ltd.

2017

Critical Review on the Significance of Olive Phytochemicals in Plant Physiology and Human Health

Authors
Gouvinhas, I; Machado, N; Sobreira, C; Dominguez Perles, R; Gomes, S; Rosa, E; Barros, AIRNA;

Publication
MOLECULES

Abstract
Olive oil displays remarkable organoleptic and nutritional features, which turn it into a foodstuff appreciated by consumers, and a basic component of the Mediterranean diet. Indeed, the noticed benefits of including olive oil in the diet have been assigned to the presence of diverse bioactive compounds with different molecular structures. These compounds confer a wide range of biological properties to this food matrix, including the prevention of distinct human diseases as well as the modulation of their severity. The most relevant bioactive compounds present in olive oil correspond to benzoic and cinnamic acids, phenolic alcohols and secoiridoids, and also flavonoids. Over the last decades, several studies, devoted to gaining a further insight into the relative contribution of the separate groups and individual compounds for their biological activities, have been conducted, providing relevant information on structure-activity relationships. Therefore, this paper critically reviews the health benefits evidenced by distinct phenolic compounds found in olive oils, thus contributing to clarify the relationship between their chemical structures and biological functions, further supporting their interest as essential ingredients of wholesome foods.

2017

Addressing Facts and Gaps in the Phenolics Chemistry of Winery By-Products

Authors
Machado, NFL; Dominguez Perles, R;

Publication
MOLECULES

Abstract
Grape and wine phenolics display a noticeable structural diversity, encompassing distinct compounds ranging from simple molecules to oligomers, as well as polymers usually designated as tannins. Since these compounds contribute critically to the organoleptic properties of wines, their analysis and quantification are of primordial importance for winery industry operators. Besides, the occurrence of these compounds has been also extensively described in winery residues, which have been pointed as a valuable source of bioactive phytochemicals presenting potential for the development of new added value products that could fit the current market demands. Therefore, the cumulative knowledge generated during the last decades has allowed the identification of the most promising compounds displaying interesting biological functions, as well as the chemical features responsible for the observed bioactivities. In this regard, the present review explores the scope of the existing knowledge, concerning the compounds found in these winery by-products, as well as the chemical features presumably responsible for the biological functions already identified. Moreover, the present work will hopefully pave the way for further actions to develop new powerful applications to these materials, thus, contributing to more sustainable valorization procedures and the development of newly obtained compounds with enhanced biological properties.

2017

Anomalous surface-enhanced Raman scattering of aromatic aldehydes and carboxylic acids

Authors
Machado, NFL; Marques, MPM; de Carvalho, LAEB; Castro, JL; Otero, JC;

Publication
JOURNAL OF RAMAN SPECTROSCOPY

Abstract
Raman and SERS spectra of benzaldehyde (Bz-CHO) and chromone-3-carboxaldehyde (Ch-CHO) on silver colloids have been analyzed, being subsequently compared to the spectra of the corresponding acids. In the SERS spectra of both aldehydes, the band corresponding to the.(C =O) stretching mode of the carboxaldehyde group at ca. 1700cm (-1) ismissing, while a newband at 13501400cm(-1), characteristic of the symmetric stretching mode of carboxylate group, is appearing in both cases. These results point out that aldehydes are oxidized to their corresponding acidswhen adsorbed on silver nanoparticles. This conclusion has been confirmed by means of HPLC-MS analysis and supported on the basis of DFT calculations. Copyright (c) 2016 John Wiley & Sons, Ltd.

2016

Chemometric analysis on free amino acids and proximate compositional data for selecting cowpea (Vigna unguiculata L.) diversity

Authors
Domínguez-Perles, R; Machado, N; Abraão, AS; Carnide, V; Ferreira, L; Rodrigues, M; Rosa, EA; Barros, AI;

Publication
Journal of Food Composition and Analysis

Abstract

2016

Chemometric analysis on free amino acids and proximate compositional data for selecting cowpea (Vigna unguiculata L.) diversity

Authors
Dominguez Perles, R; Machado, N; Abraao, AS; Carnide, V; Ferreira, L; Rodrigues, M; Rosa, EADS; Barros, AIRNA;

Publication
JOURNAL OF FOOD COMPOSITION AND ANALYSIS

Abstract
Biodiversity of cowpea, along with the interesting agricultural and nutritional properties, has encouraged research with local landraces of Portugal. This work deals with the composition of dry beans of cowpea from 28 different Portuguese cultivars concerning dry matter (DM), crude proteins (CP), fat content (FC), ash, and concentration of free essential and non-essential amino acids. Data obtained on these traits showed contents of DM, FC, ash, and CP in the ranges of 95.7-98.9%, 1.0-1.6%, 2.7-4.7%, and 18.6-26.9%, respectively. The content in free amino acids was evaluated as an indicator of germinating potential of the diverse cultivars assessed. The amino acids content was the highest in the varieties 'Vg50' and 'Vg58'. Cluster and principal component analyses of the data allowed the identification of the most promising Portuguese landraces of cowpea to be used for breeding new varieties with improved germination potential and nutritional traits.

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