Browsing by Author "Coimbra, Manuel A."
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- Apple pomace aqueous extract as a food ingredientPublication . Fernandes, Pedro; Ferreira, Sónia; Elvas, Beatriz; Pinto, António; Gonçalves, Fernando; Coimbra, Manuel A.; Wessel, Dulcineia Ferreira; Cardoso, Susana M.The present work aimed to assess the potential of apple pomace (AP) as a low priced source of food ingredients rich in bioactive compounds. In order to determine its safety, AP was evaluated regarding Total Aerobic Mesophiles (TAM), Yeasts and Moulds (YM) and Enterobacteriaceae (ENT). A hot water extract of AP was investigated concerning total phenolic content (TPC) by the Folin-Ciocalteu method and its antioxidant capacity by the hydroxyl scavenging (OH˙) and ABTS˙+ methods. The extract was incorporated into a yoghurt and its microbiological parameters, antioxidant activity and sensorial acceptability were evaluated. AP had very acceptable microbial levels respecting the TAM, YM and ENT, potentiating its valuation as a source of food ingredients. The AP extract presented a TPC of ≈11 µg of GAE/g, which resulted in the capability to inhibit OH˙ radical and the ABTS˙+ radicals. These properties were reflected by an increased antioxidant activity of the yoghurts fortified with the extract, reaching more than twice of the controls. This was achieved without affecting the native yoghurt lactic acid bacteria and sensorial acceptance. Although the present strategy proves to be very promising for the valuation of AP, further studies are required in order to better elucidate the extracts’ bioactivity.
- Interaction of wine mannoproteins and arabinogalactans with anthocyaninsPublication . Gonçalves, Fernando J.; Coimbra, Manuel A.; Fernandes, Pedro; Wessel, Dulcineia Ferreira; Cardoso, Susana M.; Rocha, Sílvia M.Wine polymeric material (WPM), which includes polysaccharides, proteins, and polyphenolic compounds, interacts with anthocyanins. To determine the contribution of polysaccharides in these interactions, the diffusion performance of anthocyanins along a dialysis membrane was determined in the presence and absence of isolated mannoproteins (MP) and arabinogalactans (AG) from WPM. Furthermore, to estimate the extent of the interaction between WPM and polyphenolic compounds, the activation energy (Ea) required for their diffusion in the presence of WPM was determined. AG, generally more abundant than MP in wine, interact in a greater extent with anthocyanins, showing their relevant contribution for WPM/anthocyanins interactions. The Ea for the diffusion of polyphenolic compounds in presence of WPM indicated the occurrence of interactions with relative weak to strong intensities (2.6–50.8 kJ/mol). As not all polyphenolic compounds were able to be released from WPM, stronger interactions, possibly by covalent linkages, are involved, providing new insights on WPM/polyphenolic compounds relationships.
- Occurrence of cellobiose residue directly linked to galacturonic acid in pectic polysaccharidesPublication . Nunes, Claudia; Guiné, Raquel; Silva, Lisete; Fernandes, Ana Paula; Domingues, M. Rosário; Coimbra, Manuel A.Pectic polysaccharides are present in all plant cell walls. These polymers are constituted by different associated polysaccharides, such as homogalacturonan, xylogalacturonan, rhamnogalacturonan type I, rhamnogalacturonan type II, arabinan, and arabinogalactan [1]. This work describes the structural features of pectic polysaccharides extracted from plum (Prunus domestica L.) and pear (Pyrus communis L.) cell walls and commercial pectin, obtained from Citrus. The alfa-(1→4)-D-galacturonic acid backbone was submitted to a selective hydrolysis with endo-polygalacturonase (EPG) and the fractions with low molecular weight (< 1000 kDa) obtained by size-exclusion chromatography were analysed by mass spectrometry using electrospray ionisation (ESI-MS and ESI-MSn) and by methylation analysis The ESI-MS spectra obtained revealed the presence, in all samples, of several [M+Na]+ ions of pectic oligosaccharides identified as belonging to different series, including oligosaccharides constituted only by galacturonic acid residues (GalAn, n=1-5) and galacturonic acid residues substituted by pentose residues (GalA3Pentn, n=1-2). Surprisingly, it was also observed the occurrence of galacturonic acid residues substituted by hexose residues (GalAnHexm, n=2-5, m=1-2). The fragmentation of the observed [M+Na]+ ions, obtained under ESI-MS/MS and MSn allowed to confirm the proposed structures constituent of these pectic oligosaccharides. Furthermore, the ESI-MSn spectra of the ions that could be identified as GalAnHexm (n=2-5, m=1-2) confirmed the presence of Hex or Hex2 residues linked to a GalA residue. Methylation analysis showed the presence, in all EPG treated samples, of terminally- and 4-linked glucose. These results show that pectic polysaccharides from different origins (plum, pear, and citrus) and structural features (different proportions of branching residues) have Glc residues directly linked to GalA as single residues or as cellobiose residues. The occurrence of GalA substituted by Glc, and Glc-beta-(1→4)-Glc are structural features that, as far as we know, have never been reported to occur in pectic polysaccharides.
- Occurrence of cellobiose residues directly linked to galacturonic acid in pectic polysaccharidesPublication . Nunes, Claudia; Silva, Lisete; Fernandes, Ana P.; Guiné, Raquel; Domingues, M. Rosário; Coimbra, Manuel A.The study carried out in this work concerns the structural characterization of pectic polysaccharides from plum (Prunus domestica L.) and pear (Pyrus communis L.) cell walls and commercial pectin, obtained from Citrus. The -(1→4)-D-galacturonic acid backbone was submitted to a selective hydrolysis with endo-polygalacturonase (EPG) and the fractions with low molecular weight (< 1000 kDa) obtained by size-exclusion chromatography were analysed by mass spectrometry using electrospray ionisation (ESI-MS). The ESI-MS spectra obtained revealed the presence of several [M+Na]+ ions of pectic oligosaccharides identified as belonging to different series, including oligosaccharides constituted only by galacturonic acid residues (GalAn, n=1-5) and galacturonic acid residues substituted by pentose residues (GalA3Pentn, n=1-2). Surprisingly, it was also observed the occurrence of galacturonic acid residues substituted by hexose residues (GalAnHexm, n=2-5, m=1-2). The fragmentation of the observed [M+Na]+ ions, obtained under ESI-MS/MS and MSn allowed to confirm the proposed structures constituent of these pectic oligosaccharides. Furthermore, the ESI-MSn spectra of the ions that could be identified as GalAnHexm (n=2-5, m=1-2) confirmed the presence of Hex or Hex2 residues linked to a GalA residue. Methylation analysis showed the presence, in all EPG treated samples, of terminally-linked arabinose, terminally- and 4-linked xylose, and terminally- and 4-linked glucose. The occurrence of GalA substituted by Glc, and Glc--(1→4)-Glc are structural features that, as far as we know, have never been reported to occur in pectic polysaccharides.