Browsing by Author "Esteves, M. P."
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- Physicochemical characterization of psyllium fiberPublication . Temudo, M. Salomé; Nunes, M. Cristina; Batista, Ana Paula; Carvalheiro, Florbela; Esteves, M. P.; Raymundo, AnabelaPsyllium is the common name used for several members of the plant genus Plantago, whose seeds are commercially used for mucilage production. Owing to its considerable fiber amount it has been used as dietary fiber supplement. Psyllium has a strong gelling ability, even at low temperature, enabling its use as a gelling agent in the food industry. This work is part of a project to developing jellies enriched with fiber, honey and propolis, aiming to increase these products intake, with evident health benefits. The chemical characterization of psyllium was performed, with the following results (in dry matter): total ash 2.5%, fat content 3.4% and total protein 1.4%. After qualitative acid hydrolysis polymeric sugars were quantified (in dry matter): glucan 7.3%, xylan 61.1% and arabinan 22.9%. This means that total fiber content is about 90%, being soluble fiber predominant, and allows classifying psyllium hemicellulose as an arabinoxylan. Psyllium functional properties were evaluated by water-binding capacity and swelling determination: 27.1 g/g and 36.9 ml/g, respectively. These properties are important in the food industry, but under certain circumstances may limit the food type that can be enriched with this fiber. An important part of the research consisted on the characterization of gels viscoelastic behavior and texture, which were prepared with different psyllium particle dimension (raw and ground) and concentration (2.0%, 2.5% and 3.0%). The Response Surface Methodology was used to study the effect of process conditions (time and temperature) on texture and color characteristics of gels. Texture properties of gels were evaluated by Texture Profile Analysis. Gels dynamic behaviour was studied by a sequence of oscillatory measurements of temperature, time and frequency sweeps. Psyllium gelling properties were improved with the reduction of the fiber particle dimension. Gels revealed potential viscoelastic properties that might be interesting in the industrial purpose of honey jelly production.
- Prebiotic xylo-oligosaccharides as high-value co-products on an integrated biorefinery approach from lignocellulosic feedstockPublication . Moura, Patrícia; Carvalheiro, Florbela; Esteves, M. P.; Gírio, FranciscoThe present work proposes the production of prebiotic xylo-oligosaccharides (XOS) as high-value co-products of the Lignocellulose Feedstock Biorefinery concept, foreseeing potential applications on food, feed and nutraceutical industries. Autohydrolysis was used to selectively solubilise the hemicellulosic fraction of several xylan-rich, widely available, agricultural, agro-industrial and forestry by-products: corn cobs, brewery’s spent grain and Eucalyptus wood chips. The soluble hemicellulose-rich and the solid cellulose- and lignin-rich fractions were separated, and the crude XOS-rich hydrolysates were further purified by gel filtration chromatography. Selected fractions of purified XOS within the desired ranges of polymerization degree were characterised and their prebiotic potential was investigated in in vitro fermentations by bifidobacteria, lactobacilli and intestinal inocula. Parameters such as bacterial growth and XOS consumption were evaluated and compared with commercially available xylo-oligosaccharides. The differences observed were considered of relevance for the formulation of symbiotic preparations and the future design of targeted, tailor-made prebiotic xylo-oligosaccharides.
- Os subprodutos agro-industriais de natureza lenhocelulósica:caracterização da situação portuguesa.Publication . Duarte, Luís C.; Esteves, M. P.; Carvalheiro, Florbela; Vicente, Paula; Gírio, FranciscoOs materiais provenientes do processamento de matérias-primas nas agro-indústrias são usualmente considerados como não perigosos, abundantes, facilmente biodegradáveis, baratos e potencialmente valorizáveis. No entanto, devido às grandes quantidades processadas, podem constituir um problema ambiental, impondo assim um encargo económico significativo neste sector. A viabilidade económica da sua transformação/valorização depende de vários factores, como a quantidade disponível, os custos do material e transporte, as utilizações já existentes e eventuais restrições político-económicas regionais. Para o desenvolvimento de programas de valorização que potenciem a cadeia de valor do sector agro- -industrial, é necessário deter uma caracterização qualitativa e quantitativa destes materiais. Com este propósito, foi desenvolvido um inquérito postal junto das empresas agro-industriais portuguesas que processam materiais de natureza lenhocelulósica. A amostra apresenta uma boa cobertura geográfica e uma adequada representação dos diferentes subsectores agro-industriais, tendo a taxa de resposta obtida sido de 17%. O inquérito permitiu a caracterização, ao nível dos subsectores, em termos da sua composição e distribuição regional, bem como identificar os diferentes materiais produzidos, respectivas quantidades, destinos e valores económicos actuais, o que permitiu definir os principais subsectores/ materiais que mais poderão beneficiar com o investimento em actividades de I&D. Os principais subprodutos identificados foram os seguintes: dreche cervejeira, bagaço de uva sem álcool, polpa de alfarroba, casca de arroz, repiso de tomate, bagaço de azeitona extractado, casca de frutos rijos, engaço, borra de vinho sem álcool e grainha de uva. Por fim, apresentam-se e discutem-se as principais oportunidades e restrições para a valorização destes subprodutos utilizando tecnologias biológicas.