Publicação
Propriedades reológicas e de estabilização de emulsões do FucoPol
| Resumo: | In this work, were studied the rheological properties in aqueous solution, namely the thickening ability and the ability of stabilizing oil in water emulsions, of an extracellular polysaccharide produced by the bacterial strain Enterobacter A47 from glycerol. Several studies were carried out, that enabled to evaluate the rheological behavior of the biopolymer under a wide range of pH and ionic strength vallues, as well asto obtain optimum conditions for the formation of stable sunflower oil/water emulsions. It was observed that the biopolymer aqueous solutions have a non-Newtonian shear thinning behavior. By studying the thickening ability, it has been demonstrated that increasing the concentration of polymer in solution, the apparent viscosity increases. Through an experimental central composite rotatable design, it was studied the effect of ionic strength (between 0.15 and 0.75) and pH (between 3.47 and 10.54) on the apparent viscosity. The value of viscosity at the first Newtonian plateau reached higher values in the pH range between 3 and 8, and ionic strength between 0.1 and 0.5 M. The ability of the biopolymer to stabilize sunflower oil/water emulsions was studied using aqueous biopolymer solutions with concentrations of 0.25%, 0.5%, 1.0% and 1.5% w/w, and ratios oil/water (O/A) of 20/80, 40/60, 60/40 and 80/20. It was observed that the polymer solutions of 1.0% and 1.5% w/w, and for oil/water ratios of 20/80, 40/60 and 60/40, were the ones producing stable emulsions without perceiving any phase separation. |
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| Autores principais: | Bastos, Elsa de Fátima Soares da Silva |
| Assunto: | extracellular polysaccharide glycerol Enterobacter A47 rheology emulsions |
| Ano: | 2013 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | português |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | In this work, were studied the rheological properties in aqueous solution, namely the thickening ability and the ability of stabilizing oil in water emulsions, of an extracellular polysaccharide produced by the bacterial strain Enterobacter A47 from glycerol. Several studies were carried out, that enabled to evaluate the rheological behavior of the biopolymer under a wide range of pH and ionic strength vallues, as well asto obtain optimum conditions for the formation of stable sunflower oil/water emulsions. It was observed that the biopolymer aqueous solutions have a non-Newtonian shear thinning behavior. By studying the thickening ability, it has been demonstrated that increasing the concentration of polymer in solution, the apparent viscosity increases. Through an experimental central composite rotatable design, it was studied the effect of ionic strength (between 0.15 and 0.75) and pH (between 3.47 and 10.54) on the apparent viscosity. The value of viscosity at the first Newtonian plateau reached higher values in the pH range between 3 and 8, and ionic strength between 0.1 and 0.5 M. The ability of the biopolymer to stabilize sunflower oil/water emulsions was studied using aqueous biopolymer solutions with concentrations of 0.25%, 0.5%, 1.0% and 1.5% w/w, and ratios oil/water (O/A) of 20/80, 40/60, 60/40 and 80/20. It was observed that the polymer solutions of 1.0% and 1.5% w/w, and for oil/water ratios of 20/80, 40/60 and 60/40, were the ones producing stable emulsions without perceiving any phase separation. |
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