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sur le développement des zones arides et semi-arides

Titre : Secado por aspersión de mucílago de nopal (Opuntia ficus indica) y su efecto en las propiedades reológicas de los polvos reconstituidos

Auteur : León Martínez, Frank Manuel

Etablissement de soutenance : Instituto Politécnico Nacional (IPN)

Grade : Maestria en Ciencias 2010

Résumé
Currently , there is a marked interest by the use of the specie Opuntia ficus indica , due to its ability to develop in adverse environments. Fruits, stems and extracts are used to multiple uses. In particular case, the mucilage generated by this species has been studied by its physicochemical properties and rheological properties . However , the shelf life of the extract is very limited, given its high water activity (>0.8) and chemical composition (polysaccharides). The bio-polymer stabilization has not been studied thoroughly, and is of vital importance an analysis of processing alternatives if it industrial level is wished. In this study was evaluated the use of the spray drying in aqueous extracts of O. ficus indica mucilage without the addition of a drying agent at pilot scale. These studies may help in the determination of factors that affecting the drying process, as well in the process optimization in function of material response, without the needs to invert much economic resources . A 2 3 factorial design with three central points w as used for analyze the effects of the spray-drying conditions on the dehydrated mucilage properties. The effects of inlet air temperature, feed flow rate, and atomizer speed on the rheological properties (elastic and viscous), as well the particle size distribution of mucilage reconstituted solutions at different concentrations were evaluated. In addition, the effects of the drying conditions on powder properties bulk density, moisture content, and yield were considered. It was elected a sample of mucilage powder to determine glass transition temperature (T g ), water adsorption behavior, and particle morphology. The results indicated that mucilage powders obtained had low higroscopicity for a w < 0.6 and with values of T g higher than the room temperature. In general, the mucilage reconstituted solutions exhibited a non-Newtonian “shear thinning” behavior, with important viscoelastic properties at high concentrations, composed of particles in agglomerated structure. The best spray drying conditions founded for the production of mucilage powder with low moisture content , high bulk density , and acceptable rheological properties were with inlet temperature of 130 °C, a feed flow rate of 2.3 L/h, and speed atomizer of 2 1000 rpm .

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