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sur le développement des zones arides et semi-arides

Titre : Efecto del método de extracción en las características químicas y físicas del mucílago del nopal (Opuntia ficus-índica) y estudio de su aplicación como recubrimiento comestible.

Auteur : ABRAJÁN VILLASEÑOR, MYRNA ALICIA

Université de soutenance : Universitat Politècnica de València

Grade : Tesis doctoral 2008

Résumé
The aim of this work was to optimize the method of extracting the Nopal (Opuntia ficus-indica var. Forragera) mucilage and to study its potential use in the formation of edible films. As such, it has been applied to a fresh cut vegetable : jícama. To this end, the mucilage has been extracted by different processes and each extract has been characterized. Differences have been found in the chemical (macro and micro components) and physical (rheological behaviour, colour and solubility) properties of the extracts. The process that includes blanching of the peeled and ground stems was the one that gave the extract with the best properties for its use as film, due to the fact that it showed the greatest thickening capacity (greatest mean molecular weight), the least pH sensitive solubility and had the best colour. The mucilage extracted using the selected process was characterised as to water interactions through the water sorption isotherms and the glass transition temperature-moisture content relationships. Its capacity as a film forming product was studied through the evaluation of the water barrier properties, film solubility and mechanical and optical (gloss, translucency and colour) properties ; all of these in film samples equilibrated at three different moisture contents. Likewise, the influence of incorporating different ratios of lipids (oleic or estearic acids) in the film was evaluated, through the changes induced in the above mentioned properties. Results showed that oleic acid allows us to obtain films with better mechanical and water barrier properties, but it imparts yellowness to the film. The coating capacity of film formulations containing oleic acid were evaluated in jicama cubes. None of the formulations supposed a reduction of the product water loss during its storage at 4ºC and 85% relative humidity, although loss of product firmness was inhibited.

Mots Clés : Opuntia ficus indica | Viscosidad intrinseca | Mucilago | Comportamiento al flujo | Isoterma de sorcion | Temperatura de transicion vitrea | Films y recubrimientos comestibles

Présentation

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