Solubility of Dispersions of Opuntia ficus-indica

Solubility of the macromolecules depends on their surface properties, and is related to the chemical composition, the molecular flexibility and in minor degree of the form and the size. Frequently in the extraction and purification processes, no-solvents are used, and these can generate conformationals changes reversible or not, affecting hydration and recovery of the original functional properties. The mucilage is an interesting ingredient for the food industry due to their viscous properties. This is extracted from cladodes of Opuntia ficus-indica L. Mill. that grows in the Argentinean semi-arid, particularly in Santiago del Estero. The aim of this work was to study the solubility properties of mucilage precipitated with different solvents and to compare against that of freeze-dried mucilage (FM). For it, the natural exudate of the parenchymatic tissue of sliced cladodes was precipitated with ethanol (EtOH) and acetone (Me2CO). The solubility was determined as the dry weight of the supernatant, collected after centrifuging to 10.000 rpm, 60 min. Effect of the stirring time and temperature (25, 40, 60, 80 degrees C) on the solubility was studied. The results showed that the solubility was dependent of the solvent employed. Highest solubility was found for FM and EtOH. On the basis of these results, we can conclude that although freeze-drying allows obtaining precipitated with very good solubility, precipitation with ethanol appears like the recommendable method, since it showed good solubility and was the most economic and atoxic process.