Interactions of gelatin—acacia microcapsules with surfactants

Abstract

Gelatin—acacia microcapsules containing water were prepared from those containing olive oil by extracting the oil with acetone and replacing the solvent by ethanol and then by water. Their interactions with octaoxyethyleneglycol-1-dodecyl ether (ODE), sodium 1-dodecyl sulfate (SDS), and 1-dodecylpyridinium chloride (DPyCl) were studied at different pH and ionic strengths of the medium. The nonionic surfactant was found to cause disintegration of the capsules at very high concentrations if pH was low, irrespective of the ionic strength of the medium. On the other hand, ODE did not break down the capsules at high pH. In media of low pH, the capsules were disintegrated by SDS at relatively low concentrations while the solubilized polymers were precipitated by high concentrations of the anionic surfactant. The degree of disintegration decreased as pH of the medium rose. An increase in the ionic strength of the medium brought about an increase in the amount of the precipitated polymers at high surfactant concentrations. Very tow concentrations of DPyCl produced aggregation of the capsules at all pH values studied. As the surfactant concentration increased, the capsules underwent disintegration and then the solubilized polymers were salted out with further increase of the surfactant concentration. Adsorption experiments indicated that the observed disintegration phenomenon of the capsules is due to monolayer and/or bilayer surfactant adsorption on the constituent polymers.