Influence of surfactant-gelatin interaction on microcapsule characteristics

Abstract

Investigations of influence of surfactant-gelatin interaction on microcapsule characteristics were undertaken. In the first step of microencapsulation 20% (v/v) paraffin oil emulsions were prepared in the solution of SDS of different concentrations with 3.0 % of gelatin. Concentration of SDS was varied in order to provide both types of gelatin-SDS interactions (ionic and hydrophobic ones). Microencapsulation was performed by addition of the crosslinking agent, formaldehyde, to the emulsion. The emulsions were spray dried afterwards and the microcapsules were obtained in a powder form. Microcapsule characteristics such as redispersibility, mean size, wall thickness, wall density, kinetic of core release and wall permeability have been determined. The results show that at prevailing hydrophobic mechanism of interaction, microcapsules have smaller wall thickness, wall density and greater permeability. Rate of paraffin oil release was measured by continuous flow method, and release kinetics was correlated with Hixon-Crowell equation. Release constant calculated by the equation depends on the interaction mechanism. An increase in the value of the constant was obtained if the hydrophobic mechanism of interaction is the prevailing one. This fact shows that conformational changes on gelatin molecules cause formation of permeable microcapsule wall and therefore faster release of core material.