The release of potassium sorbate front tapioca starch-based edible films with glycerol as plasticizer was studied and modeled. Tapioca importance as a source of starch is growing rapidly, especially because its price in the world market is low when compared to starches from other sources. A semi-empirical approach was proposed to describe the diffusion of water molecules into the polymeric film, the counter diffusion of the antimicrobial compound and the polymeric matrix swelling kinetic. Despite the simplicity of the proposed model, it successfully fitted the experimental data. From the obtained results it was observed that casting technique, producing films with high amorphous degree, determined a greater contribution of matrix relaxation to sorbate release. The pH of the receiving media contributed slightly to antimicrobial release and its effects seem to be related to the influence of this variable on antimicrobial solubility. (c) 2007 Elsevier Ltd. All rights reserved.