Alginates being depolymerized during their alkaline extraction, reducing extraction time could help producing higher rheological quality alginates. The purpose of the present work is to study fresh Laminaria digitata destructuration during alkaline extraction and its link to extraction kinetics. Both alginate extraction yield and mean diameter of algae particles were followed for different values of agitation level and initial size of algae pieces. Results highlighted the existence of a link between extraction yield and algal destructuration. Those elements and the specificity of L. digitata structure have been taken into account to propose a kinetics model based on a fluid-particle reaction with decreasing size particles. The model parameters have been adjusted thanks to acquisition data and its predictive capacity was assessed by validation data. Provided predictions appeared to be relevant and the model structure suitability was confirmed, as extraction yield kinetics specific shape was quite reliably described. (C) 2008 Published by Elsevier Ltd.