In many productions, Arthrospira sp. biomass is dried in cylinders or layers form. Drying involves shrinkage that changes organoleptic qualities and aspects. To understand the change, similar production forms and sizes were convective dried at 45 degrees C with 2-6 mm initial diameter cylinders and 1 and 4 mm thin layers. Total layer size- and cylinder length shrinkage ratio is only 95%. Thicknesses direction shrinkage is the most significant with 28-65%. Cylinders present anisotropicity and shrink more in the perpendicular direction to the support than in the parallel one. All curves present several stages. The first ideal shrinkage stage of layers goes until the half of initial moisture content that involves lower final porosity by layers than by cylinders. End of ideal shrinkage moisture content decreases when cylinder initial diameter decreases. Cylinders initial porosity is around 15-20% and increases only during the 2nd stage up to final porosities between 68% and 80%. (C) 2010 Elsevier Ltd. All rights reserved.