Osmotic dehydration of plant tissues promotes sample volume reduction in line with cell deformation while linked through bonding zones, thus leading to a shrunk cell network. The sample volume changes of apple slices throughout osmotic processes at 30 o C, 40 o C and 50 o C were analysed by using sucrose solution of different concentration (25-65 o Brix), in treatments carried out at atmospheric pressure and by applying a vacuum pulse. These volume changes are compared with the volume variations of sample liquid (water plus soluble solids) and gas phases in order to analyse their different contribution to sample volume development and the porous structure role.