Some raw material characteristics were evaluated in three apple varieties cultivated in Southern Sweden, namely Kim, Mutsu and Jonagold. The study was undertaken to collect information in order to identify the effects of initial tissue properties on mass transport phenomena in general, and osmotic processing responses in particular. The texture profile analysis revealed cortex anisotropy of the three apple varieties studied. The porosity and bulk density varied depending on the sampling location within the apple. More specifically, in each variety the bulk density increased by about 10% on going from the skin to the core of the apple, while the porosity decreased by about 50-60% from the skin to the core of the apple. Experiments to evaluate the tissue pore accessibility, performed by immersion in apple juice, showed that for the agitation levels used in osmotic processing the Kim apple variety had the lowest pore accessibility. Following a simple analysis of the pore accessibility experiments it was inferred that, irrespective of the dominating mechanism driving the osmotic medium into the pores of apple tissue, the pore penetration of the osmotic medium alone cannot explain the extent and the speed of solids uptake during osmotic processing. (C) 2003 Elsevier Ltd. All rights reserved.