SAFES methodology has been specifically designed to describe and analyze foods, operations and processes systematically. It is based on the multicomponent and polyphasic character of foods, requires establishing simplificative hypothesis and it allows us to quantify the changes that the operations and processes cause in food as well as the mechanisms responsible for them, making possible a quality control in the final product. The application of SAFES methodology to dehydration of apple by combined methods requires considering it as a biologic system constituted by cells which assemble in a tissue including intercellular connexions, intercellular spaces and pores. In this system, the phases and components considered should not limit the mechanisms involved in removing water. Five components distributed in five different phases have been considered in the definition of composition matrix of raw material and products after each operation. Experimental data for mass (total, water and solutes) and volume changes after each step and simplified hypothesis concerning water distribution among phases and location of liquid phase have been necessary to apply the SAFES methodology, determining the evolution of composition and volume in each phase (composition matrix and volume vector) and analyzing driving forces and mechanisms involved in the main changes of the product. The application of SAFES methodology to dehydration of apple by combined methods reveals that traditional methods based on the analysis of foods as a continuous and homogeneous system are inadequate to control the changes in the quality properties of the product. Consequently, it is necessary a rigorous analysis directed to establish relations between food properties and physico-chemical changes in the product along the process. (C) 2007 Elsevier Ltd. All rights reserved.