A procedure, Controlled Sudden Decompression (Detente Instantanee Controlee DIC(R)) has been developed to impart a porous structure to partially dried pieces of food by expanding them. In this paper, the DIC cycle was optimized for use with special food products. The establishment of an initial vacuum phase prior to the steam treatment, a treatment by step-wise increases in temperature and an atmospheric air injection phase enabled us to process product pieces in a thick layer, very heat-sensitive products or other food products with a low hardening temperature. The physical attributes evaluated were the expansion ratio and color of three vegetables: potatoes, carrots and onions. (C) 2004 Elsevier Ltd. All rights reserved.