Flash vacuum-expansion, a new process for the treatment of plant materials, enables the production of food products (juices, purées, etc.) whose physicochemical and rheological attributes differ from those of products obtained by traditional methods (i.e. blanching, crushing and pulping). Briefly, entire fruits are first steam-heated to 60-90°C and immediately placed in a vacuum chamber (2-5 kPa) where they expand and disaggregate because of the formation of micro-channels inside the tissues by evaporation of water and volatile compounds. Endogenous oxidases are denatured during the steam-heating stage and as the expansion process is performed under vacuum the oxidation and subsequent browning of the products are avoided. Processed materials exhibit higher viscosity than those of traditional products and also differ in colour. This process is increasingly used for pre-treatment of grapes before fermentation in winemaking and for the production of more viscous, better-coloured tomato pureé. Three tropical fruits (passion fruit, guava and mango) were processed by flash vacuum-expansion and further refined. Reference (A) and vacuum-expanded (B) products were then characterized for cell-wall polysaccharides and viscosity and the results were compared. Finally, the process was applied for the extraction of essential oils from citrus peel.