Orange pulp was extruded using a Brabender single extruder (20:1 1/D) so as to modify the functional and structural properties of the fibre. The independent variables studied were: barrel temperature (83degreesC, 100degreesC, 125degreesC, 150degreesC, and 167degreesC), moisture content (22, 25, 30, 35, and 38 g/100 g), and screw speed (126, 140, 160, 180, and 194 rpm). The feed speed was kept constant at 70 g/min. The compression ratio was 3:1, and the die diameter was 4 mm. The extrusion process increased the water absorption index (34.86 g/100 g), water solubility index (134 g/100 g), and swollen volume (43.75 g/100 g) and these variables were significantly influenced by the feed moisture content of the raw material and by the barrel temperature. The extruded orange pulp had 74.87 g/100 g total alimentary fibre, 54.81 g/100 g insoluble alimentary fibre and 20.06 g/100 g soluble alimentary fibre. Biscuits of good technological quality and with a good level of acceptance were obtained by means of replacing up to 15 g/100 g of the wheat flour with extruded orange pulp, The energy value of the biscuits decreased with increased extruded orange pulp content, with reductions of 2.95, 6.62, and 10.67 g/100 g in total calories as compared to the control. (C) 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.383213220