Effect of some operational extrusion parameters on the constituents of orange pulp

Orange pulp was extruded using a Brabender laboratory single screw extruder (20:1 L/D), with the objective of modifying the properties of the fibre components. Response surface methodology was used following a central rotational composite, experimental design (51). The independent variables studied were: barrel temperatures (83, 100, 125, 150, and 167 degreesC); moisture contents (22%, 25%, 30%, 35% and 38%) and screw speed (126, 140, 160, 180 and 190 rpm). The feed speed was kept constant (70 g/min). The compression ratio was 3:1, and the diameter of the die 4 mm. The extrusion process decreased insoluble dietary fibre in 39.06% and soluble dietary fibre was increased by 80%. Also, total dietary fibre was decreased as consequence of the production of smaller fragments that would not be completely recovered during the alcoholic precipitation. Increments in contents of total pectin and soluble pectin resulted from the solubilization of pectic substances. (C) 2004 Elsevier Ltd. All rights reserved.