The effect of extrusion conditions on the functional and physical properties of wheat-based expanded snacks

The effect of extrusion conditions, including feed rate (20–32 kg h−1), feed moisture content (14–22%), screw speed (180–320 rpm), and barrel temperature (100–140 °C) on the functional properties (density, expansion, water absorption index (WAI), and water solubility index (WSI)) and physical properties (density, expansion and textural characteristics) of an expanded wheat snack was investigated. Increasing feed rate results in extrudates with a higher hardness and lower energy to puncture the samples. Increasing feed moisture content results in extrudates with a higher density, lower expansion, lower WAI, higher WSI, higher hardness and lower puncture energy. Increasing screw speed caused slight reduction of density and hardness of wheat extrudate. Higher barrel temperature reduced density, WAI, and hardness, but increased the WSI and puncture energy of extrudate.