The effect of extrusion conditions on the functional properties of defatted cake of sunflower-maize based expanded snacks

The effect of extrusion conditions, including feed moisture content (14-20%), screw speed (300-500 rpm), and barrel temperature (120-180°C) on the functional properties (water absorption index (WAI), and water solubility index (WSI), fat absorption capacity (FAC) and foaming capacity) and sensory properties (color, appearance, flavor, overall acceptability and textural characteristics) of an expanded sunflower snack was investigated. Extruded snacks were prepared by substituting maize flour with developed texturized flour of sunflower at 0-40% levels. Protein content increased to 13.83% in snacks prepared with 10% texturized sunflower meal as compared to the control i.e., 7.55%. Fibre content increased while protein digestibility improved with increased level of incorporation of texturized defatted sunflower flour in extruded snacks making. Increasing feed moisture content results in extrudates with lower expansion, lower WAI, higher WSI, higher hardness and lower sensory acceptability. Increasing screw speed caused slight reduction of density and hardness of sunflower extrudate. Feed moisture had positive while screw speed and barrel temperature had negative influence on WAI. Negative coefficient of linear terms of moisture and screw speed indicated that WSI decreased with increase in these variables. Higher moisture content in extrusion process could diminish protein denaturation which lowered WSI values.