Effect of some extrusion parameters on the nutrient composition and quality of a snack developed from cocoyam (Xanthosoma sagittifolium) flour

There is increase in the use of cocoyam tubers for flour production which can be use for food and industrial purposes in Nigeria. Cocoyam (Xanthosoma sagittifolium) flour was cooked and extruded in a single screw extruder. A second order central composite response surface design was used in designing the experiment which generated 20 runs on selected process parameters including feed moisture (22, 24 and 26%), screw speed (60, 70 and 80rpm) and barrel temperature (200, 220 and 240°C) on the functional and physical properties (density, expansion, water absorption index (WAI), water solubility index (WSI) and hardness) of the extrudates. Furthermore, the nutritional compositions of the snacks were also determined. Increase in feed moisture content results in higher density, lower expansion, higher WAI, lower WSI and higher hardness in the extrudates while increase in barrel temperature decreases the density, WAI and hardness but led to increase in expansion and WSI in the extrudates. The nutrient value for the extruded snacks were protein (3.76%), fibre (6.41%), carbohydrate (79.50%), energy (343.03 kj/100 g), Ca (238.50 mg/100 g), Mg (113.71 mg/100 g), K (283.77 mg/100 g), Na (97.66 mg/100 g), P(161.23 mg/100 g), vitamin C (1.03 mg/100 g) and niacin (0.78 mg/100 g). This study has established that a nutritious and acceptable snack can be produced from cocoyam flour using extrusion cooking.