Effect of Extrusion Process on Performance of an Indigenous Extruder and Quality of Cassava Products

Abstract

A locally developed autogenous single screw extruder was used to investigate the process for screw extrusion of the flour and starch of cassava, in a bid to find alternate uses for the commodity. The experiment was conducted with a factorial design and completely randomized. Analysis of Variance and Tukey Honestly Significant Difference methods were utilized as follow up test to check the result of extrusion variables: feed moisture (25, 30, 40%) and extruder temperature built up by varying the duration of sampling (2, 10, 18, 24, 30 minutes) on some product quality attributes and system parameters. The product quality attributes considered include water absorption index (WAI) and water solubility index (WSI), product moisture (PQ_MC), transverse expansion (ExR), cold and hot paste viscosities (CPV and HPV), Melt viscosity (MV) and strength properties of extrudates (CP) while the system parameters are product temperature (PT), mean residence time (MRT), and specific energy input (SME). All system parameters PT, MRT and SME varied directly with duration of operation. Also, PQ_MC, CP, WAI, WSI, MV, CPV and HPV varied reciprocally whereas ExR, and MV varied directly with duration of operation. The extrudates’ water loss is directly proportional with ExR. It was observed that extruded cassava starch was less stable than cassava flour extrudates. Moreover, the specific end uses to which the extruded products can be put were identified. All the treatments and their interactions are highly significant (P ≤ 0.001).