Effect of extrusion conditions on cassava/soybean extrudates

Abstract

Extrusion has been an effective technique in food process industry for production of convenience foods of diverse attributes due to its high productivity rate, very high energy efficiency, no effluents generation, e.t.c. In the present work, the effects of extrusion parameters such as feed moisture (FM), amount of soybean (AS) and barrel temperature (BT) on water absorption index (WAI), water solubility index (WSI), trypsin inhibitors reduction (TIR) and SEC of cassava and soybean blends were investigated using a locally developed simple single screw extruder. A Box-Benkhen design of response surface methodology was used with the three input variables: FM (16%, 20% and 24%), AS (10, 20 and 30 g soybean/ 100g flour) and BT (120, 145 and 170 °C). The experimental values of response variables WAI, WSI, TIR and SEC measured ranged from 2.43 to 3.56 g gel/g dry sample, 0.330 to 0.447 g solid/100g sample, 62.71 to 96.21 % and 2.57 to 4.24, respectively. Regression equations describing the effect of each variable on the product responses were obtained. The product responses were most affected linearly (p<0.01) by changes in BT and to a lesser extent by FM and AS (p<0.1). A second-order polynomials obtained to predict the response variables were all significant (p<0.01) with high correlation coefficients (R2) between 0.895 and 0.937 showing that the model can be used to navigate the design space. In the present study, best extrudate was obtained when the FM, AS and BT were 16 g water/100g, 20 g soyabean/100g flour and 170 °C, respectively.