Effect of Process Variables on Some System Parameters and Physical Properties of Millet-Soybean Fura Extrudates

A three-factor three level central composite rotatable (CCRD) was adopted to study the effect of feed composition (X1), feed moisture content (X2) and screw speed (X3) on average residence time (ART), mass flow rate (MFR), specific mechanical energy (SME), expansion ratio (ER) and bulk density (BD) during extrusion of pearl millet and soybean flour mixtures for fura production (a Nigerian traditional food).The results shows that linear and quadratic terms showed significant (P < 0.05) effect on the ART. The regression model for the data indicates that the proposed model was adequate showing significant (P < 0.05), possessing lack of fit and with satisfactory coefficients of R2 = 0.83, 0.87, 0.79.0.92 and 0.96 for specific mechanical energy, mass flow rate, average residence time, expansion ratio and bulk density respectively, suggesting a good fit. The CCRD was effective in optimizing the process condition for fura as influenced by feed composition, feed moisture and screw speed. The importance of process variables on system parameters and physical properties could be ranked in the following order- Feed Moisture (X2) > Feed Composition (X1) > Screw Speed (X3). Response variables predicted with model equations under optimum conditions were in general agreement with experimental data. The data obtained from the system parameters and physical properties could be used for control of product characteristics and possible projection for the commercial production of millet-soybean based foods like fura.