The aim of this work is to study the extrusion process and optimum conditions for development of maize-fish based extruded snacks by using Design-Expert® software for Response Surface Methodology (RSM). However, there are still low developed maize-fish extruded products on the market. Mixture of maize flour and dried fish powder was used. Effect of main extrusion conditions like feed moisture, barrel temperature and screw speed were studied. Product responses such as Specific Mechanical Energy (SME), Expansion Ratio (ER), Bulk Density (BD), Water Absorption Index (WAI), Water Solubility Index (WSI) and hardness (H) were estimated and studied using RSM. Maize-fish flour mixture was extruded at moisture content (14-18%), screw speed (400-550 rpm) and barrel temperature (125-175°C). There was a significant effect of feed moisture on all of the estimated responses. Screw speed had significant effect on ER, BD, WSI and hardness of extrudates while barrel temperature had significant effect on SME, ER, WSI and hardness. By increasing the feed moisture BD and hardness increased but SME, ER, WAI and WSI decreased. Increasing the screw speed resulted in reducing BD and hardness, but ER and WSI both were increased. By increasing barrel temperature SME and hardness were reduced while ER and WSI both were increased. Optimization of extrusion conditions for snacks processing was 14.27-15.12% feed moisture content, 400-463 rpm of screw speed and 173.61°C of barrel temperature.
Keywords: Extrusion cooking, Fish, Maize, Response Surface Methodology (RSM), Optimization.