Effect of Cassava Flour Substitution on some Quality Characteristics of Heat Pump Dried Extruded Fish Feed

Abstract. Fish is a good and healthy source of protein but 60% of its cost of production goes to fish feed in most states in Sub Sahara Africa. This research looks into the possibility of substituting maize with cassava flour in fish feed production. The present study examined the effect of substitution of maize with cassava flour at varying moisture contents on heat pump drying and some quality attributes including strength properties, durability index, micro-structure and floatability. The samples identified as S1- S6, were prepared from proven fish feed ingredients from Nigeria substituted with three levels of cassava flour before being extruded at steady state at 3 moisture contents (30, 35, and 40% db) and 150rpm extruder speed in a single screw extruder. Heat was generated through viscous dissipation. Drying was done with an open loop heat pump dryer while a JSM 7600F Jeol ultra-high resolution field emission gun scanning electron microscope (FEG-SEM) was used to study the microstructure of the fish feeds. Results showed that pellet durability was proportional to the source and concentration of starch in the samples and some of the samples floated in water. The Coefficient of performance (COP) decreased with increase in ambient temperature; the average COP attained was 4.77. The thermal efficiency of the heat pump dryer was 92.45%. The scanning electron microscopy indicated that cassava substituted samples lack some elements required of fish feed. Extrusion resulted in changes in mineral composition of fish feed blends. Further areas that needs be researched were suggested.