CASSAVA FLOUR SUBSTITUTION AND MOISTURE CONTENT VARIATION ON SOME QUALITY CHARACTERISTICS OF HEAT PUMP DRIED EXTRUDED FISH FEED
This 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 various levels of cassava flour before being extruded at steady state at 3 moisture contents (30, 35, and 40% db) in a single screw cooking extruder. Drying was done with an open loop heat pump dryer while a scanning electron microscope (FEG-SEM) was used to study the microstructure of the fish feeds. Results showed that drying rates and pellet durability were proportional to the source and concentration of starch in the samples. Some of the samples floated in water. The Coefficient of performance (COP) of the heat pump used for the drying decreased with increase in ambient temperature; the average COP being 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. Also, extrusion cooking resulted in changes in mineral composition of fish feed blends.
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