Abstract:
This study was conducted to evaluate the performance of a preconditioner and the
qualities of the extrudate under varying operating conditions (screw speed, moisture content
of the fed materials and the fill ratio). Conveyance efficiency, energy requirement, water
absorption index, sinking velocity and floatability were measured and analysed. Three
moisture content levels (20%, 30% and 40%) wet basis, three screw speeds (162.5 rpm, 180.6
rpm and 235.3 rpm) and fill ratios (2.854, 3.068 and 3.776) were used for the production of
preconditioned fish feed. Conveyance efficiency of the extrudates decreases with increased
moisture contents. Changing the moisture contents of the mix had no significant effect on the
conveyance efficiency (p > 0.05). There was no significant difference in the average energy
requirement of the preconditioner under varying moisture contents, screw speeds and fill
ratios (p< 0.05). Water absorption index (WAI) of the fish feed increased with increase in
moisture contents. Increasing moisture content from 20% to 40% increases the water
absorption index by 70.69%. The results show that extrudate has greater swelling power as
the moisture content increases. Water absorption index, sinking velocity and floatability were
not significantly affected by moisture content (p > 0.05). There was no significant difference
in the mean sinking velocity of the extrudate under different moisture content, screw speed
and fill ratio (p > 0.05). The floatability was highest at 30% moisture and lowest at 20%
moisture content. The fill ratio of 3.068 produced the greatest floatability of 43.42%. The
highest conveyance efficiency was recorded when the preconditioner was operated at 20%
moisture content, screw speed of 180.6 rpm and fill ratio of 3.068. The highest energy
requirement of the preconditioner is 28.28 KJ. The study revealed that it is better to fix the
preconditioning variable at the moderate values to enhance the preconditioning performance.
