Modelling and Optimisation of Oil Expression from Trunk Fish (Mormyrus rume)

Trunk fish (Mormyrus rume), is found in tropical and subtropical freshwaters bodies, particularly in west African region. They are cultured mainly for food and commercial purposes. Fish oil expression is the process of mechanically pressing oil from solid materials. The aim of this study was modelling of contentious oil expressed from trunk fish. With the objectives as to predict the oil yield from the optimum parameter; develop and validate the mathematical model for continuous mechanical oil expression. The current investigation used Response Surface Methodology (RSM) to optimise oil expression from Trunk fish. Shaft diameter was varied from 32.5 to 42.5mm, Shaft Speed from 25 to 85 rpm, pitch height from 10 to 30 mm and applied pressure from 10 to 25 N/m2 to study their effects on fish oil yield with the aid of a two-level, four-factor central composite design (CCD). The second-order model developed accurately predicts the optimum oil yield. Highest oil yield was obtained from the empirical model as 27.8% at a screw diameter of 42.5mm, screw speed of 55rpm, pitch height of 20mm and applied pressure of 20 N/m2. It was observed that the optimum oil yield of 27.8% is higher than the maximum oil yield of 27.1% with a 0.7% error, validating the model equation using optimal parameters: shaft diameter (42.5 mm) and applied pressure (20 N/m2). This study concludes that optimising the extruder shaft enhances oil yield and efficiency. It is recommended that the developed model be applied in the manufacturing of shafts to maximise fish oil expression oil yield.