PALM KERNEL OIL EXPRESSIO N BY UNIAXIAL COMPRESSION

Abstract

Palm kernel oil yield was found to be dependent on operative processing variables including: heating
temperature, applied pressure and particle size to which ground palm kernel samples of fine and coarse
particle sizes were subjected to using a Piston-cylinder Rig under an instrumented hydraulic uniaxial
compression. The effects of heating temperature and applied pressure on the oil yield was investigated at
heating temperatures of 70, 90, 110, and 130 0C and applied pressures of 6, 9, 12 and 15 MPa. The oil
expressed from each temperature level at optimum applied pressure of 15 MPa was subjected to
laboratory analysis using AOAC 1991 recommended method at the analytical and quality control
laboratory of the Global Soaps and Detergents Industries, Ilorin, Nigeria. From the results, the highest
palm kernel oil yield obtained was 32.15 % at optimum conditions of 15 MPa applied pressure for 10
minutes and 110 °C heating temperature for 30 minutes on samples of 4.5 % moisture content dry basis.
This yield corresponds to an expression efficiency of 71.8 % of the total palm kernel oil content. Increase
in oil yield was recorded at corresponding increase in heating temperature and applied pressure, but the
oil yield begins to drop after an optimum heating temperature of 110 °C was attained. Oil yield from fine
particle size of palm kernel was discovered to be significantly different from that obtained from coarse
particle size at 5 % level of confidence.
The result of the physio-chemical characteristics of the palm kernel oil at temperature of between 70 -
130 ⁰C are: Free fatty acid 4.02 - 4.63 %; Acid value 11.29-12.0 mgKOH/g; rancidity index 2.4R.21Y
1.9R.10Y; saponification value 246.57-243.80mgKOH/g; viscosity 140 60cps and specific gravity
0.908-0.894. The result indicates that the quality of the expressed oil decreases as the heating temperature
increases.