Effect of Pre-Treatments on Mechanical Oil Expression from Dika Kernels

The effect of pre-treatments on mechanical oil expression from dika kernels was investigated in this study. The parameters considered were particle sizes (fine and coarse), moisture content (4, 6, and 8%), heating temperature (30, 40, and 50°C), heating time (15, 35 and 45 min) and applied pressure (5, 10 and 15 MPa). The results showed that the oil point pressure of dika kernels reduced with increase in heating temperature and time and moisture content. The highest oil point pressure for coarse particles was recorded at 2.11 MPa; whereas oil point pressure for fine particles was below 1 MPa. The lowest pressure at which oil began to flow was 0.41 MPa (at 50°C and 8.3% MC) while the highest was 0.65 MPa (at 30°C and 4.2% MC). The optimal oil point pressure ranged from 0.55 to 0.65 MPa for fine particles and 1.51 to 2.11 MPa for coarse particles. The least oil yield was at 4% moisture content at 5 Mpa for coarse particles; whereas the highest yield was obtained at 4% moisture content at 15 MPa for fine particles. For coarse particles, resistance to oil flow decreased significantly with increase in moisture content, heating temperature and heating time. The optimal oil expression occurred at pressure range of 0.55 to 0.65 MPa for fine particles and 1.51 to 2.11 MPa for coarse particles. Dika kernel has a high oil content, which makes it valuable for oil production. An understanding of the response of oil yield to various pre-treatments will provide valuable information for the optimization of dika oil expression.