Design, Fabrication And Evaluation Of A Beniseed (Sesamum Indicum L.) Oil Expeller

Some physical and mechanical properties of two Nigerian beniseed accessions (Yandev-55 and E8) were determined at 5 moisture content levels of 5.3, 10.6, 16.1, 22.4, and 28.3 per cent (wet basis). These were used as inputs into designing a beniseed oil expeller, as available ones could not perform effectively with the seed. 

 The determined physical properties were linear dimensions, size, sphericity, bulk and true densities, porosity, thousand kernel weight and coefficient of friction between the seed and different structural surfaces while the determined mechanical properties were the required force, sustained deformation and energy needed to rupture and express oil from the seed. 

  The linear dimensions in terms of major, intermediate and minor diameters were found to be 2.80, 1.83 and 0.66mm for Yandev-55; 3.30, 2.13 and 0.75mm for E8 respectively. The corresponding geometric mean sizes were 1.49 and 1.73mm for the two accessions at 5.3% moisture content levels. These parameters were found to increase with increase in moisture content. The sphericity values for the two accessions were determined to be in the range 0.52 to 0.55 (0.03).  It was found that moisture content had no significant effect on sphericity.

The bulk and true densities decreased from 688 to 613kg/m3 and 1042 to 981kg/m3 for Yandev-55; 674 to 528kg/m3 and 1050 to 988kg/m3 for E8 respectively with increase in moisture content from 5.3 to 28.3% wb. The porosity and thousand kernel weight increased with the increase in moisture content from 5.3 to 28.3% and are within the range of 34.52 to

46.56% and 2.63 to 3.50g respectively. The static coefficients of friction between beniseed and four structural surfaces show that glass has the least value of 0.32, while for mild steel, plywood and concrete, frictional coefficients with beniseed were between 0.39 to 0.59 within the 5.3 and 22.4% moisture content levels. 

The applied force, resulting deformation and required energy ranged from 7.73 to 29.40N, 0.17 to 0.54mm and 0.0013 to 0.0100J for whole and dehulled seeds respectively within 4.1 and 7.7% moisture content (wet basis). 

A portable expeller for beniseed oil expression was designed and fabricated, based on the results of the determined properties. The expression chamber has a barrel of 60mm diameter and a special wormshaft of length 600mm rotating at a speed of 45rpm through a 1hp electric-gear reduction motor. The average capacity of the expeller was 10kg beniseed per hour. A-50litres/h oil filter press was also designed and fabricated for improved oil recovery and better cake utilization.

The efficiency of the expeller in terms of oil recovery from the seed as influenced by wormshaft speed and seed moisture content was evaluated. Increasing wormshaft speed from 30 to 45rpm increased the oil recovery from 37.56 to 79.63% and 33.70 to 74.28% for Yandev-55 and E8 respectively. A further increase to 75rpm decreased the respective oil recovery for the two accessions to 32.47 and 31.92%.  The residual oil-in-cake increased from 14.43 to 43.54% and 17.73 to 43.88% for the two accessions, with the increase in seed moisture content from 4.1 to 10.3% wb. The maximum filtered oil recovery of 79.63 and 74.28% and minimum oil-incake of 14.43 and 17.73% were obtained for Yandev-55 and E8 respectively from a – one pass crushing. These values were obtained at wormshaft speed of 45rpm and moisture content of 5.3% and are in agreement with what obtained for other oilseeds.  The oil quality attributes in terms of relative density, free fatty acid and colour varied from 0.915 to 0.922, 0.98 to 1.01 and pale yellow to golden yellow respectively while the respective moisture and protein contents of the expressed cake were in the range 3.3 to 6.7% and 31.68 to 33.98%.