Development of a laboratory model screw press for peanut oil expression

In the laboratory, small quantities of freshly extracted oil are often required for on-the-spot analysis. This can be obtained at an affordable price from equipment like a model screw press, which is capable of processing small quantities of oil-seed, if readily available. In this study, a model screw press was designed and fabricated. In the design of the screw press, the size of the screw material, the optimum shaft length for a given screw pitch, appropriate shaft speed, the tapering angle of the conical shaft, the maximum shaft, diameter and the inside diameter of the enclosing barrel were determined. A shaft speed of not more than 90 rpm was found to be suitable for working the screw press while the clearance between the shaft and the barrel was 3 mm. Quality evaluation of the product showed that the acid value, the saponification number and the peroxide value of the oil obtained from roasted peanut were lower than that obtained from fresh peanut, implying that oil expressed from roasted peanut is of better quality to the oil obtained from fresh peanut.