Putting the press to the test : effects of temperature on Shea nut oil output

Abstract

In northern Ghana, part of a belt reaching from Sub-Saharan Africa to northern Uganda, women collect and process Shea nuts for their valuable oil. This oil is then used in various cosmetic, cooking, and medicinal products. However, the traditional process to extract oil from Shea kernels is time and labor intensive, and the quality is inconsistent, preventing it from being a primary source of income. In order to address these problems, a hydraulic jack press for extracting Shea oil was designed for a woman's co-operative in the village of New Longoro during the summer of 2009 as part of the International Development Design Summit. This thesis presents the results of a study of the effect of temperature and roasting on the Shea oil yield of a hydraulic jack press in order to evaluate its practicality. Extraction efficiency was measured for ground Shea kernels, either unroasted or roasted, for pressing temperatures ranging from 50-70*C. It was found that a pressing temperature of 60-62°C produced the highest oil yields for both roasted and unroasted nuts, with unroasted, ground kernels producing slightly more oil than roasted, ground kernels. The highest yield produced was (23 ± 2.8)% for unroasted Shea kernels at 60.7°C. Furthermore, it was observed that the optimal press chamber configuration is one with perforations along the circumference of the cylinder and on the base with slits to allow oil to escape. It was also confirmed that post-press filtering will be necessary to purify the oil for marketability. Finally, although the initial results are promising, more investigation is needed in order to determine the economic viability of using the hydraulic jack press.