Optimization of Aqueous Extraction Conditions of Unrefined Shea Butter Using Response Surface Methodology

Abstract

The optimum condition for the extraction of unrefined Shea butter via (aqueous) traditional extraction method was determined using response surface methodology (RSM). A central composite design (CCD) was used to investigate the effect of three independent variables, namely- roasting time (min), roasting temperature (°C) and clarification time (min) on the responses, oil yield (%), peroxide value (meq/kg), free fatty acid (%) and unsaponifiable matter (%). The CCD consisted of 8 factors, 6 axial points and 5 central points to give total of 19 experimental points. Data were analyzed using design expert 7 software. Second order polynomial terms were used to predict the responses. The result indicated that oil yield, unsaponifiable and peroxide value were optimized with all having R2 > 80% except for free fatty acid which was not a significant response (p = 0.58). The optimal extraction conditions for optimizing the responses were 106°C, 120 min and 90 min of roasting temperature, roasting time and clarification time respectively. Predicted response values were in agreement with experimental values indicating the success of RSM in optimizing the quality parameters of Shea butter. This result also reflects that it is more suitable to roast Shea kernel at low temperature for longer duration than at higher temperature for short time which is the current practice in Nigeria.