Etude des paramètres opératoires de pressage mécanique des amandes de Vitellaria paradoxa Gaertn C.F. (karité)

Abstract

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most difficult oleaginous resources to extract by traditional way. In Burkina Faso, where production of sheanuts is estimated at 70000 tons per year, presses manufactured locally are used to improve the production. In order to optimize the handcraft process of sheabutter production, extraction parameters of Vitellaria paradoxa Gaertn C.F. were studied under laboratory controlled conditions on 3 g samples of ground almonds using a uni-axial compression test machine specifically instrumented for this purpose. The studied operational parameters were the grinding (unsieved sample 0.5 mm<Ø<5 mm ; sieved samples 0.5 mm<Ø<1 mm ; 1 mm<Ø<2 mm ; 2 mm<Ø<4 mm ; 4 mm<Ø<5 mm), the heating temperature (30; 50; 70; 90; 110; 130; 150°C) and the extraction pressure (7; 10; 13.4; 15; 16.17; 17.44; 20; 22.43 and 25 MPa). The grinding has favourably influenced the extraction rate. The finest sieved fraction (0.5 mm<Ø<1 mm) presented the highest extraction rate, 84%. When using unsieved samples, the best results were obtained with a heating temperature of 90°C and an extraction pressure of 20 MPa. In these conditions, the extraction rate reached 78% and the chemical characteristics of the sheabutter were not altered. As a result, a significant increase of the handcrafted presses efficiency could be reached by simple and inexpensive modifications as an increase of the pressure applied to the product, by a decrease of the pressing chamber diameter