Comparative studies of thermophysical and physicochemical properties of shea butter prepared from cold press and solvent extraction methods

Abstract

Over the years, the importance of shea butter, for its exceptional use in food and cosmetics industries, has been over-emphasized. This work compares the qualities of shea butter produced from two methods of extraction with respect to thermal stability and physicochemical properties. Two different extractions; Soxhlet extraction (SBSE) and cold press (SBCP) methods were carried out, and proximate analysis, viscosity, specific gravity and refractive index of the butter were equally analyzed. The activation energies (Ea) were determined from Arrhenius-type plots, and the enthalpy, entropy as well as Gibb’s free energy were obtained from Eyring plots. Proximate analysis showed that the nuts contains 5.30% moisture, 16.45% crude protein, 4.51% ash, 46.50% crude fats, 4.45% crude fibre and 23.24% carbohydrate. Peroxide values of 4.00 and 6.50 Meq/kg, acid values of 3.50 and 9.54 mg KOH/g, iodine values of 53.82 and 54.93 g/100 g and saponification values of 172.2 and 185.7 mg/KOH were obtained for the shea butter from Soxhlet extraction (SBSE) and cold press (SBCP) methods, respectively. SBSE contains higher level of unsaturated fatty acid, oleic and linoleic acids, than SBCP, while the trend was reversed in relation to the saturated fatty acid contents. The viscosity, specific gravity and refractive index of both SBCP and SBSE are within the same range. The viscosities of the butters decrease with temperature and the activation energies (Ea) determined from Arrhenius-type plots are 170.19 and 190.97 J/mol for SBSE and SBCP, respectively, as a measure of their thermal stability. The enthalpy, entropy and Gibb’s free energy of activation obtained from Eyring plots are approximately the same for the butters from the two extraction methods and have the values of approximately 2900 J mol−1, −165 J mol−1 K−1 and 52.10 kJ mol−1, respectively, showing that the processes involved are endothermic and of non-spontaneous nature. The butter extracts exhibit good thermophysical and chemical properties and could be used as valuable industrial raw materials.