A study of the traditional method of processing shea fruit into shea kernel: effect of some initial processing parameters on quality of the shea kernel

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The objective of the study was to determine the effect of certain inlet processing parameters like blanching temperature, blanching time, drying method and drying time on the quality of shea kernel produced from shea nut. The Dagomba traditional shea nut processing method was used. Freshly harvested shea nut was blanched at 70°C for 30 mm and then dried using two different drying methods: solar tent drying and sun drying. Blanching reduced the moisture content of the kernel by 20.58% and moreover, enhanced drying. Solar drying method dries the kernel faster than the sun drying method. The free fatty acid content of the kernel reduced by 86.12% after blanching. There was respective decrease of 72.12% and 74. 04% in free fatty acid content of the solar-dried blanched and sun-dried blanched kernel after 336 hr of drying. The free fatty acid content of the unbianched shea kernel decreased by 20.96% at the end of the solar drying. The peroxide value of the kernel increased by 2.52% after blanching. The peroxide value of the unbianched kernel decreased by 3 9.62% after it had been solar-dried for 336 hr. There was 3.95% decrease in the total tocopherol content of the kernel after blanching. The drying times had significant effect (P<0.05) on the tocopherol content of the kernel over the 336 hr drying period. The compressive strength of the kernel improved after it had been blanched and dried using the solar tent dryer. The compression stress was inversely proportional to the moisture content up to critical moisture content. Below the critical moisture content, as the moisture content further decreased, the force required to let the kernel fail decreased and consequently the stress also decreased. The respective required compression stress for 10% and 1% deformation followed similar trend. Temperature was found out to have influence on enzymatic browning of the kernel. The brownish color of the solar-dried unblanched kernel was the most vivid (a* = 13.97), followed by that of the solar-dried blanched and then sun-dried blanched shea kernel.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Chemical Engineering, 1997