Effect of storage period and boiling time of fresh shea nuts on physico-chemical characteristics of kernels and butter

Abstract

Two traditional treatments for shea (Vitellaria paradoxa) butter processing namely storage of fresh nuts and duration of subsequent boiling were studied by using the response surface methodology (RSM) to determine best treatment. Experimental treatments influenced several kernel parameters, such as fat content (38-52% dw), redness (a* values between 6.3 and 11.7), and butter parameters, viz. yield (24 to 36% wet weight of kernel mass), brightness (L* values between 70-80), yellowness (b* values between 16-23), and free fatty acid (FFA) percentage (0.5-2%). On the other hand, the moisture content (6-8%) of the kernels and the peroxide values (2.3 - 3.8 meq O2/kg) of the butter were not affected. Storage for 3 days and boiling for 28 ± 3 min gave the best results, that is, kernels with a moisture content of 7% and a fat content of 50% dw. Butter extracted by traditional technique from these kernels yielded 32% on wet weight of kernel mass with 0.8% of FFA, and 2.5 meq O2/kg of peroxide. This butter can be used for food and cosmetic purposes without refining. Furthermore, the microstructure of fresh shea nuts, studied with Laser Scanning Confocal Microscopy, showed large and small fat globules with some free spaces inside.