Quality of traditionally processed shea (Vitellaria paradoxa) kernels and shea butter

Abstract The shea tree is an endogenous and multipurpose tree from the Savanah zone of Africa, mostly used for its fruits and the fat extracted from its kernels, commonly known as shea butter. The butter is used for cooking and medicinal purposes by local populations, and in cosmetic products as well as a cocoa butter substitute in chocolate in others areas of Africa and at the international level. The butter is generally extracted by traditional methods, which vary throughout the production zones but involve some common processing operations viz. boiling of the fresh nuts, sun drying, shelling, crushing, roasting, milling, churning, and heating. This thesis investigated the influence of traditional processing of shea on quality attributes of shea kernels and butter. The results showed that 2 mains techniques (differing in the heat treatment applied to the fresh nuts) are used to process shea fruits after their collection: the boiling followed by sun drying technique and the smoking technique. Boiled and sundried kernels contained a higher fat content (48 % dw) and yielded more butter (30 % of kernel mass) than smoked kernels that had a fat content of 39 % dw. The butter extracted from the boiled kernels had a better quality than the butter from smoked kernels with respect to the unsaponifiable fraction (7 %), tocopherol compounds (125 mg/g), peroxide value (8 meq O2/kg), and FFA (2 %). Some processing operations, namely the storage of fresh nuts as related to their boiling time and the roasting of kernels, were optimized using the response surface method to design the experiments. The conditions to obtain an optimal quality of kernels are to store the nuts for 3 days and boil them for 28 ± 3 min. Subsequently, optimal roasting conditions for kernels were found to be 15 min at 171 ºC, which resulted in kernels with a fat content of 49 % dw, a butter yield of 32 %, and butter with a FFA of 1.2 %. The results also revealed that shea butter extracted from roasted kernels contained more volatile compounds (58) than that from unroasted kernels (27). Additionally, storage temperature and storage duration significantly affected some quality characteristics of shea butter, whereas the influence of local packaging materials was less pronounced Shea processors are advised to process shea fruits by integrating the optimal conditions of storage of fresh nuts, boiling and roasting found in this research, then pack the butter in clean and opaque plastic and store it in a relatively cool area to maintain the quality of the product during prolonged storage periods. Areas for future research were identified for further improvements of local shea processing.