There is high demand for Shea butter in the international market due to its industrial potential and rich chemical constituents (mature kernel contains about 61% edible fat). Shea butter can be used for food, medicinal as well as industrial purposes such as cakes and margarine, in cosmetic and pharmaceutical industries. Despite its wide usage, Shea butter processed in Nigeria is characterized by low quality.
A study of the effect of fungal contamination on the quality of processed Shea butter and identification of the sources of contamination along the different processing stages was carried out with the aim of identifying the fungi associated with processing and to deduce the degradative effect of the associated microbial communities on the butter quality.
Shea butter samples were obtained from processing sites in Kwara and Niger States of Nigeria. Microbological and chemical analyses of the samples were done using standard conventional methods.
The fungi associated with the local method of processing were Aspergillus niger, A. persii, A. flavus, A. niger (aggregate), A. oryzae and A. fumigatus.The identification of sources of microbial contamination and traceability of fungal organisms to processing stages was analyzed using molecular methods. The results revealed that the fungi contaminated the processing line from the use of unsorted Shea kernels and from the environment. Aspergillus oryzae and A. niger increased the yellow portion of the olein from 16.2Y to 40Y and 20Y, respectively while A. persii, A. fumigatus and A. flavus reduced the yellow fraction of the oil from 16.2Y to 10Y, 7Y and 8Y, respectively. The difference between values for experimental and control for pH and relative density was not significant while that of lipophilic activity of the isolates was highly significant. The presence of the different Aspergillus species affected the olein fraction of the Shea butter such as release of high amounts of free fatty acids and peroxide, thereby reducing butter quality.
Changes in chemical parameters brought about by Apergillus presence has implications for health, as well as for pharmaceutical and cosmetic industries.