EFFECT OF TEMPERATURE ON THE YIELD OF SHEA BUTTER IN AN UNBAFFLED VESSEL AT SELECTED KNEADING PERIOD

1.1     BACKGROUND OF THE STUDY

Shea butter has been a traditional heritage of Africa from time immemorial. The triglyceride which contains a high amount of vitamin A, E, F and some other valuable nutrients is widely used in cosmetics and pharmaceuticals, as well as for domestic use in cooking. Nigeria (as well as many other West African countries) is blessed with abundance of the shea tree (from which the shea butter is obtained). Due to increasing demand for this product, especially in the cosmetic industries across the globe, there is a need for process optimization where

a high yield of shea butter of good grade can be obtained with little energy input.

There are basically three methods of obtaining shea butter from shea nut:

• Solvent Extraction Method
• Use of Mechanical Expeller
• Traditional Method

Solvent extraction makes use chemical solvent such as hexane to absorb the oil from the nut. The oil and the solvent are then separated in another column.

In the mechanical expeller process, an expeller is force driven into the nut contained in a tight container. As the expeller presses against the nut in a screw manner, the oil are forced out and collected at the end.

The traditional method (in southwest Nigeria for example) typically involves crushing of the nuts (after the outer flesh of the fruit has been removed) with mortar and pestle. The crushed nuts are then roasted in a large pot over an open fire (burning of fire wood). They are then ground and well mixed to form a thick paste. The paste formed is kneaded by hand and leg in a large container and with constant addition of water, the butter oil are separated, melted in another pot and cooled.

Of these three methods, the traditional process gives the best quality shea butter and it is by far the most preferred in the most industry. However, this process requires a lot of rigorous exercises. According to Bonkoungou in 2005 for example, it would take one person 20 to 30 hours to produce 1kg of shea butter. Also the level of personal and professional hygiene observed by the local producers may render the locally made shea butter unfit for use in areas such as pharmaceutical and chocolate industry. For example, in a research by Ademola, Oyesola and Osewa of the Department of Agricultural Extension and Rural Development, Faculty of Agriculture and Forestry, University of Ibadan conducted on 120 local producers of shea butter from different Local Governments Areas in Oyo state Nigeria, 95.8% of them do not actually wash the fruit before use.

Although the mechanical expeller process may be preferred in terms of energy saving, but it yields a denatured shea butter which can never compete in terms of quality with the handmade type.

The solvent extraction process gives the highest yield since it is a large scale industrial operation that may be adopted for commercial production. However, it is too expensive as the cost of equipment and operation may be more than the capacity of an individual. Also, the interaction of the solvent with the oil still makes the shea butter formed be of lower quality than the locally made product.