DETERMINATION OF BIOCHEMICAL COMPOSITION OF SHEA (VITELLARIA PARADOXA) NUT USING NEAR INFRARED SPECTROSCOPY (NIRS) AND GAS CHROMATOGRAPHY

Abstract

The shea tree Vitellaria paradoxa L. is the most prevalent tree crops in northern Ghana with the shea butter fat as the most important product from the tree. Difference in the shea butter fat quality is mainly attributed to bioclimatic variations in temperature and rainfall. The purpose of this study was to apply near infrared, wet chemistry and gas chromatography to characterize the fat and free fatty acid profiles of shea butter fat from three locations (Paga, Nyankpala and Kawampe) in Ghana. The shea nuts from the tree locations in Ghana conformed to the West Africa shea nuts on the global data base on shea nuts compiled at CIRAD. Samples from Paga recorded the highest moisture content ranging between 5.63 % and 12.04 % (dry matter) with a mean content of 6.83 % and a standard deviation of 1.30 % whilst from Kawampe recorded the lowest moisture content with a mean of 5.23 %. Samples from Kawampe recorded the highest fat content ranging from 47.07 % to 57.39 % (dry matter) with a mean content of 52.69 % and a standard deviation of 2.55 % with samples from Paga recording the lowest fat content with a mean of 48.84 %. Stearic acid content of the samples was higher than oleic acid content from the three locations with virtually the same ratio of saturated and unsaturated fatty acids. Correlation between wet chemistry values and near infrared spectroscopy (NIRS) predicted values for moisture content (calibration set) with regression of 0.974 indicating the ability of NIRS to differentiate between nuts from different regions. The nature of the dried shea nuts before processing affected the quality of the shea butter fat as moulded samples recorded higher free fatty acids reducing the quality of the shea butter fat. Fatty acid methyl esters (FAME) analyses indicated that the samples from the three locations in Ghana were mostly saturated with stearic and oleic acids and less of palmitic, vaccenic, linoleic and arachidic acids in the fatty acid profiles of shea butter fats.