Evaluation of physicochemical properties of Jatropha curcas seeds from four different agro-climatic areas of Ghana

Abstract

Jatropha curcas is a drought resistant multipurpose small shrub/tree with significant economic importance because of its several potential agricultural, industrial and medicinal uses. The study was conducted to provide quantitative data on the physical and chemical properties of seeds and kernels of Jatropha curcas grown locally in four different agro-climatic areas of Ghana (1. Nyankpala, Northern Region, 2. Dambai, Volta Region, 3. WA, Upper West Region, 4. Techiman, Brong Ahafo Region), that differ in agro-climatic conditions. The average seed weight was between 0.65 – 0.73 g and average kernel and shell weights ranged between (0.41- 0.45 g) and (0.24 – 0.28 g) respectively. The kernel forms larger proportion of the seed and the percentage kernel weight of whole seed was highest in seeds obtained from Nyankpala, sample 1 (62.74 %) and lower in seeds from WA, sample 3 (61.19 %). The seeds have dry matter content of (93.13 – 94.18 %), crude protein (18.21 -19.97 %), lipid (36.52-38.64 %), carbohydrate (14.70 – 16.64 %), crude fibre (14.14 – 19.04 %) and total ash (5.03 – 5.71 %). The kernels of Jatropha samples were very rich in lipid (55.51 – 56.83 %) that did not vary significantly (p > 0.05) among the four samples. The kernels also contained high crude protein that varied between (23.08 – 25.88 %). Crude fibre was low in the kernels (3.68 – 5.52 %). The seeds and kernels of Jatropha curcas samples also contained varying amounts of antinutrients such as crude phorbol ester, phytic acid and tannins. Crude phorbol ester concentrations in the seed samples are sample 1(5.35 mg/g), sample 2 (6.20 mg/g), sample 3(5.30 mg/g) and sample 4(6.82 mg/g). However, the concentration of crude phorbol ester in the kernels (1K, 2K, 3K, and 4K) ranged between (5.0 – 6.45 mg/g). The phytic acid content (% dry matter) in seeds and kernels were between the range (8.71 -10.15 %) and (7.88-9.50 %) respectively. Tannins content in the kernel was low (0.05 – 0.09 % tannic acid equivalent).