Determination of the Physicochemical Characteristics of Sesame Seed (Sesamum indicum) and the Underlying Soil in Tegede District, Ethiopia

Abstract

Background: Sesame (Sesamum indicum) is a member of the Pedaliaceae plant family, and it is one of the world most important and oldest known oil seed crops. Investigations on the physicochemical properties of plants and the underlying soils have critical importance in crop production and productivity. Methods: The determination of moisture, ash, protein, crude fiber, crude fat and total carbohydrate contents of sesame seeds and soil samples was performed following standard methods of Association of Official Analytical Chemists. The concentrations of some essential major elements (Ca and Mg) and trace elements (Fe, Zn, Cu and Ni) in samples were also determined by using flame atomic absorption spectroscopy. Results: The sesame seed samples contained high levels of fat (52.86±1.52%), followed by crude protein (23.52±0.89%). The amount of carbohydrate found in the seed samples was (14.51±1.82%), moisture (5.2±0.20%), ash (4.83±0.53%) and the crude fiber (4.26±0.59%). The elemental analysis results indicated that Mg is most abundant 525.41±1.25 mg/kg, followed by Ca 453.24±38.11 mg/kg. The concentration of Fe determined in the seed samples was 37.76±1.43, Zn 14.65±2.19 mg/kg, Cu 7.26±0.84 mg/kg, Mn 2.30±0.34 mg/kg and Ni 1.77±0.16 mg/kg, which was the least abundant element in the seeds. Regarding the physicochemical properties of the underlying soil, the measured pH value was 5.4, temperature 20.7 oC and the moisture 7.1%. The elemental composition results indicated that soil samples had the highest concentration of Mg 507.50±13.77 mg/kg, followed by Ca 418.02±49.12 mg/kg, Fe 212.62±2.64 mg/kg, Cu 28.82±0.14 mg/kg and Zn 28.75 ±1.92 mg/kg. Conclusion: The sesame seeds have good nutritional value with high amounts of fat and protein. The seeds also contain significant amounts of Mg and Ca, where the amounts were comparable with that determined in the soil samples. Regarding the essential trace elements, Fe, Cu and Zn, the soil contained 2-6 times higher than that found in the sesame seeds.