Levels of essential and non-essential elements in raw and processed Lupinus albus L.(White Lupin, Gibto) cultivated in Ethiopia

Abstract

White lupin (Lupinus albus L.) cultivated in Ethiopia is locally known as ‘Gibto’. Its seed is used as a snack, for the preparation of local alcoholic drink, ‘Areqi’ and as ‘Shiro’ flour for the people living in the north western part of Ethiopia. It is also used for maintaining soil fertility and as a food. Certain elements are essential for plant growth, for animal and human health. However, if present in excessive concentrations they become toxic. Other elements are non-essential and toxic to human health even at trace level. Even though the levels of four of the elements are reported, there is no report in literature on the levels of other essential and non-essential elements in white lupin cultivated in Ethiopia. Therefore, this study was carried out to determine the levels of essential (K, Na, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn) and non-essential elements (Pb and Cd) in raw and processed grains Lupinus albus L. (Gibto) cultivated in Ethiopia (particularly Debretabor, Dembecha and Kosober). The micro and macro-nutrient levels of the raw and processed white lupin grains were determined by flame atomic absorption spectrometry. Known weight of dried raw and processed samples were wet digested using 2 mL of HNO₃, 1 mL of HClO₄ and 1 mL of H₂O₂ at temperature round 270 ⁰C with 3 hours total time. The mean metal concentration (µg/g dry weight basis) ranges in raw and processed white lupin samples, respectively, were: K (5142-6215, 1100-1222), Na (31.9-50.1, 15.1-31.1), Mg (1739-2159, 629-759), Ca (502-967, 709-1284), Cr (11.3-17.6, 9.40-10.3), Mn (1657-4095, 1075-2265), Fe (77.9-92.8, 70.7-83.8), Co (16.2-16.6, 16.7-17.2), Ni (12.0-15.6, 6.90-11.7), Cu (4.80-9.90, 5.10-12.2), Zn (40.3-53.6, 55.6-64.6) and Pb (10.8-16.4, 9.90-13.1). The level of Cd was below method detection limit in both the raw and processed samples from all the sample sites. The concentrations of all the nutrients were higher in raw as compared to processed white lupin samples except for Ca, Co, Cu and Zn samples from all of the sampling sites. Analysis of variance (ANOVA) at 95% confidence level indicated that there is significant difference between the mineral contents of raw and processed samples from the three sample sites. Pearson correlation indicated positive correlation between most elements in both the raw and processed samples. In general, white lupin is rich in essential elements and safe to consume and could be an alternative source of the essential elements to the individual daily intake.

Key words: Lupinus albus, legumes, food, elements, Ethiopia