Onion bulbs and stalks, proximate, nutrient elements, vitamins A and C, oxalate.
The proximate, macro and trace-elements, vitamins A and C, and oxalate compositions were determined in onion bulbs and their stalks from three agricultural fields in Aliero, Kebbi state. The bulbs and stalks contained closely related mean values of 93.11g/100g and 91.70g/100g, 6.48g/100g and 6.74g/100g as moisture and crude protein contents respectively. Values of 4.26g/100g (bulbs) and 13.56g/100g (stalks) were observed as ash content, while their fibre contents were 13.56g/100g (bulbs) and 9.33g/100g (stalks). The macro element concentration in the bulbs was in the order Ca>Mg>K>P>Na while that of the stalks was Mg>Ca>K>P>Na. For the trace elements, the order was Fe>Zn>Mn>Cu>Pb>Ni>Cd for the bulbs and Fe>Mn>Zn>Cu>Ni>Pb>Cd for the stalks. Only Iron concentrations were observed to be higher than (100-500μgg-1) the normal Fe concentrations in plants. There were significant differences (p<0.05) in the mean concentrations of Fe, Mn and Pb with stalks having higher
values for Fe and Mn. Both the oxalate and vitamins A and C contents of the bulbs were significantly (P<0.05) high when compared to other reported values. The presence of oxalate in
both the bulbs and stalks could affect the bioavailability of some nutrient elements. The results generally indicate that the bulbs are more nutritious than the stalks. With the current problem of Fe deficiency as identified by WHO, onions could be another source of helping the situation.
Keywords: Onion bulbs and stalks, proximate, nutrient elements, vitamins A and C; oxalate