Abstract

Nutrient level at harvest of vegetables is an important aspect in the efforts to combat food and nutrition insecurity in developing countries. However information on the nutrient levels at different maturity stages of most indigenous African green leafy vegetables is scanty. This study was undertaken to determine the levels of vitamin C, iron and zinc in Amaranthus cruentus, Cleome gynandra and Solanum villosum at different stages of maturity. The vegetables were planted on plots and harvested at 21, 28 and 35 days. At each stage, about 500 to 600 g of the edible part was harvested and standard chemical analyses procedures were followed to determine the levels of vitamin C, iron and zinc. Vitamin C increased significantly (p<0.05) with maturity in all vegetables except S. villosum Nduruma BG 16 which had similar values for stage I and II. Vitamin C content was highest (163.4 ± 2.3 mg/100 g) in C. gynandra stage III and lowest (27.7 ± 3.9 mg/100 g) in S. villosum SS 49 stage I. Iron content increased significantly (p < 0.05) at all maturity stages. Amaranthus cruentus Madiira Ex zim had the highest iron concentration (99.9 ± 3.7 mg/100 g) while S. villosum Olevolosi SS 49 had the lowest value (23.1 ± 1.5 mg/100 g). Zinc content decreased with plant age, highest values (7.8 ± 0.4 mg/100 g) were observed in C. gynandra at the first stage of maturity which was reduced to about half at the third stage of maturity (3.9 ± 0.0 mg/100 g). There were marked differences in nutrient content among the various varieties and cultivars involved in this investigation. Iron and vitamin C concentrations increased with plant age whereas levels of zinc decreased with plant maturity. Consuming the different vegetables varieties would be the best approach to get all the essential nutrients in adequate amounts. Further studies are needed to investigate organoleptic acceptability of these vegetables at the different stages of maturity.

Key words: Iron, zinc, vitamin C, maturity stage, green leafy vegetables.