Mineral Content of Five Tropical Leafy Vegetables and Effect of Holding Methods and Time

Objective: This study was undertaken to determine the mineral content of five popular leafy vegetables consumed in southeast Nigeria and to evaluate the effects of time and methods of holding on minerals.
Methodology: Five vegetables Pterocarpus soyauxii ("oha"), pterocarpus santalinidies ("nturukpa"), Gongronema latifolium (utazi), Corchorus olitorious ("ahihiara") and Amaranthis Hybridus ("green") were harvested from farm. Some of the leafy vegetables were wrapped and some unwrapped. They were analyzed for minerals using standard analytical methods. Analysis of variance (ANOVA) at 5% level of significances was also calculated for mineral content of fresh leafy vegetables. The mean were separated using Turkey's test. All the experiments were carried out in triplicates.
Results: Among these five leafy vegetables, Gongronema latifolium ("utazi") had the highest content of potassium (78.5mg), calcium (68.30mg), magnesium (54.60mg) and iron (7.83mg) per 100g of each of the leaf. Amaranthis Hybridus ("green") recorded the highest sodium content of 38.90mg/100g. There was decrease in the level of minerals in all the five leafy vegetables with increases in the time of holding. The rate and percentage of loss of minerals among the leafy vegetables varied depending on the method and time of holding. Unwrapped leafy vegetables held day and night in a room recorded the highest percentage loss of minerals. While the wrapped leafy vegetables recorded the lowest percentage loss of minerals. The unwrapped Pterocarpus santalinidies ("nturukpa") held day and night in a room recorded the highest loss of 54.71% sodium in four days.
Conclusion: The rate of metabolism of nutrients (minerals) in harvested leafy vegetables was influenced by their temperature, the lower the temperature the less the loss of minerals.