Effect of Processing on the Elemental Composition of Selected Leafy Vegetables
The elemental composition of leaves of Vernonia amygdalina, Gnetum africana, Gongronema latifolium and Ocimum gratissimum subjected to different processing methods were investigated. Processing methods employed include oven drying, sun drying, fresh milling, steaming and a combination of these while the mineral elements investigated include Na, Ca, Mg, Fe, Zn, and P. The tested vegetables were found to have some nutritional potential with high levels of mineral elements. Oven drying was the most effective method of retaining the minerals followed by sun drying while a combination of steaming and sun drying caused the highest loss in the levels of all the mineral elements tested for in the vegetables. Other processing methods employed caused significant loses in the levels of minerals at P<0.05 in all the tested vegetables. Although Na, K, Ca and P were randomly affected by the different processing treatments, the Na/K and Ca/P ratios were retained after the treatments. Thus, for maximum retention of mineral elements in the leaves, oven drying and sum drying methods are recommended.
Keywords: Vegetables, minerals, processing.