The nutrient content of five traditional South African dark green leafy vegetables - a preliminary study

Abstract

The nutrient content (proximate composition, vitamin B2, ß-carotene, iron, zinc, magnesium, calcium and phosphorus) of 5 traditional dark green leafy vegetables, traditionally consumed by rural inhabitants of South Africa (SA), was determined in this study. The nutritional dilemma in SA, with many children and adults suffering from micronutrient deficiencies, is a strong motivation for determining the nutritional composition of traditional foods. The moisture, protein, ash and fat content in the raw leaves per 100 g ranged from 81.0 to 89.9 g/100 g, 3.49 to 5.68 g/100 g, 1.42 to 3.23 g/100 g and 0.12 to 0.36 g/100 g respectively. There was an increase in moisture content in the cooked leaves, while the protein, fat and ash decreased during the cooking process. Raw misbredie (Amaranthus tricolor), pumpkin leaves (Curcubita maxima) and cat's whiskers (Cleome gynandra) had a high iron content compared to cowpea leaves (Vigna unguiculata) and wild jute (Corchorus olitorius), which in nutritional terms might play a role in combating iron deficiency in SA. The zinc content ranged from 0.5 to 1.0 mg/100 g, while the magnesium ranged from 54.7 mg to 146 mg/100 g. As expected, the minerals decreased during cooking. Cowpea leaves was the poorest source of minerals compared to the other leafy vegetables but had a good index of nutritional quality for protein. Raw and cooked pumpkin leaves had the highest index of nutritional quality for protein. Both raw and cooked leafy vegetables contained high levels of beta-carotene (with total beta-carotene levels in the range of 796–6134 μg/100 g) but low levels of vitamin B2 (0.01–0.12 mg/100 g).