Effect of cooking on the mineral and antinutrient contents of the leaves of seven accessions of Colocasia esculenta (L.) Schott growing in South Africa

Abstract The effect of cooking on the mineral and antinutrient contents of the leaves of seven accessions (UFCe1 UFCe7) of Colocasia esculenta (L.) Schott growing in South Africa was investigated. Cooking significantly reduced the phosphorus, potassium and zinc contents. After cooking, calcium, magnesium, sodium and copper levels were not significantly different in almost all the accessions tested in the study. In contrast, cooking appears to increase the iron levels in all the samples, though this was not significant in most of the accessions. The manganese levels were also reduced with cooking in four accessions while UFCe3, UFCe6 and UFCe7 showed increase in manganese level after boiling. Generally, potassium and magnesium contents were reasonably high in all the accessions. High dietary potassium in humans plays a protective role against hypertension, stroke, cardiac dysfunctions, renal damage, hypercalciuria, kidney stones and osteoporosis. The results further indicate that the accessions are good sources of potassium, magnesium, sodium and calcium. Salts of these minerals are known to regulate the acid-base balance of the body. Boiling remarkably reduced the level of the anti-nutritional factors, thereby improving the food quality of all the accessions tested in this study. Boiling for 5 min led to 16-78% drop in oxalate level, 28 61% in tannin and 17 41% reduction in phytate contents in some of the accessions. Boiled C. esculenta leaves may therefore serve as a good source of iron. This may imply that the consumption of the leaves of cocoyam may increase the blood level and may therefore be recommended as a good food for anemic patients.