Effect of cooking on nutrient content of tropical root crops from the south pacific

Abstract

Abstract The changes in nutrient content of sweet potato ( Ipomoea batatas ), taro (Colocasia esculenta), yam ( Dioscorea alata ) and cassava ( Manihot esculenta ) as a result of boiling, steaming and baking were determined. These changes were similar for all root crops (except in the case of sweet potato) and may be explained largely in terms of breakdown of nutrients with heat and in solubilisation of water‐soluble constituents. Major changes observed were (1) an approximate doubling of the apparent dietary fibre content due to formation on cooking of starch which was resistant to degradation by the enzymes used in the starch assay procedure; (2) a decrease in the content of potassium by up to one‐fifth and smaller decreases of other water‐soluble salts; (3) a very large increase in the maltose content of sweet potato on cooking, which did not occur with the other root crops. In terms of human nutrition dry baking, generally speaking, appears to be the best method of cooking, followed by steaming, then boiling with retention of water and, finally, boiling with discarding of the water. However, in the particular cases of cassava and the edible aroids, which include taro, antinutritional factors may need to be removed by special cooking methods.