Effects of Cooking on the Mineral and Oxalate Content of Some Legumes

Abstract

The diet of many worldwide cultures depends heavily on various legumes. Legumes form an important item of the diet in developing countries that every effort should be made to retain the nutrition during cooking. The effect of cooking with water and coconut milk on the mineral (Na, K, Ca, Mg, Fe, Cu,Zn,Mn P) and oxalate content of some legumes (Lenus culinaris, Vigna unguiculata Cajanus cajan, Glycine max, Cicer ariethium, Vigna mungo, Vigna radiata, Phosphocarpus tetragonolobus) was investigated using a clay pot and a aluminium utensil. In the case of all legumes investigated the greatest depletion was observed for K, the leaching out being greatest when the legumes were cooked in water as compared to coconut milk.The leaching out ofNa was also greater in water than in coconut milk. Chick pea (Cicer ariethium} leached out the greatest amount ofK. The greatest depletion in Na Content was observed for black gram or ulundu (Vigna mungo). Cowpea (Vingna unguiculata) and winged bean (Phosphocarpus tetragonolobus ) were found to have a tendency to retain most ofthe minerals when compared with other legumes. The loss of Fe was greater for soya bean (Glycine max) when cooked with water in a pan. A noteworthy decrease in Mn and Zn content of lentil s (Lenus culinaris) and black gram or ulundu (Vigna mungo) were observed when cooked with water in a pot. The depletion in the Cu content was the highest for black gram or ulundu (Vigna mungo ). Only mung bean (Vigna radiata) showed a significant depletion in Ca content. The depletion in the P content oflegumes was highest when cooked with water in a pan; mung bean (Vigna . radiata) and Chick pea (Cicer ariethium) showing small losses. Yellow dhal (Cajanus cajan) and mung bean (Vigna radiata) showed the greatest retention in oxalate content when cooked with coconut milk.