Changes in the Contents of Eight Mineral Elements Contained in Root Vegetables after Cooking

The contents of the eight inorganic elements (Na, K, Ca, Mg, Cu, Mn, Fe and Zn) in vegetables were determined by atomic absorption and flame emission spectrometry after several cooking (boiling for 2,5and 10 min, and heating with micro-wave oven), and the percent of the elements remained in the tissues after the cooking was estimated. The samples used in this study were five root vegetables such as Japanese radish, turnip, carrot, east Indian lotus (root) and edible burdock.<br>1. The remaining amounts of Mg, Ca, Cu, Mn, Fe and Zn in the vegetables after boiling in water were higher than those of Na and K.<br>2. The remaining percent of Na and K after boiling for 2,5 and 10 min were 60,50 and 40%, respectively, whereas those of other 6 elements after boiling for 2,5 and 10 min were 80,80,70%, respectively.<br>3. The remaining percent of elements in the tissues after cooking with micro-wave oven was higher than that in the tissues cooked in boiling water.<br>All the elements except Ca in Japanese radish and edible burdock were remained 80-90% in the tissue after cooking with micro-wave oven. The remaining percent of the immersed tissue (MW I) in the cold water after cooking with micro-wave oven were significantly lower (86±4%) than that of tissue without immersing (94±4%).<br>4. The contents of Na and K in Japanese radish after cooking in boiling water for 10 min were one-third and one-fourth of the contents of raw materials, respectively. The remaining percent of Ca in turnip, carrot and east Indian lotus (root) was relatively high. In the edible burdock the remaining percent of Na, K and Ca were low, whereas that of Mg was high. Remaining percent of Ca and Fe in the edible burdock after cooking in boiling water were similar to those cooked with micro-wave oven, and the average of the remaining percent of Ca and Fe was 57±4% and 96±2%, respectively.