The effect of cooking, steaming and frying on the content of allantoin, which can prevent inflammation and ulcers in the human body, in Dioscorea (tsukuneimo) was determined by HPLC. A sample of tsukuneimo (30×30mm,2.5-10mm in thickness) immersed for 12 hr in commercial vinegar diluted by ten times resulted in 0-50% of allantoin remaining. The allantoin remaining in tsukuneimo after cooking for 10 minutes was 50-80% with boiling,70-80% with steaming and 80-90% with frying.
