Abstract
The levels of nitrite and nitrate in both leaves and stalks of three raw Chinese vegetables (Taasai, Chingentsuai and stalk of garlic) were determined.
The level of nitrate in stored Taasai and in cooked Taasai and Chingentsuai was also examined. The level of nitrate in three raw samples was higher than that of nitrite, with the content of nitrate of 764.1mg% for the stalk of Taasai. The nitrate contents in the stalks of Taasai and Chingentsuai were 2.3 and 15.5 times greater than those in the leaves, respectively.
No significant difference was found in the contents of nitrate in Taasai stored at 25&C. However, the content of nitrate in Taasai stored at 8&C was variable according to the parts, and that in stalk increased slightly on the 5-7 days. Nitrite was not detected.
The residual rates of nitrate in the stalks of Taasai and Chingentsuai after cooking were 69.4~97.8and 62.7-107.6% of raw samples, respectively. The level of elution for nitrate in the leaf of cooked Taasai varied according to cooking methods, with the minimum residual rate of 35.7% of raw samples for boiling. The rate constant of boiling was 0.429.
