Toonium contains relatively high levels of nitrates and nitrites, which can form carcinogens in the body. However, blanching toonium in boiling water for about one minute can remove more than two-thirds of its nitrates and nitrites. Therefore, it is recommended to blanch toonium before cooking. Moreover, the unique aroma of toonium comes from its essential oils, which are insoluble in water, so blanching does not affect the dish's flavor.
In addition, there are three other categories of vegetables that require blanching. The first category includes vegetables high in oxalic acid, such as spinach, bamboo shoots, and water bamboo. Peng Jing, Director of the Nutrition Department at the School of Tourism and Cuisine at Yangzhou University, told a reporter from the Life Times that oxalic acid combines with calcium in the intestines to form calcium oxalate, which is difficult to absorb. This interferes with the body's absorption of nutrients and can also lead to kidney stones. Since oxalic acid is water-soluble, blanching can remove most of it. The second category includes cruciferous vegetables like cauliflower and broccoli, which are difficult to cook thoroughly by direct stir-frying and should be blanched first. The third category includes wild vegetables like purslane, which should be blanched in boiling water to completely remove dust and insects. Furthermore, water chestnuts should be peeled and blanched before eating to ensure they are more sanitary.
However, some vegetables are better eaten raw. Song Xin, a nutritionist from the Nutrition Department at Chaoyang Hospital, explains that vegetables like lettuce, radishes, cucumbers, and the inner core of Napa cabbage retain more of their nutrients when washed and eaten directly. It is best to choose organic or pesticide-free green vegetables for raw consumption.