Nitrite surged after frying vegetables for 6 hours.
When it comes to overnight dishes, most people will think of nitrite and turn pale. In this experiment, the experimenter prepared three different types of dishes: stir-fried, tomato and egg, braised pork, and tested the changes of nitrite content after different dishes were placed for different time.
The experimenter divided the three dishes into four parts, then covered them with plastic wrap and put them in the refrigerator at 5℃- 10℃. The changes of nitrite content in dishes were determined in four time periods: half an hour, 6 hours, 18 hours and 24 hours.
The results showed that the nitrite content of fried vegetables increased from less than 1mg/kg at the beginning to about 5mg/kg, and rose rapidly after 6 hours to 2mg/kg. The content of nitrite in tomato and egg soup increased from about 2mg/kg to about 5mg/kg, and began to increase rapidly after about 18 hours. The nitrite content of braised pork quadrupled from about 2mg/kg to about 8mg/kg, and it also increased rapidly after 18 hours.
Experts dispel doubts
Three factors determine the nitrite content of dishes.
Where does the nitrite in food come from? Professor Zhu Yunlong, vice president of Jiangsu Cuisine Research Institute and master tutor of Yangzhou University, introduced that nitrogen is a widely existing element in nature. Plants absorb nitrogen from the environment and finally synthesize amino acids through complex biochemical reactions. Nitrate is an inevitable step in this process. There are some reductases in plants, which can reduce some nitrate to nitrite. Therefore, all plants contain nitrate and nitrite.
He introduced that the current scientific research results generally believe that nitrate itself is non-toxic. However, if nitrite enters the human body in large quantities, it may lead to "methemoglobinemia", and the blood will lose its oxygen-carrying ability, resulting in symptoms of hypoxia, which may be life-threatening. A broader concern about nitrite is that it may be converted into nitrosamines in the human body, which is a carcinogen.