“Overnight food” does not only refer to the dishes put overnight, placed more than 8-10 hours, it should be considered overnight. There are two reasons for the increase in toxic ingredients in food, the first is because the chemicals in the food produce carcinogens, such as nitrites, even if the heating can not be removed. The other reason is the secondary contamination by foreign bacteria when placed. The following types of dishes are especially harmful when left for a long time. 1, leafy greens overnight most dangerous Usually the highest nitrate content of leafy vegetables, melon vegetables are slightly lower, root vegetables and cauliflower class in the middle. Therefore, if you buy a large number of vegetables at the same time, you should first eat leafy vegetables, such as cabbage, spinach and so on. If you are ready to make more dishes to eat hot the next day, you should try to do less stem and leafy vegetables, and choose melon vegetables. 2, overnight seafood damage liver and kidney crab, fish, shrimp and other seafood, overnight will produce protein degradation, damage to liver and kidney function. If you really buy more, you can put raw seafood in a plastic bag or plastic box, put it in the freezer, and cook it next time. 3, half-cooked eggs prone to disease Many people love to eat soft yolk half-cooked eggs, but this egg sterilization is not complete, coupled with the egg is rich in nutrients, extra easy to breed bacteria, consumption can be dangerous. If the egg is cooked and properly stored in a low-temperature seal, it is not a problem to eat overnight. 4, silver fungus mushrooms to beware of whether it is wild or artificial cultivation of silver fungus, mushrooms, etc., are prone to residual nitrates. If you put the time is really a bit long, you can only bear the pain and throw away. 5, do not put the soup in metal utensils boiling soup is time-consuming and labor-intensive, people often boil a large pot, a series of days to eat. If the leftover soup for a long time in the aluminum pot, iron pot, will precipitate harmful substances. The best way to store the soup is not to put salt and other seasonings in the soup, cook the soup with a clean spoon to drink the day, drink is not finished, it is best to use the wok or fresh box stored in the refrigerator.