In daily life, many foods are not finished in one sitting. To avoid waste, people will put leftover food in the refrigerator to eat the next day. However, there are many precautions to take when eating overnight food. So, which overnight foods should not be eaten?
Foods Not to Eat Overnight
1. Overnight Tremella (Silver Ear Mushroom) Should Not Be Eaten
Tremella soup is a high-nutrition health supplement, but after being left overnight, its nutritional value decreases and harmful substances are produced. This is because both indoor-cultivated and wood-cultivated tremella contain a high amount of nitrates. After being cooked, if left for a long time, the nitrates are reduced to nitrites by bacterial action. When a person drinks this soup, the nitrites enter the bloodstream. The red blood cells contain hemoglobin, which can carry large amounts of oxygen to meet the body's needs.
However, nitrites have the opposite effect, oxidizing the body's normal hemoglobin into methemoglobin, which loses its ability to carry oxygen, causing the body to lack normal hematopoietic function!
2. Overnight Leafy Green Vegetables Should Not Be Eaten
Because some leafy green vegetables contain a high amount of nitrates, if they are cooked and then left for too long, the nitrates will be reduced to nitrites by bacterial action. Nitrites are carcinogenic and cannot be removed by reheating. Generally, stem and leaf vegetables have the highest nitrate content, followed by root and stem vegetables and flowering vegetables like cauliflower, with gourds having the lowest content.
Therefore, if you buy different types of vegetables at the same time, you should eat the leafy greens first, such as cabbage and spinach. If you plan to cook extra food to reheat the next day, you should try to make fewer leafy greens and choose gourds instead.
3. Homemade Braised and Marinated Foods Should Not Be Eaten Overnight
Braised and marinated foods are popular seasonal dishes among Shanghai residents. Many people also like to put leftover braised and marinated foods in the refrigerator "overnight," but this practice poses significant food safety risks. To prevent food poisoning, do not eat overnight braised and marinated foods in spring and summer. Bulk braised foods should be finished on the same day and not left overnight. From a food safety perspective, this is unhygienic. If possible, it is best not to eat overnight marinated foods. Food experts remind that even food stored in the refrigerator is not absolutely "safe." The refrigerator is a breeding ground for molds and psychrophilic bacteria.
4. Seafood Should Not Be Eaten Overnight
Foods that should not be eaten overnight include fish, seafood, leafy greens, and cold salads. Fish and seafood can produce protein degradation products overnight, which can damage liver and kidney function. Leafy greens contain varying amounts of nitrates. If overcooked or left for too long, the vegetables will turn yellow and taste bad, and the nitrates will be reduced by bacteria into toxic nitrites, which are carcinogenic. Cold salads are more contaminated during processing, and even after refrigeration, they are likely to have spoiled overnight and should be eaten freshly made.
5. Overnight Soup Is Best Not to Be Drunk
Cantonese people love to simmer soups. If there's leftover soup, they put it in the refrigerator and reboil it the next day. Is this overnight soup good for your health?
Healthy way to eat: The best way to preserve soup is not to add salt or other seasonings to the base. After cooking the soup, use a clean spoon to scoop out the portion for the day. For the leftover soup, it is best to store it in a crock pot in the refrigerator. Because leaving soup in an aluminum or stainless steel pot for a long time can cause chemical reactions, it should be stored in glass or ceramic containers.
6. Overnight Tea Should Not Be Drunk
Because overnight tea has been left for too long, most of its vitamins are lost, and the proteins and sugars in the tea become nutrients for the growth of bacteria and molds. Therefore, people generally believe that overnight tea should not be drunk!
7. Overnight Undercooked Eggs Should Not Be Eaten
Can you eat overnight eggs? Northerner: Yes, don't you see tea eggs sold everywhere! Southerner: No, especially for men, because it can cause hernias and scrotal enlargement! Scientist: It depends! Because if the egg is not fully cooked, the uncooked yolk, if eaten overnight and improperly stored, can easily breed bacteria, which is harmful to health, causing problems such as indigestion and bloating.
However, if the food (egg) is fully cooked and properly sealed and stored at a low temperature (generally refrigeration temperature), it can generally be safely stored for 48 hours.
From the scientist's advice, we know: whether an overnight egg can be eaten depends not only on whether it is reheated, but also on whether the egg was fully cooked the first time it was boiled. Only after it is fully cooked the first time can it be reheated and eaten the next day without any problem. This is the same principle for tea eggs. Many people may not know that tea eggs are boiled twice: the first time to cook them through, and the second time after cracking the shells, adding tea and other ingredients to simmer again. So tea eggs are definitely cooked. Now some people like to eat half-cooked eggs (with a semi-liquid yolk). Those eggs cannot be eaten overnight, even if they are reheated the second time.
8. Overnight Boiled Water Should Be Avoided
Boiling tap water for 3-5 minutes minimizes the content of harmful substances like nitrites and chlorides, making it most suitable for drinking.
Avoid drinking overnight boiled water: Nitrites can form carcinogenic nitrosamines in the human body. Experts have found that the nitrite content in boiled water is higher than in raw water. Moreover, repeatedly boiling water for too long or water that has been boiled for more than 24 hours has a significantly increased nitrite content. After 24 hours, the nitrite content in boiled water is 1.3 times higher than when it was first boiled. Chinese people have a habit of drinking boiled water. It is best to boil and drink it fresh or only drink water from the same day. Also, do not drink water that has been boiled for too long.