Recently, the claim that "overnight food causes cancer" has been all the rage. So, is there any truth to this statement?
"Overnight food" doesn't just refer to dishes left for a whole night. If food has been left out for more than 8-10 hours, it should be considered as such. There are two reasons for the increase in harmful components in food. The first is that chemicals in the food produce carcinogens, such as nitrites, which cannot be removed even by reheating. The other reason is secondary contamination from external bacteria during storage.
The following types of dishes are particularly harmful when left for a long time
Green leafy vegetables are the most dangerous when left overnight. Generally, stem and leafy vegetables have the highest nitrate content, followed by gourd vegetables, with root and stem vegetables and cauliflower types in the middle. Therefore, if you buy a large quantity of vegetables, you should eat the leafy ones first, such as Chinese cabbage and spinach. If you plan to cook extra to reheat the next day, try to make less of the stem and leafy vegetables and choose gourd vegetables instead.
Overnight seafood can damage the liver and kidneys. Seafood like crabs, fish, and shrimp produce protein degradation products after being left overnight, which can impair liver and kidney function. If you've bought too much, you can store the raw seafood in sealed bags or containers in the freezer and cook it later.
Undercooked eggs can easily cause illness. Many people love soft, runny yolks in their eggs, but these eggs are not thoroughly sterilized. Coupled with the fact that eggs are rich in nutrients, they are particularly prone to bacterial growth, which can be dangerous to eat. If the egg is fully cooked and stored properly at a low temperature, it is fine to eat the next day.
Be careful with silver ear and mushrooms. Whether wild or cultivated, fungi like silver ear and mushrooms can easily retain a lot of nitrates. If they have been stored for too long, you have to throw them away.
Don't store soup in metal containers. Making soup is time-consuming and laborious, so people often make a large pot to eat for several days. If leftover soup is kept in an aluminum or iron pot for a long time, harmful substances can leach out. The best way to store soup is to not add salt or other seasonings while cooking. After cooking, scoop out the portion for the day with a clean spoon. For the rest, it's best to store it in a clay pot or a sealed container in the refrigerator.
How to handle overnight food without wasting it
1. It's best to store leftover food in glass containers
Overnight food is not some kind of monster. As long as it hasn't been stored for too long and isn't consumed too frequently, there's no need to be afraid of it. The nitrates and nitrites in food pose a minimal risk to human health.
Of course, to minimize the impact of harmful substances on the body, it is best to store leftover cooked food in the refrigerator in sealed glass or ceramic containers, sorted by type. When eating refrigerated food again, it must be thoroughly reheated at high temperatures. Fresh raw meat is best eaten as soon as it's bought. If it can't be used all at once, it's best to freeze it in the refrigerator, which is the best way to preserve it.
It should be noted that the leftover dishes mentioned above do not include cooked freshwater fish, seafood, or cold salads. Cooked freshwater fish and seafood, when stored for a long time, can easily produce protein degradation products that can damage liver and kidney function and even produce toxins. Cold salads are also easily contaminated and can spoil quickly even when refrigerated.
2. Portion in advance
If you know you won't finish a meal in one sitting, you should portion it into different plates as soon as it's cooked. Once a portion has cooled down a bit, put it in the refrigerator. This way, the "base number" of bacteria in the food is very low, and it will be fine to eat it the next day or even the third day after reheating it thoroughly. If the food has been out for two or three hours and has been stirred around with chopsticks, its shelf life will be shortened. In this case, spread it out a bit and place it in the back of the bottom shelf of the refrigerator to cool down to the refrigerator's temperature as quickly as possible.
3. Thoroughly reheat
It's okay to eat leftovers for the next meal, but they must be thoroughly reheated. Thorough reheating means heating the entire dish to 100°C and keeping it at a boil for more than 3 minutes. Using a microwave to reheat leftovers is a good method as it allows the inside of the food to be heated thoroughly.
However, at home, it's often difficult to control the microwave heating time, and food can easily splatter inside the microwave. You can consider heating the food in the microwave for one or two minutes first to raise its internal temperature, and then finish heating it in a pot or steamer, which makes it easier to heat through. For leftovers where you don't want too much soup, you can use steaming or pan-frying with a little water to reheat them.