Not wasting food is a virtue, and many people are used to saving leftover dinner for the next day. However, some foods, if consumed overnight, may pose health hazards.
Overnight Tremella
Tremella soup is a high-nutrition tonic, 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. When cooked and left for a long time, bacteria will break down the nitrates into nitrites.
Nitrites oxidize the normal hemoglobin in the human body into methemoglobin, causing it to lose its ability to carry oxygen and resulting in a deficiency in normal blood production.
Overnight Tea
Due to the long duration, most vitamins in overnight tea are lost, and the proteins and sugars in the tea become a breeding ground for bacteria and mold. Therefore, it is generally believed that overnight tea should not be consumed.
Overnight Eggs
If an egg is not fully cooked, consuming the uncooked yolk overnight, especially if stored improperly, can easily breed bacteria, leading to issues such as gastrointestinal discomfort and bloating. However, if the egg is fully cooked and properly sealed and stored at a low temperature, it is generally fine.
Tea eggs are typically boiled twice: the first time to cook them through, and the second time after cracking the shells with other ingredients like tea, so they are definitely cooked. However, those half-cooked eggs with a semi-liquid yolk should not be eaten overnight.
Overnight Leafy Green Vegetables
Due to their high nitrate content, some leafy green vegetables can have their nitrates converted into nitrites by bacterial decomposition if left for too long after cooking. Nitrites are carcinogenic and cannot be removed by reheating. Therefore, if you want to prepare extra food to reheat the next day, you should try to minimize leafy stem and vegetables and choose gourds instead.
In addition, all seafood and fish are not suitable for overnight consumption. Protein degradation products can easily form in fish and seafood overnight, which can damage liver and kidney function.