1. Corruption: The black tea fungus is stored for too long, or the storage environment is too humid, which is easy to be infected by bacteria, leading to corruption and deterioration.
2. Mildew: In an excessively humid environment, black tea fungus is easily attacked by mold and feels damp. When white spots or molds are found, it means that the black tea fungus has deteriorated.
3. Bacteria turn green: If the bacteria turn green, it means that the black tea fungus has gone bad and can no longer be eaten.
It should be noted that if the black tea fungus itself does not have any peculiar smell or abnormal appearance, you don't have to worry too much about whether it will deteriorate and you can continue to use it. But if you smell a strong smell or see an abnormal color mold, you need to stop using it immediately.