Just because tofu is a little sour doesn't necessarily mean it can't be eaten. Tofu is a perishable food. If it is not properly preserved or expired, it will produce sour taste. If the tofu is just a little sour, you can smell it first to see if there is any peculiar smell, and then taste it to see if the taste is normal. If there is no obvious difference between the taste of tofu and that of ordinary tofu, it can be eaten.
However, if the bean curd has abnormal taste or changes in appearance (such as mildew, discoloration, etc.), it should not be eaten because it may cause food poisoning or other health problems. In order to avoid food poisoning, the preservation of tofu should be checked regularly, and it should be discarded in time when it expires or deteriorates.