Besides nitroso compounds, fermented food also involves mold pollution. Among them, as many as five kinds of mold strains were detected in dried vegetables and douchi. Except for moldy tofu, if it is eaten for a long time, it has certain potential harm to human body; The nutritional value of pickles and bean curd is low and too salty; In order to preserve some processed foods such as pickles and bean curd, preservatives may be added, which is harmful to health.