Freshwater fish such as carp, crucian carp and silver carp often smell earthy. This is because the living environment of freshwater fish, such as fish ponds and lakes, is rich in humus, which is very suitable for the growth of microorganisms. Studies have shown that some cyanobacteria and chlorophyta organisms can produce substances with earthy smell. Now some people think that some species of diatom and actinomycetes can also produce earthy smell. Earthy smell enters the blood through fish gills, so it has earthy smell. Modern research shows that the earthy smell is mainly caused by MIB(2 and Geosmin.

The traditional method of removing the fishy smell from freshwater fish is to remove scales and gills, cut open the belly and wash it, then soak it in cold water, and pour in a small amount of vinegar and pepper. Because cold water replaces the blood in the fish and adds seasonings such as ginger, onion and garlic to remove the fishy smell, the fishy smell can be removed. In recent years, the research on deodorization methods in processing industry at home and abroad mainly includes salt solution soaking, tea solution soaking, deodorization agent method and ozone method.