Oyster sauce is made by concentrating cooked oyster soup. It is dark brown and has a special taste. It is used as a condiment, and many famous dishes in Guangdong cannot do without it. It is one of the famous specialties in Guangdong. There are two kinds of oyster sauce products: light oyster sauce and salty oyster sauce. The former is oyster soup obtained by cooking oysters, and the latter is salty soup obtained by adding salt to cooked oysters.

The method of cooking oysters by mud pot concentration is as follows: after filtering the impurities, pour the oyster soup into a large iron pot and boil it to make the water evaporate continuously. After the liquid level drops, new soup will be added to continue evaporation. This process is commonly known as "pumping soup". As the concentration goes on, the oyster soup in the pot becomes thicker and darker. When oyster sauce is processed recently, the color is dark brown, the liquid viscosity increases, and the specific gravity of the finished product is generally 28 ~ 30. At this time, oyster sauce is ready.

At present, there is an improved atmospheric vacuum concentrator, which has been successfully used to extract oyster sauce, thus realizing the semi-mechanized production of the main processes of oyster product production.