''Douchi'' is made by and salting soybeans. The process turns the beans black, soft, and mostly dry. The flavor is sharp, pungent, and spicy in smell, with a taste that is salty and somewhat bitter and sweet.
''Douchi'' should not be confused with , a variety of common bean that is commonly used in the cuisines of Central America, South America, and the Caribbean.
In , ''douchi'' is also referred to by the same kanji and pronounced as ''touchi''.
The process and product are similar to ''ogiri'' and ''iru'', both being African fermented bean products.
Douchi is especially used to flavor fish or vegetables . Unlike some other fermented soybean-based foods such as natto or tempeh, ''douchi'' is used only as a seasoning, and is not meant to be consumed in large quantities, being typically much more salty.
Small packets of ''douchi'' are available wherever Chinese foods are sold.
Some common dishes made with ''douchi'' are Steamed Spare ribs with Fermented Black Beans and Chili Pepper , and Braised Mud Carp with Fermented Black Beans .
Black bean paste
In Chinese cuisine, a condiment called black bean paste or black bean garlic sauce is made from ''douchi'', as well as garlic and soy sauce, a typical combination used for seasoning a dish. This paste is commercially available in glass jars from companies such as Lee Kum Kee, although most Chinese restaurant chefs prefer to use actual ''douchi'' to prepare such sauces rather than using commercially available black bean paste.