The Korean fermented soybean block used as a key ingredient in gochujang is called meju. Meju is made from cooked soybeans that are pounded, shaped into bricks or blocks, and fermented before being dried and used in Korean seasoning traditions.
For gochujang, meju is generally ground into meju-garu, or fermented soybean powder. It contributes savory depth, aroma, and the proteins and microorganisms that support fermentation. Traditional gochujang also combines the soybean component with red-pepper powder, glutinous rice or another grain, malt, and salt, producing Korea’s characteristic sweet, spicy, and savory red paste.
Meju is also the foundation of other Korean fermented sauces. Ganjang and doenjang are traditionally produced from related meju preparations, but they are not interchangeable answers here: ganjang is soy sauce, while doenjang is fermented soybean paste. Cheonggukjang is a separate fermented soybean food, usually known for its strong aroma and sticky texture.