It can be made in two to three days through fermentation of boiled soybeans, adding Bacillus subtilis, which is usually contained in the air or in the rice straw, at about 40°C without adding salt, compared with the much longer fermentation period required for doenjang, another, less pungent variety of Korean soybean paste.
[citation needed] Cheonggukjang may also be made by fermenting boiled soybeans in a warm place, pounding a portion of them, and adding salt and red chili powder.
One theory proposed by Chinese scholars is that cheonggukjang was introduced by what is now China to the Korean peninsula during the Joseon era.
[citation needed] However, Samkukjiwijidongijeon (Records of the Three Kingdoms, 三國志魏志東夷傳) suggests that cheonggukjang has existed in the Korean peninsula since before the Joseon era, as there are records of such fermented foods dating back to first century BC, throughout the Koryo dynasty and the Kingdom of Silla.
[2] Cheonggukjang is generally considered to be a healthy food (particularly in the winter), as it is rich in vitamins and other nutrients, though its very strong odor is not universally enjoyed.