<P> Fermented black soybeans are the oldest - known food made from soybeans . In 165 BC, they were placed, clearly marked, in Han Tomb No. 1 at Mawangdui Tomb Site in South Central China . The tomb was sealed about 165 BC and was first opened in 1972 . The high - ranking woman to whom the undisturbed tomb belonged was probably the wife of the first Marquis of Tai . </P> <P> In 90 BC, in the Records of the Grand Historian by Sima Qian, Chapter 69, refers to 1,000 earthenware vessels of mold - fermented cereal grains and salty fermented soybeans (shi). They were now an important commodity in China . When the prince of Huainan (legendary inventor of tofu) was exiled for inciting rebellion (in 173 BC) against his brother, the Han Emperor Wendi, his retinue and he were, nevertheless, provided with such necessities of life as firewood, rice, salt, shi (fermented black soybeans), and cooking utensils . This date, 173 BC, is before Han Tomb No. 1 at Mawangdui was sealed . </P> <P> It is used as an ingredient for mapo tofu . Douchi is also used to flavor fish or stir - fried vegetables (particularly bitter melon and leaf 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 saltier . </P> <P> Small packets of douchi are available wherever Chinese foods are sold . </P>

What are the black things in hunan chicken