Douchi (Chinese fermented black beans)

Douchi (豆豉) — also commonly transliterated as 'fermented black beans' in English Chinese-cooking literature — is one of the oldest documented Chinese soybean ferments, with written references dating to the Han dynasty (200 BCE - 220 CE). The substrate is black soybeans (or sometimes yellow soybeans, dried dark by the fermentation rather than naturally black), inoculated with Aspergillus oryzae or wild mixed cultures, salt-cured, and dried to a chewy-firm finish.

The technical distinction from miso and doenjang is critical: douchi is whole-bean — the soybeans remain individually identifiable, not pasted. The texture is firm and chewy rather than pasty. The fermentation typically uses lower moisture and higher salt than miso, producing a more concentrated, drier final product. Douchi is added whole or coarsely chopped to dishes; it is not used as a base paste the way miso or doenjang is.

Regional variations are substantial. Yangjiang douchi from Guangdong is mild, fragrant, and used in Cantonese dim sum (the foundation of black-bean spareribs and clams in black bean sauce). Liuyang and Pixian douchi from Sichuan and Hunan are saltier, more intensely fermented, and often combined with chili paste for the famous dou-ban-jiang (see separate entry). Some Chinese douchi traditions use wild Aspergillus surface fermentation similar to Korean meju; others use directly inoculated Aspergillus oryzae closer to Japanese koji.

The culinary applications are concentrated in Cantonese, Sichuan, and Hunanese cooking: black-bean garlic sauce, douchi with steamed fish, mapo tofu base, huiguorou (twice-cooked pork). A small handful of douchi (10-20 beans, maybe 15-20 g) provides the umami backbone for a dish serving 4-6 people. Douchi is to Chinese cooking what soy sauce is to Japanese — but in solid form, more concentrated, more textural.