At the heart of East Asian fermentation lies koji, the cultivated mold Aspergillus oryzae. Koji is grown on cooked grains and produces enzymes—particularly amylases and proteases—that convert starches into fermentable sugars and proteins into amino acids. This dual enzymatic action is the foundation of Japanese fermentation. Sake, often called Japanese rice wine, is brewed by inoculating steamed rice with koji; the enzymes break the rice starch into sugars, which yeast then convert into alcohol. The result is a beverage of considerable complexity built on this two-step enzymatic and microbial process. Miso is another koji-driven ferment: cooked soybeans combined with koji and salt are aged for months to years, producing a deeply savory paste used as a base for soups and glazes. Shoyu (soy sauce) follows a similar logic, fermenting soybeans and wheat with koji in a salt brine.
Asian cuisines also host a remarkable variety of legume and seed ferments beyond those derived from koji. Tempeh binds cooked soybeans together with the mold Rhizopus into a firm cake during a short 24–48 hour incubation around 88°F (31°C), after which it is sliced and cooked. Natto is fermented by Bacillus subtilis, producing small sticky soybeans with a pungent aroma prized in Japanese breakfast culture. Across the continent, fermented soybean pastes include Korean doenjang and gochujang (a chili paste that incorporates rice and soybeans) and Chinese doubanjiang, made from broad beans and chilies. Salted, fermented black beans—douchi—contribute savory depth across Chinese stir-fries and braises. Southeast Asian cuisines contribute their own thread: fish sauce, fermented fish with salt over 6–24 months, anchors Thai, Vietnamese, and Philippine cooking, where a few drops add umami without any overt fishiness. Similar ferments include Filipino bagoong and the ancient Roman garum that preceded European fish sauces by centuries.
Chili ferments tie these threads together across continents. Hot sauce begins with a chili mash held in salt brine at room temperature for 1–4 weeks, fermenting until naturally tangy, then blended and strained to taste. Air locks are especially handy in this case: a sealed jar of fermenting chilies builds carbon dioxide pressure that can erupt when opened. Tabasco represents the long-aged end of the spectrum, fermenting peppers in oak barrels for about three years to develop a vinegar-based heat. Variants of fermented chili pastes—sambal, harissa, and others—recur throughout the world's hot cuisines, each carrying the microbial fingerprint of its region.