Cheonggukjang (청국장) is Korea’s fast soybean ferment: cooked soybeans kept warm for two to three days until they’re coated in sticky threads and smell strongly, then roughly mashed – often with a little salt, garlic and chili – into a paste. It’s best known in cheonggukjang-jjigae, a pungent, hearty stew. Unlike doenjang, which is brined and aged for months, cheonggukjang is ready in days and can be made without salt (Kim et al., 2021).
What Ferments It
Like Japanese natto, cheonggukjang is fermented by Bacillus bacteria – mainly B. subtilis or B. licheniformis – with lactic acid bacteria and Enterococcus faecium also involved (Kim et al., 2021). Traditionally the cooked beans were wrapped in rice straw, which carries Bacillus, and kept somewhere warm.
A shotgun-metagenomics study of naturally fermented cheonggukjang found Bacillus dominating – about 150 species, with B. thermoamylovorans the most abundant, then B. licheniformis, B. glycinifermentans and B. subtilis – but also genera such as Cronobacter and Enterobacter (Tamang et al., 2022). That’s the case for using a pure Bacillus subtilis (natto) starter at home rather than wild straw, holding the beans hot so the starter dominates, and cooking the result, as Korean cooks usually do.
Cheonggukjang and Health
A review of cheonggukjang research lists many possible effects – on blood pressure, cholesterol, blood clotting, inflammation and more – but these come largely from lab and animal studies, not trials in people (Kim et al., 2021). The most practical advantage is that, unlike doenjang and gochujang, it can be made with little or no salt. Like natto, Bacillus-fermented soybeans can be rich in vitamin K2, which counteracts the blood thinner warfarin – natto measurably raises blood vitamin K2 for days (Homma et al., 2006) – so check with your doctor if you take warfarin.
Compare Korean, Japanese and other soy ferments in our fermented soybean guide; West Africa’s dawadawa is another Bacillus-fermented bean seasoning.