Chunggukjang — Quick-Fermented Soybean Paste (청국장)

Korean winter cuisine tradition; records trace to the Goryeo period; the name roughly means 'Chinese quick soy paste' (청국 = old term for China), suggesting possible cross-cultural origins

Chunggukjang (청국장) is the rapid-fermented soybean paste of Korean cuisine: cooked whole soybeans fermented for 2–3 days at 40–42°C through naturally occurring Bacillus subtilis natto, producing a pungent, ammonia-scented paste with long white fermentation threads (the Bacillus biofilm) stretching through the beans. Unlike doenjang (which ferments for months to years in earthenware), chunggukjang was historically made in winter within days to provide fermented soybean nutrition quickly. It is now associated with strong-smelling, intensely flavoured jjigae (chunggukjang jjigae) that divides Korean households — those who grew up with it and treasure it, and those who find the smell unbearable.

Chunggukjang jjigae is the primary use: paste dissolved in anchovy stock, simmered briefly with tofu, kimchi, and vegetables. The smell intensifies during cooking and permeates the dining space — eating chunggukjang jjigae is a sensory commitment. Eaten with plain rice, it is considered highly nutritious.