Jeju Island Fermented Green Soybean Jang

The island of Jeju is located 130 km off the southern coast of South Korea. It is a popular tourist destination, in particular for Mount Halla, its famous dormant volcano. In the past, it was an island of farmers and fishers, however, little by little, tourism has taken over. The main agricultural activity that has survived is the cultivation of mandarins, which has now become a kind of monoculture.
Although the volcanic soil of the island is not suitable for the cultivation of rice, it is perfect for soybeans, particularly a variety that has always been cultivated in the southern part of Jeju, the green soybean called pureun kong (which literally translates to “blue bean”), also known as dok pureun saegi kong (meaning “egg-shaped seed”) or more generally kong jang (the term jang indicates all kinds of soy products and derivatives). It is this local variety, which has a smaller seed than the others, together with a particular yeast (known as nuruk), which makes the fermented soybean paste of Jeju and gives it a unique flavor, bittersweet and intense.
Jeju is an essential condiment across South Korea, used to flavor vegetables, meat, fish and soups. It is an important source both of flavor to dishes and nutritional characteristics.
The production technique is long and complex. First the soybeans are placed in cold water (below 15°C) for 18 hours. They are then cooked for three hours and crushed with a sort of blender (previously they were crushed in a mortar or with the feet). They are then dried for ten days and placed in large earthenware jars, immersed in salt water. At this point, the jars are closed and left to ferment for 45 days. After this period, the solid and liquid parts are divided: the first part is the soy sauce; the second is the raw material for the dough. To make the Presidium paste, the solid part is mixed with nuruk (a fermented grain made from barley or wheat), then water and salt are added to stimulate fermentation. In winter, the fermentation lasts 12 hours; in summer it takes one to two hours. Once fermented, the mix is one again placed in jars. It is ready after two to three months; however the flavor improves significantly with time (it can be matured for up to two years). The fermented dough can be made with soy, but there are other recipes that combine the soy, wheat, rice, barley or even rice and chili.