Nuruk is the traditional Korean fermentation starter used to make rice-based foods and drinks, including products associated with harvest festivals.
Nuruk is made from grains, traditionally wheat, rice, or barley, that are shaped and allowed to develop a community of molds, yeasts, and bacteria. These microorganisms help break down starches into sugars and support alcoholic fermentation. Producers then use the starter in beverages such as makgeolli and cheongju, as well as in some fermented foods.
The quality and character of nuruk influence aroma, acidity, sweetness, and alcohol development. Traditional production methods vary by region and household, so nuruk is not a single standardized commercial ingredient.
Nuruk is often confused with meju, the fermented soybean block used for Korean pastes and sauces. Gochujang and doenjang are finished foods, not fermentation starters of the same kind. Chuseok meals may feature foods made from newly harvested grains, but nuruk itself is the technical ingredient that enables many Korean grain-fermentation processes.