Wheat, rice (of both the glutinous and non-glutinous types), and barley are used to make nuruk, either as whole grain or in the form of grits or flour.[2][7] Wheat nuruk is the most common variety. The dry grain is moistened, shaped into a large cake, and hung up to ferment for 2‒4 weeks in an ondol room.[2][3][7] The cake matures at a precise temperature until a mold forms.[3]
^"Fermented Cereals a Global Perspective. Chapter 3." Fermented Cereals a Global Perspective. Chapter 3. Web. 04 Mar. 2016.
^ abYokotsuka, T. (1985). "Fermented protein foods in the Orient, with emphasis on shoyu and miso in Japan". In Wood, Brian J. B. (ed.). Microbiology of Fermented Foods. Vol. 1. London: Elsevier Applied Science Publishers. pp. 197–247. ISBN978-1-4613-7990-4.