''Nuruk'' () is a traditional Korean fermentation starter. It is used to make various types of Korean alcoholic beverages including '' takju'', ''

cheongju Cheongju () is the capital and largest city of North Chungcheong Province in South Korea. History Cheongju has been an important provincial town since ancient times. In the Cheongju Mountains, specifically in the one where Sangdang Sanseong is ...

'', and

soju (; Hangul: ; Hanja: ) is a clear and colorless Korean distilled alcoholic beverage. It is usually consumed neat. Its alcohol content varies from about 12.9% to 53% alcohol by volume (ABV), although since 2007 low alcohol soju below 20% h ...

. It is an essential ingredient in Shindari and is mixed with rice.Nowicki, Stephen. Holt McDougal Biology. Orlando, FL: Holt McDougal, 2012. Print. Historically, it was used in a variety of provinces of

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic ...

, including Jeju Island.

Wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

(of both the glutinous and non-glutinous types), and

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...

are used to make ''nuruk,'' either as whole grain or in the form of grits or flour. 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 Ondol (; , Hangul: 온돌, 溫堗, ) or gudeul (Hangul: 구들, ) in Korean traditional architecture, is underfloor heating that uses direct heat transfer from wood smoke to heat the underside of a thick masonry floor. In modern usage it refe ...

room. The cake matures at a precise temperature until a mold forms.

Origin

''Nuruk'' has been used in Korea since the period of the

Three Kingdoms The Three Kingdoms () from 220 to 280 AD was the tripartite division of China among the dynastic states of Cao Wei, Shu Han, and Eastern Wu. The Three Kingdoms period was preceded by the Eastern Han dynasty and was followed by the West ...

in the 3rd century CE, while similar fermentation starter, '' jiuqu'', was first made in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

during the

Warring States period The Warring States period () was an era in History of China#Ancient China, ancient Chinese history characterized by warfare, as well as bureaucratic and military reforms and consolidation. It followed the Spring and Autumn period and concluded ...

beginning in the 5th century BCE. Chinese history records the first use of ''nuruk'' in Korea in 1123 CE. Traditionally, ''nuruk'' was prepared on a small scale by families in summer or autumn, especially in July when the ambient temperature is between on the Korean peninsula. It has been mass-produced in factories since the 1920s.

Characteristics

Microorganisms present in ''nuruk'' include ''

Aspergillus oryzae ''Aspergillus oryzae'', also known as , is a filamentous fungus (a mold) used in East Asia to saccharify rice, sweet potato, and barley in the making of alcoholic beverages such as '' sake'' and ''shōchū'', and also to ferment soybeans f ...

'', ''Rhizopus'' ''oryzae'', lactic acid bacteria such as ''

Lactobacilli The ''Lactobacillaceae'' are a family of lactic acid bacteria. It is the only family in the lactic acid bacteria which includes homofermentative and heterofermentative organisms; in the ''Lactobacillaceae,'' the pathway used for hexose fermentati ...

'', and yeasts, predominantly '' Pichia anomala'' and ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...

''.Baldwin, Becca; Lenaghan, Daniel (2014).
Begin with Rice and Water: A Primer on Brewing Makgeolli
" Iseo-myeon, Jeollabuk-do, South Korea: National Academy of Agricultural Science, Rural Development Administration. . Retrieved 04 February 2019. ''Aspergillus'' provides the enzyme

amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...

, which saccharifies the rice's starches. The resulting sugars are consumed by the yeasts, producing alcohol, as well as the ''Lactobacilli'', producing lactic acid. ''Rhizopus'' provides the enzyme

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...

and

lipase Lipase ( ) is a family of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually ...

, which break down the protein and fat in the outer layers of the rice grain (endosperm), allowing the amylase access to the starches in the inner part. The proportions of microorganisms can vary depending on the region where the nuruk was made. Nuruk made in the southern coastal areas surrounding

Busan Busan (), officially known as is South Korea's most populous city after Seoul, with a population of over 3.4 million inhabitants. Formerly romanized as Pusan, it is the economic, cultural and educational center of southeastern South Korea ...

, for example, have a higher lactic acid bacteria content due to the warmer climate and humidity. Chemically, it contains 2,6-Dimethoxybenzoquinone (2,6-DMBQ), also found in fermented wheat germ extract.

References

{{Reflist Fermentation in food processing Korean cuisine