What is Nuruk?
Nuruk is a fermentation agent used in making Korean alcoholic beverages. It's made by cultivating mold on grains such as wheat, rice, barley, mung beans, or soybeans. The purpose of nuruk is to obtain the enzymes needed for brewing and the yeast that produces alcohol. In other words, nuruk is used for starch saccharification by saccharifying enzymes and for alcohol production by yeast.
In Korea, wheat is used as the primary ingredient for nuruk in almost all cases. This is because the saccharifying enzymes and lactic acid bacteria in wheat help ensure safe fermentation when making alcohol. Additionally, the wild yeasts naturally present in wheat greatly assist with alcohol fermentation when using traditional nuruk, which is why wheat has been the grain of choice in Korea.
Types of Nuruk
Nuruk can be divided into two types: "ddeok-nuruk" (cake nuruk) and "heurim-nuruk" (scattered nuruk). Ddeok-nuruk is made by grinding the ingredients, mixing them with water, and forming them into solid chunks of a specific size. Heurim-nuruk, on the other hand, is made by spreading out the grains without clumping them together and cultivating mold on each individual grain particle. This is easier to understand if you think of Japanese koji.
Korea has used both methods throughout history, but primarily relies on the cake form of nuruk. Some people claim that scattered nuruk has less saccharification power and contains fewer yeasts, which is why the cake form is preferred. However, since the flavor and taste of alcohol vary depending not only on the nuruk used but also on the fermentation environment created, we cannot conclusively say that scattered nuruk has inferior saccharification power or fewer yeasts.
The important thing to remember is that whether it's nuruk or koji, it's an essential ingredient for making good alcohol.
Difference between Nuruk and Koji
The difference between nuruk and koji is simple. Most yeasts that adhere to nuruk are wild yeasts. While commercial breweries typically use specifically cultivated yeasts for consistent quality control, traditional brewing methods using nuruk primarily rely on wild yeasts found in the air, on plants, or on grains.
Due to this characteristic of nuruk, alcoholic beverages made using traditionally produced nuruk develop rich flavors and aromas. However, the disadvantage is that it's difficult to maintain consistent quality in the final product because of the variety of microorganisms involved.
In contrast, Japan has addressed this disadvantage by creating koji, which involves sprinkling Aspergillus oryzae (yellow mold) on steamed rice and cultivating it under controlled conditions to produce a fermentation starter of consistent quality.
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Regional Variations and Climate Impact on Nuruk
The local climate plays an extremely important role in nuruk production. Japan developed the scattered nuruk (koji) method partly because of its relatively humid climate. If too much moisture remains during the fermentation of nuruk, it can rot.
In Korea, the shape of nuruk varies by region. In mountainous areas like Gangwon and Gyeongsang provinces, nuruk tends to be wide and thin. In the Jeolla region, nuruk is smaller in size but thicker, while on Jeju Island, nuruk is small like a palm and thin. This demonstrates how local climate, humidity, and sunlight significantly influence nuruk production.
Therefore, if you want to make nuruk, you should experiment with different methods based on your environment, climate, and available space to create the most suitable nuruk for your specific conditions.
